1001 39TH ST 2016-01-01 MF Import

i _ DAVID L. NELSON AND ASSOCIATES, INC. Consulting Enginecring Geology ' November 27, 1991 Project No. 10591 Page 3 The surficial soils encountered across the site consist of areas I of native soils and fill. Beneath the surface fill, the r�ative soils consist of about 1 . 5 to 3 feet of brown loose silty sand � w:th roots. Covering the root zone, is about 0 . 5 to 4 feet of f.ill, and consist generally of black, brown and grey, very loose to medium dense, mixed silty sand with gravel, organics and some debris . The fill is relati�•ely thin along the upslope relatively I level portion, becomes thicker along the "top of slope" area, and thins again downslope. The fill does not appear exist below the I apprcximate areas of test pits 1 , 2 and 3 . It appears that this ' I fill was placed by pushing the material over the top of slope . HYDROLOGIC CONDITIONS I Ground water was not encountered within any uf the test pits I performed around the site. We found some indications of seasonal seepage and wet conditions within the mc�re permeable soils I perched above the finer grained Whidbey Formation. This perched ground water is expected to flow down gradient to the north and west. This type of ground water condition is common for upland areas underlain by relatively impermeable soils, and tends to be somewhat seasonal . We expect this condition to decline markedly during the drier summer months. No seepage was observed on the steep slope ar��as to the north and west, within or below the proposed residence area. We did observe wet to saturated conditions within the base of the drainage swale to the north. SENSITIVE 11REA 1'sVALUATION The subject site evaluated for sensitive area evaluation, as recommended in the new ordinance. Of the potential reasons for classification as environmental].y sensitive (environmentally sensitive characteristics) , the following could occur on site; unstable soils hazard areas, landsli.de i.uzard areas, seismic hazard areas, sprin��s, ground water seepage, and steep slopes associated or in conjunction with one or more of the environmentally sensitive area elements . We will discuss these potential elements be].ow. Seismic Hazard The Puget Sound region is classified as a zone 3 by the Uniform Building Code. Seismic considerations for this type of site include liquefaction poteatial and attenuation of ground motions by soft soil deposits. Typic:ally, seismic hazards are highest for thick alluvial (organic zind/or normally consolidated) soils. The liquefaction potential is highest for l�ose sand and silty sand deposits with a high ground water table. The thickness of the sand deposit should be considered, as liquefaction is /� s�ec=.r.m.r.�ws�a-=�..a.....�..... . ... .- . _ .._.-- :..- .- .�.-.__— . _. .. . e "10�.. __. ._ .<a�L_ " ._ ., . __. . _ '-.