ARCHIVED REPORTS_2020 ADDITIONAL SITE ASSESS RPT

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21 October 2020 Project No. 14-3002 Page 13 of 15 samples analyzed.  TPH-d were detected in the groundwater samples collected from B46, B48, B65 and B79 at concentrations of 150 micrograms per liter (µg/l), 98 µg/l, 1,000 µg/l and 330 µg/l, respectively. TPH-d concentrations detected from B65 and B79 exceed the MCL Priority of 200 µg/l.  TPH-mo were detected in the groundwater samples collected from B46, B48, B65 and B79 at concentrations of 460 µg/l, 380 µg/l, 6,100 µg/l and 760 µg/l, respectively. There is no established MCL Priority for TPH-mo.  Total lead was detected in groundwater samples from B46, B48 and B65 at concentrations of 0.37 milligrams per liter (mg/l), 0.00075 mg/l and 0.017 mg/l, respectively. The concentrations exceed the MCL of 0.015 mg/l. However, the samples were inadvertently analyzed for total lead and not dissolved lead.  Dioxins/Furans were detected in the groundwater samples collected from B46, B48 and B65 at TEQ concentrations of 0.723 picograms per liter (pg/l), 2.41 pg/l, and 0.0126 pg/l, respectively. The concentrations detected were significantly below the MCL of 30 pg/l for dioxin/furans. Analytical results of groundwater samples are summarized in Table 8. The laboratory reports (listed in Section 5.3.), QA/QC reports and chain of custody forms are included in Appendix D. Laboratory EDF files were QA/QC checked and uploaded to the State Water Board GeoTracker site. 6.0. SUMMARY AND CONCLUSIONS Based upon the environmental activities completed, AGI provides the following summary and conclusions:  Lithology at the site consists of silty sand and sand from near surface grade to approximately 14 feet bsg (18 feet bsg in the former power plant area) and clay from 14 to 15 feet bsg (between 18 and 20 feet bsg in the former power plant area). In most borings, silty sand grades into poorly graded sand between approximately 9 and 14 feet bsg. Groundwater was generally encountered in the poorly graded sands between 10 and 11 feet bsg and between 14 and 15 feet bsg in the former power plant area. The surface elevation of the former power plant area is approximately 3.5 to 5.0 feet higher than the surrounding area.  Two additional waste cell areas were identified at the site: 1) Waste Cell No. 1A is located near the eastern property boundary and appears to be the continuation of the South Waste Cell. However, Waste Cell No. 1A is discontinuous from the South Waste Cell. Waste was not encountered along the property boundary within the benched/sloped area of the stormwater retention basin. Waste Cell No. 1A is approximately 1,200 square feet with waste observed between four (4) and ten (10) feet bsg. The waste cell is fully defined (Figure 3). Waste Cell No. 2A is located