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Troy Estacio - 3 - 2 June 2020 <br />The samples were analyzed for total petroleum hydrocarbons (TPH), semi-volatile <br />organic compounds (SVOCs), polychlorinated biphenyls (PCBs), title 22 metals, <br />arsenic, lead, dioxins and furans. None of these 70 samples contained any of the tested <br />analytes at concentrations exceeding the hazardous waste criteria or <br />commercial/industrial regional screening levels (RSLs) established by the United States <br />Environmental Protection Agency (US EPA). <br /> Verification Waste/Stockpile Samples from WU1: A total of 49 spatially distributed <br />random/representative samples of stockpiled wastes excavated from WU1 were <br />collected for analytical laboratory testing. Each sample was analyzed for TPH, SVOCs, <br />PCBs, Title 22 metals, dioxins and furans. None of these 49 samples contained metals, <br />TPH, PCBs, SVOCs, or dioxins and furans at concentrations above the <br />commercial/industrial screening levels established in the EMMP. A site-specific <br />background concentration of 8.6 milligrams per kilogram (mg/kg) was established for <br />arsenic in the EMMP. In addition, none of results exceeded hazardous waste criteria <br />established in the California Code of Regulations (CCR) Title 22, Division 4.5. <br />A total of 11 waste/stockpile samples from WU1 containing the highest concentrations <br />of total metals were analyzed for soluble Title 22 metals by the Waste Extraction <br />Method by EPA Method 1311 using DI as the extractant (DI WET). Samples were <br />included from all five stockpiles and results show DI WET concentrations of chromium, <br />arsenic, and lead exceeded the California Maximum Contaminant Level (MCL) values in <br />most samples. <br />WU1 Materials Reuse Evaluation <br />To evaluate materials removed from WU1 for reuse, the potential for future impacts to <br />groundwater as a result leaching of metals from the materials was evaluated using DI WET <br />analyses for soluble Title 22 metals. Although the results show most of the Title 22 metals did <br />not exceed California Maximum Contaminant Levels (MCL), concentrations of arsenic, lead <br />and chromium exceeded their respective MCLs in several samples. Arsenic exceeded its MCL <br />of 0.01 mg/L in 7 of 11 samples with concentrations ranging from 0.017 to 0.039 mg/l. Lead <br />exceeded its MCL of 0.015 mg/L in all 11 samples with concentrations ranging from 0.046 to <br />0.39 mg/L. Chromium exceeded its MCL of 0.05 mg/L in 6 of the 11 samples with <br />concentrations ranging from 0.054 to 0.069 mg/L. <br />Groundwater Evaluation <br /> Chromium and Lead: None of the groundwater samples collected from beneath WU1 as <br />part of the assessment work detected chromium or lead exceeding their respective <br />MCLs. <br /> Arsenic: Elevated arsenic detections in groundwater beneath the site were inconsistent <br />and did not appear to be related to a specific site feature or location. Department of <br />Defense studies on the nearby Rough and Ready Island show that naturally occurring <br />arsenic is present in groundwater at elevated levels in San Joaquin County. Therefore, <br />the arsenic detected in groundwater beneath the site may also be naturally occurring.