SITE INFORMATION AND CORRESPONDENCE

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page 2,1645 Cherokee The work plan states that no definitive cleanup goals have been established for this site by any regulatory agency. The Regional Water Quality Control Board has listed target cleanup levels for groundwater contaminants in the Tri-Regional Guidelines;the target level established for diesel and kerosene is 100 micrograms per litre. In previous discussion with your consultant, SJC/EHD indicated the soil contamination should be addressed by calculating an estimated current contaminant mass, propose how much of that mass can be removed, and then evaluate when or if the mass then remaining in soil may impact groundwater,and if that impact would be at a concentration of concem. A calculation of the current contaminant mass has not been prepared. In recent discussion with BES they indicated they would prepare an estimate of contaminant mass remaining after the excavation. BES has proposed a target clean-up goal for soil of 750 mg/kg, but they did not provide a detailed explanation or calculation of how they determined this as a clean-up goal concentration. BES's statement specifically was: "Utilizing determining factors such as the presence of ecological receptors and site specific exposure pathways, and considering the residual contaminant mass and the threat potential of the contaminant to significantly impact groundwater,a realistic and reasonable remedial Site Specific Target Level can be established". However,.none of these 'determining factors'are then detailed for this site, or utilized in a fate and transport model or risk calculation. In discussion with BES,it was explained to SJC/EHD that the 750 mg/kg concentration was selected based on review of similar site situations throughout the central valley region, and was not specifically intended as a goal for the proposed excavation. BES noted in general terms that it was a contaminant level in soil that would degrade before it impacts groundwater; however, this conclusion has not been demonstrated. SJC/EHD approves the proposed destruction and re-installation of the four groundwater monitoring wells at this site. SJC/EHD approves the concept of the proposed interim remediation by excavation of contaminated soil defined by the geoprobe borings. Please note that before a final corrective action plan (CAP)can be approved for this site, a feasibility study comparing at least two remedial actions for their cost and ability to mitigate the effects of residual contamination must be prepared. The feasibility study and the CAP must be prepared using site speck data. Please proceed with submittal of a well destruction permit along with the required $60.00 permit fee,a well installation permit and$89.00 permit fee,and with scheduling the approved work. Forty- eight hours notice to SJC/EHD is required prior to all site fieldwork;a report of findings must be submitted to SJC/EHD within 60 days following completion of the work. If you have any questions or comments please call Lori Duncan at(209)468-0337. Donna Heran, REHS, Director, Environmental Health Department Lori Duncan, Senior REHS Nuel C. Henderson,Jr., PG LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV cc: James Barton, CVRWQCB David Solis, BES