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SECTION VIII: PERMANENT STORMWATER CONTROL PLAN <br /> A. OFF-SITE ANALYSIS <br /> A site reconnaissance was performed by Brian Kalab of Insight engineering on <br /> October 1'1, 2018 to verify the downstream flow paths and observe any drainage problems <br /> downstream of the site. The sky was partly cloudy and overcast with a temperature of 61 <br /> degrees. <br /> The site is currently developed with a single family home with a garage and an <br /> asphalt driveway from Seahurst Ave. The site contains two drainage basins. Basin-1 which <br /> encompasses the majority of the site slopes to the moderately to the west. Basin-2 slopes <br /> moderately to the east. Per Per NRCS survey of Snohomish County, the project site <br /> contains Alderwood soils that have a hydrologic classification of Type"C". No visible on- <br /> site drainage problems were observed at the time of field investigations. <br /> Upstream Analysis <br /> Based on the site reconnaissance and the topographic survey of the site, the off-site <br /> area entering the site is very minimal. Refer to the Downstream Analysis Map attached in <br /> the next page for more details. <br /> Downstream Analysis <br /> The site contains two drainage basins. Basin-1 slopes to the west. The runoff from <br /> Basin-1 flows to he west and enters the existing drainage system along Seahurst Ave. The <br /> flow heads north west along El Charlee St through a 12-in PE pipe for about 518-ft and <br /> then heads west through a vegetated area for about 350-ft. It joins with the existing <br /> drainage system along Glenwood Ave and heads north west through a 15-in CP for 2,170- <br /> ft. The flow turns west along W Mukilteo Blvd through a 21-in pipe for about 440-ft and <br /> heads north along the Harborview park for about 1,110-ft and finally discharges into <br /> Pudget Sound. <br /> Basin-2 slopes to the east and the runoff enter the neighboring property. The flow <br /> heads north along the driveway and enters the existing drainage system along 51S' St SW <br /> which is a 12-in pipe. It heads I I0-ft east and turns north along 1011, P1 W. After about <br /> 500-ft, the flow enters a detention pond and it discharges into Glenhaven Creek. This creek <br /> Insight Engineering Co. -Stormwater Site Plan 07/24/19 <br /> -20- <br />