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Proposed View Ridge Subsurface Exploration, Geologic Hazards, Infiltration Potential, <br /> Elementary School Replacement and Preliminary Geotechnical Engineering Report <br /> Everett, Washington Project and Site Conditions <br /> 4.1 Stratigraphy <br /> Surficial Topsoil <br /> Those exploration borings not located in paved areas generally encountered approximately <br /> 6 inches of grass and topsoil. Topsoil is not suitable for structural support, and should be <br /> stripped from structural areas. Excavated topsoil may be suitable for reuse in landscape areas. <br /> Existing Paving <br /> Existing paving was encountered at one of the boring locations. The asphalt paving was <br /> approximately 3 inches thick at the location of EB-7. Existing paving should be removed from <br /> below planned building areas. <br /> Fill <br /> Existing fill was encountered in two of our explorations to maximum depths of approximately <br /> 10 feet below the existing ground surface. Possible existing fill was encountered in two <br /> additional explorations. It should be noted that some of the existing fill appears to consist of <br /> soils derived on-site and are difficult to distinguish from intact site soils in exploration borings. <br /> Typically, such determinations are much easier in open excavations such as those that are made <br /> at the time of construction. <br /> Existing fill is not suitable for structural support without remedial preparation as described in <br /> the "Site Preparation" section of this report. Existing fill should be replaced below planned <br /> building areas, and should be re-worked under paving. Excavated existing fill material is <br /> suitable for reuse in structural fill applications if it is free of excessive organic material and <br /> other deleterious materials and is allowed by the project plans and specifications. <br /> Advance Outwash <br /> Below the surficial fill where it was present, all of the exploration borings encountered dense <br /> sand with few silt and silt stringers interpreted as Vashon advance outwash sediments. <br /> Advance outwash was deposited at the base of an advancing glacier, and was subsequently <br /> compacted by the weight of the overlying glacial ice. Advance outwash deposits typically <br /> exhibit gradational stratification, including stringers consisting of silt and/or silty sand. Such <br /> stratification has the potential to limit advance outwash sediments from performing well as an <br /> infiltration receptor. The construction of pit drains, as discussed in this report, penetrates finer <br /> strata and substantially improves the ability of advance outwash to serve as an infiltration <br /> receptor. Excavated advance outwash sediments are expected to be suitable for reuse in <br /> September 22, 2010 ASSOCIATED EARTH SCIENCES, INC. <br /> BWG/tb-KE100255r12-Prof ects120100255IKEIWP Page 4 <br />