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Irrigation System Two ponds within the development on the east and west sides of the site are proposed to provide the primary water quality treatment. These ponds are routed downstream to either of two pond options. Option 1: Route both downtown ponds via a large gravity pipe to the existing pond in St Genevieve's Church property. Option 2: Route both downtown ponds to a future constructed pond in LaMotte Park. Option 1 is dependent on discussions with St Genevieve's Church and detailed analysis of the existing pond. A pump would then be consVucted from either pond option connected to a proposed irrigation system in LaMotte Park. The irrigation system would reuse the downtown siormwater on the LaMotte Park fields, essentially eliminating discharge for small storm events. An adjacent groundwater supply well is recommended to feed the pond during dry conditions and allow for continued field irrigation. The concept of the irrigation system was discussed with RCWD staff. Ongoing discussions will be necessary to finalize the detailed system, but it is considered an acceptable BMP. There are � numerous benefits to irrigation systems utilizing stormwater — reduces runoff volume, spreads stormwater over large su�face area, beneficial for low permeability soils, provides evaporation, I biological uptake and soil adsorption, high pollutant removal efficiency, Utilizing the irrigation system provides the majority of the required bioretention volume needed to meet RCWD requirements for the downtown redevelopment. A portion of the area north of CSAH 14 cannot be gravity piped into this system based on existing grades and would require smaller scale BMPs as shown. Area 4 adjacent to Centerville Lake would also require small scale BMPs onsite. Refer to the attached sheet for general assumptions regarding the preliminary stormwater system design. I I Centerville lake TMDL Study Both Centerville Lake and Clearwater Creek are listed as impaired waterbodies by the MPCA — I a waterbody that does not meet water quality standards and designated uses because of "pollutant(s), pollution, or unknown causes of impairment". Clearwater Creek is impaired for fish and invertebrate index of biotic integrity and Centerville Lake is impaired for nutrients. RCWD is in the process of completing a TMDL study for CenteNille Lake. Additional stormwater analysis may be necessary once the TMDL study is accepted.