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2017 Corrective Action Evaluation Report-Austin Road Unit Forward Landfill The TVOC masses corresponding to all contour pairs on a given quarter's isoconcentration map were then summed to estimate the total, plume-wide TVOC mass for that quarter. Tables 6 through 9 summarize the quarterly TVOC mass estimation calculations for the monitoring period; the historical TVOC masses for the facility are summarized on Table 10; and the corresponding quarterly groundwater potentiometric maps are presented in Appendix A. The TVOC mass for each quarter was compared to the TVOC mass TL of 789.5 kg. During the monitoring period,the calculated quarterly TVOC mass did not exceed the TL. 2.0 TVOC MASS TREND The estimated TVOC masses for the past four quarters were reviewed for increasing trends. Although the TVOC mass has not increased for four consecutive quarters over the monitoring period, the TVOC mass median value has doubled from 203 kg in the 2016 monitoring year to 407 kg in the 2017 monitoring year(Table 10). The increasing TVOC mass is primarily the result of increasing concentrations of VOCs in wells AMW-1, AMW-19,AMW-19BR, and AMW-22. 3.0 INDIVIDUAL WELL TVOC CONCENTRATIONS The TVOC concentrations observed at individual wells for the past four quarters are presented on Tables 2 through 5 and summarized on Table 11. Time-series charts for TVOC mass and individual well TVOC concentrations, and a historical database summary, are presented in Appendix B. The individual TVOC concentrations for each quarter were compared to the established TVOC concentration TLs. As shown on Table 11, there were eight quarterly individual well TL exceedances during the monitoring period, with two exceedance in shallow well AMW-12, four exceedances in shallow well AMW-19, and two exceedances in deep well AMW-19BR. All of these exceedances were the result of increasing tetrachloroethene (PCE) concentrations. 4.0 CONDITION OF LANDFILL COVER During the monitoring period, there were no significant problems reported with landfill cover that resulted in exposed waste. Minor erosional issues were addressed by placement and compaction of soil material. No leachate seeps were reported and no notices of violation (NOVs) were issued to the facility for cover-related issues during the monitoring period. S.0 LANDFILL GAS MONITORING RESULTS At municipal solid waste (MSW) landfills, such as Forward Landfill, MSW is heterogeneous, and therefore, patterns of LFG compounds and their concentrations can vary within the landfill. Typically MSW LFG composition consists of methane, carbon dioxide, oxygen, nitrogen, and non-methane organic compound (NMOC) concentrations. The NMOC concentrations in LFG are Project No 5017.1030 12017 Corrective Action Evaluation Report-Austin Road Unit 3 Forward Landfill