Final SWMP Plan 08-30-2006
EXECUTIVE SUMMARY
The City of Chanhassen (City) has a surface area of roughly 15,400 acres, of which almost 3,975
acres, or more than 26 percent, is surface water features. These surface water resources include
12 lakes, approximately 400 wetlands, over 170 storm water ponds, and portions of four creeks
that are located wholly or partially within the City. One of the most prominent water features is
Bluff Creek, which runs nearly the entire length of the City and has numerous wooded bluffs and
vegetative buffer areas along the creek. Chanhassen also has a number of widely used public
open spaces located throughout the community, including the Minnesota Landscape Arboretum,
Lake Minnewashta Regional Park, and Lake Ann Park.
This wealth of water resources is clearly worth protecting, and is a primary goal of this Plan.
Investing in improvement efforts for some of the resources that are currently impaired by one or
more pollutants is also needed. The City has completed this second generation Surface Water
Management Plan (SWMP or Plan) to protect and enhance these treasured resources and
establish a more effective and up-to-date guide for future surface water management activities.
This Plan builds on the projects and activities called for in the City’s 1994 SWMP and addresses
several relatively new issues related to storm water management that the City is faced with
addressing in the coming years.
This executive summary provides a brief description of the purpose and basis for this updated
Plan, followed by a presentation of the goals that were used to guide development of this Plan.
This executive summary also highlights some of the key issues the City intends to address as part
of the ongoing implementation efforts of its overall surface water management program.
Purpose of the Plan
The purpose of this Plan is to establish the framework of a comprehensive program that does
more than simply protect and improve the quality of existing water resources within the City.
The Plan also recognizes that development must and will continue well into the future, and will
serve as a guide for City staff to follow as they evaluate the potential impacts of a given project
on these quality resources. The Plan will serve as a toolbox for the City that includes the best
available water resource data at the time it was completed, up-to-date policies and design
standards, and a process to adjust goals and policies as new data is collected and evaluated or as
complimentary programs change.
Basis for the Plan
Minnesota Rule, Chapter 8410 comprises the State’s Metropolitan Surface Water Management
Program (MSWMP) that establishes the regulatory need to update the City’s 1994 Surface Water
Management Plan (Bonestroo Rosene Anderlik and Associates). These Statutes and Rules
require the preparation of watershed plans by watershed management organizations (WMOs) and
the preparation of local water management plans that are consistent with the respective WMO
plans. This program requires that a local (i.e., City) Plan be approved by the WMOs that operate
within the City. Chanhassen is located within four major watershed units, as shown in Figure 2A.
These watersheds are the Minnehaha Creek Watershed District (MCWD), the Riley Purgatory
Bluff Creek Watershed District (RPBCWD), the Lower Minnesota River Watershed District
(LMRWD), and the Carver County Water Management Organization (CCWMO).
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The intent of the MSWMP is that through establishing realistic goals and policies at the local
level, and completing prioritized implementation activities, local goals for proper water resource
management can be realized and water quality can be protected. Through proper planning and
implementation, informed decisions can be made which allow for the protection and/or
enhancement of water resources and reduction of local flooding.
A second regulatory program, very much related to the goals, policies and standards of this Plan,
is the National Pollutant Discharge Elimination System (NPDES) Phase II Storm Water Permit
Program. This program is administered in the State by the Minnesota Pollution Control Agency
(MPCA). This program has many similarities to the MSWMP, and both programs were
considered with the Plan update. The NPDES Phase II Storm Water Permit Program is a federal
regulatory program that requires owners of Municipally Separate Storm Sewer Systems (MS4s)
to prepare and implement a Storm Water Pollution Prevention Program (SWPPP) and apply for
the permit with the administrative agency. The City submitted its initial permit application and
SWPPP in March 2003 and has been operating under the program since that time. This Plan does
not specifically incorporate the best management practices (BMPs) identified in the City’s
SWPPP. Instead, the Plan builds on these existing activities by specifying projects and
management approaches to achieve the City’s water resources goals.
Plan Overview
One of the first steps taken to develop this Plan was to gather and compile the best available
information and data from a number of resources. Sources of these data include the City’s 1994
Surface Water Management Plan, the WMO plans, MPCA NPDES Program and other relevant
sources. This data and information were then reviewed and evaluated as part of the updated
process. An introductory section establishes the purpose and basis for the Plan and provides a
general Plan overview. The subsequent sections provide a brief background and history and
describe the existing physical environment (Section II); identify goals and policies (Section III);
present specific information regarding key water bodies within the City (Section IV); present
specific information regarding wetlands management within the City (Section V), and establish
an implementation plan to guide future projects and management activities for the protection and
future enhancement of the City’s water and wetland resources (Section VI).
Using the seven goals summarized in Table ES-1, the Plan is intended to guide surface water
resource management activities through about the year 2020. Though long-term in focus, the
Plan has numerous future decision points relating to recommended capital improvements and
ongoing inspection, maintenance and monitoring activities. Where applicable, staff and financial
resources of the City, WMOs, and adjacent communities are called on to maximize the
effectiveness of the results. The Plan was developed recognizing the need to prioritize
management actions and decisions based on the management class and current water quality
status or trend for each key water resource.
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Table ES-1. Chanhassen Surface Water Management Plan Goals
Goal
Goal Goal Statement
Number
Water Quantity Provide 100-year (1% chance) flood protection for all structures.
1
Water Quality Achieve water quality standards in lakes, streams, and wetlands consistent
2
with their designated uses and established classifications.
Wetlands Protect and rehabilitate wetlands to maintain or improve their function and
3
value.
Erosion and Minimize soil erosion and sedimentation.
4
Sediment Control
Financing Establish and maintain funding sources to finance activities of this Plan.
5
Regulatory Maintain primary responsibility for managing water resources at the local
6
level but continue coordination and cooperation with other agencies and
Responsibility
organizations.
Public Education and Provide information and educational resources to improve knowledge and
7
Information promote an active public role in management of water resources.
One of the larger tasks undertaken was to update the City-wide hydrologic model. The 1994
HydroCAD Model was updated from the previous DOS-based version to Version 7.0, which is a
more rigorous and versatile program that will provide City staff a better tool for evaluating
proposed projects. One of the goals of this modeling effort was to improve the City’s ability to
predict and understand the urban hydrology within the City such that potential future flooding
issues resulting from development or redevelopment can be evaluated and avoided or reduced.
A City-wide wetland inventory was completed using the MnRAM 3.0 method as the basis for an
updated wetland classification system. Of the 356 wetlands within the city, 315 were field
reviewed and evaluated using the MnRAM assessment. The 41 basins that were not field
reviewed were mapped using high resolution aerial photographs, but were on private property,
and were not accessible for the required field assessment. Those basins that were accessible were
mapped, visited in the field and assessed to determine their condition and relative value, and
assigned to a classification category. Boundaries for each basin were mapped using GPS units in
the field, followed by a review and refinement of the boundaries in the office for many of the
basins based on the available aerial photography. The overall result of this significant effort is
establishment of the tools to more efficiently manage wetlands within the City and
recommendations for revised ordinance language to support protection and improvement of these
valued resources.
This updated SWMP addresses each of the required elements in Minnesota Statutes and Rules
and is consistent with the Metropolitan Council’s guidelines for Water Management Plans. The
Plan is also consistent with the CCWMO, LMRWD, MCWD and RPBCWD Plans. As a
minimum, the criteria set forth in this Plan establish the degree of performance necessary to
maintain the existing high-quality resources and to achieve improvement in water quality and
water quantity management where needed. These criteria are not intended to dictate or preempt
the design process, but rather provide guidelines to proper development and redevelopment.
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Water Bodies
The current condition of the majority of Chanhassen’s water bodies is good, with trends
generally showing improvements in water quality. There are a few exceptions, and the need to
improve these waters and protect the quality of all City waters is the primary basis of this Plan.
Each water body has been assigned a management classification based on the use, function and
current water quality characteristics. This management classification system shown in Table ES-
2 is intended to help City staff manage the overall surface water program.
Table ES-2. Water Management Classification System
Management Management Storm Water Water Use
Class Strategy Treatment Resource Designation
(3)(1)
Seminary Fen Calcareous Fen
NURP
Preserve and
Preserve
impose
improve,
Plus Enhanced
Assumption Trout Stream
highest standards
.
Treatment
Creek
Lotus LakeRecreational
Goal to improve
Improve - 1
Development
NURP
impose
trends,
Lake Riley Recreational
higher standards.
Plus Enhanced
Development
These waters are
Treatment
“impaired” see Table
Bluff Creek Natural Stream
21 for details
. (2)
Riley Creek Natural Stream
Lake Ann Recreational
Improve - 2 NURP
Development
Goal to maintain or
Enhanced
Christmas Lake Recreational
improve. Look for
Treatment if
Development
opportunities to
Opportunities
Lake Recreational
apply higher
Present
Minnewashta Development
standards
.
Lake Susan Recreational
Development
Harrison Lake Natural
Improve - 3
Environment
Lake Lucy Recreational
NURP
Development
Goal to maintain
water quality and
Rice Marsh Lake Natural
keep long-term trends
Environment
stable to improving
Silver Lake Natural
Environment
Lake St. Joe Natural
Environment
Storm Water Treatment
NA NA
Constructed
Ponds System
(1)Use designation taken from the City’s Comprehensive Plan.
(2)TMDL list of impaired waters for nutrients (Riley and Lotus Lakes), Turbidity (Bluff and Riley Creeks), Fish IBI (Bluff Creek).
(3)Standards provided in Appendix D. NURP level is removal of 90% TSS, 60% TP. Enhanced treatment for one or more of the
following: higher level of TSS/TP removal, additional discharge rate controls and/or temperature controls.
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This approach includes establishing treatment requirements for future development projects and
looking for opportunities to retrofit the City’s existing storm water treatment system. In addition
to the major lakes, special features within Chanhassen, such as the Seminary Fen, Assumption,
Bluff and Riley Creeks, are classified. One of the key considerations related to several of the
City’s waters, as noted in Table ES-2, is the listing on the 2004 Final Total Maximum Daily
Load (TMDL) List of Impaired Waters. The City understands that the TMDL List (as required
under Section 303(d) of the Clean Water Act) is revised every two years by USEPA, and that
additional waters may be listed in the future.
To date, approximately 8 percent of Minnesota’s river miles and 14 percent of Minnesota’s lakes
have been tested for pollution problems. Approximately 40 percent of those tested are polluted
with human and animal waste, algae from phosphorus, fertilizers and mercury. As more of the
States’ surface waters are tested for pollution problems, it is reasonable to assume that the State
will continue to add surface waters to the list of impaired waters. As such it is possible (in reality
likely), that additional surface waters within the City of Chanhassen will be added to this list in
the future.
When studies are completed for an impaired water body, the TMDL work plan will be used by
the MPCA and local entities to further prioritize management actions and establish additional
regulatory controls. The City will consider the current and any future listings in management
decisions and actively manage the activities in the contributing watersheds to limit delivery of
these pollutants to these waters. The City’s approach to addressing potential pollutant loadings to
these waters will be to evaluate the opportunities for a level of storm water “treatment” higher
than the basic standards established in this Plan on a case-by-case basis, prior to completion of
the TMDL study and associated implementation plan.
Implementation Plan
The Implementation Plan is intended to provide guidance in carrying out the Plan goals and
objectives. The implementation section summarizes capital improvement projects, studies and
ongoing maintenance, inspection, monitoring and other management activities. This Plan is
intended to serve the City for at least the next ten years and out to the year 2020. In order to
focus the implementation efforts towards achieving the stated goals, each of the individual goal
sections of this Plan include an implementation plan summary. A similar summary is provided in
the Water Bodies section of this Plan. These implementation activities and projects are combined
in a summary table in the implementation section of the Plan, along with planning-level cost
estimates.
While the City has an extensive list of projects to implement and activities to conduct on an
ongoing basis, there are several efforts that are considered the highest priority to complete. Table
ES-3 below lists these priority projects and activities in the order they appear in this Plan,
without assigning a direct priority ranking to each one. Planning level costs and a more complete
description for each project are provided in within the plan.
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Table ES-3. Implementation Program Priority Projects and Activities
Plan Section
Project Name Description Year
ID
Reference
Evaluate High Water Levels on Review previous efforts and evaluate Table 7 - 5 2007
1
Lotus Lake opportunities to reduce risks.
2 Update Storm Water Ordinance Update to reflect standards in App. D. Table 9 - 7 2006
3 Update Wetland Ordinance Update to reflect Plan recommendations. Table 11 - 3 2007
Identify stream bank protection Identify improvement locations during Table 13 - 3 2006
4
needs at storm outlets NPDES outfall inspections process. -07
Select/create storm system Identify long-term system for record Table 17 - 3 2006
5
inspections/reporting database keeping, planning and reporting. -07
Pond LL-P7.5 (Lotus Lake Proposed pond installation in current Table 25, 2007
6
watershed) lake association property. Appendix I
7 Pond LL-P10.17 (Lotus Lake Add treatment adjacent to channel / Table 25, 2008
watershed) wetland in backyards. Appendix I
8 Pond LL-P2.2 (Lotus Lake Add treatment area adjacent to wetland Table 25, 2008
watershed) on lake association property. Appendix I
9 Pond LM-P8.8 (Minnewashta Add pond in Fir Tree street recon project Table 27, TBD
watershed) area. MCWD P-reduction project. Appendix G, I
10 Pond LM-P1.5 (Minnewashta Pond in City park, Orchard Lane street Table 27, TBD
watershed) recon area. MCWD P-reduction project. Appendix G, I
11 Pond LR-P2.3 (Lake Riley Potential pond in Bandimere Park Table 29, TBD
watershed) Appendix I
12 Proposed pond installation in current Table 29, TBD
Pond LR-P2.6 (Lake Riley)
lake association property. Appendix I
The City currently has a storm water utility (Surface Water Management Utility Fee) in place.
The 1994 Surface Water Management Plan recommended the establishment of a trunk fee
system for new development. This funding served to supplement the existing surface water
utility fee. The surface water connection charge is a one-time charge payable upon subdivision of
a property. The connection charge includes a water quality and a water quantity fee for each net
developable acre. For the purpose of fee calculations, the net developable area generally includes
total site area after subtracting the land that will not be developed, including right-of-way for
some roads, wetlands, ponds and parks.
The surface water management utility fee is a quarterly fee charged to each property within the
City. Single family residential, rural residential, agricultural and undeveloped properties are
charged a fixed quarterly fee. All other land uses are charged based on a base rate multiplied by
the utility factor for the land use, multiplied by the acreage of the parcel, exempting public right-
of-way and lakes.
These revenue sources will be continued in order to fund surface water management activities
within Chanhassen. The charges and fees will be reviewed and adjusted annually to ensure
adequate funding for the activities set forth in this plan and those required by law. In order to
establish a baseline estimate of the overall program costs for the next 20 to 30 years of the Plan,
individual activity and project cost estimates were developed. The costs represented below do
not account for the parts of the overall program implementation budget that include costs such as
staff salaries, street sweeping equipment, water quality monitoring equipment or sampling costs,
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and sweeping disposal costs. The costs also do not include land acquisition costs (capital or
legal) which may be necessary to implement the pond or water quality treatment BMPs
recommended in the Plan.
Table ES-3 summarizes the estimated implementation costs on an annual basis for the projects
and activities presented in Table 30. These estimated costs are intended here as an order of
magnitude estimate of the funding needed for the projects and activities identified in this Plan.
Table ES-4. Implementation Plan Summary/Overview
Estimated
Description Annual Costs
Category
(examples)(2006 Dollars)
Feasibility Study - Lotus Lake
Planning Costs
High Water Levels
$50,000
Studies
Review of Pond Easements
Ordinance Updates
Public Education Efforts
Update Ordinances
Public Education Materials and
Event Participation
Sediment Removal from Pond and
Capital Construction Costs
structural BMPs
$350,000
Construction of Ponds, Outlet
Storm Pond and BMP Construction
Structures and/or Structural
Costs
BMPs
Pond/BMP Cleanout
Updates to GIS Databases for
Operation and Maintenance
easements, pond projects, BMP
$35,000
Program Management
Tracking
New Technologies for
Program Management
Inspections Coordination with
County Staff
System and Site Inspections
NPDES Program Tracking Tools
Land/Easement Acquisition Varies
Property for water quality ponds
Estimated Total Annual Cost $435,000
Amendments to the Plan
For the SWMP to remain current and dynamic, an avenue must be available to incorporate new
information, ideas, methods, standards, management practices, and any other changes which may
affect the intent and/or results of the Plan. Amendment proposals can be requested any time by
any person or persons either residing in or having business within the City. Proposed
amendments are reviewed by staff, and if determined to be a reasonable and necessary
amendments the amendment may be implemented with or without Council action. If the
amendment is considered major, the need for a public hearing will be considered at a regular or
special Council meeting with the public having an opportunity to provide input. Council and the
WMOs have an opportunity to determine whether or not to approve of the proposed
amendments.
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ACKNOWLEDGEMENTS
City Council
Mayor Thomas Furlong
Steve Labatt
Brian Lundquist
Craig Peterson
Bethany Tjornhom
City Commissions
City Staff
Lori Haak Water Resources Coordinator
Don Asleson Natural Resources Technician
Kate Aanenson Community Development Director
Todd Gerhardt City Manager
Todd Hoffman Park and Recreation Director
Justin Miller Assistant City Manager
Paul Oehme Public Works Director/City Engineer
Greg Sticha Finance Director
SEH Staff
Ron Leaf Project Manager
Erin Krueger Project Engineer
Deric Deuschle Wetland Scientist
Reviewing Agencies
Minnehaha Creek Watershed District
Riley Purgatory Bluff Creek Watershed District
Lower Minnesota River Watershed District
Carver County Water Management Organization
Minnesota Pollution Control Agency
Metropolitan Council
Task Force Members
Ladd Conrad Citizen At Large
Annette Ellson Citizen At Large
Kurt Papke Planning Commission Member
Lee Scholder Environmental Commission Member
Leslie Shneider Citizen At Large
Glenn Stolar Park and Recreation Commission
Bethany Tjornhom City Council Member
Technical Committee Members
Julie Ekman Department of Natural Resources Area Hydrologist
Paul Moline Carver County Water Management Organization
Aaron Mylnek Carver County Soil and Water Conservation District
Bob Obermeyer Riley Purgatory Bluff Creek Watershed District Engineer
Brad Wozney Board of Soil and Water Resources Board Conservationist
Mike Wyatt Minnehaha Creek Watershed District Planner
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EXECUTIVE SUMMARY
ACKNOWLEDGEMENTS
TABLE OF CONTENTS
I. INTRODUCTION .................................................................................................. 1
A. Purpose of the Plan .............................................................................................. 1
B. Basis for the Plan ................................................................................................. 1
1. Regulatory Basis ............................................................................................ 1
a. Metropolitan Surface Water Management Program .................................. 2
b. Watershed Management Organizations .................................................... 2
2. Related Surface Water Programs .................................................................... 3
a. NPDES Phase II Storm Water Permit Program ......................................... 3
b. Wetland Management Plan....................................................................... 4
C. Water Resources Related Agreements.................................................................. 4
D. Plan Overview ..................................................................................................... 4
E. Plan Development Process ................................................................................... 5
1. 1994 Plan Information ................................................................................... 6
2. SWMP Task Force ......................................................................................... 6
a. Vision Statement for the SWMP .............................................................. 6
3. Technical Committee ..................................................................................... 8
4. Internal (City) Review ................................................................................... 8
5. Agency and Public Review ............................................................................ 8
II. BACKGROUND, HISTORY AND PHYSICAL ENVIRONMENT ....................... 9
A. Soils and Geology................................................................................................ 9
1. Soil Associations ......................................................................................... 10
2. Hydrologic Soil Groups and Infiltration Capacities ...................................... 10
B. Vegetation ......................................................................................................... 11
C. Precipitation ...................................................................................................... 12
D. Land Use ........................................................................................................... 13
1. Impervious Surfaces and Water Quality ....................................................... 13
2. TH 212 – Anticipated Impacts on Water Resources ..................................... 14
E. Public Utilities ................................................................................................... 14
F. Water-Based Recreation Areas .......................................................................... 15
G. Unique Features and Scenic Areas ..................................................................... 16
1. Assumption Creek ....................................................................................... 16
2. Seminary Fen ............................................................................................... 16
3. Bluff Creek .................................................................................................. 17
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H. Pollutant Sources ............................................................................................... 17
I. Groundwater Resource Data .............................................................................. 17
J. Fish and Wildlife Habitat ................................................................................... 18
III. GOALS AND POLICIES ..................................................................................... 19
A. Goal 1: Water Quantity ...................................................................................... 20
1. Hydrologic Modeling Update ....................................................................... 22
2. Implementation Plan .................................................................................... 23
B. Goal 2: Water Quality ........................................................................................ 25
1. Water Quality Information ........................................................................... 27
2. Implementation Plan .................................................................................... 27
C. Goal 3: Wetland Protection ................................................................................ 29
1. Wetland Management Program .................................................................... 29
2. Implementation Plan .................................................................................... 30
D. Goal 4: Erosion and Sediment Control ............................................................... 30
1. Implementation Plan .................................................................................... 32
E. Goal 5: Financing .............................................................................................. 32
1. Implementation Plan .................................................................................... 33
F. Goal 6: Regulatory Responsibility ..................................................................... 33
1. NPDES Phase II SWPPP ............................................................................. 34
2. Implementation Plan .................................................................................... 35
G. Goal 7: Public Education and Participation ........................................................ 35
1. Watershed District and County Programs ..................................................... 36
2. City Programs .............................................................................................. 36
3. Implementation Plan .................................................................................... 37
IV. SURFACE WATER RESOURCES ...................................................................... 39
A. Overview ........................................................................................................... 39
B. Lakes ................................................................................................................. 43
1. Background and Previous Findings .............................................................. 43
2. Methods and Approach ................................................................................ 44
a. Lake Ann (MNDNR I.D. No. 10-12P) .................................................... 45
b. Christmas Lake (MNDNR I.D. No. 27-137P) ......................................... 47
c. Lotus Lake (MNDNR I.D. No. 10-6P) ................................................... 48
d. Lake Lucy (MNDNR I.D. No. 10-7P) .................................................... 50
e. Lake Minnewashta (MNDNR I.D. No. 10-9P) ....................................... 52
f. Rice Lake (MNDNR I.D. No. 27-132P) ................................................. 54
g. Rice Marsh Lake (MNDNR I.D. No. 10-1P) .......................................... 54
h. Lake Riley (MNDNR I.D. No. 10-2P) .................................................... 55
i. Lake Susan (MNDNR I.D. No. 10-13P) ................................................. 57
j. Lake St. Joe (MNDNR I.D. No. 10-11P) ................................................ 60
3. Lakes Summary ........................................................................................... 60
C. Creeks and Linear Waterways ........................................................................... 65
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1. Assumption Creek ....................................................................................... 65
2. Bluff Creek .................................................................................................. 66
3. Lake Minnewashta Outlet ............................................................................ 67
4. Purgatory Creek ........................................................................................... 68
5. Riley Creek .................................................................................................. 68
6. Unnamed Creek – Southeast Bluff Area: ...................................................... 69
7. Minnesota River .......................................................................................... 69
D. Storm Water Ponds ............................................................................................ 70
E. Drainage to Subwatersheds Outside of Chanhassen ........................................... 70
V. WETLANDS MANAGEMENT ........................................................................... 73
A. Overview ........................................................................................................... 73
B. Existing Wetland Regulations ............................................................................ 74
1. Minnesota Wetland Conservation Act .......................................................... 74
2. Minnesota Department of Natural Resources ............................................... 74
3. United States Army Corps of Engineers ....................................................... 75
4. Watershed Management Organizations ........................................................ 75
C. 2006 Wetland Inventory .................................................................................... 75
1. Methods ....................................................................................................... 76
2. Inventory Data Format and Information ....................................................... 77
3. Inventory Results ......................................................................................... 81
a. Wetlands ................................................................................................ 81
b. Lakes ..................................................................................................... 83
c. Linear Waterways .................................................................................. 83
4. Limitations on Inventory .............................................................................. 84
5. Comparison to the 1992 Inventory ............................................................... 85
6. Comparison to MCWD Inventory ................................................................ 87
D. Functions and Values Assessment ..................................................................... 87
1. Methods ....................................................................................................... 88
E. Classification and Management Standards ......................................................... 91
1. Description of Standards .............................................................................. 91
1. Preserve ....................................................................................................... 92
2. Manage – 1 .................................................................................................. 94
3. Manage – 2 .................................................................................................. 95
4. Manage – 3 .................................................................................................. 96
2. Results ......................................................................................................... 96
F. Wetland Buffer Standards .................................................................................. 97
G. Storm Water Susceptibility ................................................................................ 97
H. Potential Wetland Mitigation and Restoration Sites ........................................... 98
VI. IMPLEMENTATION PLAN ............................................................................. 101
A. Overview ......................................................................................................... 101
B. Implementation Priorities and Costs ................................................................ 107
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C. Amendments to the Plan .................................................................................. 109
1. Amendments Procedures ............................................................................ 109
2. Request for Amendments ........................................................................... 109
3. Staff Review .............................................................................................. 110
4. WMO Approval ......................................................................................... 110
5. Council Consideration ............................................................................... 111
6. Public Hearing and Council Action ............................................................ 111
7. Council Adoption ...................................................................................... 111
LIST OF FIGURES (APPENDIX A)
FIGURE 1 CITY LOCATION MAP
FIGURE 2 WATERSHED BOUNDARIES
FIGURE 3 SOIL HYDROLOGIC GROUP
FIGURE 4 EXISTING LAND USE
FIGURE 5 PROPOSED 2020 LAND USE
FIGURE 6 PROTECTED WATERS
FIGURE 7 WATER FEATURES MANAGEMENT CLASS
FIGURE 8 NEIGHBORHOOD STUDY LOCATIONS
FIGURE 9 STORMWATER PONDS
FIGURE 10 NWI WETLANDS
FIGURE 11 MCWD-CITY INVENTORY COMPARISON
FIGURE 12 WETLAND INVENTORY
FIGURE 13 POTENTIAL WETLAND MITIGATION SITES
LIST OF TABLES
Table 1. Plan Goals and Goal Statements .................................................................. 5
Table 2. Approximate Watershed Surface Areas ....................................................... 9
Table 3. Rainfall Data for the Minneapolis-St. Paul Metropolitan Area................... 12
Table 4. Summary of Water-Based Recreational Facilities ...................................... 16
Table 5. Plan Goals and Goal Statements ................................................................ 20
Table 6. Water Quantity Policies ............................................................................ 21
Table 7. Water Quantity Implementation Plan ........................................................ 24
Table 8. Water Quality Policies .............................................................................. 26
Table 9. Water Quality Implementation Plan .......................................................... 28
Table 10. Wetland Protection Policies .................................................................... 29
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Table 11. Wetland Implementation Plan ................................................................. 30
Table 12. Erosion and Sediment Control Policies ................................................... 31
Table 13. Erosion and Sediment Control Implementation Plan ............................... 32
Table 14. Financing Policies ................................................................................... 33
Table 15. Financing Implementation Plan ............................................................... 33
Table 16. Regulatory Responsibility Policies .......................................................... 34
Table 17. Regulatory Responsibility Implementation Plan ...................................... 35
Table 18. Public Education and Participation Policies ............................................. 36
Table 19. Public Participation, Information and Education Implementation Plan .... 37
Table 20. Water Management Classification for Chanhassen Water Features .......... 41
Table 21. TMDL Listed Impaired Waters in Chanhassen ........................................ 42
Table 22. Lake Physical Characteristics .................................................................. 44
Table 23. Lake Ann Proposed Ponds Prioritization ................................................. 46
Table 24. Christmas Lake Proposed Ponds Prioritization ........................................ 48
Table 25. Lotus Lake Proposed Ponds Prioritization ............................................... 49
Table 26. Lake Lucy Proposed Ponds Prioritization ................................................ 51
Table 27. Lake Minnewashta Proposed Ponds Prioritization ................................... 53
Table 28. Rice Marsh Lake Proposed Ponds Prioritization ...................................... 55
Table 29. Lake Riley Proposed Ponds Prioritization ............................................... 57
Table 30. Lake Susan Proposed Ponds Prioritization............................................... 59
Table 31. Lake Management Recommendation Summary....................................... 62
Table 32. Bluff Creek Subwatershed Proposed Ponds Prioritization........................ 67
Table 33. Minnewashta Outlet Creek Subwatershed Proposed Ponds Prioritization 67
Table 34. Purgatory Creek Subwatershed Proposed Ponds Prioritization................. 68
Table 35. Minnesota River Subwatershed Proposed Ponds Prioritization ................ 70
Table 36. Mitchell Lake Subwatershed Proposed Ponds Prioritization .................... 71
Table 37. Lake Hazeltine Subwatershed Proposed Ponds Prioritization .................. 71
Table 38. Circular 39 and Cowardin Classification System Summary ..................... 79
Table 39. Wetland Classification Summary ............................................................ 81
Table 40. Summary of Basins Based on Wetland Type ........................................... 83
Table 41. Results of 1992 Wetland Inventory ......................................................... 85
Table 42. Recommended Wetland Management Strategies ..................................... 93
Table 43. Results of 2002 McRAM and 2005 Chanhassen Wetland Inventories...... 96
Table 44. Susceptibility of Wetlands to Degradation by Stormwater Impacts .......... 97
Table 45. Implementation Program Priority Projects and Activities ...................... 101
Table 46. Implementation Plan Summary/Overview ............................................. 103
Table 47. Surface Water Management Fees in Chanhassen ................................... 108
Table 48. Implementation Plan Financial Summary .............................................. 109
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LIST OF APPENDICES
APPENDIX A FIGURES 1
APPENDIX B ACRONYMS AND GLOSSARY 1
APPENDIX C LITERATURE REVIEW AND WEBSITE LINKS 1
APPENDIX D DEVELOPMENT STANDARDS 1
APPENDIX E HYDROLOGIC SYSTEM TABLES 1
APPENDIX F LAKE BACKGROUND INFORMATION 1
APPENDIX G NEIGHBORHOOD STUDIES 1
APPENDIX H GOALS AND POLICIES 1
APPENDIX I RECOMMENDED PONDS - STATUS SUMMARY 1
APPENDIX J NPDES MS4 PERMIT SWPPP (SUMMARY) 1
APPENDIX K WETLAND ORDINANCE RECOMMENDATIONS 1
APPENDIX L SUMMARY OF MNRAM 3.0 OUTPUT 1
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I.INTRODUCTION
The City of Chanhassen (City) has completed this second generation Surface Water Management
Plan (SWMP or Plan) to establish a more useful and up-to-date resource for guiding surface
water management activities throughout the City. This Plan builds on the City’s 1994 SWMP,
and addresses several key issues related to storm water management that the City is likely to
encounter in the coming years. This introductory section begins with a brief description of the
purpose and basis for this updated Plan, followed by an outline of the major sections of the seven
overriding goals that were used to guide development of the Plan.
The City of Chanhassen is located in the southwestern suburbs of the Twin Cities metropolitan
area in east central Carver County, with 154 acres in Hennepin County, as shown on Figure 1.
The City is bordered by Shorewood, Excelsior and Minnetonka to the north, Eden Prairie to the
east, Shakopee to the south, and Chaska and Victoria to the west. The City is located within the
jurisdictional boundaries of four watershed management organizations. Cumulatively, lakes,
wetlands, streams and ponds account for approximately 26% of the City’s surface area.
A.Purpose of the Plan
The purpose of this Plan is to establish the framework of a comprehensive program that does
more than simply protect and improve the quality of existing water resources within the City.
The Plan also recognizes that development must and will continue well into the future, and will
serve as a guide for City staff to follow as they evaluate the potential impacts of a given project
on these quality resources. The Plan will serve as a toolbox for the City that includes the best
available water resource data at the time it was completed, up-to-date policies and design
standards, and a process to adjust goals and policies as new data is collected and evaluated or as
complimentary programs change.
B.Basis for the Plan
1.Regulatory Basis
There are a number of programs that deal with surface water management issues in Minnesota.
State laws and rules, specifically Minnesota Statutes, Sections 103B.201 to 103B.255 and
Minnesota Rule, Chapter 8410 (http://www.revisor.leg.state.mn.us), establish the regulatory need
to update the City’s initial Surface Water Management Plan (Bonestroo Rosene Anderlik and
Associates, 1994). These statutes and rules comprise the State’s Metropolitan Surface Water
Management Program (MSWMP), which requires the preparation of watershed plans by
watershed management organizations (WMOs), and the preparation of local water management
plans that are consistent with the respective WMO plans. This program also requires
municipalities to develop a Second Generation Local Surface Water Management Plan. This
program includes the requirement that the City Plan needs to be approved by the WMOs that
operate within the City.
A second regulatory program, very much related to the goals, policies and standards of this Plan,
is the National Pollutant Discharge Elimination System (NPDES) Phase II Storm Water Permit
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Program that is administered in the State by the Minnesota Pollution Control Agency (MPCA)
(http://www.pca.state.mn.us). This program has many similarities to the MSWMP, and both
programs were considered with the Plan update. Additional information on the purposes and
background for each of the two programs, including information on the four WMOs that exist
within Chanhassen, follows.
a.Metropolitan Surface Water Management Program
The purposes of the MSWMP is that through policies and thoughtful program implementation,
goals for proper water and wetland resource management can be realized and water quality can
be protected. Such a program requires cooperation with neighboring communities, counties, state
agencies, and WMOs. Through proper planning and implementation, informed decisions can be
made which allow for the protection and/or enhancement of water quality, prevention of ground
water degradation, and reduction of local flooding.
The purpose of the water management programs required by Minnesota Statutes §103B.205 to
103B.255 are to:
Protect, preserve, and use natural surface and groundwater storage and retention systems;
Minimize public expenditures needed to correct flooding and water quality problems;
Identify and plan for means to effectively protect and improve surface and groundwater
management;
Establish more uniform local controls for surface and groundwater management;
Prevent erosion of soil into surface water systems;
Promote groundwater recharge;
Protect and enhance fish and wildlife habitat and water recreation facilities; and
Secure benefits associated with the proper management of surface and ground water.
b.Watershed Management Organizations
Under the MSWMP (http://www.bwsr.state.mn.us), the City is required to submit its updated
SWMP to WMOs having jurisdiction within the City. Chanhassen is located within four major
watershed units, including the Minnehaha Creek Watershed District (MCWD)
(http://www.minneahahacreek.org), the Riley Purgatory Bluff Creek Watershed District
(RPBCWD) (http://www.rileypurgatorybluffcreek.org), the Lower Minnesota River Watershed
District (LMRWD) (http://www.watersheddistrict.org), and the Carver County Water
Management Organization (CCWMO) (http://www.co.carver.mn.us/water). These watersheds
are shown on Figure 2A, which illustrates the jurisdictional boundaries of the watershed units.
All four of the WMOs have jurisdictional authority within the City, and therefore each must
review the City’s Plan to evaluate consistency with the respective WMO Plan. As of August
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2006, the MCWD is in the process of updating its Plan, RPBCWD plans to update its Plan in
2006, and CCWMO will update its plan by 2008.
This updated SWMP addresses each of the required elements in Minnesota Statutes and Rules
and is consistent with the Metropolitan Council’s guidelines for Water Management Plans. The
Plan has been prepared to be consistent with the MCWD, RPBCWD, LMRWD, and CCWMO
Plans. The criteria set forth in this Plan, as a minimum, establish the degree of performance
necessary to achieve improvement in water quality and water quantity management. These
criteria are not intended to dictate or preempt the design process, but rather provide guidelines to
proper development and redevelopment.
This Plan represents a unique combination of resource management, regulatory controls and
public works management. As discussed above, State Statutes and Rules require that a plan be
prepared for each watershed in the seven county metropolitan area. Local (i.e., City) plans must
also be prepared and approved by the applicable watersheds and reviewed by the Metropolitan
Council. Once approved by the WMOs and adopted by council, the Plan becomes part of the
City’s overall Comprehensive Plan. The Plan is geared towards meeting the mutual goals of all
of the WMO’s within the City.
2.Related Surface Water Programs
a.NPDES Phase II Storm Water Permit Program
The NPDES Phase II Storm Water Permit Program is a federal regulatory program that requires
owners of Municipally Separate Storm Sewer Systems (MS4s) to prepare and implement a Storm
Water Pollution Prevention Program (SWPPP) and apply for the permit with the administrative
agency. The Minnesota Pollution Control Agency (MPCA) administers the Phase II MS4
program in the state (http://www.pca.state.mn.us). The City submitted their permit application
and SWPPP prior to the March 10, 2003, initial submittal deadline. A revised permit was issued
by the MPCA in 2006 and the City completed a revised SWPPP during the final stages of this
SWMP update. This SWMP does not specifically incorporate all of the best management
practices (BMPs) identified in the City’s SWPPP. Instead, the Plan builds on these existing
activities by specifying projects and management approaches to achieve the City’s water
resources goals.
One step in meeting the Phase II requirements included a self assessment process that the City
completed to prepare their Notice of Intent (NOI or permit application) for coverage under the
NPDES MS4 Phase II. In this process, the City considered receiving waters, the City’s existing
storm water management plan, and a range of BMPs that could be followed to achieve the MS4
permit requirements. The self assessment resulted in an understanding of the City’s current storm
water programs and future priorities. A key part of this SWMP update was the completion of an
initial inspection of outfalls and inventory of the City’s storm water infrastructure. This
inventory is discussed more in Section II and III of the Plan. Appendix I contains a summary of
the City’s NPDES Program SWPPP.
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b.Wetland Management Plan
Additionally, as part of the SWMP update, many components of a comprehensive wetland
management plan (CWMP) were completed and are summarized in Section V of this Plan. While
the result of this Plan update was not establishment of a CWMP under the state rules, several of
the major efforts were consistent with the state rules. Included in this effort was the completion
of a Minnesota Routine Assessment Method Version 3.0 (MnRAM 3.0) evaluation for
essentially all wetlands within the City. A draft wetland ordinance was also prepared and is
provided in Appendix K. The data presented in this Plan serves as an update to the City’s 1994
Wetland Inventory.
C.Water Resources Related Agreements
The City of Chanhassen has an agreement with the Carver County Soil and Water Conservation
District (CCSWCD) that states the CCSWCD will assist the City in performing Erosion and
Sediment Control Inspections at construction projects in the City. The City also has an
agreement for the Citizen Assisted Monitoring Program (CAMP) that includes monitoring at 4
lakes within the City; Lake St. Joe, Lotus Lake, Lake Susan, and Lake Riley.
D.Plan Overview
One of the first steps taken to develop this Plan was to gather and compile the best available
information and data from a number of resources. Sources of these data include the City’s 1994
Surface Water Management Plan, the WMO plans, MPCA NPDES Program and other relevant
sources. This data and information was then reviewed and evaluated as part of the update
process. See Appendix C for a summary of the information reviewed and evaluated. Following
this Introduction section, subsequent sections address the background, history and description of
the existing physical environment (Section II); goals and policies (Section III); key water bodies
within the City (Section IV), wetlands management and inventory (Section V), and establish an
implementation plan to guide future projects and management activities for the protection and
future enhancement of the City’s water and wetland resources (Section VI).
Using the seven goals presented in Table 1, the Plan is intended to guide surface water resource
management activities through about the year 2020. Though long term in focus, the Plan has
numerous future decision points relating to recommended capital improvements and ongoing
inspection, maintenance and monitoring activities. Where applicable, staff and financial
resources of the City, WMOs, and adjacent communities are called on to maximize the
effectiveness of the results. The Plan was developed recognizing the need to prioritize
management actions and decisions based on the protection level of a given receiving water (i.e.,
lake or wetland), as established by the City.
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Table 1. Plan Goals and Goal Statements
Goal
Goal Goal Statement
Number
Water Quantity Provide at least 100-year (1% chance) flood protection for all structures.
1
Water Quality Achieve water quality standards in lakes, streams, and wetlands consistent
2
with their designated uses and established classifications.
Wetlands Protect and rehabilitate wetlands to maintain or improve their function and
3
value.
Erosion and Minimize soil erosion and sedimentation.
4
Sediment Control
Financing Establish and maintain funding sources to finance activities of this Plan.
5
Regulatory Maintain primary responsibility for managing water resources at the local
6
level but continue coordination and cooperation with other agencies and
Responsibility
organizations.
Public Education and Provide information and educational resources to improve knowledge and
7
Information promote an active public role in management of water resources.
E.Plan Development Process
The updated Plan was developed over about a twenty month period starting in December 2004
and wrapping up in August 2006. The process included many steps and coordination, including
significant efforts by members of a City Task Force, informal and formal meetings with the
Technical Committee, City Council and Planning Commission, and a public hearing to allow
residents an opportunity to provide input in the planning process. The key milestones are
summarized directly below and a more detailed description of each major step follows.
Milestone/ActivityDate
Task Force Meetings #1 to #6 (Monthly) Aug. 2005 – Jan. 2006
Draft #1 - Delivered to Staff/PC/CC January 18
Planning Commission/Council Joint Meeting February 13
Task Force Meeting #7 – Review Comments February 15
Internal Review Process Completed for Draft #1 February 15
Revise and Prepare Agency Review Draft – Complete by March 27
Draft #2 - Deliver to Agencies for Review March 27
1 st Planning Commission Meeting – Open Public Hearing April 4
2nd Planning Commission Meeting – Close Public Hearing May 2
60-Day Agency Review Period Ends May 5
Respond to Agency Comments, Gain Approvals August
Final Planning Commission Meeting – Close Public Hearing August 15
Final Council Meetings – Adoption of Plan August 28
Draft #3 - Delivery of Final Plan (after Adoption by Council) September
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1.1994 Plan Information
The first step in the plan development process was to use the 1994 Plan as a basis, and review
and compile the information available as related to the City’s surface water system and
resources. As part of the 1994 Plan the City completed a HydroCAD model that included all of
the surface water features and several proposed storm water ponds. The City also completed a
wetland inventory, and established water quantity and quality standards for future development.
The information in the 1994 Plan was reviewed and used as a starting point in the completion of
the Plan update. In addition to the 1994 Plan and the technical information available, the City
also gathered valuable information from the Task Force that was created as part of the Plan
update. See Appendix C for a list of the materials reviewed for this Plan.
2.SWMP Task Force
The Task Force was formed by the City to assist in the Plan update process. The Task Force was
made up of individuals from the City Council, Environmental Commission, Planning
Commission, Park and Recreation Commission, and three citizens-at-large. One of the citizen
members also served on the 1994 Plan Update Task Force. The Task Force participated in seven
meetings with City Staff, assisted in establishing the goals and policies of the Plan and spent
numerous hours of their own time to help produce this 2006 Plan. Their efforts and dedication in
assisting the City with the Plan update are greatly appreciated.
a.Vision Statement for the SWMP
The Task Force developed the following vision statement for the Surface Water Management
Plan to provide a backdrop for current and future users of the plan. The purpose of the vision
statement is to convey to the reader the ideas that guided the work of the Task Force and the
major themes that developed in the course of the Task Force’s discussions.
Task Force Vision Statement
Because water covers approximately 26% of the land within Chanhassen, a commitment to
maintaining and improving the City’s surface water resources is essential. Demonstrating
this commitment should be a priority for the City in its municipal operations. The
management of City facilities, equipment and property should reflect an emphasis on
preserving and enhancing the quality of the community’s water resources. The City should
only expect protection and improvement of water resources by others (including residents,
businesses, developers and contractors) if the City demonstrates those same values in its
day-to-day operations.
The City’s commitment to water resource preservation and enhancement should be
demonstrated through the use of appropriate best management practices in its capital
projects, as well as its general operations. The City should continue to investigate and
implement, where appropriate, new methods for water resource management. Ordinances
and funding should be adequate to support the goals, policies and capital improvements set
forth in this Plan.
Continued…
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Task Force Vision Statement
(continued)
Simply stated, the vision of the task force is for the City to set the bar for water resources
protection in Chanhassen and for others to follow the City’s example. Five major themes that
support this vision have been identified:
1. Chanhassen must set realistic goals, and measure and report progress annually. In
the decade that has passed since the first SWMP was adopted, several of the original goals
and policies have been found to be unrealistic. These items have been revised to reflect
more attainable, manageable expectations. Where possible, it is also important for the City to
be able to quantify its progress. To that end, a system for measuring and reporting progress
toward the SWMP goals on an annual basis is necessary. Only when the City is accountable
for its management of surface water will the goals set forth in this plan be truly realized, and
the plan update will be a more valuable document.
2. Chanhassen must prioritize improvements and finance the surface water
management fund to a level that will facilitate implementation of priority
improvements, goals and recommendations of the plan. Funding should be based on
the need for resource protection and the implementation of recommended improvements. As
costs of materials, land and labor continue to increase, the surface water management plan’s
goals and recommendations may become difficult to achieve if financial considerations are
not kept in mind.
3. Chanhassen must protect its “Crown Jewel” resources. The City of Chanhassen has
many natural resources within its borders. Two of them have been identified by the City and
others to be of exceptional natural resource value. Assumption Creek and the Seminary Fen
should be considered the “crown jewels” of Chanhassen and must be priority resources with
regard to this Plan. City policy and operations should work together with the regulations of
other agencies to protect these resources to the greatest extent practicable.
4. Chanhassen must protect and improve degraded resources within developing areas
of the City. The City of Chanhassen has been experiencing rapid growth and must consider
the water resources as a priority during development. It will be easier and less costly to
protect and improve resources by anticipating future difficulties and enacting more stringent
requirements as development occurs instead of going back later to resolve problems by
retrofitting. To achieve this, it is necessary to ensure that commissioners and council
members are well-informed, educated about water resources and have the technical
assistance necessary to anticipate water resource issues and to implement the City’s
regulations effectively.
5. Chanhassen must remain committed to improving the process for making water
resource related decisions through continued education. Local government officials,
City employees, consultants, developers, contractors, local businesses, school children and
the general public should receive consistent, clear information through a well-developed
water resources education program. This can be accomplished in part through means such
as the City’s website, the Chanhassen Connection, Cable Channel 8, presentations to the
City’s council and commissions by staff and others, printed materials, and cooperation with
other educational professionals.
Continued…
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Task Force Vision Statement
(continued)
Complicating the City’s ability to work toward this vision is the fact that surface water
regulations, with implications for the City, are in a period of transition. Additional
requirements and standards that are implemented in the future by local, state and federal
agencies cannot be completely known or anticipated during any plan update. However, this
surface water management plan should be a living document that can direct water resources
management and planning activities for years to come.
By working together with a shared vision, this Plan will help the City of Chanhassen and
those who live and work here not only protect but also improve the water resources that are
integral to this community.
3.Technical Committee
Additionally, a Technical Committee consisting of representatives from the WMOs, Carver
County, Board of Water and Soil Resources (BWSR), and the Department of Natural Resources
(DNR) was also formed. The team attended two meetings with City staff to go over the goals,
policies, and design standards of the SWMP update.
4.Internal (City) Review
Based on the input and guidance received through the Task Force and Technical Review Team, a
Draft Plan was prepared for internal review by staff, the Task Force members, the Planning
Commission and City Council. Comments were collected from this review and incorporated into
the Plan.
5.Agency and Public Review
Once the internal review was complete, an Agency Review Draft of the Plan was prepared and
submitted to the agencies and WMOs that have jurisdiction in the City of Chanhassen for their
review and comment. In addition, the Plan was made available for public review during this
period, including a formal Public Hearing process. Once this review was complete and the
SWMP was finalized, the Plan was adopted by the City Council.
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II.BACKGROUND, HISTORY AND PHYSICAL ENVIRONMENT
The City has a variety of lakes, wetlands and waterways that provide aesthetic, environmental
and recreational value to the community. The City has an area of approximately 15,400 acres or
about 24 square miles of land. Water bodies, including lakes, ponds, wetlands, streams and
rivers, constitute approximately 3,975 acres, about 26 percent of the City. Portions of four major
watersheds exist with in the City (See Figure 2A). Table 2 provides the approximate surface
areas of the City that are encompassed by the four watersheds units. These data are not intended
to represent the exact areas within the watershed legal boundaries or hydrologic boundaries.
Instead the areas are presented to illustrate the relative area of each within the City.
Table 2. Approximate Watershed Surface Areas
1
Watershed Area Area (acres) Percentage of City (%)
Carver County Watershed 300 1.9
Lower Minnesota River Watershed 1,300 8.4
Minnehaha Creek Watershed 2,900 18.8
Riley Purgatory Bluff Creek Watershed 10,900 70.9
1. Areas are approximate and rounded to the nearest 100 acres.
There are 12 lakes, approximately 356 wetlands, 171 storm water ponds, and 4 creeks located
wholly or partially within the City. One of these creeks, Bluff Creek, runs the entire length of the
City and there are numerous bluffs and wooded areas along the creek. Chanhassen also has a
number of public open spaces located throughout the community, including the Minnesota
Landscape Arboretum, Lake Minnewashta Regional Park, and Lake Ann Park. Section IV
presents more detailed information on the water bodies within the City.
The largest type of land use in the City is low-density residential. There are numerous areas of
commercial and industrial land use, the largest contiguous area being the downtown area of
th
Chanhassen, along West 78 Street. The City has experienced increased growth throughout the
1990s and into the 2000s and is considered a developing community, as discussed in the City’s
Comprehensive Plan. Prior to the more recent development activity, the City mostly consisted of
agricultural land use. Overall, the low-density residential development will remain the largest
land use, with some higher density residential areas, employment centers and shopping areas.
A.Soils and Geology
The topography of this area is gently to steeply rolling. Many depressions of various sizes are
present in the overall topography. The numerous lakes and wetlands found in the City fill these
depressional areas. The natural drainage in the City is fairly complicated since there is no
prevailing direction for surface flow.
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1.Soil Associations
The major soil associations present in the City is the Hayden-Lester-Peat. The Hayden and
Lester series are deep, well-drained soils. Peat soils are associated with wet depressions and
drainageways. Pockets of other soil types exist including poorly drained Cordova, Webster, and
Glencoe soils and the moderately well drained LeSueur and Terril loamy soils. The Minnesota
River Valley possesses two associations, the Alluvial land-Chaska-Oshawa association, and to
the west the Salida-Hayden association. The latter association is characterized by coarse to
medium-textured soils on steep slopes and bluffs overlooking the river. The former association is
characterized by alluvial soils that are typically fine-grained silts and are very poorly drained.
The central portion of the City, with its more gentle topography, is covered with larger amounts
of Lester soils than any other type. Lester soils are generally well drained and have a moderately
thick, organic-rich top soil. The rest of the watershed not included in the Lower Minnesota
Watershed or central region contains predominantly Hayden soils. The Hayden soils are similar
to the loamy Lester soils but contain less organic matter and a thinner mantle of top soil. All the
non-alluvial soils in the City have formed over glacial till. The most recent glacial coverage of
Carver County was the Mankato substage of the Wisconsin continental glacier. The calcareous,
clay loamy material and limestone rock fragments carried by the last ice sheet advance are the
parent material for most of the soils in the City.
The soils associated with the Minnesota River Valley originated predominantly from glacial
outwash. This material, deposited by the escaping melt waters of glaciers, is often well sorted
and can range from gravel to fine clays depending on the location. The cutting action of the river
exposes different layers deposited by earlier advances of the ice sheets. The diverse mixture of
parent materials exposed and transported by the river’s erosional processes is often deposited by
the river’s waters in well sorted layers. The layering is dependent on the size of the material and
the river’s flow, which will vary in time and space. The result is a complex network of layers that
are difficult to predict and must be checked at individual sites in the field.
2.Hydrologic Soil Groups and Infiltration Capacities
Soils in the City vary widely. Some areas have well drained soils, and other areas, near the
numerous wetlands, are usually poorly drained. Figure 3 illustrates soil types relative to their
hydrologic soil group (HSG). The HSG is an indicator of the relative infiltration rate of the soil.
HSG “A” soils have relative high natural infiltration rates and HSG “D” soils generally have
very low natural infiltration rates as described below. Infiltration capacities of soils can affect the
amount of direct runoff resulting from a rainfall event. Generally, the higher the infiltration rate a
soil is given, the lower the runoff potential. Conversely, soils with low infiltration rates produce
relatively high runoff volumes and peak discharge rates. Four general hydrologic soil groups for
soils based on texture and slope have been established by the Natural Resource Conservation
Service (NRCS). The groups as shown in Figure 3 are:
Group A – Low runoff potential, high infiltration rate
Group B – Moderate infiltration rate
Group C – Slow infiltration rate
Group D – High runoff potential, very slow infiltration rate
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Soils within Chanhassen are predominately Group B soils, with large areas of Group C and D
soils, and a very small area of Group A soils. As part of the hydrologic assessment of this
planning project, the hydrologic grouping was evaluated along with future 2020 land use data to
estimate runoff characteristics that will occur over a given area for a particular rainfall amount.
These modeling efforts and results are discussed more in Section III of this Plan.
Soil characteristics are essential for completing hydrologic analyses and are also important when
developing erosion control plans. Special attention to erosion control measures and establishment
of interim cover during construction must be considered in areas of steep slopes, in areas with
highly erodible soil, and in areas with prolonged exposure of disturbed land. The erosion control
handbook published by the Board of Water and Soil Resources (BWSR) and the MPCA Storm
Water Manual (2005) include recommended best management practices for erosion protection.
B.Vegetation
The original vegetation in Chanhassen was a mosaic of plant communities adapted to the
climatic, topographic, geologic, and biologic conditions of the region at that time. According to
the 1994 Plan, four major communities originally occurred within Chanhassen’s City limits: oak
openings and barrens; Big Woods; wet prairies, marshes and sloughs; and river-bottom forest.
The oak openings and barrens mainly consisted of individual oak trees and islands of oaks
scattered amongst prairie grasses. These oak openings and barrens probably occupied a transition
zone between Big Woods and prairie communities. The Big Woods community was dominated
by red and white oak, sugar maple, and basswood trees, with numerous shrubs and herbaceous
species. Low pockets of wet prairies, marshes and sloughs were scattered within the big woods
region, and consisted of cattail in wetter sites, and willows, red osier dogwood, and sedges
dominating the seasonally flooded sites. The community at the southern limit of the City was the
Minnesota River and associated river bottom forest. This community was strongly influenced by
seasonal flooding.
Agricultural use in Chanhassen began around the mid-1800’s, with approximately 70 percent of
this area cleared for agricultural use since the late 1800’s. Wetlands were first drained for
cultivation and grading, and the draining was followed by filling of wetlands for development
purposes. These activities have significantly altered the quality and quantity of wetlands in the
City over the last century and a half.
The plant species composition has also been altered with the changes to the wetlands due to
associated land use changes. The scattered prairies, marshes and sloughs of pre-settlement
wetlands included many of the same species that still exist in wetlands, such as cattails,
bulrushes, iris, and willows. However, the mix and dominance of these species in most cases was
quite different than is encountered today. While the major species may be similar, the specific
interrelationship of the plant community was likely quite different.
Today most plant communities are characterized by the dominance of a single species within the
entire wetland or wetland zone, while other species are just scattered individuals. The largest
difference is the composition of grasses. Canada bluejoint and big bluestem were the prominent
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grasses throughout this area in pre-settlement times. Today, there are some high quality wetlands
with bluejoint grass present, but none with big bluestem prominent. Reed canary grass, which is
an exotic subspecies, is the dominant grass in most wetlands, and has displaced all other plant
species in many Chanhassen wetlands.
C.Precipitation
Climate within the Minneapolis-St. Paul metropolitan area is a humid continental climate with
moderate precipitation, wide daily temperature variations, warm humid summers and cold
winters. The total average annual precipitation is 29 inches. The average annual snowfall is
approximately 50 inches, equivalent to roughly 5 inches of water. Rainfall data for a variety of
return frequencies and storm duration for the Minneapolis-St. Paul metropolitan area is shown in
Table 3. The 100-Year, 24-hour storm event is the event used to design most flood control
structures and detention basins. This data is consistent with the Minnesota Hydrology Guide.
Table 3. Rainfall Data for the Minneapolis-St. Paul Metropolitan Area
Return
24-hr 12-hr 6-hr 3-hr 2-hr 1-hr 30-min 15-min
Frequency
1-Year 2.3 2.0 1.7 1.5 1.4 1.2 0.9 0.6
2-Year 2.8 2.4 2.1 1.7 1.7 1.4 1.1 0.7
5-Year 3.6 3.1 2.7 2.3 2.2 1.8 1.4 1.0
10-Year 4.2 3.7 3.1 2.6 2.5 2.1 1.7 1.3
25-Year 4.6 4.2 3.5 3.0 2.8 2.3 1.9 1.4
50-Year 5.3 4.6 4.0 3.4 3.1 2.7 2.1 1.5
100-Year 6.0 5.0 4.4 3.8 3.5 2.9 2.4 1.7
500-Year 7.4
Several rainfall parameters are considered in using the NRCS hydrologic design methodology.
Storm duration, rainfall depths, time distribution (how the total rainfall depth is distributed over
the duration of the rainfall event), and recurrence interval (how probable it is that the rainfall
event will recur in a given year) are important factors.
The 24-hour, NRCS Type II rainfall distribution with average soil moisture conditions (AMC-2)
is used for overall subwatershed planning within the City of Chanhassen. This is consistent with
the Minnesota Hydrology Guide’s distribution recommendation for hydrologic analysis of urban
areas. See Appendix B for more detail on Type II storm distributions.
The return period is related to the probability of a given event being equaled or exceeded. The
probability that the “100-year event” will be exceeded in a given year is 1 percent. Conventional
wisdom holds that if a 100-year event occurs in one year, then it cannot occur for another 100
years. This belief is false because it implies that rainfall occurs deterministically rather than
randomly. Because rainfall occurs randomly, there is a finite possibility that the 100-year event
could occur in two consecutive years or more frequently than one occurrence in any given year.
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More information on the NRCS design method or rainfall events is available at
http://www.nrcs.usda.gov, or on the State Climatology website at http://climate.umn.edu.
D.Land Use
The City of Chanhassen is considered to be a developing community, as discussed in the
Comprehensive Plan. The predominant land uses include single-family residential, parks, open
space and natural areas. Single-family residential will continue to be the predominant housing
type in the City, although housing types have slowly been shifting from this type of housing, and
becoming more diversified. Industrial development has been growing in the City in recent years,
and according to the City’s 2020 Land Use Plan it will make up approximately 9% of the City’s
area. Commercial land use will constitute approximately 1% of the City’s 2020 land use. Most of
th
the commercial development has taken place in the City’s downtown district, along West 78
Street. Figure 4 illustrates the existing land use, and Figure 5 illustrates the 2020 Land Use Plan
for the City. For more information on land use within the City of Chanhassen refer to the City’s
2020 Comprehensive Plan.
The City has created and maintained numerous park and open space areas throughout the City. In
addition, many outlots or natural areas are incorporated into new developments. While many of
these outlots are marginal lands for development, most contain wetlands or are used for storm
water detention, both of which can provide important wildlife habitat as well as aesthetic benefits
for the City.
Future land use projections help to identify areas that may be available for water resource
enhancements and also help to prioritize improvements. Significant changes in land use can
increase runoff rates and volumes due to the additional impervious surface, and degrade or
improve water quality depending on the type of change. As areas develop or redevelop at a
higher density, storm water runoff generally increases. Numerous studies have been completed
on the effect development can have on water quality. Without getting into great detail, the
general conclusions are that as the percentage of impervious cover increases, the greater the risk
to water quality. Generally speaking, water quality can be negatively impacted when the
impervious level in the watershed reaches as little as 10-15 percent of the total contributing area.
1.Impervious Surfaces and Water Quality
Treatment facilities like NURP ponds can help offset the impacts, but reducing the level of
impervious cover (or effective impervious) in the first place is gaining more support in
Minnesota and nationally every year. What has been termed low-impact development (LID), low
impact design, conservation site design as well as many others, is basically a process that strives
to create a site design that will have little to no adverse impacts on the surrounding water
resources.
While LID concepts can extend beyond water quality and water resource issues, the focus of this
discussion is on the concepts that could result in developments better managing their storm water
runoff by mimicking the existing site hydrology. A number of different site layout and physical
practices are combined to accomplish this goal. For example, some the practices include narrow
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streets (less impervious surface), rural road sections with adjacent grassed swales and without
curb and gutter, rain water gardens, bio-retention areas, infiltration basins and many others.
Chanhassen has some forms of these practices already established throughout the City.
Because a reduction in the impervious cover is one of the most effective LID practices, more and
more projects in Minnesota and throughout the nation are using pervious pavements; pavements
that are designed to let the rainfall pass through them into the underlying soils instead of directly
running off. These pavements come in many forms such as:
Paver blocks, with gaps between the blocks that allow rainfall to be infiltrated or filtered.
Porous asphalt and concrete which are similar to their impervious counterparts except
that larger pores are created to allow the rainfall to pass through the surface.
Structurally reinforced turf, in which a geo-engineered grid or underlayment is placed
below a typical turf grass area. The geo-grid allows heavier traffic to use the are without
significantly compacting the soils, thus maintaining the pervious nature of the grassed
surface.
There are volumes of information available on the internet on pervious pavement options and
many more products than are summarized above. The main point in discussing these systems in
this Plan is to raise the awareness of these alternative pavements and to encourage developers
and City decision makers to challenge designers to take a real look at the applicability to their
projects. These systems are not without concerns, especially in colder climates with extensive
freeze-thaw cycles and heavy applications of sand, and the systems tend to be more expensive to
install and maintain compared to conventional pavements. The challenge in determining their
cost-effectiveness overall is to also consider the cost savings that may be realized in offsetting
some of the other storm water BMP costs (e.g., land acquisition for a NURP pond). Therefore,
like any storm water BMP, selection of porous pavement for a project site needs to be considered
from many perspectives, but is an option that will likely continue to gain momentum.
2.TH 212 – Anticipated Impacts on Water Resources
The Minnesota Department of Transportation (MnDOT) is currently constructing the new
alignment of Highway 212 through the City of Chanhassen. The purpose of the project is to
increase capacity, decrease congestion, and improve traffic safety. The project includes
construction of a 4-lane highway and includes construction of several bridges, interchanges, and
overpasses throughout the project alignment. Impacts to water resources include wetland impacts
and mitigation projects, and construction of storm water ponds to treat the storm water runoff
from the roadway project.
E.Public Utilities
Public utilities within the City include sanitary sewer, water supply system and storm sewer. The
City currently operates 9 wells, 4 storage tanks, and 30 lift stations, and the system consists of
over 122 miles of water main and over 110 miles of sanitary sewer trunk lines. The City is in the
process of constructing a Water Treatment Plant, which will provide mineral treatment to water.
Sanitary sewer and municipal water is available to approximately two-thirds of the City.
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Currently there are approximately 350 individual sewage treatment systems (ISTS) within the
City limits.
Chanhassen’s drainage system includes storm sewer, open channels, storm water ponds,
wetlands, creeks and lakes. A significant portion of the City’s drainage system consists of storm
sewer. Construction of new storm sewer and improvement of existing storm sewer throughout
the City is primarily controlled by new development and street maintenance or reconstruction
activities. The storm water system is discussed in more detail in Section III of this Plan.
As part of this project, the City's existing storm sewer system database has been updated. The
update results in a GIS-based version of much of the storm sewer system based on a field
inventory of the existing storm water infrastructure. The inventory includes survey-grade GPS
location and elevation data for the vast majority of storm water infrastructure located on City-
owned and privately-owned land in Chanhassen. Ultimately, these files will form the foundation
for complying with the inspection, maintenance and reporting requirements for the National
Pollutant Discharge Elimination System (NPDES) Phase II storm water permit program
discussed in Section III of this Plan. These data will also serve to improve the City’s abilities and
efficiencies in reviewing development projects.
F.Water-Based Recreation Areas
As mentioned previously, the City has 12 lakes (7 recreational development lakes, 5 natural
environment lakes), 4 creeks, and 356 wetlands. These diverse water features provide aesthetic,
environmental and recreational value to the community. Several parks located on or near these
recreational waters provide boat ramps, fishing access and/or swimming beaches, along with
trails and picnic areas. Table 4 summarizes the water-based recreational facilities at these
locations. Figure 6 shows the locations of the DNR protected waters in Chanhassen. Section V of
this Plan includes a summary of the inventoried wetlands throughout the City based on the
Minnesota Routine Assessment Method, version 3.0. Wetlands provide habitat for several
wildlife species and thus provide aesthetic and recreational value.
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Table 4. Summary of Water-Based Recreational Facilities
Trails or
Lake Park or Area Boat Fishing Swimming Picnic
Ramp Access Beach Areas
Ann Lake Ann Park
● ●●●
Christmas ●
Lotus Carver Beach Park
●●●
North Lotus Lake Park
●
South Lotus Lake Park
●● ●
Lucy
Minnewashta Roundhouse Park
● ● ●
Lake Minnewashta Regional Park
●●●●
Riley Riley Lake Park
● ● ● ●
(Eden Prairie)
St. Joe
●
Susan Lake Susan Park
●●●●
G.Unique Features and Scenic Areas
The following paragraphs summarize three unique water and natural resource features within
Chanhassen. Additional information on each of these and other resources is provided in
Section IV.
1.Assumption Creek
Assumption Creek is a designated Trout Stream within the City of Chanhassen. The City
recognizes how important it is to protect this unique and special resource and the standards of
this Plan support that goal. In addition, the NPDES Construction Storm Water Permit and the
City’s MS4 Permit have provisions that require additional measures to be implemented by
development projects in the watershed.
2.Seminary Fen
The Seminary Fen is a calcareous fen located in the southern portion of Chanhassen. There are
approximately 112 acres of calcareous seepage fen in this area with rare and threatened plant
species. Preserving and protecting this resource is at the top of the City’s wetland protection and
preservation policies. The Seminary Fen is also listed in Minnesota Rules, Chapter 7050 as an
Outstanding Resource Value Water. As such, the NPDES Construction Storm Water Permit and
the City’s MS4 Permit have provisions that require additional measures to be implemented by
development projects in the watershed.
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3.Bluff Creek
Bluff Creek runs southeast of Lake Minnewashta and discharges into Rice Lake and the
Minnesota River. The City completed a management plan for the Bluff Creek Corridor in order
to develop guidelines and goals on how to preserve and protect the Bluff Creek Watershed
before development occurs. The watershed is currently in a state of transition due to the City’s
rapid growth and development, and the Bluff Creek Watershed Natural Resources Management
Plan identifies significant natural features along the Bluff Creek Corridor.
In 1998, the City adopted Article XXXI, Chapter 20 of its City code entitled “Bluff Creek
Overlay District.” This article serves to implement the regulatory recommendations set forth in
the management plan, including primary corridor preservation and grading and structural
setbacks from the primary corridor. These regulations are the foundation for the preservation of
Bluff Creek as a water resource, a continuous habitat corridor and a vital component of the
City’s urban forestry resources.
In order to further realize the natural resources recommendations in the plan, the City petitioned
the Riley-Purgatory-Bluff Creek Watershed District to undertake a basic water management
project in 1997. The City’s main goal is for Bluff Creek to be de-listed as an impaired water. The
City will continue to work with the RBPCWD to manage Bluff Creek.
H.Pollutant Sources
The City of Chanhassen does not have any landfills, dumps, hazardous sites, or feedlots within
its boundaries. Information on pollutant sources is available from the MPCA (651.296.6300).
This detailed information has not been included here as it is subject to frequent change and may
be obtained by calling the MPCA or by visiting the MPCA’s website (www.pca.state.mn.us)
which has information on various pollutant sources and related regulatory programs. The MPCA
will identify leaking underground storage tank (LUST) sites and maintain a list of registered
above and underground storage tanks (ASTs and USTs) within the City. The MPCA also has
information on permitted wastewater discharges and hazardous waste sites. Carver County has
information on abandoned wells within the City of Chanhassen.
Some additional pollutant source information may also be available from Carver and Hennepin
Counties. Counties maintain maps and databases that display MPCA-reported LUSTs, MPCA-
reported spills, MPCA-registered ASTs and USTs.
I.Groundwater Resource Data
According to the RPBCWD Water Management Plan, the groundwater system is comprised of
the glacial drift water table and the underlying bedrock aquifers which are partially in artesian
condition, meaning water in the bedrock is maintained under pressure by confining upper layers.
In many places, the Jordan Formation is a source of water to Riley, Purgatory and Bluff Creeks.
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J.Fish and Wildlife Habitat
As Identified in Section II (Background, History, and Physical Environment) Part G (Unique
Features and Scenic Areas) The City of Chanhassen has adopted a Bluff Creek Natural
Resources Management Plan to address the specific concerns of development along the creek
corridor and bluff areas. There is also a Bluff Creek Overlay District, which would protect
critical wildlife corridors and habitat. Section 5 (Wetlands), Part D (Functions and Values
Assessment) of the SWMP also includes a brief description of the critical resource areas that
would be identified as outstanding fish and wildlife habitat. These sources include Seminary fen,
Raguet Wildlife Management Area, Minnesota Valley Wildlife Refuge, and Assumption Creek.
This section also discusses the results of the County Biological Survey completed for Carver,
Hennepin, and Scott Counties, and the concentration of critical habitat, both upland and wetland,
along the Minnesota River bluffs, and the occurrence of the least darter in Lake Minnewashta.
The MCWD has identified wetlands along the eastern side of Lake Minnewashta as exceptional
or high aesthetic value and exceptional or high wildlife habitat.
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III.GOALS AND POLICIES
Minnesota Rules, Part 8410.0170, subpart 5 (italics below), relating to Surface Water
Management, requires local governments to establish goals and policies for the effective
management of water resources. The seven goals established in this Plan support the City’s
Purpose Statement by translating each goal into specific policies and ultimately standards that
are realized through the implementation plan. As a reference point for the basis of these goals
and policies, the following italicized text is from Minnesota Rules.
M.R. 8410.0170, Subpart 5. Establishment of policies and goals (Local Plans).
Each local (SWMP) plan must state specific goals and corresponding policies
related to the purpose of these plans, be consistent with the policies and goals of
the organization plans within the City or township, and address the relation of the
local plan to the regional, state, and federal goals and programs outlined in
Part 8410.0070.
goal
A is a desired end toward which surface water management efforts are directed. This
section identifies goals for water resources planning and management functions throughout the
City. The goals of this plan were established in accordance with the purposes of the water
management programs required by Sections 103B.201 to 103B.251 and in conformance with the
goals of the WMOs having jurisdiction in Chanhassen, including the MCWD, RPBCWD, the
LMRWD and the CCWMO. Table 5 summarizes the City’s seven goals and corresponding goal
statements.
policies
Each goal has several corresponding that form the governing principals that will be
followed to achieve the goals. The seven goals and the corresponding policies is presented in
standards
more detail in the following pages. Plan (or storm water Development Criteria) are an
extension of the goals and policies that provide detailed criteria on storm water management
practices. Recommended surface water management design standards for development and
redevelopment projects are provided in Appendix D of this Plan.
Implementation Plans
have been developed for each of the seven goals which present identified
or potential problems related to achieving the stated goals and recommended approaches and/or
solutions for addressing the problems.
The Implementation Plans may include specific activity steps, references to the applicable
NPDES Permit Best Management Practice (BMP), available resources, the means of measuring
the completion of the activity step and a target date for completion. The combination of these
implementation plans will formulate the overall strategy for implementing the City’s second
generation Surface Water Management Plan. Some of the action-implementation activities
correspond directly to actions committed to in the City’s NPDES Permit submittal, known as the
Storm Water Pollution Prevention Program (SWPPP).
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Table 5. Plan Goals and Goal Statements
Goal
Goal Goal Statement
Number
Water Quantity Provide at least 100-year (1% chance) flood protection for all persons and
1
structures.
Water Quality Achieve water quality standards in lakes, streams, and wetlands consistent
2
with their designated uses and established classifications.
Wetlands Protect and rehabilitate wetlands to maintain or improve their function and
3
value.
Erosion and Minimize soil erosion and sedimentation.
4
Sediment Control
Financing Establish and maintain funding sources to finance surface water
5
management activities.
Regulatory Maintain primary responsibility for managing water resources at the local
6
level but continue coordination and cooperation with other agencies and
Responsibility
organizations.
Public Education and Provide information and educational resources to improve knowledge and
7
Information promote an active public role in management of water resources.
A.Goal 1: Water Quantity
Development and the related changes in land use can increase runoff rates and volumes due to
additional impervious surface. As areas develop or redevelop at a higher density, storm water
runoff generally increases. This increase in runoff rates and volumes can cause flooding issues in
the downstream system. It is important to control these increased runoff rates and volumes in
order to ensure reduction of flooding in the downstream system and to control the potential
effects of erosive flows on streams and waterways.
A relatively new issue has recently gained much more attention over the past two years for 30
selected municipalities due, in large part, to the revised NPDES MS4 Permit. While runoff
volume has been regulated in many areas of Minnesota, and the country as a whole, the new non-
degradation requirements of the revised NPDES permit may create the need for stricter controls
in many communities, including Chanhassen. The non-degradation portion of the permit will
require Chanhassen to assess the change in loading of three pollutants (runoff volume, total
suspended solids, total phosphorus) over two time periods (approximately 1988 to 2000 and
2000 to 2020). The intent of these requirements is for the cities to develop a plan to address any
significant increased loading of one or more of the three pollutants. At this time, it is too early to
tell what additional long-term implementation efforts this will require of the City.
The City experienced two large storm events in the fall of 2005. The first storm occurred on
September 3 and 4 and was on order of a “100-year” event, totaling approximately 5.55 inches of
rainfall. The second occurred on October 4 and 5, 2005, and totaled approximately 4.61 inches of
rainfall. The good news is that overall the City’s storm water system worked well and was able
to handle the large storm events. However, there were a few exceptions. While significant
damages did not occur, a few areas were subject to high water levels and short-term flooding of
streets. Lotus Lake experienced extended high water levels. Residents of the lake experienced
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submerged docks and users were subject to the City’s emergency slow/no-wake restrictions for a
period of about 15 days. Looking at opportunities to reduce the extent and/or duration of these
high water levels is one of the key water quantity issues for the City. Because the lake discharges
to Purgatory Creek, the solution is not a simple one. Coordination with RPBCWD, Lotus Lake
area residents and the potentially impacted property owners downstream will be a critical step in
developing a long term solution that does not push the problem downstream.
Another issue that was discovered during the large event of 2005 is the lack of emergency
overflows and flow paths in some areas of the City. Ultimately, the City’s focus is to operate and
maintain the system so that it continues to function in the way it is intended, and provides flood
protection for adjacent properties. During review of storm water management plans it is
important for City staff to review the location of emergency overflow paths for storm water
infrastructure in new developments.
The City has developed the water quantity policies listed in Table 6 to support the water quantity
goals of this Plan.
Table 6. Water Quantity Policies
Goal Statement: Provide at least 100-year (1% chance) flood protection for all persons and
structures.
Policy No. Goal 1. Water Quantity – Policies
1 Establish building elevations to provide at least 3 feet of freeboard adjacent to ponding
areas and floodplains as an area develops or when drainage facilities are constructed for an
area.
2 Establish and maintain overflow routes for ponds and low areas to provide relief during
storm conditions that exceed design conditions.
3 Design, operate and maintain newly constructed storm water facilities in accordance with
this Plan.
4 Where possible, regional ponding areas, as opposed to individual on-site ponds, should be
used to reduce flooding, to control discharge rates, and to provide necessary storage
volumes as indicated in this Plan.
5 As opportunities allow through development, redevelopment, and infrastructure
replacement, stormwater facilities should be built or upgraded to provide or improve flood
management and water quality.
6 Encourage the development of new and improvement of existing ponds located upstream
of priority water bodies.
7 Permanently protect surface water impoundments and drainage systems by requiring the
dedication of land and/or protective easements as required.
8 Creative and innovative Best Management Practices, including infiltration systems will be
encouraged considering site limitations such as soil conditions, depth to groundwater,
safety, snow removal, and maintenance issues.
9 Continue to stringently enforce impervious surface requirements set forth in City Code
and development contracts.
10 Require all developments to construct nutrient detention ponds, enlarge regional ponds,
and/or contribute to the construction or improvement of a regional facility for the purpose
of reducing peak flows generated by the subject development, in accordance with
Minnesota Statute 462.358, and in the general location indicated by the Surface Water
Management Plan.
11 Preserve existing water storage below 100-year flood elevations.
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An effective Flood Insurance Study (FIS) dated January 1979 was completed for the City of
Chanhassen. As part of the FIS, Flood Insurance Rate Maps and Flood boundary and Floodway
Maps were created for the City, and are available from the FEMA website, www.fema.gov.
Flood profiles for the Riley, Purgatory and Bluff Creeks are provided in Appendix E.
1.Hydrologic Modeling Update
One of the larger tasks involved in the SWMP update was to update the City-wide hydrologic
model. The 1994 HydroCAD Model was updated from the DOS-based version available in 1994
to Version 7.0, which is a more rigorous and versatile program that will provide City staff a
better tool for evaluating proposed projects. One of the goals of this modeling effort was to
improve the City’s ability to predict and understand the urban hydrology and to evaluate
potential future flooding issues resulting from development or redevelopment projects. This
model update was created based on the 2020 Land Use Plan, soil hydrologic group data and
drainage area characteristics. A digital terrain model (DTM), consisting of two-foot contours and
GIS, was used to delineate watershed boundaries and identify detention/storage areas.
The watershed boundaries were compared with the subwatershed mapping from the 1994 Plan,
the storm sewer structure survey, and the wetland inventory to ensure the boundaries are as
accurate as possible for this planning-level analysis. Once the final watershed boundaries were
established, this file was merged with the hydrologic soil group and future land use files. Curve
numbers were generated using automated GIS procedures, and a weighted curve number was
calculated for each drainage area. The updated curve numbers were compared to the original
values to ensure they were logical and were revised as reasonable. Figure 2 (foldout map with
individual drainage areas shown) illustrates the drainage network that forms the basis for the
City-wide hydrologic model.
For the watersheds that were not altered significantly from the 1994 Plan boundaries, the time of
concentration was not altered. For altered or new subwatersheds a new time of concentration was
determined. Proposed ponds presented in the 1994 Plan were left in the model if the field work
and/or aerial photography review confirmed the pond was constructed. Proposed ponds that were
not constructed or observed in the field, but remain as implementation recommendations as part
of this SWMP update, were left in the model as an unconnected node. If stage storage-data were
available in as-built plans for new ponds, the data was included in the updated model. In many
cases the data available consisted only of a pond surface area, a normal water elevation and an
outlet pipe size. In general, the most recent and best available data was entered into the updated
HydroCAD Model. The model will be continuously updated by the City as new and better data
becomes available.
Modeling was completed for the critical duration storm events including the 2-year, 10-year, and
100-year, 24-hour NRCS Type II storm events with Antecedent Moisture Condition (AMC) 2. In
addition to the updated boundaries and input parameters, information relating to lake, wetland
and pond outlet conditions were also reviewed to develop a model that better represents the
current condition of the drainage system. Several storm water ponds were also inventoried as
part of the wetland inventory. The information available for these ponds in as-built plans was
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added to the HydroCAD model. In many cases the data provided in the as-built plans was limited
to surface area and normal water level information. Therefore the model does not include stage-
storage data for all storm ponds.
There are several natural conveyances within the City, including the 5 streams discussed in this
Plan. These streams are modeled as ponds or reaches in the HydroCAD model, since most
streams are conveyed through wetlands that provide additional storage volume. Other more
detailed hydrologic and hydraulic models are available for some of the natural conveyances
within the City.
The hydrologic modeling results for the 2-year, 10-year, and 100-year events were compared to
and evaluated against the data from the 1994 Plan. Results of this model were used to form
recommendations on system improvements and development standards. The updated HydroCAD
model will be used primarily for planning and development review efforts, and is not intended to
be used for design purposes without further refinement of the drainage area and pond data. The
modeling results for these storm events are provided in Appendix E. It is important to note that
the 100-year modeling data was not developed to the level of detail required in a flood insurance
study. Therefore, the data tables also include the regulatory flood elevation as defined in the
most recent flood insurance study for the City. As part of the review of potential updates to the
flood maps, it was determined that the mapping is generally accurate and updates to the detailed
hydrologic studies are not warranted at this time.
MCWD has identified four subwatersheds with land-locked basins located partially within the
City of Chanhassen. The MCWD requires these basins to continue to be managed as land-locked
basins.
Nine neighborhood areas located within Chanhassen were studied further for opportunities to
improve storm water quantity and quality with proposed street reconstruction projects. The
neighborhoods that were analyzed are illustrated in Figure 8 and a summary Technical
Memoranda and supporting computations for each completed study are provided in Appendix G.
2.Implementation Plan
Table 7 outlines activity steps intended to guide the City in achieving the water quantity goals of
this Plan. Table 7 also shows a list of possible resources available, the measurement system and
a project target date or schedule for each of the planned activities.
In general, the recommended activities and projects are to continue to review completed and
proposed development projects and look for opportunities to improve maintenance and operation
of the conveyance systems. In the process, some of the water quantity improvements will also
have a positive impact on water quality. For example, if by initiating a project that will establish
or improve the emergency overflow from a pond, the City may combine those efforts with
expanding the pond or conducting removal of accumulated sediment. These efforts would be
coordinated, in part, based on the (classification) priority system established for each lake or
surface water’s watershed. At the same time, the City would evaluate the existence of a drainage
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easement and initiate establishment of an easement if none currently exists. These efforts would
relate specifically to Activities 3 and 4 in Table 7.
Specific recommendations also relate to fixing identified current problems with the conveyance
system. Both of the recommended projects (Activities 1 and 5) will involve coordination with the
watershed district to evaluate the downstream impacts and to coordinate the compatibility of
potential improvements with other plans and regulatory requirements. These projects would first
involve completion of more detailed feasibility studies to determine the potential benefits and a
planning-level opinion of the costs of the improvements. A critical aspect of the feasibility is,
once a beneficial project is refined, a consideration of the funding sources must be included.
Therefore, the planning-level costs for these items in the Implementation section of this Plan
address only the costs the City would incur in participating in the feasibility studies. Additional
costs may be incurred by the City in any project design or construction stages.
Table 7. Water Quantity Implementation Plan
ID Activity / Project Resources Measurement Schedule
Review of proposed BMPs installed for
1 Explore opportunities for Ongoing
discharge rate reductions or development projects additional detention
hydrograph modifications in
Hydrologic / hydraulic Reduction in peak
the Bluff Creek System.
and/or duration of
models
erosive flows
Analysis of downstream
Reduction in bank
impacts
erosion
City-wide model Improved system
2 Refine City-wide hydrologic Ongoing
model as proposed projects model (each
Engineering Dept. staff
are completed project)
Developer’s plans and
modeling submittals
Property records GIS evaluation of
3 Review easement coverage 2008
on City owned and ponds / parcels
GIS data / parcel coverage
(Ongoing)
maintained storm systems
Dedicated easements
Property owners
relative to the 100-year HWL
over ponds to the
100-year HWL
Example agreement in Reduction of
4 Initiate Private System 2007
Appendix D of this plan localized flooding
Maintenance Program
Ongoing
“www” access to O&M Improved water
quality treatment
requirements
efficiency
City inspection and
maintenance staff
City-wide model Completed Study
5 Complete Feasibility Study 2007
to evaluate potential
XP-SWMM model if Identified
reductions of extended high
opportunities for
needed
water levels on Lotus Lake
volume and water
Coordinate with
quality benefits
watershed district efforts
Activity 2 is primarily needed to continue to refine the City tools for surface water management
and to comply with the City’s NPDES MS4 permit program. The permit does not require a
model to be established, but it does require an understanding of the City’s storm water “system”.
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The expectation is that both the new storm sewer and pond areas will be added to the GIS
database and City-wide hydrologic model for new development and verified and updated for
existing developments as new data is collected.
Activity 4 is needed for special circumstance within the City where BMPs will be maintained by
a private entity. The City owns and maintains the majority of the City’s storm water system, but
in areas where this will not be the case, private system maintenance agreements should be in
place. An example agreement is included in Appendix D of this Plan.
B.Goal 2: Water Quality
The City of Chanhassen seeks to maintain and improve the water quality in its lakes, streams and
wetlands. Water quality is often directly related to the level of available nutrients in a water
body. While nutrients comprise only one category of substances that can affect water quality,
nutrients (principally phosphorous) must be controlled to achieve the water quality goals of this
Plan. Phosphorous is most often the limiting factor for plant growth, and increases in available
phosphorous allow plant species to dominate the lakeshore, open water, or marsh. Two of the
City’s lakes are currently listed as impaired for nutrients (Lake Riley and Lotus Lake), and
phosphorous is the key nutrient responsible for this listing.
There are several key activities that can be followed to minimize the delivery of phosphorus into
these listed waters and all of the City’s water bodies. These activities include better management
of construction site erosion control measures, reducing the level of impervious cover, reducing
the extent of managed lawn areas and replacing them with native vegetation, reducing stream
bank erosion and using more open channel drainage systems with natural vegetative cover.
An assessment of the overall quality of the lakes and water resources in the City was completed
as part of this planning process. The results of this review indicate that the City’s lakes are
generally in very good condition with steady to improving trends. There are a few exceptions
that are discussed in more detail in Section IV of this Plan. In addition to focusing efforts on
improving the few waters that are impaired, a number of activities can be accomplished on a
routine basis to improve the quality of all City waters.
Housekeeping practices, such as removing leaves from streets and storm drains and limiting the
use of phosphorus fertilizers, are examples of simple ways individuals (residents) and the City
can make improvements in water quality. Many people do not realize that organic materials, like
leaves and grass clippings, fertilizer and pet waste can disrupt the ecosystem of a lake. Once in
the lakes these organic materials decay, releasing phosphorus. Excess phosphorus increases algae
growth, inhibiting the growth of other aquatic plants. When algae die and decay, they exert a
biological oxygen demand on the lake, depleting available oxygen for fish and other aquatic
species. Limiting nutrients is one of the keys to maintaining or improving water quality.
Turbidity is another concern that is caused by pollutants such as total suspended solids (TSS).
According to the MPCA, elevated turbidity reduces the depth of photosynthesis and the feeding
ability of aquatic organisms. Riley and Bluff Creeks are both impaired for turbidity, and
therefore sediment deposits into these creeks needs to be addressed.
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As discussed in the water quantity section, a relatively new issue has recently gained much more
attention over the past two years for 30 selected municipalities due, in large part, to the revised
NPDES MS4 Permit. The new non-degradation requirements of the revised NPDES permit may
create the need for stricter controls in many communities, including Chanhassen. The non-
degradation portion of the permit will require Chanhassen to assess the change in loading of
three pollutants (runoff volume, total suspended solids, total phosphorus) over two time periods
(approximately 1988 to 2000 and 2000 to 2020). The intent of these requirements is for the cities
to develop a plan to address any increased loading of one or more of the three pollutants. At this
time, it is too early to tell what additional long-term implementation efforts this will require of
the City.
The City has developed the water quality policies listed in Table 8 to support the water quality
goals of this Plan.
Table 8. Water Quality Policies
Goal Statement: Achieve water quality standards in lakes, streams, and wetlands consistent with
their designated use and established classifications.
Policy No. Goal 2. Water Quality – Policies
1 Categorize and manage each water body in the City’s surface water system to best meet
state, local, and federal water quality standards.
2 Establish and implement on-going programs designed to educate land owners in sensitive
water quality management practices and develop and maintain a public education program
to promote reduction of nutrient and sediment loading to water bodies.
3 Continue to monitor long term water quality trends on prioritized water bodies.
4 Focus management activities and capital improvements based on the priority ranking
scheme included in this Plan. Update priorities annually with a 5 year horizon.
5 Evaluate the progress of the surface water management program on an annual basis in
conjunction with the annual City Council Report/NPDES MS4 annual report.
6 The City may require higher water quality standards in areas identified as Preserve or
Improve 1 subwatersheds.
7 The City will lead by example by following the standards of this Plan and encouraging
BMPs to provide pollution prevention and water quality treatment on City-initiated
projects.
8 The City will encourage residents and landowners to practice environmentally friendly
lawn care and housekeeping practices, and to use native planting or natural landscapes
rather than turf lawns, where appropriate.
9 Prohibit the discharge of foreign material into the storm water system. Such material
should include, but not be limited to, waste oil, paint, grass clippings, leaves, commercial
fertilizers, trash, construction debris, and miscellaneous chemicals.
10 Develop and implement a spill response program for the City personnel to prevent
discharge of spilled materials into the storm sewer system. The response program should
focus on containing, neutralizing, and properly disposing of spilled materials. The Fire
Department, Public Safety Department, and Public Works Department should have a
readily available supply of response material including oil absorbing pads.
11 Require owners of development or redevelopment projects to provide on-site treatment or
contribute to the construction or improvement of a regional facility.
12 Continue to implement the erosion and sediment control policies and the construction site
inspection program to ensure reduction of water quality impacts from lack of erosion and
sediment control.
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1.Water Quality Information
The City of Chanhassen requires new developments to construct storm water ponds that provide
rate control and water quality treatment. The design standard for the storm water quality
treatment is to meet removal efficiencies for total phosphorus (TP) and total suspended solids
(TSS), as they relate to the Nationwide Urban Runoff Program (NURP) study that was
completed by the Environmental Protection Agency (EPA). Removal efficiencies of at least 60%
for TP and 90% for TSS are the criteria the City requires for all projects, which is the same as the
criteria in the 1994 SWMP. The standards in Appendix D of this Plan require water quality
modeling or computations to be submitted with the grading permit to support the stated removal
efficiency.
The water bodies in the City are assigned a management classification for water quality
treatment requirements. This management class designation is based on the water quality trends
of the receiving water, along with its current designated use and if it is on the TMDL List of
Impaired Waters. Development in watersheds that discharge to “Preserve” or “Improve-1” class
water bodies may be required to provide water quality treatment beyond the baseline NURP
levels established in the City development standards. This enhanced treatment requirement will
be implemented by staff on a project specific basis and may include, for example, establishment
of multi-cell treatment systems or infiltration/filtration BMPs to better treat the smaller “water
quality” storms. Section IV of the Plan explains the management classification system and water
quality trends of the water bodies in more detail
Nine neighborhood areas located with Chanhassen were studied further for opportunities to
improve storm water quantity and quality with proposed street reconstruction projects. The
neighborhoods that were analyzed are illustrated in Figure 8, and a summary Technical
Memoranda and supporting computations for each completed study are provided in Appendix G.
At the time of this Plan approval, one study has been completed; the intent is for the City to
insert the remaining studies into the Appendix upon completion.
2.Implementation Plan
Table 9 outlines activity steps that are intended to guide the City in achieving the water quality
goals of this Plan. Table 9 also shows a list of possible resources available, the measurement
system and a project target date or schedule for each of the planned activities.
While many activities in this Plan are focused on maintaining or improving water quality, the
recommendations in Table 9 focus primarily on the activities and projects that will restore,
expand or create new treatment capacity throughout the City. These efforts will help comply
with regulatory requirements of the NPDES program (e.g., including the future non-degradation
assessment and implementation activities). More importantly, the projects will help to maintain
the existing water quality trends and/or improve the water quality of receiving waters. For the
most part, specifically Activities 1, 2, 4 and 5, will support this goal on a long-term basis to help
the general public and developers better understand and support the need for water quality
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improvements, and to monitor the water quality trends to evaluate the progress to achieving the
goals of this Plan.
Table 9. Water Quality Implementation Plan
ID Activity / Project Resources Measurement Schedule
NPDES SWPPP Education events
1 Continue Education program Ongoing
as part of the City’s NPDES
Water Resources
Permit program SWPPP
Coordinator
Watershed Organizations
City staff inspectors Measurable goals
2 Coordinate BMP Ongoing
maintenance program with from NPDES SWPPP
Maintenance staff
NPDES SWPPP and private
BMPs maintained
Private system
system maintenance
maintenance program in
Materials removed
program.
Table 7, ID 4.
Review of proposed BMPs installed
3 Explore opportunities for Ongoing
water quality improvement development projects
Improved water
projects. Focus on Riley and
City-wide hydrologic
clarity trends
(see pond
Lotus Lakes to jump start
model
Increased treatment
summary
anticipated TMDL results.
GIS database of storm
capacity
in App. I
Identify direct discharges (no
systems, ponds, wetlands
of this
treatment pond/system) to
Plan for
Street recon projects (see
priority water resources.
possible
Appendix G)
ponds)
Recommended pond data
in Appendix I.
MPCA Final Study
4 Participate in TMDL Studies Pending
Recommendations
for Riley and Lotus Lakes
Watershed Organizations
MPCA Citizen Monitoring Annual assessment of
5 Continue water quality Annually
data
monitoring programs on City
City staff
lakes and key resources
Management
Lake Management Plans
approach adjustments
and Studies
Study memorandums in Completed projects
6 Complete Neighborhood Varies
studies and implement Appendix G.
Treatment capacity
treatment BMPs
Street reconstruction
established
project plans
See Figure 8
2006 Plan standards in Completed ordinance
7 Update storm water 2006-
Appendix D update
management ordinance 2007
Local watershed standards
More specific projects, as listed in the resources column for Activity/Project 3 in Table 9, are
listed as recommended pond implementation projects in Appendix I. The table in Appendix I
lists all recommended storm water ponds from Table III-D1 in the 1994 Plan. The table in
Appendix I identifies whether or not a recommended pond from the 1994 Plan has been
constructed. The table also includes all new storm water ponds that were inventoried as part of
the most recent wetland inventory. Some of these new ponds were not listed in the 1994 Plan.
Appendix I also contains a planning-level cost estimate for each pond that has not been
constructed as of the date of this Plan. The intended process for implementing these
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recommended ponds (or alternative treatment systems) is to use the classification (priority)
system in selecting projects from the list. As stated previously in this Plan, if two project
opportunities were available, City staff would use the classification system as part of the decision
process to select which project(s) to implement.
Activity 6 in Table 9 addresses several areas in the City where the potential for establishing new
treatment capacity was evaluated and implemented. The areas are illustrated in Figure 8, and at
the time of this Plan update one project (i.e., the Yosemite Neighborhood) was being
implemented. The remaining areas will follow a similar process to evaluate the potential parcels
available in the areas, the feasibility of completing a range of water quality BMPs (ponds, sump
manholes, mechanical separators, bio-retention areas, etc.), and the anticipated costs of the
recommended BMPs.
C.Goal 3: Wetland Protection
The key to meeting the City’s wetland goals is the implementation of a wetland management
program. In Chanhassen, this program consists of the inventory information in Section V and the
current wetland ordinance in effect. More background and wetland inventory information is
discussed in Section V, and recommendations for an update to the City’s ordinance are provided
in Appendix K. This portion of the Plan provides only a summary of Section V and establishes
the overall goals and policies for wetland management in the City.
The policies listed in Table 10 will be used as the basis to achieve the City’s wetland goals. The
policies and strategies will apply to new development and redevelopment projects proposed
within the City. Any wetland habitat on property to be developed will be subject to these
management policies, as well as the rules and requirements of the Wetland Conservation Act.
Table 10. Wetland Protection Policies
Goal Statement: Protect and rehabilitate wetlands to maintain or improve their function
and value.
Policy No. Goal 3. Wetland Protection – Policies
1 Develop and maintain an official wetlands map that classifies wetlands by function and
value.
2 Adopt and keep current ordinances and standards designed to protect wetlands.
3 Wetland alteration, where allowed, should be the basis of “no net loss”. If wetland impacts
are unavoidable, they should be mitigated through replacement, wetland conversion,
and/or improvements to wetland function and value.
4 Adopt the storm water and water quality management practices designed to protect
wetland functions and values. Introduction of storm water runoff should be allowed only
when it is demonstrated that wetlands will not be adversely impacted.
5 Adopt an ordinance in compliance with the Minnesota Wetlands Conservation Act of
1991 for no net loss in quantity and quality of jurisdictional wetlands.
1.Wetland Management Program
The City of Chanhassen has developed a Wetland Management Plan as part of this plan update.
If the City pursues approval of the plan as a Comprehensive WMP, the plan would formally
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serve as an alternative to the rules adopted under Minnesota Statutes, section 103G.2242.
However, before this occurs, the plan would need to be approved by BWSR, be adopted by the
City and must require equal or greater standards and procedures as compared to the Wetland
Conservation Act (WCA). The benefits of a CWMP include a current functions and values
assessment for management and wetland ordinance development, greater flexibility in
sequencing and replacement standards for wetlands, and development and management of higher
quality wetlands within the City. The major disadvantage to finalizing the approval process at
this time is that the plan would not address all the requirements under the Corps of Engineers
regulations for wetlands. Essentially two separate sets of rules would still exist.
The Wetland Management Plan (Section V and Appendix G) includes an inventory, a functions
and values assessment, sequencing standards, replacement standards, a description of the size
and location of replacement wetlands, allowance of exemptions based on ordinance standards
and definitions of high priority wetlands. A Minnesota Routine Assessment Method Version 3.0
(MnRAM 3.0) was completed for each wetland located in the City. MnRAM assessments
identify wetland functions and values. These qualitative data provide a basis for management,
decision-making, and permitting for the inventoried wetlands. MnRAMs will also provide a base
reference for long-term monitoring and management of wetlands. The MCWD has also
completed a wetland inventory and functions and values assessment for the portion of the City
within the Minnehaha Creek watershed (Minnehaha Creek Routine Assessment Method for
Evaluating Wetland Functions, or McRAM). The City has agreed to use the McRAM results for
that portion of the city, although the more recent inventory will be used for evaluation and
comparison as needed. The City also addresses wetland buffers as part of the wetland
management planning process and has buffer requirements in their current wetland ordinance.
2.Implementation Plan
Table 11 outlines activity steps that are intended to guide the City in achieving the wetland goals
of this Plan. Table 11 also shows a list of possible resources available, the measurement system
and a project target date for each of the identified activities.
Table 11. Wetland Implementation Plan
ID Activity / Project Resources Measurement Schedule
2006 Inventory WMP project review
1 Implement the wetland Ongoing
management program
MnRAM, GIS Database Implemented projects
Section V of this Plan
Development reviews New wetland created
Development projects Maintained, updated
2 Update Wetland Inventory. Ongoing
Digitize created wetlands and database
MnRAM, McRAM, GIS
modify impacts per projects.
Database
2006 Inventory Completed ordinance
3 Update wetland management 2007
update
ordinance
Ordinance in Appendix K
D.Goal 4: Erosion and Sediment Control
The City addresses erosion and sediment control in its ordinances and its NPDES Phase II
SWPPP. The City partners with the Carver County Soil and Water Conservation District to
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implement its construction site erosion control inspection program. The policies listed in
Table 12 are intended to help the City achieve the erosion control goal of this Plan.
Table 12. Erosion and Sediment Control Policies
Goal Statement: Minimize soil erosion and sedimentation.
Policy No. Goal 4. Erosion and Sediment Control – Policies
1 Erosion and sediment control practices are necessary on all construction sites and on sites
experiencing erosion control problems.
2 Best Management Practices should be used at all construction sites per the Minnesota
Pollution Control Agency’s “Minnesota Urban Small Sites BMP Manual” (2001), the
Minnesota Pollution Control Agency’s “Protecting Water Quality in Urban Areas” (2000),
and/or the Minnesota Pollution Control Agency 2005 Storm Water Manual.
3 Disturbances to existing vegetation (trees, turf grass, native vegetation, etc.) should be
minimized.
4 The City will continue to work with the Carver County SWCD to inspect construction
sites for erosion and sediment control issues once every 2 weeks and after every 0.5-inch
rain event.
5 The City will maintain and educate the public on the Clean Water Hotline. This hotline is
used to report erosion and sediment control issues on sites, and to report any water quality
issues.
6 Graded areas should be protected using erosion and sediment control Best Management
Practices to reduce erosion in a manner consistent with the standards of this Plan. Streets
will be frequently swept where construction activities spill and or track sediments onto
streets. In areas undergoing construction activities, the cost of sweeping sediment from the
streets generated by development should be borne by the developer and/or home builder.
7 Stockpiled soil (and/or like-materials) should be protected to prevent erosion.
8 Effective energy dissipation devices should be provided at all conveyance system
discharge points to prevent bank, channel, or shoreline erosion. Design of stream bank
stabilization and streambed control measures should consider unique or special site
conditions, energy dissipation potential, adverse effects, preservation of natural processes
and aesthetics, in addition to standard engineering and economic criteria.
9 Update City Specifications annually to reflect current technology for erosion and sediment
control.
As discussed previously in Goal 2, water quality problems are frequently linked to high
phosphorus and total suspended solids concentrations. Phosphorus is often transported to surface
water through soil erosion, but can also be transported to waters in a variety of other
.
mechanismsNevertheless, erosion control is extremely important in the effort to improve water
quality. Soil erosion and sediment deposition also can create pond and drainageway performance
and maintenance problems.
Ponds, drainage facilities and water bodies can be impacted by erosion and sediment from a
variety of sources, including construction sites and winter street sanding operations. The coarse
sediment accumulates in water bodies where runoff or flow velocities are relatively low. Usually
a sand delta appears at a storm sewer outfall that is a visible indication of the effectiveness of
erosion and sediment control measures and the extent of road sanding activities of the past
winter. As sediment builds up over time, it reduces the capacity of drainage systems and the
pollutant removal capabilities of ponds by reducing dead storage volume (i.e., the volume below
the outlet elevation). Sediment from erosion also reduces infiltration rates in basins or BMPs
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designed for groundwater recharge. Extending the life of these facilities involves source control
and elimination of material that causes the problem, and maintenance of the systems on a regular
basis. Regulatory aspects will control a major portion of the sediment at the source, and an
effective street sweeping program will also have a positive impact.
The Lower Minnesota River Watershed District (LMRWD) Plan identified a bank erosion
problem adjacent to the LRT trail in the northeast quarter of Section 35 in Chanhassen. The City
will continue to monitor erosion issues at this site and throughout the City and address these
issues as necessary.
1.Implementation Plan
Table 13 outlines activity steps that are intended to guide the City in achieving the erosion and
sediment goals of this Plan. Table 13 also shows a list of possible resources available, the
measurement system and a project target date for each of the identified activities.
Table 13. Erosion and Sediment Control Implementation Plan
ID Activity / Project Resources Measurement Schedule
Development projects Implemented projects
1 Continue to implement the Ongoing
erosion and sediment control
Carver County
inspection program.
Watershed Organizations
Clean Water Hotline
Review of proposed BMPs installed
2 Explore opportunities for Ongoing
erosion protection and bank development projects
Reduction in bank
stabilization at key storm
City-wide hydrologic
erosion
system conveyances and
model
Reductions in gullies,
outlets
Analysis of peak rates on
washouts
downstream impacts
Implement new Improved compliance
3 Evaluate the need for Assess
technologies for
improving the efficiency and at construction sites need in
inspection tracking
effectiveness of the
2006
Reduced sediment
inspection program.
Dedicated staff to delivered to water
Program
supplement work of
bodies
Ongoing
Carver County staff
E.Goal 5: Financing
Paying for water management projects has become more complex in recent years. In the past,
special assessments against benefited properties financed most of the necessary improvements.
However, the financial options have broadened considerably. The City currently uses a storm
water utility program as a key component of their overall approach to fund storm water-related
projects. Section I.B of the Plan includes a summary of the state and federal rules, statutes and
agencies that drive the City to implement the recommendations set forth in this Plan, and in turn
implement financing goals and policies to fund the program. Table 14 lists the policies that are
intended to help the City achieve the financing goal of this Plan.
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Table 14. Financing Policies
Goal Statement: Establish and maintain funding sources to finance surface water management
activities.
Policy No. Goal 5. Financing Policies
1 Revise, implement, and maintain a financing strategy for surface water improvements
utilizing a combination of storm water utility fees, special assessments, surface water
management plan connection charges, and storm water program grant funds.
2 Require all new development to pay connection charges for water quality and water
quantity to finance downstream improvements to accommodate new developments.
3 Continue to collect storm water utility fees from all parcels within Chanhassen (exempting
public ROW and lakes), to reflect the service provided by the City for storm water
management and associated operational costs.
1.Implementation Plan
Table 15 outlines activity steps that are intended to guide the City in achieving the finance goals
of this Plan. Table 15 also shows a list of possible resources available, the measurement system
and a project target date for each of the planned activities.
Table 15. Financing Implementation Plan
ID Activity / Project Resources Measurement Schedule
Original Utility Study Completed study
1 Complete an assessment of 2006
trunk storm water and utility
Implemented changes
City staff
system fees needed to
to assessments and or
NPDES SWPPP
support the overall City
utility rates
requirements
water resources program.
Clean Water Hotline
MPCA Programs BMPs installed
2 Explore opportunities for Ongoing
grant program funding to
Water quality
Watershed Organizations
implement water resource
improvement,
Metropolitan Council
improvement projects
education and/or
demonstration
projects
F.Goal 6: Regulatory Responsibility
The City assumes the role of permitting all land alteration activities and enforcing the standards
and policies set forth by the Plan. Riley Purgatory Bluff Creek Watershed District (RPBCWD)
also reviews and permits on any proposed land alteration > 1 acre within the RPBCWD.
Minnehaha Creek Watershed District (MCWD) permits for projects that include land alteration,
floodplain alteration, dredging, shoreline and streambank improvement, and stream and lake
crossings. Lower Minnesota River Watershed District reviews alterations to land within the
Minnesota River valley. Carver County Water Management Organization reviews and permits
land altering projects in the WMO. The City is the LGU for the Wetland Conservation Act, and
assumes the role of permitting all wetland impacts.
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The Minnesota Department of Natural Resources has authority over issues relating to water and
wetlands designated as State Protected Wetlands and Waters. The U.S. Army Corps of
Engineers has authority relating to all wetlands identified by the U.S. Fish and Wildlife Service’s
National Wetland Inventory.
Carver County and the Minnesota Department of Health have regulatory authority over
groundwater issues within the City. Erosion control falls under several jurisdictions including the
City, the watershed districts, and the MPCA. The MPCA also has regulatory authority over
individual septic systems within the City limits.
The City has developed the policies in Table 16 to help ensure that the regulatory responsibility
goals of this Plan are clearly understood, met and addressed on an ongoing basis. The City
wishes to retain permitting authority for projects within the City in order to provide a consistent
permitting process for developers and residents. The City feels this is especially important since
there are four WMOs that have jurisdictional authority within the City limits, and each has their
own set of standards and guidelines. This situation becomes more complex when there is a larger
development that potentially straddles two different WMOs, with two different sets of rules to
follow.
Table 16. Regulatory Responsibility Policies
Goal Statement: Maintain primary responsibility for managing water resources at the local level but
continue coordination and cooperation with other agencies and organizations.
Policy No. Goal 6. Regulatory Responsiblity – Policies
1 Adopt policies consistent with local watershed authorities’ management plans.
2 This plan and all subsequent amendments will be consistent with the plans of regulatory
agencies.
3 This plan will be amended as necessary to remain current.
4 Coordinate projects and information with government agencies; i.e. MnDOT, Carver and
Hennepin Counties, Department of Natural Resources, Watershed Districts, and Water
Management Organizations.
1.NPDES Phase II SWPPP
The NPDES Phase II Permit Program (http://www.pca.state.mn.us/water/stormwater/index.html)
is a federal regulatory program that requires owners of Municipally Separate Storm Sewer
Systems (MS4s) to prepare and implement a Storm Water Pollution Prevention Program
(SWPPP), and apply for the permit with the administrative agency. The Minnesota Pollution
Control Agency administers the Phase II MS4 program in the state, and the City submitted their
permit application prior to March 10, 2003 to comply with the initial submittal deadline. This
SWMP incorporates some of the BMPs that were identified in the City’s SWPPP along with
several specific projects that were not specified as part of the Phase II program.
As discussed in the water quality and quantity goal sections, a relatively new issue has recently
gained much more attention over the past two years for 30 selected municipalities due, in large
part, to the revised NPDES MS4 Permit. The new non-degradation requirements of the revised
NPDES permit may create the need for stricter controls in many communities, including
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Chanhassen. The non-degradation portion of the permit will require Chanhassen to assess the
change in loading of three pollutants (runoff volume, total suspended solids, total phosphorus)
over two time periods (approximately 1988 to 2000 and 2000 to 2020). The intent of these
requirements is for the cities to develop a plan to address any increased loading of one or more of
the three pollutants. At this time, it is too early to tell what additional long-term implementation
efforts this will require of the City.
2.Implementation Plan
Table 17 outlines activity steps that are intended to guide the City in achieving the regulatory
responsibility goals of this Plan. Table 17 also shows a list of possible resources available, the
measurement system and a project target date for each of the identified activities.
Table 17. Regulatory Responsibility Implementation Plan
ID Activity / Project Resources Measurement Schedule
SWPPP and individual Annual Report and
1 Continue to implement the Annually
program assessment
City’s NPDES Permit BMPs
June 30
summary
program SWPPP.
Permit activity tracking
system
Adjacent MS4s
Minnehaha Creek Plan Plan updates as
2 Maintain consistency with Ongoing
needed
Watershed Management
Riley Purgatory Bluff
Organization Plan Goals and
Creek Plan
Policies
Carver County WMO Plan
Lower Minnesota River
Watershed District Plan
Current GIS data for Evaluate options
3 Establish electronic NPDES 2006
inspection and maintenance structures
System established
2007
program tracking and
Recommendations in
and fully functional
reporting system
Appendix J
Off-the-shelf software or
in-house system
The City encourages the WMO’s to take the lead in developing TMDL studies as they become
necessary. The City will continue to coordinate and cooperate with the WMO’s in this process.
G. Goal 7: Public Education and Participation
The public education and participation goal is a strategy that recognizes people want to be
involved in decisions that affect any facet of their life. The process of involving the public seeks
to create opportunities for the public to participate in the processes that lead to decision-making
and result in more public ownership in the outcome. The City has developed the public education
and participation policies listed in Table 18 to help achieve the goals of this Plan. Public
education and participation activities are also requirements of the National Pollutant Discharge
Elimination System (NPDES) Permit.
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Table 18. Public Education and Participation Policies
Goal Statement: Provide educational resources to improve knowledge and promote an active
public role in management of water resources.
Policy No. Goal 7: Public Education and Participation - Policies
1
The City will continue to provide opportunities for public involvement (e.g.,
neighborhood meetings, public hearings, mailed notices, etc.) for significant water
resource decisions or projects.
2
The City will coordinate and consult with the City Council and appropriate City
commissions and committees on surface water issues.
3
City will communicate with lake associations and other appropriate civic and citizen
groups.
4
The City will actively implement the current educational programs and work to
develop and implement new education programs and activities related to water
resources. This program will use a variety of media including use of notices, mailings,
local cable television, newsletters, articles, internet web sites, workshops and/or
presentations to inform and educate the public.
5
The City will cooperate with other agencies and encourage establishment of model
interpretative sites for public education like the storm water practices at the Landscape
Arboretum.
6
Continue to remain in compliance with the NPDES Phase II MS4 permit with respect
to public education and involvement.
1. Watershed District and County Programs
The watershed districts and Carver and Hennepin Counties currently have public education and
information activities efforts in their overall surface water programs. These agencies make this
information available to the City generally through their websites, but also on a case-by-case
basis for special programs or events available to the City or City residents to participate in. The
City will continue to seek out these education efforts to more effectively reach and inform
residents, businesses and City staff on the wide range of surface water management issues. The
City encourages the counties and watershed districts to devote more time and energy to
producing educational tools, such as brochures, videos, training sessions, newsletter articles, etc.,
that can be used by municipalities throughout their jurisdictions.
2. City Programs
The City has numerous lake associations and committees who focus on the interests and the
protection of the lakes and other water resources within the City limits. The City also has a
website where information regarding the City’s committees and commissions, their mission
statements and past agendas and meeting minutes are available. As part of the NPDES Phase II
MS4 Permit, the City has also posted their SWPPP on the website. As part of the NPDES
program, the City is required to implement a public education and outreach program, along with
a public participation and involvement program and to incorporate public information into each
of the other four minimum control measures of the permit.
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The City’s website is an alternative medium to provide municipal information to both City
residents and those people who live outside the City. An electronic version of the completed and
approved surface water management plan will ultimately be accessible on the web. Because the
Plan has such a wide audience, from engineers and planners to developers, citizens, scientists
and educators, electronic access to the text and mapping creates a better understanding of the
goals, policies and activities of this Plan.
The City will continue to distribute information on pertinent water and wetland management
issues via the Chanhassen Connection, its quarterly community newsletter, and will promote
opportunities for residents to participate in water resources management activities. The City will
also make ongoing efforts on both a City-wide and watershed level toward educating the public
by distributing information to its residents on responsible practices they should employ to protect
water resources within the community. The program will educate residents on things such as the
benefits of using phosphorus-free fertilizer and the proper use of a wide range of lawn chemicals.
3. Implementation Plan
Table 19 outlines activity steps intended to guide the City in achieving the public participation,
information and education goals of this Plan. Table 19 also shows a list of possible resources
available, the measurement system and a project target date for each of the planned activities.
Table 19. Public Participation, Information and Education Implementation Plan
ID Activity / Project Resources Measurement Schedule
SWPPP - BMPs Annual Report and
1 City Storm Water Program Annually
and Annual NPDES Permit program assessment Prior to
Adjacent MS4s
Public Meeting June 30
Public hearing held at
Public Input
City Council
Metro WaterShed Partners Resulting information
2 Remain involved in local Ongoing
distributed
educational campaigns
Watershed Districts
Metropolitan Council Annual results in
3 Recruit volunteers to Annually
report from
participate in the Citizen
City staff
Metropolitan Council
Assisted Monitoring
Program (CAMP) for lakes
Metro WaterShed Partners Articles placed in
4 Include water resources Quarterly;
articles in Chanhassen newsletter quarterly
Ongoing
Watershed Districts
Connection
City staff
Metro WaterShed Partners Updated info on
5 Provide water resources-Ongoing
website - water
related information on the
City staff
quality, current issues
City’s website
City staff Provide information
6 Continue to maintain Clean Ongoing
on current projects
Water Hotline
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IV.SURFACE WATER RESOURCES
A.Overview
The current condition of the majority of Chanhassen’s surface water resources is very good, with
lake quality trends showing general improvements in water quality. There are a few exceptions
to this trend, and the need to improve these waters and protect the quality of all City surface
waters is the primary basis of this Plan. To support the City’s goals to protect and improve water
quality, each water body has been assigned a management classification based on the use,
function and current water quality characteristics. This management classification system is
shown in Table 20 for all surface waters except wetlands, and is intended to help City staff in
managing the overall surface water management program. The classification system provides the
basis for establishment of treatment requirements for future development projects and
prioritizing opportunities to retrofit the existing City treatment system.
The basis for most water body designations is the Carlson Trophic State Index (TSI), which is a
measure of a lake’s trophic state. Trophic state is one way to measuring a lake’s productivity,
health and succession, and is designated as one of four categories ranging from Oligotrophic,
which is typically crystal clear and very nutrient poor, to hypereutrophic, which has excess
nutrients, and is frequently covered in thick vegetation and frequent algae blooms. Between these
two extremes are mesotrophic and eutrophic, which are the most common classifications for the
City’s lakes. Trophic state is usually determined by collecting water samples from the lake and
analyzing it for phosphorus concentration and chlorophyll a. Water clarity can also be measured
physically using a Secchi disk to determine how far light penetrates the surface. Each of these
values can be used to estimate a trophic state, although multiple samples are required to establish
an overall state and to track changes over time.
Total phosphorus and chlorophyll-a are measured in micrograms per liter (g/L), and Secchi disk
transparency is measured in meters (3.281 feet per meter). The TSI scale ranges from 0 (ultra-
oligotrophic) to 100 (hypereutrophic). High and/or increasing trophic status values indicate more
eutrophic conditions (higher productivity). The following values are indicative of the conditions
present for the range of TSI values possible
TSI < 30
Classical Oligotrophy: Clear water, oxygen throughout the year in the hypolimnion,
salmonid fisheries in deep lakes.
TSI 30 - 40
Deeper lakes still exhibit classical oligotrophy, but some shallower lakes will become
anoxic in the hypolimnion during the summer.
TSI 40 - 50
Water moderately clear, but increasing probability of anoxia in hypolimnion during
summer.
TSI 50 - 60
Lower boundary of classical eutrophy: Decreased transparency, anoxic hypolimnia
during the summer, macrophyte problems evident, warm-water fisheries only.
TSI 60 - 70
Dominance of blue-green algae, algal scums probable, extensive macrophyte problems.
TSI 70 - 80
Heavy algal blooms possible throughout the summer, dense macrophyte beds, but
extent limited by light penetration. Often would be classified as hypereutrophic.
TSI > 80
Algal scums, summer fish kills, few macrophytes, dominance of rough fish.
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The following is an example of the water quality monitoring data for Lake Minnewashta
compiled by the Minnesota Pollution Control Agency and presented on their website.
Major lakes in Chanhassen are classified in Table 20 as Management Class: Preserve;
Improve-1, Improve-2 or Improve-3 water bodies. Storm water ponds are classified as
Constructed. Table 20 also establishes a management strategy and storm water treatment level
for each class of water resources. Figure 7 shows the locations of these water resources and the
management class associated with each water feature. The management class is based on the
water quality trends, designated uses and regulatory status (i.e., EPA’s impaired waters list). For
example, Lakes Lotus and Riley are classified as ‘Improve-1’ because these two lakes both have
been identified as impaired due to excessive nutrients. There is not only a desire to improve the
water quality; there is also a regulatory need for improvement in these lakes. Other examples are
Lake Minnewashta and Lake Ann, which are classified as ‘Improve-2’ water bodies. Both of
these lakes have relatively high water quality and steady to improving trends. The City wishes to
continue the improving trends and will do so by continuing to manage the watershed to maintain
and improve the quality of these water bodies.
This section of the Plan is intended to describe the key water bodies within Chanhassen
according to their relative priority or management classification. Each water body or special
feature is presented in the following sections, along with a summary of the information collected
and analyzed for each water body to date, an assessment of any problems, and recommended
implementation activities.
The Minnesota Pollution Control Agency (MPCA) has also identified a number of Outstanding
Resource Value Waters (ORVW), requiring a higher level of protection (Minnesota Rules,
Chapter 7050). Discharge to ORVWs is more stringently regulated than the other waters in the
state because these waters have statewide significance or are unique and/or outstanding water
resources. For example, if a project discharges to a trout stream designated as an ORVW, more
stringent BMPs are required by the NPDES Construction Stormwater Permit and the City is
required to manage these waters differently as part of its NPDES MS4 SWPPP. In the case of
trout waters, the requirements include establishing BMPs that provide temperature control of the
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storm water prior to discharge to the trout water. The Seminary Fen and Assumption Creek are
both ORVWs.
Table 20. Water Management Classification for Chanhassen Water Features
Management Management Storm Water Water Use
Class Strategy Treatment Resource Designation
(3)(1)
Seminary Fen Calcareous Fen
NURP
Preserve and
Preserve
impose
improve,
Plus Enhanced
Assumption Trout Stream
highest standards
.
Treatment
Creek
Lotus LakeRecreational
Goal to improve
Improve - 1
Development
impose
trends,
NURP
higher standards.
Lake Riley Recreational
Plus Enhanced
These waters are
Development
Treatment
“impaired” see
Bluff Creek Natural Stream
Table 21 for details
.
(2)
Riley Creek Natural Stream
Lake Ann Recreational
Goal to maintain or
Improve - 2 NURP
Development
improve. Look for
opportunities to
Enhanced
Christmas Lake Recreational
apply higher
Treatment if
Development
standards
.
Opportunities
Lake Recreational
Present
Minnewashta Development
Lake Susan Recreational
Development
Goal to maintain
Harrison Lake Natural
water quality and
Improve - 3
Environment
keep long-term trends
Lake Lucy Recreational
NURP
stable to improving
Development
Rice Marsh Lake Natural
Environment
Silver Lake Natural
Environment
Lake St. Joe Natural
Environment
Storm Water Treatment
NA
NA
Constructed
Ponds System
(1)Use designation taken from the City’s Comprehensive Plan.
(2)TMDL list of impaired waters for nutrients (Riley and Lotus Lakes), Turbidity (Bluff and Riley Creeks), Fish IBI (Bluff Creek).
See Table 21 for additional information on TMDL listings including Mercury-impaired waters.
(3)Standards provided in Appendix D. NURP level is removal of 90% TSS, 60% TP. Enhanced treatment for one or more of the
following: higher level of TSS/TP removal, additional discharge rate controls and/or temperature controls.
Waters that are on the TMDL list of impaired waters for one or more pollutants are shown in
Table 21. One of the key considerations that is not fully addressed in this Plan is the waters listed
on the Draft 2006 TMDL List of Impaired Waters. The City understands that the TMDL process
is really just beginning and that the 2004 Final TMDL List of Impaired Waters (as required
under Section 303(d) of the Clean Water Act) is updated every two years.
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To date, approximately 8 percent of Minnesota’s river miles and 14 percent of Minnesota’s lakes
have been tested for pollution problems. Approximately 40 percent of those tested are polluted
with human and animal waste, phosphorus, suspended solids and mercury. As more of the states’
surface waters are tested for pollution problems, the state will continue to add surface waters to
the TMDL list. It is reasonable to assume that as more waters are assessed, then more waters will
be listed as impaired in subsequent biennial cycles. When studies are completed, the TMDLs will
likely be used by the MPCA and local entities to further prioritize management actions and
establish additional regulatory controls.
The City will consider the listing of the lakes in Table 21 in future management decisions and
actively manage the activities in the contributing watersheds to limit the delivery of these
pollutants (primarily nutrients and sediment) to these waters. The City’s approach to addressing
potential pollutant loadings to these waters will be to evaluate the opportunities for a level of
storm water “treatment” higher than the basic standards established in this Plan on a case-by-case
basis prior to completion of the TMDL study and associated implementation plan.
Table 21. TMDL Listed Impaired Waters in Chanhassen
Receiving Assessment ID Affected Pollutant
or Stressor
Water or DNR Lake # Use (1)
Lotus Lake 10-0006 Aquatic Recreation Excess Nutrients
Aquatic Consumption Mercury FCA
Riley Lake 10-0002 Aquatic Recreation Excess Nutrients
Aquatic Consumption Mercury FCA
Bluff Creek 07020012-510 Aquatic Life Fish IBI
Aquatic Life Turbidity
Riley Creek 07020012-511 Aquatic Life Turbidity
Lake Lucy 10-0007 Aquatic Consumption Mercury FCA
Lake Ann 10-0012 Aquatic Consumption Mercury FCA
Lake Susan 10-0013 Aquatic Consumption Mercury FCA
Christmas Lake 27-0137 Aquatic Consumption Mercury FCA
Lake Minnewashta 10-0009 Aquatic Consumption Mercury FCA
(1) FCA = Fish Consumption Advisory
According to the MPCA’s Draft Statewide Mercury TMDL Study, most of the mercury in
Minnesota’s fish comes from atmospheric deposition, with approximately 90 percent originating
from outside the state. Because mercury has regional TMDL implications, little effort will be
placed on TMDL recommendations related to mercury for these waters as part of this planning
effort. The City will continue to review recommendations for mercury that may be offered by
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EPA and/or MPCA to see if the regional approach to mercury has any future implications on the
City. More detail on the progress of the statewide mercury TMDL process can be found on the
MPCA’s website.
B.Lakes
1.Background and Previous Findings
Nine of the twelve lakes located entirely or partially within the City of Chanhassen were
discussed in the 1994 Surface Water Management Plan. The 1994 Plan described historic and
existing water quality, biological quality, lake and watershed quality conditions and trends. The
1994 Plan summarized existing data, and then recommended future studies and management
needs and objectives for each of the nine lakes and the community as related to these lakes.
Priorities and planning needs were established for each lake and included both short and long
term goals and objectives. The nine lakes addressed in the 1994 Plan were; Riley, Rice Marsh,
Susan, Ann, Lucy, Minnewashta, Lotus, Christmas, and St. Joe. The City’s Comprehensive Plan
lists two additional ‘natural environment’ lakes: Harrison Lake and Silver Lake. Rice Lake is
located in the southeast corner of the City, on the border of Chanhassen and Eden Prairie. These
three lakes were not evaluated in the ‘Lakes’ section of the 1994 Plan. Table 22 provides a
summary of the basic physical characteristic of each of the 12 lakes in Chanhassen.
The 1994 Plan defined and classified each lake according to the conditions and qualities that
were revealed through previous studies, lake monitoring, or through geospatial data
interpretations. Previous studies include aquatic vegetation surveys, lake water quality studies,
and lake management plans conducted for any of the nine referenced lakes. The 1994 Plan
utilized the Minnesota Department of Natural Resources (MNDNR) Ecological Classification
System to establish and model a baseline condition for future monitoring, lake management, and
restoration goals. The 1994 Plan then identified and prioritized monitoring and lake management
needs, goals, and objectives. These recommendations and priorities range widely in content for
the individual lakes, and include education, management, engineering, and biological based
topics.
This 2006 SWMP Update included a review of the 1994 Plan as well as a review of the studies
completed and the lake monitoring data available since 1994. The City participates in the Citizen
Assisted Monitoring Program (CAMP), and currently Lake St. Joe, Lotus Lake, Lake Susan, and
Riley Lake are monitored as part of this program. The Metropolitan Council monitors water
quality and level of Bluff Creek at the intersection of existing TH 212 and TH 101.
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Table 22. Lake Physical Characteristics
Lake
Max.
Surface Watershed 100-yr Lake Recreational
Lake NWL OHW
Depth
Area Area (ac) HWL Uses
(ft)
(ac)
Boating (electric
Ann 116 45 257 955.2 955.5 956.0 motors only), fishing,
and swimming,.
Boating, fishing and
Christmas 257 87 410 932.8
swimming.
Harrison (1) 993.6
Boating, fishing, and
Lotus 246 29 1,340 895.4 896.3 896.7
swimming.
Boating, fishing, and
Lucy 92 20 972 955.2 956.1 956.8
swimming
Boating, fishing and
Minnewashta 738 70 2,653 942.2 944.5 943.1
swimming.
Rice Marsh 79 11 934 874.8 877.0 876.62
Rice 699.2
Boating, fishing and
Riley 297 49 1,667 862.8 865.3 864.2
swimming.
Silver N/A 898.53 898.1
Boating, fishing and
Susan 93 17 1,330 881.4 881.8 885.5
swimming.
Boating, fishing and
St. Joe 14 52 204 945.4 945.2 946.3
swimming.
(1) Lake Harrison watershed area included in Lake Lucy watershed area.
In general, the recommendations confirm that the continued monitoring of transparency by
Secchi disc readings and sampling of water quality (primarily phosphorus) are the most
important activities to monitor the long-term trends in water quality of the City’s lakes. Each
lake will have its own needs for monitoring that are discussed more in the sections that follow.
This review focused on general trends and activities and, as such, does not in all cases provide
specific recommendations for additional parameters, monitoring locations or frequencies. In
some cases these recommendation are provided, while for others the details are best left to results
of more detailed lake management planning efforts or diagnostic studies.
2.Methods and Approach
The objectives of this discussion are three-fold. The first objective is to identify, summarize and
compare studies and lake monitoring results completed on the nine lakes since the 1994 Plan,
and to establish some trends and gaps in information. The second objective involves the review
and reclassification, if necessary, of each lake’s watershed land use determinations and nutrient
budgets. The third objective is to develop or revise short and long-term lake management
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strategies and goals to improve or manage these valuable natural resources towards trends
associated with high quality lakes in the Ecoregion. It should also be recognized that there have
been advances in lake management methods and data analysis; and these approaches will be
referenced and incorporated into the findings when appropriate. The first two objectives are
addressed below for each lake while the third objective is addressed globally following the
discussion of each lake.
a.Lake Ann (MNDNR I.D. No. 10-12P)
Lake Ann is located partially within a City of Chanhassen Municipal Park northwest of the
downtown area. Lake Ann has a surface area of 116 acres, a maximum depth of 45 feet and a
maximum depth of plant growth at 13 feet. The Ordinary High Water (OHW) level for Lake Ann
is 955.5 ft above Mean Sea Level (MSL). Plant growth is categorized as abundant and the
dominant bottom substrate is sand, detritus and muck. Public access is provided through a
concrete boat ramp located within the municipal park. Boats are restricted to non-motorized use
and electric motors.
Numerous studies and plans have been completed on Lake Ann, starting with the monitoring of
the lake water levels by the MNDNR in 1959. Water quality studies and monitoring events
occurred in 1994 and 2003. The following two studies were also generated on Lake Ann:
Aquatic Plant Surveys for Ann Lake, Chanhassen, Minnesota; May 2004 – results of
early summer survey in June 2003 and fall survey in September 2003.
Chanhassen Water Quality Monitoring Results for Ann, Lucy, Rice Marsh, and Susan for
2003.
These two studies, coupled with the 1994 Plan results, indicate that Lake Ann has maintained its
condition of a relatively healthy lake system. Utilizing the Metropolitan Council (Met Council)
grading criteria for metropolitan lakes (see criteria in Appendix F), Lake Ann was graded A for
all three categories of water quality: Secchi disc average (water clarity), total phosphorus, and
chlorophyll a. A grade of A is the highest quality ranking for these three parameters. Water
clarity appears to have improved since the 1994 Plan, when the average transparency value was
4.8 feet compared to the 2003 studies when it was 11.0 feet.
The Aquatic Plant Survey results also identify some trends for Lake Ann. The establishment of
Eurasian watermilfoil (Myriophyllum spicatum), a nuisance/exotic species, was first identified in
Lake Ann by the MNDNR in 1995. Despite the widespread distribution and relatively high
densities of Eurasian watermilfoil, Lake Ann’s aquatic vegetation community has continued to
maintain high species diversity and establishment of desirable species within both the
submergent and emergent vegetation communities. Curlyleaf pondweed (Potamegeton crispus),
another potential nuisance species, has also become established, but has not expanded
aggressively throughout Lake Ann. Whether or not this pondweed species will be a problem
remains to be seen. Perturbations in water quality typically drive pondweed growth invasions and
given the stable conditions, the probability of pondweed expansion may be low for Lake Ann.
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The 1994 plan identified Lake Ann as a mesotrophic lake in accordance with the data obtained.
The Plan further referenced that Lake Ann is borderline eutrophic and should be given high
priority for maintaining the mesotrophic status. Lake Ann was also identified as thermally
stratified with a defined thermocline. The stratification may account for the unusually high
phosphorus readings sampled in the lower strata (hypolimnion).
The existing management and water quality BMPs that have been implemented within the Lake
Ann watershed, the position of the lake within a City Park and undeveloped properties, and other
implemented management approaches will maintain the Met Council overall lake quality ranking
of A. Future monitoring and implementation activities should focus on:
Monitoring the health and diversity of the lake’s aquatic vegetation community, with a
special emphasis on Eurasian watermilfoil and curlyleaf pondweed management.
Additional water quality monitoring events should occur at least once per every five
years. Monitoring the phosphorus levels, especially within the hypolimnion, and secchi
disc sampling should occur monthly every year during the summer months.
Continue to follow the recommendations for Lake Ann in the 1994 Plan.
The 1994 Plan identified a list of proposed storm water ponds within the Lake Ann
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
were inventoried as part of the most recent wetland inventory. Table 23 is a summary of the
proposed storm water ponds in the Lake Ann subwatershed.
Table 23. Lake Ann Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
First Improve-2 LA-P1.7, LA-P1.13
Second Improve-2 LA-P1.5
Fourth Improve-2 LA-P1.2
Eighth Improve-2 LA-P1.9
The RPBCWD completed a Use Attainability Analysis (UAA) for Lake Lucy and Lake Ann in
1999. The UAA set specific goals and recommendations for water quality and quantity in the
Lake Ann Watershed. The following recommended BMPs were included in the UAA:
Preserve all existing wetlands in the watershed.
Add five ponds in the Lake Ann watershed in areas that contribute significant particulate
phosphorus loads to each lake.
Provide infiltration basins throughout the Lake Ann watershed in areas that experience a
significant change in impervious area between existing and future (Year 2020) land use
conditions.
Manage the lake’s macrophytes by continuing to survey communities in order to detect
nuisance, non-native growths.
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Refer to Figure Ex-8 in the Lake Lucy and Lake Ann UAA for the proposed locations for
upgraded and additional storm water ponds. Most of the recommended locations for additional
storm water ponds in the Lake Ann watershed are addressed in Appendix I of the Plan. The City
will continue to work with the RPBCWD as opportunities arise to construct the additional storm
water treatment ponds in the Lake Ann watershed.
b.Christmas Lake (MNDNR I.D. No. 27-137P)
Christmas Lake is located mostly within the City of Shorewood, but a small portion of it extends
into the north-central portion of the City of Chanhassen. Christmas Lake has a surface area of
257 acres, a maximum depth of 87 feet. The OHW level for Christmas Lake is 932.77 above
MSL. Public access is provided by a concrete boat ramp on the northwest bay. Christmas Lake
was partially evaluated in the 1994 Plan under the “Drainage to Neighboring Communities”
section.
A Christmas Lake Management Plan was completed in 1996 and partially funded by the City of
Chanhassen, the City of Shorewood, and the Christmas Lake Home Owners Association. In
summary, the management plan provided the following observations, analyses, and
recommendations.
Christmas Lake has a surface area of 257 acres and a watershed of approximately 410 acres.
Water quality studies on Christmas Lake extend as far back as 1908, and included chemical
analyses in 1993 and 1994. The lake is strongly thermally stratified with a well defined
thermocline and a very oxygen-poor hypolimnion. Nutrients, in particular phosphorus, are in low
to moderate concentrations and appear to be stable. The aquatic vegetation community is diverse,
but Eurasion watermilfoil was first documented in 1992 and curlyleaf pondweed has also
invaded. Both nuisance species are being monitored and controlled when necessary. Christmas
Lake is a “two-story” fishery with warm water species in the warmer hyperlimnion and shallows
depths, and cold water species (MNDNR stocked rainbow trout) in the hypolimnion and deeper,
colder depths.
The Christmas Lake Management Plan includes management and improvement
recommendations that are either in-lake or within the watershed. Most of these are outside of the
City of Chanhassen, with the exception of the recommendations established in the 1994 SWMP.
The recommendations for Christmas Lake are to:
Implement BMPs in the Chanhassen areas tributary to the lake, as opportunities arise,
that address storm water runoff management and nutrient runoff controls (i.e., ponding
areas).
Continue to follow the 1994 SWMP recommendations and install ponding areas based on
the classification system (priority basis) of this Plan if they have not yet been
implemented (see Appendix I).
The 1994 Plan identified a list of proposed storm water ponds within the Christmas Lake
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
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from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
were inventoried as part of the most recent wetland inventory. Table 24 is a summary of the
proposed storm water ponds in the Christmas Lake subwatershed.
Table 24. Christmas Lake Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
Fifth Improve-2 CL-P1.2A
Sixth Improve-2 CL-P2.2
Eighth Improve-2 CL-P1.1
rd
The MCWD’s 3 Generation Water Management Plan, which is in the process of being
completed, sets phosphorus loading reduction goals for the cities in the watershed. In the
Christmas Lake subwatershed, the phosphorus loading reduction goal for Chanhassen is 7
lbs/year. By constructing two of the proposed ponds in Appendix I, ponds CL-P1.2A and CL-
P2.2, Chanhassen will be meeting this phosphorus reduction goal.
c.Lotus Lake (MNDNR I.D. No. 10-6P)
Lotus Lake is located in the northeast corner of the City of Chanhassen. Lotus Lake has a surface
area of 246 acres, and a maximum depth of 29 feet. The OHW level for Lotus Lake is 896.3 ft
above MSL. Lotus Lake is classified as eutrophic. Access is provided at South Lotus Lake Park
located on the south end of the lake.
Lotus Lake has been monitored for water clarity sporadically since at least 1979. Secchi disc
readings taken in 1979, 1980, 1988, 1989, 1990, 1991, 1993 and 2004 show a gradual
improvement trend in water clarity. The 1979 average reading was 2.8 feet and the most recent
reading (2004) was 5.2 feet. Lotus Lake’s water clarity ranges from “acceptable” to “good”, and
is “impaired” for recreational use (a common ranking for Metropolitan area lakes) according to
the Met Council. Past monitoring and the 1993 Plan studies also demonstrated that chlorophyll a
values and high phosphorus value increases in Lotus Lake are coupled with decreases in water
clarity, another expected trend.
An Aquatic Plant Survey for Lotus Lake was completed in 2004. Eurasian watermilfoil
(Mynophyllum spiratum) was first documented in 1989 and is the second most abundant species
in the lake, with coontail (Ceratophyllum demersum) being the most abundant. Curlyleaf
pondweed has also become well established. Six species of submergent and six emergent species
were documented. Emerged vegetation grew to a depth of seven feet in Lotus Lake. The 1994
Plan also identified some stands of purple loosestrife (Lythrum salicaria) within fringe and
adjacent wetland basins. Lastly, American lotus (Nelumbo lutea) was also identified in the
Aquatic Plant Survey. The American Lotus is listed as a ‘DNR Protected Wild Flower’ on the
DNR’s website and no removal is allowed.
In addition to the storm water and surface water based recommendations that were provided in
the 1994 Plan, additional recommendations here include:
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Focusing on the management of nuisance invasive/exotic species, primarily Eurasian
watermilfoil, curlyleaf pondweed and purple loosestrife.
Control of Eurasian watermilfoil is critical, especially in light of the presence of the
American lotus. Eurasian watermilfoil could potentially out-compete and eliminate lotus
and other species from the lake. The extensive coverage established by Eurasian
watermilfoil in Lotus Lake warrants the need for control. Curlyleaf pondweed should be
monitored and controls implemented if it becomes dominant.
Purple loosestrife control should be continued or initiated and biocontrol agents (beetles)
seem to be the best long-term solution.
The 1994 Plan identified a list of proposed storm water ponds within the Lotus Lake
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
were inventoried as part of the most recent wetland inventory. Table 25 is a summary of the
proposed storm water ponds in the Lotus Lake subwatershed.
Table 25. Lotus Lake Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
First Improve-1 LL-P7.5
Second Improve-1 LL-P9.2, LL-P10.17
Third Improve-1 LL-P2.2, LL-P6.6
Fourth Improve-1 LL-P6.7
Fifth Improve-1 LL-P2.1
Sixth Improve-1 LL-P2.5
Seventh Improve-1 LL-P8.1, LL-P8.2
The RPBCWD completed a Use Attainability Analysis (UAA) for Lotus Lake in 2005. The
UAA set specific goals and recommendations for water quality in Lake Lotus. It was determined
in the UAA that watershed loading provides approximately 23 percent of the annual total
phosphorus to the lake, while internal loading (caused by direct release of phosphorus from lake
sediments) provides approximately 62 percent of the annual total phosphorus to the lake. The
UAA also states that improving the lake’s water clarity will likely result in increased curlyleaf
pondweed and Eurasian water milfoil unless a vegetation management program is completed
first. Therefore following implementation plan was selected for the management of aquatic
plants and water quality in Lotus Lake:
Herbicide treatment of curlyleaf pondweed and Eurasian watermilfoil for 4 years
followed by 3 consecutive years of alum treatment.
Beetles (Galerucella pusilla, Galerucella calmariensis) will be introduced in purple
loosestrife infested areas to control shoreline purple loosestrife and promote native
vegetation.
The City will continue to work with the RPBCWD on the implementation plan for the Lotus
Lake.
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d.Lake Lucy (MNDNR I.D. No. 10-7P)
Lake Lucy is located within the central portion of the City of Chanhassen, northwest of the
downtown area and immediately north of Lake Ann. Lake Lucy has a surface area of 92 acres, a
maximum depth of 20 feet, and a maximum depth of plant growth of 10 feet. The OHW level for
Lake Lucy is 956.1 MSL. Plant growth is abundant and the bottom substrate is muck, detritus,
and sand. The vast majority of land on Lake Lucy is privately owned and, therefore, public
access is not available except through the channel connecting with Lake Ann, which is neither
permanent nor maintained to provide human or vehicular access
Starting in 1990, Lake Lucy has been monitored for water clarity annually. Average secchi disc
readings during this period have varied from a low of 2.6 feet in 1998 to a high of 5.3 feet in
2002. The remaining readings have varied within these two extremes. The water clarity,
phosphorus and chlorophyll a trends assessed under the Met Council’s criteria indicate that Lake
Lucy’s overall water quality fluctuates between “impaired” to “severely impaired”. High
phosphorus is attributed as the main source of the poor water quality. Since the late 1980s, the
source of the phosphorus has shifted from agricultural to urban storm water run-off sources. The
trend was determined through a lake modeling study completed during the preparation of the
1994 Plan.
Single family housing developments are currently the largest source of the storm water run-off
and pollutant loading in the Lake Lucy watershed. Some of the loading results from human
activities like fertilizing lawns and spillage of the fertilizers or grass clippings into the streets
where it has a more direct route to the lake. Also, there are few storm water ponds in the
subwatershed. Previous modeling demonstrated that, under the present and future land use
conditions with “NURP-level” storm water management practices (i.e., treatment consistent with
the City’s NURP standard), Lake Lucy will not degrade further, but it also will not likely
improve.
In 2003 a water quality study was completed on Lake Lucy. The average secchi disc reading was
6.9 feet, a significant improvement over the previous years’ values. Phosphorus and chlorophyll
a values also show an improving water quality trend. The Met Council grades for each of these
three parameters is “C”, “B-“, and “B+” respectively. The Overall Quality value for Lake Lucy
was B. These results suggest that Lake Lucy’s water quality may be improving.
An Aquatic Plant Survey for Lake Lucy was also completed in 2003. Eurasian watermilfoil, first
confirmed in 1989, was not present in the 2003 survey. This may be the result of a species
misidentification in 1989. The 2003 survey identified northern milfoil (Myriophyllum sibricum),
a similar-looking related species that is native and not considered a nuisance species. Eurasian
watermilfoil was observed in Lake Lucy during the wetland inventory, so it is still present.
Curlyleaf pondweed was present and comprised nearly half of the submergent vegetative
community. Coontail was the most abundant of the 11 submergent species identified and two
emergent species were identified. The maximum depth of plant establishment was 10 feet.
The storm water quality, wetland restoration/management, and lake management
recommendations discussed in the 1994 Plan should be revaluated and updated due to the land
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use changes within the lake watershed. Recent studies suggest that water quality may be
improving. Specific recommendations for Lake Lucy include:
Curlyleaf pondweed should be monitored and a control/management plan should be
developed.
A Lake Lucy Lake Management Plan is recommended to identify if the lake water quality
is improving and the sources driving this improvement.
A vegetation management plan should be developed separately or as part of an updated
Lake Management Planning project.
The 1994 Plan identified a list of proposed storm water ponds within the Lake Lucy
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
were inventoried as part of the most recent wetland inventory. Table 26 is a summary of the
proposed storm water ponds in the Lake Lucy subwatershed.
Table 26. Lake Lucy Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
Second Improve-3 LU-P3.4
Third Improve-3 LU-P5.2, LU-P5.14, LU-P5.16
Fourth Improve-3 LU-P5.13
Fifth Improve-3 LU-P5.12
Sixth Improve-3 LU-P5.3
Seventh Improve-3 LU-P6.1
LU-P2.6, LU-P5.4, LU-P5.10,
Eighth Improve-3
LU-P6.2
The RPBCWD completed a Use Attainability Analysis (UAA) for Lake Lucy and Lake Ann in
1999. The UAA set specific goals and recommendations for water quality and quantity in the
Lake Lucy Watershed. The following recommended BMPs were included in the UAA:
Preservation of al existing wetlands in the Lake Lucy watershed.
Upgrade two ponds in the Lake Lucy watershed to provide more wet detention for
stormwater treatment.
Add seven ponds in the Lake Lucy watershed areas that contribute significant particulate
phosphorus loads to the lake.
Refer to Figure Ex-8 in the Lake Lucy and Lake Ann UAA for the proposed locations for
upgraded and additional storm water ponds. Most of the recommended locations for additional
storm water ponds in the Lake Lucy watershed are addressed in Appendix I of the Plan. The City
will continue to work with the RPBCWD as opportunities arise to construct the additional storm
water treatment ponds in the Lake Lucy watershed.
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e.Lake Minnewashta (MNDNR I.D. No. 10-9P)
Lake Minnewashta is located in the northwestern portion of the City of Chanhassen. Lake
Minnewashta has a surface area of 738 acres, a maximum depth of 70 feet, and a maximum
depth of plant growth at 8 feet. The OHW level is 944.5 MSL. Plant growth is categorized as
abundant and the bottom substrate is comprised of sand, detritus, and muck. Public access is
available at two locations within Lake Minnewashta Regional Park.
Water quality sampling data on Lake Minnewashta is fairly extensive. Water transparency
sampling has occurred annually since 1978. The Met Council ranks Lake Minnewashta as “very
good” with regards to water quality, and that is reflected in the average annual secchi disc
readings at or around 7 feet and the low phosphorus readings which are well within the ecoregion
value standard. Lake Minnewashta is classified as mesotrophic and this trophic status is stable.
After completion of the 1994 Plan, additional studies were completed on Lake Minnewashta,
including a Lake Management Plan in 1995 and an Aquatic Plant Survey in 2001. The primary
objective established in the Lake Management Plan was maintaining the lake at the ecoregion
values through the maintenance of water transparency averages at 5 to 7 feet, and phosphorus
values below 40 parts per billion (ppb). Another objective was to develop an approach to
implement Eurasian watermilfoil control/management, ultimately leading to the Aquatic Plant
Survey.
The Aquatic Plant Survey confirmed the extent of the Eurasian watermilfoil infestation, first
detected in 1989. Eurasian watermilfoil vegetative coverage exceeded 50% during the first half
of the summer. Curlyleaf pondweed was also detected, but in relatively lower abundances
compared to Eurasian watermilfoil. Nevertheless, curlyleaf pondweed does have the potential to
expand and become a concern, and monitoring is recommended. Despite the presence and extent
of these nuisance species, Lake Minnewasta’s aquatic vegetation community is diverse and rich
with desirable species. Approximately 21 submergent, 3 floating, and 4 emergent species were
identified.
The Lake Management Plan for Lake Minnewashta identified and appended additional
information to the water quality improvement and storm water management needs within the
lake’s watershed. Wetland quality and restoration potential were also analyzed. The physical,
chemical and biological aspects of the lake were analyzed and summarized in the plan, and the
results were utilized to model and predict future in-lake trends and management needs. The Lake
Management Plan utilized these findings to develop short and long-term implementation
strategies including the following:
Continue to implement storm water management and wetland restoration projects within
the Lake Minnewashta watershed.
Monitor adjacent wetlands for phosphorus input.
Educate and promote conservation, water quality, and lake management BMPs to
watershed residents, for example, through the MNDNR’s lakescaping program.
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Implement vegetation management, restoration, and nuisance/invasive species control
including both within the lake (Eurasian watermilfoil) and watershed (purple loosestrife).
Curlyleaf pondweed has the potential to expand and ongoing monitoring is
recommended.
The 1994 Plan identified a list of proposed storm water ponds within the Lake Minnewashta
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
were inventoried as part of the most recent wetland inventory. Table _ is a summary of the
proposed storm water ponds in the Lake Minnewashta subwatershed.
Table 27. Lake Minnewashta Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
LM-P4.2, LM-P5.2,
First Improve-2
LM-P7.5, LM-P8.11
LM-P1.12, LM-P3.16,
Second Improve-2
LM-P5.20, LM-P8.8
LM-P1.5, LM-P4.3,
Third Improve-2
LM-P8.10
LM-P1.6, LM-P3.2,
Fourth Improve-2
LM-P3.13
LM-P1.9, LM-P3.15,
Fifth Improve-2
LM-P5.6
LM-P3.1, LM-P3.8,
Sixth Improve-2 LM-P3.10, LM-P5.3,
LM-P5.5
Seventh Improve-2 LM-P5.4, LM-P5.14
Eighth Improve-2 LM-P5.21, LM-P8.1
rd
The MCWD’s 3 Generation Water Management Plan, which is in the process of being
completed, sets phosphorus loading reduction goals for the cities in the watershed. In the Lake
Minnewashta subwatershed, the phosphorus loading reduction goal for Chanhassen is 27
lbs/year. By constructing the first nine prioritized ponds listed in Appendix I, Chanhassen will be
meeting this phosphorus reduction goal by removing approximately 28 lbs/year. The nine ponds
include:
LM-P4.2
LM-P5.2
LM-P1.12
LM-P3.16
LM-P5.20
LM-P8.8
LM-P1.5
LM-P4.3
LM-P8.10
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f.Rice Lake (MNDNR I.D. No. 27-132P)
Rice Lake is located in the southeast corner of the City of Chanhassen, on the border of
Chanhassen and Eden Prairie. The Lower Minnesota River Watershed District (LMRWD) Plan
describes Rice Lake as a floodplain lake. Bluff Creek flows into Rice Lake, and it is located
within the Raguet Wildlife Management Area. Very little water quality information is available
on this lake. According the LMRWD Plan, floodwaters from the Minnesota River contribute a
large portion of the overall nutrients and sediments to this lake, and once the flooding subsides
the high sediment and nutrient loads are trapped in the lakes. The LMRWD Plan states that
improvement to the Minnesota River water quality will help reduce this heavy sediment and
nutrient loading to the floodplain lakes like Rice Lake.
g.Rice Marsh Lake (MNDNR I.D. No. 10-1P)
Rice Marsh Lake is located in the east-central portion of the City of Chanhassen, and a portion
(126 acres) of the watershed occurs within the City of Eden Prairie. Rice Marsh Lake is a flow-
through basin with an inlet that receives outflow from Lake Susan and an outlet that discharges
into Lake Riley. Rice Marsh Lake has a surface area of 79 acres and a maximum depth of 11
feet. The OHW level is 877.0 MSL. There are no public accesses on Rice Marsh Lake. Rice
Marsh Lake is surrounded by extensive beds of emergent vegetation, some of which have been
excavated for water quality improvements. Rice Marsh Lake has had a wastewater treatment
plant on its northern shore.
The 1994 Plan recognized that Rice Marsh Lake was not a well studied lake. Despite this status,
water quality and clarity data was available annually from 1972 through 1991. Rice Marsh Lake
is classified as hypereutrophic due to excessive nutrients (high phosphorus), excess algae, and
poor water clarity, with average Secchi disc readings of 1.5 feet. Based on the data available, the
trophic conditions are likely attributed to several factors, including the lake’s small size, shallow
depths, watershed-to-lake ratio (large watershed compared to the size of the lake), specific land
uses and, to some extent, the wastewater treatment plant discharge. The Met Council score for
water quality on Rice Marsh Lake ranges from “poor” to “very poor”.
Following the recommendations of the 1994 Plan, a Water Quality Monitoring study and Aquatic
Plant Survey were both completed for Rice Marsh Lake in 2003. The results demonstrate a trend
of improving water quality. Water clarity (Secchi disc) readings averaged 7.0 feet and were
consistent throughout the summer. Phosphorus has dropped below the 40 ppb threshold and
chlorophyll a was noticeably lower. The new Met Council grading system gave an overall water
quality grade of B, which is an improvement over the “poor” to “very poor” grade. Grade B
would equate to “good” in the old system.
The Aquatic Plant Survey identified five species of emergent plants and two submerged species.
No Eurasian watermilfoil was identified, but curlyleaf pondweed was extensive with peak
coverage of 64% in the early summer. Coontail was the most abundant submerged species with
nearly 97% coverage at the end of summer. White water lily (Nymphaea tuberosa) was the most
abundant emergent species, covering 50% of the lake surface. Floating filamentous algae mats
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became well established throughout the lake towards the end of summer. With a maximum depth
of plant growth at 10 feet, most of Rice Marsh Lake is littoral and vegetated.
Future management needs and watershed improvements for Rice Marsh Lake are to:
Focus on continued implementation of the recommendations in the 1994 Plan.
Development and implementation of a lake management plan or strategy for controlling
curlyleaf pondweed. A Lake Management Plan is a recommended tool that may be a
means to identify the sources of the improved water quality on Rice Marsh Lake, and is a
tool for setting long and short term management goals and priorities. For example, given
the shallow depths and flow-through hydrology of Rice Marsh, management priorities
could focus on managing Rice Marsh Lake for wildlife, or for multiple uses that include
wildlife management with storm water or flood storage improvements.
The 1994 Plan identified a list of proposed storm water ponds within the Rice Marsh Lake
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
were inventoried as part of the most recent wetland inventory. Table 28 is a summary of the
proposed storm water ponds in the Rice Marsh Lake subwatershed.
Table 28. Rice Marsh Lake Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
First Improve-3 RM-P5.7
Third Improve-3 RM-P4.9
Fifth Improve-3 RM-P3.1
The RPBCWD completed a Use Attainability Analysis (UAA) for Rice Marsh Lake and Lake
Susan in 1999. The UAA set specific goals and recommendations for water quality and quantity
in the Rice Marsh Lake watershed. The following recommended BMPs were included in the
UAA:
Upgrade five ponds in the Rice Marsh Lake watershed.
Add four ponds in the Rice Marsh Lake watershed.
Treat Rice Marsh Lake with in-lake alum treatment.
Refer to Figure Ex-7 in the Lake Susan and Rice Marsh Lake UAA for the proposed locations
for upgraded and additional storm water ponds. Most of the recommended locations for
additional storm water ponds in the Rice Marsh Lake watershed are addressed in Appendix I of
the Plan. According to the 2005 wetland and storm water pond inventory, improvements have
been made at several locations within the Rice Marsh Lake watershed. The City will continue to
work with the RPBCWD as opportunities arise to construct the additional storm water treatment
ponds in the Rice Marsh Lake watershed.
h.Lake Riley (MNDNR I.D. No. 10-2P)
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Lake Riley is located in the east-central portion of the City of Chanhassen and a portion (603
acres) of the watershed is within the City of Eden Prairie. Lake Riley is the last watershed in a
chain-of-lakes in Chanhassen and receives run-off from upstream watersheds. Surface water
management within the City and in upstream watersheds can have effects on Lake Riley. Lake
Riley has a surface area of 297 acres, a maximum depth of 49 feet, and an OHW level of 865.3
MSL. Public access is available within an Eden Prairie City park located on the northeast side of
the lake.
The information on Lake Riley in the 1994 Plan is relatively extensive. Water clarity monitoring
has been conducted annually since 1979. Secchi disc readings have fluctuated widely with a high
of 6.6 feet in 1982 to a low of 2.0 in 1997. Phosphorus levels and chlorophyll a have also spiked
and fluctuated, and the 1994 Plan shows a strong correlation between water clarity and nutrient
loading. Water clarity decreases during years of high phosphorus and chlorophyll a readings,
indicating that phosphorus is the primary vector driving water quality on Lake Riley. The Met
Council water quality ranking for Lake Riley is “poor” to “very poor”. Lake Riley is also
classified as eutrophic. At the time of the 1994 Plan, Lake Riley’s watershed was predominantly
agricultural. Watershed conditions and the position of Lake Riley within the chain-of –lakes
could be potential factors for the poor water quality.
A Lake Riley Aquatic Plant Survey was completed in 2001. The presence of Eurasian
watermilfoil was first confirmed in 1990 and was the second most abundant submergent species
(56% cover) documented after coontail (60% cover). Curlyleaf pondweed was also present but
only comprised approximately 2% of the vegetative cover. Five submergent species and no
emergent or floating leaf species were documented on Lake Riley.
Lake Riley is one of the twelve lakes where the contributing watershed has experienced a
measurable change in land use since completion of the 1994 Plan. The major development
changes are a result of new residential developments. The hydrologic model update also
identified an increase in the runoff curve number between the 1994 and 2006 Plans.
The 1994 Plan recommended updating the diagnostic/feasibility study completed for Lake Riley
in 1980. A comparable, equivalent and more contemporary format would be a water quality
monitoring study. This study should reevaluate the water quality of Lake Riley in accordance
with the changes in land use, as the Lake Riley watershed appears to have become more
urbanized and less agricultural since the 1994 Plan. The study should determine if phosphorus is
still a major concern and source of the eutrophic conditions. Upon completion of the water
quality monitoring study, a lake management plan can be assembled with long and short term
management goals for improving the water and biological quality of Lake Riley. Similarly, the
Lake Riley Aquatic Plant Survey includes supporting information for completion of the
Management Plan and for assembly of an Aquatic Vegetation Management Plan for Lake Riley.
There are proposed improvement projects within the Rice Marsh Lake and Riley Lake
subwatersheds to improve the water quality of both lakes. The Cities of Chanhassen and Eden
Prairie have petitioned these projects, and they will be designed and managed by the Riley
Purgatory Bluff Creek Watershed District.
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Specific recommendations for Lake Riley include:
Completion of a water quality monitoring study in lieu of an update to the diagnostic
feasibility study. Details of the monitoring study would be established considering the
data needs of the planned TMDL study. Alternatively, the City could delay completion
of the study until after the non-degradation assessment has been completed as part of the
NPDES permit.
Support the implementation of water quality treatment practices throughout the
watershed.
The 1994 Plan identified a list of proposed storm water ponds within the Lake Riley
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
were inventoried as part of the most recent wetland inventory. Table 29 is a summary of the
proposed storm water ponds in the Lake Riley subwatershed.
Table 29. Lake Riley Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
Second Improve-1 LR-P2.5, LR-P4.6
Third Improve-1 LR-P2.3, LR-P2.6, LR-P3.8
Fourth Improve-1 LR-P4.5
Fifth Improve-1 LR-P3.6
Sixth Improve-1 LR-P3.3
Seventh Improve-1 LR-P2.2, LR-P3.7
The RPBCWD completed a Use Attainability Analysis (UAA) for Lake Riley in 2002. The UAA
set specific goals and recommendations for water quality and quantity in the Lake Riley
watershed. The following recommended BMPs were included in the UAA:
Treat Rice Marsh Lake with alum and lime slurry.
Treat Lake Riley with alum.
Treat highway runoff by constructing three ponds in the Lake Riley watershed.
Refer to Figure 14 in the Lake Riley UAA for the proposed locations for upgraded and additional
storm water ponds. Most of the recommended locations for additional storm water ponds in the
Lake Riley watershed are addressed in the TH 212 storm water management system. The City
will continue to work with the RPBCWD as opportunities arise to construct the additional storm
water treatment ponds in the Lake Riley watershed.
i.Lake Susan (MNDNR I.D. No. 10-13P)
Lake Susan is located in the central portion of Chanhassen and receives significant hydrology
from Lake Ann via open channel and several large wetlands. Lake Susan discharges through an
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outlet into Rice Marsh Lake, all within the Chanhassen chain-of-lakes. Lake Susan has a surface
area of 93 acres, a maximum depth of 17 feet and an OHW of 881.8 MSL. The Lake Susan
watershed is well developed with many different land use types. Lake Susan has a 13:1
watershed area to lake area ratio, making storm water treatment a critical need. Lake Susan is
classified as hypereuthrophic. Public access is provided through a City park located on the
northwest side of the lake and a significant amount of land on Lake Susan is publicly owned.
The 1994 Plan identified Lake Susan with a Met Council ranking of “very poor” for water
quality. Water clarity was poor in most years with annual averages of 2.0 feet, and total
phosphorus levels typically exceed 40 ppb. Chlorophyll a values also correlated with increased
phosphorus and decreased Secchi disc values. The temperature profiles suggest that Lake Susan
rarely or poorly stratifies and is subject to low oxygen conditions (anoxia). The lack of
stratification enhances mixing and contributes to algae blooms through nutrient mixing of the
bottom sediments. The findings of the 1994 Plan resulted in additional studies, planning and
ultimately a restoration project for Lake Susan.
The Lake Susan Management Plan, completed in 1998, involved additional water quality and
water clarity diagnoses, identified water quality and biological trends, and identified lake
management objectives and restoration projects. Phosphorus from surface water run-off and in-
lake conditions (e.g. rough-fish) was identified as the potential sources for Lake Susan’s
hypereutrophic conditions. Storm water management, wetland restoration and management,
whole lake chemical treatment, and rough-fish control were recommended actions in the Lake
Management Plan.
In 1998, four Lake Susan restoration projects were implemented and evaluated in annual
monitoring events through 2001, including the following:
Carp and bullhead harvesting conducted in the winter – approximately 18,700 pounds of
carp and 6,000 pounds of bullheads were removed.
Spring bullhead trapping – involved removal of 17,000 pounds of bullhead in 1998 and
another 14,000 pounds in 1999.
Carp barrier installation – a carp barrier was placed at the Lake Susan outlet. This carp
barrier is marginally effective.
Whole-lake alum treatment – 40,000 gallons of alum were applied in the Spring of 1998.
Lake Susan responded rapidly following the completion of the four restoration efforts, and the
improved water quality results were sustained during the three year monitoring schedule.
Phosphorus concentrations dropped to around 40 ppb, and secchi disc readings improved to as
high as seven feet, the best readings since recordkeeping was initiated in 1971. Other projects
have complimented and benefited the restoration efforts, including the installation of a winter
aeration system, creation of a new wetland in the watershed, and storm water pond
improvements. Additionally, riparian buffer plantings and bioengineered shoreline stabilization
were also completed on Lake Susan in 2002-2003 and 2004-2005, respectively.
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Lastly, an Aquatic Plant Survey was completed for Lake Susan in 2003. The survey occurred one
year prior to the confirmation of Eurasian watermilfoil in 2004. The survey identified six
submergent, three floating-leaved, and one emergent species. Curlyleaf pondweed was present
and comprised 28% of the emergent vegetative cover making it the most abundant species in
Lake Susan. American lotus (Nelumbo lutea) is common in the lake, particularly in the southwest
portion.
Future restoration and management efforts on Lake Susan and within the watershed should
continue to focus on:
Implementation of storm water management BMPs within the watershed.
Active efforts to control rough fish.
With the recent and confirmed establishment of Eurasian watermilfoil, future efforts
should also focus on monitoring and managing nuisance species, including curlyleaf
pondweed.
Participate in the installation of a carp barrier between Lake Susan and Rice Marsh Lake
that will be installed by the MnDNR and paid for by the RPBCWD in conjunction with
the TH 101 corridor project.
The 1994 Plan identified a list of proposed storm water ponds within the Lake Susan
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
were inventoried as part of the most recent wetland inventory. Table 30 is a summary of the
proposed storm water ponds in the Lake Susan subwatershed.
Table 30. Lake Susan Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
Third Improve-2 LS-P3.1, LS-P2.12, LS-P3.7A
Fourth Improve-2 LS-P3.7B
Fifth Improve-2 LS-P3.8
Eighth Improve-2 LS-P1.3
The RPBCWD completed a Use Attainability Analysis (UAA) for Rice Marsh Lake and Lake
Susan in 1999. The UAA set specific goals and recommendations for water quality and quantity
in the Rice Marsh Lake watershed. The following recommended BMPs were included in the
UAA:
Upgrade or improve nine storm water ponds in the Lake Susan watershed.
Add eight storm water ponds in the Lake Susan watershed.
Treat Lake Susan with an in-lake alum treatment.
Refer to Figure Ex-7 in the Lake Susan and Rice Marsh Lake UAA for the proposed locations
for upgraded and additional storm water ponds. Most of the recommended locations for
additional storm water ponds in the Lake Susan watershed are addressed in Appendix I of the
Plan. In-lake alum treatment has been used in the past to provide improvement to Lake Susan’s
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water quality. The City will continue to work with the RPBCWD as opportunities arise to
construct the additional storm water treatment ponds and provide additional treatment in the
Lake Susan watershed.
j.Lake St. Joe (MNDNR I.D. No. 10-11P)
Lake St. Joe is a small lake located in the northwest corner of the City of Chanhassen on the west
side of Lake Minnewashta. Despite the small surface area (14 acres of open water), Lake St. Joe
is relatively deep with a maximum depth of 52 feet. The OHW level is at elevation 945.2 above
MSL. A small portion of Lake St. Joe’s watershed occurs within the City of Victoria. Lake St.
Joe discharges to Lake Minnewashta through a 42-inch pipe. Public access is available on the
northeast side of the lake.
A Lake St. Joe Management Plan was completed in 1998 in response to the following conditions
identified in the 1994 Plan. Lake St. Joe is meso-eutrophic with good water clarity averaging 7.0
annually, but had very high phosphorus concentrations, especially within the bottom sediments.
This was attributed to historical and existing surface water run-off contributions. The Lake St.
Joe Management Plan established the following goals for implementation:
Maintain the summer average phosphorus concentration range of 30 to 42 ppb.
Maintain a range of secchi disc readings from 5 to 7 feet throughout the summer.
Maintain native aquatic vegetative coverage at 40 percent or greater.
A Lake St. Joe Aquatic Plant Survey was completed in 2001. Two submergent and three
emergent species were identified and no nuisance species were present or have been documented
since 2001. The recommended goals can be achieved through:
Implementation of storm water management BMPs within the watershed and considering
the priority of the lake in the classification system.
Consider the possibly of using in-lake phosphorus treatments.
Continued monitoring is recommended, especially for phosphorus concentrations.
3.Lakes Summary
Table 31 summarizes the management recommendation discussed above for each lake within the
City. The storm water pond recommendations within each of these lake’s watersheds, based in
part on the 1994 Plan recommendations, are included in Appendix I for reference. Overall, the
nine lakes addressed in the 1994 Plan have undergone varying degrees of improvement through
increased monitoring, in-lake management, and storm water management. With the exception of
Lake Riley, Lake Lucy and Lake Susan, the contributing watersheds for the other eight lakes
have experienced little to no change in land use in the contributing watersheds since the 1994
Plan. Furthermore, it is probably safe to assume the improved stormwater management methods
and applications that have been constructed and/or retrofitted within each lake watershed are
partially responsible for water quality improvements or observed steady trends. This assumption
extends to areas within and beyond the City limits into the major watershed.
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Approximately 8 percent of Minnesota’s river miles and 14 percent of Minnesota’s lakes have
been tested for pollution problems. Approximately 40 percent of those tested are polluted with
human and animal waste, algae from phosphorus, fertilizers and mercury. As more of the states’
surface waters are tested for pollution problems, the state will continue to add surface waters to
the TMDL list. It is possible that additional surface waters within the City of Chanhassen will be
added to this list in the future.
The management goals and objectives established for each lake have in some cases been
implemented or even achieved. The extensive lake monitoring that has and will continue to occur
should allow continued tracking of each lake and provide a base of comparison to ensure that
these goals and objectives continue to be met.
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Table 31. Lake Management Recommendation Summary.
Lake Recommendations Schedule Comments
Develop a Comprehensive Lake Management Plan. The plan should focus
2010-2012
This item addresses completion of
Ann
on two primary components: (1) monitoring; and (2) management.
the plan itself.
(1) Monitoring activities should include assessing the health and diversity
Annually
Secchi disc sampling should occur
of the lake’s aquatic vegetation community, with a special emphasis on
monthly every year during the
Eurasian watermilfoil and curlyleaf pondweed and continuing the current
summer months.
water quality monitoring program.
(2) Management activities should include regular assessments of
Ongoing
monitoring data to identify consistency or shifts in trends.
Support the implementation activities in the 1996 Lake Management Plan
Ongoing
In cooperation with Shorewood and
Christmas
Hennepin County.
Develop a Comprehensive Lake Management Plan. The plan should focus
2008-2010 Coordinate with TMDL Study.
Lotus
on two primary components: (1) monitoring; and (2) management.
(1) Monitoring activities should include assessing the health and diversity
Annually
Continue or initiate control of purple
of the lake’s aquatic vegetation community, with a special emphasis on
loosestrife with bioagents (beetles)
Eurasian watermilfoil and curlyleaf pondweed, and continuing the current
water quality monitoring program.
(2) Management activities should include regular assessments of
Ongoing
monitoring data to identify consistency or shifts in trends.
Participate in the development of the Total Maximum Daily Load (TMDL)
Track Study start date depends on
Study to reduce nutrient loading. The 1994 Plan also recommended that
TMDL availability of funding through
wetlands along the fringe of Lotus Lake should be sampled and monitored to
start date MPCA.
determine their phosphorus input to the lake.
Complete a Feasibility Study to evaluate the extended high water levels on
2007
Use updated model as a starting
Lotus Lake with the goal of identifying what, if any, combination of storage
point. May need to import data to an
in the upstream areas and/or outlet structure modifications would limit the
XP-SWMM model to evaluate
extent or duration of high water levels. See also Water Quantity project
effects of additional storage areas in
Recommendations.
more detail.
A detailed analysis of alternatives to eliminate street flooding at Carver
2007
Carry over from 1994 (confirm if
Beach Road should be undertaken.
complete or still pending).
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Table 31. Lake Management Recommendations
(Continued)
Lake Recommendations Schedule Comments
Develop a Comprehensive Lake Management Plan. The plan should focus
2012-2014
This item addresses completion of
Lucy
on two primary components: (1) monitoring; and (2) management.
the plan itself.
(1) Monitoring activities should include assessing the health and diversity
Annually
Water quality trend appears to be
of the lake’s aquatic vegetation community, and continuing the current
improving.
water quality monitoring program.
(2) Management activities should include regular assessments of
Ongoing
Identify what management activities
monitoring data to identify consistency or shifts in trends.
can be applied to other watersheds.
Continue to implement the activities specified in the Lake Management
Ongoing
Nuisance species control includes
Minne-
Plan. Notable activities include: monitoring adjacent wetlands for
both within the lake (Eurasian
washta
phosphorus input; and implementation of vegetation management,
watermilfoil) and watershed (purple
restoration, and nuisance species control.
loosestrife).
Develop a Comprehensive Lake Management Plan. The plan should focus
2014-2016
This item addresses completion of
Rice
on two primary components: (1) monitoring; and (2) management. Also
the plan itself.
Marsh
consider setting priorities for wildlife management, storm water or flood
storage management as part of the plan development.
(1) Monitoring activities should include assessing the health and diversity
Annually
Assess the need for wildlife habitat
of the lake’s aquatic vegetation community, and continuing the current
improvements by landscaping the
water quality monitoring program.
near shore areas.
(2) Management activities should include regular assessments of
Ongoing
Implement strategy(ies) for
monitoring data to identify consistency or shifts in trends.
controlling curlyleaf pondweed.
Focus efforts on new and retrofit ponds and phosphors reduction BMPs in
Annually
The 1994 Plan indicated the need to
Riley
the watershed. Use pond summary in Appendix I as the basis for evaluating
develop a better understanding of
pond options.
source of algae blooms.
Develop a Comprehensive Lake Management Plan. The plan should focus
2006-2008 Coordinate with TMDL study.
on two primary components: (1) monitoring; and (2) management.
(1) Monitoring activities should include assessing the health and diversity
Annually
of the lake’s aquatic vegetation community, and continuing the current
water quality monitoring program.
(2) Management activities should include regular assessments of
Ongoing
Look for opportunities to implement
monitoring data to identify consistency or shifts in trends.
additional regional or local storm
water treatment systems.
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Table 31. Lake Management Recommendations
(Continued)
Lake Recommendations Schedule Comments
Continue to implement the activities specified in the Lake Management
Ongoing
Susan
Plan.
(1) Monitoring activities should include assessing the health and diversity
Annually
Focus on monitoring and managing
of the lake’s aquatic vegetation community, and continuing the current
nuisance species, including Eurasian
water quality monitoring program.
watermilfoil and curlyleaf pondweed
(2) Management activities should include regular assessments of
Ongoing
Focus future restoration and
monitoring data to identify consistency or shifts in trends.
management efforts on storm water
management and on rough fish
control (bullhead, carp)
St. Joe
Continue to implement the activities specified in the Lake Management Monitor and maintain native aquatic
Ongoing
Plan. Notable activities include: monitoring phosphorus levels and native vegetative coverage at 40 percent or
vegetation and continuing Secchi disc water clarity readings. greater.
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C.Creeks and Linear Waterways
In addition to the rich abundance of wetlands, Chanhassen has several significant waterways. As
part of the wetland inventory, all linear waterways were mapped to complete the comprehensive
overview of the City’s resources. Linear waterways include the major streams and creeks, but
also include some of the ditches, grassed swales, and other areas designated for conveyance of
surface waters. Many waterways flow through wetland areas. In these portions, the channel has
not been mapped, but is contained within the wetland boundary. The channels have been mapped
for those portions not located within a wetland, i.e. those areas that flow through an upland area.
Mapping was done with both GPS and through aerial photograph interpretation.
The RPBCWD Water Management Plan (RPBCWD Plan) provides Physical and Ecological Use
Classifications of Purgatory, Riley and Bluff Creeks. The classification system for physical
classification is the David L. Rosgen system. According to the RPBCWD Plan, this system
describes a stream on a reach-by-reach basis, and therefore one stream can have several different
stream types. The stream type is defined by the shape, pattern, and profile of the reach. Please
see Figures PC1 and PC2 in Appendix E for an illustration of these parameters. Please refer to
the RPBCWD Plan for more information on the classification methodology.
According to the RPBCWD Plan, the classification system used for ecological classification of
Purgatory, Riley and Bluff Creeks is based on procedures that have been developed by the
Wisconsin Department of Natural Resources (WDNR). The purpose of these procedures is to
provide a scientific method for designating uses according to a stream’s natural ability to support
a certain biological community. Please see Tables EUC1 and EUC2 in Appendix E for the
criteria used in the ecological classification of Purgatory, Riley and Bluff Creeks. Please refer to
the RPBCWD Plan for more information on the classification methodology.
A summary description of some of the major waterways within the City is provided in the
following sections.
1.Assumption Creek
Assumption Creek is a tributary of the Minnesota River. It begins just northwest of the
Assumption Seminary property and empties into the Minnesota River after flowing through the
Raguet Wildlife Management Area, west of Highway 101 and south of Highway 212 in
Chanhassen. The creek is Carver County’s only remaining native trout stream. It is one of only
15 streams in the metro area that still supports trout populations. Additionally, it is one of the
few streams in the metro area that supports native brook trout instead of non-native brown trout.
Assumption Creek is also closely associated with Seminary Fen, another critical resource, and
extensive wetland along the Minnesota River. Property and storm water management practices
have compromised the integrity of stream banks and riparian areas. The entire Assumption Creek
drainage area is unique and deserves additional protection.
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2.Bluff Creek
Bluff Creek is the most significant waterway within the City. Bluff Creek has several tributaries
which originate in large wetlands in the north central portion of the City. Wetlands 10-116-23-
09-019 and 10-116-23-16-005 are the origin for the biggest tributaries of the creek.
Approximately 20% of Bluff Creek flows through wetland, which is a low proportion compared
to other creeks in the City. The northern third of the creek flows mostly through larger wetlands
and recently developed residential areas. The middle third of the creek is less developed and has
much more agricultural land use. The final third of the creek, before it discharges into the large
wetland along the Minnesota River, is undeveloped and is a sensitive bluff area. This final third
of the creek has few wetlands, but is a critical natural resource for sensitive bluff species. There
are several extensive public walking trails through the Bluff Creek corridor, and these trails are
integral to the future health of the corridor.
Two significant escarpments exist in the lower section of Bluff Creek. These cliffs are quite
spectacular in their size and form, but could create serious land management issues in the future.
There is also a strong likelihood that the meandering process of Bluff Creek will reroute the
creek away from the base of these cliffs, slowing the erosion of their face walls.
The RPBCWD Plan physically classifies five reaches of Bluff Creek. Most of the creek consists
of C and E stream type, with some portions of type B and type F. The RPBCWD Plan states that:
Improving the physical characteristics of Bluff Creek where necessary will improve the
ability of the stream to convey surface waters without eroding and also improve the
ecological characteristics and aesthetics of the stream.
Problems are described as follows:
B2 – Bank stability problems were observed, this is due partly to wet clay soils
o
and change in gradient
B3 – Loss of meandering due to straightening and grazing was observed
o
B4 – This reach is likely a degraded C stream type, resulting from the upstream
o
railroad culvert and downstream channel straightening.
The ecological classification for Bluff Creek is mostly Ecological Use Class D and E, according
to the RPBCWD Plan. Habitat improvement in the downstream portion of Bluff Creek will result
in an ecological use classification change from Class D to Class C. The RPBCWD Plan states
that the ecological use of Bluff Creek is limited by its low flow and habitat conditions, but the
stream provides habitat for many species of aquatic life. The RPBCWD Plan’s main
recommendation for preserving Bluff Creek as a valuable resource is to preserve a corridor of
undeveloped land along Bluff Creek and preserving the biotic integrity of the stream.
The 1994 Plan identified a list of proposed storm water ponds within the Bluff Creek
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
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were inventoried as part of the most recent wetland inventory. Table 32 is a summary of the
proposed storm water ponds in the Bluff Creek subwatershed.
Table 32. Bluff Creek Subwatershed Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
First Improve-1 BC-P4.11
BC-P2.13, BC-P4.12,
Third Improve-1 BC-P5.11, BC-P6.19,
BC-P7.9
BC-P4.6, BC-P5.2,
Fourth Improve-1
BC-P5.6, BC-P6.5
BC-P1.8, BC-P4.1,
Fifth Improve-1 BC-P5.1, BC-P5.13,
BC-P6.16
BC-P6.1, BC-P6.2,
Sixth Improve-1
BC-P7.4
Seventh Improve-1 BC-P1.2, BC-P1.12
BC-P5.3, BC-P6.10,
Eighth Improve-1 BC-P6.11, BC-P6.12,
BC-P6.15
3.Lake Minnewashta Outlet
Although mostly flowing through wetlands, there is an unnamed channel that acts as the outlet
for Lake Minnewashta and flows into Lake Virginia outside the City limits. Most of the channel
is in wetlands or flows through created ditches in front of several single family residential lots.
This unnamed stream is within the Minnehaha Creek watershed and discharges into the
Mississippi River drainage rather than the Minnesota River.
The 1994 Plan identified a list of proposed storm water ponds within the Minnewashta Oulet
Creek subwatershed. The table in Appendix I lists all recommended storm water ponds from
Table III-D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended
pond from the 1994 Plan has been constructed. The table also includes all new storm water
ponds that were inventoried as part of the most recent wetland inventory. Table 33 is a summary
of the proposed storm water ponds in the Minnewashta Outlet Creek subwatershed.
Table 33. Minnewashta Outlet Creek Subwatershed
Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
First Improve-2 MC-P2.6
Second Improve-2 MC-P3.3
Third Improve-2 MC-P2.9
Fifth Improve-2 MC-P3.4
Seventh Improve-2 MC-P4.2
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4.Purgatory Creek
Purgatory Creek originates as the outflow of Lotus Lake and is only within the City of
Chanhassen through less than 1,000 feet of floodplain forest and a controlled outlet.
According to the RPBCWD Plan, the physical classification for Purgatory Creek in the reach
that’s located within Chanhassen is a Type C Channel. The RPBCWD Plan states that there was
some loss of meandering observed at the reach located in Chanhassen. The RPBCWD Plan also
states that the existing ecological use for Purgatory Creek within Chanhassen is Ecological Use
Classification E. This is also the attainable ecological use class.
The 1994 Plan identified a list of proposed storm water ponds within the Purgatory Creek
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
were inventoried as part of the most recent wetland inventory. Table 34 is a summary of the
proposed storm water ponds in the Purgatory Creek subwatershed.
Table 34. Purgatory Creek Subwatershed Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
First Improve-1 PC-P1.4
Third Improve-1 PC-P1.6
Fourth Improve-1 PC-P1.5
5.Riley Creek
Riley Creek is the second longest waterway in the City. Riley Creek flows through many
wetlands and lakes and has less than 10% of the channel not associated with a surface water
body or wetland. Riley Creek starts in Lake Lucy and flows south through a small channel to
Lake Ann, through a wooded channel to a service road and Trunk Highway 5 crossing. South of
TH 5, Riley Creek flows through several wetlands and floodplain forest areas to Lake Susan and
then Rice Marsh Lake before leaving the City.
According to the RPBCWD Plan, four reference reaches of Riley Creek were physically
classified. Most of the creek consists of type C and E stream, with some portions of type B
stream. The RPBCWD Plan states that:
Improving the physical characteristics of Riley Creek where necessary will improve: (1)
the ability of the stream to continue to naturally meander without eroding bank areas, and
(2) the ecological characteristics and aesthetics of the stream.
Observations of problems at particular reference reaches are described as follows:
R1 – Stream bank erosion and slumping was observed; this is due to the natural
o
meandering of the stream impinging upon the steep valley walls.
R2 – Channel downcutting was observed due to an upstream culvert concentrating
o
overbank flows through the narrow valley.
R4 – Bank erosion and bed degradation due to upstream channel straightening.
o
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The ecological classification for Riley Creek is mostly Ecological Use Class D, with a small
portion of Ecological Use Class E, according to the RPBCWD Plan. The attainable habitat
improvements for ecological use in this stream are related to attainable changes in the physical
stream conditions. The RPBCWD Plan identifies the following habitat improvements that can be
attained by solving the creek’s bank erosion and slumping problems in the downstream reaches:
Reduced watershed erosion
Reduced bank erosion
Improved bank erosion
Reduced lower bank deposition
Less bottom deposition
Improved bottom substrate and available cover
Improved depth in riffles/runs and pools.
By attaining these habitat improvements the ecological use classification will change from
Class E to Class C. Please refer to the RPBCWD Plan for more information regarding the
physical and ecological use classification for Riley Creek.
6.Unnamed Creek – Southeast Bluff Area:
The last significant creek in Chanhassen is a short unnamed channel in the southeast portion of
the City. Like Bluff Creek, this channel flows through a largely undeveloped area of the bluffs.
This area hasn’t been identified as having the same critical resources as Bluff Creek has, but
similar habitats and erosion control concerns warrant a similar level of protection.
The City currently has setback requirements and restrictions on land use along the creeks. It is
recommended that these existing requirements continue to be enforced and that additional
requirements be evaluated for the sections of the creeks flowing through the bluff areas.
Continued implementation of the current policies is likely sufficient, but additional action may
be needed to preserve the most critical natural resources.
7.Minnesota River
The Minnesota River forms the southern boundary of Chanhassen. The wetlands along the river
bottom are protected by the Raguet Wildlife Management Area and the Minnesota Valley
Wildlife Refuge.
The 1994 Plan identified a list of proposed storm water ponds within the Minnesota River
subwatershed. The table in Appendix I lists all recommended storm water ponds from Table III-
D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended pond
from the 1994 Plan has been constructed. The table also includes all new storm water ponds that
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were inventoried as part of the most recent wetland inventory. Table 35 is a summary of the
proposed storm water ponds in the Minnesota River subwatershed.
Table 35. Minnesota River Subwatershed Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
First Preserve LOM-P1.12
Second Preserve LOM-P1.4
Fourth Preserve LOM-P1.3, LOM-P1.8
LOM-P1.1, LOM-
Fifth Preserve
P1.11
Seventh Preserve LOM-P1.6
Eighth Preserve LOM-P1.5
D.Storm Water Ponds
In addition to the wetland basins mapped as part of the 2006 wetland inventory field work, all of
the storm water ponds in the city were mapped. Of these, 57 were included with the MnRAM
analysis as they were part of the 1992 inventory, or were inadvertently included. Most storm
water ponds are open water and would be classified as Type 4 or Type 5 wetlands. Some of the
ponds, especially those in the older parts of the city, have significant areas of emergent
vegetation and are comparable to a Type 3 wetland. In total, storm water ponds make up 72
acres within the city. Because storm water ponds were created with a specific purpose of
treating runoff, they are classified as “Constructed” in this Plan, regardless of what the results of
the MnRAM analysis shows. Several of the storm water ponds have wetland characteristics
consistent with wetland classified as Manage 1 or Manage 2 if they followed the MnRAM
results. Historically, natural wetlands were used for storm water treatment, either through
restricting outflows, or excavating wetlands to create additional open water areas and storage
volume. While this practice has since been discouraged, many of the storm water ponds,
particularly in the northeast portion of the city, were likely wetlands that have been converted.
These ponds would still be classified as wetlands under current wetland regulations, and could be
subject to replacement if impacted for more than routine maintenance. Even if an area was
formerly wetland, however, its current function is storm water treatment, and therefore will be
classified as “Constructed”. Many of these basins were identified as “Utilized” in the 1994 Plan.
For more information on the wetland classification system, see Section V of this Plan.
E.Drainage to Subwatersheds Outside of Chanhassen
A portion of the City of Chanhassen drains to surface waters located outside the City boundaries.
A small are of the City in the far east side of the City drains to Mitchell Lake, which is located
within the City of Eden Prairie. Another small portion of Chanhassen in the south central part of
the City drains to Lake Hazeltine, which is located within the City of Chaska.
The 1994 Plan identified a list of proposed storm water ponds within the Mitchell Lake and Lake
Hazeltine subwatersheds. The table in Appendix I lists all recommended storm water ponds from
Table III-D1 in the 1994 Plan. The table in Appendix I identifies whether or not a recommended
pond from the 1994 Plan has been constructed. The table also includes all new storm water
ponds that were inventoried as part of the most recent wetland inventory. Tables 36 and 37 are a
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summary of the proposed storm water ponds in the Mitchell Lake and Lake Hazeltine
subwatersheds.
Table 36. Mitchell Lake Subwatershed Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
Third Improve-3 ML-P1.2
ML-P1.1, ML-P2.1,
Eighth Improve-3
ML-P2.2
Table 37. Lake Hazeltine Subwatershed Proposed Ponds Prioritization
1994 Plan Priority
2006 Water Management Class Pond Label
Ranking
Seventh Improve-3 LH-P1.1
LH-P1.4, LH-P1.6,
Eighth Improve-3
LH-P1.8, LH-P1.9
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V.WETLANDS MANAGEMENT
A.Overview
The City has a wealth of natural resources including 12 lakes, 356 wetlands, and the origin of
several major stream drainages including Bluff Creek, Riley Creek, and Purgatory Creek. The
city also has some very sensitive aquatic resources such as Assumption Creek, Seminary Fen,
and the wetlands associated with the Minnesota River. This section of the SWMP has been
dedicated to describe the wetlands within the city and identifying measures to classify and
provide adequate protective measures to them. In 1992, the City updated its wetland inventory
and assigned management classifications and identified other details of interest on wetlands. The
intent or use of a wetland was to be considered in its classification. The inventory has been
updated and a MnRAM Version 3.0 assessment has been completed on 315 of the wetlands as
part of this Plan update. The 41 basins not included with the functions and values assessment wer
located on private property and could not be reached, or were new basins that were identified by
aerial photograph review after completion of the field review.
The majority of the wetlands within the City are shallow marshes or wet meadow wetlands.
These two wetland types make up approximately 68% of the total number of wetlands and 88%
of the total wetland area of the City. Much of this is due to the extensive shoreland wetlands and
those along the Minnesota River. Cumulatively, wetlands total 2,370 acres within the City
limits, which is approximately 15% of the total area of the City. Storm water ponds account for
an additional 78 acres of aquatic habitat. Lakes compose a significant portion of the City, with
the 12 mapped lakes comprising 1,526 acres. Cumulatively, surface water features (lakes,
wetlands, streams and ponds) account for 3,975 acres of the City’s surface area. As stated
previously, water features represent approximately 26% of the City’s surface area.
The wetlands portion of the SWMP is intended to provide a plan for the protection and
management of the City’s wetland and associated natural resources. This plan has been
developed in accordance with the Wetland Conservation Act guidelines (MN Rules 8420.0650),
although it is not currently intended to be used as a Comprehensive Wetland Management Plan.
The information contained within this section of the Plan will allow the City to protect and
manage their wetland resources and provide protection beyond that already provided by the
WCA or the local watershed districts and management organizations.
The primary objectives of this section of the SWMP are to:
Identify all of the wetlands within the city through the completion of a wetland inventory;
Complete a functions and values analysis on all wetlands within the city;
Prioritize wetland regulations based on the functions and values of the basin;
Identify the status and trends of wetlands in the city since the 1992 inventory was
completed;
Manage wetland resources with the intention of improving functions and values;
Identify short term and long-term management strategies;
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Provide data on the wetlands in the city to residents and developers; and
Identify restoration opportunities.
Field assessments of the wetlands presented in this Plan are not delineations of the inventoried
wetlands. Delineations are performed prior to development of individual sites or for identifying
mitigation and restoration opportunities.
B.Existing Wetland Regulations
Although one of the main purposes of the SWMP is to allow the City to regulate and manage
their water resources, including wetlands to some degree, there are several layers of protection
already in place. These regulations may be implemented at the state, local, or federal level, and
can come from a variety of agencies and organizations. The following are summaries of some of
the main agencies and organizations that may be encountered.
1.Minnesota Wetland Conservation Act
The WCA was first passed in 1991 and has been subsequently amended as the Act has evolved.
The Board of Water and Soil Resources (BWSR) is the lead agency for administering the WCA,
and its guidelines are published in Minnesota Rules 8420. The intent of the WCA was to achieve
no net loss of wetlands in the state. This is achieved by regulating the filling, draining,
excavation, and alteration of wetlands within the state. There are some notable exemptions, such
as allowing temporary impacts, farming of wetlands, and allowing small impacts to occur (de
minimis). If an activity cannot avoid impacts and certain thresholds of impacts are met, creation
of new wetland, or restoration of an altered or drained wetland must occur.
The WCA is administered by the Local Government Unit (LGU), which is the City of
Chanhassen for all areas within the city limits. This authority, within the rules of the WCA,
allows the city to regulate wetland impacts and replacement criteria. The city is assisted with the
administration of the WCA by a Technical Evaluation Panel (TEP). The TEP is comprised of
the LGU, plus representatives of the BWSR, the County Soil and Water Conservation District
(SWCD), and the Minnesota Department of Natural Resources (MNDNR). Other agencies and
experts may be invited to attend TEP meetings, but are not voting members.
2.Minnesota Department of Natural Resources
The Minnesota Department of Natural Resources has regulatory authority of Protected Waters
and Protected Water Wetlands, which are identified on the Protected Waters Inventory.
Protected Waters and Protected Water Wetlands can be lumped together as Public Waters.
Regulatory authority is to all areas below the Ordinary High Water (OHW) elevation of ponds
and lakes and any area below the top of bank for rivers and streams. If an OHW has not been set,
which is often the case for Protected Water Wetlands, the jurisdiction will be the delineated
wetland edge. Within the city, there are 27 listed protected waters and wetlands and five
waterways (see Figure 6). These basins are identified on the City’s GIS database and are also
available for viewing at the MNDNR’s website (http://www.dnr.state.mn.us/waters/
watermgmt_section/pwi/maps.html). Work below the OHW or within the channel of a Protected
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Water may require a permit from the MNDNR. Water appropriations may also require permits
depending on the rate and amount of water used. Wetlands are regulated by the Area
Hydrologist.
3.United States Army Corps of Engineers
The USACE regulates filling and excavation of wetlands through Section 404 of the Clean Water
Act. It also regulates impacts to navigable waters through Section 10 of the Rivers and Harbors
Act. The USACE has regulatory authority over any navigable water, and any wetlands
hydrologically connected or adjacent to them. Currently, the USACE does not have the authority
to regulate isolated wetlands, although there are very few basins in Chanhassen that would be
considered isolated under current guidelines. Any impacts, including filling, dredging, or
excavation may require a permit from the USACE. Additionally, the USACE also approves
wetland delineations, and can participate on a Technical Evaluation Panel. Permitting is
conducted through the regulatory branch, and agents are identified on a by county basis. More
specific information of the USACE regulatory process can be found at their website
(www.mvp.usace.army.mil).
4.Watershed Management Organizations
Within the city limits are four water management authorities including the Minnehaha Creek
Watershed District (MCWD) (http://www.minneahahacreek.org), the Riley Purgatory Bluff
Creek Watershed District (RPBCWD) (http://www.rileypurgatorybluffcreek.org), the Lower
Minnesota River Watershed District (LMRWD) (http://www.watersheddistrict.org), and the
Carver County Water Management Organization (CCWRMO)
(http://www.co.carver.mn.us/water). These organizations may have additional regulatory
requirements which must also be complied with for both the surface water and wetland
components of the SWMP.
C.2006 Wetland Inventory
Mapping of the wetlands within the City of Chanhassen was started in the fall of 2004 and
continued through the growing season in 2005. The intention of this wetland inventory was to:
Update the inventory completed in 1992 by revisiting those basins
Revisit those basins identified on the inventory and evaluate the functional assessment
completed by the Minnehaha Creek Watershed District in 2003
Identify any new wetlands not identified in the 1992 inventory
Map any of the linear waterways and streams that were not within a wetland
Map all of the storm water ponds to differentiate them from wetlands
The wetland inventory identified and mapped a total of 171 storm water treatment basins or other
excavated ponds, which have a total area of approximately 78 acres. The total number of basins
includes 57 treatment ponds that were part of the 1992 inventory and 114 basins that have been
created since 1992 or were not included in the previous inventory. Storm water ponds are not
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part of the wetland inventory, but were mapped to provide a designation for all of the ponds and
wetlands in the city. Many of the storm water ponds, particularly those 57 that were part of the
1992 inventory, may have been wetland that was excavated and converted into storm water
ponds. Storm water ponds that were created from wetlands are still under the jurisdiction of the
WCA. Storm water ponds that may have been wetland previously have not been separated from
those clearly created from upland. Figure 9 identifies all of the storm water ponds and identifies
those that were present in the 1992 inventory and those created afterward. Basins that were
included in the 1992 inventory may require further investigation to determine if they were
formerly wetland. All other basins have been confirmed to have been built in an upland area,
and would not be regulated under the WCA or would be considered incidental basins.
1.Methods
The wetland inventory was completed by observing and identifying each basin in the field during
the growing season. At each basin, notes on wetland vegetation, wetland type, amount of open
water, control structures, and any other observation were taken in a dedicated field notebook.
Field work was facilitated by using a Trimble GeoXT Global Positioning System (GPS). The
GPS unit was preloaded with rectified aerial photographs from 2000 and 2003, which allowed
both efficient navigation and the ability to locate basins that were not visible from public
roadways.
Whenever possible, wetlands were directly observed in the field as opposed to interpretation
using off-site resources. Wetland boundaries were noted electronically on the rectified aerial
photographs on the GPS unit, and accompanied by detailed field notes. When practical, all or
part of the wetland boundary would be recorded directly using GPS. Approximately 75% of the
wetlands mapped had at least one GPS location recorded along the wetland boundary.
Approximately 30% of all the wetland boundaries were mapped using GPS, with the remainder
being interpreted using recent aerial photographs. Although only a small portion of the wetlands
were mapped directly, this allows much greater accuracy than using aerial interpretation alone.
This allows small wooded basins, wooded fringes, and floodplain forests to be mapped
accurately where tree cover completely obscures the wetland signature. This also allows a
partially mapped boundary to establish a wetland signature that can be used to more accurately
photo interpret the remaining boundary.
It is important to clarify that although portions of the wetlands have been mapped on the ground,
this does not constitute a wetland delineation. A wetland delineation, as set forth in the 1987
Manual for Delineating and Identifying Jurisdictional Wetlands (U.S. Army Corps of Engineers,
1987), requires documentation of wetland hydrology, hydric soils, and hydrophytic vegetation.
The current inventory is based only on visual observation of the basins, and therefore is based
primarily on hydrophytic vegetation. Because of this, the boundaries in the wetland inventory
are not sufficient and cannot be substituted for a jurisdictional wetland delineation. As required
by ordinance and the Wetland Conservation Act, a wetland delineation must be completed if any
work is proposed to occur in or near one of the inventoried basins. It is also worth pointing out
that, although considerable effort has been made to locate and identify all the basins within the
city, there is a possibility that some wetlands have been missed. The absence of a wetland on a
given property, based on the results of the wetland inventory, does not necessarily mean that
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there is no wetland present, nor does it obviate developer investigation and/or observation of
wetlands on a site.
2.Inventory Data Format and Information
In the office, the field notes, sketches, and GPS data were used to digitize the wetland boundaries
over the aerial photographs. Several data fields were created that provide information on the
basin. The following fields were prepared for each basin:
2005 SWMP ID:
This is the unique number for the basin for the current wetland inventory. This
number is derived from the format of the Minnesota Routine Assessment Method 3.0, which is
used to complete the functions and values assessment. The number is based on the location of a
wetland and is composed of a two digit county identification number, three digit Township
number, two digit Range number, two digit Section number, a unique number for each basin
within a section, and finally a numeric code representing whether this is the first, second, third,
or future assessment of the wetland.
Original Wetland Inventory No.:
The identification code for the basin from the 1992
inventory. This older inventory number is based on the section the wetland occurs in and the
location within that section. The last portion of the code is a letter which may be P, N, A, or U.
These stand for Pristine, Natural, Ag/Urban, or Utilized, and are the basis for the regulations
used in the ordinances prior to the currently recommended revisions.
Map Sequence:
Order in which the basins were digitized. This is independent of the order the
field work was completed, and is only used for QA/QC.
Wetland Type:
The Circular 39 classification of the basin. Most wetlands are composed of
more than one wetland type, but an effort has been made to classify the basin with the most
dominant wetland type, with preference toward the deeper water habitats. Multiple wetland
types are used occasionally when there is no clearly dominant wetland type. For example a basin
that is 70% cattails, 20% reed canary grass and 10% wooded fringe would be classified as a Type
3 only. A basin that is 60% cattail marsh and 40% shallow open water would be classified as
Type 3/4. Wetlands can be classified as Type 1 through Type 8.
The eight possible wetland types are as follows:
Type 1 Seasonally Flooded Basins or Floodplains:
Type 1 wetlands are seasonally flooded
basins or flats in which soil is covered with water or is waterlogged during variable seasonal
periods but usually is well-drained during much of the growing season. Type 1 wetlands are
located in depressions and in overflow bottom lands along water courses. Vegetation varies
greatly according to the season and duration of the flooding, and includes bottom land
hardwoods, as well as herbaceous plants.
Type 2 Wet Meadow:
Occurs along the shallow edges of lakes, marshes and floodplains, or
in perched depressions. The soil is usually without standing water during much of the
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growing season, but is waterlogged within at least a few inches of the surface. Vegetation
includes grasses, sedges, rushes and various herbaceous plants.
Type 3 Shallow Marsh
: Soil is usually water logged during the growing season, often
covered with as much as six inches or more of water. Vegetation includes grasses, bulrushes,
cattails, arrowheads, smartweeds and other emergent aquatic vegetation.
Type 4 Deep Marsh:
Soil covered with six inches to three feet or more of water during
growing season. Vegetation includes cattails, reeds, bulrushes and wild rice. Open water
areas may contain pondweeds, naiads, coontail, water milfoils and other submergent aquatic
vegetation.
Type 5 Open Water:
Water is usually less than 10 feet deep and is fringed by a border of
emergent vegetation. Vegetation includes pondweeds, naiads, coontail, water milfoils and
other submergent aquatic vegetation.
Type 6 Scrub shrub:
Occurs along sluggish streams or on floodplains. The soil is usually
waterlogged during the growing season, and is often covered with as much as six inches of
water. Vegetation includes alder, willow, and dogwood.
Type 7 Wooded Swamp:
Occurs along sluggish streams, on floodplains, on flat perched
depressions and in shallow lake basins. The soil is waterlogged to within a few inches of its
surface during the growing season and is often covered with as much as one foot of water.
Vegetation typical to this wetland includes tamarack, white cedar, black spruce, balsam fir,
red maple and black ash.
Type 8 Bog:
Occurs along sluggish streams, on flat perched depressions and shallow lake
basins. The soil is waterlogged and supports a spongy covering of mosses. Vegetation typical
to this wetland type includes sphagnum moss, heath shrubs and sedges. Minnesota bogs
contain leatherleaf, Labrador tea, cranberries and pitcher plants. Scattered stunted black
spruce and tamarack also are common features of bogs.
Cowardin (NWI) Classification:
This classification system is used by the National Wetlands
Inventory (NWI) and is based on a tiered system. The NWI system is illustrated in Figure 10.
This system identifies a wetland based on hydrology and vegetation composition, plus any
special modifiers. The hierarchical structure progresses from Systems and Subsystems at the
most general levels to Classes, Subclasses, and Dominance Types at the most specific levels. A
comparison of Circular 39 and Cowardin wetland classifications along with the typical Cowardin
classification symbols are provided in Table 38.
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Table 38. Circular 39 and Cowardin Classification System Summary
SYSTEM
Circular SUBSYSTEM Typical NWI
39 Type CLASS Common Water Regimes Symbols
SUBCLASS (Cowardin System)
Type 1 PALUSTRINE (P) Temporarily Flooded (A) PEM1A
Emergent (EM) Intermittently Flooded (J) PEM1J
Persistent (1) PFO1A
Forested (FO) PFO1J
Broad-Leaf Deciduous (1)
Type 2 PALUSTRINE (P) Saturated (B) PEM1B
Emergent (EM)
Persistent (1)
Type 3 PALUSTRINE (P) Seasonally Flooded (C) PEM1C
Emergent (EM) Semipermanently Flooded (F) PEM1F
Persistent (1)
Type 4 PALUSTRINE (P) OR LACUSTRINE (L) Semipermanently Flooded (F) PEMF L2EM2F
Littoral (2) Intermittently Exposed (G) PEMG L2EM2G
Emergent (EM) Permanently Flooded (H) PABF L2EM2H
Aquatic Bed (AB) PABG L2ABF
Unconsolidated Bottom (UB) PUBF L2ABG
PUBG L2ABH
Type 5 PALUSTRINE (P) OR LACUSTRINE (L) Intermittently Exposed (G) PABG L2ABG
Limnetic (1) Permanently Flooded (H) PABH L2ABH
Littoral (2) PUBG L2UBG
Aquatic Bed (AB) PUBH L2UBH
Unconsolidated Bottom (UB)
L1UBH
Type 6 PALUSTRINE (P) All nontidal regimes except PSS1,2,3,4, or 5A
Scrub-Shrub (SS) Permanently Flooded PSS1,2,3,4, or 5B
Broad/Needleleaf Deciduous (1,2) (A,B,C,F,J,G) PSS1,2,3,4, or 5C
Broad/Needleleaf Evergreen (3,4) PSS1,2,3,4, or 5F
Dead (5) PSS1,2,3,4, or 5J
PSS1,2,3,4, or 5G
Type 7 PALUSTRINE (P) All nontidal regimes except PFO1,2,4, or 5A
Forested (FO) Intermittently Flooded and PFO1,2,4, or 5B
Permanently Flooded (A,B,C,F,J) PFO1,2,4, or 5C
PFO1,2,4, or 5F
PFO1,2,4, or 5J
Type 8 PALUSTRINE (P) Saturated (B) PSS1,2,3,4, or 5B
Scrub-Shrub (SS) PFO1,2,3,4, or 5B
Broad + Needleleaf Deciduous (1,2) PMLB
Broad + Needleleaf Evergreen (3,4) PEMB
Dead (5)
Forested (FO)
Broad + Needleleaf Deciduous (1,2)
Broad + Needleleaf Evergreen (3,4)
Dead (5)
Moss-Lichen (ML)
Emergent (EM)
RIVERINE (R) Intermittently Exposed (G) RUBG
Lower Perennial (LP) Permanently Flooded (H) RUBH
Upper Perennial (UP)
Intermittent (IN)
Unconsolidated Bottom (UB)
Wetland Type Description:
This is a text description of the wetland type and follows the same
naming convention as the Circular 39 description. The wetland types that were found in the
inventory where classified as one of nine possible types including: Seasonally flooded basin,
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wet meadow, shallow marsh, deep marsh, open water, scrub shrub, wooded swamp, stream, and
floodplain forest.
General Classification:
This is a general category of a basin which allows for additional
description of the basin than allowed by just using wetland types. This category helps to identify
special basins that are less commonly observed, such as wooded swamps, and those that may
have additional protection, such as mitigation areas. The following general classifications are
provided:
Farmed Wetland: A wetland that is used for agricultural production. Farmed wetlands
must be disturbed and actually used for production, not just be in an agricultural setting.
The WCA allows for agricultural exemptions, and unique wetland mitigation
opportunities for these unique basins.
Floodplain Forest: Wooded wetlands associated with forests and supported
hydrologically by flooding. Most of these are along the creeks in the city, although some
are supported by ephemeral streams and storm water runoff.
Mitigation Area: Any wetland area created or restored for compensatory mitigation under
the WCA.
Shoreland Wetland: Wetland, typically cattail marshes or other shallow emergent
vegetation, that is directly associated with one of the lakes. Many of the shoreland
wetlands are below the ordinary high water elevation and are regulated by the MNDNR
and USACE, not the WCA.
Wetland: Any wetland, regardless of type, that doesn’t fall into one of the other
categories.
Wooded Swamp: Wetland dominated by trees but is not a floodplain forest.
Significant Changes:
This is a quick measure of whether a basin has changed significantly
from the 1992 inventory. A ‘no’ indicates that the basin is relatively unchanged in both area and
wetland type. A ‘yes’ indicates that either the wetland has changed in size or shape, in wetland
type, merged or divided, or wasn’t previously mapped.
Storm Water Pond ID:
The identification number assigned to a wetland in the 1994 surface
water plan.
MNDNR PWI:
The identification code used by the Minnesota Department of Natural
Resources Protected Water Inventory. If an identification number is provided, that basin is under
the regulatory authority of the MNDNR.
McRAM ID:
Identification code of a basin that was inventoried and classified by the
Minnehaha Creek Watershed District study. This only includes basins with the Lake
Minnewashta and Christmas Lake watersheds.
Comments:
Brief text description of the basin including notes of flow, structures, and
disturbances.
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Acres:
The size of the basin in acres.
Area:
The size of the basin in square feet.
Perimeter:
The linear distance of the wetland boundary.
Classification:
The results of the MnRAM analysis after being processed through the “Basic”
level of protection matrix as described in Section E below. This may be Preserve, Mange 1,
Manage 2, Manage 3, or Undetermined. Undetermined indicates that the MnRAM assessment
was not completed for that Basin.
3.Inventory Results
The wetland inventory identified a total of 356 wetlands which are illustrated in Figure 12. The
inventory also resulted in a GIS mapping of all of the storm water treatment ponds, lakes, and
water courses that were not within wetlands. The wetland inventory focuses on the wetlands, but
a brief discussion of the lakes and major water courses and how all of the City’s aquatic
resources are related, is worthwhile. The following sections describe the results of the wetland
inventory, but also include a brief discussion of the lake a stream resources.
a.Wetlands
The 356 mapped wetland basins shown in Figure 12 have been divided into classifications based
on the results of the MnRAM analysis (described in Section D below). In addition to this
classification, the wetlands can be divided and described by wetland type. Table 39 provides a
summary of the results based on the general wetland classification. Following the table is a
general description of the classifications identified, along with the rationale for inclusion of that
category.
Table 39. Wetland Classification Summary
Number Total Area
Classification
of Basins (acres)
Farmed Wetlands 13 8.10
Floodplain Forest 11 9.75
Mitigation Areas 12 5.82
Shoreland Wetland 20 296.97
Stream 3 0.64
Wetland 291 2046.88
Wooded Swamp 6 1.14
Total 356 2669.84
Farmed Wetlands:
Farmed wetlands are usually highly disturbed and are almost always
classified as Manage 3. Farmed wetlands also have some of the best opportunities for
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wetland restoration, application of agricultural exemptions, and ways of getting mitigation or
wetland banking credits not eligible to non-farmed basins.
Floodplain Forest:
In addition to being wooded wetlands, which are relatively rare already,
floodplain forests are associated with waterways and have unique ecological functions.
Mitigation Areas:
Mitigation areas are created wetlands and are placed under protective
easements. Because of the additional protection and high standards for native vegetation and
buffers, these areas are automatically classified as Preserve. Wetland mitigation areas are
also protected from future impacts without significant justification. For this reason, impact
avoidance for these basins is critical.
Shoreland Wetlands:
Shoreland wetlands are unique in that they serve as a transition
between the aquatic and wetland or terrestrial habitats. Most shoreland wetlands are used for
fisheries habitat and also have high recreational and aesthetic functions and values. Most
shoreland wetlands rank as Manage 1.
Stream:
The stream feature is essentially the same as the linear feature, but has been
inventoried in the past and is therefore included as a polygon. The stream feature is limited
to a small portion of the unnamed channel leading from Lake Minnewashta to Lake Virginia
Wetland:
The wetland classification covers all other wetland types not already specified.
This classification includes the most common basins such as wet meadows, shallow marshes,
deep marshes, and shallow open water. Wetlands will rank in all of the management
classifications, but the majority are Manage 2.
Wooded Swamp:
The wooded swamp designation includes small woodland basins
dominated by tree cover. In Chanhassen these basins tend to be small, ephemeral, and
sensitive to disturbance. Wooded swamps generally have higher quality and most are
Manage 1.
Collectively, the less common wetland types comprise 18 % of the wetlands in the city.
Removing the shoreland wetlands from this total, as they are separated only due to their
shoreland zoning criteria, and the less common wetlands only comprise 13% of the total number
of basins and less than 1% of the total wetland area. These numbers demonstrate how
uncommon some of these wetland types are. Identification of these rare basins as separate
categories helps to highlight them when they might otherwise be hidden by the majority.
Another common analysis of wetlands is by wetland type. Wetland type is based on a
combination of hydrology and vegetation, and can be one of eight types as previously described.
Wetland typing is often difficult, as most basins have more than one type present. For this
comparison, the dominant wetland type has been used to identify the basin as a single type. In
cases where the basin is roughly equal areas of more than one wetland type, the deepest
hydrologic designation is given preference. Table 40 shows the distribution of wetlands based on
wetland type.
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The most common wetland type in the city is a shallow marsh. Shallow marshes are typically
dominated by cattails and occur as isolated basins and along the lake shores. The second most
common wetland type is the wet meadow. This can include sedge meadows, but most often wet
meadows are dominated by reed canary grass, particularly in agricultural or disturbed areas.
Type 6 basins are very rare in the city. Type 6 basins are typically dominated by shrubs,
typically willows or alders. While only two basins were inventoried that would be considered to
be Type 6, many basins have a small type 6 component. Type 6 wetland isn’t as uncommon as
suggested, but it is rare for that wetland type to comprise more than 20% of any given basin.
Table 40. Summary of Basins Based on Wetland Type
Wetland Number Total Area
Description
Type of Basins (acres)
Type 1 Seasonally Flooded 21 13.355
Type 2 Wet Meadow 94 547.18
Type 3 Shallow Marsh 131 1464.86
Type 4 Deep Marsh 52 154.95
Type 5 Shallow Open Water 11 125.92
Type 6 Scrub Shrub 2 0.42
Type 7 Wooded Swamp 24 8.91
Total 335 2315.61
b.Lakes
Twelve lakes were mapped as part of the wetland inventory. Mapping of the lakes was based on
the extent of emergent vegetation, not the Ordinary High Water elevation. This was chosen as it
allows the shoreland wetlands to be mapped accurately, and will allow future evaluations to
determine if the amount of emergent vegetation changes significantly in the lakes. Areas of
floating leaved or submerged vegetation were not included in the wetland inventory. The lakes
section of the Surface Water Management Plan identifies additional information on the lakes and
describes management opportunities and an implementation plan.
c.Linear Waterways
In addition to the rich abundance of wetlands, Chanhassen has several significant waterways. As
part of the wetland inventory, all linear waterways were also mapped to complete the
comprehensive overview of the city’s aquatic resources. Linear waterways include the major
streams and creeks, but also include some of the ditches, grassed swales, and other areas
designated for conveyance of surface waters. Many waterways flow through wetland areas. In
these portions, the channel has not been mapped, but is contained within the wetland boundary.
The channels have been mapped for those portions not located within a wetland, i.e. those areas
that flow through an upland area. Mapping was done with both GPS and through aerial
photography interpretation. A summary description of the following waterways within the City is
provided in Section IV of this Plan:
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Assumption Creek
Bluff Creek
Lake Minnewashta Outlet
Purgatory Creek
Riley Creek
Unnamed Creek – Southeast Bluff Area.
4.Limitations on Inventory
While every effort was made to identify every wetland within the city, there are undoubtedly
instances where wetlands may have been missed or have boundaries that are not as accurate as
possible. The following are some of the limitations of the inventory.
Access to Private Property: Several areas of the city are privately owned and access
could not be obtained. In these areas, the wetlands were viewed from public vantage
points or interpreted from aerial photographs. This decreases accuracy, but future access
may be able to provide better boundaries and results. If any of these areas are proposed
for development, a wetland delineation and functions and values assessment would be
required.
Farmed wetlands: Because of the high levels of disturbance, farmed wetlands can be
difficult to identify. Review of the annual crop slides available at the USDA Service
Center may identify additional farmed wetlands not apparent in a routine ground survey.
Dating of Aerial Photographs: During the inventory process, aerial photographs from
2000, 2002, and 2003 were used. Recent changes are not visible on these, and the
resolution of the most current photographs isn’t fine enough to make interpretations on
small or wooded basins.
Amount of Recent Construction: In areas of current development, there is so much
change that both the aerial photographs and the previous inventory are significantly
different than what exists today. In these areas, ongoing construction and wetland
impacts instantly date the inventory. Follow-up survey following construction or review
of as-builts may adjust the boundaries or increase the number of storm water ponds and
mitigation areas.
Wetland in Right-of-Way: Many of the major roads and highways have built in drainage
systems composed of ditches within the right of way. These wetlands were not included
in the wetland inventory unless they were also included in the 1992 inventory. Under
current regulatory guidelines, these ditches are usually considered to be jurisdictional
wetland and are regulated under the Wetland Conservation Act. These ditches are
typically encountered with transportation projects, but should be relatively unaffected by
residential development.
Wetlands along Railroad: Crossing the city along a roughly east-west corridor is a single-
track railroad line. Most of the railroad has Type 3 cattail ditches along both sides of it.
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These wetlands are all located on railroad property, and were not included in the wetland
inventory. Many of these wetlands may be incidental under the WCA.
5.Comparison to the 1992 Inventory
In 1992 a wetland inventory was completed for the City as part of the 1994 Surface Water
Management Plan. The 1992 inventory identified a total of 406 basins. These basins were
classified as Pristine, Natural, Ag/Urban, or Utilized depending on quality and setting. Table 41
summarizes the results of the 1992 inventory.
Table 41. Results of 1992 Wetland Inventory
Number
Classification
of Basins
Pristine 3
Natural 106
Ag/Urban 242
Utilized 55
Total 406
Of this total of 406 wetlands, 55 were classified as Utilized, which is the equivalent of being a
storm water pond in the current inventory. Removal of these basins from the inventory leaves a
total of 351 basins, which is slightly less than the 356 wetlands mapped in the current inventory.
This suggests that there has been no net loss of wetlands in the city, but it is not accurate enough
to identify a trend based solely on the number of basins. Twenty two of the wetlands in the 1992
inventory are not part of the current inventory. These basins are not included because they are
no longer wetland (either filled or no longer meet criteria); were mapped as wetland on the 1992
inventory but weren’t wetland then either (the 1992 inventory has several mapped basins that
have field notes indicating “not wetland”); or changed designation, such as Riley Creek as it
flows south from Lake Ann, which was on the 1992 inventory, but is now mapped as a linear
feature and not a wetland.
The current wetland inventory includes 58 wetlands that had previously not been inventoried.
Additionally, the 1992 inventory had 15 basins that were identified as separate basins that have
been merged into single basins in the current inventory. There are also 10 basins that were single
basins that have been split into two basins, and two basins that were one and are now three
individual basins.
Although it is debatable if the number of basins has really changed, the truly significant measure
is just how much wetland is present, and if there has been a loss or gain of wetlands by area, not
number of basins. The 1992 inventory did not calculate the wetland areas, so there is no acreage
available for comparison. Comparing the two inventories using a light table indicates that, at
least for the larger basins, very little has changed. The basins in the 1992 inventory that are no
longer present are all small basins, as are the wetlands that have been added and were not
previously inventoried. Cumulatively, these basins make up only a few percent of the wetlands,
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and do not add or take away significant wetland areas. When the new wetland areas created for
wetland mitigation are considered, it appears that there has been a slight increase in the amount
of wetland in the city, although that cannot be quantified at this time.
The 1992 wetland inventory classified wetlands using the Cowardin and Circular 39 systems, but
they are also not quantified. Comparison of the current inventory to the 1992 inventory,
however, matches wetland types in more than 90% of the wetlands compared. This suggests that
there has also been little change in wetland types between the two inventories. One of the things
that was observed, however, is the increased prevalence of cattails and reed canary grass within
the basins. In the 1992 inventory, cattails (Typha latifolia and T. angustifolia) and reed canary
grass (Phalaris arundinacea) were common, and were often dominant in the more disturbed
basins. Sedges seemed to be more prevalent in 1992 than they are now, which is reflective of the
increased reed canary grass. Many basins that are currently reed canary grass monotypes had
several additional species present in 1992. This trend is unfortunate, but is occurring just about
everywhere and is not a problem unique to Chanhassen. One other important observation
concerning invasive and exotic species is purple loosestrife. Purple loosestrife was observed in
1992 and continues to be in the city. Wetlands that had purple loosestrife in 1992 continue to
have it, but there are very few basins that have it now that did not have it previously. Those
wetlands that have purple loosestrife tend to be impacted by storm water or have a history of
disturbance. This suggests that purple loosestrife is relatively contained and is not posing a
significant problem.
Summary of observations from 1992 to 2005:
In general, there seems to be about the same amount of wetland now as there was in
1992. Inclusion of mitigation areas probably increases the amount of wetland slightly.
Reed canary grass and cattails have increased significantly, at the expense of sedge
meadows and diverse marsh and emergent vegetation assemblages.
Purple loosestrife does not seem to have increased significantly.
There are fewer wetlands in agricultural areas, and many more surrounded by residential
development.
The number of storm water treatment ponds has tripled, although much of that is due to
development. However, several wetlands have been retrofitted with treatment cells to
improve water quality.
A total of 58 wetlands were added that had not previously been inventoried. These
additional basins are mostly small wetlands that may have been missed, but also include
wetland mitigation areas.
22 basins that were identified in the 1992 Inventory were no longer present. These basins
are not part of the 2005 inventory update as they are
No longer present,
o
Are undergoing current modification related to current development,
o
Were mapped but failed to meet wetland criteria currently and based on the field
o
notes from 1992.
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Have changed type to be mapped as other features (for example, some of the
o
streams were mapped as wetlands, but are better mapped as linear waterways).
A total of 15 basins that were mapped as separate basins in the 1992 Inventory have been
merged into single basins in the 2005 Update.
A total of 10 basins that had been mapped as one wetland in 1992 were divided into 2
separate basins in 2005. Two basins that had been mapped as one were divided into three
new basins (six total) in 2005.
6.Comparison to MCWD Inventory
In 2002, the Minnehaha Creek Watershed District completed a functional assessment of all the
wetlands in their watershed. This assessment was called the Minnehaha Creek Routine
Assessment Method (McRAM), and was a pilot project that eventually evolved into the current
MnRAM program. A portion of the Minnehaha Creek watershed is present in the north and
northwest portions of the City of Chanhassen, including the Lake Minnewashta and Christmas
Lake watersheds. The MCWD inventory identified 159 basins within the city of Chanhassen,
most of which were Type 2 and Type 3. In this same area, the current city inventory identified
122 Wetlands, seven of which were not in the MCWD inventory. Most of the basins identified
by the MCWD inventory and not in the city inventory are small basins, but upon investigation
did not appear to be wetland currently. Additionally, the MCWD inventory has several basins
identified as storm water ponds, ditches along the roadways, or areas of potential wetland
restoration, which have not been counted in the city wetland inventory.
In terms of wetland area the two surveys are similar, but the MCWD inventory identifies several
basins as being considerably larger or merges several basins into larger wetland complex.
Overall, there is approximately a 90% agreement in the wetlands. As the two inventories were
both field assessed and had similar protocols, there is no easy explanation for the differences.
Wetland types generally match, as do functions and values assessments. As any projects done in
these areas will require a wetland delineation and review, these differences are likely only
academic and should not have an influence of the validity of the current inventory. Results of the
2002 Minnehaha Creek McRAM results compared to the current inventory are provided
graphically in Figure 11.
The City will have two sets of wetland inventories for the area of the City that is within the
MCWD. The City will adopt the McRAM data that the MCWD completed in 2002, along with
the City’s MnRAM data that was completed in 2005. Both data sets will be used for wetland
assessments in this area of the City.
D.Functions and Values Assessment
Of the 356 wetlands, 515 were assessed using the Minnesota Routine Assessment Method
Version 3.0 (MnRAM). MnRAM 3.0 was developed using the concept of ideal theoretical, pre-
European settlement wetland conditions as the baseline. This application will rank each wetland
for several functional criteria and determine quantitatively whether this function is low, medium,
high, or exceptional for each basin. The MnRAM values will be used to determine the
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classification of a basin, and as a result the appropriate management required to preserve or
manage the basin.
The functional criteria that are evaluated in the MnRAM are:
Maintenance of Characteristic Vegetative Diversity/Integrity
Maintenance of Hydrologic Regime
Flood/Stormwater Attenuation
Downstream Water Quality
Maintenance of Wetland Water Quality
Shoreline Protection
Maintenance of Characteristic Wildlife Habitat Structure
Maintenance of Characteristic Fish Habitat
Maintenance of Characteristic Amphibian Habitat
Aesthetics/Recreation/Education/Cultural
Commercial Uses
Ground Water Interaction
Additional Evaluation Information
Restoration Potential
Sensitivity to Storm Water & Urban Development
Additional Storm Water Treatment Needs
1.Methods
The wetland inventory was completed by visiting each of the wetlands as part of the wetland
inventory. At each wetland the dominant vegetation, wetland types, and a sketch were made in a
dedicated field notebook. A digital photograph was also taken. The data colleted was either
entered directly into the MnRAM database using a laptop computer, or was filled out on field
data sheets and later transcribed into the database. The database is completed using additional
information from the inventory, including wetland area, proximity to other wetlands, surrounding
landuse, soil survey information, and ownership.
One of the first measures of a wetland is the identification of the basin as a critical resource.
Wetlands in the assessment area are evaluated for designation as critical resources based on
several features defined by Minnesota Statutes. These critical wetland resources should be
classified into the Preserve management class due to their special functions. Criteria for
designating wetlands as critical resources are as follows:
Outstanding Resource Value Waters (Minn. Rules 7050.0180)
Designated Scientific and Natural Areas (Minn. Rules 86A.05)
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Wetlands with known occurrences of Threatened or Endangered Species (Minn. Stat.
84.0895)
State Wildlife Management Areas (Minn. Stat. 86A.05, subpart 8)
State Aquatic Management Areas (Minn. Stat. 86A.05, subpart 14)
Wellhead Protection Areas (Minn. Stat. 103I.101, MN Rules Chapter 4720)
Sensitive Ground Water Areas (MN Rules 8420.0548, Subp. 6)
Designated trout streams or trout lakes (MN Rules 6264.0050)
Calcareous fens (MN Rules 8420.1010 through 8420.1060)
High priority areas for wetland preservation, enhancement, restoration and establishment
(MN Rules 8420.0350, subpart 2)
Designated Historic or Archaeological Sites
State or federal designated wild and scenic rivers (MN Rule Chapter 7050)
Mn Pollution Control Agency “special waters search” mapping utility
The City of Chanhassen has wetlands that meet these criteria including the large wetlands along
the Minnesota River, which are part of the Raguet Wildlife Management Area and the Minnesota
Valley Wildlife Refuge; Seminary Fen, which is a calcareous fen; and Assumption Creek, which
is a trout stream. The City also has an abundance of high quality habitats that are known to
contain threatened and endangered species. These areas are not restricted to wetlands, although
the wetlands would be the prime emphasis for protection under this plan.
Calcareous fens are defined in MN Rules 8420.1020 as peat-accumulating wetlands dominated
by distinct groundwater inflows having specific chemical characteristics. The water is
characterized as circumneutral to alkaline, with high concentrations of calcium and low
dissolved oxygen content. The chemistry provides an environment for specific and often rare
hydrophytic plants. Minnesota Rules 8420.1010-1070 sets out minimum standards and criteria
for the identification, protection, and management of calcareous fens as authorized by Minnesota
Statutes, section 103G.223. The MnDNR is charged with identifying and maintaining a list of
calcareous fens in the state and maintains a database of them. Calcareous fens are also listed in
the Classifications for Waters in Major Surface Water Drainage Basins. Finally, the rules for
Nondegradation of Outstanding Resource Value Waters also lists identified calcareous fens in
the state.
State wildlife management areas are established to protect those lands and waters which have a
high potential for wildlife production and to develop and manage these lands and waters for the
production of wildlife, for public hunting, fishing, and trapping, and for other compatible
outdoor recreational uses. State wildlife management areas satisfy the following criteria:
Includes appropriate wildlife lands and habitat, including but not limited to marsh or
wetlands and the margins thereof, ponds, lakes, stream bottomlands, and uplands, which
permit the propagation and management of a substantial population of the desired
wildlife species; and
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Includes an area large enough to ensure adequate wildlife management and regulation of
the permitted recreational uses.
Designated trout streams and lakes in the state of Minnesota are inhabited by trout other than
lake trout. Fishing and other restrictions have been placed on these waterbodies to protect and
foster the propagation of trout. Wetlands associated with these lakes are an integral part of the
whole ecosystem that functions to maintain the characteristics necessary to support the cold-
water fishery.
Endangered and threatened plant and animal species are protected under Minnesota Statute
84.0895 and are designated as one of three categories:
Endangered, if the species is threatened with extinction throughout all or a significant
portion of its range.
Threatened, if the species is likely to become endangered within the foreseeable future
throughout all or a significant portion of its range.
Species of Special Concern, if although the species is not endangered or threatened it is
extremely uncommon in this state, or has unique or highly specific habitat requirements
and deserves careful monitoring of its status.
In 1987 the state began a systematic survey of rare biological features through the Minnesota
County Biological Survey. The goal of this survey was to identify significant natural areas and
to collect and interpret data on the distribution and ecology of rare plants and animals. The data
collected by the county biological survey is available through published maps of each county.
The data available for Chanhassen is through the Natural Communities and Rare Species of
Carver, Hennepin, and Scott Counties, Minnesota. This resources identifies the corridor of Bluff
Creek from south of CSAH 14 (Pioneer Trail) to the intersection of TH 101 and 212 as an area of
maple basswood forest, lowland hardwood forest, oak forest, oak woodland, and dry prairie. The
bluff area in the southeast portion of the City is also identified as having critical maple basswood
habitat. These are all upland types, but are centered along Bluff Creek, and the unnamed creek in
the southeast portion of the city. The area of Seminary Fen and Raquet Wildlife Management
Area (WMA) are also identified on the survey for having outstanding wet meadow, mixed
emergent marsh, oak woodland, seepage shrub swamp, and maple basswood habitats. These are
primarily wetland habitats, and therefore would be of greater concern for the SWMP.
All of these areas identified as having critical habitats are also identified for numerous state or
federally listed plant species. The greatest concentration is in and around Seminary Fen, but
listed species have been identified along Bluff Creek and within the Raquet WMA. Lake
Minnewashta has also been identified as having a listed animal species (Least darter, Etheostoma
microperca), and is the only area in the city outside of the bluff, fen, and river bottom habitats
that has a habitat or species identified on the county biological survey. The MNDNR Natural
Heritage and Nongame Research Program collects, manages, and interprets information on
nongame species and is the primary contact for more recent information on what species and
habitats are present. It is strongly recommended that the Natural Heritage program is contacted
prior to development to obtain the most current information and to identify mitigation measures
that may reduce or eliminate impacts to listed species.
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Once this initial step of identifying critical resources is completed, the data is filled in to address
the remaining functional categories. Each wetland function is rated with a numeric index
according to the formulas embedded in the MnRAM programming. The scoring system is from
0.1 to 1.0 signifying low to high, respectively; in the instances where an exceptional rating
applies, a score of 2 accentuates the rarity. For ‘yes-no’ questions, ‘yes’ will receive a score of 1
and ‘no’ will receive a score of 0.1. Each wetland function then receives an index score with
ratings as follows:
Functional Ratings Question Score Functional Index Score
Exceptional: 2.0 1.01 - 2.00
High: 1.0 0.66 - 1.00
Medium: 0.5 0.33 - 0.65
Low: 0.1 0.10 - 0.32
The MnRAM database is then programmed to run a summary report that lists the results of the
12 functional criteria for each basin. This information is then used to identify the wetland
classification based on the flow chart in Appendix L. This will allow each basin to be classified
as Preserve, Manage 1, Manage 2, or Manage 3.
E.Classification and Management Standards
1.Description of Standards
The MnRAM functions and values analysis will be used to classify basins for the purposes of
establishing regulatory guidelines. The Board of Water and Soil Resources (BWSR) has
established recommended guidelines for classifying and managing wetlands based on the result
of the MnRAM analysis. The BWSR guidelines provide two classification standards based on
wetland recommendations and in compliance with the WCA, state water quality standards, and
multiple wetland management plans. Suggested classifications are either Basic Protection or
Increased Protection, with the local authority determining which level of protection is most
appropriate. Appendix K contains the flow charts used to determine the levels of protection
under both standards. The City has selected to use the Basic Protection Standard, although the
Increased Protection Standard will remain for reference purposes, and may be used as an
alternative if an additional level of protection is warranted.
The Basic Protection Standard is the minimum recommended to satisfy no net loss goals, protect
critical resources, and allow for use of some wetlands in developing areas. The increased
Protection Standard will include more wetlands in the Preserve category that would otherwise be
considered Manage 1. This has the net effect of protecting more wetlands with higher standards.
A summary of the proposed protection standards is included as Table 42.
Using the system recommended by BWSR, each wetland that has been surveyed will be
classified into one of four categories: Preserve, Manage 1, Manage 2, or Manage 3. The Preserve
category is for exceptional and highest-functioning wetlands, or those sensitive wetlands
receiving conveyed storm water runoff that have yet retained a medium level of vegetative
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diversity/integrity. These wetlands are those that should be preserved in (or improved to) their
most pristine or highest functional capacity with wide, natural buffers, in perpetuity.
In the Manage 1 category are high-quality wetlands that should be protected from development
and other pressures of increased use, including indirect effects. Maintaining natural buffers will
help to retain the significant function these wetlands provide. In the event that impacts to these
wetlands cannot be avoided, replacement ratios for mitigation should exceed the state-required
minimums. Manage 2 wetlands provide medium functional levels and the wetland extent should
be maintained. These wetlands often provide optimal restoration opportunity. Manage 3
wetlands have been substantially disturbed and have the lowest functions and values.
1.Preserve
Wetlands classified as Preserve have at least one of the following characteristics:
Are identified as Critical Resources
Wetlands rated with exceptional vegetative diversity/integrity, which may include
wetlands with natural communities not significantly impacted by invasive species or
other human-induced alterations, wetlands harboring endangered or threatened plant
species, or rare wetland habitats classified as imperiled (S1) or critically imperiled (S2)
by the state rankings.
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Table 42. Recommended Wetland Management Strategies
Management Minimum
1
Class Management Strategy Stormwater Treatment Buffer Mitigation Standard Hydrologic Guidelines
Preserve Maintain wetland and existing Avoid conveyed flows 50 feet WCA minimum or greater replacement Bounce (10 yr): Existing
functions, values and wildlife where prudent and feasible. ratio with documented replacement of Inundation (1 & 2 yr): Existing
habitat. Possible need for active Upstream sediment and Require functions/values. Consider requiring (10 yr): Existing
3
management of wetland to protect nutrient pretreatment monuments buffer replacement. Runout Control: No Change
unique features. Apply strict required to maintain to mark
avoidance standards. May be background loading rates. buffer edge. Maintain existing hydrology.
appropriate to develop a Maintain existing Encourage infiltration and reduced
conservation easement. hydrology—divert increased impervious BMPs.
flows. Avoid concentrating Conduct water budget analysis.
flows.
Manage 1 Maintain wetland without Pretreat conveyed flows to 35 feet WCA minimum or greater replacement Bounce (10 yr): Existing + 0.5 ft
degrading existing functions, maintain background ratio. Emphasis on replacement of Inundation (1 & 2 yr): Existing
values and wildlife habitat. Apply loading rates. Require functions and values on site plus 1 day
WCA sequencing process. monuments (10 yr): Existing + 7 days
2
to mark In compliance with Ch. 7050 the entire Runout Control: No Change
buffer edge. area affected by storm water or other Maintain existing hydrology.
wastewater flows must be avoided, Encourage infiltration and reduced
minimized and replaced at a impervious BMPs.
replacement ratio of 1:1 for all changes
in wetland type.
Manage 2 Maintain wetland footprint. Pretreat all conveyed 25 feet WCA minimum or greater replacement Bounce (10 yr): Existing + 1.0 ft
Improve wetland biological and discharges to remove all ratio. Emphasis on replacement of Inundation (1& 2 yr): Existing
plant community diversity/integrity heavy particles and Require functions and values on site plus 2 days
or enhance other functions if maximize removal of fine monuments (10 yr): Existing + 14 days
2
possible. Apply WCA sequencing grained sediment prior to to mark Runout Control: 0 to 1.0 ft above
process. Consider for restoration. discharging to the wetland buffer edge. existing runout
Manage 3 Allow for sequencing and Pretreat all conveyed flows 16 feet WCA minimum replacement, although Bounce (10 yr):
replacement plan flexibility. to remove all medium sequencing flexibility may be used No Limit
Consider for grained and larger (M.R. 8420.0650). Inundation (1 & 2 yr): Existing
restoration/enhancement. sediments. plus 7 days
(10 yr): Existing + 21 days
2
Runout Control: 0 to 4.0 ft
above existing runout
1. Buffers are unmowed, naturalized strips of vegetation around the wetland perimeter. Buffers would be provided during development or redevelopment
2. If currently landlocked, new outlet should be above delineated wetland elevation.
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Wetlands rated as exceptional for wildlife habitat. These include wetlands known to
harbor endangered or threatened animal species, rare communities, or wildlife refuges
and fish and wildlife management areas whose purpose is maintaining suitable habitats
for wildlife.
Wetlands rated as high for amphibian habitat.
Wetlands rated as exceptional for fish habitat. These wetlands include those specifically
managed for fish management; designated trout streams, lakes or adjacent wetlands; and
known spawning habitat for game fish.
Wetlands rated high for shoreline protection. Wide wetlands bordering lakes and feeder
streams that have persistent, emergent, submergent, or floating-leaved vegetation are
critical to protecting the water quality of the lakes from bank erosion and sedimentation
from upstream.
Wetlands rated exceptional for aesthetics/education/recreation/cultural and rated high for
wildlife habitat, include those located on public lands that provide a unique or rare
recreational, educational, or cultural opportunity, and have high functional level for
wildlife since that is typically a primary focus for users.
Wetlands that are exceptionally sensitive to storm water impacts and have a vegetative
diversity/integrity rating of medium or higher were also placed in this category. These
wetlands may have suffered some degradation from human influences due to their
heightened sensitivity. The vegetative quality of the wetland is such that improved
management may allow for restoration of the community.
Wetlands with a high vegetative diversity/integrity rating and a high rating for wetland
water quality. The vegetative community in these wetlands typically has been only
slightly affected by humans and still maintains high functioning to maintain water
quality, which is critical to wetland sustainability.
Wetlands with a high vegetative diversity/integrity rating and a high rating for hydrologic
regime. The vegetative community in these wetlands typically has been only slightly
affected by humans and still maintains high functioning levels for hydrologic regime,
which is critical to wetland sustainability.
2.Manage – 1
Wetlands classified as Manage 1 have at least one of the following characteristics:
Wetlands rated with high vegetative diversity/integrity, which typically include diverse
wetland plant communities with less than 20 percent cover of non-native or invasive
species.
Wetlands rated as high for wildlife habitat. These generally include wetlands located
within large tracts of undeveloped land or in parks, which allow for wide high quality
upland buffers. In addition, this includes seasonal wetlands that are well buffered.
Wetlands rated as medium for amphibian habitat. This includes seasonal wetlands that
are well buffered.
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Wetlands rated as high for fish habitat. These wetlands are lacustrine/riverine or are
contiguous with a permanent waterbody or watercourse and provide spawning/nursery
habitat, or refuge for native fish species in adjacent lakes, rivers or streams.
Wetlands rated medium for shoreline protection. These wetlands include those that are
moderately wide and support persistent emergent, submergent, or floating-leaved
vegetative cover bordering lakes and feeder streams.
Wetlands rated high for aesthetics/education/recreation/cultural and medium for wildlife
habitat, include those that provide a number of benefits that may include: spatial
buffering, accessibility, public ownership, multiple recreational opportunities, and
medium-quality wildlife habitat.
Wetlands that are highly sensitive to storm water impacts and have a vegetative
diversity/integrity rating of medium or high. The vegetative quality of the wetland is
such that improved management may allow for restoration of the community.
Wetlands with a medium vegetative diversity/integrity rating and a high rating for
wetland water quality. The vegetative community in these wetlands has only been
moderately affected by humans and still maintains high functioning levels for water
quality, which is critical to wetland sustainability. These wetlands would likely benefit
from active management.
Wetlands with a medium vegetative diversity/integrity rating and a high rating for
hydrologic regime were placed in the Manage 1 category. The vegetative community in
these wetlands has only been moderately affected by humans and still maintains high
functioning levels for hydrologic regime, which is critical to wetland sustainability.
These wetlands would likely benefit from active management.
Wetlands rated high for commercial use. These wetlands provide important social value
without having an altered hydrology.
3.Manage – 2
Wetlands classified as Manage 2 have at least one of the following characteristics:
Wetlands rated with medium vegetative diversity/integrity, which typically include
wetlands with less diversity and up to 50 percent cover of non-native or invasive species.
Wetlands rated as medium for wildlife habitat. These often include wetlands that are
increasingly separated from natural communities and wildlife corridors; they often lack
significant upland buffers and are increasingly altered.
Wetlands rated as low for amphibian habitat. These wetlands are increasingly altered,
but they still have some opportunity to provide either breeding, over wintering, or resting
habitat for amphibians.
Wetlands rated as medium for fish habitat. These wetlands include those which are
intermittently connected to waterbodies supporting native fish populations
Wetlands rated low for shoreline protection. While these wetlands are not providing the
highest level of protection to the lake or river systems, their mere presence provides some
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level of protection that should not be dismissed. These wetlands are typically narrow,
with little emergent, submergent, or floating-leaved vegetation.
Wetlands rated Medium for aesthetics/education/recreation/cultural and Low for wildlife
habitat.
4.Manage – 3
Wetlands classified as Manage 3 include all of the remaining wetlands that did not fit into any of
the above-described conditions. All of these wetlands would rate low for vegetative
diversity/integrity. Many of these wetlands rate medium or high for downstream water quality
protection and for flood storage/attenuation. This correlation is expected since wetlands that
provide higher levels of water quality treatment and runoff/rate control often suffer from
ecological degradation.
2.Results
The wetlands that were included within the updated wetland inventory were subjected to the
Basic Protection Standard to determine the appropriate wetland classification. The results of this
classification are shown below in Table 43, and graphically on Figure 12.
Table 43. Results of 2002 McRAM and 2005 Chanhassen Wetland Inventories
Number
Classification
of Basins
Preserve 29
Manage 1 67
Manage 2 196
Manage 3 17
Unclassified 47
Total 356
The majority of the wetlands have been classified as Manage 2, with the second most common
classification being Manage 1. This distribution seems to accurately reflect the status of the
wetland, as the vast majority of the basins are composed of cattail marshes and reed canary
grass-dominated wet meadows. These habitats are generally lower in quality than more diverse
basins would be. Preserve basins are the highest quality, and include many of the hardwood
swamps, fens, mitigation sites, and extensive floodplain areas along the Minnesota River.
Manage 1 basins include many of the basins located within the Arboretum and around the lakes,
and tend to be located in the more northern portions of the city. Manage 3 wetlands are severely
degraded, and include excavated wetlands on the golf courses and the farmed wetlands. Many of
the Manage 3 basins are suitable candidates for potential wetland restoration if land-use practices
can be modified to accommodate it.
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The unclassified basins are wetlands that were identified from aerial photograph review
following the termination of the MnRAM field work. Some of these basins are located on
private property and were not accessible during the review. Many of these unclassified basins
were not included in the previous inventory, and therefore were not specifically sought out
during the update. It is assumed that these unclassified basins would have a similar distribution
as those that were evaluated. The wetland inventory can be adjusted to accommodate these
unclassified basins, should they need to be classified in the future.
F.Wetland Buffer Standards
Wetland buffers are used to reduce runoff of sediment and nutrients into wetlands. Buffers can
also provide wildlife habitat, if they are of sufficient size. The effectiveness of buffers varies
depending on slope, density of vegetation, type of vegetation, and width. While the literature is
quite variable, the one certainty is that the bigger the better. For this reason, the recommended
minimum buffer width is greater for Preserve classifications, and decreases as wetland quality
decreases. The standards recommended are minimum standards, and are intended to provide a
reasonable level of protection for the quality of the wetland being protected.
G.Storm Water Susceptibility
Storm water runoff contains more than just water. Nutrients, soil particles, and other
contaminants are also included in runoff, and levels can be very high depending on the types of
soils and land use in the areas surrounding a wetland. These other components can be
detrimental to a receiving body, and can upset the ecological balance. Changes in the volume,
rate, frequency, or duration of storm water entering a basin can also alter the ecological integrity.
Alterations associated with storm water can lead to changes in the function of wetlands, and can
lead to loss of fish and wildlife habitat, replacement of native species with invasive or nonnative
species, and loss of other wetland functions. Wetland sensitivity varies by wetland type.
Table 44 identifies wetland types and their sensitivity to storm water. Pristine wetlands, bogs,
and fens are highly susceptible to hydrologic alteration. Floodplain forests are moderately
susceptible, as storm water discharge can mimic some of the natural conditions of that habitat
type. Shallow marshes and wet meadows are the most tolerant, particularly those that are
already degraded or composed on non-native species.
Table 44. Susceptibility of Wetlands to Degradation by Stormwater Impacts
Exceptionally Moderately
Susceptible Highly Susceptible Susceptible Wetland Least Susceptible
1234
Wetland Types: Wetland Types: Types: Wetland Types:
Sedge Meadows Shrub-carrs a Floodplain Forests a Gravel Pits
Open Bogs Alder Thickets b Fresh (Wet) Meadows b Cultivated Hydric Soils
Coniferous Bogs Fresh (Wet) Meadows c, e Shallow Marshes c Dredged Material/Fill
Material Disposal Sites
Calcareous Fens Shallow Marshes d, c Deep Marshes c
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Low Prairies Deep Marshes d, c
Source: Storm -Water and Wetlands: Planning and Evaluation Guidelines for Addressing Potential Impacts of
Urban Storm-Water and Snow-Melt Runoff on Wetlands, St. of Mn. Storm-Water Advisory Group, June, 1997
Notes: There will always be exceptions to the general categories listed above
1. Special consideration must be given to avoid altering these wetland types. Inundation must be avoided.
Water chemistry changes due to alterations by storm water impacts can also cause adverse impacts. All
Critical Resources are considered exceptionally susceptible regardless of wetland type
2. a, b, c can tolerate inundation from 6 to 12 inches for a short period of time. May be completely dry in
drought or late summer conditions. d can tolerate more than 12 inches inundation, but adversely impacted
by sediment and nutrient loading and prolonged water levels. e, some exceptions
3. a, can tolerate annual inundation of 1 to 6 feet or more, possibly more than once per year. b, fresh meadow
dominated by reed canary grass, cattail, giant reed, or purple loosestrife
4. These wetlands are usually so degraded that input of urban storm water may not have adverse impacts
Wetland management for storm water inputs are proposed to maintain tolerable hydrologic and
water quality changes based on the goals of the management classification. The standards
represent what is recommended for tolerable bounce, inundation period, and inlet and outlet
controls.
H.Potential Wetland Mitigation and Restoration Sites
One of the components of the wetland inventory was to identify potential areas on city-owned
property that would be suitable for the creation of wetland mitigation areas or for developing a
wetland bank. One of the questions (number 56) on the MnRAM specifically asks for an
evaluation of the restoration potential of a basin. This is a somewhat difficult question as it is
specific to restoration of wetland hydrology, and it is rare that you would know of subsurface
drainage or hydrologic alterations from a single field visit. Guidance suggests that the question
isn’t applicable to basins that are not drained or ditched or agricultural purposes. Only 11 basins
were identified as farmed wetlands, and none of them had any indication of subsurface drainages
or ditches. None of them were on city–owned property either.
The McRAM evaluation identified 45 basins within the city that are restorable, but this
evaluation is limited to the Lake Minnewashta and Christmas Lake basins, which are not areas of
intensive agriculture. Certainly many basins would be candidates for vegetation restoration. The
widespread occurrences of reed canary grass, hybrid cattails, giant reed grass, and purple
loosestrife would make many basins candidates for vegetation restoration. The biggest drawback
to this, however, is that it is very difficult to get wetland credits, and a good restoration project is
very costly. The cost benefit of vegetation restoration is currently so low that it is practically
unfeasible.
There are a few areas that creation of new wetlands may be feasible on city-owned property.
Many of these sites would be extensions of existing basins, and careful hydrologic analysis
would be required to determine how feasible this may be. Careful consideration must also be
given concerning the species of plants present in the existing and proposed basins. Many
extensions of low quality basins are performed, but few are as successful as proposed due to the
problems of fighting invasive and exotic species. This list of suggested opportunities does not
include areas that are currently wooded, as the ecological value of many of the woodlands may
exceed the value of the additional wetland created. Mitigation opportunities on private properties
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are also not discussed. There are many opportunities for wetland restoration and/or creation in
many of the agricultural areas. Much of the property owned by the University of Minnesota and
Carver County also have areas suitable for wetland creation. In both these instances, however,
the properties are not readily available for city use, and therefore it is not feasible to suggest
properties that cannot be used.
The following properties are suggested for further investigation into the potential to create
wetlands, and/or create a wetland bank. These sites have been selected based on the potential
area that could be used to create new wetland areas and potentially restore adjacent wetlands as
well. Many other opportunities to create small wetland areas are also present, but are not
included as it is typically not cost-effective to create or restore small areas. The following eight
properties have been identified as the best potential areas for creating new wetland. These
parcels are identified on Figure 13
Parcel ID 3641
- This property is within a city park adjacent to Carver County property. There
are two wetlands in the park, plus some recreational amenities. The existing wetlands are low
quality, but there is some room for expansion and potential restoration. The McRAM identifies
this area as potential wetland restoration as well.
Parcel ID 6114
– This property is also a park with a small trail system. A small storm water
treatment pond is located on the west end, and could be used as the first cell of a larger wetland
complex. Space is somewhat limited, and there is a concern that sufficient hydrology could be
obtained.
Parcel ID 4177
– This property is also a small city park, and already has degraded Type 2
wetland on it. There is room for expansion of this basin and restoration of hydrology and
vegetation. This basin has also been identified as a potential restoration site by the McRAM.
Parcel ID 4285
– This parcel is also located in a city park and currently has a grassed swale
running through it. It may be possible to intercept the drainage from the swale and support a
mitigation area in the park. This could be designed to incorporate the existing trail system and
have less loss of green space than would occur in other parks. This is one of the better sites
reviewed for creating wetland.
Parcel ID 3960
– This is also a park with a small ballfield. A portion of the ballfield is low and
has been included in the wetland inventory. Restoration of this site is possible, but would come
at the cost of losing the ball field. Given the soggy conditions, this may be a good exchange over
the improvements needed to improve the park.
Parcel ID 3695
– This is a small parcel surrounded by residential development. A grassed
swale, flow-through wetland exists in the property. This could be expanded into a larger flow-
through wetland.
Parcel IDs 12823 and 12835
– These two adjacent properties are located on the south side of
Rice Marsh Lake and are undeveloped. The area along the lake is wooded, but there is some
open space on the south side that may be suitable for the creation of wetland.
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VI.IMPLEMENTATION PLAN
A.Overview
The Implementation Plan is the final section of the Plan, and one which is intended to provide
guidance in carrying out the Plan goals and objectives. The implementation section summarizes
capital improvement projects, studies and ongoing maintenance, inspection, monitoring and
other management activities. This Plan is intended to serve the City for at least the next ten years
and possibly out to the year 2030. Procedures for amending the Plan are provided.
Based on the action-implementation plans from each of the seven goals, a process for
accomplishing the goals and policies of this SWMP is established. In order to focus the
implementation efforts towards achieving the stated goals, each of the individual goal sections of
this Plan include an implementation plan summary. A similar summary is provided in Section IV
of this Plan. Table 46 includes the elements of all the individual plan implementation tables and
further includes a planning-level cost estimate for each activity or project. A summary of the
estimated program costs is provided at the end of this section.
While the City has an extensive list of projects to implement and activities to conduct on an
ongoing basis, there are several efforts that are considered the highest priority to complete. Table
45 below lists these priority projects and activities in the order they appear in this Plan, without
assigning a direct priority ranking to each one. Planning level costs and a more detailed
description for each project are provided in Table 46.
Table 45. Implementation Program Priority Projects and Activities
Plan Section
Project Name Description Year
ID
Reference
Evaluate High Water Levels on Review previous efforts and evaluate Table 7 - 5 2007
1
Lotus Lake opportunities to reduce risks.
2 Update Storm Water Ordinance Update to reflect standards in App. D. Table 9 - 7 2006
3 Update Wetland Ordinance Update to reflect Plan recommendations. Table 11 - 3 2007
Identify stream bank protection Identify improvement locations during Table 13 - 3 2006
4
needs at storm outlets NPDES outfall inspections process. -07
Select/create storm system Identify long-term system for record Table 17 - 3 2006
5
inspections/reporting database keeping, planning and reporting. -07
Pond LL-P7.5 (Lotus Lake Proposed pond installation in current Table 25, 2007
6
watershed) lake association property. Appendix I
7 Pond LL-P10.17 (Lotus Lake Add treatment adjacent to channel / Table 25, 2008
watershed) wetland in backyards. Appendix I
8 Pond LL-P2.2 (Lotus Lake Add treatment area adjacent to wetland Table 25, 2008
watershed) on lake association property. Appendix I
9 Pond LM-P8.8 (Minnewashta Add pond in Fir Tree street recon project Table 27, TBD
watershed) area. MCWD P-reduction project. Appendix G, I
10 Pond LM-P1.5 (Minnewashta Pond in City park, Orchard Lane street Table 27, TBD
watershed) recon area. MCWD P-reduction project. Appendix G, I
11 Pond LR-P2.3 (Lake Riley Potential pond in Bandimere Park Table 29, TBD
watershed) Appendix I
12 Proposed pond installation in current Table 29, TBD
Pond LR-P2.6 (Lake Riley)
lake association property. Appendix I
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Table 46. Implementation Plan Summary/Overview
Completed
Plan Section ID Estimated (Y/N)
(Table No.) Activity / Project Resources Measurement Schedule Cost Notes
Review of proposed development projects BMPs installed for additional detention
Explore opportunities for discharge rate Ongoing $10,000
1
reductions or hydrograph modifications in the
Hydrologic / hydraulic models Reduction in peak/duration of erosive flows
Water
(annual cost)
Bluff Creek System.
Quantity
Analysis of downstream impacts Reduction in bank erosion
Goals
City-wide model Improved system model
Refine City-wide hydrologic model as Ongoing Staff
2
proposed projects are completed (each project) Time
Engineering Dept. staff
(Table 7)
Developer’s plans and modeling submittals
Property records GIS analysis of parcel data
Review easement coverage on City owned and 2008 $20,000
3
maintained storm systems relative to the 100-
Dedicated easements over ponds to the 100-year
City pond GIS data and parcel coverages
year HWL
high water level - annually
(Ongoing/annual)
Property owners
$15,000
Example agreement in Appendix of this plan Reduction of localized flooding
Initiate Private System Maintenance Program 2007 $10,000
4
“www” access to O&M requirements Improved water quality treatment efficiency
$50,000
(Ongoing/annual)
City inspection and maintenance staff Pond/BMP cleanout
City-wide model Completed Study
Complete Feasibility Study to evaluate 2007 $20,000
5
potential reductions of extended high water
Identified opportunities for volume and water
XP-SWMM if needed
levels on Lotus Lake
quality benefits
Coordinate with watershed district efforts
NPDES SWPPP Education events
Continue Education program as part of the Ongoing $5,000
1
City’s NPDES Permit program SWPPP (annual cost)
Water Resources Coordinator
Water Staff
Quality
Time
Watershed Organizations
Goals
City staff inspectors Measurable goals from NPDES SWPPP
Coordinate BMP maintenance program with Ongoing $10,000
2
NPDES SWPPP and private system
(annual cost)
Maintenance staff BMPs maintained
(Table 9)
maintenance program.
Private maintenance program in Table 7, ID 4. Materials removed
Review of proposed development projects BMPs installed
Explore opportunities for water quality Ongoing $350,000
3
improvement projects. Focus on Riley and
City-wide hydrologic model Improved water clarity trends
(Avg. annual cost
Lotus Lakes to jump start anticipated TMDL
- see App. I of
GIS database of storm systems, ponds, wetlands Increased treatment capacity
results. Identify direct discharges (no treatment
Plan for pond
Street recon projects (see Appendix G)
pond/system) to priority water resources.
summary info.)
Recommended pond data in Appendix I.
MPCA Final Study Recommendations
Participate in TMDL Studies for Riley and Pending MPCA
4
Lotus Lakes Funded
Watershed Organizations
MPCA Citizen Monitoring Annual assessment of data
Continue water quality monitoring programs Annually Staff
5
on City lakes and key resources Time
City staff Management approach adjustments
Lake Management Plans and Studies
Study memorandums in Appendix G. Completed implementation projects
Complete Neighborhood studies and Varies Included
6
in
implement treatment BMPs (annual cost)
Street reconstruction project plans Treatment capacity established
Table 9
See Figure 8
2006 Plan standards in Appendix D Completed ordinance update
7 Update storm water management ordinance 2006-2007 Staff
time
Local watershed standards
Table continued on next page.
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Table 46. Implementation Plan Summary/Overview
(continued)
Completed
Plan Section ID Estimated (Y/N)
(Table No.) Activity / Project Resources Measurement Schedule Cost Notes
2006 Inventory Completion of annual WMP project review
Implement the wetland management program Ongoing Staff time
1
activities
described in Section V of this Plan
Wetland Conservation Act
Wetland
Implemented projects
MnRAM, GIS Database
Goals
New wetland created
Watershed Organizations
Development project reviews
(Table 11)
Development projects Maintained, updated database
Update Wetland Inventory with project data. Ongoing Staff time
2
Digitize created wetlands and modify impact
MnRAM, GIS Database
wetlands per projects.
City staff
2006 Inventory Completed ordinance update
Update wetland management ordinance 2007 $5,000
3
Draft ordinance recommendations - Appendix
K of Plan
Development projects Implemented projects
Continue to implement the erosion and Ongoing
1
sediment control inspection program.
Carver County
Erosion
and
Watershed Organizations
Sediment
Clean Water Hotline
Control
Review of proposed development projects BMPs installed
Explore opportunities for erosion protection Ongoing Staff time
2
Goals
and bank stabilization at key storm system
City-wide hydrologic model Reduction in bank erosion
conveyances and outlets
Analysis of peak rates on downstream impacts Reductions in gullies, washouts
(Table 13)
Implement new technologies for inspection Improved compliance at construction sites
Evaluate the need for improving the efficiency 2006 $5,000
3
tracking
and effectiveness of the inspection program.
Reduced sediment delivered to water bodies
(Ongoing/annual)
Dedicated staff to supplement work of Carver
County staff
Original Utility Study Completed study
Complete an assessment of trunk storm water 2006 Done
1
and utility system fees needed to support the
Implemented changes to assessments and or
City staff
Financing Review after
overall City water resources program.
utility rates
Non-Deg Plan
Goals
NPDES SWPPP requirements
Completion
Water Quality Hotline
(Table 15)
MPCA Programs BMPs installed
Explore opportunities for grant program Ongoing $5,000
2
funding to implement water resource
(annual cost)
Water quality improvement, education and/or
Watershed Organizations
improvement projects
demonstration projects
Metropolitan Council
Table continued on next page.
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Table 46. Implementation Plan Summary/Overview
(continued)
Completed
Plan Section ID Estimated (Y/N)
(Table No.) Activity / Project Resources Measurement Schedule Cost Notes
SWPPP and individual BMPs Annual Report and program assessment
Continue to implement the City’s NPDES Annually June Staff time
1
summary
Permit program SWPPP. 30
Permit activity tracking system
Regulatory
Responsibility (tracking
$3,000
Adjacent MS4s
system annual
Goals
cost)
(Table 17)
Minnehaha Creek Plan Plan updates as needed
Maintain consistency with Watershed Ongoing Staff time
2
Management Organization Plan Goals and
Riley-Purgatory Bluff Creek Plan
Policies
Carver County Plan
Lower Minnesota River Watershed District Plan
Current GIS data for structures Evaluate options
3Establish electronic NPDES inspection and 2006 $10,000
maintenance program tracking and reporting
Recommendations in Appendix J System established and fully functional
2007
system
Annually
Off-the-shelf software or in-house system Ongoing data collection/reporting
SWPPP and individual BMPs Annual Report and program assessment
City Storm Water Program and Annual NPDES Annually Prior $2,000
1
summary
Permit Public Meeting to June 30
Permit activity tracking system
Public hearing held at City Council
Adjacent MS4s
Public
Public Input
Participation
Information
Metro WaterShed Partners Resulting products and/or information
Remain involved in local educational Ongoing Staff time
2
and distributed
campaigns
Counties
Education
Watershed Districts
Goals
Metropolitan Council Annual results in report from Metropolitan
Recruit volunteers to participate in the Citizen Annually Staff time
3
Council
Assisted Monitoring Program (CAMP) for
City staff
(Table 19)
lakes
Metro WaterShed Partners Articles placed in newsletter quarterly
Include water resources articles in Chanhassen Quarterly; Staff time
4
Connection Ongoing
Watershed Districts
City staff
Metro WaterShed Partners Updated information on website regarding
Provide water resources-related information on Ongoing Staff time
5
waterbody water quality, ongoing projects and
the City’s website
City staff
current issues
City staff Regular updates to outgoing messages to
Continue to maintain Clean Water Hotline Ongoing Staff time
6
provide information on current water resources
projects
Table continued on next page.
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Table 46. Implementation Plan Summary/Overview
(continued)
Completed
Plan Section Estimated
(Y/N)
(Table No.) ID Activity / Project Resources Measurement Schedule Cost
Notes
City staff
Monitor and manage Eurasian watermilfoil and Ongoing
Reduction of watermilfoil and curlyleaf pondweed
curlyleaf pondweed
Citizen Monitoring program
Steady to improved water quality trends
Lake
Water quality monitoring events should occur at
Watershed District Staff/Coordination
Ann
least once every five years (phosphorus levels,
Use Attainability Analysis
Lake
especially within the hypolimnion). Secchi disc
Management
sampling monthly every year during the summer
Recommend-
City staff
Continue to follow the 1994 Lake Management Ongoing
Christmas
Steady to improved water quality trends
ations
Plan recommendations
Citizen Monitoring program
Lake
Watershed District Staff/Coordination
(Table 31)
City staff
Control nuisance invasive/exotic species, Eurasian Ongoing
Reduction of nuisance invasive/exotic species
watermilfoil, curlyleaf pondweed, purple loosestrife.
Citizen Monitoring program
Lotus
Curlyleaf pondweed should be monitored and
Watershed District Staff/Coordination
Lake
controls implemented if it becomes dominant.
Technical expert/consultant
Purple loosestrife control should be continued or
initiated using biocontrol agents (beetles)
City staff
Curlyleaf pondweed should be monitored and a 2008 (Plan) $25,000
Reduction of nuisance invasive/exotic species
control/management plan should be developed.
Citizen Monitoring program
Steady to improved water quality trends
Lake
Complete a Lake Management Plan.
Watershed District Staff/Coordination
Ongoing
Lucy
A vegetation management plan should be developed
Technical expert/consultant
separately or as part of an updated Lake Plan.
Use Attainability Analysis
City staff
Monitor adjacent wetlands for phosphorus input. Ongoing
Reduction of nuisance invasive/exotic species
Citizen Monitoring program
Implement nuisance/invasive species control
Steady to improved water quality trends
Lake
(Eurasian watermilfoil and purple loosestrife).
Watershed District Staff/Coordination
Minne-
Curlyleaf pondweed monitoring is recommended.
Technical expert/consultant
washta
City staff
Continued implementation of the 1994 Lake Ongoing
Reduction of nuisance invasive/exotic species
Management Plan.
Citizen Monitoring program
Rice
Steady to improved water quality trends
Development and implementation of a strategy for
Watershed District Staff/Coordination
Marsh
controlling curlyleaf pondweed.
Technical expert/consultant
Lake
Use Attainability Analysis
City staff
Support the implementation of water quality
Steady to improved water quality trends
treatment practices throughout the watershed.
Citizen Monitoring program
Lake Omgoing
Watershed District Staff/Coordination
Riley
Technical expert/consultant
Use Attainability Analysis
City staff
Monitoring and managing nuisance species, including Ongoing
Reduction of nuisance invasive/exotic species
Eurasian watermilfoil and curlyleaf pondweed.
Citizen Monitoring program
Lake
Reduction in rough fish populations
Active control of rough fish. Participate in carp
Watershed District Staff/Coordination
Susan
barrier project with the TH 101 corridor project.
Technical expert/consultant
Use Attainability Analysis
City staff
Evaluate use of in-lake phosphorus treatments. Ongoing
Steady to improved water quality trends
Citizen Monitoring program
Continued monitoring is recommended, especially
Lake
for phosphorus concentrations.
Watershed District Staff/Coordination
St. Joe
Technical expert/consultant
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B.Implementation Priorities and Costs
Paying for water management projects and administrative activities has become more complex in
recent years. In the past, special assessments against benefited properties financed most of the
necessary improvements. However, the financial options have broadened considerably. The
question is, which method(s) best suits the needs of the City. The major categories of funding
sources are: Ad Valorem Taxes; Special Assessments; Storm Water Utility; and Grants as
summarized below.
Ad Valorem Tax. General taxation is the most common revenue source used to finance
government services, including minor maintenance measures for drainage and water
quality facilities. Using property tax has the effect of spreading the cost over the entire
tax base of a community. A special tax district can also be used to raise revenue. The
special tax district is similar to the administrative structure under general taxation except
that all or part of the community may be placed in the tax district. The principle is to
better correlate improvement costs to benefited or contributing properties.
Special Assessments.Municipalities are familiar with the use of special assessments to
finance special services from maintenance to construction of capital improvements. The
assessments are levied against properties benefiting from the special services. The
philosophy of this method is that the benefited properties pay in relation to benefits
received. The benefit is the increase in the market value of the properties.
Trunk Storm Sewer/Development Fees.Fees charged to new development that generates
runoff can be charged to finance infrastructure needed to serve the development. This is a
useful tool in communities that are rapidly developing.
Storm Water Utility. A utility is a service charge or fee based on usage, similar to the fees
charged for sanitary sewer or potable water supply. The fee is typically charged against
improved parcels based on the concept of contributors (or users) pay. The rate structure is
based on the land use type, density, and parcel size to reflect the typical runoff
contributed by a given parcel. In some cases parcels may be eligible for a credit to reduce
their fee.
Grants.State grants are available for surface water management and non-point source
pollution. However, it is generally not a good financial practice to rely on grants for a
service program. This source of revenue is not dependable and requires constant
speculation as to its availability. Grants are useful but should only be used to supplement
a planned local revenue source. Some of the agencies and programs that may have
available grant funds include:
Environmental Protection Agency
o
Watershed Districts and WMOs
o
U. S. Fish and Wildlife Service
o
Minnesota Department of Natural Resources
o
Metropolitan Council
o
Minnesota Pollution Control Agency
o
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The City currently has a storm water utility (Surface Water Management Utility Fee) in place.
The 1994 Surface Water Management Plan recommended the establishment of a trunk fee
system for new development. This funding served to supplement the already-existing surface
water utility fee. The Purpose of each funding approach is described in Table 47.
Table 47. Surface Water Management Fees in Chanhassen
Fee Established Purpose
Funding improvements related to increasing the
Surface Water Connection
1994
capacity of or reconstructing infrastructure to
Charge
accommodate new development.
Surface Water Management 1990 Planning, monitoring, capital expenditures,
Utility Fee personnel, maintenance, equipment.
The surface water connection charge is a one-time charge payable upon subdivision of a
property. The connection charge includes a water quality and a water quantity fee for each net
developable acre. For the purpose of fee calculations, the net developable area generally includes
total site area after subtracting the land that cannot be developed including, but not limited to,
pond or wetland areas, buffer areas and steep slopes.
The surface water management utility fee is a quarterly fee charged to each property within the
City. Single family residential, rural residential, agricultural and undeveloped properties are
charged a fixed quarterly fee. All other land uses are charged based on a base rate multiplied by
the utility factor for the land use multiplied by the acreage of the parcel, exempting public right-
of-way and lakes.
These revenue sources will be continued in order to fund surface water management activities
within Chanhassen. The charges and fees will be reviewed and adjusted annually to ensure
adequate funding for the activities set forth in this plan and those required by law.
In order to establish a baseline estimate of the overall program costs for the next 20 to 30 years
of the Plan, individual activity and project cost estimates were developed. The costs represented
below do not account for the parts of the overall program implementation budget that include
costs such as staff salaries, street sweeping equipment, water quality monitoring equipment or
sampling costs, and sweeping disposal costs. The costs also do not include land acquisition costs
(capital or legal) which may be necessary to implement the pond or water quality treatment
BMPs recommended in the Plan (see Appendix I for recommended pond options).
Table 48 summarizes the estimated implementation costs on an annual basis for the projects and
activities presented in Table 31. These estimated costs will be updated as the Plan proceeds
through the final review and approval process, and are intended here as an order of magnitude
estimate of the funding needed for the projects and activities identified in this Plan.
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Table 48. Implementation Plan Financial Summary
Estimated
Description Annual Costs
Category
(examples)(2006 Dollars)
Planning Costs
Feasibility Study - Lotus Lake
$50,000
High Water Levels
Studies
Ordinance Updates
Review of Easements on
Public Education Efforts
Ponds/BMPs City-wide
Update Storm Water and Wetland
Ordinances
Public Education Materials and
Event Participation
Capital Construction Costs
Sediment Removal from Pond and
$350,000
structural BMPs
Construction of Ponds, Outlet
Structures and/or Structural
Storm Pond and BMP Construction
BMPs
Costs
Pond/BMP Cleanout
Operation and Maintenance
Updates to GIS Databases for
$35,000
easements, pond projects, BMP
Program Management
New Technologies for Tracking
Program Management New
Inspections Coordination with
System and Site Inspections
County Staff
Updates to NPDES Program
Tracking Systems
Estimated Total Annual Cost $435,000
C.Amendments to the Plan
1.Amendments Procedures
The Surface Water Management Plan is intended to extend approximately through the year 2016.
In conjunction with this Plan, the NPDES SWPPP activities will be reviewed and evaluated
annually in a public meeting and the permit program itself will be updated as required by the
MPCA NPDES permit program. For this plan to remain dynamic, an avenue must be available to
implement new information, ideas, methods, standards, management practices, and any other
changes which may affect the intent and/or results of this Plan. Amendment proposals can be
requested at any time by any person or persons either residing or having business within the City.
2.Request for Amendments
Any individual can complete a written request for a Plan amendment and submit the request to
City staff. The request shall outline the specific items or sections of the Plan requested to be
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amended, describe the basis and need for the amendment and explain the desired result of the
amendment towards improving the management of surface water within the City. Following the
initial request, staff may request that additional materials be submitted in order for staff to make
a fully-informed decision on the request.
3.Staff Review
Following a request for Plan amendments, staff will make a decision as to the completeness and
validity of the request. If additional information is needed by staff to determine the validity of
the request, staff will generally respond to the requestor within 30 days of receiving the request.
Following receipt of sufficient information such that validity of the request can be evaluated,
there are three options which are described below:
a)Reject the amendment. Staff will reject the amendment if the request reduces, or has the
potential to reduce, the Plan’s ability to achieve the goals and policies of the Plan, or will
result in the Plan no longer being consistent with one or more of the watershed district’s
plans.
b)Accept the amendment as a minor issue, with minor issues collectively added to the plan
at a later date. These changes will generally be clarifications of plan provisions or to
incorporate new information available after the adoption of the 2006 Plan. Minor changes
will generally be evaluated on the potential of the request to help staff better implement
and achieve the goals and policies the Plan. Minor issues will not result in formal
amendments but will be tracked and incorporated formally into the Plan at the time any
major changes are approved.
c)Accept the amendment as a major issue, with major issues requiring an immediate
amendment. In acting on an amendment request, staff should recommend to the City
council whether or not a public hearing is warranted. In general, any requests for changes
to the goals and policies or the development standards established in the Plan will be
considered major amendments.
Staff will make every attempt to respond to the request within 30-60 days of receiving sufficient
information from the requestor. The timeframe will allow staff to evaluate the request internally
and gather input from the WD/WMOs and other technical resources, as needed. The response
will describe the staff recommendation and which of the three categories the request falls into.
The response will also outline the schedule for actions, if actions are needed to complete the
requested amendment.
4.WMO Approval
All proposed major amendments must be reviewed and approved by the appropriate Watershed
Management Organizations and Water Districts prior to final adoption of the amendments. Major
amendments would include changes to the goals and policies of the Plan. Staff will review the
proposed amendments with the WD/WMOs to determine if the change is a major amendment
and if determined to be major amendment, then will assess the ability of the requested
amendment to maintain consistency with WD/WMO plans.
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5.Council Consideration
Major amendments and the need for a public hearing will be determined by staff and if identified
as a major amendment, the request will be considered at a regular or special Council meeting.
Staff recommendations will be considered before decisions on appropriate action(s) are made.
The requestor will be given an opportunity to present the basis for, and intended outcomes of, the
request at the public hearing and will be notified of the dates of all official actions relating to the
request.
6.Public Hearing and Council Action
The initiation of a public hearing will allow for public input or input based on public interest in
the requested amendment. Council, with staff recommendations, will determine when the public
hearing should occur in the process. Consistent with other formal Council actions and based on
the public hearing, Council would adopt the amendment(s), deny the amendment(s) or take other
action.
7.Council Adoption
Final action on any major amendments, following approval by the Watershed Management
Organizations and/or Watershed Districts, is Council adoption. Prior to the adoption, an
additional public hearing may be held to review the Plan changes and notify the appropriate
stakeholders.
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APPENDIX A FIGURES
FIGURE 1 CITY LOCATION MAP
FIGURE 2 WATERSHED BOUNDARIES
FIGURE 3 SOIL HYDROLOGIC GROUP
FIGURE 4 EXISTING LAND USE
FIGURE 5 PROPOSED 2020 LAND USE
FIGURE 6 PROTECTED WATERS
FIGURE 7 WATER FEATURES MANAGEMENT CLASS
FIGURE 8 NEIGHBORHOOD STUDY LOCATIONS
FIGURE 9 STORMWATER PONDS
FIGURE 10 NWI WETLANDS
FIGURE 11 MCWD-CITY INVENTORY COMPARISON
FIGURE 12 WETLAND INVENTORY
FIGURE 13 POTENTIAL WETLAND MITIGATION SITES
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APPENDIX B ACRONYMS AND GLOSSARY
Acronyms
AST
Above-ground Storage Tank
BMP
Best Management Practices
BWSR
Minnesota Board of Water and Soil Resources
CCWRMA
Carver County Water Resource Management Area
DNR
Department of Natural Resources
EQB
Minnesota Environmental Quality Board
EQC
Environmental Quality Committee
FEMA
Federal Emergency Management Agency
FIRM
Flood Insurance Rate Map
GIS
Geographic Information System
GPS
Geographic Positioning System
IMP
Integrated Management Practice
LID
Low Impact Development
LMRWD
Lower Minnesota River Watershed District
LUST
Leaking Underground Storage Tank
MCWD
Minnehaha Creek Watershed District
McRAM
Minnehaha Creek Routine Assessment Method
MnDOT
Minnesota Department of Transportation
MnRAM
Minnesota Routine Assessment Method
MPCA
Minnesota Pollution Control Agency
MS4
Municipal Separate Storm Sewer System
MSWMP
Metropolitan Surface Water Management Program
MUSA
Metropolitan Urban Services Area
NOI
Notice of Intent (for coverage under the NPDES Permit Program)
NPDES
National Pollutant Discharge Elimination System
NURP
Nationwide Urban Runoff Program
RPBCWD
Riley-Purgatory-Bluff Creek watershed District
SWCD
Soil and Water Conservation District
SWMP
Surface Water Management Plan
SWPPP
Storm Water Pollution Prevention Program
TP
Total Phosphorus
TSS
Total Suspended Solids
USEPA
United States Environmental Protection Agency
UST
Underground Storage Tank
WD
Watershed District
WMO
Watershed Management Organization
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GLOSSARY
100-Year Flood or 100-Year Storm Event:
The flood having a one-percent (1%) chance of
being equaled or exceeded in any given year. A 100-year flood is synonymous with Base Flood,
Regional or 1% Chance Flood.
Agricultural Land:
Any land designated specifically for agricultural production. This may
include row crops, pasture, hayland, orchards, or land used for horticultural purposes
Anaerobic:
Conditions either in water or soil where there is a lack of oxygen.
Army Corps of Engineers (COE or USCOE):
The United States Army Corps of Engineers is a
regulatory agency involved in design, permitting and construction projects related to or
impacting navigable waters of the United States including lakes, waterways and wetlands.
Aquatic Bench:
A 10- to 15-foot bench around the inside perimeter of a permanent pool that is
approximately one-foot deep. Normally vegetated with emergent plants, the bench augments
pollutant removal, provides habitat, conceals trash and water level drops, and enhances safety.
Best Management Practice (BMP):
A combination of land use, conservation practices, and
management techniques, which when applied to a unit of land will result in the opportunity for a
reasonable economic return with an acceptable level of water quality or water quantity
improvements.
Bluff:
A natural topographic feature such as a hill, cliff, or embankment having the following
characteristics: (1) The slope rises at least 25 feet above the toe of the bluff; and (2) The grade of
the slope from the toe of the bluff to a point 25 feet or more above the toe of the bluff averages
30 percent or greater; and (3) An area with an average slope of less than 18 percent over a
distance for 50 feet or more shall not be considered part of the bluff.
Buffer:
The use of land, topography, difference in elevation, space, fences, or vegetation to
screen or partially screen a use or property from the vision of another use or property, and thus
reduce undesirable influences such as: sight, noise, dust, and other external effects. Also defined
as area immediately adjacent to a wetland that is unmowed and/or unmanaged. Buffers are
ideally dominated by native vegetation and add to the ecological health of the wetland by adding
habitat and assisting and filtering pollutants from surface water runoff.
Buffer Strip:
An area of vegetated ground cover abutting a water body that is intended to
sediment or other pollutants from runoff.
BWSR:
Board of Water and Soil Resources. This is the lead regulatory agency that oversees the
Wetland Conservation Act in the State of Minnesota.
Circular 39:
Wetland classification system developed by United States Fish and Wildlife
Service in 1956 that categorizes wetlands into eight types. This is the same classification system
generally accepted by the State of Minnesota for wetland classification.
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Comprehensive Plan:
As defined in Minnesota Statutes 394.21, the policies, statements, goals
and interrelated plans for private and public land and water use, transportation and community
facilities that guide future development (and growth).
Cowardin Classification:
Wetland classification system developed by the United States Fish
and Wildlife Service in 1979. This system defines wetlands by a tiered system and is more
detailed that the Circular 39 method. The Cowardin System is the classification System used in
the National Wetlands Inventory.
Design Storm:
A rainfall event of specified size and return frequency that is used to calculate
the runoff volume and peak discharge rate to a BMP.
Detention:
The temporary storage of runoff from rainfall and snowmelt events to control peak
discharge rates and provide an opportunity for physical, chemical and biological treatment to
occur.
Development:
The construction, installation or alteration of any structure, the extraction,
clearing or other alteration of terrestrial or aquatic vegetation, land or the course, current or cross
section of any water body or water course or division of land into two (2) or more parcels. See
also re-development, new development and existing development.
Drawdown:
The gradual reduction in water level in a pond BMP due to the combined effect of
infiltration and evaporation.
Draining:
The removal of surface water or ground water from land.
Drop Structure:
Placement of logs with a weir notch across a stream channel. Water flowing
through the weir creates a plunge pool downstream of the structure and creates fish habitat.
Easement:
A grant of one or more property rights by a property owner for use by the public, a
corporation, or another person or entity.
Ecoregion:
Areas of relative homogeneity characterized by distinctive regional ecological
factors, including land use, soils, topography and potential natural vegetation. There are seven
such Ecoregions in the state of Minnesota:
NLF = Northern Lakes and Forests
CHF = North Central Hardwood Forests
NGP = Northern Glaciated Plains
WCP = Western Corn Belt Plains
RRV = Red River Valley
DA = Driftless Area
NMW = Northern Minnesota Wetlands
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Exotic Species or Invasive Species
: Non-native plants or wild animals that can naturalize, have
high propagation potential, are highly competitive for limiting factors, and cause displacement
of, or otherwise threaten, native plants or native animals in their natural communities.
End of Pipe Control:
Water quality control technologies suited for the control of existing urban
storm water at the point of storm sewer discharge to a receiving water. Due to typical space
constraints, these technologies are usually designed to provide water quality control rather than
quantity control.
Erosion:
The wearing away of land surface and soil by the action of natural elements (wind
and/or water).
Eutrophication:
Process by which overabundance of nutrients in a waterbody lead to
accelerated productivity and general decrease in water clarity and quality.
Exfiltration:
The downward movement of runoff through the bottom of an infiltration BMP into
the subsoil.
Existing Development:
A property or parcel of land that has previously been subject to
development, and that is not undeveloped property.
Extended Detention:
A storm water design feature that provides for the gradual release of a
volume of water (typically 0.25 to 1.0 inches per impervious acre) over a 12 to 48 hour time
period. With proper design, the extended detention period allows for an increased settling of
pollutants, and can protect channels from frequent flooding or scour.
Extended Detention (ED) Ponds:
A conventional ED pond temporarily detains a portion of
storm water runoff for a period of 12 to 48 hours after a storm using a fixed orifice. Such
extended detention allows urban pollutants to settle out. ED ponds can be designed to be "dry"
between storm events and thus do not have any permanent standing water or “wet” with a
permanent pool of water. An enhanced ED pond is designed to prevent clogging and
resuspension and provides greater flexibility in achieving target detention times. It may be
equipped with plunge pools near the inlet, a micropool at the outlet, and utilize an adjustable
wet pond
reverse-sloped pipe at the ED control device. See also “” definition for diagram.
Extended Detention Wetland:
A storm water wetland design alternative in which the total
treatment volume is equally split between a shallow marsh and temporary detention of runoff
above the marsh. After a storm, the normal pool of the shallow marsh may rise by up to two feet.
The extra runoff is stored for up to 24 hours to allow pollutants to settle at, before being released
downstream.
Finished Floor Elevation
: The lowest elevation of the first floor or basement in a residential
building or other structure that will or may be inhabited by a person or persons.
Filtration Basin
: A treatment area designed to treat storm water by a process that physically
removes particles from the water.
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Flood:
A temporary rise in stream flow or stage that results in inundation of the areas adjacent to
the channel or water body.
Flood Frequency:
The average frequency, statistically determined, for which it is expected that
a specific flood stage or discharge may be equaled or exceeded.
Flood Fringe:
That portion of the 100-year floodplain outside of the floodway.
Flood Obstruction:
Any dam, well, wharf, embankment, levee, dike, pile, abutment, projection,
excavation, channel rectification, culvert, building, wire, fence, stockpile, refuse, fill, structure or
matter in, along, across or projecting into any channel, watercourse or regulatory flood hazard
area which may impede, retard or change the direction of the flow of water, either in itself or by
catching or collecting debris carried by such water, or that is placed where the flow of water,
either in itself or by catching or collecting debris carried by such water, or that is placed where
the flow of water might carry the same downstream to the damage of life or property.
Floodplain:
Floodplains are lowland areas adjoining lakes, wetlands, and rivers that are
susceptible to inundation of water during a flood. For regulatory purposes, the floodplain is the
area covered by the 100-year flood and it is usually divided into districts called the floodway and
flood fringe. Areas where floodway and flood fringe have not been determined are called
approximate study areas or general floodplain.
Floodplain (General) Area:
The general floodplain area is determined using the best available
data, in lieu of performing a detailed engineering study. These data may be from soils mapping,
experienced high water profiles, aerial photographs of previous floods, or other appropriate
sources. There are no associated published 100-year flood elevations with general floodplain
delineations, unlike detailed study areas. General floodplain area is synonymous with
approximate study area and unnumbered A-Zone.
Floodplain Forest:
Wooded area adjacent to stream or river that is periodically flooded. Within
this plan, floodplain forests have been specifically identified as a separate wetland category due
to their unique ecology and protection needs.
Flood Proofing:
A combination of structural provisions, changes or adjustments to properties
and structures subject to flooding primarily for the reduction or elimination of flood damages to
properties, water and sanitary facilities, structures and contents of buildings in a flood hazard
area in accordance with the Minnesota State Building Code.
Floodway:
The floodway is the channel of a river or other watercourse and the adjacent land
areas which must remain open in order to discharge the 100-year flood.
Forebay:
An extra storage area provided near an inlet of a pond or BMP to trap incoming
sediments, reducing the amount that accumulates in a pond or BMP.
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Freeboard:
A factor of safety usually expressed in feet above a certain flood level. Freeboard
compensates for the many unknown factors (e.g., waves, ice, debris, etc.) that may increase flood
levels beyond the calculated level.
Forbs:
Vegetation that is not a tree, grass or shrub. Usually associated with flowering plants
Geographic Information System (GIS):
Computer database of georeferenced information on
the cities various resources.
Global Positioning System (GPS):
Network of satellites used to map and identify locations on
the earth. For this plan, the GPS unit used was a Trimble GeoXT, which is accurate to within
three feet.
Hydric Soil:
Soils that are saturated, flooded, or ponded long enough during the growing season
to develop anaerobic conditions in the upper part.
Hydrophytic Vegetation:
Macrophytic plant life growing in water, soil, or a substrate that is at
least periodically deficient in oxygen as a result of excessive water content.
Hypereutropic:
A very nutrient-rich lake characterized by frequent and severe nuisance algal
blooms and low transparency.
Impervious Surface:
The portion of the buildable parcel which has a covering which does not
permit water to percolate into the natural soil. Impervious surface shall include, but not be
limited to, buildings, all driveways and parking areas (whether paved or not), sidewalks, patios,
swimming pools, tennis and basketball courts, covered decks, porches, and other structures.
Open, uncovered decks are not considered impervious for the purposes of this ordinance. The use
of patio blocks, paver bricks or class 5 gravel material are considered impervious surfaces as a
majority of water runs-off the surface rather than being absorbed into natural soils underneath.
Some exceptions to these conditions may include paver blocks or pavement systems engineered
to be permeable with the underlying soils suitable for infiltration.
Infiltration Basin:
An impoundment where incoming storm water runoff is stored until it
gradually infiltrates into and through the soil of the basin floor.
Infiltration Trench:
A conventional infiltration trench is a shallow, excavated trench that has
been backfilled with stone to create an underground reservoir. Storm water runoff diverted into
the trench gradually exfiltrates from the bottom of the trench into the subsoil and eventually into
the water table. An enhanced infiltration trench has an extensive pretreatment system to remove
sediment and oil. It requires an on-site geotechnical investigation to determine appropriate
design and location.
Infrastructure:
Public facilities and services, including transportation, storm water pipes,
structures and ponds, water and sewer pipes and structures, telecommunications, recycling and
solid waste disposal, parks and other public spaces, schools, police and fire protection, and health
and welfare services.
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Integrated Management Practice (IMP):
A range of small-scale storm water controls or
practices distributed throughout a site and intended to maintain flow patterns, filter pollutants
and/or re-create or maintain existing site hydrology.
Invasive Species or Exotic Species
: Non-native plants or wild animals that can naturalize, have
high propagation potential, are highly competitive for limiting factors, and cause displacement
of, or otherwise threaten, native plants or native animals in their natural communities.
Local Government Unit (LGU):
Agency that has the primary responsibility of administering
the Wetland Conservation Act. The City of Chanhassen acts as LGU for all wetlands within the
City limits and shares responsibility for basins that border adjacent municipalities.
Lowest Floor:
The lowest floor of a structure, including basement.
Low Impact Development (LID):
An approach to storm water management intended to protect
water resources, reduce storm sewer infrastructure costs and provide a more attractive storm
water management system. LID practices include infiltration systems, bioretention areas, rain
barrels, green roofs, porous pavements and a long list of additional innovative storm water
treatment practices.
Mesotrophic:
Describes a lake of moderate photosynthetic productivity.
MNRAM:
The Minnesota Routine Assessment Methodology as referenced by Minnesota Rules
8420. MNRAM is the primary tool used to assess wetland functions and values on a qualitative
basis. The MNRAM evaluates wetlands based on vegetation, wildlife habitat, water quality,
flood and storm water attenuation, recreational opportunities, aesthetics, fishery habitat,
groundwater interactions, and commercial use. The version referenced in this plan is Version 3.0.
Monotypic:
Used to describe vegetation communities in which only one species is present.
Most often used to describe areas that are entirely dominated by reed canary grass or cattails.
Navigable Waters.
Waters defined by the United States, 33 Code of Federal Regulations
Section 329.4 as those waters that are subject to the ebb and flow of the tide and/or are presently
used, or have been used in the past, or may be susceptible for use to transport interstate or
foreign commerce.
New Development:
Development of a property or portion thereof that is currently undeveloped
property.
NURP:
Nationwide Urban Runoff Program, a study by the U.S. Environmental Protection
Agency. A key component of this program was to assess the effectiveness of urban runoff
detention/retention basins (e.g., ponds) in removing pollutants from storm water runoff.
Off-Line BMP:
A water quality facility designed to treat a portion of storm water (usually 0.5 to
1.0 inches per impervious acre) which has been diverted from a stream or storm drain.
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Off-Line Treatment:
A BMP system that is located outside of the stream channel or drainage
path. A flow diverter is used to divert runoff from the channel and into the BMP for subsequent
treatment.
Ordinary High Water Level (OHWL or OHW):
The boundary of public waters and wetlands,
and shall be an elevation delineating the highest water level which has been maintained for a
sufficient period of time to leave evidence upon the landscape, commonly that point where the
natural vegetation changes from predominantly aquatic to predominantly terrestrial. For
watercourses, the ordinary high water level is the elevation of the top of the bank of the channel.
For reservoirs and flowage, the ordinary high water level is the operating elevation of the normal
summer pool. In Chanhassen all of the lakes have an OHW established. For streams and
waterways, the OHW is considered the top of bank. Areas below the OHW are under the
jurisdiction of the Minnesota Department of Natural Resources and are not regulated by the
Wetland Conservation Act.
Permanent Pool:
A 3- to 10-foot deep pool in a storm water pond system that provides removal
of urban pollutants through settling and biological uptake. (Also referred to as a wet pond).
Porous Pavement:
An alternative to conventional pavement whereby runoff is diverted through
a porous asphalt layer and into an underground stone reservoir. The stored runoff then gradually
infiltrates into the subsoil.
Protected Water:
Any water or wetland designated by the Minnesota Department of Natural
Resources and identified by statute on the Protected Waters Inventory.
Public Waters:
Those waters of the state identified as public waters or wetlands under
Minnesota Statutes, Section 103G.005.
Reach:
A hydraulic engineering term to describe a longitudinal segment of a stream or river
influenced by the natural or man-made obstruction. In an urban area, the segment of a stream or
river between two (2) consecutive bridge crossings would most typically constitute a reach.
Redevelopment:
Any development including but not limited to rebuilding, renovation, revision,
remodel, reconstruction or redesign of or at an existing development.
Regional Flood:
A flood which is representative of large floods known to have occurred
generally in Minnesota and reasonably characteristics of what can be expected to occur on an
average frequency in the magnitude of the 100-year recurrence interval. Regional flood is
synonymous with the term “base flood" used in the Flood Insurance Study.
Regulatory Flood Protection Elevation:
A point not less than one-foot (1') above the water
surface profile associated with the 100-year flood as determined by the use of the 100-year flood
profile and surrounding technical data in the Flood Insurance Study plus any increase in flood
heights attributable to encroachments on the floodplain. It is the elevation to which uses
regulated by City ordinance are required to be elevated or flood proofed.
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Retention:
The permanent storage of runoff from rainfall and snowmelt events with volume
reduction coming from infiltration, evaporation or emergency release.
Riprap:
A combination of large stone, cobbles and boulders used to line channels, stabilize
banks, reduce runoff velocities, or filter out sediment.
Runoff (Storm Water):
The overland and near surface flow from storm water and snowmelt.
Runoff Conveyance:
Methods for safely conveying runoff to a BMP to minimize disruption of
the stream network, and promote infiltration or filtering of the runoff.
Runoff Pretreatment:
Techniques to capture or trap coarse sediments before they enter a BMP
to preserve storage volumes or prevent clogging within the BMP. Examples include forebays and
micropools for pond BMPs, and plunge pools, grass filter strips and filter fabric for infiltration
BMPs.
Sand Filter:
A relatively new technique for treating storm water, whereby the first flush of
runoff is diverted into a self-contained bed of sand. The runoff is then strained through the sand,
collected in underground pipes and returned back to the stream or channel.
Sediment Forebay:
Storm water design feature that employs the use of a small settling basin to
settle out incoming sediments before they are delivered to a storm water BMP. Particularly use
full in tandem with infiltration devices, wet ponds or marshes. See also Forebay.
Sequencing:
The process used by the Local Government Unit to evaluate the necessity of an
activity impacting a wetland. The party proposing the impact must demonstrate that the activity
proposed complies with the following principles in descending order of priority.
1.Avoids direct or indirect impacts to the wetlands that may diminish or destroy them;
2.Minimizes the impact to the wetland by limiting the degree or magnitude of the
wetland activity and its implementation;
3.Rectifies the impacts by repairing, rehabilitating, or restoring the affected wetland;
4.Reduces or eliminates the impact to the wetland over time by preservation and
maintenance operations; and,
5.Replaces unavoidable wetland impacts to the wetland by restoring or, if wetland
restoration opportunities are not reasonably available, creating substitute wetland
areas having equal or greater public value as provided for under the Wetland
Conservation Act.
Shoreland:
Land located within the following distances from public waters: one thousand feet
(1,000') from the ordinary high water level of a lake, pond, or flowage; and three hundred feet
(300') from a river or stream, or the landward extent of a floodplain designated by ordinance on a
river or stream, whichever is greater. The limits of shoreland may be reduced whenever the
waters involved are bounded by topographic divides which extend landward from the waters for
lesser distances and when approved by the Commissioner of the DNR.
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Short Circuiting:
The passage of runoff through a BMP in less than the theoretical or design
treatment time. For example, a properly designed treatment pond will have the inlet and outlet
pipes located as far apart (along the water flow path) as possible. A short circuiting pond would
have the inlet very close to the outlet such that the water coming into the pond would leave the
pond much sooner than if it were able to travel through the entire pond.
Storm Water Treatment:
Detention, retention, filtering or infiltration of a given volume of
storm water to remove pollutants.
Stream Buffer:
A variable width strip of vegetated land adjacent to a stream that is preserved
from a disurbance to protect water quality and aquatic and terrestrial habitats. See also buffer
strip.
Structure:
Anything manufactured, built, constructed, erected, or a portion thereof which is
normally attached to or positioned on land, whether temporary or permanent in character,
including but not limited to buildings, fences, sheds, advertising signs, dog kennels, hard surface
parking areas, boardwalks, playground equipment, concrete slabs.
Shoreland Wetland Protection Zone:
The land located within 1,000 feet from the Ordinary
High Water Elevation of a Protected Water, 500 feet from the Minnesota River or the landward
extent of the designated floodplain, and 300 feet from any stream designated in the shoreline
management ordinance.
Storm Water:
(See Runoff)
Storm Water Treatment Pond:
Any waterbody that has been specifically created to remove
sediment and nutrients and “treat” surface water runoff. Storm water ponds that were created
from existing wetland are still regulated as jurisdictional wetlands. Storm water ponds created
from upland areas are not wetland and are exempt from regulatory jurisdiction.
Subwatershed
: A subdivision based on hydrology corresponding to a smaller drainage area
within a larger watershed.
Technical Evaluation Panel (TEP):
A panel of technical professionals from the Board of
Water and Soil resources, Carver or Hennepin County Conservation Districts, and a Minnesota
Department of Natural Resources representative. Additional members can also be invited,
including the U.S. Army Corps of Engineers. The TEP provides decision making support for the
LGU for many wetland and regulatory issues.
Ten-Day Snow Melt Runoff with Type “C” Distribution (100-Year/10-day runoff):
A
modeled runoff event that represents snowmelt conditions over a 10-day period for a return
period snow depth of 100 years. The runoff event is simulated for a curve number (CN) of 100
which represents frozen soil conditions or where all surfaces are considered impervious. For
some drainage basins the ten-day runoff event is the critical event for identifying the high water
level of the basin or water body. The Type C distribution is similar in concept to the Type I and
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II distributions, and for this event, establishes the time distribution of runoff volume over the ten-
day period.
Treatment Volume (Vt):
The volume of storm water runoff that is treated within a BMP or IMP
storm water treatment facility. Typically the volume is expressed in terms of inches of runoff per
impervious acre.
Type I, IA, II and III Storm Distributions - NRCS
: These storm types represent the time
distribution of a 24-hour rainfall event for areas throughout the United States. The total storm
depth is distributed according to the diagram in subpart A. Type II storms are more “flashy” (i.e.,
convective/thunderstorms) than a Type I or IA storm. Subpart B illustrates that all of Minnesota
is within the Type II rainfall distribution area.
A. SCS 24-hour rainfall distributions (SCS, 1986):
B. Approximate geographic boundaries for SCS rainfall distributions (SCS, 1986):
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Underdrain:
Typically perforated plastic pipes installed on the bottom of a filtration of
infiltration BMP, or sand filter. The under drain is used to collect and remove treated storm water
that exceeds the water holding and/or infiltration capacity of the soil.
Upland:
General term to describe any area that is not a wetland.
Vegetated Filter Strip:
A vegetated section of land designed to accept runoff as overland sheet
flow from upstream development. It may adopt any natural vegetated form, from grassy meadow
to small forest. The dense vegetative cover facilitates pollutant removal. A filter strip cannot treat
high veloCity flows; therefore, they have generally been recommended for use in agriculture and
low-density development. A filter strip can also be an enhanced natural buffer, whereby the
removal capability of the natural buffer is improved through engineering and maintenance
activities such as land grading or the installation of a level spreader. A filter strip differs from a
grassed swale in that a swale is a concave vegetated conveyance system, whereas a filter strip
has a fairly level surface.
Watershed:
A topographically defined area within which all runoff water drains to a point.
Watershed-to-Lake Ratio:
The relative surface area of the contributing watershed to the surface
area of the lake or water body. In terms of water quality, generally the smaller the watershed-to-
lake ratio, the better the quality of the lake. For example a lake with a ratio of 2 to 1 means that
the watershed is twice the size of the surface water itself (i.e., 100 acres contributing to a 50 acre
lake).
Wetland:
Transitional land between terrestrial and aquatic systems where the water table is at or
near the surface or the land is covered by shallow water. For purposes of the plan, wetlands must
have a predominance of hydric soil, be inundated or saturated to the surface or groundwater at a
frequency and duration sufficient to support a prevalence of hydrophytic vegetation typically
adapted for life in saturated soils; and under normal circumstances supports a prevalence of
hydrophytic vegetation.
Wetland Conservation Act (WCA):
In 1991 Minnesota adopted the initial Wetland
Conservation Act (Minnesota Laws Chapter 354) to protect the states wetland resources. This
act has been amended and updated periodically, but is used by reference to the current program,
and any future amendments.
Wetland Delineation
: The process and procedure by which an area is adjudged a wetland or
non-wetland including a determination of the wetland boundary based on the point where the
non-wetland areas shift to wetlands or aquatic habitats.
Wetland Mitigation:
Wetlands created to replace wetland areas destroyed or impacted by land
disturbances.
Wet Pond:
A conventional wet pond has a permanent pool of water for treating incoming storm
water runoff and a live storage component for flood storage and additional water quality
treatment detention (see typical cross section in Appendix D).
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APPENDIX C LITERATURE REVIEW AND WEBSITE LINKS
Literature Review
1.Barr Engineering. July 1999. Lake Lucy and Lake Ann Use Attainability Analysis.
Prepared for the Riley-Purgatory-Bluff Creek Watershed District.
2.Barr Engineering. December 1999. Lake Susan and Rice Marsh Lake Use Attainability
Analysis. Prepared for the Riley-Purgatory-Bluff Creek Watershed District.
3.Barr Engineering. April 2002. Lake Riley Use Attainability Analysis Prepared for the
Riley-Purgatory-Bluff Creek Watershed District.
4.Blue Water Science. February 2002. Christmas Lake, Chanhassen, Minnesota Aquatic
Plant Surveys for 2001.
5.Blue Water Science. 1994. City of Chanhassen Lake Data for 1994.
6.Blue Water Science. 1995. Lake Minnewashta Lake Management Plan.
7.Blue Water Science. June 1996. Christmas Lake Management Plant June 1996.
8.Blue Water Science. February 2002. Lake Minnewashta, Chanhassen, Minnesota Aquatic
Plant Surveys for 2001.
9.Blue Water Science. November 1998. Lake St. Joe Management Plan.
10.Blue Water Science. April 2002. Lake St. Joe, Chanhassen, Minnesota Aquatic Plant
Surveys for 2001.
11.Blue Water Science. May 2004. Aquatic Plant Surveys for Ann Lake, Chanhassen,
Minnesota.
12.Blue Water Science. May 2004. Aquatic Plant Surveys for Lotus Lake, Chanhassen,
Minnesota.
13.Blue Water Science. May 2004. Aquatic Plant Surveys for Lake Lucy, Chanhassen,
Minnesota.
14.Blue Water Science. August 1998. Lake Lucy Management Plan.
15.Blue Water Science. May 2004. Aquatic Plant Surveys for Lake Susan, Chanhassen,
Minnesota.
16.Blue Water Science. January 2004. Chanhassen Water Quality Monitoring Results for
Lakes Ann, Lucy, Rice Marsh, and Susan for 2003.
17.Blue Water Science. May 2004. Aquatic Plant Surveys for Rice Marsh Lake,
Chanhassen, Minnesota.
18.Blue Water Science. February 2002. Lake Riley, Chanhassen, Minnesota Aquatic Plant
Surveys for 2001.
19.Blue Water Science. January 2000. Lake Susan Restoration Evaluation for 1999.
20.Blue Water Science. February 1999. Lake Susan Restoration Evaluation for 1998.
21.Blue Water Science. February 2001. Lake Susan Restoration Evaluation for 2000.
22.Blue Water Science. February 1998. Lake Susan Management Plan.
23.Bonestroo Rosene Anderlik & Associates. December 1996. Bluff Creek Watershed
Natural Resources Management Plan.
24.Bonestroo Rosene Anderlik & Associates. 1994. City of Chanhassen Surface Water
Management Plan.
25.Carver County Water Management Area. June 2001. Carver County Water Management
Plan.
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26.Chanhassen, City of. 1998. Comprehensive Plan.
27.Cowardin, L.M., V. Carter, F.C. Golet, R.T. LaRoe. 1979. Classification of Wetlands and
Deepwater Habitats of the United States. U.S. Fish and Wildlife Service,
FWS/OBS079/31, 103 pp.
28.Eggers, S.D. & D.M. Reed. 1997. Wetland Plants and Plant Communities of Minnesota
& Wisconsin. 2nd edition. US Army Corps of Engineers, St. Paul.
29.Lower Minnesota River Watershed District. 1999. Lower Minnesota River Watershed
District Water Management Plan.
30.Minnesota Department of Natural Resources Protected Waters and Wetlands Inventory
Map, Carver County, Electronic format.
31.Minnesota Department of Natural Resources Protected Waters and Wetlands Inventory
Map, Hennepin County, Electronic format.
32.Minnesota Pollution Control Agency. March 2000. Protecting Water Quality in Urban
Areas, Best Management Practices for Dealing with Storm Water Runoff from Urban,
Suburban and Developing Areas of Minnesota.
33.Minnesota Stormwater Steering Committee. November 2005. Minnesota Stormwater
Manual.
34.Riley Purgatory Bluff Creek Watershed District. May 1996. Riley Purgatory Bluff Creek
Watershed District Water Management Plan.
35.Shaw, S. and C.G. Fredine. 1956. Wetlands of the United States Circular 39. U.S. Fish
and Wildlife Service. U.S. Government Printing Office, Washington, D.C.
36.Thill, D., and M. Jacobson. 2000. The Minnehaha Creek Routine Assessment Method, in
conjunction with the Minnehaha Creek Watershed District.
37.U.S. Department of the Interior, 1988. National List of Plant Species that Occur in
Wetlands: North Central (Region 3). Biological Report 88 (26.3), Fish and Wildlife
Service. In cooperation with the National and Regional Interagency Review Panels.
Washington, D.C.
38.U.S. Army Corps of Engineers, 1987. Corps of Engineers Wetlands Delineation Manual.
Technical Report Y-87-1. Waterways Experiment Station, Vicksburg, Mississippi.
39.Wenck Associates, Inc. 1997. Minnehaha Creek Watershed District Water Resources
Management Plan.
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Water Management Agency/Organization Contacts
Numerous agencies and organizations in Minnesota have varying authorities and/or interest in
surface water management activities relative to the City‘s Plan. A summary of these agencies
and organizations is listed below with a link to their respective website at the time this Plan was
created. More detailed information is available on each web page including contacts and key
responsibilities relative to surface water management.
Agency/Organization Website Link
State
MN Pollution Control Agency http://www.pca.state.mn.us
MN Department of Natural Resources http://www.dnr.state.mn.us
Board of Water and Soil Resources http://www.bwsr.state.mn.us
Local
City of Chanhassen http://www.ci.chanhassen.mn.us
Carver County WMO http://www.co.carver.mn.us/water
Hennepin County http://www.co.hennepin.mn.us
Watersheds
Lower Minnesota River WD http://www.watersheddistrict.org
Minnehaha Creek WD http://www.minnehahacreek.org
Riley Purgatory Bluff Creek WD http://www.rileypurgatorybluffcreek.org
Federal
US Army Corps of Engineers http://www.usace.army.mil
Natural Resources Conservation Service http://www.nrcs.usda.gov
Federal Emergency Management Agency http://www.fema.gov
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APPENDIX D DEVELOPMENT STANDARDS
These development standards are intended to be used by developers and/or project proposers in
design and layout of their site plans and water management features. These standards do not
replace or supercede City ordinances, watershed district regulations, state and federal rules or
permits required for the project. The standards have been updated from the original standards
completed as part of the City’s 1994 Surface Water Management Plan. These standards have not
been adopted, but include recommendations for ordinance revisions.
All plans shall be reviewed and stamped “Approved by the City Engineer” and all applicable
permits must be obtained prior to commencing construction. For all newly constructed storm
water facilities (ponds, retention areas, infiltration basins, storm sewer, etc.) or existing facilities
that are modified, as-built plans shall be prepared by the developer. As-built plans shall be
signed and certified by a licensed professional engineer in the State of Minnesota and record
drawings shall be provided to the City. The City has standard details available for many typical
storm structures (e.g., storm sewer, outlet structures, catch basins, sump manholes, etc.) on the
City’s website (www.ci.chanhassen.mn.us).
A maintenance agreement may also be required by the City. An example agreement for ponds is
provided at the end of this appendix. The agreement may be modified to address a wide range of
BMPs (infiltration systems, retention areas, grit chambers, etc.) with the addition of maintenance
activities and schedules specific to the selected BMP. Recommended maintenance activities may
be found at number of sources including the Stormwater Manager’s Research Center website
http://www.stormwatercenter.net.
Standards summarized in this Plan consist of the following major sections:
General Elements
Facility Design Elements
Erosion and Sediment Control
Wetland Elements
GENERAL ELEMENTS
A. Hydrologic Analysis
1.Storm distributions and storm volumes for hydrologic analysis shall be based upon
Hershfield, D.M., 1961, Rainfall Frequency Atlas of the United States for Durations of 30
Minutes to 24 Hours and Return Periods from 1 to 100 Years, Technical Publication No. 40
(TP-40).
2.Design of major facilities (e.g., ponds, detention areas, retention areas) shall be based on the
U.S.D.A. NRCS methods, 100-year return period, 24-hour duration, type II distribution with
average soil moisture conditions (AMC-2). The analysis of flood levels, storage volumes and
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discharge rates for detention basins shall utilize the design storm/freeboard evaluation storm
concept.
3.Minor drainage systems (storm sewer) shall be analyzed and designed to protect for the
10-year frequency rainfall, and shall be evaluated for the 100-year frequency rainfall. Full
pipe flow analysis shall be used unless special conditions can be demonstrated to consider
pressure flow.
4.The Rational Method is the accepted design method for the design of minor systems (storm
sewer). The preferred method of design would be a method utilizing a hydrograph approach
with factors for land use and soil moisture conditions. NRCS methodology is not acceptable
for minor system design unless approved by the City Engineer.
5.Landlocked storm water basins shall be designed to hold back-to-back 100-year storms. For
landlocked areas, available freeboard and infiltration capacity of in-place soils should be
analyzed (if analyzed for unfrozen soil conditions).
B. Peak Discharge Rates
1.Peak storm water discharge rates and storage volumes from any drainage area, watershed,
subwatershed, detention basin, wetland or conveyor shall be consistent with the values shown
in this plan for the 100-year storm event.
2.No increase in peak discharge may result from the proposed project for the 1 or 2-year storm,
the 10-year storm and the 100-year storm event. Variances may be allowed if computations
can be provided which demonstrate no adverse downstream effects will result from the
proposed system. Cumulative storm depths for the required events are:
2-Year – 2.8-inches
10-Year = 4.2 inches
100-Year = 6.0 inches
C. General Facility Planning
1.Developments shall maximize preservation and use of natural detention areas and regional
detention areas shall be used to the greatest practical extent. Multiple purpose detention areas
are encouraged to maximize maintenance efficiency within proposed developments while
providing the proper flood control and water quality features.
2.The construction of detention basins will involve the direct participation of individual
developers. Where regional basins serve multiple properties and may lie outside of the
ownership of the specific development, the City and WDs will take an active role on
implementing policy. Because the basis for the hydrology is based on the developer’s grading
plan, the developer is required to obtain and submit the certification of a licensed engineer
that the detention areas are constructed to the specifications of the approved design.
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MAJOR FACILITY DESIGN ELEMENTS
A. Facility Design Criteria
1.For design or modification of storm water facilities, the following criteria shall be followed:
a.All hydrologic data and computations shall be based on NRCS (formerly SCS)
methodology. Computer modeling may be completed using HydroCAD, TR20/TR55,
SWMM or comparable City-approved modeling software.
b.Hydraulic computations shall be completed using the rational method for storm sewer
design, or in commonly used software packages including FHWA HY-8, Geopack,
Eagle Point or SWMM compatible software.
c.Water quality modeling shall be completed using Pondnet, P8 Urban Catchment
Model, SLAMM or comparable software.
d.Outlet structure designs shall provide rate controls that limit post-project rates to not
exceed existing rates for 1 or 2-year, 10-year, 100-year events and 100-year/10-day
snowmelt.
e.An emergency overflow spillway shall be identified and designed to convey storm
flows from events greater than the 100-year event. Extreme events (on the order of a
10.0 inch event) shall be analyzed to ensure the emergency overflow spillway will
function as designed. An emergency overflow shall be set an elevation at least 1.5
feet below the lowest adjacent low building elevation.
f.Maximum 3:1 (H:V) side slopes (see diagram that follows).
g.10:1 (H:V) safety bench from normal water level (see diagram that follows).
h.For basins intended to have permanent water levels, a minimum of four feet of
standing water (dead storage depth) and a maximum of ten feet shall be provided.
i.Proper allowance shall be made for future access and maintenance. Easements shall
be greater than or equal to 20 feet wide.
j.Separation between the inlet(s) and outlet shall be maximized to prevent short-
circuiting.
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2.The facility design shall provide adequate live storage to provide protection from the design
storm, consistent with lowest building elevation standards. Lowest building elevation is
defined as the lowest slab elevation for a home or building, including basements and crawl
spaces. The lowest building elevation for structures adjacent to wetlands and water bodies
shall be an elevation three feet above the 100-year high water level.
3.Newly constructed or modified detention basins shall provide storage volume below the
outlet (dead storage) to allow for water quality treatment in accordance with the following,
whichever is most restrictive:
a.Water quality features meeting the MPCA NPDES construction permit for Permanent
Storm Water Management Systems;
b.Water quality treatment consistent with NURP criteria (90% removal of TSS and
60% removal of TP for a standard NURP particle size distribution); and/or
c.For proposed projects in a watershed that directly discharges to a ‘Preserve’ water
feature (Table 20 of SWMP), NURP plus enhanced treatment is required as listed
below:
1.Storm water ponds are required to include a sediment forebay at the inlet.
The volume of the sediment forebay should be 5 – 15% of the permanent
pool surface area. The sediment forebay shall be a minimum of 3 feet plus
the depth for sediment storage.
2.Projects in watersheds that discharge directly to Assumption Creek must
incorporate BMPs as outlined in Appendix A C.1, C.2, C.3 and C.5 of the
MPCA NPDES Construction General Permit, and as listed below:
1.During construction.
a.All exposed soil areas with a slope of 3:1 or steeper, that have a
continuous positive slope to a special water must have
temporary erosion protectionpermanentcover
or within 3
days after the area is no longer actively being worked. All
other slopes that have a continuous positive slope to a special
temporary erosion protectionpermanent
water must have or
cover
within 7 days after the area is no longer actively being
worked.
b.Temporary sediment basin requirements described in Part
III.B.1-5 must be used for common drainage locations that
serve an area with five (5) or more acres disturbed at one time.
water quality volume
2.Post construction. The that must be treated by
storm water
the project’s permanent management system described in
impervious
Part III.C. shall be one (1) inch of runoff from the new
surfaces
created by the project.
3.Buffer zone. An undisturbed buffer zone of not less than 100 linear
feet from the special water (not including tributaries) shall be
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maintained at all times. Exceptions from this requirement for areas,
such as water crossings or limited water access, are allowed if the
PermitteeSWPPP
fully documents in the the circumstances and
reasons that the buffer encroachment is necessary. All potential water
quality, scenic and other environmental impacts of these exceptions
SWPPP
must be minimized and documented in the for the project.
storm water
4.Temperature Controls. The permanent management
system must be designed such that the discharge from the project will
minimize any increase in the temperature of trout stream receiving
waters resulting from the 1, and 2-year 24-hour precipitation events.
This includes all tributaries of designated trout streams within the
section that the trout stream is located. Projects that discharge to trout
streams must minimize the impact using one or more of the following
measures, in order of preference:
impervious surfaces
a.Minimize new .
impervious surfaces
b.Minimize the discharge from connected
by discharging to vegetated areas, or grass swales, and through
the use of other non-structural controls.
c.Infiltration or evapotranspiration of runoff in excess of pre-
project conditions (up to the 2-year 24-hour precipitation
event).
d.If ponding is used, the design must include an appropriate
combination of measures such as shading, filtered bottom
wetland
withdrawal, vegetated swale discharges or constructed
treatment cells that will limit temperature increases. The pond
should be designed to draw down in 24 hours or less.
e.Other methods that will minimize any increase in the
temperature of the trout stream.
d.For proposed projects in a watershed that directly discharges to an ‘Improve 1’
(Table 20 of SWMP) water feature NURP plus enhanced treatment is required as
listed below:
1.Storm water ponds are required to include a sediment forebay at the inlet.
The volume of the sediment forebay should be 5 – 15% of the permanent
pool surface area. The sediment forebay shall be a minimum of 3 feet plus
the depth for sediment storage.
2.Projects in watersheds that discharge directly to Riley or Bluff Creeks must
analyze the downstream system to ensure there is no increase in runoff rates.
One way to determine the downstream effects is to extend the analysis
downstream to a point where the proposed development represents less than
ten percent of the total watershed draining to that point.
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B. Skimmers and Outlets
1.Skimming devices should be designed to remove oils and floatable materials up to a one-year
frequency event. The skimmer should be set 12 inches below the normal surface water
elevation and should control the discharge velocity to 0.5 fps.
2.Outlets shall be evaluated for the need to dissipate energy so as to reduce velocities to
permissible levels as allowed by the soil and vegetation. At a minimum, flared end sections
should be provided with riprap consistent with Mn/DOT standards. For areas with high flows
or where excessive erosion occurs or is anticipated, energy dissipation per Federal Highway
Administration standards shall be followed.
3.Riprap shall be provided below the channel grade and above the outfall or channel bottom to
insure that riprap will not be underminded by scour or rendered ineffective by displacement.
Riprap consisting of natural angular stone suitably graded by weight shall be designed for
anticipated velocities. Riprap shall be placed over a suitable filter material or filter fabric to
insure that soil particles do not move through the riprap and reduce its stability.
4.For outlets through berms or roadway embankments and all culverts under public traveled
streets, anti-seepage collars shall be used (see diagram in this section). The collars shall be
installed so as to increase the creep distance or seepage line along conduit by 15 percent. The
locations for the use of collars include:
a.All water and pond structures with a pool depth of two feet and two-day duration.
b.250 Acre watershed or more.
c.Design head of 10 feet or more.
EROSION AND SEDIMENT CONTROL
A. Erosion and Sediment Control Plans
1.An erosion and sediment control plan shall be created for any land disturbing activity.
Erosion and sediment control elements shall be implemented before any grading can begin. A
schedule of significant grading work will be required as part of the erosion and sediment
control plan.
2.The MPCA’s most recent version of the NPDES Construction Storm Water Permit shall be
used to develop sediment and erosion control plans. Where the NPDES permit conflicts with
City standards, the more stringent standard will apply.
3.Site access roads (entrances to construction sites) shall be graded or otherwise protected with
silt fences, diversion channels or dikes and pipes to prevent sediment from exiting the site via
the access road. Primary site access roads shall be surfaced with crushed rock or wood chips.
The rock entrance shall extend for a distance of 75 feet (150 for wood chips) beginning at
existing paved surface. All construction traffic shall utilize the entire length of the rock
entrance.
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4.Soil tracked from the site by motor vehicles shall be cleaned from paved roadway surfaces at
least daily or as needed throughout the duration of construction. Roadway cleaning shall be
the responsibility of the party or parties having a permit with the City.
5.Streambank stabilization and stream bed control structures shall be designed based on the
unique site conditions present including soil conditions, flow rate, slope, and flow velocity.
6.Where inadequate natural vegetation exists or where it becomes necessary to remove existing
natural vegetation, both temporary vegetative and permanent vegetative cover shall be
addressed in the plans and specifications and be consistent with the provisions of the NPDES
Construction permit.
B. Sediment Basins
1.Detention basins may be used as temporary sediment retention during the construction phase.
The design should include providing permanent storage volume for construction and
restoration phase sediment accumulation or the removal of the sediment to restore the
required permanent pool volume in the detention area.
2.Detention areas intended to permanently trap sediments shall provide excess dead storage
beyond the required water quality volume, to allow for sediment accumulation. Sediment
basins shall be capable of removing coarse suspended sediment from storm water for all
runoff events and the greatest practical grain size (#40 typically). Sediment storage volume
should be estimated by the universal soil loss equation and 0.5 tons per watershed acre per
year. Volume below the outlet can be estimated by using the runoff volume resulting from a
2.5” rainfall.
WETLAND ELEMENTS
A.Wetland Alteration
1.Wetland alteration will only be allowed with the approval of and receipt appropriate permits
from the City, the water management organization, watershed district, the Department of
Natural Resources, and the U.S. Army corps of Engineers. Mitigation efforts shall be
determined by the review agencies.
2.Water level fluctuations (peak elevation and duration) for wetlands shall be limited to two
feet and duration not to exceed 48 hours so as to prevent the destruction of wildlife habitat
and wetland vegetation.
3.Mitigation for WCA approved impacts is required within the same watershed. In the areas of
the City that is within the Minnehaha Creek Watershed District, 1:1 mitigation is required for
excavation within wetlands. This will be addressed during ordinance adoption for the
Wetland Ordinance.
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4.Sedimentation basins or sediment removal devices must be provided prior to discharge into
wetlands.
5.Variable bottom contours should be considered to provide deeper holes and flat shallow
benches. This feature will provide habitat for diversity of plants and wetland inhabitants for
wetland mitigation sites and storm water basins.
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MAINTENTANCE AGREEMENT (EXAMPLE)
REGARDING STORM WATER MANAGEMENT PRACTICES:
WATER QUALITY AND QUANTITY TREATMENT POND
I. THIS AGREEMENT made this ______ day of _____, 200__ by and among the City of
Chanhassen, Minnesota (hereinafter referred to as the “City”) and,
________________________________, a _____________________ [corporation, individual]
(hereinafter referred to as “__________________”) with reference to the following facts and
circumstances:
A. (*) is the fee owner of certain real
property situated in the City of __________________, legally described as follows:
(Legal) ,
(*) CAPS ( )
(hereinafter referred to as the “Subject Property”).
B. As a condition of its approval of the development for the Subject Property, the City has
required that the parties hereto enter into an agreement, which makes provision for the
maintenance of the Storm Water Management Practice located within the boundaries of
the Subject Property as the same is described and depicted in those certain construction
plans drawn by , approved by the City and
constructed by . The Storm Water Management
Practice is located in the platted drainage and utility easement in
.
1.The parties hereto desire to set forth their agreement with respect to the maintenance of
the Storm Water Management Practice and the costs of such maintenance.
II. NOW THEREFORE, in consideration of the foregoing facts and circumstances, and for
other good and valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the parties hereto hereby agree as follows:
A. For the purposes of this Agreement, maintenance of the Storm Water Management
Practice shall mean the annual inspection and certification by a qualified individual that
the pond, including the pond outlet, is functioning in accordance with the approved plans
and, if necessary, the periodic removal of the buildup in the Storm Water Management
Practice as necessary to maintain function, as established for the Storm Water
Management Practice in the construction plans and to maintain the proper operation of
the treatment function of the Storm Water Management Practice.
B. (*) shall be solely responsible
for the maintenance of the Storm Water Management Practice, and shall bear all costs of
such maintenance, until such time as ________________________ (hereinafter referred
to as the “Association”) is activated pursuant to Article _________________, Section
________________, of the Declaration of Covenants for _________________________,
whereupon the Association shall bear the sole responsibility for such maintenance and
shall bear all costs of such maintenance. If (*) , or after its
incorporation, the Association, does not undertake the necessary maintenance within
30 days of notification by the City, or within 30 days provide the City with a schedule for
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undertaking the necessary maintenance, the City may undertake such maintenance, and
the costs reasonably incurred by the City for performing such maintenance shall be
reimbursed to the City within 30 days by the party responsible for such maintenance and,
if the responsible party does not timely reimburse the City, then the City may recover its
costs by levying a special assessment against all single family house lots in the Subject
Property, each lot to bear an equal share.
C. (*) , as present owner of the Subject Property,
for itself and respective successors and assigns, hereby waives any statutory right which
it may have to contest any such assessment by the City of its maintenance costs on the
basis of the benefit to portions of the Subject Property.
D. Notwithstanding anything contained in this Agreement to the contrary, in the event the
City shall establish a policy for maintenance by the City of Storm Water Management
Practices located elsewhere in the City of Chanhassen, under which policy the costs of
such maintenance are to be paid either out of general City revenues or by collection of
utility or service fees or charges, then any owner of any portion of the Subject Property
shall be entitled to petition the City for the inclusion of the Storm Water Management
Practice under such maintenance program, and the City shall consent to such request and
thereupon authorize the termination of this Agreement. The recording of a certified copy
of the Resolution of the City Council of the City which sets forth the consent and
authorization described in the foregoing sentence shall serve the terminate this
Agreement, without further action on the part of any party hereto.
E. The terms and conditions of this Agreement shall be binding upon, and shall insure to the
benefit of, the parties hereto and their respective successors and assigns.
III. IN WITNESS WHEREOF, the parties hereto have caused this document to be executed
as of the day and year first above written.
____________________________________ ____________________________________
Date
Title ________________________________
for the City of Chanhassen, Minnesota
____________________________________ ____________________________________
[Corporation/individual] Date
THIS INSTRUMENT DRAFTED BY ______________________________________________
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APPENDIX E HYDROLOGIC SYSTEM TABLES
DESCRIPTION OF TABLE HEADINGS AND DATA
Column Description
1.Subwatershed ID. Corresponds to the subwatershed in both the HydroCAD model
and Figure 2.
2.Drainage Area. Area of the subwatershed listed in column 1 in acres.
3.Weighted curve number (CN). The weighted average CN based on a GIS analysis of
the individual areas of each combination of land-use type and soil hydrologic group
type in the subwatershed.
4.Time of Concentration. The time used in the hydrologic model that represents the
longest flow path, in hydrological time, to the outlet of the subwatershed. Also the
time when the entire watershed is contributing runoff to the outlet.
5.Pond Name. The specific pond ID as show in the HydroCAD model and Figure 2.
6.Pond Type. The type of basin – nutrient trap, wetland, lake, pond, etc.
7.Pond Surface at the NWL. The approximate area in acres of the pond or basin (lake,
wetland, etc) at the normal water level.
8.Ratio of Pond Area to Subwatershed Area – in percent (%). Column 7 divided by
column 2.
9.Ratio of Pond Area to Subwatershed Area – >1 %. This, along with the actual
percent in the previous column, is a first cut look at the relative size of the basin to
the contributing subwatershed. Generally speaking if less than 1 percent there is
likely a need for additional treatment in the subwatershed. Looking downstream to
the next basin will help determine if there is additional regional treatment capacity
(and how much) beyond the initial basin.
10.Outlet Description. The size and type of outlet for each basin as used in the
hydrologic model. To the extent these data were available in as-built plans or field
survey data, they were updated from the previous 1994 Plan data.
11.NWL. Normal water level of the basin, which is generally determined by the area at
the elevation of the outlet invert.
12.OHWL. Ordinary High Water Level is a regulatory term defined by the Minnesota
Department of Natural Resources to represent the long-term conditions of a water
body. The data area only listed for lakes that have data from DNR on the Lake finder
website.
13.100-Year Event – HWL. The results from the hydrologic modeling for the
basin/pond.
14.100-Year Event – BFE. The regulatory Base Flood Elevation defined in the flood
insurance rate study and effective flood mapping. Only basins with a defined BFE
are noted with an elevation.
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15.100-Year Event – Flood Storage. The estimated live storage volume calculated as the
volume between the NWL and the top of the basin at the natural overflow point.
16.100-Year Event – Peak Outflow Rate. The peak discharge rate from the basin as
determined in the HydroCAD model for the 100-year storm event.
17.Approximate Overflow Elevation. The point/elevation at which the runoff water
would overflow from the basin if there is (or were) no other outlet structure.
18.Outflow P-Concentration. Taken from the 1994 Plan, from which a POND NET
model was used to develop an estimate of the average annual Phosphorus loading
generated from the subwatershed (see 1994 Plan Page III-2). The estimate was used
to design (conceptually) the recommended treatment for each watershed and the
priority water bodies. An ultimate conditions model was created and improvements
were modeled under full development conditions.
19.P-Removal Efficiency. See Column 18 description.
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APPENDIX F LAKE BACKGROUND INFORMATION
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APPENDIX G NEIGHBORHOOD STUDIES
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APPENDIX H GOALS AND POLICIES
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Complete Listing of Goals and Policies (Tables 6, 8, 10, 12, 14, 16, 18)
Goal Statement: Provide at least 100-year (1% chance) flood protection for all persons and
structures.
Policy No. Goal 1. Water Quantity – Policies
1 Establish building elevations to provide at least 3 feet of freeboard adjacent to ponding
areas and floodplains as an area develops or when drainage facilities are constructed for an
area.
2 Establish and maintain overflow routes for ponds and low areas to provide relief during
storm conditions that exceed design conditions.
3 Newly constructed stormwater facilities will be designed, operated, and maintained in
accordance with this Plan.
4 Where possible, regional ponding areas, as opposed to individual on-site ponds, should be
used to reduce flooding, to control discharge rates, and to provide necessary storage
volumes as indicated in this Plan.
5 As opportunities allow through development, redevelopment, and infrastructure
replacement, stormwater facilities should be built or upgraded to provide or improve flood
management and water quality.
6 Encourage the development of new and improvement of existing ponds located upstream of
priority water bodies.
7 Permanently protect surface water impoundments and drainage systems by requiring the
dedication of land and/or protective easements as required.
8 Creative and innovative Best Management Practices, including infiltration, shall be
promoted within the limitations imposed by construction practices, soil conditions,
groundwater supply and recharge, safety, snow removal, and maintenance.
9 Continue to stringently enforce impervious surface requirements as set forth in City Code
and development contracts.
10 Require all developments to construct nutrient detention ponds, or enlarge regional ponds,
for the purpose of reducing peak flows generated by the subject development, in accordance
with Minnesota Statute 462.358, and in the general location indicated by the Surface Water
Management Plan.
11 Preserve existing water storage below 100-year flood elevation.
Goal Statement: Achieve water quality standards in lakes, streams, and wetlands consistent with
their designated use and established classifications.
Policy No. Goal 2. Water Quality – Policies
1 Categorize and manage each water body in the City’s surface water system to best meet
state, local, and federal water quality standards.
2 Establish and implement on-going program designed to educate land owners in sensitive
water quality management practices and develop and maintain a public education program
to promote reduction of nutrient and sediment loading to water bodies.
3 Continue to monitor long term water quality trends on prioritized water bodies.
4 Focus management activities and capital improvements based on the priority ranking
scheme included in this Plan. Update priorities annually with a 5 year horizon.
5 Evaluate the progress of surface water management on an annual basis in conjunction with
the annual City Council Report/NPDES MS4 annual report.
6 The City may, at its own discretion, require construction of a higher level of treatment
than required in the standards of this Plan, when it is determined that it is necessary to
maintain the integrity of water quality in downstream priority water bodies.
7 City will lead by example by following the standards of this Plan and encouraging BMPs
to provide pollution prevention and water quality treatment on City-initiated projects.
8 The City will encourage residents and landowners to practice environmentally friendly
lawn care and housekeeping practices, and the use of native planting or natural landscapes
rather than turf lawns, where appropriate.
Chanhassen, MN H-2
nd
2 Generation: Surface Water Management Plan August 2006
9 Prohibit the discharge of foreign material into the storm water system. Such material shall
include, but not be limited to, waste oil, paint, grass clippings, leaves, commercial
fertilizers, and miscellaneous chemicals.
10 Develop and implement a spill response program for the City personnel to prevent
discharge of spilled materials into the storm sewer system. The response program should
focus on containing, neutralizing, and properly disposing of spilled materials. The Fire
Department, Public Safety Department, and Public Works Department should have a
readily available supply of response material including oil absorbing pads.
11 Require all developments to construct nutrient detention ponds, or enlarge regional ponds,
for the purpose of treating increased runoff generated by the subject development, in
accordance with Minnesota Statute 462.358, and in the general location indicated by the
Surface Water Management Plan.
12 Continue to implement the erosion and sediment control policies and the construction site
inspection program to ensure reduction of water quality impacts from lack of erosion and
sediment control.
Goal Statement: Protect and rehabilitate wetlands to maintain or improve their function
and value.
Policy No. Goal 3. Wetland Protection – Policies
1 Develop and maintain an official wetlands map that classifies wetlands by function and
value.
2 Adopt and keep current ordinances and standards designed to protect wetlands.
3 Wetland alteration, where allowed, should be the basis of “no net loss”. If wetland impacts
are unavoidable, they should be mitigated through replacement, wetland conversion,
and/or improvements to wetland function and value.
4 Adopt the storm water and water quality management practices designed to protect
wetland functions and values. Introduction of storm water runoff should be allowed only
when it is demonstrated that wetlands will not be adversely impacted.
5 Adopt an ordinance in compliance with the Minnesota Wetlands Conservation Act of
1991 for no net loss in quantity and quality of jurisdictional wetlands.
Goal Statement: Minimize soil erosion and sedimentation.
Policy No. Goal 4. Erosion and Sediment Control – Policies
1 Erosion and sediment control practices are necessary on all construction sites and on sites
experiencing erosion control problems.
2 Best Management Practices should be used at all construction sites per the Minnesota
Pollution Control Agency’s “Minnesota Urban Small Sites BMP Manual” (2001), the
Minnesota Pollution Control Agency’s “Protecting Water Quality in Urban Areas” (2000),
and/or the Minnesota Pollution Control Agency 2005 Storm Water Manual.
3 Disturbances to existing vegetation (trees, turf grass, native vegetation, etc.) should be
minimized.
4 The City will continue to work with Carver County SWCD to inspect construction sites
for erosion and sediment control issues once every 2 weeks and after every 0.5-inch rain
event.
5 The City will maintain and educate the public on the Clean Water Hotline. This hotline is
used to report erosion and sediment control issues on sites, and to report any water quality
issues.
6 Graded areas should be protected using erosion and sediment control Best Management
Practices to reduce erosion in a manner consistent with the standards of this Plan. Streets
will be frequently swept where construction activities spill and or track sediments onto
streets. In areas undergoing construction activities, the cost of sweeping sediment from the
streets generated by development should be borne by the developer and/or home builder.
7 Stockpiled soil (and/or like-materials) should be protected to prevent erosion.
Chanhassen, MN H-3
nd
2 Generation: Surface Water Management Plan August 2006
8 Effective energy dissipation devices should be provided at all conveyance system
discharge points to prevent bank, channel, or shoreline erosion. Design of stream bank
stabilization and streambed control measures should consider unique or special site
conditions, energy dissipation potential, adverse effects, preservation of natural processes
and aesthetics, in addition to standard engineering and economic criteria.
9 Update City Specifications annually to reflect current technology for erosion and sediment
control.
Goal Statement: Establish and maintain funding sources to finance surface water management
activities.
Policy No. Goal 5. Finance Policies
1 Revise, implement, and maintain a financing strategy for surface water improvements
utilizing a combination of storm water utility fees, special assessments, surface water
management plan connection charges, and storm water program grant funds.
2 Require all new development to pay connection charges for water quality and water
quantity to finance downstream improvements to accommodate new developments.
3 Continue to collect storm water utility fees from all parcels within Chanhassen (exempting
public ROW and lakes), to reflect the service provided by the City for storm water
management and associated operational costs.
Goal Statement: Maintain primary responsibility for managing water resources at the local level but
continue coordination and cooperation with other agencies and organizations.
Policy No. Goal 6. Regulatory Responsiblity – Policies
1 Adopt policies consistent with local watershed authorities’ management plans.
2 This plan and all subsequent amendments shall be consistent with the plans of regulatory
agencies.
3 This plan will be amended as necessary to remain current.
4 Coordinate projects and information with government agencies; i.e. MnDOT, Carver and
Hennepin Counties, Department of Natural Resources, Watershed Districts, and Water
Management Organizations.
Goal Statement: Provide educational resources to improve knowledge and promote an active public
role in management of water resources.
Policy No. Goal 7: Public Education and Participation - Policies
1
The City will continue to provide opportunities for public involvement (e.g.,
neighborhood meetings, public hearings, mailed notices, etc.) for significant water
resource decisions or projects.
2
The City will coordinate and consult with the City Council and appropriate City
commissions and committees on surface water issues.
3 City will communicate with lake associations and other civic and citizen groups.
4
The City will actively implement the current educational programs and work to develop
and implement new education programs and activities related to water resources. This
program will use a variety of media including use of notices, mailings, local cable
television, newsletters, articles, internet web sites, workshops and/or presentations to
inform and educate the public.
5
The City will cooperate with other agencies and encourage establishment of model
interpretative sites for public education like the storm water practices at the Landscape
Arboretum.
6
Continue to remain in compliance with the NPDES Phase II MS4 permit with respect to
public education and involvement.
Chanhassen, MN H-4
nd
2 Generation: Surface Water Management Plan August 2006
APPENDIX I RECOMMENDED PONDS - STATUS SUMMARY
Chanhassen, MN I-1
nd
2 Generation: Surface Water Management Plan August 2006
Planning
Status 2006
Pond 1994 Level Cost
(Constructed / Watershed
Label Priority Comments / Notes Estimate
Not Management
(ID) Ranking (2006
Constructed) Class
Dollars)
BLUFF CREEK $1,355,000
BC-P1.1 Constructed Fifth Improve 1
BC-P1.2 Not Constructed Seventh Improve 1 Proposed pond is mapped as a $15,000
wetland in the 2005 wetland
boundary.
BC-P1.5A Constructed Improve 1
BC-P1.5B Constructed Improve 1 No as-built information.
BC-P1.5C Constructed Improve 1 No as-built information.
BC-P1.6 Constructed Seventh Improve 1
BC-P1.7 Constructed Improve 1
BC-P1.7A1 Constructed Improve 1 No as-built information.
BC-P1.7A2 Constructed Eighth Improve 1 No as-built information.
BC-P1.7B Constructed Improve 1 No as-built information.
BC-P1.8 Not Constructed Fifth Improve 1 Proposed pond is mapped as a $40,000
wetland in the 2005 wetland
boundary.
BC-P1.9 Constructed Seventh Improve 1
BC-P1.10A Constructed Improve 1 No as-built information.
BC-P1.10B Constructed Improve 1
BC-P1.10C Constructed Improve 1 No as-built information.
BC-P1.10D Constructed Improve 1 No as-built information.
BC-P1.11A Constructed Improve 1
BC-P1.11B Constructed Improve 1 No as-built information.
BC-P1.11C Constructed Improve 1 No as-built information.
BC-P1.11D Constructed Improve 1 No as-built information.
BC-P1.11E Constructed Improve 1
BC-P1.12 Not Constructed Seventh Improve 1 $45,000
BC-P1.13 Constructed First Improve 1
BC-P1.13A Constructed First Improve 1 No as-built information.
BC-P1.13B Constructed First Improve 1
BC-P1.13C Constructed First Improve 1 No as-built information.
BC-P1.13D Constructed First Improve 1
BC-P2.13 Not Constructed Third Improve 1 $25,000
BC-P2.3 Constructed Fourth Improve 1
BC-P2.4 Constructed Seventh Improve 1
BC-P2.4A Constructed Seventh Improve 1
BC-P2.7 Constructed Fifth Improve 1
BC-P2.9A Constructed First Improve 1
BC-P2.9B Constructed First Improve 1
BC-P3.1A Constructed Fourth Improve 1
BC-P3.1B Constructed Fourth Improve 1
BC-P3.2 Constructed Fifth Improve 1
BC-P3.4 Constructed First Improve 1
BC-P3.4A Constructed First Improve 1
BC-P4.1 Not Constructed Fifth Improve 1 Proposed pond is mapped as a $15,000
wetland in the 2005 wetland
boundary.
BC-P4.2A Constructed Improve 1 No as-built information.
Chanhassen, MN I-2
nd
2 Generation: Surface Water Management Plan August 2006
Planning
Status 2006
Pond 1994 Level Cost
(Constructed / Watershed
Label Priority Comments / Notes Estimate
Not Management
(ID) Ranking (2006
Constructed) Class
Dollars)
BC-P4.2B Constructed Improve 1 No as-built information.
BC-P4.6 Not Constructed Fourth Improve 1 $100,000
BC-P4.7A Constructed Second Improve 1
BC-P4.7B Constructed Second Improve 1
BC-P4.10 Constructed Improve 1 No as-built information.
BC-P4.10A Constructed Improve 1 No as-built information.
BC-P4.11 Not Constructed First Improve 1 Proposed pond is located within $65,000
2005 wetland boundary.
BC-P4.12 Not Constructed Third Improve 1 Proposed pond is located within $370,000
2005 wetland boundary.
BC-P5.1 Not Constructed Fifth Improve 1 $20,000
BC-P5.2 Not Constructed Fourth Improve 1 $20,000
BC-P5.3 Not Constructed Eighth Improve 1 $30,000
BC-P5.6 Not Constructed Fourth Improve 1 Proposed pond is mapped as a $65,000
wetland in the 2005 wetland
boundary.
BC-P5.8A Constructed Fourth Improve 1 No as-built information.
BC-P5.9A Constructed Improve 1
BC-P5.11 Not Constructed Third Improve 1 $75,000
BC-P5.13 Not Constructed Fifth Improve 1 Proposed pond is mapped as a $50,000
wetland in the 2005 wetland
boundary.
BC-P5.19 Constructed Second Improve 1
BC-P6.1 Not Constructed Sixth Improve 1 $65,000
BC-P6.2 Not Constructed Sixth Improve 1 $55,000
BC-P6.3 Not Constructed Sixth Improve 1 Proposed pond is mapped as a $65,000
wetland in the 2005 wetland
boundary. Not states wetland
acts as filter strip.
BC-P6.5 Not Constructed Fourth Improve 1 $40,000
BC-P6.10 Not Constructed Eighth Improve 1 $15,000
BC-P6.11 Not Constructed Eighth Improve 1 $25,000
BC-P6.12 Not Constructed Eighth Improve 1 $25,000
BC-P6.15 Not Constructed Eighth Improve 1 $10,000
BC-P6.16 Not Constructed Fifth Improve 1 $20,000
BC-P6.19 Not Constructed Third Improve 1 Proposed pond located on Bluff $25,000
Creek.
BC-P7.1 Constructed Eighth Improve 1
BC-P7.1A Constructed Eighth Improve 1 No as-built information.
BC-P7.4 Not Constructed Sixth Improve 1 $25,000
BC-P7.5 Not Constructed Third Improve 1 Proposed pond located on Bluff $25,000
Creek.
BC-P7.9 Not Constructed Third Improve 1 Proposed pond within Rice Lake $25,000
boundary and 2005 wetland
boundary.
CHRISTMAS LAKE $50,000
CL-P1.1 Not Constructed Eighth Improve 2 Proposed pond is located within $15,000
2005 wetland boundary.
CL-P1.2A Not Constructed Fifth Improve 2 Proposed pond is located within $20,000
2005 wetland boundary.
Chanhassen, MN I-3
nd
2 Generation: Surface Water Management Plan August 2006
Planning
Status 2006
Pond 1994 Level Cost
(Constructed / Watershed
Label Priority Comments / Notes Estimate
Not Management
(ID) Ranking (2006
Constructed) Class
Dollars)
CL-P2.2 Not Constructed Sixth Improve 2 $15,000
CL-P1.13 Constructed First Improve 2
LAKE ANN $70,000
LA-P1.2 Not Constructed Fourth Improve 2
LA-P1.5 Not Constructed Second Improve 2 $20,000
LA-P1.7 Not Constructed First Improve 2 $15,000
LA-P1.9 Not Constructed Eighth Improve 1 $10,000
LA-P1.13 Not Constructed First Improve 2 $25,000
LAKE HAZELTINE $215,000
LH-P1.1 Not Constructed Seventh Manage Proposed pond is located within $100,000
2005 wetland boundary.
LH-P1.1A Constructed Manage No as-built information.
LH-P1.4 Not Constructed Eighth Manage $25,000
LH-P1.5 Constructed Eighth Manage
LH-P1.6 Not Constructed Eighth Manage $65,000
LH-P1.8 Not Constructed Eighth Manage Proposed pond is located within $15,000
2005 wetland boundary.
LH-P1.9 Not Constructed Eighth Manage Proposed pond is located within $10,000
2005 wetland boundary.
LOTUS LAKE $215,000
LL-P2.1 Not Constructed Fifth Improve 1 $15,000
LL-P2.2 Not Constructed Third Improve 1 $25,000
LL-P2.4 Constructed Fourth Improve 1
LL-P2.5 Not Constructed Sixth Improve 1 Proposed pond is located within $15,000
2005 wetland boundary.
LL-P6.6 Not Constructed Third Improve 1 $15,000
LL-P6.7 Not Constructed Fourth Improve 1 $20,000
LL-P7.3 Constructed First Improve 1
LL-P7.5 Not Constructed First Improve 1 $45,000
LL-P8.1 Not Constructed Seventh Improve 1 $10,000
LL-P8.2 Not Constructed Seventh Improve 1 $20,000
LL-P9.2 Not Constructed Second Improve 1 $15,000
LL-P10.17 Not Constructed Second Improve 1 $35,000
LAKE MINNEWASHTA $610,000
LM-P1.5 Not Constructed Third Improve 2 $25,000
LM-P1.6 Not Constructed Fourth Improve 2 $20,000
LM-P1.9 Not Constructed Fifth Improve 2 $40,000
LM-P1.12 Not Constructed Second Improve 2 $25,000
LM-P3.1 Not Constructed Sixth Improve 2 Proposed pond is located within $25,000
2005 wetland boundary.
LM-P3.2 Not Constructed Fourth Improve 2 $35,000
LM-P3.8 Not Constructed Sixth Improve 2 $20,000
LM-P3.9A Constructed Improve 2
LM-P3.10 Not Constructed Sixth Improve 2 $15,000
LM-P3.13 Not Constructed Fourth Improve 2 Proposed pond is located within $15,000
2005 wetland boundary.
LM-P3.15 Not Constructed Fifth Improve 2 $15,000
Chanhassen, MN I-4
nd
2 Generation: Surface Water Management Plan August 2006
Planning
Status 2006
Pond 1994 Level Cost
(Constructed / Watershed
Label Priority Comments / Notes Estimate
Not Management
(ID) Ranking (2006
Constructed) Class
Dollars)
LM-P3.16 Not Constructed Second Improve 2 Proposed pond is located within $25,000
2005 wetland boundary.
LM-P4.2 Not Constructed First Improve 2 $25,000
LM-P4.3 Not Constructed Third Improve 2 $20,000
LM-P5.1A Constructed Improve 2 No as-built information.
LM-P5.1B Constructed Improve 2 No as-built information.
LM-P5.1C Constructed Improve 2 No as-built information.
LM-P5.2 Not Constructed First Improve 2 Proposed pond is located within $40,000
2005 wetland boundary.
LM-P5.3 Not Constructed Sixth Improve 2 $25,000
LM-P5.4 Not Constructed Seventh Improve 2 $25,000
LM-P5.5 Not Constructed Sixth Improve 2 $25,000
LM-P5.6 Not Constructed Fifth Improve 2 $15,000
LM-P5.14 Not Constructed Seventh Improve 2 $20,000
LM-P5.20 Not Constructed Second Improve 2 Proposed pond is located within $25,000
2005 wetland boundary.
LM-P5.21 Not Constructed Eighth Improve 1 $25,000
LM-P5.23A Constructed Improve 2
LM-P7.4 Constructed First Improve 2 No as-built information.
LM-P7.5 Not Constructed First Improve 2 $25,000
LM-P7.6 Constructed Second Improve 2 No as-built information.
LM-P8.1 Not Constructed Eighth Improve 1 $15,000
LM-P8.5 Constructed Fifth Improve 2
LM-P8.5A Constructed Fifth Improve 2 No as-built information.
LM-P8.6 Constructed Second Improve 2
LM-P8.8 Not Constructed Second Improve 2
LM-P8.9 Constructed First Improve 2 No as-built information
LM-P8.10 Not Constructed Third Improve 2 Proposed pond is located within $30,000
2005 wetland boundary.
LM-P8.11 Not Constructed First Improve 2 Proposed pond is located within $25,000
2005 wetland boundary.
LOWER MINNESOTA RIVER $390,000
LOM-P1.1 Not Constructed Fifth Preserve Proposed pond is located within $25,000
2005 wetland boundary.
LOM-P1.3 Not Constructed Fourth Preserve Proposed pond is located within $80,000
2005 wetland boundary.
LOM-P1.4 Not Constructed Second Preserve $25,000
LOM-P1.5 Not Constructed Eighth Preserve $15,000
LOM-P1.6 Not Constructed Seventh Preserv Proposed pond is located within $65,000
2005 wetland boundary.
LOM-P1.8 Not Constructed Fourth Preserve Proposed pond is located within $45,000
2005 wetland boundary.
LOM-P1.11 Not Constructed Fifth Preserve $20,000
LOM-P1.12 Not Constructed First Preserve $115,000
LAKE RILEY $235,000
LR-P1.6A Constructed Improve 1
LR-P1.7A Constructed Improve 1
LR-P1.7B Constructed Improve 1
LR-P1.9A Constructed Improve 1
Chanhassen, MN I-5
nd
2 Generation: Surface Water Management Plan August 2006
Planning
Status 2006
Pond 1994 Level Cost
(Constructed / Watershed
Label Priority Comments / Notes Estimate
Not Management
(ID) Ranking (2006
Constructed) Class
Dollars)
LR-P1.9B Constructed Improve 1
LR-P2.2 Not Constructed Seventh Improve 1 $25,000
LR-P2.3 Not Constructed Third Improve 1 $20,000
LR-P2.5 Not Constructed Second Improve 1 $25,000
LR-P2.6 Not Constructed Third Improve 1 Proposed pond is located within $25,000
2005 wetland boundary.
LR-P3.3 Not Constructed Sixth Improve 1 Proposed pond is located within $20,000
2005 wetland boundary.
LR-P3.6 Not Constructed Fifth Improve 1 Proposed pond is mapped as a $20,000
wetland in the 2005 wetland
boundary.
LR-P3.7 Not Constructed Seventh Improve 1 Proposed pond is located within $20,000
2005 wetland boundary.
LR-P3.8 Not Constructed Third Improve 1 Proposed pond is located within $30,000
2005 wetland boundary.
LR-P4.5 Not Constructed Fourth Improve 1 $25,000
LR-P4.6 Not Constructed Second Improve 1 $25,000
LR-P4.10 Constructed First Improve 1
LAKE SUSAN $240,000
LS-P1.1 Constructed Eighth Improve-2 No as-built information.
LS-P1.3 Not Constructed Eighth Improve-2 $20,000
LS-P2.7 Constructed Improve-2
LS-P3.1 Not Constructed Third Improve-2 $10,000
LS-P3.2 Constructed Improve-2
LS-P3.11 Constructed Third Improve-2
LS-P2.12 Not Constructed Third Improve-2 Proposed pond is mapped as a $160,000
wetland in the 2005 wetland
boundary.
LS-P3.6A Constructed Improve-2
LS-P3.7A Not Constructed Third Improve-2 $15,000
LS-P3.7B Not Constructed Fourth Improve-2 Proposed pond is mapped as a $15,000
wetland in the 2005 wetland
boundary.
LS-P3.8 Not Constructed Fifth Improve-2 $20,000
LS-P3.9 Constructed Seventh Improve-2
LS-P3.9 Constructed Improve-2
LS-P3.20 Constructed Second Improve-2 Former drainage channel is
acting as a storm water
treatment swale.
LS-P3.21A Constructed Improve-2 No as-built information.
LS-P3.21B Constructed Improve-2 No as-built information.
LS-P3.22 Constructed Improve-2 No as-built information.
LS-P3.24A Constructed Improve-2
LS-P3.31 Constructed Improve-2
LS-P3.34 Constructed First Improve-2
LS-P3.35A Constructed Improve-2
LS-P3.36 Constructed Improve-2 No as-built information.
Chanhassen, MN I-6
nd
2 Generation: Surface Water Management Plan August 2006
Planning
Status 2006
Pond 1994 Level Cost
(Constructed / Watershed
Label Priority Comments / Notes Estimate
Not Management
(ID) Ranking (2006
Constructed) Class
Dollars)
LAKE LUCY $460,000
LU-P1.10 Constructed Improve-3
LU-P1.11 Constructed First Improve-3 .
LU-P2.4A Constructed Improve-3
LU-P2.5A Constructed Improve-3
LU-P2.6 Not Constructed Eighth Improve-3 Proposed pond is located within $25,000
2005 wetland boundary.
LU-P3.4 Not Constructed Second Improve-3 Proposed pond is located within $120,000
2005 wetland boundary.
LU-P5.2 Not Constructed Third Improve-3 $35,000
LU-P5.3 Not Constructed Sixth Improve-3 $30,000
LU-P5.4 Not Constructed Eighth Improve-3 $20,000
LU-P5.8A Constructed Improve-3
LU-P5.10 Not Constructed Eighth Improve-3 $25,000
LU-P5.11 Constructed Third Improve-3 Storm water pond constructed
on private property, not labeled
in inventory.
LU-P5.12 Not Constructed Fifth Improve-3 $30,000
LU-P5.13 Not Constructed Fourth Improve-3 Proposed pond is located within $55,000
2005 wetland boundary.
LU-P5.14 Not Constructed Third Improve-3 $30,000
LU-P5.15A Constructed Improve-3
LU-P5.16 Not Constructed Third Improve-3 $50,000
LU-P6.1 Not Constructed Seventh Improve-3 $20,000
LU-P6.2 Not Constructed Eighth Improve-3 $20,000
MINNEHAHA CREEK $155,000
MC-P1.1A Constructed No as-built information.
MC-P2.6 Not Constructed First Proposed pond is located within $40,000
2005 wetland boundary.
MC-P2.9 Not Constructed Third Proposed pond is located within $35,000
2005 wetland boundary.
MC-P3.3 Not Constructed Second Proposed pond is located within $50,000
2005 wetland boundary.
MC-P3.4 Not Constructed Fifth $20,000
MC-P4.2 Not Constructed Seventh $10,000
MITCHELL LAKE $105,000
ML-P1.1 Not Constructed Eighth $20,000
ML-P1.2 Not Constructed Third $55,000
ML-P2.1 Not Constructed Eighth $10,000
ML-P2.2 Not Constructed Eighth $20,000
ML-P2.4 Constructed Sixth
PURGATORY CREEK $60,000
PC-P1.1 Constructed First
PC-P1.4 Not Constructed First $25,000
PC-P1.5 Not Constructed Fourth Proposed pond is mapped as a $20,000
wetland in the 2005 wetland
boundary.
PC-P1.6 Not Constructed Third Proposed pond is located within $15,000
2005 wetland boundary.
Chanhassen, MN I-7
nd
2 Generation: Surface Water Management Plan August 2006
Planning
Status 2006
Pond 1994 Level Cost
(Constructed / Watershed
Label Priority Comments / Notes Estimate
Not Management
(ID) Ranking (2006
Constructed) Class
Dollars)
RICE MARSH LAKE $85,000
RM-P1.3 Constructed Eighth Manage Proposed pond is located within
2005 wetland boundary, wetland
was excavated to provide
additional storm water
treatment.
RM-P1.4 Constructed Fourth Manage Proposed pond is located within
2005 wetland boundary. Part of
the wetland was excavated to
provide additional storm water
treatment.
RM-P1.4A Constructed Fourth Manage No as-built information.
RM-P1.6 Constructed Seventh Manage Proposed pond is located within
2005 wetland boundary, wetland
was excavated to provide
additional storm water
treatment.
RM-P3.1 Not Constructed Fifth Manage Proposed pond is located within $30,000
2005 wetland boundary.
RM-P3.2 Constructed Manage No as-built information.
RM-P3.2A Constructed Manage No as-built information.
RM-P3.2B Constructed Manage No as-built information.
RM-P3.3A Constructed Second Manage No as-built information.
RM-P3.3B Constructed Second Manage No as-built information.
RM-P4.8 Constructed Manage
RM-P4.9 Not Constructed Third Manage Proposed pond is located within $30,000
2005 wetland boundary.
RM-P5.3A Constructed Manage
RM-P5.6 Constructed Manage
RM-P5.7 Not Constructed First Manage $25,000
TOTAL POND SUMMARY (2006 DOLLARS)$4,245,000
Notes:
1. Planning level costs based on the data from the 1994 Plan and assuming 3.5 percent inflation over 12 years. The
numbers were then rounded to the next highest $5,000 value.
2. Cost estimates do not include land acquisition costs which can be a major additional cost in the implementation
of the pond systems.
Chanhassen, MN I-8
nd
2 Generation: Surface Water Management Plan August 2006
APPENDIX J NPDES MS4 PERMIT SWPPP (SUMMARY)
1. Storm System Maintenance and Inspection Recommendations Memorandum.
2. SWPPP Summary. Note that SWPPP as of March 2006 – Changes may occur prior to final
SWMP as a result of the revised Non-degradation assessment permit requirements.
Chanhassen, MN J-1
nd
2 Generation: Surface Water Management Plan August 2006
MEMORANDUM
TO: Lori Haak, Water Resources Coordinator
City of Chanhassen
FROM: SEH Water Resources
DATE: August30, 2006
RE: Storm System Inspections and Maintenance Considerations
SEH No. A-CHANH0409.00 Task 93001 SP
The City’s stormwater conveyance system inherently collects and conveys urban runoff and stormwater
that may contain certain pollutants to surface water resources. Like other City infrastructure, the system
requires a combination of routine maintenance and occasionally major repairs in order to function
properly. Conducting inspections and maintenance of the system is also a requirement of the City’s
NPDES permit program. The intent of this memorandum is to outline recommended inspection and
maintenance protocols the City should follow in order to comply with the obligations of the NPDES
program as a first priority. In doing so, the City will realize reductions in the pollutants entering water
resources, reduce the occurrences of localized flooding from blocked or degraded system components and
reduce the overall long-term costs associated with its storm water management infrastructure.
Protocols for maintenance are described in a number of online sources as well as in similar guidance
documents from regulatory agencies. These guidance documents are intended to reduce the volume and
resulting impacts of pollutants reaching receiving waters through proper conveyance system operation
and maintenance. Properly maintaining infrastructure such as catch basins, sump manholes, inlets,
skimmer structures, treatment systems (ponds, rain gardens, etc.) and other stormwater system
infrastructure on a regular basis will remove pollutants, reduce pollutant concentrations during the first
flush, prevent clogging of the conveyance system, restore sediment trapping capacity, and reduce
blockages in the system so that it functions properly hydraulically and reduces the occurrences of
localized flooding.
The primary BMPs in the City’s NPDES SWPPP that relate to inspections and maintenance of the storm
sewer system are listed below. Recommendations for each category are provided in the following pages
to supplement the City’s regulatory requirements.
BMP ID BMP Title
6a-1 Municipal Operations and Maintenance Program
6a-2 Street Sweeping
6b-2 Annual Inspection of All Structural Pollution Control Devices
6b-3 Annual Inspection of 20% of Outfalls, Sediment Basins and Ponds
Annual Inspection of All Exposed Stockpiles, Storage and Material
6b-4
Handling Areas
6b-5 Inspection Follow-up (Repair, Replacement, Maintenance)
Record Reporting and Retention: Inspections and Maintenance
6b-6
Program
6b-7 Evaluation of Inspection Frequency
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Suggested Considerations and Protocols - by BMP
6a-1 Municipal Operations and Maintenance Program
The City will provide training for Public Works, Parks & Recreation and Development Review Staff on a
range of topics related to the NPDES permit program. Several potential topics and specific
recommendations are provided below as a guide to developing a more formal training program. One
example of a simple training topic that can help improve water quality to train City landscape crews on
the need to limit the deposits of grass clipping into the streets, unless they are cleaned/removed after
mowing so they don’t end up in the storm drains.
In addition, some local twin cities municipalities have initiated efforts to better coordinate municipal
training programs such as the Public Works Forum in the east metro area which includes City Engineers,
Public Works Directors and Watershed Organization staff addressing topics such as those listed below.
Again, the items listed below are potential topics to present at training and are intended as a guide to help
City staff at all positions recognize the activities that may have impacts to the City’s storm water system.
1. Train crews in proper maintenance activities, including record keeping and material handling and
disposal.
2. Train staff involved in detection and removal of illicit connections in the following:
a. OSHA-required Health and Safety Training plus annual refresher training (as needed).
b. OSHA Confined Space Entry training for staff entering manholes or other confined
spaces.
3. Procedural training for field staff looking for illicit discharges or tracking origination of
discharges (field screening, sampling, smoke/dye testing, TV inspection).
4. Clean up of spills and leaks using “dry” methods (with absorbent materials and/or rags), or dig
up, remove, and properly dispose of contaminated soil.
5. Look for evidence of illegal discharges or illicit connections during routine maintenance of
conveyance system and drainage structures:
a. Is there evidence of spills such as paints, discoloring, etc?
b. Are there any odors associated with the drainage system?
c. Record locations of apparent illegal discharges/illicit connections.
d. Track flows back to potential dischargers and conduct aboveground inspections. This can
be done through visual inspection of upgradient manholes or alternate techniques
including zinc chloride smoke testing, fluorometric dye testing, physical inspections, or
TV camera inspection.
e. Eliminate the discharge once the origin of flow is established.
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6. Conduct illegal dumping training for inspecting and cleaning up hot spots and other storm
drainage areas regularly where illegal dumping and disposal occurs. Train staff that may be in the
field on non-storm water program activities to recognize, look for and report potential problems
in the context of what may impact water quality or potential plugging of the drainage system.
7. Establish a process to investigate all reports of spills, leaks, and/or illegal dumping promptly and
for tracking incident response. The system should be designed to identify the following:
a. Types and quantities (in some cases) of wastes
b. Patterns in time of occurrence (time of day/night, month, or year)
c. Mode of dumping (abandoned containers, “midnight dumping” from moving vehicles,
direct dumping of materials, accidents/spills)
d. Responsible parties
8. Clean-up activities may create a slight disturbance for local aquatic species. Access to items and
material on private property may be limited. Trade-offs may exist between channel hydraulics
and water quality/riparian habitat. If storm channels or basins are recognized as wetlands, many
activities, including maintenance, may be subject to regulation and permitting.
9. Storm drain flushing is most effective in small diameter pipes (36-inch diameter pipe or less,
depending on water supply and sediment collection capacity). Other considerations associated
with storm drain flushing may include the availability of a water source, finding a downstream
area to collect sediments, liquid/sediment disposal, and prohibition against disposal of flushed
effluent to sanitary sewer in some areas.
10. Stencil or demarcate storm drains, where applicable, to prevent illegal disposal of pollutants.
Storm drain inlets should have messages such as “Dump No Waste Drains to Stream” stenciled
next to them to warn against ignorant or intentional dumping of pollutants into the storm drainage
system.
11. Post “No Dumping” signs in problem areas with a phone number for reporting dumping and
disposal. Signs should also indicate fines and penalties for illegal dumping.
6a-2 Street Sweeping
The City currently sweeps at least once per year and has goals to sweep at least twice per year starting in
2007. The City also intends to develop a schedule and tracking system for sweeping activities. Figure J-2,
provided in this Appendix J for the inspection program, can also be used to help prioritize sweeping
activities. The approach may be to complete the first and/or second sweeping based on a prioritized basis
of which watershed areas have the highest priority waters. Traffic and safety issues are also involved,
although the priority system would help identify which areas should see a more focused sweeping effort.
As the sweeping program progresses, the City could end up with a map that shows different levels of
priority based roughly on a structure that considers factors including:
1. The highest priority watersheds.
2. The extent and frequency of sanding activities.
3. Areas which discharge directly to water bodies versus areas that are routed through storm water
ponds.
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6b-2 Annual Inspection of All Structural Pollution Control Devices
The City will inspect all structural pollution control devices annually as part of the NPDES permit
program requirements. Structures may include sump manholes, grit chambers, skimmers, mechanical
separators, small filtering devices, trash racks, etc. The following subsections provide some
recommended frequencies and maintenance actions for each type of BMP. See the general inspection
procedures at the end of this Appendix for a summary of the key things to looks for and observe during
inspections of these structures.
Sump Manholes/Grit Chambers/Separators
1. Inspect facilities at least annually in accordance with BMP 6b-2, to determine need for removal of
sediment or other maintenance. Sump manhole locations are identified in Figure J-2.
2. Cleaning should be conducted before a sump exceeds approximately the 40-60% full level. Sump
manholes should be cleaned as frequently as needed to meet this standard. The level of the
sediment/debris in the sump area should be tracked for each inspection, even if the material is not
removed. This process will help identify the need for extending or shortening the time between
inspections and to identify the preferred timing of sediment/debris removal.
3. The notebook process (or electronic method in the future) mentioned in 6b-3 should be followed
for all small pollution control devices.
4. As new structures are added, the development review staff would be responsible for adding the
new structures to the GIS database so that they are inspected later in the current year and/or part
of the annual inspections in the following year.
Catch Basins/Inlet Structures
1. Inspect facilities routinely during regular street maintenance activities to determine if there are
signs of any deterioration threatening structural integrity that are in need of immediate repair, and
if stenciling of catch basins and inlets with “drains to stream” or “drains to lake” are still visible
or in need of re-stenciling
6b-3 Annual Inspection of 20% of Outfalls, Sediment Basins and Ponds
The City will inspect 20% of the ponds and outfalls annually as part of the NPDES permit program
requirements. The following subsections provide some recommended approaches and considerations for
this inspection program. City staff will identify if the ponds and outfalls are functioning properly and
conduct necessary maintenance, repair or replacement. This memorandum includes an attached example
inspection checklist (which is similar to what the City currently uses) but that also clearly identifies the
key elements required for reporting and follow-up maintenance actions in the NPDES permit program.
The following subsections provide some considerations and suggestions for outfalls and ponds
specifically. See the general inspection procedures at the end of this Appendix for a summary of the key
things to looks for and observe during inspections of these structures.
Outfalls and Ponds/Sediment Basins
1. Inspect facilities on an annual basis according to the groupings identified in Figure J-1. Five areas
are identified in Figure J-1 that have borders based on major roads or distinct sections of the City.
The intent of the priority system listed in Figure J-1 is to establish a guide for annual inspection
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planning based on the priority of the water body or water bodies within the border. The map
represents a balance between administrative ease and watershed-based planning.
2. While the areas do not separate the outfalls and ponds into exact 20% sections of the City, the
long-term (5-year) goal is to reach each outfall and pond at least once in the five-year period. As
time permits, the intent would be to get ahead of the program by inspecting priority areas 1 and 2,
for example, in the first year.
3. Outfalls and ponds should be inspected directly (and not by a drive-by process) to observe that
the system does not have restrictions, scour at the outlet, or discolored liquid discharging into the
pond or discharging to the downstream surface water.
4. Until the City is upgraded at some point in the future to using handheld electronic web-based
devices for infrastructure inspections, the use of a 3-ring notebook with the areas in Figure J-1
separated into parts will be sufficient to plan and track the outfall and pond inspections.
5. The notebook should have a print-out of each outfall (or group of outfalls) identified on a letter
sized page that identifies the unique ID of each outlet and the major road or roads in the area. In
the same manner, each pond could have a printout with its unique ID and showing the pipes or
conveyances into and out of the pond.
6. Inspection staff would then use their current inspection form or the example in this appendix in
the field (prior to establishing a hand held device process), then enter the data into the GIS or
other tracking system database for each outfall in the office after completing the field work. The
end result would be that staff could have the ability to click on an outfall or pond from their
desktop and see what and when inspections and maintenance had been conducted on each system
component.
7. For areas needing a follow-up inspection or maintenance, the City’s lead for inspections would
review the items on a weekly or monthly basis and be responsible for scheduling follow-up
activities. Any major maintenance needs and activities should also include notification to the
Public Works and Natural Resources departments.
8. As new ponds or outfalls are added, the development review staff would be responsible for
adding the new features to the GIS database so that they are inspected later in the current year
and/or part of the annual inspections in the following year.
6b-5 Inspection Follow-up (Repair, Replacement, Maintenance)
City staff will conduct inspections of the system as identified in the previous BMP sections for water
quality purposes, but also are required to identify if the system is functioning properly and conduct
necessary maintenance, repair or replacement. This memorandum includes an attached example
inspection checklist (which is similar to what the City currently uses) but that also clearly identifies the
key elements required for reporting and follow-up maintenance actions in the NPDES permit program.
The assignment of responsible staff for follow-up activities is the critical item in this BMP section. The
tracking and reporting form current used (or the example form) will help gather a reasonable amount of
data to be tracked to support the ongoing program evaluation, and adjustment in the inspection program
over time.
The following subsections provide some considerations and suggestions for the more routine storm
system maintenance that crews will be responsible for and that are not specifically mentioned in BMPs
6b-3 and 6b-5.
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Catch Basins/Inlet Structures
1. Clean catch basins, storm drain inlets, and other conveyance structures in the late winter/early
spring to remove sediments and debris accumulated and again in late fall to remove leaves and
debris. Note areas which have regular maintenance needs due to heavy vegetation or debris
blocking a structure.
2. Keep accurate logs of the number of catch basins cleaned to better track trends in which
structures have most frequent maintenance needs.
Storm Drain Conveyance System (Pipes, FES, Culverts, etc.)
1. Locate reaches of storm drain with deposit problems and develop a flushing schedule that keeps
the pipe clear of excessive buildup.
2. Where the sediment buildup is adjacent to a sediment basin or storm water pond, flush the
material into the pond and remove it during the next scheduled pond cleanout activity for that
pond. If excessive sediment buildup has occurred at that pipe outlet, then remove the
accumulated sediment as soon as possible following flushing operations.
3. Where the sediment buildup is in a pipe segment that discharges to a wetland, lake or stream,
collect the material with a vactor truck and dispose of off-site. Note the location of the
accumulated sediment on the storm system checklist and request an evaluation of the need for a
sump manhole at that location by Engineering Department staff.
4. Inspect FES pipe inlets and outlets for signs of sediment and debris accumulation that reduce the
capacity of the system and for signs of deterioration or damage. On all FES inlets and outlets,
inspect for the presence of erosion or scour around the pipe section and immediately adjacent to
the FES. If the outlet is routed to a dry channel downstream, observe the downstream reach for
signs of erosion and scour.
Open Channels
1. Observe channel sections for occurrences of scour or bank erosion and deposits of sediment or
large debris which may reduce the conveyance capacity of the channel.
2. Consider modifications to storm channel characteristics to improve stability, channel hydraulics,
increase pollutant removals, and enhance channel/creek aesthetic and habitat value.
Pump Stations
1. Clean all storm drain pump stations at least twice per year to remove silt and trash.
2. Do not allow discharge to reach the storm drain system when cleaning a storm drain pump station
or other facility.
3. Conduct routine maintenance at each pump station including testing pump operation at least
annually.
4. Inspect, clean, and repair as necessary.
6b-6 Record Reporting and Retention: Inspections and Maint. Program
The use of a paper and/or electronic storm system inspection record process is the first step in tracking
and reporting on annual inspections described in previous BMPs. Getting the data tracked in an
electronic format will further automate the process of preparing a summary of the activities and results of
the program. As a first step the City may be best suited to track the data in an Excel or Access database
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and consider a more comprehensive work-order management system like City-Works in the future. The
City should consider how the current data would be uploaded to a more comprehensive system when
making this decision. In this light Access would allow for both more efficient tracking and likely easier
transfer of the data.
6b-7 Evaluation of Inspection Frequency
Based on the data collection and a review of trends in material removed from structures or ponds and the
frequency of maintenance of system, the City may choose to adjust the inspection frequency (either
increase or decrease). For example, if a selected sump manhole is inspected annually and determined to
be 80% full each inspection in the first two years, the City should consider increasing the frequency to
twice per year to better manage the accumulation of sediment in the structure. The more frequent
inspection may also help to identify what are the best times to maintain structures in various locations
(e.g., spring, summer, fall, winter).
In selected areas the City may also consider the effects of more frequent sweeping in areas with ponds
and small sediment control devices. Timely or more frequent sweeping may allow the City to clean sump
manholes out less frequently. As a big picture view, the overall goal is to reduce the loading of sediment
and pollutant to the City’s water resources. Inherent in this goal is the need for the City to manage its
resources in a cost-effective manner. A more functional database of the inspections and maintenance
program will allow the City to make better decisions on the cost-effectiveness of the various storm system
maintenance program.
rbl
Attachments:
1. Figure J-1. Inspection Zones: Outfall and Pond Locations
2. Figure J-2. Inspection Zones: Sump Manhole Locations
3. Storm System Inspection record (Example)
s:\ae\c\chanh\040900\maintenance program\inspections and maintenance memo - appendix j.doc
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Storm System Inspection Record
Pond/Water Body Name _____________________________ Date Inspected _____________
Inspector Name _________________________ Dept.: STREET UTIL. PARKS
(circle one)
Current Weather: ________________________ Weather Trends: NORMAL WET DRY
(circle one)
Unique ID ______________________________
Structure Type: 100% Inspected Annually (small pollution control devices)
Sump MH/CB Separator Skimmer Stockpile Environmental Manhole
Rain Garden Bioretention Area Infiltration Basin Other _________________
Structure Type: 20% Inspected Annually
Outfall (into lake/river/stream) Sediment Basin Pond
INSPECTION RESULTS:
OK NEEDS FURTHER REVIEW
[circle reason(s) below and add description]
Pipe Issues Structure Issues Sediment Deposition Possible Illicit Discharge
Trash Guard Obstruction Sediment Delta Other __________________
Description: ________________________________________________________________
FOLLOW-UP
Follow-up Maintenance Required:
MINOR MAJORDescription: _________________
______________________________________________________________________________
Follow-up Maintenance Completed:__________________________
Date(s) Completed:
Activity Description __________________________________________________________
Material removed (sediment, organics, etc.; estimated volume) ________________________
___________________________________________________________________________
Submit completed forms to __________
Entered into database by (initials) ________________________ Date: ____________________________________
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Best Management Practice – General Inspection Procedures
For Ponds, Sump Manholes, Bioretention Areas, etc.
The list below is intended as a summary of the key steps and considerations from the suggestions
provided in the detail inspection forms in the MPCA Storm Water Manual (MPCA Manual - Appendix D,
Pages 9-12).
1. Ponds:
a. Inspect the entire embankment including the emergency spillway for signs of erosion and or loss
of vegetative cover, animal burrows, larger vegetation (tree) growth near the inlets and outlets
that may cause plugging.
b. Inspect the inlet and outlet pipes for accumulation of debris and/or sediment and remove any
debris that can be easily and safely removed with equipment on hand at the time of the inspection.
c. Inspect inlet and outlet structures for signs of material damage or deterioration. For example, for
concrete, inspect for presence of exposed rebar, spalling of concrete and excessive cracking.
d. Inspect inlet and outlet structures lock/bolts and other safety devices for proper condition and
function.
e. Observe the permanent pool for any signs of visual pollution (e.g., discolored water, oil floating
on the surface, etc.)
f. Observe the condition of rip-rap or other inlet/outlet protection measures for signs of failure.
g. If a sediment delta is apparent from visual observations at one or more of the inlets, note these on
the inspection form and identify the need for a follow-up inspection. The frequency of sediment
accumulation to this stage will generally be 5-10 years of more, but may be more frequent in
areas where substantial construction or erosion has taken place.
i. The follow-up inspection should be conducted with waders or small boat to access the
sediment delta area(s). A survey rod could be used to measure the approximate water depth
in the sediment accumulation area.
ii. Follow-up sediment removal should occur when the sediment accumulation is estimated to
have taken no more than about 20% of the total pond storage volume below the normal
water level.
2. Sump Manholes and Environmental Manholes:
a. Inspect structure for signs of plugging from debris or accumulated sediment.
b. Place survey rod on top of sediment accumulation within the structure and determine the depth of
accumulated sediment. If the depth of accumulated sediment and debris is 40-60% of the sump
depth, note on the inspection form that sediment should be removed as soon as possible.
3. Bioretention and Infiltration Systems:
a. Follow the same general steps as for ponds and clean sumps that are 40-60% full, if present
upstream of the system.
b. Remove debris and litter from planted and/or mulched areas.
c. Observe if ponded water is present. If present and it has more than 48 hours since the last rainfall,
inspect for plugging of the overflow outlet and for indications that the soil or mulch layer has
plugged with fine sediments.
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APPENDIX K WETLAND ORDINANCE RECOMMENDATIONS
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Draft Wetland Ordinance Language 3-27-2006
Sec. 20-401. Findings intent; rules adopted by reference.
(a). Wetlands help maintain water quality, serve to reduce flooding and erosion, act as sources of
food and habitat for a variety of fish and wildlife, and are an integral part of the community's
natural landscape. Wetlands provide the aesthetic benefits of open space and can be used to
provide a natural separation of land uses. It is the intent of this ordinance to establish a policy of
sound stewardship through coordination of regulations that conserve, protect, enhance, and result
in the no net loss of these environmentally sensitive resources. In addition, it is the intent of the
city to promote the restoration of degraded wetlands.
(b). The intent of this ordinance is to avoid alteration and destruction of wetlands. When this is
not feasible, mitigation must be provided to recreate the function and value of the lost or altered
wetlands.
(c). This ordinance is adopted in part to implement the Wetland Conservation Act of 1991, as
amended (M.S. § 103F.612 et seq.), and the accompanying rules of the Minnesota Board of
Water and Soil Resources (Minnesota Rules Chapter 8420, as amended).
(d). This ordinance incorporates by reference the act and the rules. Terms used in this ordinance
which are defined in the act or the rules have the meanings given there.
Sec. 20-402. Purpose.
The purpose of this ordinance is to assure the general health, safety, and welfare of the residents
through preservation and conservation of wetlands and sound management of development by:
(1). Conducting an inventory and classification of all wetlands within the city and maintenance
of a comprehensive set of official city maps depicting the approximate location and extent of
wetlands.
(2). Establishment of wetland regulations that are coordinated with flood protection and water
quality programs under the Chanhassen Surface Water Management Plan.
(3). Requiring sound management practices that will protect, conserve, maintain, enhance, and
improve the present quality of wetlands within the community.
(4). Requiring measures designed to maintain and improve water quality in streams and lakes.
(5). Protecting and enhancing the scenic value of wetlands.
(6). Restricting and controlling the harmful effects of land development on wetlands.
(7). Allowing only development that is planned to be compatible with wetland protection and
enhancement.
(8). Providing standards for the alteration of wetlands when alteration is allowed.
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(9). Mitigating the impact of development adjacent to wetlands.
(10). Educating and informing the public about the numerous benefits and features of wetlands
and the impacts of urbanization.
(11). Obtaining protective easements over or acquiring fee title to wetlands as appropriate.
Sec. 20-403. Wetland Mapping and Classification
(a). Wetlands shall be subject to the requirements established herein, as well as restrictions and
requirements established by other applicable city ordinances and regulations. The wetland
protection regulations shall not be construed to allow anything otherwise prohibited in the zoning
district where the wetland area is located.
(b) The City shall maintain the official City Wetland Inventory Map, which is hereby adopted by
reference. A copy of this map shall be maintained on the City’s GIS database, with both hard
and electronic copies being made available for public review upon request.
(c). The City Wetland Inventory Map shall identify each basin as one of four management
categories: Preserve, Manage 1, Manage 2, and Manage 3. These classifications will be
determined using the attached Figure 1.1 “Wetland Management Classification Process
Flowchart for Basic Wetland Protection”.
(d). Wetlands shall be classified using the results from the Minnesota Routine Assessment
Method for Evaluating Wetland Functions (MNRAM Version 3.0), or future versions.
(e). The MNRAM 3.0 classification system shall be completed by the City as a component of the
Wetland Inventory. Applicants, however, may appeal the determination, and submit a request to
change the classification. To do so, the applicant must submit an electronic copy of the
MNRAM 3.0 for each affected basin to the WCA agent. The forms must be filled out by a
qualified wetland scientist. The WCA agent will consult with the technical evaluation panel to
determine if a change is the classification is warranted. In all cases, the burden to demonstrate
the need for a change in classification lies with the applicant.
(f). The presence or absence of a wetland on the City Wetland Inventory does not represent a
definitive determination as to whether a jurisdictional wetland that would be covered by this
ordinance is present. Wetlands identified during a site specific delineation, but not identified by
the Wetland Inventory, are still subject to the provisions of this ordinance.
(g). It is the responsibility of the applicant to determine whether a wetland exists on a subject
property. It is the responsibility of the applicant to complete a wetland delineation and submit
sufficient documentation of the wetland boundary through a Wetland Delineation Report.
Wetland delineations shall be completed by, or under the direct supervision of, a Certified
Wetland Delineator. Four hard copies of the Wetland Delineation Report must be submitted to
the City’s WCA official. Additionally, an electronic copy of the wetland delineation results must
be submitted in a format compatible with the City’s GIS database.
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(h). Wetland delineations do not need to be completed for adjacent properties, however sufficient
information must be presented to demonstrate that any proposed activities shall not inadvertently
or intentionally impact adjacent basins. The applicant shall review readily available information
including, but not limited to, the City Wetland Inventory, National Wetland Inventory maps,
topographic maps, Soil Survey maps, and recent and historic aerial photographs.
Sec. 20-404. No net loss.
To achieve no net loss of wetland, except as provided under section 20-416 of this ordinance, or
authorized by a wetland alteration permit issued by the city, a person may not drain, grade,
excavate, fill, burn, remove healthy native vegetation, or otherwise alter or destroy a wetland of
any size or type. Any alteration to a wetland permitted by a wetland alteration permit must be
fully mitigated so that there is no net loss of wetlands.
Sec. 20-405. Standards.
The following standards apply to all lands within and abutting a wetland:
(1). Septic and soil absorption system must be a setback minimum of 75 feet from the ordinary
high water mark of the wetland.
(2). The lowest ground floor elevation of a principal structure is three feet above ordinary high
water mark of the wetland.
(3). Docks and boardwalks shall be elevated a minimum of six inches above the ordinary high
water mark or six inches above the ground level, whichever is greater. Docks shall only extend
from the edge of the wetland in to the lake in instances where a wetland surrounds or abuts the
lake.
(4). Access across a wetland shall be by means of a boardwalk or elevated structure and only
upon approval of a wetland alteration permit. Wetland crossings must also be in conformance
with all other state regulations.
(5). The city's Best Management Practices Handbook shall be followed.
Sec. 20-406. Wetland buffer strips and setbacks.
(a). For lots created after June 1, 2006, a buffer strip shall be maintained abutting all wetlands.
All existing vegetation adjacent to a wetland shall be left undisturbed and applied toward the
buffer strip unless otherwise approved by city council. Buffer strip vegetation shall be
established and maintained in accordance to the following requirements. If the buffer area is
disturbed, native plant species shall be selected from wetland and upland plants to provide
habitat for various species of wildlife. Buffer strips shall be identified by permanent
monumentation acceptable to the city. In residential subdivisions, a monument is required for
each lot. In other situations, a monument is required for each 300 feet of wetland edge.
(b). Before release of final plat, the applicant must submit to the City Planner and receive
approval of a conservation easement for protection of the wetland and approved buffer strip. The
easement must describe the boundaries of the wetland and the wetland buffer strips, monuments,
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and monument locations, and prohibit any structures, paving, mowing, introduction of non-
native vegetation, cutting, filling, dumping, yard waste disposal, fertilizer, or tampering with the
monuments.
(c). The following table provides the minimum standards required for each wetland
classification. The buffer width is divided into two categories to reflect both the minimum
average width, and minimum widths allowed.
Principal and Permanent Minimum
Accessory Buffer Strip Permanent Percent Native
Wetland Type
Structure Setback Average Buffer Zone Vegetation
(feet) Width (feet) Width (feet)
Preserve 50 50 30 Entire
Manage 1 35 35 25 Entire
Manage 2 25 25 20 Majority
Manage 3 16 16 16 Majority
DNR Protected
50 50 25 Majority
Waters
(d). The WCA agent or City Council may approve buffer variations if suitable hardship can be
demonstrated. In these instances, additional performance standards may be enforced to
compensate for the reduced buffer widths.
(e). Wetland buffers for wetland mitigation areas shall conform to the minimum standards as set
forth by the Wetland Conservation Act.
(f). Additional wetland impacts shall not be allowed for the creation of buffer, even if impacts
are small and exempt from compensatory replacement.
(g). The use of meandering buffer strips to maintain a natural appearance is encouraged
(h). Where roadways are constructed next to a wetland, the average buffer strip width for the
adjacent wetland shall be maintained.
(i). Setback requirements are also designated. No structures are to be placed within the setback
distance. Additional front and side yard setback requirements must also be adhered to and must
be provided for outside of the designated wetland and buffer.
(j). Where acceptable natural vegetation exists in a wetland and adjacent buffer, the retention of
such vegetation in an undisturbed state shall be required unless the applicant receives approval to
replace such vegetation. A wetland and/or buffer has acceptable vegetation if it is dominated by
native tree, shrub, or grass species, and has not been used for agricultural production in the last
five years.
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(k). The City WCA agent may also deny the use of existing vegetation for the use of buffers if:
1.It is dominated by any species on the state noxious weed list as defined by Minnesota
Statutes, Section 18.76-18.88. These species include species such as leafy spurge,
spotted knapweed, purple loosestrife, and common and glossy buckthorn.
2.Is present on unstable slopes, has significant bare soil, displays history or erosion
problems, prone to gully formation, or inability to function for sediment and nutrient
removal.
3.Any areas were used for agricultural production in the last five years.
(l). If an area is deemed to be unacceptable in its current state, wetland buffer landscaping plan
must be submitted to the City WCA Agent. This plan shall include, at a minimum:
1.A plan sheet showing the proposed new buffer locations and any buffers acceptable as
existing. Existing buffers shall be identified and marked to prevent accidental
disturbances.
2.A specification as to what seed mixture will be used, or what trees and/or shrubs will be
planted and their locations.
3.Verification that all seed stock and tree species are native to Minnesota, and preferably be
of local ecotypes.
4.Detailed specifications that identify the project schedule, materials, and installation or
seeding instructions
5.A maintenance schedule that describes the activities that will occur for at least the first
two years. This should include a schedule of mowing and spot spraying for weeds if an
area is seeded. Plans that call for periodic burning shall have additional details and must
have special permission prior to installation.
6.Detail all BMP’s and erosion control plans.
7.Identify the locations of buffer markers.
8.Provide an electronic copy of plans in a format compatible with the City GIS database.
(m). The city may, at their discretion, require a cash escrow or letter of credit up to 150% of the
cost to reestablish the buffer should it not be successful, not be maintained, or otherwise require
city intervention to maintain the ordinance requirements.
(n). For residential developments, the locations of buffers shall be surveyed and recorded on the
Property Title and Certificate of Survey. A Certificate of Occupancy shall not be issued unless
this task is completed and approved by City Staff.
(o). For lots of record between prior to June 1, 2006 the buffer strips and setback requirements
shall meet the standards based on the wetland classification used at the time of approval.
(p). For lots of record on December 14, 1992 within wetland areas and for lands abutting a
wetland area, the following minimum provisions are applicable unless alternative plans are
approved by the city as outlined in subparagraph (a) above. The wetland classifications shall be
those used in the 1994 SWMP, as listed in the following table.
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Pristine Natural Ag/Urban Utilized
Setback Principal Structure 100' 75' 75' 0'
Sec. 20-407. Permit required.
(a). No person shall drain, excavate in the permanent of semipermanent flooded areas of type 3,
4, or 5 wetlands, or fill a wetland, wholly or partially, or otherwise impact wetlands without first
having a wetland replacement plan or other determination approved by the city. Draining,
grading, excavating, filling, removing of healthy native vegetation, or otherwise altering or
destroying a wetland of any size or type requires a wetland alteration permit. Activity in a
wetland requiring a wetland alteration permit includes, but is not limited to:
(1). Construction of new streets and utilities.
(2). Creation of ponds or dams and alterations of the natural drainageways of water courses. This
shall only be allowed as part of a mitigation project, or to restore or improve the function and
value of the wetland.
(3). Installation of boardwalks.
(4). Discharge of stormwater runoff in a manner that impacts the wetland.
(a). The city must be notified at least five business days prior to the use of any form of
treatment of wetlands including chemically treating, burning, mowing or biologically
treating wetlands to control nuisance vegetation.
(1). At the time of notification, a person or company will be required to supply the
following information:
a.. Location of pond.
b.. Area of pond to be treated.
c.. Name, address and telephone number of the party responsible for
treatment.
d.. Name, address and telephone number of person or persons performing
the treatment.
e.. Date of treatment.
f.. A list of the type of treatments to be used at such time.
g.. A statement indicating an understanding of the treatment being applied
and its effect on humans, plants and wildlife.
Sec. 20-408. Wetland alteration.
(a). An applicant for a wetland alteration permit must demonstrate that the activity impacting a
wetland has complied with all of the following principles in descending order of priority:
1.Avoids the direct or indirect impacts to the wetland that may destroy or diminish the
wetland;
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2.Minimizes the impact to the wetland by limiting the degree or magnitude of the wetland
activity and its implementation;
3.Rectifies the impact by repairing, rehabilitating, or restoring the affected wetland;
4.Reduces or eliminates the impact to the wetland over time by preservation and
maintenance operations during the life of the activity; and
5.Replaces unavoidable impacts to the wetland by restoring or, if wetland restoration
opportunities are not reasonably available, creating substitute wetland areas having equal
or greater public value as set forth in Minnesota Rules 8420.0530 to 8420.0760.
Exceptions to this part are calcareous fens, which are subject to Minnesota Rules
8420.1010 to 8420.1070.
(b). A wetland alteration permit shall not be issued unless the proposed development complies
with section 20-412, as well as the standards, intent, and purpose of this ordinance.
(c). Sequencing flexibility.
(1). Sequencing flexibility cannot be implemented unless alternatives have been
considered and unless the proposed replacement wetland is certain to provide equal or
greater functions and public values as determined based on a functional assessment
reviewed by the technical evaluation panel using a methodology approved by the
Minnesota Board of Water and Soil Resources. The project sponsor must provide the
necessary information and the local government unit must document the application of
sequencing flexibility in the replacement plan approval.
(2). Flexibility in application of the sequencing steps may be applied, subject to the
conditions in item (1), as determined by the local government unit if:
a.. The wetland to be impacted has been degraded to the point where replacement
of it would result in a certain gain in function and public value;
b.. Preservation of a wetland would result in severe degradation of the wetland's
ability to function and provide public values, for example, because of surrounding
land uses and the wetland's ability to function and provide public values cannot
reasonably be maintained through other land use controls or mechanisms;
c.. The only feasible and prudent upland site available for wetland replacement or
development has greater ecosystem function and public value than the wetland.
Although this is a rare circumstance since there will usually be several options for
siting the replacement wetland or development, it may be appropriate if the
project sponsor:
1. Demonstrates impact minimization to the wetland;
2. Agrees to perpetually preserve the designated upland site;
3. Completely replaces the impacted wetland's functions and public
values; or
4. The wetland is a site where human health and safety is a factor.
(d). When a wetland alteration permit is issued allowing filling in a wetland, filling must be
consistent with the Chanhassen Surface Water Management Plan and the Minnesota Wetland
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Conservation Act. The filling shall not alter the hydrological patterns in the remainder of the
wetland if a portion of the wetland remains unless exempted under section 20-416.
(e). When a wetland alteration permit is issued allowing grading in a wetland, the following
standards shall be followed:
(1). The grading will not have a net adverse effect on the ecological and hydrological
characteristics of the wetland.
(2). It shall be located as to minimize the impact on vegetation.
(3). It shall not adversely change water flow.
(4). The size of the graded area shall be limited to the minimum required for the proposed
action.
(5). The disposal of any excess graded material is prohibited within the wetland area.
(6). The disposal of any excess graded material shall include proper erosion control and
nutrient retention measures.
(7). Grading in any wetland area is prohibited during waterfowl breeding season or fish
spawning season, unless it is determined by the city that the wetland is not used for
waterfowl breeding or fish spawning.
(8). Grading in wetland areas will be required to be mitigated in accordance with the
requirements of this ordinance if the activity results in a loss of function and value of the
wetland.
Sec. 20-409. Filling.
When a wetland alteration permit is issued allowing filling in a wetland, filling must be
consistent with the Chanhassen Surface Water Management Plan and the Minnesota Wetland
Conservation Act. The filling shall not alter the hydrological patterns in the remainder of the
wetland if a portion of the wetland remains unless exempted under section 20-416.
Sec. 20-410. Grading.
When a wetland alteration permit is issued allowing grading in a wetland, the following
standards shall be followed:
(1) The grading will not have a net adverse effect on the ecological and hydrological
characteristics of the wetland.
(2) It shall be located as to minimize the impact on vegetation.
(3) It shall not adversely change water flow.
(4) The size of the graded area shall be limited to the minimum required for the proposed
action.
(5) The disposal of any excess graded material is prohibited within the wetland area.
(6) The disposal of any excess graded material shall include proper erosion control and
nutrient retention measures.
(7) Grading in any wetland area is prohibited during waterfowl breeding season or fish
spawning season, unless it is determined by the city that the wetland is not used for
waterfowl breeding or fish spawning.
(8) Grading in wetland areas will be required to be mitigated in accordance with the
requirements of this ordinance if the activity results in a loss of function and value of the
wetland.
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Sec. 20-411. Permit Application Requirements and Decisions
(a). Any subdivisions requesting approval to work in and around wetlands and subject to this
ordinance will be required to submit the following:
(1). A grading plan of the entire property
(2). Existing and proposed drainage areas to wetlands
(3). Wetland delineation report
(4). Electronic version of MnRAM 3.0 for each wetland on property
(5). Buffer landscape plan meeting the criteria of 20-406(i)
(6). Submittals required by the Wetland Conservation Act
(b). Ordinance compliance can be approved by staff, however, a wetland replacement plan can
only be approved by the City Council.
(c). Decisions made under this ordinance may be appeals to the Board of Water and Soil
Resources. Staff costs to the city associated with appeals shall be borne by the applicant.
(a). The applicant for a wetland alteration permit shall furnish the information required by the
city including, but not limited to, a site plan, topographic data, hydrological data, habitat
evaluation procedures for the review of a wetland alteration permit application, and any other
information required by Minnesota Rules 8420.0530. The community development director shall
use discretion regarding the level and complexity of information required to review the request.
A wetland alteration permit shall not be issued without having been first reviewed by the
planning commission and approved by the city council following the review and hearing
procedures set forth for conditional use permits and the additional requirement of Minnesota
Rules 8420.0230. The applicant shall have the burden of proving that the proposed use or
activity complies with the purposes, intent, and other provisions of this ordinance. The council
may establish reasonable conditions which are specifically set forth in the permit to ensure
compliance with requirements contained in this ordinance. Such conditions may, among other
matters, limit the size, kind, or character of the proposed work; require the construction of other
structures; require replacement of vegetation and wetland function and value; establish required
monitoring procedures and maintenance activity; stage the work over time; require the alteration
of the site design to ensure buffering; require the provision of a performance security.
(d). The city council shall appoint a person to serve on a technical evaluation panel. The person
must be a technical professional with expertise in water resources management. Decisions under
this ordinance must not be made until after receiving the determination of the technical
evaluation panel regarding wetland public values, location, size, and/or type if the city council,
the landowner, or a member of the technical evaluation panel asks for such determinations. This
requirement does not apply to wetlands f or which such data is included in an approved
comprehensive wetland management plan per Minnesota Rules 8420.0240. The city council may
seek and consider recommendations, if any, made by the technical evaluation panel in making
replacement plan decisions.
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(e). Decisions made under this ordinance may be appealed to the board of water and soil
resources under Minnesota Rules 8420.0250, after administration appeal rights under the official
controls have been exhausted.
(f). The applicant for a wetland alteration permit is responsible for obtaining all other necessary
permits including but not limited to those required by watershed districts, Minnesota Department
of Natural Resources, Army Corps of Engineers, and Minnesota Pollution Control Agency prior
to the permitted work been commenced.
Sec. 20-412. Mitigation.
(a). Mitigation intent . Where wetland alteration is approved and mitigation is required pursuant
to City Code and Minnesota Rules 8420.0540, mitigation must result in an improvement to the
wetland function and value. Mitigation plans must address water quality, improvement, and
maintenance of preexisting hydrological balance and wildlife habitat. The wetland function and
value will include improvement of water quality, maintaining hydrological balance, and
provision of wildlife habitat. Mitigation will be performed at ratios required by Minnesota Rules
8420.0546 to achieve replacement of the wetland function and value.
(b). Mitigation standards . Mitigation of wetlands for function and value should be restored,
created, and enhanced. The mitigation standards found in Minnesota Rules 8420.0550 shall be
followed.
(c). Mitigation techniques .
(1). Mitigation will be performed at a ratio required by state law.
(2). Replacement wetlands must replace the wetland function and value that are lost from
a wetland that is drained or filled. The wetland function and value will include, but is not
limited to, improvement of water quality, floodwater and stormwater retention, public
recreation and education, commercial uses, fish, wildlife and native plant habitat, and low
flow augmentation.
(3). Mitigation shall provide a buffer strip as set forth in this ordinance.
(4). Mitigation shall maintain or enhance the wetland function and values through the
following in ratios set forth in Minnesota Rules 8420.0541:
a.. Restoration of completely or partially deteriorated wetlands.
b.. Creation of new wetlands.
c.. Upland buffer areas.
d.. Restoration of wetland vegetation.
e.. Water quality treatment areas.
(5). Mitigation, through the buffer strip, shall provide landscaping for nesting and food
for wildlife habitat. The buffer strip landscape shall provide for wildlife cover and utilize
a diversity of native flora (i.e., trees, shrubs, grasses, herbaceous plants) to encourage
wildlife diversity and provide visual variety.
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(6). Wetland mitigation should be undertaken on-site. If this is not feasible, mitigation
should occur locally within the subwatershed. If this is not possible, mitigation should
occur outside the subwatershed, elsewhere in the city. If mitigation cannot be
accomplished on site, or if the city deems it necessary to perform mitigation off-site, the
applicant shall be responsible for purchasing wetland credits from the state wetland bank.
(d). Construction management and long term wetland maintenance.
(1). The permit holder shall follow the city's best management practices to minimize
direct impacts due to erosion and construction practices and to safeguard wildlife habitat.
(2). The applicant shall submit an annual report to the city for replacement wetlands in
Chanhassen. The purpose of the annual report is to describe actual wetland restoration or
creation activities completed during the past year as well as activities planned for the
upcoming year. The annual report shall include all the information required of annual
monitoring reports by Minnesota Rules 8420.0620 subpart 2.
The applicant shall submit annual monitoring reports as required by Minnesota Rules
8420.0610. Submission shall continue for at least five years or until the replacement
wetland is deemed by the TEP to be fully functional. Where feasible, the city shall
require the permit holder to satisfy long term management requirements.
(e). Mitigation Surety. To ensure that the proposed wetland replacement occurs, the city shall
hold either a cash escrow or letter of credit equal to 150% of the current value of wetland credits
on the open market. An additional escrow account shall be established to ensure that the
required monitoring occurs. The monitoring escrow shall be set at the current average
monitoring expense as performed by an independent consultant. The minimum monitoring
escrow shall be $10,000, and may be released incrementally as monitoring is successfully
completed. The remaining escrow amount will be returned and the letter of credit terminated
upon completion of the monitoring and approval by the Technical Evaluation Panel. Any
interest earned by holding of a cash escrow shall be the property of the City.
Sec. 20-413. Exemptions.
Activities exempted by Minnesota Rules 8420.0122 shall be exempted from the provisions of
this ordinance. However, certificates of exemption must be obtained from the city prior to
starting work.
A person conducting an activity in a wetland under an exemption in part 8420.0122 shall ensure
that:
(a). Appropriate erosion control measures are taken to prevent sedimentation of the
water;
(b). The activity does not block fish activity in a watercourse; and
(c). The activity is conducted in compliance with all other applicable federal, state, and
local requirements, including best management practices as listed in part 8420.0112, and
water resource protection requirements established under M.S. ch. 103H.
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Sec. 20-414. Variances.
Variances from the requirements of this ordinance may be granted in accordance with the
variance provisions of this chapter as regulated by article II, division 3 of this chapter so long as
the variances do not violate the Wetland Conservation Act and rules adopted under the act.
Sec. 20-415. Expiration and renewal of permit.
(a). Unless otherwise specified by the city council, the person issued a wetland alteration permit
shall begin and complete the development authorized by the permit within one year after the date
the council approves the permit application.
(b). The permittee shall provide written notice to the city 24 hours prior to the commencement
and completion of the development project. No project shall be deemed to have been completed
until approved by the city after receipt of notice of completion.
(c). If the permittee fails to commence work within the time specified in this section, the permit
shall be void. The permittee may make a written application to the council for an extension of the
time to commence work, but only if the permittee submits the application prior to the date
already established to commence work. The application of an extension shall state the reasons
the permittee requires an extension. If the council does not extend the permit, the holder of the
void permit may apply for a new perm it.
Sec. 20-416. Inspection of work.
The city may cause inspection of work for which a wetland alteration permit is issued, at the
applicant's expense, to be made periodically during the course of such work and shall cause final
inspection to be made following the completion of the work.
Sec. 20-417. Enforcement procedures.
(a). Violation of article VI, wetland protection, or of the terns of a permits issued thereunder
shall be a misdemeanor.
(b). Any person who alters a wetland in violation of article VI shall apply for a wetland alteration
permit and shall pay a filing fee double the regular fee. The city council may require the violator
to restore the wetland or take other mitigative measures.
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APPENDIX L SUMMARY OF MNRAM 3.0 OUTPUT
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