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Memo To:Mark Statz From: Dan Edgerton City of Centerville Stantec – Minneapolis File: 193804960 Date:February 19, 2020 Reference: City of Centerville – LaMotte Park Stormwater Reuse Expansion Future downtown redevelopment within the City, including the 2020 Downtown Area Street and Utility Improvements (SUIP), will need to meet Rice Creek Watershed District (RCWD) Rule C requirements for water quality treatment. This memo discussed how the LaMotte Park stormwater reuse (irrigation area) expansion can help meet RCWD requirements in 2020 and moving forward. LaMotte Park Irrigation System Expansion The existing irrigation system has 7 “gun-style” irrigation heads (190’ water distribution radius) and covers approximately 11.1 acres of pervious irrigated area, as shown in attached Figure 1 – Existing and Proposed Irrigated Areas. Proposed system improvements include a base design and two alternatives, detailed in the table below. The base design and each alternative are shown on Figure 1. Alternative Irrigated AreasArea Increase (ac) Base Lamotte Park: 3 additional “gun-style” heads, infield irrigation (conventional), and3.62 Hidden Springs Park irrigation (conventional) Alternative 1 Base + SPRWS Lot irrigation (conventional) 4.08 Alternative 2 Base + Alternative 1 + MCES & Church Lots irrigation (conventional) 8.32 Potential RCWD Rule C Credits Met Council Water Reuse Spreadsheets (updated per RCWD Rules) have been completed to display existing and proposed conditions for each alternative. The “Increase in Impervious Area Treated” shows the amount of additional impervious area (over existing conditions) that could be credited (Rule C) with the increase in irrigated area. Water Reuse Spreadsheet results are shown in the table below, and individual alternative results are attached. Existing Base Alternative 1 Alternative 2 Impervious Area Draining to Supply (ac) 38.238.238.2 38.2 Irrigation Storage \[pond\] Volume (af) 0.919 0.919 0.919 0.919 Pervious Area to be Irrigated (ac)11.014.62 15.08 19.32 Impervious Area Treated (ac) 7.218.708.86 10.10 Increase in Impervious Area Treated (ac) NA 1.491.65 2.89 2020 SUIP and Beyond Pending upcoming discussions with RCWD staff, the increased irrigation areas should allow water reuse credits to be applied to upcoming downtown redevelopment projects, including the 2020 SUIP. The 2020 SUIP has 17,200 sf (0.4 ac) of new impervious area, which could be accounted for with the 1.49 ac of credits provided under the base design. Thus, the base design would cover the 2020 SUIP while leaving 1.09 ac of credit for future downtown redevelopment. ed \\\\us0291-ppfss01\\workgroup\\1938\\active\\193804960\\design\\stormwater\\rcwd_permit\\centerville_rcwd_waterreuse_finalmemo_02192020.docx