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R � <br /> enviroso <br /> 3.4 Ground Water Chemical Analytical Data <br /> Ground water samples collected from Borings SB-1, SB-2, SB-4, and SB-5 contained <br /> TPPH concentrations ranging from 15,000 to 38,000 parts per billion (ppb), TEPH <br /> concentrations ranging from 2,700 to 25,000 ppb, and benzene concentrations ranging <br /> from 220 to 1,900 ppb Ground water samples from these four borings contained MTBE <br /> concentrations ranging from 110 to 370 ppb SB-5 contained the highest level of MTBE at <br /> 370 ppb However, an EPA Method 8260 MTBE confirmation analysis performed on the <br /> ground water sample from SB-5 found MTBE to be ND at a detection limit of 50 ppb <br /> Ground water samples from Borm SB-3 contained ND levels of TPPH and benzene, and <br /> TEPH at a concentration of 430! pb MTBE was not detected in ground water samples <br /> from Boring SB-3 <br /> Chromium, nickel, and zinc were dete tqd in ground water samples from Boring SB-2 at <br /> concentrations ranging from 1 1 to 1 6(pf� Oil and Grease was not detected in the ground <br /> water sample from Boring SB-2 Concentrations of VOCs and SVOCs were detected in <br /> the ground water sample from SB-2 (51 ppb dichloroethane, 390 ppb <br /> 2-methylnaphthalene, and 350 ppb naphthalene) <br /> The ground water chemical analytical data are presented in Table 3 and shown on Plate 2 <br /> 4.0 SUMMARY OF FINDINGS <br /> Lithology encountered during the drilling of the exploratory soil borings consisted of clay, <br /> silt, clayey sand, silty sand, and sand to a maximum depth explored of approximately 36 <br /> feet below grade (fbg) First encountered ground water occurred in the borings at depths <br /> ranging from 19 to 33 fbg Ground water in the borings rose to levels ranging from <br /> approximately 13 to 16 fbg <br /> Low levels of petroleum hydrocarbons were detected in soil samples from Borings SB-1 <br /> through SB-4 Boring SB-5, located along the western property line, contained the highest <br /> levels of petroleum hydrocarbons in soil 890 ppm TPPH, 260 ppm TEPH, and ND <br /> (c0 50) benzene <br /> Chromium, lead, nickel, and zinc were detected in soil samples from Boring SB-2, located <br /> in the vicinity of the former waste oil tank The concentrations bf metals were all below the <br /> State of California Total Threshold Limit Concentration (TTLC) values Soil samples from <br /> Boring SB-2 contained phenol at concentrations ranging from 770 to 930 ppm <br /> The concentrations of TPPH in ground water at the site ranged from ND to 38,000 ppb <br /> The highest concentrations of TPPH were detected along the western property boundary <br /> TEPH was detected in ground water samples from each boring at concentrations ranging <br /> from 430 to 25,000 ppb The highest concentration of TEPH in ground water was detected <br /> in the vicinity of the former waste oil tank <br /> 407 4 <br />