1412 63RD ST SE 2020-05-06 - Laserfiche WebLink

3. Existing Conditions Summary The existing condition is an existing lot with a slope of less than 5% to the east and then south. The sheds that were on the lot have been removed and the lot is covered with piles of mulch, grass and some small areas of gravel. There is an existing 12" storm system in 63rd flowing east with a catch basin in the area of the proposed driveway. The existing soil is mapped as 5-Alderwood-Urban. As Alderwood soils can be suitable for infiltration a soil log was dug on site between the proposed house site and the road. The soil log showed hard gravel in the top 6", then hard brown gravelly, sandy silt to a depth of 14", and then moist hard gravelly silty sand with iron staining. This soil type continued to 36" where the soil became too hard to penetrate any further with a post hole digger. There are no critical areas on-site or adjacent to the site. The surrounding lots have all been developed with single family homes and there are no areas with a high potential for erosion and sediment deposition (based upon soil properties, slope, etc.) or areas of required tree retention as there are no significant trees on the site. 4. Off-site Analysis and Mitigation Proposed: Roof Area 2,509 S.F. D/W - Sidewalk 1,078 S.F. Total: 3,587 S.F Existing Removed & Replaced 621 S.f. Total New Impervious 2,966 S.f. 5. Upstream Analysis There is about 1/3 acre of yards and roof that appear to drain to this lot. The flows are all sheetflow so the proposed development should be able to take the existing flows and route them around the new building so they continue their current flow path. The analysis does not include any proposed mitigation as no significant drainage impacts from the development or redevelopment activity were identified in the upstream analysis. Kravchuk Targeted Drainage Plan Page 5