ARCHIVED REPORTS_2010 - Laserfiche WebLink

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W. MICHAEL CARROLL, PE COUNTY OF SAN JOAQUIN DEPARTMENT OF PUBLIC WORKS DECEMBER 22, 2009 • 24 -inch operations layer Critical Interfaces: — Smooth side of HDPE geomembrane-geonet — Geonet-geotextile Module 4 and Future Modules Base Liner (starting from the bottom): • 12 -inch compacted soil layer • Geosynthetic clay liner (GCL) barrier • 60 -mil double -sided textured HDPE geomembrane • 9 -inch -thick drainage layer • 8 oz/ yd non -woven geotextile separator • 24 -inch -thick operations soil layer Critical Interfaces: — GCL-textured HDPE geomembrane Side Slope Liner (starting from the bottom): • 6 -inch compacted soil layer • GCL • 60 -mil double -sided textured HDPE geomembrane • Geocomposite drain • 24 -inch -thick operations soil layer Critical Interfaces: — GCL-textured HDPE geomembrane — Textured HDPE geomembrane-geocomposite drain — Geocomposite drain -operations soil While the interface shear test data provided in Appendix E of the 2007 report indicated the smooth HDPE geomembrane/geonet and geonet/non-woven geotextile interfaces of Modules I and 3 have large displacement friction angles > 12 degrees, experience indicates typical friction angles of about 10 degrees for these interfaces. Therefore, to be conservative, a friction angle of 10 degrees and zero adhesion was assumed for the 2007 stability analyses. A double -sided textured HDPE geomembrane was used for the liner system in Module 4 in lieu of the single -sided textured geomembrane in Module 3 and will be used in all future modules (5 through 11). The double -sided textured HDPE geomembrane/GCL interface is the most critical. As agreed at the August 31, 2009 meeting, we designed a testing regime to obtain liner interface data for the slope stability analyses of Modules 5 through 11 for normal stresses that will occur as currently proposed. The critical interface is either between the textured geomembrane and the GCL or internal PAGE 4 J O