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samples with detectable levels of BTEX and this value was used for the average exposure scenario (Table 3-1). To be very protective of human health and groundwater and evaluate worst case } conditions, the highest hit of each chemical was used in the assessment for the Reasonable Maximum Exposure (RME) scenario. This is making the assumption that the average .soil concentrations across the area with residual contamination had the r highest concentrations detected. The concentrations used for the RME concentrations are as,follows: benzene 0.68 mg/Kg, toluene-2.1 mg/Kg, ethylbenzene 16 mg/Kg, and xylene 44 mg/Kg (Table 3-1). ' Groundwater sampling at the,on site well and the groundwater sample near the former tank location did not detect,any petroleum hydrocarbons. 4 ' 3.3 COMPARISON WITH PRELIMINARY REMEDIATION GOALS The levels of BTEX components were compared with:U.S. EPA Region IX Preliminary Remediation Goals (PRGs) (EPA 1995). PRGs have been calculated to be conservative f and protective of human health so as not to underestimate site,risks. The overall result of using PRGs 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, prioritized areas of concern at large sites, and 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 inhalation of particulates. PRGs are to be used for a single medium (e.g. soil, air, or ` water). PRGs do not consider impact to groundwater. The following table compares the PRGs for soil for residential and industrial sites and tap water with the 95% UCL concentration calculated for the site and the highest detected concentration (highest hit). SALDCIYELLO.RPT May 4,1995 3-2 -