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2017 Corrective Action Evaluation Report-Austin Road Unit Forward Landfill Figure D-3 presents cis-1,2-DCE results in ARU groundwater monitoring wells from May 2017. • The May 2017 results indicate that cis-1,2-DCE concentrations exceed 1 Vg/L at CAP monitoring well AMW-1, and EMP/CAP well AMW-21. The highest concentration of cis-1,2-DCE was measured at 5.2 µg/L in well AMW-21. Figure D-4 presents vinyl chloride results in ARU wells from May 2017. Vinyl chloride was not detected above 1 µg/L in ARU wells in May 2017.These results indicate agreement with the EFS model simulation. 7.0 SUMMARY During the monitoring period, there have been no exceedances of the TVOC mass TL, however, the median TVOC mass has doubled from the 2016 monitoring year. In addition, there were eight quarterly exceedances of individual well TVOC concentration TLs during the past four quarters: two at shallow detection well AMW-12; four at shallow corrective action well AMW- 19; and two at deep corrective action well AMW-19BR. All of these exceedances were due to increasing concentrations of PCE. On June 30, 2017, Forward submitted an Interim Groundwater Plume Remediation workplan to the RWQCB to address the TL exceedances in the vicinity of these wells. As summarized in Appendix B, with the exception of wells AMW-12, AMW-13, AMW-19, and AMW-19BR, overall TVOC concentrations have generally decreased or remained static following • implementation of the corrective action measures. However, the VOC concentrations (cis-1,2- DCE, PCE, and TCE) are still higher than the concentrations predicted in the model simulations presented in the EFS. Historically, EMP/CAP wells AMW-1,AMW-22, and AMW-22S continue to exhibit the highest TVOC concentrations downgradient of the ARU. During the monitoring period, one or more VOCs exceeded a State maximum contaminant level in wells AMW-1, AMW-12, AMW-13, domestic well 8106-A, AMW-19, AMW-19BR, AMW-21, AMW-22, AMW- 22S, AMW-26R, and AMW-29. In an effort to define the lateral and vertical limits of the VOC plume, Forward will begin drilling and installing 12 additional EMP/CAP wells downgradient of ARU in August 2017. Forward has also implemented a Domestic Well Sampling Program to evaluate the presence of VOCs in downgradient public wells. The results obtained from the additional EMP/CAP wells, the Domestic Well Sampling Program, the new Point of Compliance LFG Monitoring Program, along with the existing EMP/CAP wells will be used to prepare a revised Engineering Feasibility Study that may include revisions to the corrective action program and evaluation procedures previously described in the Evaluation Procedures Report. Forward has also prepared an Interim Groundwater Plume Remediation Workplan to address VOCs downgradient of the ARU. Project No 5017.1030 12017 Corrective Action Evaluation Report-Austin Road Unit 6 Forward Landfill