Laserfiche WebLink
of the State of Colorado (Rule 4.05.9(3), CRS 37-87-105) nor MSHA (Rule 4.05.9(4), <br />CFR.77.216(a)). <br />The western pond embankment is judged to be Class A, with the eastern <br />pond Class B according to United States Department of AgriculturefSoil <br />Conservation Service (USDAISCS) TR-60 criteria (Reference 11). We believe our <br />level of investigation and design meets the requirements of CDMG Rule 4.05.9(6) <br />and USDAISCS TR-60. <br />Eneineerine Properties <br />The strength and density properties of the overburden soils and <br />embankment fill were evaluated as follows. <br />The overburden soils typically consisted ofa silty to clayey sand with gravel. <br />• Gradation testing showed about 20 to 40 percent low plasticity fines, with 30 to 40 <br />percent sand and 20 to 30 percent gravel (Figs. A-3 through A-7 and Table 1). Direct <br />sshear tests were performed on both Intact liner samples (Fig. A-8) and remolded <br />samples (Fig. A-9). A consolidated-undrained (CU) test with pore pressure <br />measurements was performed on a remolded sample (Fig. A-10). <br />The direct shear tests indicated relatively high friction angles (36 to 44 <br />degrees) and significant cohesion values (500 to 1,700 psft, The CU test indicated <br />lower strength values which probably reflect the strength of the finer matrix <br />materials. Atotal stress strength envelope of 14 degrees, 1,000 psf cohesion and <br />effective stress envelope of 21 degrees, 880 psf cohesion were inferred from this <br />test (Fig. A-10). <br />We also reviewed previous CTL~Thompson, Inc, investigations at the site. <br />A similar clayey sand soil from the area ofthe proposed Lower Wilson Pit (Reference <br />10) showed a friction angle of 23 degrees, cohesion of 300 psf in direct shear <br />KENNECOTT ENERGY <br />COLOWYO COAL COMPANY-SOUTH TAYLOR SEDIMENTATION POND <br />CTI~T JOB N0. ~b,b6~ 5 <br />Exh. 7-20F-9 Revision Date: 1/05/07 <br />Revision No.: PR-02 <br />