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1 <br /> r <br /> PRELIMINARY CONDITIONS SUMMARY <br /> The site is in the Penny Creek Drainage Subbasin(North Creek Basin),and all drainage flows to <br /> an unnamed creek approximately 500 feet west of the site,which conveys runoff south to Ruggs <br /> Lake. According to the 2002 Snohomish County Drainage Needs Report,the unnamed creek is <br /> not identified as a fish-bearing stream. The site is divided into subbasins to describe the different <br /> portions of the site. See the Existing Drainage Basin Map in Appendix A. Subbasin A drains as <br /> sheet flow west to the Snohomish County storm drain system in 27th Avenue SE,then to the <br /> unnamed creek. Subbasin B 1 drains as sheet flow to a conventional pipe and catch basin system <br /> that flows to the southwest corner of the site and connects by an 18-inch pipe to the county storm <br /> drain system. The county storm drain system then discharges to the unnamed creek. <br /> Subbasin B2 is an underdrained athletic field that connects to the storm drain system in <br /> Subbasin B1. Subbasin C drains as sheet flow to the county storm drain system in 110th Street <br /> SE. There is currently no stormwater detention or water quality facility on the site. <br /> Approximately 0.2 acre of off-site area drains onto the northeast portion of the site from the <br /> north. This off-site area consists of the landscaped areas along the rear of the existing lots of the <br /> Plat of Cascade Highlands. This off-site drainage is captured by the underdrain system in <br /> Subbasin B2. <br /> DOWNSTREAM ANALYSIS <br /> The majority of the site runoff discharges from the southwest portion of the site through an <br /> existing catch basin. The downstream drainage conveyance system is detailed on the <br /> 1 Downstream Inventory Map in Appendix A. The majority of the existing stream channel was <br /> not observed because it flows through private drainage tracts that are not accessible. The <br /> unnamed stream eventually discharges to Ruggs Lake,approximately 5,600 feet to the south. <br /> ' The Drainage Needs Report(DNR)—North Creek Basin,prepared by Snohomish County,has <br /> documented flooding problems near 28th Drive SE and 110th Street SE. This area is southeast of <br /> the subject property and a 0.12-acre portion of the existing site is tributary to this area. The <br /> project will not increase existing flows to this area. According to the DNR,there are no <br /> documented flooding problems along the subject stream channel. <br /> DESIGN CRITERIA <br /> • The Stormwater Management Manual for Western Washington (SMMWW), 1992 <br /> • City of Everett Stormwater Management Manual, 1997 <br /> • City of Everett(COE), Title 14, Chapter 14.28—Surface and Storm Drainage <br /> Stormwater Conveyance System <br /> Convey the peak 25-year storm event. <br /> ' James Monroe Elementary School 3 Reid iddleton <br /> Drainage Report <br /> 1 <br />