Design of Landfill Lining and Final Cover Systems

HGC staff are experienced and knowledgeable in the design and construction oversight of landfill lining and final cover systems. In addition, HGC provides regulatory permitting and construction oversight services to verify installation consistent with the design. Federal regulations require composite landfill lining systems, constructed of a two-foot minimum of compacted clay overlain by an polyethylene membrane, with provision for alternative lining concepts that are protective of human health and the environment. HGC evaluates the needs of each landfill based on site conditions and the regulatory environment to determine whether a prescriptive or alternative lining system is appropriate to minimize cost and maximize operational airspace for the facility.

Where a membrane lining system is present in the base liner, federal regulations prescribe installation of an equally effective liner in the final cover system with provision for alternative cover systems that are environmentally protective. Standard methods of “entombing” landfills with so-called impermeable caps and liners may not be appropriate for all landfills, particularly for arid and semi-arid areas where leachate production is small and water tables are deep. Our understanding of vadose-zone gas and liquid flow can be quantitatively applied to create permeable caps and liners that prove to be not only more suitable for site conditions, but also much less expensive to construct and maintain. Such caps can be designed using appropriate moisture monitoring to support recreational uses such as golf courses and ballfields. HGC has the necessary gas and liquid flow credentials to conduct these studies, as well as experience designing and constructing permeable caps, and in obtaining regulatory agency approval of alternative cover system designs.

Soil Cover near Casa GrandeTechnical Bulletin

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