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MINIMUM REQUIREMENT NO. 1 — Preparation of Stormwater Site <br /> Plans <br /> Project Overview and Executive Summary: <br /> This document is intended to provide engineering information necessary and demonstrate <br /> compliance with Minimum Requirements 1 through 9 per the Stormwater Management <br /> Manual for Western Washington (SWMMWW) and the City of Everett's Stormwater <br /> Management Manual. The total parcel is 0.35 of an acre. Currently there is an existing <br /> one single family home structure and a detached garage. There is an existing driveway <br /> providing access to the site of 4t" Ave. W. <br /> This project proposes to remove existing single family house structure, detached garage, <br /> existing driveway and construct one new duplex structure and driveway access serving both <br /> units. <br /> This project will create a total of 6,779 sq. ft. new impervious surfaces of which only 3,254 <br /> sq. ft. of pollution generating impervious surface (PCIS) from driveway access to the <br /> structures. The reminder of the new created impervious surface is 3,525 sq. ft. is non- <br /> pollution generating impervious surface (NPGIS) from roof tops and walkways. <br /> This report has been prepared to fully comply with Stormwater requirements within <br /> the city of Everett that are established in Everett Municipal Code (EMC) 14.28, the <br /> City of Everett Stormwater Management Manual and the most current Washington <br /> State Department of Ecology Stormwater Management Manual for Western <br /> Washington. <br /> This project has been designed to collect all runoff from the new impervious and pervious <br /> surfaces proposed on this site. Flows will be directed as in existing condition. Runoff from <br /> driveway will be directed and sheet flow toward sheet flow dispersion system (BMP T5.12) <br /> and runoff from roof areas will collected by pipe drains and will be directed to an onsite <br /> dispersion trench system (BMP T5.1 OB). The remainder runoff from this site ifanywill be <br /> minimal. <br /> This submittal package contains plans showing the proposed on-site grading. This <br /> project will require minimal grading, the grading is for new duplex structure <br /> foundation and for driveways sub-grade and surfacing as shown on site plans. In <br /> addition, cut material will be generated on the site and will used as fill around the <br /> structure foundation. Excess material, if any, will be disposed of off-site at an approved <br /> dumping location. <br /> The drainage plan has been prepared with consideration for the site grading by collecting <br /> all runoff from the new on-site impervious and pervious surfaces and releasing the flows <br /> to the onsite existing conveyance system at a rate no greater than 0.15 cfs over the <br /> existing 100-year conditions, this project will not have any significant impacts on the <br /> existing downstream drainage system. In addition, the necessary erosion control <br /> measures will be provided to protect the exposed soil during construction and once final <br /> grading is completed. <br /> At this time no erosion hazard areas, landslide hazard areas or seismic hazard areas <br /> have been identified on or adjacent to this site. <br /> Drainage Report—9227 4t"Ave W Everett,WA 98204 <br /> Nov. 10,2022 Page 3 <br />