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2025 Annual Corrective Action Evaluation Report <br /> <br />www.arcadis.com <br />Forward Landfill 2025 Annual CA Eval Rpt_08012025(1) 8 <br />TCE data from the last 5 years are not available for wells PZ-1 through PZ-3 and CDCR-EW-1 through <br />CDCR-EW-5 because these locations were added to the monitoring program in second quarter 2025. <br />Evaluation of the above TCE concentration trends and the most recent data indicate the highest and <br />reoccurring concentrations of TCE are on the offsite CDCR property,1 with the highest concentrations <br />centered around well AMW-22S. There is an additional plume with lower concentrations at the landfill <br />centered around AMW-54R. <br /> cis-1,2-DCE concentrations exceeded 1 µg/L at groundwater monitoring wells AMW-54R, AMW-56, and <br />AMW-63. The highest concentration of cis-1,2-DCE was measured at 6.2 µg/L in well AMW-56. Where the <br />data are available, cis-1,2-DCE concentration trends across the last 5 years (Appendix D) are as follows: <br />- cis-1,2-DCE concentrations have decreased in well AMW-56. <br />- cis-1,2-DCE concentrations have been stable to increasing in wells AMW-54R and AMW-63. <br />Evaluation of the above cis-1,2-DCE concentration trends and the most recent data indicate the highest and <br />reoccurring concentrations of cis-1,2-DCE onsite, with the highest concentrations centered around well AMW- <br />56 on the northeastern corner of the landfill. <br /> Carbon tetrachloride concentrations exceeded 1 µg/L at groundwater monitoring wells MW-10, AMW-22S, <br />AMW-50S/M, AMW-52S, AMW-58S, AMW-60S/M, AMW-61M, PZ-1 through PZ-3, and CDCR-EW-1 through <br />CDCR-EW-5. The highest concentration of carbon tetrachloride was measured at 69 µg/L in well AMW-22S. <br />Where the data are available, carbon tetrachloride concentration trends across the last 5 years (Appendix D) <br />are as follows: <br />- Carbon tetrachloride concentrations have decreased in monitoring well AMW-61M. <br />- Carbon tetrachloride concentrations have remained relatively stable in monitoring wells AMW-22S and <br />AMW-50S. <br />- Carbon tetrachloride concentrations have been stable to increasing in monitoring wells MW-10, AMW- <br />50M, AMW-52S, AMW-58S, AMW-60S, and AMW-60M. <br />Carbon tetrachloride data from the last 5 years are not available for wells PZ-1 through PZ-3 and CDCR-EW- <br />1 through CDCR-EW-5 because these locations were added to the monitoring program in second quarter <br />2025. <br />Evaluation of the above carbon tetrachloride concentration trends and the most recent data indicate the <br />highest and reoccurring concentrations of carbon tetrachloride are on the offsite CDCR property, with the <br />highest concentrations centered around well AMW-22S. <br /> Chloroform concentrations exceeded 1 µg/L at groundwater monitoring wells AMW-22S, AMW-50M, AMW- <br />51S, AMW-58S, AMW-60M, PZ-1 through PZ-3, and CDCR-EW-1 through CDCR-EW-5. The highest <br />concentration of chloroform was measured at 26 µg/L in well CDCR-EW-4. Where the data are available, <br />chloroform concentration trends across the last 5 years (Appendix D) are as follows: <br />- Chloroform concentrations have remained relatively stable in monitoring wells AMW-22S and AMW-51S. <br /> <br />1 This evaluation does not include the concentrations of TCE at the 7833 Newcastle Road property as it appears <br />to represent a separate localized offsite source and is not addressed in this report. <br />