SITE INFORMATION AND CORRESPONDENCE

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Ms.Lori Duncan January 19,2011 RE:2911 E.Fremont St,Stockton,CA Page 5 of 6 Table 2 summarizes analytical results of groundwater samples collected near the inactive clarifier. Attachment 2 contains a copy of the laboratory report. Conclusions Based upon the analytical results of soil samples collected at the site, soil beneath the clarifier has been impacted by low to moderate concentrations of petroleum hydrocarbons and chlorinated solvents. The area of impacted soil appears to be less than 15 feet in diameter and extends to a depth of between 30 and 35 feet below ground surface, containing an estimated 650 pounds of residual gasoline constituents. Naphthalene was previously detected at a concentration as high as 29 mg/kg(Krazan,April 2010),which exceeds its Preliminary Remedial Goal(PRG)of 4.2 mg/kg for soil in an industrial setting,as established by the US EPA, Region 9. Only low levels of PCE were detected in groundwater,at levels below the Maximum Contaminant Level (MCL) of 5.0 µg/L. Based upon the lack of contaminants in boring LPB-4, located east of the clarifier and near the former waste oil UST,it does not appear that the documented contamination is related to the former USTs that were removed from the site in the early 1990s. Recommendations Due to the presence of an estimated 650 gallons of residual gasoline beneath the site, including naphthalene at levels above its PRG, additional actions are warranted. Options to consider include: 1. Conduct a site specific risk evaluation to determine if the site should be recommended for closure as a low-risk contamination case; 2. Evaluate potential remediation alternatives, such as soil excavation and disposal or in-situ remedial alternatives. Due to the low levels of PCE in groundwater, remedial actions related to groundwater do not appear warranted. 10759-SUMMARY LTR