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4D <br />cQ H <br />9 H !n <br />y 0 <br />tC f] <br />H xl <br />1-3 <br />MH41 <br />iA H <br />OE <br />HU <br />OH <br />tZI O <br />0. t� <br />t HZ <br />t" H H <br />0 rn <br />0 U C/3 <br />Fa � <br />Z H rO <br />H O m <br />1.1.1.6 Soil and Substrate Goal <br />The goal is to have soil that will sustain wetland plants and help maintain wetland <br />hydrology. This will be accomplished in part by selecting areas where the native soils have the <br />right properties or by importing soils from elsewhere on the Boeing Everett property. A <br />combination of specified 'fines' content and compaction will be used to achieve the needed <br />restriction of permeability. <br />1.1.2 Report of Site Investigations on Soils and Hydrology <br />This report discusses the preliminary findings on soils and hydrology of the wetland <br />compensation area for the Boeing Everett Employee Activity Center. The location of the <br />proposed compensating wetlands will be in the headland and within the western -most gully <br />(tributary drainage to Japanese Gulch) within site boundaries, as shown on Plate 1. <br />The assessment of site conditions, conclusions and recommendations are based on soil <br />borings, field observations and logging of soils, review of previous site work and regional <br />information, and laboratory analysis of soil samples. <br />j ��► There is convenient access to the proposed wetland compensation areas through graded <br />dirt roads. Two gullies lie in a north/south trend on the western portion of the site; one gully on <br />the northern border trends southerly. The gullies extend 500 to 1,000 ft, changing in elevation <br />from 410 ft to 550 ft. Surrounding ridges rise steeply and stand at approximately 600 ft in <br />�0 elevation. <br />4 <br />1.1.2.1 Geologic and Soil Conditions <br />®® Review of geologic information for the Everett area indicates that glacial till, typically <br />a poorly sorted, low permeability mixture of clay, silt, sand and gravel, overlies the much more <br />permeable Esperance Sand Unit. The top of the Esperance Sand beneath the site, based on <br />inference from the regional information, probably lies between elevations 400 and 500 feet. <br />The geologic reconnaissance information from the USGS for the western part of <br />6 Snohomish County shows outcrops of Esperance Sand in both Japanese Gulch and Powder Mill <br />Gulch , west and east of the site, respectively. The Esperance Sand is an advance outwash deposit <br />consisting of sand and gravel, up to 400 or 500 feet thick. It lies stratigraphically below the till <br />member. Site elevations are 410 to 550 feet, in close proximity to the Esperance Sand. <br />o1+� Regional soils in the vicinity of the site have been mapped as Alderwood gravelly sandy <br />loam. The Alderwood soils are moderately deep to very deep, moderately -well drained to <br />excessively drained, and nearly level to very steep. These soils typically occur on till plains, <br />terraces, and outwash plains. The Alderwood soils are considered to be limited for use at <br />embankments, dikes, or levees due to seepage potential. (Debose and Kygman Soil Survey of <br />Snohomish County Area, Washington.) <br />3 <br />DAMES 9 MOORE <br />