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I Introduction <br /> City of Everett <br /> EVERETT Reviewed for Permit 10/20/2021 <br /> WASHINGTON <br /> 1 .1 Water Treatment Overview <br /> Chitosan-enhanced sand filtration (CESF) on this project is a flow-through water <br /> treatment technology that utilizes a biopolymer to increase filtration efficiency. Chitosan <br /> is a natural biopolymer, derived from crustacean shells, that is nontoxic and completely <br /> biodegradable. Chitosan-enhanced sand filtration has been used extensively throughout <br /> the United States to treat storm dewatering water with exceptional results. The chitosan- <br /> enhanced sand filtration process is capable of reducing water turbidities to less than 10 <br /> NTU on a continuous, flow through basis. The CESF systems may also incorporate Poly <br /> Aluminum Chloride and/or BHR-P50 as needed, to treat for expected higher organic <br /> levels and tannins. Chitosan, Poly Aluminum Chloride and BHR-P50 are all water <br /> treatment chemicals accepted by DOE through a "Request for Chemical Treatment" <br /> document. <br /> A "flow through" CESF system along with other passive treatment methods and BMP's <br /> will be used on site to manage construction water. The CESF systems used on site will <br /> have a flow rate of 500 GPM and be configured and operated to meet the Washington <br /> State Dept. of Ecology BMP C-250 document, as well as the General Use Level <br /> Designation (GULD) for the specific treatment chemicals being used. <br /> 1 .2 Water Sources, Flow Rates and Collection <br /> This section only generalizes the various water sources that may be directed to the <br /> CESF systems during construction to confirm system sizing and design. The site <br /> Erosion Control plans address more specific details and means and methods for <br /> erosion control, collection, conveyance and temporary storage of site water as well as <br /> water quality compliance and monitoring. <br /> Storm water will be collected with temporary sumps and existing conveyance systems. <br /> Water quality will be monitored, and by-pass valves could be used when areas are <br /> remaining in compliance. Storm water will be collected in the new discharge structures <br /> and a properly sized pump will use over-land lines (HDPE and/or PVC) to transfer <br /> collected water across the site to temporary storage tanks. <br /> 6 <br />