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Ms. Katie Larsen 9/3/2025 Page 3 elevations for the house pads are dependent on the groundwater elevation, the ordinary high water level (OWHL) of the Amelia Lake, and the design of the stormwater facilities. The existing parcels are within the Amelia Resource Management Unit. The applicant is proposing approximately 2.22 acres of new impervious surface for the proposed driveways and proposed house pads at this time. The proposed project is within the Vadnais Lake Area Water Management Organization (VLAWMO). Stormwater BMPs are needed to meet City stormwater and shoreland requirements. The applicant is proposing to meet City stormwater requirements by constructing several stormwater basins and infiltration basins. The design of the ponds shall meet the requirements of Table 6 of the City’s Stormwater Management ordinance. Comments: 1. The building pad Low Floor Elevations (LFE’s) must be 4 feet above the highest known groundwater level. The highest known groundwater level was estimated at elevation 910.5, corresponding to the mottles in SB3. The minimum LFE would therefore be 914.5. All LFEs are now above this elevation. 2.The LFE elevation of future homes shall not be lower than the HWL elevations of the adjacent storm basins. House pad elevations and pond elevations were adjusted so that all pond HWLs are lower than the adjacent future home LFEs. The proposed EOF and HWL levels for the basins on Lots 1 & 2 are at or just below the LFE. City staff meet and reviewed the EOF for the basins and the proposed lot grading. The pond runoff in high water conditions overflows directly to the lake and wetland. Staff recommends allowing the proposed basins to be constructed as currently shown in order to minimize impacts to natural features and use the existing topography. Per staff recommendation the basins were kept as shown. 3.For future maintenance purposes, the basins shall be located on the property for which they are treating impervious surface. Stormwater biofiltration basins have been relocated so that they are on the property for which they are treating impervious surface. 4.Filtration basins shall be located outside of the high vulnerability area shown in the Drinking Water Supply Management Area, see attached map. Please incorporate liners for the basins within the high vulnerability area. The high vulnerability area covers a significant portion of the project area, and it would not be possible to provide adequate stormwater treatment on each individual property outside of the high vulnerability area. It may also be noted that the proposed basins are biofiltration basins with an underdrain, and not infiltration basins. The likelihood of any contamination occurring because of these biofiltration basins is minimal to nonexistent. However, if still considered necessary, for the basins on proposed lots 1 and 2 (within the high vulnerability area) final plans will include a liner to be installed underneath the basin to prevent any stray infiltration. Applicant to include a clay liner for the basins on proposed lots 1 and 2. The basin detail has been modified to include the required clay liner for the basins on proposed lots 1 and 2. 5.Applicant to show the location of turf maintenance access to basins. Applicant to confirm access is traversable. Lake Amelia Woods Final Plat Engineering Review