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C 2015 Annual Correctie Action Evaluation Report Austin Road Unit, Forward Landfill — Manteca California Page 5 Appendix D. Consistent with the projected maps in the EFS and maps presented in past Annual Corrective Action Evaluation Reports, the maps in Appendix D illustrate one contour corresponding to VOC concentrations equal to or greater than 1 ug/L. Figure D-1 presents tetrachloroethene results in ARU groundwater monitoring wells from May/June 2015. The model simulation predicted that tetrachloroethene would not be detected above 1 ug/L nine years after initiation of recharge. Accordingly, there is no model contour line depicted on Figure D-1. The May/June 2015 results indicate that tetrachloroethene concentrations exceed those predicted by the model simulation at: corrective action monitoring wells AMW-1 and AMW-13; detection monitoring well AMW-6; and domestic supply well 8106-A. Tetrachloroethene concentrations above 1 ug/L were observed in evaluation monitoring wells AMW-1313, AMW-1813, AMW-19, AMW-1913R, AMW-21, AMW-21 S, AMW-22, AMW-22S, AMW-24R, AMW-26R, AMW-29, AMW-31, and AMW-31 S. However, these wells were not installed until after the EFS was submitted in 2001 and were not included in the model simulations. Consequently, the simulation is not directly applicable to these wells. Figure D-2 presents trichloroethene results in ARU wells from May/June 2015. The model simulation predicted that trichloroethene would not be detected above 1 ug/L seven years after initiation of recharge. Accordingly, there is no model contour line depicted on Figure D-2. The May/June 2015 results indicate that trichloroethene concentrations exceed those predicted by the model simulation at corrective action monitoring wells AMW-1 and AMW-13 and domestic supply well 8106-A. Trichloroethene concentrations above 1 ug/L were observed in evaluation monitoring wells AMW-21, AMW-21S, AMW-22, AMW-22S, AMW-24R, AMW-26R, AMW-29, AMW-31, and AMW-31S. However, these wells were not installed until after the EFS was submitted in 2001 and were not included in the model simulations. Consequently, the simulation is not directly applicable to these wells. Figure D-3 presents cis-1,2-dichloroethene results in ARU wells from May/June 2015. The model simulation predicted that cis-l,2-dichloroethene would not be detected above 1 ug/L five years after initiation of recharge. Accordingly, there is no model contour line depicted on Figure D-3. The May/June 2015 results indicate agreement with the model simulation in the majority of the modeled area. The May/June 2015 results indicate that cis-1,2-dichloroethene concentrations exceed those predicted by the model simulation at corrective action monitoring well AMW-1. cis-1,2- Dichloroethene concentrations above 1 ug/L were observed at evaluation monitoring wells AMW-21 and AMW-21 S. However, these wells were not installed until after the EFS was submitted in 2001 and were not included in the model simulations. Consequently, the simulation is not directly applicable to these wells. Figure D-4 presents vinyl chloride results in ARU wells from May/June 2015. The model simulation predicted that vinyl chloride would not be detected above 1 ug/L four years after initiation of recharge. Accordingly, there is no model contour line depicted on Figure D-4. Vinyl chloride was not detected above I ug/L in ARU wells in May/June 2015. The results indicate agreement with the model simulation. Extraction wells EW -1 and EW -3R were installed adjacent to AMW-6 and AMW-1, respectively, and have improved groundwater quality in those areas. Given the direction of groundwater flow at the facility, improvements in groundwater quality near the extraction wells are expected to result in groundwater quality improvements to the north and northeast of the facility. )�' IST & ASSOCIATES, INC:"