11625 AIRPORT RD SONRISE CHRISTIAN CENTER 2022-08-25

I SECTION VIII: PERMANENT STORMWATER CONTROL PLAN A. OFF-SITE ANALYSIS A site reconnaissance was performed by Brian Kalab of Insight Engineering on May 14, 2018 to verify the downstream flow paths and observe any drainage problems downstream of the site. The sky was clear and overcast with a temperature of 77 degrees. The site contains 1.88 Acres. The site is currently vacant with access from Sonrise Christian Center. The remainder of the site exists as lawn and native vegetation. The site contains one drainage basin that that slopes moderately to the south west. Please refer to the downstream analysis map for more details. Per NRCS survey of Snohomish County, the project site contains Alderwood soils that have a hydrologic classification of Type"C". Please refer to the soils map and descriptions attached later in this report for more details. Upstream Analysis Based on the site reconnaissance and the topographic survey of the site, the off-site area entering the site is very minimal. Refer to the Downstream Analysis Map attached in the next page for more details. Downstream Analysis Refer to the Downstream Analysis Maps 1 and 2 attached to the next pages for a visual description of the downstream flow. The runoff from the existing site flows to the south and joins the existing drainage system. The flow continues south east through a 12-in Concrete Pipe for about 240-ft and then continues west for 198 ft to enter a wetland. From the wetland it continues flowing Ithrough the existing drainage system for about 118 ft in south east direction and heads southwest and again southeast and finally crosses Pacific Hwy and finally discharges into Swamp creek. This is where the downstream analysis was concluded. I Insight Engineering Co. -Stormwater Site Plan 12/20/2018 - 17- i