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Ms. Katie Larsen <br />10/1/2025 <br />Page 2 <br />4. Address conflict between FES/storm sewer and retaining wall <br />a. Provide detail <br />5. Provide retaining wall details <br />a. Retaining Walls greater than 4' would require a City permit and be designed <br />by a structural engineer <br />6. Verify whether CBMH 1 or CBMH 3 can be shifted to eliminate CB(ST)MH 2 <br />7. Additional redlines on the plans to be addressed <br /> <br /> <br /> Stormwater Management <br /> <br />Stormwater management for 7920 Lake Drive site consists of constructing infiltration basins <br />on the east and west sides of the site. <br /> <br />Pre- and Post- Development Discharge Rates (cfs) <br />Condition 2-Year 10-Year 100-Year 10-Day Snowmelt <br />Existing* 0.84 1.81 5.21 Not required <br />Proposed 0.78 1.55 5.43 Not required <br />*Existing conditions is the updated modeling of the regional drainage system with assumed <br />developed landcover, the slight increase in 100-yr is still less than undeveloped runoff totals <br /> <br />Comments: <br />1. The proposed parking lot grading must be revised to raise it above the regional pond <br />HWL of 906.53. <br />2. CBMH 3 needs a sump to provide pretreatment of inflows to INF-1. <br />3. Rolled erosion blanketing containing natural netting is needed on proposed 3:1 <br />slopes. <br />4. Riprap stabilization is recommended instead of matting for INF-2 basin overflow. <br />5. Native vegetation must be shown over proposed infiltration BMPs and their side <br />slopes in the landscaping plan. <br />6. Trees should not be planted in the infiltration basin. <br />7. Exfiltration must be removed from the modeling for determination of site rate control <br />and HWLs. <br />8. HydroCAD modeling should use the separate impervious/pervious runoff mode in <br />model settings for most accurate hydrology. <br />9. Revise storm sewer to collect more of the surface flow from the eastern half of the <br />parking area. <br />a. Currently all surface flow goes to the southeast curb cut <br /> <br /> <br /> Water Supply <br /> <br />An 8” DIP CL 52 water service stub is supplied to the site. <br /> <br />Comments: <br />1. Show approximate location where existing utilities enter the building. <br />2. We recommend that the City Deputy Director of Public Safety-Fire Division review the <br />proposed plan for water supply and hydrant coverage. <br />7920 Lake Drive – Lino Lakes Dealership – Engineering Review <br /> <br />