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include PAHs and heavy metals associated with prior MGP related Site activities; and TPH and volatile organic compounds (VOCs)related to gasoline from the gasoline UST identified above. During the course of the SI sampling activities, 33 borings were completed to final depths of up to 55 feet bgs. Selected soil samples were collected at depths ranging from 1.5 feet to 55 feet bgs. Samples were generally collected at the following intervals: 2, 3, 5, 8, and 10 feet bgs and at 5 foot intervals thereafter. Soil samples from the 33 borings were analyzed for one or more of the following constituents: PAHs, TPH, BTEX, Title 22 Metals, sulfides and cyanide. Results from the soil analyses showed detectable levels of total PAHs in 13 of the 33 borings ranging from 0.08 mg/kg (TB-17) to 1,062 mg/kg (TB-13). TPH results indicated that only 5 soil borings had detectable concentrations of TPH, primarily TPH as motor oil (TPH-mo). Detectable concentrations of TPH-mo ranged from 60 mg/kg (TB-29) to 4,750 mg/kg (TB-24). Except at TB-24, all TPH-mo was located in the upper 2.5 feet. TPH as diesel (TPH-d) was only encountered in one boring (TB-24) at the same depth (10.5 to 11 feet bgs) as the elevated TPH-mo concentrations. TPH-g was only detected in Boring TB-32, which was located adjacent to the former gasoline UST. Detectable levels of BTEX were observed in 7 of 33 borings conducted during the SI, the highest concentrations of which were observed in TB-32. Elevated BTEX concentrations (>100 ug/kg) were also observed in Borings TB-8 and TB-24. Title 22 Metals analyses were performed on seven samples from four borings (TB-6, TB-13, TB-24 and TB-32). Results for the Title 22 Metals typically associated with MGP processes (i.e. lead and arsenic) do not appear to be elevated above background concentrations in a large majority of the SI samples. Sulfides and cyanide were not detected in the samples collected during the SI. The locations of the borings with detections of the COPCs in soil reported in the SI are presented in Figure 6. Tabulated soil data is provided in Tables 2 through 5. Five groundwater wells (TW-1 through TW-4 and TP-1) were installed during the SI. In addition, the six monitoring wells from the gasoline UST investigations (OW-1 through OW-6) were sampled. Groundwater samples were analyzed for PAHs, TPH, BTEX, Title 22 Metals, phenols, sulfides, cyanide, pH and general minerals. Results from the groundwater sampling showed no detectable concentrations of PAHs, phenols and/or cyanide in groundwater. TPH-g and BTEX compounds were detected only in the sample from OW-2, which was installed directly adjacent to the former gasoline UST. Title 22 Metals analyses reported seven metals (barium, chromium, copper, molybdenum, antimony, thallium and zinc) detected. Sulfides were detected in samples collected from OW-1 and OW-4 at concentrations of 32 mg/L and 15 mg/L, respectively. The pH of groundwater samples collected at the Site ranged from 7.54 to 7.98, which is typical for groundwater in the area of the Site. General minerals results show that the groundwater in the upper aquifer beneath the Site is unsuitable for drinking as the concentrations of many of the constituents exceeded drinking water standards. The locations of the groundwater wells and results from the collected groundwater samples are provided in Figure 8. Tabulated groundwater data is provided in Tables 7 through 10. Based on the information provided, the SI concluded that potential for the off-site migration of historic MGP residues is very low and will remain so as long as the clay layer underlying the upper aquifer is left intact. PARSONS 18 FINAL RI REPORT-FORMER TRACY MGP APRIL 2010