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• <br />Laboratory Investigation <br />Samples obtained from the exploratory test holes were examined and classified in the laboratory by the project <br />manager for NWCC. Laboratory testing included standard property tests, such as natural moisture contents, <br />dry unit weights, grain size analyses and liquid and plastic limits. Unconfined-compressive strength tests were <br />also conducted on samples to correlate the shear strength of the overburden soils, fill materials and bedrock <br />materials. All of the other laboratory test results are summarized in the attached Table 1. The laboratory <br />testing was conducted in general accordance with applicable ASTM and AASHTO specifications. <br />Subsurface/Groundwater Conditions <br />The subsurface conditions encountered in the test holes and test pits advanced across the slide area and to the <br />east of the slide were variable and generally consisted of a layer of man-made fill materials overlying natural <br />clays and/or weathered claystone materials that were underlain by claystone bedrock that extended to the <br />maximum depth investigated in each of the test holes, except Test Hole 10. Graphic logs of the test holes are <br />shown in Figures #3 and #4, and the graphic logs of the test pits are shown in Figure #5. The Legend and <br />Notes associated with the test hole and test pit logs are presented in Figures #6 and #7, respectively. More <br />detailed descriptions of the subsurface conditions encountered at the site are provided below. <br />A layer of man-made fill materials was encountered at the ground surface in all of the test holes and pits <br />advanced at this site. The depth and consistency of the fill materials was highly variable. The fill materials <br />were encountered to depths ranging from 2 to 19 feet beneath the existing ground surface. The fill materials <br />were highly variable in consistency and primarily consisted of clays that were slightly sandy to sandy with <br />bedrock fragments ranging from gravel to boulder in size, low to highly plastic, loose to stiff, moist to wet and <br />light brown to gray in color. Samples of the fill materials generally classified as CL to CL-CH to CH-CL soils <br />in accordance with the Unified Soil Classification System. <br />A layer of natural clays was encountered below the fill materials in seven of the test holes. The clay layers <br />generally ranged from 2 to 10 feet in thickness. The clays were nil to slightly sandy with occasional bedrock <br />fragments, moderately to highly plastic, stiff to very stiff, moist to very moist and brown to gray in color. <br />Samples of the clays generally classified as CL to CL-CH soils in accordance with the Unified Soil <br />. Classification System. <br />Job Number: 08-8099 NWCC, Inc. Page 5