1304 80TH ST SW EVERETT SCHOOL DISTRICT 2018-01-02 MF Import

Subsurface Ecploration and Everett Bits Facility Geotechnical Engineering Report Frerett Washington Project and Site Conditions that new paving not be supported on existing fill soils unless they are in a medium dense condition, do not contain organics, and the upper 2 feet can be recompacted as presented subsequently in this report. Recent Peat and Lacustrine Deposits Below the fill in exploration borings EB-1, EB-9, and GB-11, thin layers of peat and lacustrine sand were encountered. Our previous explorations also documented similar conditions in exploration boring EB-1. The peat consisted of fibrous organic material containing few amounts of silt, clay, and fine sand. The lacustrine deposits generally consisted of loose, fine to medium sand with little organics and varying amounts of silt. The peat and lacustrine deposits were deposited in a shallow lake or kettle created by a low spot in the underlying Vashon lodgement till that trapped surface water. Neither the peat nor the lacustrine sand is considered suitable for direct support of paving sections. Lodgement Till Vashon lodgement till was encountered in all explorations completed for this study. The lodgement till generally consisted of silty, fine to coarse sand containing varying amounts of gravel and scattered cobbles. The lodgement till was deposited at the base of the Vashon age glacial ice sheet and was subsequently overridden by several thousand feet of ice. Consequently, these materials are dense to very dense with depth, possess high strength, low compressibility characteristics, and are relatively impermeable. The lodgement till is suitable for pavement section support. The lodgement till has a large proportion of fine-grained material making it susceptible io disturbance when wet. 4.2 Hydrology Ground water was not encountered in our exploration borings. However, limited amounts of perched ground water are anticipated above Ste till with heavier flows to be expected during the winter/spring months. Perched ground water occurs when surface water infiltrates down through relatively permeable soils, such as the fill or the weathered portions of the till, and becomes trapped or "perched" above a comparatively impermeable barrier, such as the lodgement till. This infiltration can occur at great distances from the area where the ground water is encountered, it should be noted that fluctuations in the level of the ground water may occur due to the time of the year, on- and off-site usage such as irrigation, and variations in rainfall. The quantity and duration of flow from excavatio is made into zones of perched ground water will vary depending on season, topography, and soil grain size. November 28, 2I05 ASSn[7ATFD hARM Sr7EN(TS, INC. EGdd-E'EUTAn2B2•ftjedsI2WJW21KFI%r Page 4