Ordinance 444CITY OF CHANHASSEN
CARVER AND HENNEPIN COUNTIES, MINNESOTA
ORDINANCE NO.444
AN ORDINANCE AMENDING CHAPTER 19
CHANHASSEN CITY CODE, WATER, SEWERS AND SEWAGE DISPOSAL
THE CITY COUNCIL OF THE CITY OF CHANHASSEN, MINNESOTA ORDAINS:
Section 1. The City Code, City of Chanhassen, Minnesota, is hereby amended by adding
sections to be numbered 19-101 through 19-102, which shall read as follows:
Sec. 19-101. Unlawful discharge.
As provided in this Article and the city's NPDES permit, it shall be unlawful to discharge to any
storm sewer any pollutant waters.
Sec. 19-102. Regulations for use of storm sewer.
(a) No person shall throw, deposit, place, leave, maintain or keep or permit to be thrown,
placed, left, maintained or kept, any refuse, rubbish, garbage or any other discarded or
abandoned objects, articles, or accumulations, in or upon any street, alley, sidewalk, storm drain,
inlet, catch basin, drainage structure, business place, or upon any public or private plot of land so
that the same might be or become a pollutant, except in containers, recycling bags, or other
lawfully established waste disposal facility.
(b) No person shall intentionally dispose of grass, leaves, dirt, or other landscape debris into a
lake, wetland, storm water pond, wetland buffer strip, street, road, alley, catch basin, culvert,
curb, gutter, inlet, ditch, natural watercourse, ravine, flood control channel, canal, storm drain or
any fabricated natural conveyance.
(c) No person shall leave, deposit, discharge, dump, or otherwise expose any chemical or septic
waste in an area where discharge to streets or the storm sewer system may occur.
(d) No person shall use any storm sewer connection to intentionally convey non -storm water to
the storm water system.
(e) Objects, such as motor vehicle parts, containing grease, oil or other hazardous substances,
and unsealed receptacles containing hazardous materials, shall not be stored outdoors.
(f) Fuel and chemical residue or other types of potentially harmful material, such as animal
waste, garbage or batteries, which is located outdoors shall be removed as soon as possible and
disposed of properly. Household hazardous waste shall not be placed in a trash container.
10 (g) No person shall maliciously, willfully or negligently break, damage, destroy, uncover, deface
or tamper with any structure, appurtenance or equipment which is a part of the city storm sewer
system.
(h) The following activities shall be determined exempt from the provisions listed in this article:
(1) City staff or city contractors during the course of conducting maintenance activities; and
(2) Metropolitan Mosquito Control District during the course of conducting mosquito control
activities.
Section 2. Sections 19-140 through 19-148 of the City Code, City of Chanhassen, Minnesota,
are hereby repealed.
Section 3. The City Code, City of Chanhassen, Minnesota, is hereby amended by adding
sections to be numbered 19-140 through 19-146, which shall read as follows:
ARTICLE VII. SURFACE WATER MANAGEMENT.
Sec.19-140. Purpose.
The purpose of this ordinance is to implement standards to achieve the goals and policies set
forth in the city's Surface Water Management Plan in order to preserve, protect and improve the
• city's surface water resources.
Sec.19-141. Development standards.
These development standards shall be reflected in plans prepared by developers and/or project
proposers in the design and layout of site plans, subdivisions and water management features.
Sec.19-142. Plans required.
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. Standard details for many typical storm structures (e.g.,
storm sewer, outlet structures, catch basins, sump manholes, etc.) are available on the city's
website.
See.19-143. 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
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Minutes to 24 Hours and Return Periods from 1 to 100 Years, Technical Publication No. 40
(IT-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 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 rate 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:
a) 2-Year = 2.8 inches
b) 10-Year = 4.2 inches
c) 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.
Sec.19-144. 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, TR20fl R55,
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.
4
0 FJve Storage
Berm Dead Storagr Emcrgracy OwTflow
100 Year Ifi.0%atcr Lewi
(normal K'ater ievel
4' Average Depth
10` (10" Maidmupsr Brach
Aati-seJ
S�mfat Storage Voivae Cedar
Fba1 Bottom
• Bench areas promote growth of emergent Nwetation.
• hta imize distance bem-een the ou tlet and all Inlets to prevent short clrculting of flows.
(2) The facility design shall provide adequate live storage to provide protection from the
design storm, consistent with lowest building elevation standards. Lowest building floor
elevation is defined as the lowest slab elevation for a home or building, including basements
and crawl spaces. The lowest building floor 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 protection or
permanent cover within 3 days after the area is no longer actively being
worked. All other slopes that have a continuous positive slope to a special
water must have temporary erosion protection or permanent 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 of the
NPDES Construction General Permit must be used for common drainage
locations that serve an area with five (5) or more acres disturbed at one time.
2. Post construction. The water quality volume that must be treated by the
project's permanent storm water management system described in Part III.0 of
the NPDES Construction General Permit shall be one (1) inch of runoff from the
new impervious 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 maintained at all times.
Exceptions from this requirement for areas, such as water crossings or limited
water access, are allowed if the Permittee fully documents in the SWPPP the
circumstances and reasons that the buffer encroachment is necessary. All potential
water quality, scenic and other environmental impacts of these exceptions must be
minimized and documented in the SWPPP for the project.
4. Temperature Controls. The permanent storm water 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:
a. Minimize new impervious surfaces.
b. Minimize the discharge from connected impervious surfaces 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 withdrawal, vegetated swale
discharges or constructed wetland 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
ipoint.
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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 undermined 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.
•
Sec.19-145. 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 minimum distance of 75 feet (150 for wood
chips) beginning at existing paved surface; additional length may be required as directed by
the City. All construction traffic shall utilize the entire length of the rock entrance.
7
• 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.
Sec.19-146. Wetland elements.
(a) 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.
(b) Sedimentation basins or sediment removal devices shall be provided prior to discharge into
wetlands.
(c) 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.
Section 4. The City Code, City of Chanhassen, Minnesota, is hereby amended by adding
sections to be numbered 19-200 through 19-208, which shall read as follows:
ARTICLE VII. SURFACE WATER MANAGEMENT
See.19-200. Surface water management utility established.
0
Surface water management shall be operated as a public utility pursuant to M.S. § 444.075.
Sec. 19-201. Definitions.
The following words, terms, and phrases, when used in this article, shall have the meaning
ascribed to them in this section, except where the context clearly indicates a different meaning:
Surface water management budget is the annual budget approved by the city council for
surface water management including planning, monitoring, capital expenditures, personnel, and
equipment.
Surface water management fee means the quarterly charge for each parcel of nonexempt
property in the city for the management of surface water.
Utilityfactor means the ratio of runoff volume, in inches, for a particular land use, to the
runoff volume, in inches for a one -third -acre residential lot, assuming a two-inch rainfall and soil
conservation service (SCS) "type B" soil conditions.
Sec. 19-202. Surface water management fees.
The surface water management fees for tax parcels shall be calculated in accordance with section
4-50.
See.19-203. 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.
Sec. 19-204. Exemptions.
The following land uses are exempt from the surface water management fee:
(1) Public right-of-way.
(2) Lakes.
See.19-205. Payment of fee.
Surface water management fees shall be involved quarterly. The amount due as shown on the
invoice shall be payable on or before the twentieth day of the month in which the invoice is
issued. A penalty of ten percent per quarter shall be added to all accounts that are not paid in full
by the due date. The penalty shall be computed on the unpaid balance not paid by the due date at
the time each quarterly statement is prepared. Any prepayment or overpayment of charges shall
be retained by the city and applied against subsequent fees.
Sec.19-206. Appeal of fee.
If a property owner or person responsible for paying the surface water management fee believes
that a particular fee is incorrect, such person may file a written appeal with the city clerk.
W
C\� J
•
Appeals will be heard by the city council. No adjustment will be made to the utility factor for
property classifications 1, 2, and 3.
Sec. 19-207. Certification of delinquent fees.
If a surface water management fee is not paid within three months after a billing is issued, the
city council may certify the amount due, together with penalties, to the county auditor to be
collected with other real estate taxes on the parcel.
Sec.19-208. Surface water management fund.
A separate fund shall be maintained for surface water management fees and expenditures.
Section 5. This ordinance shall be effective immediately upon its passage and publication.
PASSED AND ADOPTED this 12`h day of February, 2007, by the City Council of the
City of Chanhassen, Minnesota.
Todd Gerhardt, City Manager
Thomas A. Furlong, Mayor
(Summary Ordinance published in the Chanhassen Villager on February 22, 2007)
10
• CITY OF CHANHASSEN
CARVER AND HENNEPIN COUNTIES, MINNESOTA
SUMMARY OF ORDINANCE NO.444
AN ORDINANCE AMENDING
CHAPTER 19 OF THE CHANHASSEN CITY CODE
WATER, SEWERS AND SEWAGE DISPOSAL
The purpose of this code amendment is to revise and update the water, sewers and sewage
disposal code of the City of Chanhassen including:
• Prohibiting unlawful discharges to storm sewers
• Restructuring the surface water management article
• Incorporating the city's development standards into the surface water management article
• Requiring landlocked storm water basins to hold back-to-back 100-year rain events
• Requiring additional storm water management techniques within the Assumption Creek
subwatershed to mitigate impacts of development to that resource
A printed copy of Ordinance No. 444 is available for inspection by any person during
regular office hours at the office of the City Manager/Clerk.
PASSED, ADOPTED, AND APPROVED FOR PUBLICATION this 121h day of
February, 2007, by the City Council of the City of Chanhassen.
(Published in the Chanhassen Villager on February 22, 2007)
0
•
•
CITY OF CHANHASSEN
CARVER AND ]HENNEPIN
COUNTIES, MINNESOTA
SUMMARY OF ORDINANCE NO.
444
AN ORDINANCE AMENDING
CHAPTER 19 OF THE'
CHANHASSEN CITY CODE
WATER, SEWERS AND SEWAGE
DISPOSAL
The purpose of this code
amendment is to revise and update
the water, sewers and sewage disposal
code of the City of Chanhassen
including:
Prohibiting unlawful discharges
to storm sewers
Restructuring the surface water
management article
Incorporating the city's
development standards into the
surface water management article
Requiring landlocked storm
water basins to hold back-to-back
100-year rain events
Requiring additional storm
water management techniques
within the Assumption Creek
subwatershed to mitigate impacts of
development to that resource
A printed copy of Ordinance No.
444 is available for inspection by any
person during regular office hours at
the office of the City Manager/Clerk.
PASSED, ADOPTED, AND
APPROVED FOR PUBLICATION
this 12t' day of February, 2007, by the
CityCouncilofthe CityofChanhassen.
(Published in the Chanhassen V illager
on Thursday, February 22, 2007; No.
4835)
Affidavit of Publication
Southwest Suburban Publishing
State of Minnesota)
)SS.
County of Carver )
Laurie A. Hartmann, being duly sworn, on oath says that she is the publisher or the authorized
agent of the publisher of the newspapers known as the Chaska Herald and the Chanhassen Vil-
lager and has full knowledge of the facts herein stated as follows:
(A) These newspapers have complied with the requirements constituting qualification as a legal
newspaper, as provided by Minnesota Statute 331A.02, 331A.07, and other applicable laws, as
amended. / 2
(B) The printed public notice that is attached to this Affidavit and identified as No. / ✓.�
was published on the date or dates and in the newspaper stated in the attached Notice and said
Notice is hereby incorporated as part of this Affidavit. Said notice was cut from the columns of
the newspaper specified. Printed below is a copy of the lower case alphabet from A to Z, both
inclusive, and is hereby acknowledged as being the kind and size of type used in the composition
and publication of the Notice:
abcdefghijklmnopgrstu yz
By.
Laurie A. Hartmann
Subscribed and sworn before me on
this day of , 2007
GWEN M. RADUENZ
NOTARY PUBLIC - MINNESOTA
_ i My Commissbn Expires Jan. 31, 2010
Notary Public
RATE INFORMATION
Lowest classified rate paid by commercial users for comparable space.... $40.00 per column inch
Maximum rate allowed by law for the above matter ................................ $40.00 per column inch
Rate actually charged for the above matter ............................................... $11.89 per column inch