K-1. Amendment of Stormwater OrdinanceRecreation Center
1.
Any land development activity that may ultimately result in the
MEMORANDUM
CYOF
TO: Kate Aanenson, Community Development Director
CUMMSSENFROM:
Terry Jeffery, Water Resources Coordinator
7700 Market Boulevard
PO Box 147
DATE: Aril 19 2016
p
Chanhassen, MN 55317
may not be constructed concurrently.
Planning &
RE: Surface Water Management Code Update
Administration
Natural Resources
Phone: 952.227.1100
Fax: 952.227.1110
Attached to this memorandum is the first reading of the updated Surface Water
Phone: 952.227.1130
Management section of City code. This revision will be consistent with the
Building Inspections
requirements of the National Pollution Discharge Elimination System permits.
Phone: 952.227.1180
General Permit.
Fax: 952.227.1190
This has been written to be consistent with the current rules of the Minnehaha Creek
Engineering
Watershed District and the Carver County Watershed Management Organization. It
Phone: 952.227.1160
is largely consistent with the Riley Purgatory Bluff Creek Watershed District
Fax: 952.227.1170
(RPBCWD) rules excepting that the minimum threshold for triggering the stormwater
impervious surface.
management requirements is less under the RPBCWD than the proposed code
Finance
changes. It is consistent with the RPBCWD erosion prevention and sediment control
Phone 952.227.1140
rule. This will be part of our Surface Water Management Plan Update.
Fax: 952.227.1110
Senior Center
Park & Recreation
The most significant change is the inclusion of a volume reduction standard.
Phone: 952.2271120
Applicants meeting the following thresholds will need to prepare a stormwater
Fax: 952.227.1110
management plan and receive a permit from the city:
Recreation Center
1.
Any land development activity that may ultimately result in the
2310 Coulter Boulevard
disturbance of one (1) or more acres of land. This shall include smaller
Phone: 952.227.1400
individual sites that are part of a larger common plan of development that
Fax: 952.227.1404
may not be constructed concurrently.
Planning &
2•
Any land development activity that will result in the disturbance of one -
Natural Resources
half acre or greater and discharges to an impaired or special water as
Phone: 952.227.1130
described in Appendix A of the NPDES/SDS Construction Stormwater
Fax: 952.227.1110
General Permit.
3.
A subdivision plat resulting in 4 or more new lots of record.
Public Works
4.
Any linear project resulting in 10,000 square feet or more of new
7901 Park Place
Phone: 952.227.1300
impervious surface.
Fax: 952.227.1310
5.
Any nonlinear redevelopment project that is immediately tributary to an
impaired water that create 10,000 square feet or more of new and/or fully
Senior Center
reconstructed impervious surfaces.
Phone: 952.227.1125
6.
Any land development activity, regardless of size, that the city determines
Fax: 952.227.1110
has a high probability to cause an adverse impact to an environmentally
Website
sensitive area or other property.
www.ci.chanhassen.nnn.us
Chanhassen is a Community for Life - Providing forTodayand Planning for Tomorrow
Kate Aanenson
Surface Water Code Update
April 19, 2016
Page 2 of 2
The following are the volume reduction performance goals per development type.
New development
a. New development that creates more than one-half acre of impervious surface will
be required to capture and retain 1.1 inches of runoff from all impervious
surfaces on the site.
b. If the new development drains to an impaired water, then the impervious
threshold is reduced to 10,000 square feet.
2. Redevelopment
a. Redevelopment projects that create one-half acre or more of new and/or fully
reconstructed impervious surfaces shall capture and retain on site 1.1 inches of
runoff from the new and/or fully reconstructed impervious surfaces.
b. Redevelopment projects that are immediately tributary to an impaired water that
create 10,000 square feet or more of new and/or fully reconstructed impervious
surfaces shall capture and retain on site 1.1 inches of runoff from the new and/or
fully reconstructed impervious surfaces.
c. Redevelopment sites that reduce their total impervious surface by 20% or more
and provide a soil management plan for the newly created green space shall be
exempt from the volume control requirement.
The new code defines site limitations that may restrict or preclude the use of infiltration
techniques. Further the code provides flexible treatment options for sites with limitations. This
flexibility reduces the abstraction amount while maintaining water quality standards.
The erosion prevention and sediment control portion of the code remains basically unchanged
except that top soil standards have been added including the requirement for a topsoil
management plan. This is consistent with Carver County and Waconia. Chaska is also in the
process of adding topsoil requirements as is Victoria.
Authorization, Findings, Purpose, Scope and Interpretation
a. Statutory authorization
L This ordinance is adopted pursuant to the authorization and policies contained
in Minnesota Statutes Chapters 1036 and 42; Minnesota Rules, Parts
6120.2500-6120.3900; and Minnesota Rules Chapters 8410 and 8420.
ii. This ordinance is intended to meet the current construction site erosion and
sediment control and post -construction stormwater management regulatory
requirements for construction activity and small construction activity (NPDES
Permit) as defined in 40 CFR pt 122.26(b)(14)(x) and (b)(15) respectively.
b. Findings
Chanhassen finds that uncontrolled stormwater runoff and construction site erosion
from land development and land disturbing activity can have adverse impacts upon local
and regional water resources diminishing the quality of public health, safety, public and
private property and natural resources of the community. Specifically, uncontrolled soil
erosion and stormwater runoff can:
L Threaten public health, safety, property and general welfare by increasing
volumes and peak flood flows and overburdening storm sewers, drainage ways
and other storm conveyances.
ii. Diminish the capacity of lakes and streams to support fish, aquatic life,
recreational and other uses by increasing pollutant loads.
iii. Degrade physical stream habitat by increasing stream bank erosion, increasing
stream bed scour and substrate embeddedness, diminishing groundwater
recharge, diminishing stream base flows and increasing stream temperatures.
iv. Undermine floodplain management efforts by increasing the incidence and
levels of flooding.
v. Alter wetland communities by changing wetland hydrology and increasing
pollutant loads.
vi. Impact groundwater by reducing recharge and increasing the potential for
pollutant loading of groundwater resources.
c. Purpose
The purpose of this ordinance is to establish minimum stormwater management
requirements and controls to minimize the threat to the general health, safety, welfare,
public and private property and natural resources of the community from construction
site erosion and post -construction stormwater runoff. This purpose shall be met
through the following objectives:
L Protect life and property from flooding.
ii. Protect private and public property as well as natural resources from the
deleterious effects of stormwater runoff and erosion.
iii. Provide a single, consistent set of performance goals applicable to all land
development.
Page I 1
iv. Ensure that annual stormwater runoff rates and volumes from post
development site conditions mimic and/or reduce the annual runoff rates and
volumes from predevelopment site conditions.
v. Assist in meeting the National Pollution Discharge Elimination System/State
Disposal System (NPDES/SDS) Municipal Separate Storm Sewer System (MS4)
and Construction Stormwater General Permit requirements.
vi. Ensure that efforts are taken to maximize pervious areas and minimize runoff by
employing better site design practices.
vii. Protect water quality form pollutant loading.
viii. Promote infiltration and groundwater recharge.
ix. Protect functional values of all types of natural waterbodies.
d. Greater Restrictions
I. Relationship to other agency Requirements—All stormwater management and
erosion prevention and sediment control activities shall comply with all
applicable requirements of the surface water management agency with legally
recognized jurisdiction in the area in which the project is located. In the case of
provisions in this ordinance and requirements of the watershed districts or
watershed management organizations that overlap or conflict and no
memorandum of understanding exists addressing the provision, the strictest
provision shall apply to the activities.
ii. Relationship to existing Easements, Covenants and Deed Restrictions—The
provisions of this ordinance are not intended to repeal, abrogate or impair any
existing easements, covenants or deed restrictions. However, where this is
ordinance imposes greater restrictions the provisions of this ordinance shall
prevail.
e. Severability
The provisions of this ordinance are severable, and if any provision of this ordinance, or
application of any such provision of this ordinance to any circumstance, is held invalid,
the application of such provision to other circumstances, and the remainder of this
ordinance must not be affected thereby.
II. Applicability
a. Stormwater management
A stormwater management plan, approved by the city, shall be required prior to any
proposed land development that meets any of the criteria in i. through v. below, unless
otherwise exempted in this ordinance in section III.
L Any land development activity that may ultimately result in the disturbance of
one (1) or more acres of land. This shall include smaller individual sites that are
part of a larger common plan of development that may not be constructed
concurrently.
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ii. Any land development activity that will result in the disturbance of one-half acre
or greater and discharges to an impaired or special water as described in
Appendix A of the NPDES/SDS Construction Stormwater General Permit.
iii. A subdivision plat resulting in 4 or more new lots of record.
iv. Any linear project resulting in 10,000 square feet or more of new impervious
surface.
v. A nonlinear redevelopment project that is immediately tributary to an impaired
water that create 10,000 square feet or more of new and/or fully reconstructed
impervious surfaces
vi. Any land development activity, regardless of size, that the city determines has a
high probability to cause an adverse impact to an environmentally sensitive area
or other property.
b. Erosion prevention and sediment control permit/plan.
An Erosion Prevention and Sediment Control (ESC) Permit, including an Erosion and
Sediment Control Plan shall be required prior to any activity that meets any of the
criteria i. through iv. below, unless otherwise exempted from this ordinance in section 3.
i. Disturbs a total land surface area of at least 2,000 square feet but less than one
acre.
ii. Involves excavating, filling, stockpiling or any combination of the three activities
in excess of 50 cubic yards.
iii. Whenever a building permit is issued.
iv. Involves the laying, repairing, replacing or enlarging of an underground utility,
pipe or other facility, or the disturbance of road ditch, grass swale or other open
channel for a distance of 300 feet or more in total.
v. Any land development activity, regardless of size, that the city determines has a
high probability to cause an adverse impact to an environmentally sensitive area
or other property. For example, within the Bluff Creek Overlay District Primary
Zone or adjacent to Seminary Fen.
c. Surface Water Pollution Prevention Plan
A surface Water Pollution Prevention Plan (SWPPP) containing all elements required by
the SDS/NPDES General Construction Permit, shall be required for any land
development activity that may ultimately result in the disturbance of one (1) or more
acres of land. This shall include smaller individual sites that are part of a larger common
plan of development that may not be constructed concurrently
III. Exemptions
The following may be exempt from the requirements of this ordinance:
a. Emergency repairs necessary to protect life, limb or property.
b. Road refurbishment such as mill and overlay that does not result in increases in
hardcover in excess of the aforementioned thresholds.
Page 13
c. Routine agricultural practices such as tilling, planting, harvesting and other associated
activities. Other agricultural practices such as the construction of structures are not
exempt.
d. Silvicultural activities.
IV. Permit Review Process
a. Pre -application meeting
The applicant shall meet with the city staff and, if necessary, staff of other agencies (eg.
WD, SWCD, etc) that may be applicable to the proposed activity. This meeting should
be used to clarify the project goals and parameters and to convey how this ordinance
applies to the proposed project.
b. Application completeness review
The City shall make a determination within ten (10) working days of the date received as
to the completeness of the application and notify the applicant in writing if the
application is not complete including the reasons for the determination.
c. Permit Authorization
If the application is found to meet the requirements of this ordinance the city may issue
approval authorizing the project or activity. This authorization shall be valid for one
year and shall be in written form from the City to the applicant.
d. Permit Denial
If the city finds that the application does not meet the requirements of this ordinance
the application must be denied. If the application is denied, the applicant will be
notified of the denial in writing including the reasons for the denial. Once denied, a new
application must be resubmitted for approval before any activity can begin.
e. Plan information requirements
The minimum information requirements of the application shall be consistent with the
erosion prevention and sediment control requirements in the most recent version of the
NPDES/SDS Construction Stormwater General Permit and shall include a fully completed
Application Checklist. The application submittal must also include permanent treatment
information showing the proposed project meets the stormwater management
requirements.
f. Modification of permitted plans
The applicant must amend an approved ESC Plan or SWPPP to include additional
requirements whenever:
L There is a change in design, construction, operation, maintenance, weather or
seasonal conditions that has the potential for to have a significant effect on the
discharge of pollutants to surface water or underground water.
ii. Inspections or investigations by site operators, local, state or federal officials
indicate the plans are not effective in eliminating or significantly minimizing the
discharge of pollutants to surface water or underground water or that the
discharges are causing water quality standard exceedances.
iii. The plan is not achieving the general objectives of minimizing pollutants in
stormwater discharges associated with construction activity.
g. Permit Completion
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Before work under the permit is deemed complete, the permittee must submit as -built
surveys in both hardcopy and georeferenced electronic form, a long term maintenance
plan and information demonstrating that the stormwater facilities conform to design
specifications.
V. Site Design and Compliance Calculations
a. Site design process
I. Better Site Design
To the maximum extent practicable, new development projects shall be
designed using the Better Site Design Techniques of the current version of the
Minnesota Stormwater Manual available on-line through the Minnesota
Pollution Control Agency. Better Site Design involves techniques applied early in
the design process to preserve natural areas, reduce impervious cover,
distribute runoff and use pervious areas to more effectively treat stormwater
runoff. Site design should address open space protection, impervious cover
minimization, runoff distribution and minimization, and runoff utilization
through considerations such as:
1. Open space protection and restoration
2. Reduction of impervious surface
3. Conformance with existing topography
4. Soil amendments
5. Distribution and minimization of runoff
a. Utilize vegetated areas, such as visual buffers, parking lot
islands, building landscaping, etc., for stormwater treatment
b. Direct impervious surface runoff to vegetated areas rather than
directly to storm sewer conveyances
c. Encourage infiltration and soils storage through grass channels,
vegetated swales, biofiltration features and soil compost
amendments, etc.
d. Plant native drought resistant vegetation that does not require
irrigation beyond rainfall and runoff from the site
6. Runoff utilization for irrigation
ii. Stormwater criteria
Storm distributions and storm volumes for hydrologic analysis, the design of
major facilities and minor drainage systems shall be based upon NOAA Atlas 14:
Precipitation -Frequency Atlas of the United States; Volume 8 Version 2.0:
Midwestern States or the most recent reference data from the National
Weather Service. The following general criteria shall be incorporated in the site
design for stormwater runoff:
1. Decrease runoff volume
2. Decrease erosion and sedimentation
3. Decrease flow frequency, duration and peak runoff rates
4. Increase infiltration
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5. Maintain existing flow patterns
6. Store stormwater runoff on-site
iii. Erosion prevention and sediment control criteria
The following general criteria shall be incorporated in site design for erosion
prevention and sediment control:
1. Minimize disturbance of natural soil cover and vegetation
2. Minimize, in area and duration, exposed soil and unstable soil
conditions
3. Protect receiving water bodies, wetlands, storm sewer inlets and
adjacent properties from sediment deposition
4. Minimize work in and adjacent to waterbodies and wetlands
5. Avoid steep slopes and the need for high cuts and fills
6. Minimize the compaction of site soils
b. Design Calculations
Storm distributions and storm volumes for hydrologic analysis, the design of major
facilities and minor drainage systems shall be based upon National Oceanic and
Atmospheric Administration (NOAH) Atlas 14: Precipitation -Frequency Atlas of the
United States; Volume 8 Version 2.0: Midwestern States or the most recent reference
data from the National Weather Service
i. Final site design and choice of permanent stormwater volume reduction
practices shall be based on outcomes of the MIDS Calculator, P8 or other model
that shows the performance goal can be met and shall meet the performance
goals in section VI of this ordinance.
ii. 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, nested, 24-hour
duration rainfall distribution with average soil moisture conditions (AMC -2). The
analysis of flood levels, storage volumes and discharge rates for detention
basins shall utilize the design storm/freeboard evaluation storm concept.
iii. 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.
1. 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
2. Landlocked stormwater 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).
Page 16
VI. Stormwater Volume Reduction Performance Goals
Any applicant for a permit that creates or fully reconstructs 10,000 or more square feet of
impervious surface and is immediately tributary to an impaired water or creates one or
more acres of new impervious surface or fully reconstructs one or more acre of impervious
surface in all other drainage areas must meet all of the following stormwater performance
goals:
a. New development volume control
i. For new, nonlinear developments that create more than one acre of new
impervious surface on sites without restrictions and are not immediately
tributary to an impaired water, stormwater runoff volumes will be controlled
and the post -construction runoff volume shall be retained on site for 1.1 inches
of runoff from all impervious surfaces on the site.
ii. For new, nonlinear developments immediately tributary to an impaired water
that create 10,000 square feet or more of new impervious surface on sites
without restrictions, stormwater runoff volumes will be controlled and the
postconstruction runoff volume shall be retained on site for 1.1 inches of runoff
from all impervious surfaces on the site.
b. Redevelopment volume control
i. Nonlinear redevelopment projects on sites without restrictions and are not
immediately tributary to an impaired water that create one or more acres of
new and/or fully reconstructed impervious surfaces shall capture and retain on
site 1.1 inches of runoff from the new and/or fully reconstructed impervious
surfaces.
ii. Nonlinear redevelopment projects on sites without restrictions that are
immediately tributary to an impaired water that create 10,000 square feet or
more of new and/or fully reconstructed impervious surfaces shall capture and
retain on site 1.1 inches of runoff from the new and/or fully reconstructed
impervious surfaces
iii. Redevelopment sites that reduce their total impervious surface by 20% or more
and provide a soil management plan for the newly created green space shall be
exempt from the volume control requirement.
c. Linear development volume control
Linear projects on sites without restrictions that create one acre or greater of new
and/or fully reconstructed impervious surfaces, shall capture and retain the larger of the
following:
L 0.55 inches of runoff from the new and fully reconstructed impervious surfaces
on the site
ii. 1.1 inches of runoff from the net increase in impervious area on the site
Mill and overlay and other resurfacing activities are not considered fully reconstructed.
d. Flexible treatment options for sites with restrictions
Page 17
Applicant shall comply with the appropriate performance goals described above.
Options considered and presented shall examine the merits of relocating project
elements to address, varying soil conditions and other constraints across the site. If full
compliance is not possible due to any of the factors listed below, the applicant must
document the reason. If site constraints or restrictions limit the full treatment goal, the
following flexible treatment options shall be used:
Applicant shall document the flexible treatment options sequence starting with
Alternative #1. If Alternative #1 cannot be met, then Alternative #2 shall be analyzed.
Applicants must document the specific reasons why Alternative #1 cannot be met based
on the factors listed below. If Alternative #2 cannot be met then Alternative #3 shall be
met. Applicants must document the specific reasons why Alternative #2 cannot be met
based on the factors listed below. When all of the conditions are fulfilled within an
alternative, this sequence is completed.
Volume reduction techniques considered shall include infiltration, reuse & rainwater
harvesting, and canopy interception & evapotranspiration and/or additional techniques
included in the MIDS calculator and the Minnesota Stormwater Manual.
Higher priority shall be given to BMPs that include volume reduction. Secondary
preference is to employ filtration techniques, followed by rate control BMPs.
In addition to the limitations listed in the NPDES/SDS Construction Stormwater General
Permit, zoning and other land use requirements as well as excessive cost may be
considered when evaluating site restrictions.
i. Alternative #1: Applicant attempts to comply with the following conditions:
1. Achieve at least 0.55" volume reduction from all impervious surfaces if
the site is new development or from the new and/or fully reconstructed
impervious surfaces for a redevelopment site
2. Remove 75% of the annual TP load and 90% of annual TSS load from all
impervious surfaces if the site is new development or from the new
and/or fully reconstructed impervious surfaces for a redevelopment
site.
3. Options considered and presented shall examine the merits of
relocating project elements to address, varying soil conditions and other
constraints across the site.
ii. Alternative #2: Applicant attempts to comply with the following conditions:
1. Achieve volume reduction to the maximum extent practicable.
2. Remove 60% of the annual TP load and 90% of the annual TSS load from
all impervious surfaces if the site is new development or from the new
and/or fully reconstructed impervious surfaces for a redevelopment
site.
Page 18
3. Options considered and presented shall examine the merits of
relocating project elements to address, varying soil conditions and other
constraints across the site.
iii. Alternative #3: Off-site Treatment. Mitigation equivalent to the performance of
1.1 inches of volume reduction for new development or redevelopment as
described above in this section, can be performed off-site to protect the
receiving water body provided it is within the watershed of the same receiving
water. Off-site treatment shall be achieved in areas selected in the following
order of preference:
1. Location that is within the same Department of Natural Resources
(DNR) Hydrologic Unit 09.
2. Location that is within the adjoining Hydrologic Unit 09 that drains to
the same DNR Catchment Area Hydrologic Unit 08.
3. Location that is within the same Hydrologic Unit 08
e. Limitations to infiltration
Infiltration techniques shall not be employed when any of the following
conditions are present.
1. An industrial facility which is not authorized to infiltrate industrial
stormwater under an NPDES/SDS Industrial Stormwater Permit.
2. Where vehicle fueling and maintenance occur.
3. When there is less than three (3) feet of separation between the
bottom of the infiltration feature and the elevation of the seasonally
saturated soils or the top of bedrock.
4. Where there is a high probability that high levels of contaminants in soil
or groundwater will be mobilized by infiltrating stormwater.
ii. Infiltration techniques may not be appropriate when any of the following
conditions are present.
1. The area is dominated by the presence of Hydrologic Group D soils.
2. When the area is within a Drinking Water Supply Management Area and
it can be shown that the infiltrated waters have a high probability of
reaching the pertinent aquifer.
3. Soils have an infiltration rate in excess of 8.3 inches per hour.
4. The area is within 1,000 feet upgradient, or 100 feet downgradient of
active karst features.
iii. Infiltration rate measurement may be requested by the City at any location or
reasonable elevation on the site through the use of an infiltrometer,
permeameter or other methodology as may be approved by the City Engineer to
verify modeling, design or other site assumptions.
iv. Shallow monitoring wells, piezometers or other investigative techniques may by
requested by the City to determine seasonally saturated soils.
VII. Stormwater Management Rate Control
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No increase in peak discharge rate may result from the proposed project for the 1- or 2 -year
storm, the 10 -year storm and the 100 -year storm event for all points where stormwater
discharges from the site. 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:
1. 2 -Year= 2.87 inches
2. 10 -Year = 4.27 inches
3. 100 -Year = 7.38 inches
VIII. Other Design Standards
Additional stormwater management facility design standards can be found in the current
version of the Chanhassen Standard Specifications and Detail Plates as well as appended to
the current Surface Water Management Plan.
a. Minnesota Stormwater Manual
All stormwater BMPs and site design specifications shall conform to the current version
of the Minnesota Stormwater Manual unless otherwise addressed in the Chanhassen
Standard Specification and Detail Plates.
b. Site Erosion and sediment control requirements
All erosion prevention and sediment control requirements shall conform to the current
requirements of NPDES/SDS Construction Stormwater General Permit.
c. Watershed District/Watershed Management Organization (WMO) requirements
The watershed organization with jurisdiction over the site may have additional
requirements such as site threshold for implementation or other applicable rules. The
applicant shall comply with the requirements of the watershed district or WMO.
IX. Inspections and Maintenance
a. Inspections and record keeping
i. Applicant responsibilities
The applicant is responsible for inspections and record keeping during and after
construction for all privately -owned stormwater treatment practices and
conveyances on the site.
H. City inspections
The city reserves the right to conduct inspections on a recurring basis to ensure
that both temporary and permanent stormwater management and erosion
prevention and sediment control measures are properly installed and
maintained prior to construction, during construction, and at the completion of
the project. The city shall be notified at the following milestones:
1. Upon installation of perimeter control, inlet protection and/or other
initial erosion prevention and sediment control practices.
2. Prior to commencement of construction of permanent stormwater
treatment systems.
3. Prior to placement of sod or other method of final turf establishment.
4. Prior to putting stormwater management practice(s) on-line.
Page 1 10
5. Prior to submittal for a Notice of Termination.
b. Right of entry and inspection
The issuance of a permit constitutes a right -of -entry for the city or its contractor to
enter upon the construction site for the purpose of obtaining information and
conducting inspections, surveys and investigations as may be necessary to assure
compliance with this ordinance, up to and including correcting deficiencies in
stormwater and erosion prevention and sediment control measures. The city shall be
allowed access to all pertinent records for examination and reproduction.
c. Fees
The city may assess a charge equal to the hourly rate of the staff or the billing rate of
the city contractor for any inspections under this ordinance by the city.
Enforcement tools/stop work orders
The city shall reserve the right to take actions to compel compliance with this ordinance
and ensure protection of public safety, property and natural resources.
i. Construction stop work order—The city may issue construction stop work
orders until stormwater management practices and/or sediment control
practices meet specifications and any damage has been repaired by the
applicant. An inspection by city staff must ensue before work can resume.
ii. Other enforcement tools — A city developed enforcement response procedure
can be found appended to the city's current Surface Water Management Plan.
Available actions may include the following:
1. Written notice of violation
2. Withholding inspections or issuance of certificates or approvals.
3. The city may conduct remedial or corrective actions and invoice the
applicant for the cost associated with the corrective actions.
4. If payment is not made within 30 days of taking the action, payment will
be made from the applicant's financial securities.
5. Failure to comply with this article will be considered a misdemeanor.
e. Longterm inspection and maintenance of stormwater facilities
I. Private stormwater facilities
1. Operations and Maintenance (0&M) Plan required - No private
stormwater facilities may be approved unless an operations and
maintenance plan is provided to and approved by the city. The plan
must define who will conduct the maintenance, the type of
maintenance and the maintenance intervals. This maintenance plan
shall be recorded against the property.
2. Facility Access - Access to all stormwater facilities must be inspected
annually and maintained as necessary. The applicant shall obtain all
necessary easements or other property interests to allow access to the
facilities for inspection or maintenance for both the responsible party
and the city.
3. Inspections - All stormwater facilities within the city shall be inspected
by the city during construction, during the first year of operation, and at
Page 111
least once every five years thereafter. This shall not abrogate the
applicant of their responsibilities under the approved O&M.
ii. Public stormwater facilities
1. Acceptance of Publicly Owned Facilities - Before work under the permit
is deemed complete; the permittee must submit as -built surveys, record
plans and/or certifications demonstrating at the time of final
stabilization that the stormwater facilities conform to design
specifications. These surveys shall be both hard copies and
georeferenced electronic format. A final inspection shall be required
before the community accepts ownership of stormwater facilities.
2. Maintenance - The community shall perform maintenance of publicly
owned stormwater facilities in accordance with their comprehensive
stormwater management plan and other regulatory requirements.
Access for city staff shall be provided to the facility and shall conform to
the city standards and details.
X. Financial Securities
A financial security in the form of a letter of credit or cash escrow shall be required from the
applicant. The security amount shall be 110 percent of the reasonable estimated cost to
construct the surface water management utility or BMP. The securities may be used by the
City to complete installation of said improvements should the developer fail to do so. The
security may be reduced as construction progresses at that city's discretion. Upon
acceptance of the utility the City shall retain up to 20% of the security for no less than two
(2) years after the utility performance has been verified.
XI. Surface water management utility established
a. Surface water management shall be operated as a public utility pursuant to M.S. §
444.075
b. The surface water management utility connection fees for any development requiring a
permit under this ordinance shall be calculated in accordance with Chapter 4 of the city
code.
c. Credits
The City council may adopt policies for adjustment of the surface water management
connection utility fee. Information to justify a fee adjustment must be provided by the
applicant or owner.
d. Exemptions
i. The following projects shall be exempt from paying a surface water
management utility fee:
1. Linear projects
2. Redevelopment that reduces hardcover by 20 percent or more
ii. The following land uses are exempt.
1. Wetland and buffer areas placed in an outlot and deeded to the City.
2. Public right-of-way.
3. Land dedicated for a city owned park.
4. Land placed into a permanent conservation easement.
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5. Other significant natural resource areas placed into an outlot and
deeded to the City.
XII. Surface water management fees.
The surface water management fees for tax parcels shall be calculated in accordance with
Chapter 4 of the City Code.
a. Credits - The city council may adopt policies for adjustment of the surface water
management fees. Information to justify a fee adjustment must be supplied by the
property owner. Adjustment of fees shall not be retroactive
b. Exemptions—the following land uses are exempt from the surface water management
fee:
i. Public right-of-way
ii. Lake area below the Ordinary High Water Level
iii. Land placed into a permanent conservation easement
XIII. Erosion and sediment control plans
An erosion prevention and sediment control plan shall be a stand-alone document that
shall include the following:
a. Site plans for existing and proposed conditions drawn to an appropriate scale. The plans
shall include the following:
i. Site location in relation to surrounding roads, steep slopes and/or bluff areas,
other significant geographic features, buildings and other significant structures.
ii. Site property lines.
iii. Area of disturbance including computation of disturbed area.
iv. Direction of drainage pre- and post -development.
v. Location of surface water features as defined in M.S. § 115.01, subd. 22,
including but not limited to, storm sewer inlet structures, wetlands, ponds,
streams, lakes, on or immediately adjacent to the site, and all appropriate
setbacks from these features.
vi. Identification of all receiving waterbodies and/or stormwater conveyance
systems to which the site discharges. Notation of an impaired or special
management waters status of waterbodies.
vii. Existing easements and utilities.
viii. Ingress and egress for equipment and materials.
ix. Location of stockpiled materials.
x. Locations of proposed runoff control, erosion prevention, sediment control and
temporary and permanent soil stabilization measures, including, but not limited
to: Inlet protection, perimeter control, temporary and permanent soil
stabilization, concrete wash areas, slope breaks, energy dissipation, rock
construction entrance, silt curtains.
A. Location of vegetation to be protected including protection measures.
xii. Turf establishment method or other method of final stabilization.
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b. Dewatering plan. If necessary, a dewatering plan shall be provided to the city for
review. The city must be noticed 24 hours prior to the commencement of any
dewatering activities.
c. Topsoil management
L Requirement. A minimum of six (6) inches of topsoil must be provided in all
green space areas of the project. Topsoil shall meet one of the topsoil standards
described below. When available onsite, topsoil shall be managed to protect
and/or restore soil permeability to non -compacted soil conditions following
construction.
1. Topsoil Standards
Topsoil used in all disturbed green areas on the site must meet one of
the following standards.
a. Chanhassen Topsoil Standard described in Chanhassen Standard
Specifications and Details Manual.
b. Match soil survey data. A site specific topsoil standard can be
developed using information on physical soil properties from
the Natural Resource Conservation Service's Web Soil Survey
from Carver County. The proposed site specific standard must
be submitted prior to permit approval.
2. Topsoil Replacement Methods
a. When available, on site topsoil (A soil horizon) shall be stripped
and stockpiled for later reapplication. Stockpiled topsoil shall
meet the standard selected for the project. If stockpiled
material does not meet the selected standard for the project,
the material shall be amended to meet the selected standard or
topsoil meeting the selected standard shall be imported to the
site.
b. If topsoil is not available on-site due to previous construction
activity or other constraints and existing material cannot be
amended to meet the Chanhassen Topsoil Standard, topsoil
meeting the standard shall be imported to the site.
3. A "Topsoil Management Plan" shall be submitted to the city for review
and approval. This may be included as part of the SWPPP but must
describe the topsoil management strategies to be used to restore soil
permeability to non -compacted conditions. At a minimum the following
elements must be included:
a. Methods for topsoil stripping and stockpiling.
b. Area of greenspace to be restored and quantity of topsoil
needed to meet the six inch requirement.
c. Topsoil sampling methodology including the number of samples
to be taken. At a minimum, one composite sample must be
taken for each 2,000 cubic yards of material stockpiled. No less
than one sample may be taken from any stockpile.
d. Method of topsoil reapplication including de -compaction.
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e. Schedule and phasing of topsoil application.
d. Stream bank stabilization and stream bed control structures, including intermittent,
ephemeral and perennial streams shall be designed based on the unique site conditions
present including soil conditions, flow rate, slope and flow velocity and shall be
consistent with Part 654 of the National Engineering Handbook: Stream Restoration
Design [H_210_NEH_654 - May 2008 or most recent revision].
XIV. Maintenance. The land owner, or permittee shall be responsible at all times for the
maintenance and proper operation of all erosion and sediment control management
practices. Specific maintenance requirements are as follows
a. Erosion prevention and sediment control BMPs shall be consistent with the
requirements of the NPDES/SDS Construction Permit regardless of the size of the site.
b. During construction of an infiltration or biofiltration system, rigorous prevention and
sediment controls must be used to prevent the discharge of sediment into the
infiltration/biofiltration area. Infiltration/biofiltration areas must not be excavated to
final grade until the contributing drainage area(s) has been constructed and finally
stabilized. Infiltration/biofiltration areas shall be protected from heavy equipment
operation and the stockpiling of materials.
c. A planting schedule and vegetation management plan shall be required for all
infiltration/biofiltration features.
d. 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. If
the tracked soil is not cleaned in a timely manner, the city may elect to clean the surface
and invoice the responsible party.
e. The removal and disposal of all erosion prevention and sediment control BMPs upon
final stabilization of the site.
XV. Inspections and notifications.
a. Work sites must be inspected once every seven days and within 24 hours of a 1.0 inch
rainfall event to assure that all sediment and erosion control elements are working
effectively.
b. Inspection and maintenance records must be maintained and retained with the erosion
control plan and/or SWPPP. Upon request, the inspection records must be made
available to the city within 24 hours.
c. The city may contract inspections out to the Carver County Soil and Water Conservation
District or other entities. The city may pass the costs on to the applicant.
d. The applicant or its authorized agent shall notify the city in writing at the following
points:
i. On completing installation of perimeter erosion and sedimentation controls.
ii. On completing land -disturbing activities and putting into place measures for
final soil stabilization and revegetation, but prior to placement of any sod.
iii. Whenever any site dewatering is proposed to take place.
iv. When the site has been permanently stabilized and revegetated.
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v. When all temporary erosion and sedimentation controls have been removed
from the site.
XVI. Financial assurance. To guarantee compliance with the plan, and related remedial work, a
cash escrow or letter of credit, satisfactory to the city, shall be furnished to the city before a
permit is issued. The escrow amount shall be not less than $250.00, but may be greater than
$250.00 if, after review of the site, the city deems it necessary to require a greater amount
to guarantee compliance. The maximum escrow allowable per parcel is $7,500.00 per acre.
The city may use the escrow or draw upon the letter of credit to reimburse the city for any
labor or material costs it incurs in securing compliance with the plan or in implementing the
plan. If the city draws on the escrowed funds, no additional permits shall be issued until the
pre -draw escrow balance has been restored. The city shall endeavor to give notice to the
owner or developer before proceeding, but such notice shall not be required in an
emergency as determined by the city. The assurance shall be maintained until final
stabilization and removal of erosion and sediment controls is completed.
XVII. Definitions.
Words or phrases used in this ordinance shall have the meanings as defined by Appendix B
of the Minnesota Construction Stormwater Permit No: MN 11100001 (Construction Permit).
If not defined in the Construction Permit or in Section 1-2 of city code, then words or
phrases shall be interpreted to have the meaning they have in common usage.
Words or phrases shall be interpreted so as to give this ordinance its most reasonable
application.
a. "Applicant' means the owner of land submitting an application under the provisions of
this ordinance for a stormwater and/or erosion control permit to be issued by the
community.
b. 'Better Site Design" means the control and management of stormwater quantity and
quality through the application of Better Site Design Techniques as outlined in the
current version of the Minnesota Stormwater Manual. Better Site Design includes:
preservation of natural areas; preservation of trees and other woody vegetation; site
reforestation; stream and shoreland buffers; open space design; disconnection of
impervious cover; rooftop disconnection; grass channels; stormwater landscaping;
compost and amended soils; minimization of grading; impervious surface reduction; and
trout stream protection.
c. "General contractor" means the party who signs the construction contract with the
owner or operator to construct the project described in the final plans and
specifications. Where the construction project involves more than one contractor, the
general contractor could be the party responsible for managing the project on behalf of
the owner or operator. In some cases, the owner or operator may be the general
contractor. In these cases, the owner may contract an individual as the operator who
would become the co -permittee.
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"Impervious Surface" means a constructed hard surface that either prevents or retards
the entry of water into the soil and causes water to run off the surface in greater
quantities and at an increased rate of flow than prior to development. Examples include
rooftops, sidewalks, patios, driveways, parking lots, storage areas, and concrete,
asphalt, or gravel roads.
e. "Land Disturbance" means any activity that result in a change or alteration in the
existing ground cover (both vegetative and nonvegetative) and/or the existing soil
topography. Land disturbing activities include, but are not limited to, development,
redevelopment, demolition, construction, reconstruction, clearing, grading, filling,
stockpiling, excavation and borrow pits.
Routine vegetation management and mill and overlay/resurfacing activities that do not
alter the soil material beneath the pavement base are not considered land disturbance.
In addition, other maintenance activities such as catch basin and pipe
repair/replacement, lighting, and pedestrian ramp improvements shall not be
considered land disturbance for the purposes of determining permanent stormwater
management requirements
f. "Linear Project' means construction or reconstruction of roads, trails, sidewalks, and
rail lines that are not part of a common plan of development or sale. Mill, overlay and
other resurfacing projects are not considered to be reconstruction.
g. "Development, new" Any development that results in the conversion of land that is
currently prairie, agriculture, forest, or meadow. Land that was previously developed,
but now razed and vacant, will not be considered new development'
h. "Public waters" means all water basins and watercourses that are described in Minn.
Stat. 103G.005 subd. 15.
i. "Redevelopment' means any development that is not considered new development.
j. "Retain" means manage stormwater on site using a low -impact development approach
so that the rate and volume of predevelopment stormwater reaching receiving waters is
unchanged.
k. "Stormwater" is defined under Minn. R. 7077.0105, subp. 41(b), and includes
precipitation runoff, stormwater runoff, snowmelt runoff, and any other surface runoff
and drainage.
I. "Underground waters (Groundwater)" means water contained below the surface of the
earth in the saturated zone including, without limitation, all waters whether under
confined, unconfined, or perched conditions, in near surface unconsolidated sediment
or regolith, or in rock formations deeper underground. The term groundwater shall be
synonymous with underground water.
m. "Waters of the State" (as defined in Minn. Stat. § 115.01, subd. 22) means all streams,
lakes, ponds, marshes, watercourses, waterways, wells, springs, reservoirs, aquifers,
irrigation systems, drainage systems and all other bodies or accumulations of water,
surface or underground, natural or artificial, public or private, which are contained
within, flow through, or border upon the state or any portion thereof.
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