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Forward Landfill – 2023 Annual Corrective Action Evaluation Report
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<br />Forward Landfill 2023 Annual CA Eval Rpt_08012023 5
<br />In past Annual Corrective Action Evaluation Reports, these projected isoconcentration maps were compared to
<br />maps based on contemporary data collected from the same monitoring wells utilized in modeling. However, the
<br />EFS simulations projected that none of the modeled VOCs would be detected above 1 µg/L by 2012 after nine
<br />years of recharge from the recharge basin. Accordingly, there are no projected isoconcentration maps available
<br />for comparison to current results.
<br />Consistent with past Annual Corrective Action Evaluation Reports, isoconcentration maps for the four modeled
<br />VOCs are presented in Appendix D using the second quarter 2023 monitoring results. The maps in Appendix D
<br />utilize a contour interval of 1.0 µg/L and do not include values less than 1 µg/L.
<br />Figure D-1 presents PCE results in ARU groundwater monitoring wells from second quarter 2023 (2Q23). The
<br />2Q23 results indicate that PCE concentrations equaled or exceeded 1 µg/L at detection monitoring well AMW-
<br />12; domestic supply wells 7898-A and 8106-A; and in EMP/CAP wells AMW-1, AMW-13, AMW-18B, AMW-19,
<br />AMW-22, AMW-22S, AMW-23M, AMW-24R, AMW-25, AMW-26R, AMW-29S, AMW-29, AMW-31S, AMW-31,
<br />AMW-44, AMW-45, AMW-46, AMW-50S, AMW-50M, AMW-51M, AMW-52S, and AMW-52M. The highest
<br />concentration of PCE was measured at 12 µg/L in well AMW-22S.
<br />Figure D-2 presents TCE results in ARU groundwater monitoring wells from 2Q23. The 2Q23 results indicate
<br />that TCE concentrations equaled or exceeded 1 µg/L at EMP/CAP wells AMW-1, AMW-13, AMW-22S, AMW-22,
<br />AMW-23M, AMW-24R, AMW-29, AMW-46, AMW-50S, AMW-50M, AMW-51M, AMW-52S. The highest
<br />concentration of TCE was measured at 9.1 µg/L in well AMW-22S.
<br />Figure D-3 present cis-1,2-DCE results in ARU groundwater monitoring wells from 2Q23. Results indicate that
<br />cis-1,2-DCE concentrations exceeded 1 µg/L at EMP/CAP well AMW-1. The concentration of cis-1,2-DCE was
<br />measured at 3.3 µg/L in well AMW-1.
<br />Figure D-4 presents vinyl chloride results in ARU wells from 2Q23. Vinyl chloride was not detected above 1 µg/L
<br />and these results indicate agreement with the EFS model simulation.
<br />8 Summary
<br />During the monitoring period, the TVOC mass TL was not exceeded in any of the four quarters.
<br />As summarized in Appendix B, overall TVOC concentrations have generally decreased or remained static
<br />following implementation of the corrective action measures. However, the VOC concentrations (cis-1,2- DCE,
<br />PCE, and TCE) are still higher than the concentrations predicted in the model simulations presented in the EFS.
<br />EMP/CAP wells AMW-22S (primarily carbon tetrachloride and chloroform) and AMW-13 (PCE and TCE)
<br />continue to exhibit the highest TVOC concentrations downgradient of the ARU. During the monitoring period,
<br />one or more VOCs exceeded a State maximum contaminant level in wells AMW-1, AMW-13, AMW-22, AMW-
<br />22S, AMW-23M, AMW-24R, AMW-46, AMW-50M, and AMW-51M, and domestic well 8106-A.
<br />To define the lateral and vertical limits of the VOC plume, Forward added 14 new EMP/CAP wells downgradient
<br />of ARU to the evaluation during third quarter 2020. Forward has also implemented a Domestic Well Sampling
<br />Program to evaluate the presence of VOCs in downgradient private wells. The results obtained from the
<br />additional EMP/CAP wells, the Domestic Well Sampling Program, the Point of Compliance LFG Monitoring
<br />Program, along with the existing EMP/CAP wells were used to prepare a revised Engineering Feasibility Study
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