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.4E <br /> Stormwater Technical Memorandum Perteet <br /> 2707 Colby Avenue,Suite 900,Everett,WA 98201 I P 425.252.7700 I F 425.339.6018 <br /> Summary <br /> The proposed project will have little stormwater impact. With the incorporation of roof drain flow dispersion, <br /> there will be no new effective impervious area and no need for additional BMPs. Table 2 below summarizes <br /> how the project will comply with each of the nine minimum requirements include in the Stormwater <br /> Management Manual. <br /> Table 2. Summary of Project Approach to Compliance with Minimum <br /> Requirements <br /> Requirement Project Conformance/Method of Compliance <br /> 1. Stormwater Site Plan This memorandum,in conjunction with the architectural <br /> Prepartion plans,will serve as the project stormwater site plan. <br /> 2. Construction As described herein,the project has a very low risk of <br /> Stormwater Pollution erosion during construction and will not require <br /> Prevention temporary BMPs. <br /> 3. Source Control of The project will not generate pollutants which require <br /> Pollution source control. <br /> 4. Preservation of Natural Discharge will be via splash blocks which will mimic <br /> Drainage Systems and existing drainage patterns. <br /> Outfalls <br /> 5. On-Site Stormwater On-site infiltration will be used to retain runoff onsite. <br /> Management <br /> 6. Runoff Treatment Not required as there e is no new pollution generating <br /> surfaces being added. <br /> 7. Flow Control As described herein,gravel zones will be included below <br /> the portables.These zones are sized to infiltrate all runoff <br /> fromor <br /> p table roofs. <br /> 8. Wetland Protection There are no identified wetlands within or near to the <br /> work area. <br /> 9. Operations and Everett Public Schools will incorporate maintenance of <br /> Maintenance the portable structures and downspouts into their <br /> existing site maintenance plan. <br /> Attachments: <br /> Attachment I —2012 WWHM Project Report <br /> Attachment 2— Targeted Drainage Report Silver Lake Elementary Parking Lot Expansion,January 2003 <br /> Attachment 3 — Silver Lake Elementary Additions-Schematic Design Narrative, Water, Sewer, Drainage <br /> October 2006 <br /> Attachment 4—Excerpts from Subsurface Exploration, Geological Hazard and Geotechnical Report- Silver Lake <br /> Elementary School Building Additions, Service Drive, and Water Line Installation, November 2006 <br /> Page 3 <br /> File location: X:\Everett Public Schools\Projects\20150040-Silver Lake Elementary Portables\Design\Drainage\Silver Lake Elementary Drainage <br /> Memorandum-Everett.docx <br />