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-4- <br />• <br />weathering of the underlying sedimentary bedrock formations. Sedimen- <br />tary bedrock consisting of claystones and sandstones occur at very shal- <br />low depths. The thickness of the surface soil veneer ranges from 5 to <br />a maximum of about 10 feet. The near-surface soils are very stiff to <br />hard clays with unconfined compressive strengths in the range of 6,000 <br />to 10,000 psf. The underlying sedimentary bedrock has very high support <br />characteristics. Unconfined compressive strength tests on some of the <br />softer bedrock samples indicated strengths in the range of 10,000 to <br />20,000 psf. Where cuts are required in the ridge line, we anticipate <br />encountering materials which can be excavated by ripping to depths on <br />the order of 15 feet. Sedimentary rocks located below a depth of about <br />15 feet may require blasting in order to facilitate removal from cuts. <br />• The near-surface residual clays and the underlying sedimentary formations <br />have relatively high strength. For analysis purposes we used a value <br />of 15 degrees for the angle of internal friction and a cohesion of 5,000 <br />psf for the lower sedimentary rock. Previous investigations by our <br />firm and others have indicated that the portions of rock which require <br />blasting will stand on an average slope between 60 degrees and 75 degrees <br />with an adequate factor of safety. The factor of safety for a 60 degree <br />slope is on the order of 2. 3. The overall mine area was investigated <br />and reported by Kenneth C. Ko and Associates in their report No. 1002 <br />dated March, 1977 entitled "Preliminary Design of Highwall Slopes", <br />Energy Fuels Corporation, Steamboat Springs, Colorado. Additional detail- <br />ed studies were conducted by CTL/Thompson, Inc. and reported under our <br />• Job No. 5029, dated January 29, 1979, "Analysis of High Wall Stability, <br />Energy Fuels Mine No. 1, Pit 8050, Steamboat Springs, Colorado" which <br />