2008-04-15_REVISION - M1980244 (256)

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~1 SMITH WILLIAMS CONSULTANTS, INC. 2. Phase II: A 1-foot-thick layer of bentonite amended SLF overlain by an 80-mil single-sided textured LLDPE geomembrane liner, representing the material used as the composite liner for Phase II. Interface direct shear testing was performed by GeoSyntec Consultants of Atlanta, Georgia using four different normal stress values ranging between 50 and 300 psi imposed on a section of bentonite amended SLF overlain by 80-mil textured LLDPE geomembrane overlain in turn by DCF material. The interface testing for these normal loads were used to define a linear relationship (friction angle and cohesion) between the normal loads calculated in the stability section slices, and the corresponding shear strength. The SLF was compacted to 95 percent of the standard Proctor maximum dry density and at optimum moisture content. Test results were presented to the DBMS by CC&V in a July 8, 1996 letter titled "Cresson Project; Permit M-80-244: Bentonite Addition to SLF -Stability Analysis File". A copy of this information was formally transmitted in a July 15, 19961etter titled "Test Results for Bentonite Amended Soil Liner Fill." An angle of internal friction of 15 degrees and 1,590-psf cohesion were used in the analysis, corresponding to the residual shear strength measured as part of the interface shear strength testing, which is consistent with that submitted previously to CC&V. The • interface shear strength results are presented in Appendix B of this report. 3. Phases III and IV: A 1-foot-thick layer of clay borrow SLF overlain by an 80-mil single-sided textured LLDPE geomembrane liner, representing the material used as the composite liner for Phase III and to be used for Phase IV. Interface direct shear testing was performed by GeoSyntec Consultants of Atlanta; Georgia using various different normal stress values. As part of the clay borrow SLF investigation, interface shear strength testing-was performed for normal loads of 50 psi and 150 psi on two different samples of clay borrow SLF overlain by 100-mil textured HDPE geomembrane overlain in turn by LVSCF. This configuration was tested as it represented the interface between the thickest geomembrane and the smallest gradation of the overlying granular material. The interface testing for these normal - .loads were used to define a linear relationship (friction angle and cohesion) between the normal loads calculated in the stability section slices, and the corresponding shear strength. The SLF was compacted to 95 percent of the standard Proctor maximum dry density at the optimum moisture content. Based on these test results, the interface shear strength that had a friction angle of 18 degrees and a cohesion of 410 psf was considered the critical interface. The interface shear strength test was repeated for • normal loads corresponding to 50 psi, 100 psi, 150 psi, and 300 psi, except that the S:\PROJECTS\1125 CCBV PHASE 5 VLF\H2 - DESIGMAREOUA VLF\VLF PHASE 5 FINAL REPORT V2.DOC 32