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Ms. Katie Larsen <br />04/02/2025 <br />Page 2 <br />3. Retaining walls exceeding 4' in height shall require a plan prepared by a Minnesota <br />licensed structural engineer submitted for review and approval by the Building Official <br />prior to permit issuance <br />a. Provide top and bottom of wall elevations at beginning and end of wall, at <br />point of maximum height, and at points along the length of wall to adequately <br />describe the retaining wall and to display final grading accurately. <br />b. Retaining walls are not allowed in easements or public rights -of -way <br />c. Provide fences for safety as required <br />4. Show all high and break points <br />5. Label all inlet elevations <br />6. Provide slopes across parking areas and along curbs <br />7. Minimize drainage areas to all underground parking entrances <br />a. Provide overflow options <br />• Stormwater Management <br />Stormwater management for the Wilkinson Waters site consists of a large sedimentation <br />basin and various smaller BMPs to provide additional treatment. There is also a proposed <br />future public street that must meet City design standards. Existing and proposed discharge <br />rates are summarized below. <br />Pre- and Post- Development Discharge Rates (cfs) <br />Condition <br />2-Year <br />10-Year <br />100-Year <br />10-Day Snowmelt <br />Needed if basins <br />Existing <br />25.47 <br />55.87 <br />127.68 <br />landlocked <br />Currently <br />Needed if basins <br />17.76 <br />45.54 <br />117.14 <br />Proposed <br />landlocked <br />Comments: <br />1. Compliance with stormwater requirements will be reviewed by the City. However, any <br />wetland impacts must be permitted through the LGU for the site, VLAWMO. <br />2. Per NURP design criteria, sedimentation basins must provide dead storage of at <br />least the 2.5" storm event volume of runoff from the tributary area. The 2.5" storm <br />event must be provided in future modeling to ensure compliance with this standard. <br />a. If this standard is met, additional pretreatment such as the SAFL Baffles and <br />rain gardens are not needed. These pretreatment BMPs are recommended <br />to be removed if Basin 1 is sufficiently sized so as to reduce future <br />maintenance needs. MIDS modeling is also not needed if Basin 1 is <br />demonstrated as meeting NURP design criteria. <br />3. A surfacewater reuse system is required. Rice Creek Watershed District staff may be <br />able to supply a water reuse spreadsheet for use in calculating water reuse rates and <br />areas for the site. <br />4. The steepest allowable slope below the 10' aquatic bench is 3: 1. Current grading of <br />2:1 is too steep and must be revised. <br />5. The outlet pipe for Basin 1 must be submerged at least 1' below the NWL. <br />a. Considering this basin is intended for irrigation reuse, the outlet pipe should <br />be set such that it is submerged even at the lowest planned water elevation. <br />Wilkinson Waters Development - Engineering Review <br />