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K:\017658-000\Admin\Docs\Memo - JMessner - Water Resource Analysis - DRAFT.docx540 GATEWAY BLVD | BURNSVILLE, MN | 55337 | 952.737.4660 | WSBENG.COMMemorandum <br />To: Justin Messner, WSB <br />From: Joey Abramson, WSB <br />Date: March 1, 2021 <br />Re: Boulevard Auto Car Wash – Water Resource Requirements <br />WSB Project No. 17658-000 <br />On behalf of the City of Saint Anthony Village, WSB conducted an analysis of water resource <br />requirements for the proposed Boulevard Auto Car Wash. Below summarizes each of the <br />applicable requirements. <br />Rate Control <br />Per the City’s Water Resources Management Plan (WRMP) Section 5.3.3.1, redevelopment <br />projects shall provide stormwater controls such that the critical Atlas 14 1-year, 2-year, 10-year <br />and 100-year storm events existing condition peak discharge rates are not increased following <br />site development. <br />Flood Control <br />Per WRMP Section 5.3.2.3, any new or redevelopment within the City will maintain two feet of <br />freeboard over the Atlas 14 100-year high water elevation or one foot of freeboard over the <br />emergency overflow elevation, and the lowest building floor elevation. <br />Volume Control <br />The project is located within the Mississippi Watershed Management Organization (MWMO) and <br />the City of St Anthony Village. <br />The MWMO’s standards language in their Watershed Management Plan requires that any <br />development that disturbs more than 1 acre of land to meet permanent stormwater management <br />requirements. <br />The project site is 0.81 acres and so the total disturbed area is not anticipated to exceed 1 acre. <br />Therefore, no permanent stormwater management is required per MWMO’s rules and therefore <br />no volume control or alternative sequencing is required. <br />Water Quality <br />WRMP Section 5.2.2.2 requires that NURP-level pretreatment is provided for all runoff leaving the <br />site as feasible. Providing 60% TP removal and 90& TSS removal will satisfy this requirement. <br />Storm Sewer Design <br />WRMP Section 5.3.2.2 requires that new storm sewer systems shall be designed to <br />accommodate a critical duration Atlas 14 10-year storm event, provided that the downstream <br />system has adequate capacity or storage available to accommodate this design. <br />61