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DRAFT <br /> from <5 mg/kg to 130 mg/kg at Area 2A. Typical background arsenic concentrations <br /> reported by Bradford, et al (1996) ranged from 0.59 to 11 mg/kg for soils collected <br /> throughout California. The U.S. EPA Region 9 (1999) residential preliminary <br /> remediation goal (PRG) for arsenic (cancer endpoint) is 0.39 mg/kg and 22 mg/kg for the <br /> non-cancer endpoint. The industrial soil PRG is 2.7 mg/kg for the cancer endpoint and <br /> 440 mg/kg for the noncancer endpoint. The representative soil concentration used in the <br /> risk calculations for Area 2A was 8.9 mg/kg which exceeds the residential EPA Region 9 <br /> ' PRG. Further evaluation of natural background concentrations of arsenic in the Stockton <br /> area should be considered prior to implementing remedial actions at Area 2A. <br /> ' For lead, the representative Area 2A lead concentration of 93 mg/kg in soils was less than <br /> the child receptor-based lead in soil target concentration and the industrial receptor-based <br /> lead in soil target concentration. Consequently, the soil lead concentrations in Area 2A <br /> do not appear to represent a potential health hazard. <br /> 2.2 Area 2B <br /> Table B-6 presents the results of the noncarcinogenic hazard and carcinogenic risk <br /> evaluation for Area 2B. Noncarcinogenic HIs were less than one for all of the receptors <br /> evaluated. <br /> Excess cancer risks for the construction worker and landscape maintenance worker were <br /> 1.96E-06 and 4.89E-05, respectively. These excess cancer risks are well within the <br /> acceptable range of 1E-04 to 1E-06 for non-residential site uses. Excess cancer risk for <br /> the resident was 1.55E-04, two orders of magnitude higher than the acceptable risk of <br /> 1 E-06 for residential site use. The elevated excess cancer risk is primarily attributable to <br /> the presence of benzo(a)pyrene in soil, which was detected in one soil sample at a <br /> concentration of 1,020 µg/kg at a depth of 1.0 foot below ground surface. The soil data <br /> suggests that there may be a localized area of PAHs in Area 2B. <br /> SOMA 99-2218 16 12/10/99 <br />