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Subsurface Exploration, Geologic Hazard, and <br /> Snohomish County YMCA Geotechnical Engineering Report <br /> Everett, Washington Project and Site Conditions <br /> approximately 76 feet in MW-1. The advance outwash deposits consisted of varying gradations <br /> of fine, medium, and coarse sand with trace to some silt and trace to some gravel, and were <br /> stratified, with some lenses with higher silt or gravel content present. AESI generally observed <br /> that fewer low-permeability stratified layers were present at greater depth within the advance <br /> outwash sediments, and that sand grain size generally increased with depth. <br /> Advance outwash is suitable for structural support when properly prepared. Excavated advance <br /> outwash material is suitable for use in structural fill applications if suitable moisture conditions <br /> are achieved prior to compaction, and if such reuse is specifically allowed by project plans and <br /> specifications. <br /> 4.2 Geologic Mapping <br /> Review of a regional geologic map (J.P. Minard, 1985, Draft Geologic Map of the Everett <br /> 7.5-Minute Quadrangle, Washington, U.S. Geological Survey (USGS), Miscellaneous Field <br /> Studies Map MF-1748, scale 1:24,000) indicates that the subject site lies near the contact <br /> between two Vashon-age lodgement till and advance outwash sediments. Our interpretation <br /> of the sediments encountered at the subject site is in general agreement with the regional <br /> geologic map. <br /> 4.3 Hydrology <br /> No groundwater was present on the surface of the subject site at the time of our explorations. <br /> AESI observed minor isolated seepage in IT-2 prior to beginning infiltration testing from above a <br /> silty interbed. We interpret this seepage to be perched water. We also observed minor <br /> post-infiltration test seepage from IT-1, IT-2, and IT-4 below the test base, occurring in <br /> conjunction with silty interbeds. <br /> AESI observed groundwater at approximately 60 feet below ground surface in advance outwash <br /> sediments in MW-1 during drilling, and after well development. Based on an approximate <br /> top-of-casing elevation of 301 feet, this corresponds with a groundwater elevation of <br /> approximately 241 feet in the advance outwash aquifer beneath the subject site. This water <br /> level elevation is consistent with regional water levels in the Vashon advance aquifer presented <br /> in Thomas et al. (1995). Groundwater conditions should be expected to vary in response to <br /> changes in precipitation, on-and off-site land usage, and other factors. <br /> February 26,2018 ASSOCIATED EARTH SCIENCES,INC. <br /> AWR/ms-170671E001-2-Projects‘201706711KE\WP Page 6 <br />