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• J.E. Stover & Associates <br />Terracon Project No. 65995058 <br />June 3, 1999 <br />Groundwater was not indicated in any of the test borings drilled by Maxim at the location of the <br />proposed ponds. <br />The source of materials to construct fill sections at the coal stockpile pad and the <br />sedimentation pond will be derived from on-site sources. For purposes of the stability <br />analyses, the use of clay materials, compacted to specifications outlined in the geotechnical <br />reports for the project, have been assumed for construction of the proposed fill sections. <br />Maxim presents shear strength data for the on-site clay soils based upon a series of <br />unconfined compression tests, and unconsolidated-undrained (UU) triaxial shear tests. The <br />unconfined compression tests are essentially UU tests with no confining pressure. Unconfined <br />compression strength reported by Maxim for the clay soils varied from 900 to 29,000 psf, with <br />an average of 12,000 psf for 12 tests. UU triaxial testing completed by Maxim indicated <br />internal friction angles of 4 to 23 degrees and cohesion values of 2200 to 4350 psf. <br />Maxim has also completed UU triaxial shear tests on samples of compacted clay soils that will <br />• be used in proposed fill sections of the project. Those test results indicated angles of internal <br />friction of 28 to 32 degrees with cohesion of 1,600 to 2,900 psf. <br />Lambert and Associates conducted direct shear tests on samples of clay soils from the site. <br />These tests have been characterized as consolidated-drained (CD) tests. Those test results <br />indicated drained angles of internal friction of 26 to 30 degrees with cohesion of 250 to 375 <br />psf. Six of the reported seven (7) tests conducted by Lambert indicated an internal friction of <br />30 degrees. <br />Shear strength parameters used for the stability analyses for the structures have been based <br />upon the laboratory data discussed above as outlined in the Maxim and Lambert reports. We <br />have generally used the more conservative shear strength parameters presented in those <br />reports (assuming a worst case analysis based upon available data). <br />In summary, the drained and undrained shear strength parameters used for the three different <br />soils types included in the stability models are as follows: <br />• <br />5 <br />