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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 /> Test Series 1 (Foundation layer soil vs GCL)was considered to represent both the base liner and the <br /> side slope liner since the foundation layer soils and the side slope subgrade soils were the same <br /> materials. <br /> To further confirm the findings from the single interface test series, two series of sandwich tests <br /> were performed: <br /> Test Series 4 - Base liner sandwich (foundation layer soil, GCL, HDPE geomembrane and <br /> GDM) <br /> Test Series 5 - Side slope liner sandwich (side slope subgrade soil, GCL, HDPE <br /> geomembrane,geocomposite and operations layer soil) <br /> All of the interface strength tests were performed at SGI Testing Services Laboratory (SGI) of <br /> Norcross, Georgia. Precision had sampled the rolls at the respective manufacturing plants in <br /> conjunction with sampling for conformance tests and directly shipped to SGI for interface shear <br /> tests. Roll selection was done by AES based on the MQC data. The foundation layer soil and <br /> operations layer soil were the same material, and were collected from the landfill site and shipped <br /> to SGI. <br /> The test configuration in the shear box and the remolding, soaking, and consolidation details for the <br /> • individual interface and the sandwich tests provided to SGI are shown in Table 12 and Table 13 <br /> respectively. <br /> The test results are summarized in Table 14 and are discussed below: <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 /> PA14 Projects114-101(SJCDPW North County and Foothiliffoothill CQAIReportTinal ReportToothill CQA Rport-Final.docx <br /> 23 <br />