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. � - c <br /> � NELSON-COUVRETTE & ASSOCIATES, INC. <br /> CONSULTINO GEOTECHNICAL ENGINEERS, GEOLOGISTS <br /> AND ENVIRONMENiAL SCIENTIS7S <br /> 1731 7-7 35M Avenua NE,A-500 SnWwmish Couny(425)337-1689 <br /> Woodinville,WA 98072 WenateheNChWn(509)784•2756 <br /> (425)486-1669• Fax 481-2510 �•^��'C0w'rom•C0R1 <br /> May 16,2000 • <br /> Ms.Kaffiy Tredway <br /> The Tredway Corporation <br /> P.O.Box 3014 <br /> Everett,Washington 98203 <br /> C�nsultation L.etter <br /> Flanned Short Plat Road and Detentiou System <br /> Everett,Washington <br /> NCA File No.2594B00 <br /> Dear Ms.Tredway: <br /> INTRODUCTION <br /> This letter prosents our recortunendations for the design and installation of the detention pipe struchues <br /> at your short plat located at 5701 South First Street in Everett,Washington. We have proviously written <br /> a geotechnical report,dated June 2, 1999,forthis site. The site wac explorod by excavating test piu with <br /> a backhce. After our explorations were completed, it was decided to move the road to the east side of the <br /> site neu the edge of a wetland. This is east of the test pit locations. The new plans include 4 and 6- <br /> foot-diameter detention pipes below the road in this area. You have requested that we explore this area <br /> and provide recommendations for design and construction of the detention pipes and roadway. <br /> Specifically,the county has asked that the bearing capacity of lazge vac-wcks be addressed. <br /> The new road will be on the order of 18 to 20 feet wide, as measurod from the site plan provided. <br /> Underlying the road, near centerline, will be 60 feet of 4foot-diemeter ADS pipe. There will La on the <br /> order of 2 feet of cover over the pipe. Mother 60 feet of 6-foot-diameter ADS pipe will be used for <br /> water quality. There will be about 5 feet of cover over this pipe. <br /> �S <br />