10200 25TH AVE SE Geotech Report 2018-01-02 MF Import

( '; � Proposed Modernilation and Addirions to Subsurjace Explorarion, Geolvgic Hazards. 6'iserthower Middle Schoo! and Geotechnica!Engineering Repon Ereretr, Washington Pro'ecr and Site Corditrons foot depth intervals. The exploration borings were continuously observed and logged by a geotechnical engineer from our firm. The exploration logs presented in the Appendix are based on the field logs, drilling actio:�, and inspection of the samples secured. Disturbed but representative samples were obtained by using the Standard Penetration Test procedure in accordance with ASTM:D 1586. This test and sampling method consists of driving a ssandard 2-inch outside-diameter, split-barrel sampler a distance of 18 inches into the soil with o 140-pound haznmer free-falling a distance of 30 inches. The number of blows for each 6-inch interval is recorded and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance ("N") or blow count. If a total of 50 is recorded within one 6-inch interval, the blow count is recorded as the number of blows for the corresponding number of inr.hes of penetration. The resistance, or N-value, provides a measure of the relative densiry of granular soils or the relative consistency of cohesive soils; these values are plotted on the attached exploration boring logs. i The samples obtained from the split-barrel sampler were classified in the field and representative portions placed in watertight containers. The samples were then transparted ro our laboratory for further visual classification and laboratory testing, as necessary. 4.0 SUBSURFACE CONDITIONS Subsurface conditions at the projec[ site were inferred &om the field explorations accomplished for this study and visual reconnaissance of the site. As shown on the field soil logs, the exploration borings generally encountered fill overlying glacially consolidated "till" soils. The depth to the underlying dense till varied from approximately 1 to 12 feet. Sub�urface conditions at the project site were inferred from the field explorations accomplished for this study and visual reconnaissance of the site. As shown on the field soil logs beneath the fill/topsoil, exploration borings generally encountered a mixture of silt, fine to coarse sand and rounded gravel interpreted as till deposits. This interpretation is consistent with the geology mapped in the site area as shown on the U.S. Geological Survey (USGS) publication: Preliminary Geologic Mnp of S«rficinl Deposits in the Seattle 30' X 60" Quadrangle, by Yount, Minard, and Dembroff (1993). The following section presents more detailed subsurface information beginning from the youngest (shallowest) to oldest (deepest) sediment types. lanunrv 33, s'ODd ASSOCIdTED E.1RTN SC/E,VCES, LVC. �` .517(d-KEOJ739d3-Pro�rcuCWl7JyiXfi��'Y- R':K Page 4 1 71 �y