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SECTIONTHRE E ®atiAnalysis into two categories based on depth below ground surface 1) shallow soil samples defined as 15 feet bgs and less and, 2) deeper soil samples greater than 15 feet bgs In order to be protective of human health and the environment, soil data were not separated based on date All soil data were used in the assessment that met QA/QC criteria, which includes data that were 12 years old Table 3-1 includes the shallow soil samples that were collected and analyzed for BTEX. Results of duplicate samples were averaged with the original sample results In calculating 95 percent upper confidence limits (95% UCLs) on arithmetic mean concentrations, one-half the detection limit was used for results reported as non-detect The 95% UCLs were calculated assuming a normal distribution Fifty three soil samples were collected and analyzed for BTEX in the top 15 feet The average surface soil concentration of benzene was 0 32 mg/kg and the 95% UCL concentration for benzene was 0 71 mg/kg The average surface soil concentration for toluene was 9 77 mg/kg and the 95% UCL concentration was 25 88 mg/kg The average surface soil concentration for ethylbenzene was 5 37 mg/kg and the 95% UCL concentration was 14 22 mg/kg The average surface soil concentration for xylenes was 18 69 mg/kg and the 95% UCL concentration was 49 65 mg/kg Benzene was detected in 11 out of the 53 shallow samples, toluene was detected in 15 out of 53, ethylbenzene was detected in 10 out of 53, and xylenes were detected in 14 out of 53 samples Subsurface soil data greater than 15 feet bgs are summarized in Table 3-2 In the subsurface, 186 soil samples were collected and analyzed for BTEX The average concentration of benzene in the subsurface soil was 0 44 mg/kg and the 95% UCL concentration was 0 66 mg/kg The average concentration for toluene was 13 07 mg/kg and the 95% UCL concentration was 25 36 mg/kg For ethylbenzene the average concentration was 4 79 mg/kg and the 95% UCL concentration was 9 12 mg/kg For xylenes the average concentration in the deeper subsurface soil was 15 73 mg/kg and the 1 95% UCL concentration was 29 59 mg/kg Benzene was detected in 51 out of the 186 deeper subsurface samples Toluene, ethylbenzene, and xylenes were detected in 49, 46, and 54 subsurface samples, respectively 3.1.2 Comparison of Soil Data with EPA Region IX Preliminary Remediation Goals (PRGs) The levels of BTEX components were compared with U S FPA Region IX Preliminary Remediation Goals (PRGs) (EPA Region IX, 1998) PRGs have been calculated to be conservative and protective of human health so as not to underestimate site risks The overall result of using PBGs is to overestimate rather than underestimate the actual potential risk posed by the site PRGs have been developed to screen sites to evaluate if further evaluation is needed, to prioritize areas of concern at large sites, and to calculate risk associated with multiple contaminants The exposure pathways used to calculate PRGs for soil consider soil ingestion, dermal contact with soil, inhalation of volatiles, and woodww e T1188T973008NAWMKTOMREPORT%SHOREP#i DOCZ-FEBQM730MAMA 3-2