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