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• Attempts were made To measure the level of free groundwater in all <br />borings. Water was found only in boring TH-7 at a depth of 21 feet. No water was <br />detected in boring TH-I at the base of the proposed fill. <br />Representative samples of the near surface soil and the bedrock were <br />returned to our laboratory for testing. The results of consolidation tests on <br />samples of the valley bottom clays are presented on Figs. B-2 Through B-4. A n <br />undrained triaxial test with pore pressure measurements was performed on <br />samples of the clay (Fig. B-I) and indicated the clay material exhibited cohesion <br />on the order of 500 psf with an angle of internal friction (phi) of about 15 <br />degrees. Unconfined compressive strengths of samples of stiff clay were on the <br />order of 6,000 psf. Samples of the sedimentary bedrock claystone/siltstone were <br />also tested using unconfined compression tests. These tests indicated cohesion in <br />• the range of 3,000 to 15,000 psf. For stability analysis, we assumed a shear <br />strength angle of internal friction of 15° and cohesion of 500 psf for the clays. <br />The bedrock was assumed to have 5,000 psf cohesion and zero friction. <br />STABILITY ANALYSIS <br />Colowyo Coal Company personnel identified the approximate area of the <br />proposed spoil and indicated slopes would be 3:1 (horizontal to vertical). ~.Ne <br />anticipated there will be intermediate terraces approximately 20 To 30 feet wide <br />at 50 to 100 feel height intervals To control surface erosion and provide access. <br /> <br />