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09 December 2021 <br />Project No. 14-3002 <br />Page 3 of 9 <br /> <br />Soil and waste are impacted in AOC1 with dioxins and PCBs at maximum concentrations <br />of 17.6 picograms per gram (pg/g) and 1.0 milligrams per kilogram (mg/kg), respectively. <br />Groundwater is not impacted with COCs in AOC1. Only one COC was detected above <br />environmental screening levels in AOC1 (PCB concentration of 1.0 mg/kg was detected <br />above the May 2020 EPA Region 9 Regional Screening Level (RSL) of 0.97 mg/kg for <br />industrial soil). The extent of glass waste and COC contamination in AOC1 is defined. <br /> <br />Soil and waste are impacted in AOC2 with dioxins, PCBs and TPH at maximum <br />concentrations of 96.6 pg/g, 320 mg/kg, and 7,500 mg/kg (TPH-mo), respectively. The <br />COCs were detected in several samples above their respective RSLs and the <br />January 2019 California Regional Water Quality Control Board Environmental Screening <br />Levels (ESLs). PCB Aroclor 1254 was detected above the RSL in 20 samples collected <br />between three and ten feet bsg. Groundwater is impacted in AOC2 with TPH-diesel <br />(TPH-d), TPH-motor oil (TPH-mo) and dioxins at maximum concentrations of <br />1,000 micrograms per liter (µg/l), 6,100 µg/l, and 2.41 picograms per liter (pg/l), <br />respectively. Additionally, total lead was detected in groundwater from AOC2 at a <br />maximum concentration of 0.37 milligrams per liter (mg/l). Dioxin concentrations were <br />below the State of California Maximum Contaminant Level (MCL) of 30 pg/l; and TPH-d <br />concentrations were above the MCL Priority established in the January 2019 ESLs. The <br />extent of glass waste and COC contamination in AOC2 is generally defined to the north, <br />partially defined to the east, and undefined to the west and south. <br /> <br />Analytical results of COCs in soil and waste are summarized in Tables 1 and 2 and results <br />of COCs in groundwater are summarized in Tables 3 and 4. Analytical results of Title 22 <br />metals, semi-volatile organic compounds (SVOCs), polyaromatic hydrocarbons (PAHs), <br />volatile organic compounds (VOCs), nitrates, total ammonia, and total dissolved solids <br />are provided in Tables 5 through 10. Groundwater elevation data is summarized in <br />Table 11. Site plans and cross-sections illustrating COC results in AOC1 are presented <br />in Figures 6 through 11 and in Figures 12 through 24 for AOC2. A groundwater elevation <br />map illustrating groundwater flow direction and gradient from monitoring performed in <br />April 2021 is presented in Figure 25. <br /> <br />Additional detailed site background and historical information was provided in the Current <br />Conditions Report dated 24 May 2021. <br /> <br /> <br />2.5. STRATIGRAPHY AND GROUNDWATER <br /> <br />The lithology of the Site from surface grade to approximately 14 feet bsg (18 feet bsg in <br />AOC2) is comprised of fine-grained silty sands and fine- to coarse-grained sands. Clay <br />was encountered in most borings and wells between 14 and 15 feet bsg (between 18 and <br />19 feet bsg in AOC2) and extending to 20 feet bsg in some locations. In most borings, <br />silty sand grades into poorly graded sand between approximately 6 and 9 feet bsg in <br />AOC1 and between approximately 9 and 12 feet bsg in AOC2 (Figures 8 through 11 and <br />19 through 23; and Appendix A). Groundwater was generally encountered in the poorly <br />graded sands between 10 and 11 feet bsg (AOC1) and between 14 and 15 feet bsg