2400 33RD ST GEOTECHNICAL INVESTIGATION 2018-01-02 MF Import

sc 130 Milbor-Pita &S r W_ 4.2.2.1 Fill The areas of fill are consistent with the history of the site. The 1902 Sanborn Fire Map shows that this area wa5z heing used by the Great Northern RrJlroad line, so the fill must predate that occupation. The 1914 Sanborn map shows an asphalt plant on the east side of Smith between 33`d and 341h Streets, indicating a possible source of some of the fill. The metal debris found in MP-2 at a depth of 23 feet could be from the lower end of a piling installed for either the railroad or the asphalt plant. It is an indication that perhaps there are more pilings that could be encountered during site grading. The fill materials appear to consist of silty sand with organic debris, construction debris (brick), and asphalt pieces. The depth of fill materials is consistently 2.5 to 3 feet north of 32"d Street, east of Smith. South of 32"d and east of Smith the fill is less consistent. The area below the proposed building appears to have. 2.5 feet of fill under the northern end (just west of the existing ` d mill), and , feet toward the southern end (between tie mill and O'Day P .,roleum, east of the railroad spur). The area south of the midpoint between 32"d and 33`d, east of Smith appear to have 3 to 5 feet of fill west of the rail spur, and no fill east of it. The fill materials are loose to very loose, and usually wet. 4.2.2.2 Silty Clay The unit uppermost below the till is a silty clay or clayey silt; laboratory test results presented in Appendix C indicate that the classification is on the border between the two types of materials. It is sediment from glacial lakes, as described above. The unit is present across the site, at a depth of approximately 2.5 feet and extends to a depth of approximately 20 feet. Appendix D presents consolidation test results of this material. The two tests performed on samples at the same depth, but from eifferent borings, had almost identical results. The third and test result also had similar results but for a material that was deeper and therefore had more overburden weigN upon it in its natural condition. The results show that this material is elastic but also has 'set', which means permanent deformation. Therefore, consolidation will occur and cyclic loadings, if allowed to occur directly on this material, could compress it in localized areas. The design should account for this condition. 4.2.2.3 Silty Sand — Recessional Outwash In some borings there is a 1 to 2 foot thick layer of silty sand between the clay/silt and till. It usually contains water, and probably is a recessional outwash. 4.2.2.4 Till At a depth of 18 to 20 feet there is a layer of silty gravelly sand, a glacial "lodgement" till. It is the material deposited directly under the glacier, and is highly compacted by the weight of the glacier. It is extremely dense, and almost G+otechnical, Tunnel and lutvimmmW FngUwm 3080 125° Ave NE Phase (423) 869-5778 13,11ewe, WA 98005 Page Fax (425)861-0677