The current project addresses the urgent need for knowledge of the effectiveness of the double-liner system of coal combustion products (CCP) landfills in Florida and its equivalency to the Subtitle D composite liner. The main objectives of the ongoing project are to (1) verify the equivalency of the Florida double liner system to the composite liner system of the Environmental Protection Agency (EPA) when used for coal disposal applications, and (2) determine if the state of the art, from the literature and current knowledge about landfill barriers, support the EPA conclusions in 40 CFR 257. In addition to the leakage rate calculation proposed previously (currently being investigated), we extend the question of equivalency of the double-liner system to the subtitle D composite liner in terms of mass transport. CCP leachate chemistry in Florida will be investigated, and numerical modeling will be conducted to compare the contaminant transport through the double liner and Subtitle D composite liner systems. We will also investigate the effect of the leachate chemistry on the leakage rate and mass transport through the liner system. Alternative disposal methods, such as co-disposal of CCP with municipal solid waste (MSW) will be explored. Finally, field studies with prototype double-liner and Subtitle D composite liner will be designed to provide further equivalency validation. The conceptual framework of this study is shown in Fig. 1.
Fig. 1 The conceptual framework of the current study.
Tasks for the proposed project include (1) characterize the chemistry of CCP and CCP-MSW co- disposal leachate, (2) evaluate compatibility and leakage rate of liner materials to CCP and CCP- MSW co-disposal leachate, (3) model mass transport through double liners and Subtitle D composite liners, and (4) design a field approach to assess liner equivalency.
Task 1 – Characterize the Chemistry of CCP and CCP-MSW Co-disposal Leachate. The objective of Task 1 is to characterize the chemical composition of CCP and CCP-MSW Co-disposal leachates and to identify target leachates that can be used for evaluating the chemical compatibility of liner materials.
Task 2 – Compatibility and Leakage Rate of Liner Materials to CCP and CCP-MSW Co-disposal Leachate. Hydraulic conductivity tests will be conducted on CSLs and GCLs following ASTM D5084 and D6766 using each of the typical and worst-case leachates identified in Task 1. Prior to hydraulic conductivity testing, the GCLs will be hydrated by contact with a moist subgrade following the procedure in the literature.
Task 3 – Modeling Mass Transport in Double Liners and Subtitle D Composite Liners. Based on the leakage rate calculation during the current FSU 1-year project, the inorganic solute transport through defects in Florida’s double liner system and Subtitle D composite liner will be simulated using COMSOL.
Task 4 – Field Equivalency Assessment of Liner Equivalency. The equivalency of Florida’s double liner and Subtitle D liner modeled by the current proposed study will be further evaluated using cross analysis by field-scale tests.
Links to TAG Meetings
TAG 1 Meeting PPT Slides (TBD)
Quarterly Progress Report 1 (TBD)