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N G� <br />Main 011ice <br />17311 - 135' Avenue NE, A-500 <br />Woodinville. WA 98072 <br />(425) 486.1669 FAX (425) 481-2510 <br />(425) 337-1669 Snohomish County <br />NELSON GEOTECHNICAL <br />ASSOCIATES, INC. <br />GEOTECHNICAL ENGINEERS & GEOLOGISTS <br />Engineering Geology Branch <br />437 East Penny Road <br />Wenatchee, WA 98801 <br />(509) 665 7696 FAX (509) 665 7692 <br />MEMO It AND UM <br />DATE: <br />July 24, 2008 <br />TO: <br />Chris Covington — Structural Design Associates <br />CC: <br />Mary Pcars/Pamcla Lescsne— Habitat for Humanity <br />PROM: <br />Michael I). Rundquist, PE <br />Bala Dodoye-Alali ' <br />RE: <br />Habitat for Humanity <br />Mulligan Mohr Projcct <br />Everett, Washington <br />NGA Pile No. 793408 <br />We have been requested by to provide design information for the daylight basement retaining wall along <br />the northern side of the planned residence located at 6624 Broadway in Everett, Washington. We have <br />previously visited the site to provide our opinion on the existing excavation wall on this property. <br />The subgrade soil exposed in the excavation consists of dense, brown -gray to gray, fine to course sand <br />with silt and gravel. The cut is approximately 9 to I I feet in height. The upper portion of the cut <br />consisted of two inches of asphalt, underlain by fill material which includes a row of black car tires <br />approximately four to six feet below the surface. The tires were underlain by approximately five feet of <br />medium dense to dense, orange -brown grading to brown -gray, fine to coarse sand with silt and gravel, <br />interpreted to be native soil. <br />The residence foundations should be placed on medium dense or better native soils, or be supported on <br />structural fill or rock spalls extending to those soils. Based on our observations, medium dense to dense <br />soils were being exposed in the bottom of the excavation. If undocumented fill or less dense soils are <br />encountered at footing bearing elevation, the subgrade should be over -excavated to expose suitable <br />bearing soil. The over -excavation may be filled with structural fill, or the footing may be extended down <br />to the competent native soils. If footings are supported on structural fill, the fill zone should extend <br />