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7-7 <br /> Runoff Control <br /> STREAMBANK EROSION CONTROL <br /> Mitigation for streambank erosion is required when a project proposes to add a net new 5,000 square <br /> feet or more of impervious surfaces. This work will add 545 square feet of impervious surface. The <br /> existing detention and water quality system was sized for 13.1 acres of impervious surface and <br /> currently only 12 acres of impervious surfacing are built. After this development the parcel will have <br /> 12 acres plus 545 square feet of area draining to the detention vault which is still less than the <br /> 13.1 acres it was sized for. No additional streambank erosion Best Management Practices(BMPs) <br /> are required. <br /> Runoff Treatment <br /> BMPs to remove sediments and other pollutants from runoff are required when a project proposes to <br /> add or replace 5,000 square feet or more of pollution generating impervious surfaces(PGIS). Water <br /> quality treatment is currently built on the site to mitigate for the full two-year release rate from the <br /> detention vault. The driveway/entryway where the impervious surface will be replaced already has <br /> runoff treatment provided for it from the previous site developments via the oil/water separator and <br /> bioswale. Even the new on-site drive aisle has already been accounted for in the on-site detention and <br /> water quality system,since it was designed for a full parcel build out of 13.1 acres. The site is <br /> currently 12 acres of impervious surface and this construction will only add 545 square feet of new <br /> impervious surface. This is less than the 13.1 acres assumed in the stormwater system sizing. <br /> Additional runoff treatment will not be required because treatment is already being provided. <br /> Community Transit <br /> Kasch Park Base 3 <br />