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As-Built CQA Report for the Construction of Area 2A at the Foothill Sanitary Landfill <br /> San Joaquin County,California <br /> • Base Liner <br /> • The post-peak strength for Foundation Layer/GCL interface (Test Series 1) at <br /> normal stresses of 6,000 psf and above (8,000 and 12,000 psf) did not meet the <br /> specified interface strength values and showed GCL internal failure. <br /> • The post-peak strength for GCL/HDPE geomembrane interface (Test Series 2) met <br /> the specification requirements at each of the 5 normal stress points. <br /> • For each of the 5 normal stresses, the peak strengths for Test Series 2 <br /> (GCL/geomembrane interface) were lower than the corresponding peak values for <br /> Test Series 1 (Foundation Layer/GCL interface). This would suggest that, in the <br /> base composite liner system, the GCL/geomembrane (and not the Foundation <br /> Layer/GCL) interface is the weakest interface and, therefore, the total liner system <br /> strengths were in conformance with the Specification requirements. <br /> • To further confirm the weakest interface, multi-layer (sandwich) interface tests <br /> were performed upon direction and approval by the County. Sandwich interface <br /> tests had been performed and used for previous Module 1 liner for the Foothill <br /> Landfill and also for the North County Landfill Area 4 and 5 composite Liners. <br /> • The tests results for sandwich tests (Test Series 4) confirmed that the specified <br /> post-peak strengths were met at all 5 normal stress points and that the sliding <br /> occurred on the GCL/geomembrane interface. <br /> • Side Slope Liner <br /> • The post-peak strengths for the HDPE geomembrane/geocomposite interface for <br /> the side slope liner (Test Series 3) met the minimum specified values at normal <br /> stresses of 6,000, 8,000 and 12,000 psf,but were slightly below the specified values <br /> at normal stresses of 1,000 and 4,000 psf. <br /> • Similar results were also confirmed for sandwich tests for side slope liner (Test <br /> Series 5). <br /> • Geosyntec evaluated the test results and confirmed that these slightly lower post- <br /> peak strengths at 1,000 and 4,000 psf normal stresses had no impact on the <br /> stability analysis. This confirmation is documented in their Construction <br /> Memorandum#3 included in Appendix C.2a. <br /> Complete details of the interface test program, test results and interpretation of the test <br /> results were presented in AES memorandum to the County dated July 13, 2015 (AES, <br /> 2015).A copy of this memorandum is included in Appendix C.2b. <br /> The interface shear test results and our interpretation documented above were peer <br /> reviewed by Professor Tim Stark, a renowned expert in this field,and he confirmed that his <br /> • <br /> PA14 Projects114-101(SJCDPW North County and Foothiliffoothill CQAIRepoffinal ReportToothill CQA Rport-Final.docx <br /> 6 <br />