202 ALDER ST Geotech Report 2018-01-02 MF Import

, , P�oposeC VieK�Ridge Subsurface Erplorolion, Geologic Hazards. lnfilnation Porentml. Elernentarv Srhoo!Repfacement and Preliminary Geotechnic�!Engrneenng Repan Everz;t, Wa hin ton Project and Sitr Conditiuns ' 4.1 StratiRraphy , Surficinl Topsoil Those exploration borings not located in paved areas generally encountered approximately , 6 inches of grass and topsoil. Topsoil is not suitable for swctural support, and should be stripped from structural areas. Excavated topsoil may be suitable for reuse in landscape areas. , Ezisting Paving ' Existing paving was encountered at one of the boring locatio�s. The asphalt paving was approximately 3 inches thick at the location of EB-7. Existing paving should be removed from below planned building azeas. , Fill , Existing fill was encouutered in two of our explorations to maxunum depths of approximately 10 feet below the existing ground surface. Possible exis�.ing fill was encountered in two additional explorations. It should be noted that some o: the existing fill appears to consist of ' soils derived on-site and are difficult to distinguish from intac. site soils in exploration borings. Typically, such determinations are much easier in open excavations such as those that are made ' at the time of construction. Existing fill is not suitable for structural support without remedial prepazation as described in ' the "Site Preparation" section of this report. Existing fill should be replaced below planned building areas, and should be re-worked under paving. Excavated existing fill material is suitable for reuse in structural fiil applications if it is free of excessive organic material and ' other deleterious materials and is allowed by the project plans and speciCcations. Advance Outr�ash ' Relow the surficial fill where it was present, all of the exploration borings encountered dense sand with few silt and silt stringers interpreted as Vashon advance outwash sediments. ' Advance outwash was deposited at the base of an advaucing glacier, and was subsequendy compacted by the weight of the overlying glacial ice. Advance outwash deposits typically , exhibit gradational stratificatioo, including stringers consisting of silt and/or silry sand. Such stratification has the po[ential to iimit advance outwash sediments from performing wel] as an infilvation receptor. The construction of pit d-�ins, as discussed in this repon, penetrates finer ' strata and substantially improves the ability of advance outwash to serve as an infiltration receptor. Excavated advance outwash sediments are expected to be suitable for reuse in ' Seytember 22, 2010 ASSOC/ATEU EARTH SCIENCES, INC. I BK'G/ib�KE!(X12.SSA2-P�ajecrt110/0�73551KFtWF page 4 � '