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(A) Any applicant proposing a land disturbance activity within the city that is one acre or greater or proposes a common plan development of sale that disturbs greater than one acre, shall apply to the city for a grading permit and shall submit a grading plan and a SWPPP with the application. No land shall be disturbed until the grading and SWPPP is approved by the city engineer and the grading permit is issued. At a minimum, the applicant’s SWPPP must include all items as required by the most current version of the NPDES general stormwater permit for construction activity, including but not limited to:
(1) BMPs to minimize erosion;
(2) BMPs to minimize discharge of sediment and other pollutants;
(3) BMPs for dewatering activities;
(4) Site inspections and records of rainfall events;
(5) BMP maintenance;
(6) Management of solid and hazardous waste on each project site;
(7) Final stabilization upon the completion of construction activity; and
(8) Criteria for the use of temporary sedimentation basins.
(B) Site inspections. Inspections will be conducted in accordance with the requirements of the NPDES general stormwater permit for construction activity.
(C) Post-construction stormwater management. Post-construction management applies to new development and redevelopment projects with land disturbance of greater than or equal to one acre, including projects less than one acre that are part of a larger common plan of development or sale.
(1) The permittee shall use permanent structural best management practices in order to achieve the applicable minimum control requirements as specified by the most current version of the NPDES/SDS Municipal Separate Storm Sewer (MS4) permit. The permittee shall use any combination of BMPs, with the highest preference given to green infrastructure techniques and practices necessary to meet the following conditions to the maximum extent practicable (MEP):
(a) There must be no net increase from pre-project conditions on an annual average basis of stormwater discharge volume, stormwater discharges of total suspended solids (TSS) and total phosphorus (TP) for new development projects.
(b) There must be a net reduction from pre-project conditions, on an annual average basis, of stormwater discharge volume, stormwater discharges of TSS and TP for redevelopment projects.
(2) The permittee is prohibited from using infiltration techniques to achieve the conditions in § 153.472(C)(1)(a) and (b)when the infiltration stormwater BMP will receive discharges from or be constructed in areas:
(a) Where industrial facilities are not authorized to infiltrate industrial stormwater under an NPDES/SDS Industrial Stormwater Permit issued by the Agency.
(b) Where vehicle fueling and maintenance occur.
(c) With less than three feet of separation distance from the bottom of the infiltration system to the elevation of the seasonally saturated soils or the top of bedrock.
(d) Where high levels of contaminants in soil or groundwater will be mobilized by the infiltrating stormwater.
(3) Infiltration techniques are prohibited, without higher engineering review, sufficient to provide a functioning treatment system and prevent adverse impacts to groundwater, when the infiltration device will be constructed in areas:
(a) With predominately Hydrologic Soil Group D (clay) soils.
(b) Within 1,000 feet up-gradient, or 100 feet down-gradient of active karst features.
(c) Within a Drinking Water Supply Management Area (DWSMA) as defined in Minn. Rule 4720.5100, subp. 13.
(d) Where soil infiltration rates are more than 8.3 inches per hour.
(5) The City Engineer or designee may allow for a lessor stormwater volume control than the requirements contained in § 153.472(C)(1)(a) and (b) under the following circumstances:
(a) The permittee is unable to infiltrate stormwater through a designed system due to the infiltration related limitations outlined in § 153.472(C)(2) or (3); or
(b) The permittee implements volume reduction techniques to the MEP, other than infiltration, (e.g., evapotranspiration, reuse/harvesting, conservation design, green roofs, etc.) on the site of the original construction activity that reduces stormwater discharge volume, but may not meet the conditions for post-construction stormwater management in § 153.472(C)(1)(a) and (b).
(6) The City Engineer may permit a permittee to mitigate TSS and TP requirements outlined in § 153.472(C)(1)(a) and (b), if the permittee cannot cost effectively meet the requirements on the site of the original construction activity. The City Engineer will designate the location of the mitigation project. The mitigation project must involve the creation of new structural stormwater BMP or the retrofit of an existing structural stormwater BMP, or the use of a properly designed regional structural stormwater BMP. Routine maintenance of structural stormwater BMPs required by the MS4 permit cannot be used to meet mitigation requirements of § 153.472(C)(1)(a) and (b). The mitigation project shall be completed within 24 months after the start of the original construction activity.
(7) Mitigation projects must be completed to the MEP in the following order of preference:
(a) Locations that yield benefits to the same receiving water that receives runoff from the original construction activity;
(b) Locations within the same Department of Natural Resource (DNR) catchment area as the original construction activity;
(c) Locations in the next adjacent DNR catchment area up-stream; and
(d) Locations anywhere within the permittee’s jurisdiction.
(8) The permittee, upon approval by the city, may elect to make a payment in lieu of a private mitigation project, as outlined in § 153.472(C)(1), as funding for a public stormwater project. The payment will be used to meet the TP and TSS requirements of § 153.472(C)(1)(a) and (b) utilizing the same criteria in § 153.472(C)(7).
(9) Long-term inspection and maintenance plans for privately-owned permanent stormwater management facilities are required. They must be submitted with the grading permit application and SWPPP to the city for review and approval.
(10) The owners of private stormwater structural BMPs, constructed after August 1, 2013, to meet the requirements of § 153.472(C)(1)(a) and (b), and are directly connected to the city’s MS4 are responsible for the long term operations and maintenance of the BMP. The owner shall allow the city engineer upon presentation of credentials, to access to the site at all times in accordance with the provisions of § 153.479. The city may assess the owner for maintenance costs if the owner fails to complete the required maintenance. The city may also direct the owner to modify, reconstruct or construct a new structural stormwater BMP, if the current structural BMP fails to meet the requirements of § 153.472(C)(1)(a) and (b). The city may assess the engineering and construction costs to the owner.