10/13/2021 P&Z Packet - Laserfiche WebLink

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Ms.Katie Larsen 10/06/2021 Page 3 Comments: 1. The building par! Loy"'Cvv rlwrElevatie (LFE''s) must be n foo+-Ahoyp the highest knGWR n Rdwa+er level The highest known groURdwater level was estimated at elevation 910.5, corresponding to the mottles ,n So3. The minimum LFE would therefore be 914.5. All I FEs are now h this eTle +' e�ov^vc-crlrs-�.�i-'c'r^vrr. 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. 3 Cer fi It ire Fn iRtenaRGe purposes, the basiRS shall he Iena+ed ep the property fer whieh they are+rea+iRg impep,�ieus urfaGe Sterm.;.vatp_r biefiltFation basins have beeR relocated so that they are on the property fer igh4rh they a e+rea+iRg im rfaGe 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. 5. Applicant to show the location of turf maintenance access to basins. Applicant to confirm access is traversable. Turf maintenance access shown on revised plans. Turf maintenance access should not be located within the septic areas (see Lot 4). 6. Plans II show rep rap or I+ +iye +ahil'za+ien fer drain the _lAdeFdFa'n e��+va lcrcts. Diprap splash pad is ip.Jiva+e.J a plans fr,r 11n.Jerrlrain outlets. Detail will be included on final plans. 7. Provide calculations to confirm the adequacy of the sizing for the proposed culverts. The culvert shown on sheet CO2 velocity exceeds 6 fps. Design outlets to the wetlands to achieve an outlet velocity less than 6 fps. • Water Supply The existing properties are identified as part of the Stage 3 Planned Service Area in the 2040 Comprehensive Plan. There is not currently any existing water main along 20tn Avenue (CSAH 54) in this area. The 2040 Comprehensive Plan does identify a future 8" watermain loop in this area. The proposed homes will need to install wells. Lake Amelia Woods Preliminary Plat Engineering Review