COMPLIANCE INFO_2023 Q4 WATER QUALITY RPT

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Forward Landfill – 2023 Annual Corrective Action Evaluation Report www.arcadis.com Forward Landfill 2023 Annual CA Eval Rpt_08012023 3 3 TVOC Mass Trend The estimated TVOC masses for the past four quarters were reviewed for increasing trends. There was not an increase in TVOC mass over the four consecutive quarters of the monitoring period. The annual median TVOC mass decreased from 158 kilograms (kg) in 2022 to 153 kg in the 2023 monitoring year (Table 10). The TVOC mass is largely driven by the concentrations of VOCs in well AMW-22S, particularly carbon tetrachloride and chloroform. These carbon tetrachloride and chloroform detections do not occur in the wells closest to the ARU and may be associated with separate offsite sources. Other significant contributors to the TVOC mass include wells AMW-1 (PCE and TCE), AMW-13 (PCE and TCE), and, more recently, AMW-46 (PCE and TCE). The distribution of carbon tetrachloride and chloroform near well AMW-22S has been further delineated by the recent installation of new wells AMW-50S, AMW-50M, AMW-51M, AMW-52S, and AMW-52M, which were added to the monitoring program beginning in the second quarter of 2023. The initial results from these new wells indicate that the occurrence of carbon tetrachloride and chloroform near well AMW-22S is more limited than previously mapped, and this change resulted in a decrease in TVOC mass for the second quarter of 2023. The calculated TVOC mass for the second quarter of 2023 is the lowest since 2015 (Table 10). TCE has been detected in wells at the 7833 Newcastle Road residence, to the north of the ARU. The TCE appears to represent a localized offsite source and is not addressed in this report. 4 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 no individual well TL exceedances during the monitoring period. 5 Condition of Landfill Cover During the monitoring period, there were minor erosional issues addressed by placement and compaction of soil material during the time of inspection. No leachate seeps were reported, and no notice of violations (NOV) were issued to the facility regarding cover-related issues during the monitoring period. 6 Landfill Gas Monitoring Results At municipal solid waste (MSW) landfills, such as Forward Landfill, MSW is heterogeneous, and therefore, patterns of landfill gas (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 a function of the types and age of waste in the landfill and the extent of the reactions that produce various compounds from the anaerobic decomposition of