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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 2 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. 0 (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