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Chevron Environmental Management Company Soil and Groundwater Investigation Report Tracy Byron Road Project kilogram(mg/kg)were not reported in soil samples collected from 15 of the 36 soil borings. TPHc concentrations ranged from 5.1 mg/kg to 8,300 mg/kg. In general the highest concentrations of TPHc were detected in soil samples collected from 5 to 12 feet bgs. In many of these borings, this interval represents the vadose zone; the interval between ground surface and the depth of first encountered groundwater. Soil samples collected between 5 and 12 feet bgs containing concentrations of TPHc greater than 1,000 mg/kg were collected from borings SB-2, SB-10, SB-11, SB-19, SB-22, SB-23, SB-25, SB-26, SB-28, SB-34, SB-35, and SB-36. In samples collected deeper than 12 feet bgs, elevated concentrations of TPHc were detected in borings SB-3 (980 mg/kg at 22 feet bgs), SB-6 (8 10 mg/kg at 18 feet bgs), and SB-30 (8 10 mg/kg at 14 feet bgs). Detectable concentrations of TPHc were not reported in 25 of the 35 soil samples collected from the total depth of each boring. A soil sample collected at 41 feet bgs from SB-22 was not analyzed due to concerns of sample cross-contamination from SPO encountered in the borehole. Detectable concentrations of TPHc in the bottom samples ranged from 5.1 mg/kg to 39 mg/kg. Benzene was not reported at or above the laboratory detection limit in any of the soil samples collected from the 36 borings. Toluene was not detected in 28 of the 36 soil borings. Detectable concentrations of toluene ranged from 0.04 mg/kg to 0.2 mg/kg. Ethylbenzene was not detected in 25 of the 36 soil borings. Detectable concentrations of ethylbenzene ranged from 0.006 mg/kg to 1.1 mg/kg. Total xylenes were not detected in 25 of the 36 soil borings. Detectable concentrations of total xylenes ranged from 0.03 mg/kg to 9.5 mg/kg. Soil sample chemical analytical results are presented in Table 1 and on Figures 3a, 3b, 3c, and 3d. Soil samples from boring SB-29 did not contain any detectable PAHs. However, detectable concentrations of PAHs were reported in 35 of the 36 soil borings. Phenanthrene and pyrene were the two most frequently reported PAHs and were detected in 89 and 78 of the 100 soil samples submitted for analysis,respectively. Reported concentrations of phenanthrene ranged from 0.0003 mg/kg to 3.8 mg/kg. Reported concentrations of pyrene ranged from 0.0004 mg/kg to 1.5 mg/kg. Benzo(a)pyrene and dibenzo(a,h)anthracene were not detected in soil samples submitted from 15 and 27 of the 36 soil borings, respectively. Reported concentrations of benzo(a)pyrene ranged from 0.0004 mg/kg to 0.30 mg/kg. Reported concentrations of dibenzo(a,h)anthracene ranged from 0.0005 mg/kg to 0.050 mg/kg. Soil sample chemical analytical results for PAHs are presented in Table 2, and on Figures 3a, 3b, 3c, and 3d. Copies of the soil chemical analytical reports are included in Appendix D. 5.2 GRAB GROUNDWATER SAMPLE ANALYSES All groundwater samples collected by SAIC were submitted to Friedman&Bruya, Inc. (F&B) in Seattle, Washington(California certified laboratory# 1727)under SAIC chain-of-custody procedure. Selected groundwater samples were analyzed for BTEX by EPA Method 8021 B,total petroleum hydrocarbons quantified as diesel (TPHd; C10—C25)by EPA Method 8015 Modified with and without silica gel cleanup, and PAHs by EPA Method 8270 C SIM. For silica gel cleanup an aliquot of the sample extract for TPHd analysis was passed through a l0-gram column of silica gel and re-analyzed for TPHd by EPA Method 8015 Modred. In addition, selected grab groundwater samples were submitted for analysis of total dissolved solids (TDS)by EPA Method 160.1. Grab groundwater samples were analyzed for TDS to gauge groundwater quality as it pertains to a potential drinking water resource. TDS samples were submitted to North Creek Analytical, Inc. of Seattle,Washington under F&B chain of custody. In addition to SAIC's grab groundwater samples,the RWQCB collected split groundwater samples from borings SB-34 (GW-34-19) and SB-35 (GW-35-18). The RWQCB submitted their samples to a separate analytical laboratory under RWQCB chain of custody. 5.2.1 Grab Groundwater Sampling Analytical Results Concentrations of TPHd were detected above the laboratory reporting limit in 9 of the 15 groundwater samples analyzed by EPA Method 8015 Modified, without silica gel cleanup. Concentrations of TPHd ranged from 59 micrograms per liter(tig/L) in groundwater sample GW-12-13 to 8,900 µg/L in 6