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Ms. Katie Larsen <br />06/03/2020 <br />Page 5 <br />area is an 897 to 899. They are not meeting the 4 foot of separation from groundwater <br />It is being proposing to mitigate this with a drain tile and pump system, backup power, <br />and cut off wall. <br />The City could consider reducing the low floor free board requirement of 4 feet <br />separation from groundwater upon submittal of a geotechnical report and design by a <br />licensed engineer. This report shall define ground water level elevations for the senior <br />living complex and include plans demonstrating that potential ground water inflow will <br />adequately be mitigated. The proposed trench grate and draintile will need to be <br />pumped or discharged downstream of the pond. <br />It is recommended to construct an improved outlet for the site, downstream of the pond <br />It is our understanding that this option would have construction impacts in an existing <br />developed area. <br />This underground dewatering system is being designed by Braun Intertec. Refer to <br />information submitted by Braun. (AJA 2020-05.08) <br />The applicant shall show the proposed storm sewer for the turn lanes. We are <br />concerned that there may not be enough grade between the turn lanes and the pond to <br />ensure proper drainage. <br />10. The applicant shall review locations of manholes 106, 111, 112, and 123. These <br />manholes appear to be in the road and possibly within wheel paths. <br />11. The applicant shall review Detail 9 on C2.13 of the final plat plans and indicate where <br />this detail is being used on the site. If not being used, please delete the detail. <br />12. Narrative describing the coordination for the site between stormwater management, <br />groundwater, and subslab system must be included in the stormwater management <br />plan. <br />13. Sheet C1.40 shows three different outlets discharging off -site. These outlets appear to <br />be: 1) storm sewer outlet from pond, 2) draintile for pond, and groundwater draintile <br />system. The outlet must be limited to one pipe discharge. Draintile must tie into storm <br />sewer outlet. <br />14. Draintile shown around 3P North Pond is not discussed in stormwater management <br />plan, nor are any elevations or notes included on the plans. Include a description of the <br />purpose of this draintile pipe around the pond within the stormwater management plan. <br />Include elevation, size and material of the draintile and a detail if it requires any <br />additional rock or fabric with installation. <br />15. Detail 12 on Sheet C2.11 should detail the specific requirement for the type of fill for the <br />pond embankment fill. <br />16. The pipe inverts and rim elevation in OCS 2 detail on Sheet C2.14 do not match the <br />HydroCAD model. Confirm which information is correct and update so that they are <br />consistent. <br />17. SUB SLAB DRAINAGE SYSTEM: <br />a. Provide invert elevation for tie in locations at storm sewer manholes. <br />b. Provide invert elevation, slope, material, and size of pipe. <br />c. Provide a construction detail for draintile installation. <br />d. Include linework for this system on the storm sewer sheet so it can be compared <br />with the other storm system management designs. <br />18. GROUNDWATER DRAINTILE SYSTEM: <br />Lyngblomsten Preliminary Plat Engineering Review <br />