COMPLIANCE INFO_FINAL WMU FU-23 DESIGN RPT & CONCURRENCE LTRS

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WMU FINAL WMU FU-23 DESIGN REPORT 2-18-23 5-1 SECTION 5 Containment System The WMU FU-23 containment system consists of a composite liner and LCRS on the base of the unit. The western boundary of WMU FU-23 connects to WMUs FU-17 and FU-19. The base liner system for WMU FU-23 consists of the following, from bottom to top: • Prepared subgrade; • Minimum 2-foot-thick compacted clay liner with a maximum field hydraulic conductivity of 1 x 10-7 cm/sec; • 60-mil, double-sided textured HDPE geomembrane liner; • Cushion geotextile; • One-foot-thick blanket gravel and pipe network drainage layer with a minimum hydraulic conductivity of 0.1 cm/sec; • Nonwoven geotextile filter fabric; • One-foot-thick protective operations layer Connection, transition, termination, and anchorage details have been designed (see Construction Drawings, Appendix A) to maintain continuity among all components and to provide connection access for future systems. 5.1 Lining System As shown on the Construction Drawings (Appendix A), the WMU FU-23 base lining system will consist of a 2-foot-thick compacted, clay liner overlain by a 60-mil thick, double-sided textured HDPE geomembrane. The base lining system meets the current prescriptive Title 27 regulations and complies with Forward’s WDRs. 5.1.1 Clay Liner The clay liner will be constructed to meet the Specifications included in Appendix C. It will consist of fine-grained soils with significant clay content and without organic matter. The material will have at least 30 percent of particles passing a No. 200 U.S. Standard sieve and be classified as SC (clayey sand), CL (lean clay, sandy or silty lean clay), or CH (fat clay, sandy or silty fat clay) by the Unified Soil Classification System (USCS). The clay liner will have a maximum field hydraulic conductivity of 1 x 10-7 cm/sec when compacted to a minimum relative compaction of 93 percent at a water content 3 to 5 percent greater than the optimum water content as determined by the Modified Proctor compaction test (ASTM D1557). A field permeability test (sealed double ring infiltrometer [SDRI]) was conducted on onsite soils to assess their suitability as clay liner material. The field permeability test indicated that the onsite soils could achieve a field hydraulic conductivity of 1 x 10-7 cm/sec. The clay liner will be constructed