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Post-Closure Performance of liner Systems at RCRA Subtitle C Landfills
Carson, D. AND T. Tolaymat. Post-Closure Performance of liner Systems at RCRA Subtitle C Landfills. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-17/205, 2017.
The aim of the study is to facilitate the discussion and decision-making processes by illustrating what data are needed, highlighting categories of useful data that are typically lacking, and recommending techniques and tools to complement the EPA’s “Guidelines for Evaluating the Post-Closure Care Period for Hazardous Waste Disposal Facilities under Subtitle C of RCRA”. The study investigates the field performance of engineered double-liner systems based on data from 9 Subtitle C landfills sites that have completed several years of post closure care (PCC). It is noted that the document is not intended to address policy issues (such as how landfills may be managed, controlled, or regulated after PCC has ended) or to provide generic answers to defining conditions for ending PCC. This information is of interest to Regional and Program Office decision makers.
In general, field data showed a decline in leachate flow from the LCRS and LDS. In all cases, placement of cover led to a reduction in the LCRS flow rate, including where only 12 inches of intermediate cover soil had been placed. Rainfall has an effect on leachate generation, with higher LCRS flows recorded at the four wet sites and very low or negligible flows recorded at three dry sites. The incidence of precipitation as rainfall versus snowfall does not appear to affect leachate generation at the wet sites. The “apparent” hydraulic efficiency (EA) of the primary liner can be calculated as the flow in the LDS relative to the flow in the LCRS. If the only source of flow into the LDS sump is primary liner leakage, then EA provides the true measure of the effectiveness of a particular liner in limiting or preventing advective transport across the liner. Overall, calculated EA values from this study generally fall significantly short of the one suggested by the 2002 study (99%). Furthermore, as would be expected, the apparent liner efficiencies are significantly higher at dry sites than at wet sites.