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16 August 2001 AGE-NC Project No. 01-0852 Page 6 of 7 protective of humans, including sensitive groups, over a lifetime. Chemical concentrations above these levels would not automatically designate-a site as"dirty"or trigger a response action.However, exceeding a PRG suggests that further evaluation of the potential risks that may be posed by the site contaminants is appropriate. Further evaluation may include additional sampling, consideration of ambient levels in the environment, or a reassessment of the assumptions contained in these screening-level estimates (e.g. appropriateness of route-to-route extrapolations). `The PRG concentrations presented in the table can be used to screen pollutants in environmental media, trigger further investigation, and provide an initial cleanup goal if applicable. When considering PRGs as preliminary goals, residential concentrations should be used for maximum beneficial uses of the property. Industrial concentrations are included in the table as an alternative cleanup goal for soils,but is not recommended that industrial concentrations be used as for screening sites'. In response to an AGE inquiry, a representative of the California Department of Toxic-Substances Control(DTSC) could not offer an opinion of the DTSC's level of concern with the concentrations detected without careful review of the sampling methods, location, etc. Based on'the assumptions of probable source localities, interpreted method of deposition, sample localities, and contaminant concentrations encountered,AGE believes that the hexavalent chromium concentrations encountered in the shallow soil samples are representative ofthe actual concentrations remaining in place and that remediation and/or cleanup of the.impacted soil is not likely to be required. 6.0. SUMMARY AND CONCLUSIONS AGE has assessed soil on the subject property potentially impacted by a fonner gasohol operation for hydrocarbons in the gasoline range, BTEX compounds and ethanol. The areas assessed were known or suspected to have been utilized in the production of gasohol on the site in the late 1970s and early 1980s. Features investigated included the distillation unit area, suspected or known AST sites,the known and suspected sump sites, and the old and new pond areas.In addition,the areas of two former cooling towers have been assessed for hexavalent chromium. Low concentrations of hydrocarbons quantified as gasoline were detected in two samples. One of the samples collected on the north portion of the property near a former large AST also contained a low concentration of ethanol(0.8 mg/kg).Additional-samples collected in the area did not contain detectable concentrations of hydrocarbons. AGE found no connection to -any of the suspected contaminant sources or other evidence that the encountered hydrocarbons-are likely to be part of a significant release in the area. The second sample with detectable concentrations of hydrocarbons iri the gasoline range, Advanced GeoEnvlronmental,Inc.