Evaluation of chemical compatibility testing of geomembranes using the Comprehensive Test System and EPA Method 9090

Tests of the compatibility of geomembrane (GM) samples with waste were cond ucted using U.S. Environmental Protection Agency (EPA) Method 9090 and the Comprehensive Testing System (CTS). The CTS is a multi-axial performance te st capable of simultaneous cyclic mechanical loads and chemical exposure. T he test chemicals consisted of solvents, transportation-related compounds, and synthesized landfill leachate. Method 9090 testing was unable to distin guish between the effects of individual chemicals to which the GM was subje cted, while the CTS was able to provide statistically-significant differenc es that were also traceable to chemical properties of the solvent and the G M liner. Further, the time required for changes in mechanical properties of the GM was significantly shorter than would be expected based upon diffusi on of the solvent into the GM alone. The combination of chemical attack wit h mechanical load was found to enhance both reduction in mechanical propert ies and the ability of the solvent to diffuse into the GM. The CTS is a mor e realistic test than the existing standard test methods because of its abi lity to provide multi-axial loads and chemical exposure simultaneously. Current waste disposal regulations require sanitary and hazardous waste lan dfills to be lined with an impermeable material to prevent the transport of contaminants from the landfill into the surrounding environment, including groundwater under the landfill. GMs, composed of thick polymeric sheets, a re used to line these landfills. Polymer GM usefulness for this application depends on the ability of the polymer to survive the landfill environment, where the GM is exposed to a variety of conditions, including mechanical l oads, chemical exposure, and elevated temperatures. Current U.S. federal regulations require that chemical compatibility testin g of GM liners be performed to demonstrate that the GM is suitable for use as primary or secondary liners.' This paper compares two testing protocols for GM liners: (1) the Compatibility Test for Wastes and Membrane Liners (E PA Method 9090) and (2) the CTS. Method 9090 is the standard test battery u sed by EPA to meet the testing requirement. The CTS is a multi-axial test, capable of simultaneous application of mechanical loads, chemical exposure, and other environmental factors such as elevated temperatures on GMs.