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Forward Landfill Water Quality Monitoring Report <br />Fourth Quarter/Annual 2023 <br />www.arcadis.com <br />Forward Landfill 4Q23 Water Quality Mon Report_02012024 6 <br />2.1.5 Detection Monitoring Program, Austin Road Unit <br />Field and laboratory results for the DMP samples collected at Austin Road Unit groundwater monitoring wells <br />during the fourth quarter of 2023 are summarized below and in Tables 6 and 7. <br />Non-Statistical Data Analysis: The CNSDAM was performed for VOCs detected in the site monitoring wells <br />during the fourth quarter of 2023. As shown in Table 6 and on Figures 3, 11, and 12, the following VOCs were <br />detected at the Austin Road Unit: <br /> AMW-6 – PCE (above PQL) and trichloroethene (TCE; above MDL); and <br /> AMW-12 – PCE (above PQL). <br />Concentration Limit Thresholds: In accordance with the MRP (RWQCB 2014), the routine inorganic <br />monitoring data from the Austin Road Unit for the fourth quarter of 2023 were compared to CLs established <br />for each well. CLs were recalculated through the fourth quarter of 2022 (Arcadis 2023b). Details on the <br />statistical analysis for the established CLs are presented in Appendix I to the Fourth Quarter Report (Arcadis <br />2023b). <br />As summarized in Table 7, the following CLs were exceeded at the Austin Road Unit during the fourth quarter <br />of 2023: <br /> AMW-5R – Sulfate. <br />As a result, these wells have been identified for resampling in the first quarter of 2024. The RWQCB was notified <br />of these VOC detections and CL exceedances in a letter dated January 31, 2024 (Arcadis 2024). <br />2.1.6 New Monitoring Wells, Austin Road Unit <br />Monitoring wells AMW-58S, AMW-58M, AMW-59S, and AMW-59M were installed between August 7 through <br />August 17, 2023 (Arcadis 2023a) as part of an expanded scope to address the requirement in the 2017 Cleanup <br />and Abatement Order R5-2017-0703 for an interim remedial action to address the volatile organic compound <br />(VOC) plume mass beneath the CDCR property. The four groundwater monitoring wells were installed to monitor <br />and define the shallow and intermediate depth plume extent beneath the CDCR property. Field and laboratory <br />results for the CDCR monitoring wells for the fourth quarter of 2023 are summarized in table 8. <br />2.1.7 Quality Assurance/Quality Control Results <br />The quality assurance (QA)/quality control (QC) samples collected at the Forward and Austin Road Units during <br />the fourth quarter of 2023 and the associated analytical results are described below. <br />Forward Unit <br /> QA/QC samples at the Forward Unit included two field blanks, one equipment blank, laboratory method <br />blanks, and one duplicate sample. The method blanks were analyzed for all of the analytes included in the <br />MRP (RWQCB 2014); equipment, field, and trip blanks were analyzed for VOCs by United States <br />Environmental Protection Agency (USEPA) Method 8260.