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Golder Associates Inc. <br />200 Union Boulevord. Suite 500 <br />lOlcewood. CO USA 80228 <br />Telephone (303) 980.0540 <br />Fax (303)985-2080 <br />July 15, 1996 <br />Cripple Creek & Victor Gold Mining Company <br />2755 State Highway 67 <br />Victor, CO 80860 <br /> <br />Our Ref: 963-2027.008 <br />RE: -TEST RESULTS FOR BE~I'I'ON'ITE A~MEi dDED SOIL LIti'ER FILL <br />Dear Ron; <br />As per a request from the Cripple Creek & Victor Gold Mining Company (CC&V), Golder <br />Associates Inc. (Golder) has evaluated the impact of the addition of 2~ bentonite to the material <br />proposed for use as Soil Liner Fill during 1996 Phase II construction activities. Golder would like <br />to take this opportunity to present the test results from the interface shear strength, swell/settlement <br />and Cation Exchange testing of the samples to CC&V. <br />Index testing, such as grain size distribution and Atterber; limiu, were performed on the material <br />~. prior to bentonite amending to confirm that the material met the specified sradacion. Results from <br />these tests are presented in Attachment A. <br />Interface shear strength testing was performed in general accordance with the American Society for <br />Tasting and Materials (ASTM) Standard Test Tvletaod DS321, "Determining the Coeffcient of Soil <br />and Georynthetic or Geosynrhetic and Georynthedc Friction by the Direct Shear Method". Tesu <br />were conducted at normal stresses ranging frown ~0 psi to 300 psi in a direct shear device <br />containing an upper and lower shear box. When samples were subjected to normal loads of 50 psi <br />to 150 psi, the upper shear box measured 12 inches by 12 inches in plan and 3 inches in depth. <br />The lower shear box measured 12 inches by 14 inches in plan and 3 inches in depth. When tests <br />were conducted at a normal stress of 300 psi, a smaller upper shear box was used which measured <br />6 inches by 6 inches in plan and 3 inches in depth. <br />Interface shear strength testing, presented in Atcacivneat B, was performed for normal loads of 50 <br />psi, 100 psi, 150 psi and 300 psi for the Cresson Ore Drain Cover Fill ! 80 mil textured LLDPE <br />geomembrane /bentonite amended Soil Liner Fili at optimum water content. Test results yielded <br />residual shear stzengths chat varied from a cohesion of 2,300 psf and friction angle of 15 degrees, <br />and a cohesion of 1,590 psf and friction angle 15 degrees. The failure plane was noted to occur <br />between the Soil Liner Fill and the 80 mil textured LLDPE geomembrane. An interface shear <br />strength of 15 degrees and 1,600 psf was incorporated in the critical stability section, with results <br />presented in Attachment C. These values meet the minimum strength criteria required for the <br />Phase II Pad, as originally identified in a January 9, 1996 letter from Golder to CC&V entitled <br />"Interface Shear Strength Test Results for Phase 11 Cresson Project°. Golder then performed an <br />~, interface shear strength test at 100 psi and 300 psi in which the Soil Litter Fill was allowed to <br />~. }J consolidate. When these two data points were plotted, the residual cohesion increased to 2,750 psf <br />and the friction angle increased to I7 degrees. Tlierefore, the Best results indicate that the material <br />~. will meet the minimum interface shear strength requirements for the project. <br />OFFICES IN AUSTRALIA. CANADA. GERMANY, hUNGA.f1Y. ITPLY. SWE.riEN. UNITED KINGDOM. UNITED SPATES <br />I~ _ _ - - - <br />