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On April 15, 2015, the US EPA published the Final Rule on the regulation of the disposal of Coal Combustion Residuals (CCR) as solid waste under Subtitle D of the Resource Conservation and Recovery Act (RCRA). The Final Rule stipulated that, all CCR landfills and surface impoundments must be constructed with a composite liner or an alternative composite liner which is equally protective of the environment. The proposed composite liner must consist of an upper geomembrane (GM) liner and a lower component consisting of at least 2ft layer of compacted soil with hydraulic conductivity not greater than 1x10-7cm/sec.

In Florida, the bottom Double Liner system used in waste containment infrastructure has an upper primary GM and a lower secondary GM, separated by a leachate detection and collection layer. In the research article titled 'Evaluating the Performance of Florida Double‐Lined Landfills' presented by the Florida Department for Environmental Protection (FDEP) during the Geosynthetics Conference in 1997, it was reported that the landfills designed and constructed using Florida Double Liner system were meeting and outperforming the design expectations. Because the Florida Double Liner system was protective of human health and the environment, the US EPA earlier approved it as an alternative to the Subtitle D composite liner system.

However in the regulations for the design, construction, operation and maintenance of CCR landfills and surface impoundments (Final Rule, April 2015), the US EPA stated, after evaluating only the soil component of the Florida Double liner system, that the system may not be appropriate for coal ash landfills.

Objectives:

• verify the equivalency of the Florida double liner system to the composite liner system of Environmental Protection Agency (EPA) when used for coal disposal applications,

• determine if state of the art, from the literature and current knowledge about landfill barriers, support the EPA conclusions in 40 CFR 257