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SECTION III: SITE DEVELOPMENT PLAN W/ON-SITE <br /> STORMWATER MANAGEMENT <br /> The site area is 0.98 acres with a clearing area of 1.03 acres. The proposal includes <br /> removing the existing building and construction of a new building, sidewalks, and planters. <br /> Access to the site will be from Evergreen Way and Holly Drive. A detailed breakdown of <br /> all the site's areas has been included under Appendix A. <br /> The site is currently developed with an existing commercial building with <br /> associated parking and exists as almost entirely impervious apart from planters in the <br /> northwest and southeast corner of the site. The site is relatively flat and consists of two <br /> drainage basins of which the respective flows do not converge within Y4 mile downstream <br /> of the site. Therefore, the site contains two threshold discharge areas: Basin "A" contains <br /> 0.42 acres in the northwest portion of the site draining to Evergreen Way and Basin "B" <br /> consisting of 0.61 acres to the southwest and draining to Holly Dr. Please refer to the Basin <br /> Maps provided in Section III of this report for more information. Per NRCS survey of <br /> Snohomish County, the project site contains Alderwood Urban Land Complex 2 to 8 <br /> percent soils that have a hydrologic classification of Type "C". Please refer to the soils map <br /> and descriptions attached later in this report for more details. <br /> The total disturbed area for Basin A will be 0.42 acres. The total new hard surface <br /> is 0.02 acres (1,030 SF) and the total hard surface replacement is of 0.19 acres (8,173 SF). <br /> 4,560 SF of the replaced hard surface will be replaced with permeable asphalt to infiltrate <br /> and be rendered ineffective impervious. The total effective impervious surface for the basin <br /> is 4,643 SF. Minimum requirements 1-9 apply to Basin A as the proposal involves <br /> replacement of more than 5,000SF of impervious surface. Refer to the Flowchart for <br /> Determining Requirements for Redevelopment attached in the next page. Basin A is <br /> exempt from flow control as there will be less than a 0.15 CFS increase in offsite runoff <br /> and the effective impervious are is 4,643 SF which is less than the 5,000 SF threshold <br /> requiring flow control. See Section 8D of this report for the hydraulic calculations. Water <br /> quality is also exempt as the proposed PGHS is 4,902 SF which is less than the 5,000 SF <br /> Insight Engineering Co. -Stormwater Site Plan 12/20/2018 <br /> - 14- <br />