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Additional BMP Summary Sheet MS4 Name: Centerville Minimum Control Measure: Not applicable Unique BMP Identification Number: 7-3 (see Centerville SWPPP) *BMP Title: Response to Listing of Impaired Water(s) *BMP Description: The following terms are used in the course of this BMP Description: . trigger event . impaired waters evaluation . impaired waters report These terms are used to describe steps of a process to address a specific MS4 Permit requirement. These terms do not imply or mandate the creation of written reports or materials that must be submitted to the MPCA. Written documentation from these steps will be retained as part of the City's MS4 Permit records. These records will be retained as per Part VI.B. of the MS4 General Permit and available to the MPCA upon request. For waters that are impaired only for mercury, only Step 1 of this BMP will be implemented. Based on the Minnesota statewide mercury TMDL, it is assumed that the City's MS4 discharge does not contribute to the mercury impairment. This assumption also applies to waters with multiple impairments that include mercury. For these waters, only the other non-mercury impairments must be addressed through Steps 2 through 5. As per 40 CFR 122.2 and 122.3, the measures in this BMP will not be applied to flows from irrigated agriculture or agricultural stormwater runoff within the City's jurisdiction. The steps included in this BMP will be instigated by one or more of the following trigger events: 1: the extension of MS4 Permit coverage upon approval of the City's submittal materials and Application by the MPCA Commissioner (if this BMP is already incorporated into the SWPPP) 2: the release of a new 303(d) list of Impaired Waters by the MPCA that is approved by the USEPA. In SleD 1, the City will review the Impaired Waters List to determine whether there are any impaired waters located within five miles of the City's boundaries that receive discharge from the City's MS4. Such waters will be identified as "impaired waters of concern". This term is used only for the purposes of this BMP to define the set of impaired waters that must be addressed in the subsequent steps. The City will depend on the 303(d) list of Impaired Waters to make this determination. Where the information in the list is insufficient, the City will contact the MPCA for further clarification. In SteD 2, the City will identify the location(s) of discharge(s) from the City's MS4 to the impaired waters of concern identified in Step 1. Discharges may include pipes, outlets, ditches, swales, street gutters, or other discrete conveyances for stormwater runoff. As part of Step 2, the City will also delineate the watershed area within the City's jurisdiction that discharges to each impaired water of concern identified in Step 1. In SteD 3, the City will prepare an impaired waters evaluation addressing the hydrology, land use, and other characteristics of each watershed area delineated in Step 2. In SteD 4, the City will prepare an impaired waters report. This report will address the results of the steps listed above along with a determination of whether changes to the City's SWPPP are warranted to reduce the impact from the City's MS4 stormwater discharge to each impaired water of concern. In SleD 5, the City will incorporate the changes identified in the impaired waters report into the City's SWPPP, as per the provisions of the MS4 General Permit regarding SWPPP modifications. The changes to the SWPPP will be reported in the subsequent Annual Report, along with a summary of the process (as listed above) that resulted in the changes. Location(s) in SWPPP of detailed information relating to this 8MP: 8MP Page 7-3 Page 66 of 67