All land disturbing activities, whether requiring a permit under this chapter or otherwise, shall be undertaken in conformance with the following:

   A.   City approved best management practices (BMPs) and the standards and criteria set forth in this chapter.

   B.   No person shall conduct land disturbing activities without protecting adjacent property and water bodies from erosion, sedimentation, flooding or other damage.

   C.   Land disturbing activities shall be planned and conducted to minimize the extent of disturbed area, runoff velocities, erosion potential, and to reduce and delay runoff volumes if possible. Erosion and runoff controls, consistent with approved BMPs, shall be properly installed before commencing land disturbing activities, and be sufficient to retain sediment on site. Erosion and runoff controls shall be regularly inspected and maintained per the approved SWPPP and NPDES/SDS construction stormwater permit requirements. Temporary and permanent vegetative cover shall be installed over all disturbed site areas per the approved SWPPP if the land disturbing activity ceases or is suspended, and upon completion. Pipe outlets shall be provided with temporary or permanent energy dissipation if connected to a surface water.

   D.   When possible, existing natural watercourses and vegetated soil surfaces shall be used to convey, store, filter, and retain runoff before discharge into public waters or a public or private stormwater conveyance system.

   E.   Runoff from new impervious areas is required to be pretreated prior to discharge into wetlands or infiltration BMPs.

   F.   When possible, runoff from roof gutter systems shall discharge onto lawns or other pervious surfaces to promote infiltration.

   G.   Use of fertilizer and pesticides in any shoreland protection zone shall be done so as to minimize runoff into public waters by the use of earth material, vegetation, or both.

   H.   When development density, topographic features, or soil and vegetation conditions are not sufficient to adequately handle runoff using natural features and vegetation, various types of constructed facilities such as diversions, settling basins, skimming devices, dikes, watercourses, and ponds may be used. Preference shall be given to designs using surface drainage, vegetation, and infiltration rather than buried pipes and manmade materials and facilities.

   I.   Whenever the city determines that a land disturbing activity has become a hazard to any person, endangers the property of another, adversely affects water quality or any water body, increases flooding, or otherwise violates this chapter, the owner of the land upon which the land disturbing activity is located, or other person, or agent in control of such land, upon receipt of written notice from the city, shall, within the time period specified therein, repair or eliminate such conditions. The owner of the land upon which a land disturbing activity is located shall be responsible for the cleanup and any and all damages resulting from sediment transported off such land. The city may require the owner to obtain a permit under this chapter before undertaking any repairs or restoration.

   J.   No person shall develop, redevelop or commence land disturbing activities on bluffs without protecting adjacent property and water bodies from erosion, sedimentation, flooding or other damage. (Ord. 30, 10-23-2008)

   A.   Plan And Permit Required:

      1.   Requirements: Unless specifically exempted by this chapter, no person or political subdivision shall commence a land disturbing activity without first developing an approved project specific stormwater management plan and obtaining a grading permit from the city. Land disturbance equal to or greater than one acre shall also require issuance of an NPDES general construction permit.

      2.   Application Requirements: Unless otherwise exempted by this section, an application for stormwater management approval shall include the following as a condition for its consideration:

         a.   A stormwater management plan; and

         b.   A maintenance agreement (if private stormwater management facilities are proposed).

The stormwater management plan shall be prepared to meet the requirements of subsection B of this section and the maintenance agreement shall be prepared to meet the requirements of subsection F of this section.

   B.   Criteria: Project specific stormwater management plans shall comply with the following criteria:

      1.   Methodology: A hydrograph method based on sound hydrologic theory and approved by the city will be used to analyze stormwater runoff for the design and analysis of flows and surface water levels. Green infrastructure techniques and practices (including, but not limited to, infiltration, evapotranspiration, reuse/harvesting, conservation design, urban forestry, and green roofs) shall be given preference as design options consistent with zoning, subdivision and public utility district requirements.

      2.   Drainage Patterns:

         a.   Existing drainage patterns to off-site areas and internal wetlands not approved for impacts (compliance points) must be maintained to the extent practicable. The requirements of this ordinance apply at each compliance point.

         b.   Existing runoff leaving the site as sheet flow must either be perpetuated at existing locations and rates or routed to a point draining to the sheet flow’s downstream eventual concentration of flow location. The new discharge location will be considered a compliance point and requirements of this section will apply.

      3.   Runoff Rates:

         a.   Stormwater runoff rates for the proposed activities, development or redevelopment shall:

            (1)   Not exceed existing runoff rates for the 1-year, 2-year, 10-year and 100-year, 24-hour storm events. Precipitation depths using NOAA atlas 14 volume 8 precipitation frequency estimates, published June 2013, or its successor, shall be used for each project location;

            (2)   Not accelerate on or off site watercourse erosion, create a downstream nuisance, or cause flooding or damage as determined by the city according to the downstream assessment provisions of this chapter;

            (3)   Runoff rates may be restricted to less than existing rates when necessary for the public health, safety and general welfare of the city; and

            (4)   The county soil survey shall be used to determine the hydrologic soil group for determining the curve number for land use covers.

      4.   Downstream Evaluation: The city will provide an assessment of the potential for adverse impacts downstream of a proposed project to determine if the project can proceed in advance of downstream regional improvements as it may deem necessary. To evaluate the impacts, the city will complete an evaluation downstream to the point where the proposed activity is ten percent (10%) of the drainage area (e.g., a 10 acre development must evaluate downstream to the point where the drainage area is 100 acres). The applicant shall identify the study area(s). The evaluation will consist of and include an assessment of:

         a.   Landlocked basin evaluations.

            (1)   The city will provide an assessment of water levels in the landlocked receiving water bodies resulting from the contributing watershed's full annual runoff yield during a 100-year wet year using the simplified hydrologic yield method (SHYM), or other methods for back to back 100-year, 24-hour storm events for existing conditions and fully developed watershed conditions.

            (2)   The applicant shall identify all public and private structures in the landlocked basin including: low floor and entry elevations of residences; individual sewage treatment systems (ISTS); and infrastructure (sanitary sewer, stormwater pipes, drain tile and facilities, and roads) surrounding the receiving water bodies and located within two (2) vertical feet of the elevation for the back to back 100-year, 24-hour storm event defined by the city.

            (3)   If there are public or private structures or infrastructure located within two (2) vertical feet of the back to back 100-year, 24-hour storm event elevation, the applicant shall provide corrective actions, delay the project until downstream regional infrastructure is in place, or revise the application.

         b.   Potential impacts to downstream infrastructure, public and private structures, and erosion along the drainage path and downstream public waters.

            (1)   The applicant shall identify:

               (A)   The existing public and private drainage easements;

               (B)   The locations, condition, and dimensions of the existing drainage infrastructure to the nearest regional stormwater facility, if any;

               (C)   The location and elevation of structures with low floors, or entries within two (2) vertical feet of the existing 100-year flood level;

               (D)   The location and description of known existing flooding problems;

               (E)   A hydrologic and hydraulic assessment of flooding impacts of the proposed project on downstream public and private structures;

               (F)   An assessment of existing and potential watercourse erosion, bank stability, bank protection, and watercourse slope;

               (G)   An assessment of the hydrologic and hydraulic capacity of the downstream public and private infrastructure; and

               (H)   An assessment of property damages including health, safety, and welfare impacts relative to increased flooding of public and private infrastructure. Minnesota department of transportation guidelines shall be used to assess safety of flood levels at downstream driveways and road crossings.

            (2)   If property damage, erosion, and public health, safety, and welfare impacts are identified, the applicant shall provide approved corrective action or delay the project until downstream regional infrastructure is in place or revise the application.

         c.   Potential impacts to wetlands with exceptional vegetative diversity functional value as defined in section 11-11-4 of this chapter.

            (1)   The applicant shall provide:

               (A)   Delineation and functional assessment of all wetlands on the subject site.

               (B)   Corrective actions that mitigate in proportion to the proposed project impacts if the water level bounce and period of inundation created by the alterations exceeds the limits specified in the following table. Corrective actions shall consist of runoff rate and volume controls necessary to keep the water level bounce and period of inundation within the limits specified in the following table:

 

 

            (2)   The city shall provide hydrologic and hydraulic analyses of the before and after project water level bounce and period of inundation for wetlands with exceptional vegetative diversity for the 1-year, 2-year and 10-year, 24-hour storm events.

      5.   Routing Capacity: All storm drainage conveyance systems shall have capacity for the runoff from a 10-year, 24-hour storm event. Runoff from larger events shall be routed by pipes or overland means to ponds and related systems. All storm drainage ponds and related facilities shall be designed to store and/or pass the runoff from the 100-year, 24-hour storm event or accumulative antecedent conditions without damage to the system or facility, downstream areas and/or significant risk to public health, safety, and welfare unless these stormwater management regulations are waived by the city.

      6.   Regional Detention Basins: Regional detention basins shall be used to manage peak flow rates and runoff volumes and meet water quality objectives when required by the city. The city may charge the applicant "cash in lieu of" fees for regional facilities, depending upon the degree of on site detention and treatment provided. On site stormwater detention basins, volume control facilities, and permanent sedimentation and water quality ponds will be used for land disturbing activities, the development or redevelopment of land that creates greater than one acre of impervious surface when regional basins are not in place or feasible, or would not otherwise meet requirements for the protection of downstream areas that are located between the project and the regional basin.

      7.   Landlocked Outlets: Landlocked water basins may be provided with outlets if an outcome based analysis and resource oriented management review regarding downstream impacts is completed that demonstrates:

         a.   A hydrologic regime is maintained that complies with the wetland and drainage alteration regulations;

         b.   Dead storage is provided to retain the fully developed future conditions SHYM predicted water volumes, or the back to back 100-year, 24-hour storm event volume, above the highest anticipated groundwater elevation while preventing damage to property adjacent to the basin;

         c.   The outlet does not create adverse downstream flooding or water quality conditions, or materially affect stability of downstream watercourses according to the criteria in this chapter;

         d.   Proposed development in tributary areas to the landlocked basin have incorporated runoff volume control practices to the extent practical;

         e.   There is a demonstrated need for an outlet to protect existing structures and infrastructure; and

         f.   The outlet design is part of an approved project specific stormwater management plan.

      8.   Treatment: Permanent sedimentation and water quality ponds shall be designed to the following standards:

         a.   Water quality features consistent with MPCA’s Construction Stormwater General Permit;

         b.   Ponds shall be designed to prevent short circuiting of the flow from the pond inlet to the outlet;

         c.   A normal water elevation above the OHW of adjacent water bodies, or normal water level (NWL) where an OHW is not established;

         d.   A minimum freeboard of one foot (1') above the pond's HWL and a minimum dike top width of four feet (4');

         e.   A submerged outlet six inches (6") or more from the NWL to the crown of the outlet pipe; and

         f.   Unobstructed vehicular access road to the safety shelf and outlet structure. The access shall be ten feet (10') wide or greater with slopes of fifteen percent (15%) or less in the running direction and five percent (5%) or less in the cross direction.

      9.   Structure Elevations: Any new residential, commercial, industrial, and other habitable structures shall be constructed with the following minimum low floor elevations:

         a.   In the case of a landlocked basin, the lowest floor elevation must be at least one foot (1'), and the lowest opening elevation must be at least three feet (3') above the surveyed basin overflow or the high water level of the basin as determined from an estimate using the SHYM, or 100-year, 24-hour back to back storm events, under full build out conditions for the contributing watershed.

         b.   Where the 100-year flood level has been established, the low floor and low opening elevations shall be at least one foot (1') above the 100-year flood level. Low openings shall be at least one foot (1') above the emergency overflow.

         c.   For public waters and public water wetlands (DNR protected water bodies) where the 100-year flood level has not been established, low floor and opening elevations shall be at least three feet (3') above the OHW.

         d.   In all other cases, the low opening elevation shall be at least three feet (3') above the highest known water level.

      10.   Volume Control:

         a.   Development and redevelopment that creates one acre or more in sum of new impervious plus fully reconstructed existing impervious surfaces and increases runoff volume shall meet both of the following two (2) volume standards:

            (1)   Volume standard 1: One inch (1") of runoff from the sum of the new and fully reconstructed impervious surfaces created by the project shall be retained on site and meet the requirements of the NPDES/SDS general permit. Impervious surfaces removed or reclaimed and replaced at the same or new grades shall be considered fully reconstructed.

            (2)   Volume standard 2: The proposed runoff volume shall be limited to the existing runoff volume for a 2-year, 24-hour storm. The use of infiltration to meet standard may be waived by the City for sites with predominately Type C and D soils, or where factors in 11.c. (7) percent construction of infiltration systems, provided the following are met in order of decreasing preference:

               (a)   BMPs and site design practices to minimize the creation of connected impervious surfaces are used to the maximum extent practicable.

               (b)   Underdrains are used to promote filtration instead of infiltration.

         b.   For linear projects, the water quality volume must be calculated as the larger of one (1) inch times the new impervious surface or one- half (0.5) inch times the sum of the new and the fully reconstructed surface. Where the entire water quality volume cannot be treated within the existing right- of-way, a reasonable attempt to obtain additional right-of-way, easement, or other permission to treat the stormwater during the project planning process must be made. Volume reduction practices must be considered first, as described in item 11.e.(10). Volume reduction practices are not required if the practices cannot be provided cost effectively. If additional right-of-way, easements, or other permission cannot be obtained, owners of constrution activity must maximize the treatment of the water quality volume prior to discharge from the project area.

         c.   At a minimum, volume control practices shall comply with the following:

            (1)   When using infiltration for volume control, infiltration volumes and facility sizes shall be calculated using the appropriate hydrological soil group classification and saturated infiltration rate Minnesota Stormwater Manual, and shall be capable of infiltrating the required volume within forty eight (48) hours. Site specific infiltration or hydraulic conductivity measurements completed by a licensed soil scientist or geotechnical engineer may be used in place of the values in the Stormwater Manual.

            (2)   Infiltration areas will be limited to the horizontal areas subject to prolonged wetting.

            (3)   The bottom area of treatment ponds shall not be accepted as part of an infiltration practice; however, properly designed slopes and safety shelves may be accepted.

            (4)   Before infiltrating runoff, pretreatment shall be required for gravel and paved surface lot runoff that will enter the infiltration system. The pretreatment shall be designed to protect the infiltration system from clogging and to protect groundwater quality. Pretreatment options may include, but are not limited to, oil/grease separation, sedimentation, biofiltration, filtration, swales or filter strips. To minimize potential groundwater impacts, it is desirable to infiltrate the cleanest runoff. To achieve this, a design may propose greater infiltration of runoff from low pollutant sources such as roofs, and less from higher pollution source areas such as parking lots.

            (5)   Infiltration systems shall be designed to bypass higher flows without incurring damage from erosion or loss of topsoil.

            (6)   Infiltration areas shall be fenced or otherwise protected from compaction and/or disturbance before and during all land disturbing activities.

            (7)   Constructed infiltration practices shall not be used in areas:

               (A)   that receive runoff from vehicle fueling and maintenance areas, regardless of the amount of new and fully reconstructed impervious surface.

               (B)   with less than three feet (3') of vertical separation from the bottom of the infiltration system to the elevation of seasonally saturated soils or top of bedrock.

               (C)   where soil infiltration rates are more than 8.3 inches per hour unless soils are amended to slow the infiltration rate below 8.3 inches per hour. For areas with runoff from industrial, commercial, and institutional parking lots and roads where there is less than five feet (5') of separation from the bottom of the infiltration system to the elevation of the seasonal high groundwater.

               (D)   where high levels of contaminants in soil or groundwater will be mobilized by the infiltration of stormwater.

               (E)   with predominately hydrologic soil group D soils.

               (F)   within one thousand feet (1,000') up gradient, or one hundred feet (100') down gradient of active karst features;

               (G)   in an Emergency Response Area (ERA) within a drinking water source management area (DWSMA) as defined in Minn. R. 4720.5100, Subp. 13, classified as high or very high by the (MDH).

               (H)   in an ERA within a DWSMA classified as moderate vulnerability unless the applicant performs, and the City approves, a higher level of engineering review sufficient to provide a functioning treatment system and to prevent adverse impacts to groundwater.

               (I)   outside of an ERA within a DWSMA classified as high or very high vulnerability unless the applicant performs, and the City approves, a higher level of engineering review sufficient to provide a functioning treatment system and to prevent adverse impacts to groundwater.

               (J)   that receives stormwater runoff from these types of entities regulated under NPDES for industrial stormwater: automobile salvage yards; scrap recycling and waste recycling facilities; hazardous waste treatment, storage, or disposal facilities; or air transportatio facilities that conduct deicing activities.

            (8)   The use of infiltration or green infrastructure techniques and practices shall be considered first for meeting the volume control standards. Examples of green infrastructure include the following practices: bioretention, evapotranspiration, reuse, harvesting, conservation design, green roofs, trees, or similar techniques on the site to reduce stormwater discharge volume. One or more of these practices treating the water quality volume defined in the MPCA General Stormwater Permit in total is required if infiltration is not feasible under the conditions listed above. Biofiltration practices must be used if infiltration is not feasible and other measures cannot retain the required volume on site.

            (9)   For non-linear projects, where the water quality volume cannot cost effectively be treated on the site of the original construction activity, the applicant must identify locations where off-site treatment projects can be completed. If the entire water quality volume is not addressed on the site of the original construction activity, the remaining water quality volume must be addressed through off-site treatment.

The applicant must ensure off-site treatment projects areas are selected in the following order of preference:

               (A)   locations that yield benefits to the same receiving water the receives runoff from the original construction activity;

               (B)   locations within the same Department of Natural Resource (DNR) catchment area (HUC 12) as the original construction activity;

               (C)   locations in the next adjacent DNR catchment area up-stream; or

               (D)   locations anywhere within City limits.

Off-site treatment projects must involve the creation of new structural stormwater BMPs or the retrofit of exiting structural stormwater BMPs, or the use of a properly designed regional structural stormwater BMP. Routine maintenance of structural stormwater BMPs cannot be used to meet this requirement.

Off-site treatment projects must be completed no later than 24 months after the start of the original construction activity. If the applicant determines more time is needed to complete the treatment project, the applicant must provide the reason(s) and schedules(s) for completing the project in writing to the City for approval.

      11.   Flood Storage:

         a.   Site alteration or filling shall not cause a net decrease in flood storage capacity below the projected 100-year flood elevation unless it is shown that the proposed alteration or filling, together with the alteration or filling of other land on the affected reach of the water body to the same degree of encroachment as proposed by the applicant, will not cause high water or aggravate flooding on other land and will not unduly restrict flood flows.

         b.   The applicant may be required to create compensatory storage to mitigate loss of flood storage.

   C.   Waivers: The city may waive the on site stormwater management criteria of this section if the city has regional stormwater facilities capable of meeting the requirements stated herein. Waiver of the on site stormwater facility siting requirements does not preclude the city from collecting appropriate stormwater area charges and/or cash-in-lieu of onsite stormwater management BMPs. (Ord. 137, 8-11-2016)

   D.   Maintenance: All stormwater management structures and facilities to be maintained by the city shall be located in outlots dedicated to the city. (Ord. 30, 10-23-2008)

   E.   Easements And Outlots:

      1.   The applicant shall dedicate or convey to the city easements or deeds to outlots for ponding, flowage, and drainage purposes over hydrologic features such as water bodies and stormwater basins as follows:

         a.   Easements: Flowage, drainage, ingress/egress, and conservation areas;

         b.   Outlots: Wetlands and associated buffers, infiltration basins, ponds and associated buffers.

      2.   Outlots and easements conveyed under this subsection shall include the right of ingress and egress for inspection, monitoring, maintenance, and enforcement purposes, including issuance of connection permits.

   F.   Private Stormwater Facilities:

      1.   Maintenance Agreement: While stormwater management facilities are generally owned and managed by the city, situations may arise where a private stormwater facility is appropriate. The applicant shall enter into a maintenance agreement with the city that documents all responsibilities for operation and maintenance of all stormwater treatment practices. Such responsibility shall be documented in a maintenance plan and executed through a maintenance agreement. The maintenance agreement shall be executed and recorded against the parcel. The maintenance agreement shall be in a form approved by the city, shall describe the inspection and maintenance obligations of this section and shall, at a minimum:

         a.   Designate the applicant, who shall be permanently responsible for maintenance of the structural or nonstructural measures.

         b.   Be designed to preserve the City’s right to ensure maintenance responsibility for structural stormwater BMPs not owned or operated by the City when those responsibilities are legally transferred to another party; and

         c.   Allows the City to conduct inspections of structural stormwater BMPs not owned or operated by the City, perform necessary maintenance, and assess costs for those structural stormwater BMPs when the City determines the owner of that structural stormwater BMP has not ensured property function;

         d.   Include a maintenance plan that contains, but is not limited to, the following:

            (1)   Identification of all stormwater treatment practices.

            (2)   A schedule for regular inspection, monitoring, and maintenance for each practice. Monitoring shall verify whether the practice is functioning as designed and may include, but is not limited to, quality, temperature, and quantity of runoff.

            (3)   Identification of the applicant for conducting the inspection, monitoring, and maintenance for each practice.

         e.   Identify a schedule and format for reporting compliance with the maintenance plan to the city.

         f.   Are designed to protect/preserve structural stormwater BMPs. If Structural stormwater BMPs change causing decreased effectiveness, new, repaired, or improved structural stormwater BMPs must be implemented to provide equivalent treatment to the original BMP.

      2.   Inspection Of Stormwater Facility:

         a.   Inspection programs shall be established on any reasonable basis, including, but not limited to: routine inspections; random inspections; inspections based upon complaints or other notice of possible violations; inspection of drainage basins or areas identified as higher than typical sources of sediment or other contaminants or pollutants; inspections of businesses or industries of a type associated with higher than usual discharges of contaminants or pollutants or with discharges of a type which are more likely than the typical discharge to cause violations of state or federal water or sediment quality standards or the NPDES stormwater permit; and joint inspections with other agencies inspecting under environmental or safety laws. Inspections may include, but are not limited to, reviewing maintenance and repair records; sampling discharges, surface water, groundwater, and material or water in drainage control facilities; and evaluating the condition of drainage control facilities and other stormwater treatment practices.

         b.   When any new stormwater treatment practice is installed on private property, or when any new connection is made between private property and a public drainage control system, sanitary sewer, or combined sewer; the property owner shall grant to the city an easement to enter the property at reasonable times and in a reasonable manner for the purpose of inspection. This includes the right to enter a property when the city has a reasonable basis to believe that a violation of this section is occurring or has occurred, and to enter when necessary for abatement of a public nuisance or correction of a violation of this section.

         c.   The city engineer, public works superintendent or designated representative shall inspect all stormwater management facilities during construction, during the first year of operation, and at least once every five (5) years thereafter. The inspection records will be kept on file at the public works department for a period of six (6) years. It shall be the responsibility of the applicant to obtain any necessary easements or other property interests to allow access to the stormwater management facilities for inspection and maintenance purposes.

      3.   Records Of Installation And Maintenance Activities: The applicant shall make records of the installation and of all maintenance and repairs of the stormwater treatment practices, and shall retain the records for at least three (3) years. These records shall be made available to the city during inspection of the stormwater treatment practice and at other reasonable times upon request.

      4.   Failure To Maintain Practices: If an applicant fails or refuses to meet the requirements of the maintenance agreement, the city, after reasonable notice, may correct a violation of the design standards or maintenance needs by performing all necessary work to place the stormwater treatment practice in proper working condition. In the event that the stormwater treatment practice becomes a danger to public safety or public health, the city shall notify the applicant in writing. Upon receipt of that notice, the applicant shall have thirty (30) days to perform maintenance and repair of the facility in an approved manner. After proper notice, the city may specially assess the owner(s) of the stormwater treatment practice for the cost of repair work and any penalties; and the cost of the work shall be assessed against the property and collected along with ordinary taxes by the county. (Ord. 137, 8-11-2016; amd Ord. 271, 3-23-2023)

Because of unique physical characteristics of a special parcel, advances in the science of stormwater management and the development of new technologies, it may be possible to meet the intent of this chapter with combinations of new and existing practices that provide equivalent performance. This chapter allows for the waiver of specific criteria based on documentation and review of equivalent approaches incorporated into project plans. Low impact development (LID) practices are encouraged to be utilized to reduce and mitigate water quality and rate impacts. (Ord. 30, 10-23-2008)

   A.   Permit Required: No person or political subdivision shall commence a land disturbing activity, unless specifically exempted by this section, without first obtaining a permit from the city that incorporates a SWPPP meeting the requirements of the MPCA for the activity, development, or redevelopment.

   B.   Criteria: Any SWPPP and the corresponding land disturbing activity shall comply with the following criteria:

      1.   Stormwater pollution prevention measures shall be consistent with approved BMPs, and shall be sufficient to retain construction generated sediment on the site.

      2.   Stormwater pollution controls shall be installed on all down gradient perimeters before commencing the land disturbing activity, and shall not be removed without city approval or receipt of a certificate of completion.

      3.   Stormwater pollution prevention measures shall meet the standards for the general permit authorization to discharge stormwater associated with construction activity under the national pollutant discharge elimination system/state disposal system permit program permit MN R100001 (NPDES/SDS general construction permit) issued by the Minnesota pollution control agency, as may be amended.

      4.   If the activity is taking place on a site where the soils are currently disturbed (e.g., a tilled agricultural site that is being developed), areas that will not be disturbed as part of the development and areas that will not be disturbed according to the time frames and slopes specified in the NPDES/SDS general construction permit shall be seeded with temporary or permanent cover before commencing the proposed land disturbing activity.

      5.   Where five (5) or more acres of disturbed soil drain to a common location, a temporary (or permanent) sediment basin must be provided prior to the runoff leaving the site or entering surface waters. The basins shall be designed and constructed according to the standards in the NPDES/SDS general construction permit and required herein.

      6.   The permittee or applicant shall be responsible for final stabilization of the site in accordance with the contract documents and the NPDES/SDS general construction permit requirements. The site will be considered as having achieved final stabilization following submission of a certificate of completion by the permittee or applicant, and inspection and approval by the city.

      7.   All temporary on site stormwater conveyance channels shall be designed and constructed to convey the expected runoff from a 10-year, 24-hour storm. Grading must direct all runoff up to and including the 100-year, 24-hour storm to any temporary or permanent stormwater management basins on the site.

      8.   Temporary sedimentation ponds shall be designed to provide:

         a.   An outlet structure and volume to control the 2-year, 10-year and 100-year, 24-hour storm events per the stormwater management regulations, section 11-11-2 of this chapter.

         b.   An identified overflow spillway and downstream route sufficiently stabilized to convey the 100-year, 24-hour storm event.

         c.   A normal water elevation above the OHW of adjacent water bodies or normal water level (NWL) where an OHW is not established.

      9.   Slopes greater than four to one (4:1) shall have an erosion control blanket installed immediately after finished grading.

   C.   Maintenance: The permittee or applicant shall be responsible for proper installation, operation, and maintenance of all stormwater pollution controls and soil stabilization measures in conformance with approved BMPs, and in conformance with the maintenance requirements in the NPDES/SDS general construction permit. The permittee or applicant is responsible for the operation and maintenance of temporary erosion prevention and sediment control BMPs for the duration of the construction work at the site. The permittee or applicant is responsible until another permittee or applicant has assumed control of the site according to the NPDES/SDS permit documentation over all areas of the site that have not been finally stabilized or until the site has undergone final stabilization, and has received an approved certificate of completion.

   D.   Security: Any security required in accordance with this title shall be maintained until final site stabilization and removal of erosion and sediment control BMPs have taken place, and the payment of all fees and other amounts due the city have been received and processed. (Ord. 30, 10-23-2008)

   A.   Wetland Application And Grading Permit Required: Wetlands or public waters wetlands shall not be drained, filled, excavated or otherwise altered without city approval of a wetland application and issuance of a grading permit from the city.

   B.   Wetland Criteria: Any drainage, filling, excavation or other alteration of a public waters wetland or wetland shall be conducted in compliance with the following:

      1.   Minnesota statutes section 103G.245, the WCA Minnesota rules 8420, and regulations adopted thereunder.

      2.   Treatment of stormwater runoff is required prior to discharge into a wetland or infiltration area.

      3.   Wetland replacement/mitigation siting shall follow the priority order below:

         a.   Mitigation on site.

         b.   Mitigation within the same major watershed within the city limits.

         c.   Purchase of wetland credits shall only be allowed by city agreement if the first two (2) preceding priorities cannot be met. The applicant will pay compensatory damage to the city per square foot of wetland filled according to the annual schedule of fees adopted by city council if mitigation beyond city limits or wetland bank credits are used.

         d.   Transportation projects can follow the BWSR road replacement program.

   C.   Buffer Criteria: The applicant for any land disturbing activity that requires a permit shall maintain or restore buffers and setbacks required for the original plat. Buffers adjacent to wetlands, waterways and ponds within the parcel boundaries are required to be maintained or established as follows for parcels platted after the effective date hereof:

      1.   A wetlands functional assessment for vegetative diversity shall be submitted by the applicant for each wetland delineated for a project. Buffers shall be maintained or established according to the following table. The functional assessment and wetland rankings will be determined using the Minnesota routine assessment method version 3.0 (MnRAM 3.0, as amended).

 

 

         a.   Exceptional Wetlands: Exceptional wetlands are most susceptible to human impacts, are most unique, have the highest community resource significance such as rare species habitats, and similar characteristics.

         b.   High Wetlands: High wetlands are relatively undisturbed but exhibit evidence of more disturbance or degradation than exceptional wetlands. High wetlands have conditions and functions that are susceptible to human impacts, are connected to other wetlands or watercourses, and may contain locally significant or rare wetland types.

         c.   Moderate Wetlands: Moderate wetlands typically provide a diversity of habitats and are connected to other wetland or upland habitats to provide wildlife habitat.

         d.   Low Wetlands: Low wetlands tend to be less susceptible to further impacts than the other wetland management classifications. They also have low diversity and connectivity to other wetlands and watercourses.

         e.   Stormwater Ponds: Stormwater ponds are ponds for treating and detaining stormwater.

      2.   The following buffer area sizes are minimum requirements for waterways identified on the waterway corridor classification map in the surface water management plan:

 

 

      3.   All structures shall have a minimum setback of thirty five feet (35') from the delineated edge of wetlands and the HWL of stormwater ponds.

      4.   The first twenty five feet (25') of buffer, as measured from the wetland, cannot be disturbed during project construction (i.e., cleared or graded, except for temporary disturbances for public roads and utility construction) and shall be protected from disturbance with temporary fencing prior to construction. Vegetation can be replaced and site soils preparation work completed within the first twenty five feet (25') if necessary to establish acceptable buffer vegetation in accordance with these wetland regulations.

      5.   Buffers shall apply whether or not the wetland is on the same parcel as a proposed development. An applicant is required to delineate the boundary for any wetland or portion thereof on the project land. An applicant shall not be required to delineate wetlands on adjacent property, but shall review available information to estimate the wetland boundary.

      6.   Buffer vegetation shall be maintained or, if necessary, established and maintained as follows:

         a.   Where acceptable natural vegetation exists in buffer areas, the retention of such vegetation in an undisturbed state is required unless an applicant receives approval from the city to replace such vegetation. A buffer has acceptable natural vegetation if it:

            (1)   Has a continuous, dense layer of perennial grasses that has been uncultivated or unbroken for at least five (5) consecutive years; or

            (2)   Has an overstory of trees and/or shrubs that has been uncultivated or unbroken for at least five (5) consecutive years; or

            (3)   Contains a mixture of the plant communities described above that has been uncultivated or unbroken for at least five (5) years.

         b.   The city may determine existing buffer vegetation unacceptable if:

            (1)   It is composed of undesirable plant species including, but not limited to, common buckthorn, purple loosestrife, leafy spurge, or noxious weeds; or

            (2)   It has topography that tends to channelize the flow of runoff; or

            (3)   For some other reason it is unlikely to retain nutrients and sediment.

         c.   Where buffers are not vegetated or have been cultivated or otherwise disturbed within five (5) years of the permit application, such areas shall be replanted and maintained. The buffer plantings shall be identified on the permit application. The buffer landscaping shall comply with the following standards:

            (1)   Buffers shall be planted with a seed mix approved by MnDOT, BWSR, NRCS, or SWCD, with the exception of a onetime planting with an annual nurse or cover crop such as oats or rye.

            (2)   The seed mix shall be broadcast according to MnDOT, BWSR, NRCS, or SWCD specifications for the selected mix. The annual nurse cover crop shall be applied at a minimum rate of thirty (30) pounds per acre. The MnDOT, BWSR, or NRCS seed mix selected for permanent cover shall be appropriate for the soil site conditions and free of invasive species.

            (3)   Native shrubs may be substituted for native forbs. All substitutions must be approved by the city. Such shrubs may be bare root seedlings and shall be planted at a minimum rate of sixty (60) plants per acre. Shrubs shall be distributed so as to provide a natural appearance and shall not be planted in rows.

            (4)   Any ground cover or shrub plantings installed within the buffer are independent of any landscaping required elsewhere by the city.

            (5)   Grasses and forbs shall be seeded or planted using a method of application that shall be approved by the city prior to planting or seeding.

            (6)   No fertilizer shall be used in establishing new buffers, except on highly disturbed sites when necessary to establish acceptable buffer vegetation and then limited to amounts indicated by an accredited soil testing laboratory.

            (7)   All seeded areas shall be mulched immediately with clean straw at a rate of two (2) tons per acre. Mulch shall be anchored with a disk or tackifier.

            (8)   Buffers (both natural and created) shall be protected by erosion and sediment control measures during construction. The erosion and sediment control measures shall remain in place until the area crop is established.

            (9)   During the first two (2) full growing seasons, the applicant shall replant any buffer vegetation that does not survive and must remove any volunteer trees, noxious weeds, or unintended vegetation by pulling or spraying in a manner that does not harm intended plants. The applicant shall be responsible for reseeding or replanting if the buffer changes at any time through human intervention or activities. At a minimum, the buffer shall be maintained as a "no mow" area.

      7.   When a buffer is required, the applicant shall, as a condition of permit issuance:

         a.   Provide to the city a dedicated outlot or conservation easement for buffers as part of platting and subdivision approval. The easement or outlot submitted shall describe the boundaries of the wetland or public waters wetland and buffer, identify the monuments and monument locations, and prohibit any of the alterations set forth below and the removal of the buffer monuments within the buffer, wetland, or public waters wetland;

         b.   File the approved easement for record and submit evidence thereof to the city, or complete preliminary and final plats including dedicated outlot(s); and

         c.   Install the monumentation required.

      8.   Subject to the exceptions below, activities including building, storage, paving, mowing, plowing, introduction of noxious vegetation, cuffing, dredging, filling, mining, dumping, grazing livestock, agricultural production, yard waste disposal, or fertilizer application are prohibited within any buffer. Noxious vegetation, such as European buckthorn, purple loosestrife and reed canary grass, may be removed.

      9.   The following activities shall be permitted within any buffer:

         a.   Placement, maintenance, repair or replacement of public roads, and utility and drainage systems that existed prior to creation of the buffer or are required to comply with any subdivision approval or building permit so long as any possible adverse impacts of public road, utility and drainage systems on the function of the buffer have been avoided or minimized to the extent practical;

         b.   Construction, maintenance, repair, reconstruction or replacement of existing and future public roads or trails within a buffer, so long as any adverse impacts of the facilities on the function of the buffer have been avoided or minimized to the extent practical.

         c.   Clearing, grading, and seeding is allowed if part of an approved wetland replacement plan.

         d.   Plantings approved by the city that enhance the natural vegetation or selective clearing of dead trees or pruning of damaged trees or removal of vegetation that is dead, diseased or poses a hazard.

      10.   Buffers shall be marked with signs to clearly designate the boundaries within a site. A sign shall be required at each parcel line where it intersects the outlot and at each change in easement or outlot alignment. Signs shall have a maximum spacing of two hundred feet (200') along the boundary. Additional signs shall be placed as necessary to visibly define the edge of the buffer. A sign shall consist of a post and a buffer sign. The signs shall be obtained from the city at the applicant's cost.

      11.   Other activities which would change the character of a wetland shall not diminish the quantity, quality, or biological diversity of the wetland.

   D.   Wetland Mitigation Monitoring: Wetland mitigation areas shall be monitored in compliance with wetland conservation act rules 8420.0810. During the growing season of each year, hydrologic and vegetative parameters shall be measured. A wetland monitoring report shall be prepared and submitted annually to the city by December 31 of each year during the five (5) year monitoring period. The monitoring reports shall include the following components:

      1.   A description of the project location, size, current wetland type (Cowardin or circular 39 classification), and desired wetland type (goal).

      2.   A comparison of the as built conditions in relation to the design specifications and a rationale for significant changes. During the first monitoring period, an as built survey drawing shall be submitted comparing the design contours with the as built contours.

      3.   A summary of water level measurements or soil pit data collected to date and a determination as to whether the hydrology in the wetlands meets the design elevations and wetland hydrology criteria as defined in the federal wetland delineation manuals. If standing water is expected, the hydrology of the mitigation areas shall be recorded throughout the duration of the monitoring period by installing staff gauges immediately upstream from each control structure and measuring water levels on a monthly basis during the growing season. In cases where there is little or no standing water, soil pits shall be dug, depth of standing water recorded, and the location of each pit located on a site plan of the mitigation site. Seasonal water level elevations shall be measured at least three (3) times during the period April through October (MSL or referenced to a known benchmark).

      4.   A list of the dominant vegetation in the wetland, including common names of the vegetation exceeding twenty percent (20%) coverage and an estimated percent of coverage. For wetland mitigation areas greater than one-half (1/2) acre, plant species data from at least two (2) sample locations shall be collected and their locations indicated on a site plan. Mitigation areas less than one-half (1/2) acre only need plant species from one sample location.

      5.   Color photographs of the project area taken during the period June through August, referenced to the fixed photo reference points identified in the wetland replacement plan and labeled accordingly.

      6.   A summary of management activities and/or corrective actions conducted in the wetlands during the previous year and activities planned for the following year (i.e., burning, tilling, regrading, herbicide application, reseeding, etc.).

      7.   The city reserves the right to extend the wetland monitoring period beyond five (5) years and require any monitoring securities be extended as part of an approved wetland replacement plan in the event that the wetland monitoring requirements are not met. It is possible that, based upon city determination, wetland establishment criteria will be achieved prior to completion of the five (5) year monitoring period, at which time, monitoring report requirements may be terminated and securities retired.

   E.   Security: A letter of credit, sufficient to pay for the cost of restoring the mitigated wetland areas shall be retained until the city has accepted and approved the wetland monitoring results. (Ord. 49, 1-14-2010)

   A.   Permit Required: No person or political subdivision shall construct, improve, repair, or alter a driveway, road, or utility across a watercourse with a tributary area in excess of one acre without first obtaining a permit from the city.

   B.   Criteria:

      1.   Bridge and culvert crossings shall:

         a.   Retain adequate hydraulic capacity.

         b.   Retain adequate navigational capacity, if applicable.

         c.   Not adversely affect water quality.

         d.   Represent the "minimal impact" solution to a specific need with respect to all reasonable alternatives.

         e.   Allow for future erosion, scour, and sedimentation considerations.

      2.   New road construction shall meet state and federal guidelines for freeboard and overtopping by flood events.

   C.   Maintenance:

      1.   The maintenance, reconstruction, and stabilization of any public crossing shall be the responsibility of the political subdivision with jurisdiction over the crossing.

      2.   The maintenance, reconstruction, and stabilization of any private crossing shall be the responsibility of the owner of the crossing, including crossings placed in public rights of way by permit.

      3.   As a condition to the approval of a permit, the city may require the applicant and owner to enter into a compliance agreement with the city. (Ord. 30, 10-23-2008)

No person or political subdivision shall artificially drain surface water, nor obstruct or redirect the natural flow of runoff, so as to affect a drainage system established under Minnesota statutes chapter 103E, or harm the public health, safety, and general welfare of the city, without first obtaining a permit from the city. The applicant for a drainage alteration shall:

   A.   Describe the overall environmental impact of the proposed drainage alteration and demonstrate that:

      1.   There is a reasonable necessity for such drainage alteration;

      2.   Reasonable care has been taken to avoid unnecessary injury to upstream and downstream land;

      3.   The utility or benefit accruing to the land on which the drainage will be altered reasonably outweighs the gravity of the harm resulting to the land receiving the burden;

      4.   That downstream impacts have been controlled or mitigated per the stormwater management regulations, section 11-11-2 of this chapter;

      5.   The drainage alteration is being accomplished by reasonably improving and aiding the normal and natural system of drainage according to its reasonable carrying capacity, or in the absence of a practicable natural drain, a reasonable and feasible artificial drainage system is being adopted.

   B.   Provide a hydraulic design that complies with all other regulations.

   C.   Provide a stable channel and outfall. (Ord. 30, 10-23-2008)

All known noncompliant ISTS in the ten (10) year capture area of wellhead protection areas (WHPA) within city limits, which have been identified by the county, shall be upgraded to conform with Minnesota rule 7080 within three (3) years of the effective date hereof. (Ord. 30, 10-23-2008)

The following operating standards shall be observed at any grading site permitted under this title:

   A.   Existing tree and ground cover shall be preserved to the extent feasible.

   B.   Noxious weeds shall be eradicated at the site. Upland and nonbuffer vegetation shall be kept mowed to twelve inches (12") maximum height to prevent weeds from going to seed and affecting neighboring properties.

   C.   The maximum noise level at the perimeter of the site shall be within the limits set by the Minnesota pollution control agency and the United States environmental protection agency.

   D.   Operators shall utilize all practical means to eliminate vibration on adjacent property from equipment operation.

   E.   Operators shall use all practical means to reduce the amount of dust, smoke, and fumes caused by the operations. When atmospheric or other conditions make it impossible to prevent dust from migrating off site, operations shall cease. (Ord. 30, 10-23-2008; amd. Ord. 298, 7-11-2024)

The following restrictions shall apply to all residential developments occurring in wooded areas.

   A.   Structures shall be located in such a manner that the maximum number of significant trees, as defined by the city subdivision ordinance 1 , be preserved.

   B.   Prior to granting a building permit, it shall be the duty of the person seeking the permit to demonstrate that there are no feasible or prudent alternatives to the clear cutting of trees on the site.

   C.   Forestation, reforestation or landscaping shall utilize a variety of tree species and shall not utilize any species presently under disease epidemic. Species planted shall be hardy under local conditions and compatible with the local landscape. (Ord. 5, 12-14-2006)

Lands which lie within the 100-year floodplain, including the floodway, floodway fringe and general floodplain, shall be subject to the provisions of the floodplain overlay district as provided in chapter 28, article D of this title. (Ord. 111, 7-24-2014)