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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 /> March 14, 2018 to verify the downstream flow paths and observe any drainage problems <br /> downstream of the site. The sky was clear and overcast with a temperature of 79 degrees. <br /> The site is currently undeveloped and covered with native vegetation. There is a <br /> wetland located to the east of the site, an associated buffer has been designated. The site <br /> contains one drainage basin that drains to the east to Pigeon Creek. Per NRCS survey of <br /> Snohomish County, the project site contains Alderwood Urban Land Complex 0 to 8 <br /> percent soils that have a hydrologic classification of Type "C" and Everett soil that have a <br /> hydrologic classification of Type "A". Please refer to the soils map and descriptions <br /> attached later in this report for more details. <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 /> Please refer to the Downstream Analysis Map attached in the next page for a description of <br /> the downstream flow. The site contains one drainage basin that sheet flows towards the east <br /> to Pigeon Creek. The site drainage enters Pigeon Creek at different locations. Pigeon Creek <br /> meanders north to its natural drainage path and eventually ends up in Puget Sound. A <br /> buffer has been set and showed on the plans due to the proximity to Pigeon Creek. <br /> No flooding problems were observed within 1 mile of the site. The proposed detention <br /> vault will store water that is currently flowing in an unrestrained manner and will meter a <br /> restricted flow into the downstream channel at smaller flow rates, which theoretically <br /> existed in the pre-historical condition of dense woodland. Therefore, the downstream <br /> channel is not expected to experience any increased peak flow rate. <br /> Insight Engineering Co. -Stormwater Site Plan 07/03/2019 <br /> -22- <br />