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Ms. Katie Larsen <br />12/20/2024 <br />Page 2 <br />Stormwater management for the 416 Lilac Street site consists of constructing a new <br />sedimentation basin on the northwest corner of the site. <br />Pre- and Post- Development Discharge Rates (cfs) <br />Condition <br />2-Year <br />10-Year <br />100-Year <br />10-Day Snowmelt <br />Existing <br />3.96 <br />6.14 <br />10.23 <br />Not required <br />Proposed <br />3.14 <br />5.12 <br />9.56 <br />Not required <br />Comments: <br />1. The City requires that the amount of untreated impervious is 15% of the site total. <br />Current plans show over 50% of the site impervious running offsite without treatment. <br />In order to meet parking requirements, the proposed basin will likely need to be <br />relocated. The City recommends shifting and/or relocating BMPs along the side and <br />rear easements. This would also allow to potentially treat additional areas. <br />2. Due to construction compaction, the pervious areas modeled in drainage area A.1 <br />must have curve numbers consistent with HSG C soils. <br />3. Pending the type of BMP, an outlet control structure with a submerged outlet pipe <br />may be needed. <br />4. A vegetation bench below the basin NWL is recommended. <br />5. Native seeding is needed around the proposed BMP and within the last 20' of the <br />proposed ditch to stabilize soils. <br />6. Rolled erosion blanketing containing natural netting is needed on BMP or pond <br />slopes. <br />7. Please clarify the gravel drive to 190th St N in the Existing Conditions section of the <br />Stormwater Drainage Report. <br />• Water Supply <br />A 6" PVC C900 water service stub is supplied to the site. <br />Comments: <br />1. Show approximate location where existing utilities enter the building. <br />2. Verify with MDH whether the proximity of an automotive use prohibits continued use <br />of the existing well. <br />a. Provide documentation to the City <br />3. We recommend that the City Deputy Director of Public Safety -Fire Division review the <br />proposed plan for water supply and hydrant coverage. <br />• Sanitary Sewer <br />A 6" PVC sanitary sewer service stub is supplied to the site. <br />Comments: <br />1. Show approximate location where existing utilities enter the building. <br />416 Lilac Street — BRF Enterprises - Engineering Review <br />