6525 HARDESON RD BASE FILE 2016-01-01 MF Import

EROSION CONTRfiL CALCULATIONS The temporary erosion and sedimentation control plan was designed to reduce the di.charge of sediment laden runoff from the site. The plan is comprised of temporary measures such as a rock wnstruction entrance, filter fence, swales etc. In general, runoff from Lot 1 will sheet flow across cleared ereas into temporary interceptor swales and be conveyed to the proposed detention pond. Runoff from Lot 2 will also sheet flow across cleared arees and into temporary interceptor swales and be conveyed to one of the two sediment ponds located at the northcast and northwest comers of Lot 2. The sediment ponds will then discharge into the proposed detention pond which i� tum will discharge into an existing tightline conveyance system located in Hardeson Road. In accordance with City of Everett standards, the sediment ponds were designed to have a design water sr face area large enough ro settle out the design particle (medium silt) at a 10-year inflow rate. A temporary erosion control hydrograph was generated for the ]0- year, 24-hour design stonn event assuming the entire site hac been cleared and graded. A summary of the calculations for a single sediment pond is included on the following page. This calculated surface area / volume was divided by two to provide the surface area / volume for each of the two sediment ponds since each pond serves approximately one-half of Lot 2. Srorm Drninage Report For King Erlrusion - Pnge 16 �