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P.O. Box 576981-6981 <br /> Kloberdanz & �,ssociates Modesto, California 95357 <br /> Environmental Assessment Phone: (209) 557-8186 <br /> Fax: (209) 577-8158 <br /> September 2, 2002 <br /> 1151E,1::�I[E�,WEE) <br /> Ms. Lori Duncan, Senior REHS <br /> Mr. Nuel C. Henderson Jr.,R.G. SEP 13 2002 <br /> LOP/Site Mitigation Unit IV <br /> San Joaquin County Environmental Health Department ENVIRONMENT HEALTH <br /> 304 East Weber Avenue, Third Floor PERMIT/SERVICES <br /> Stockton, CA 95202—2708 <br /> RE: McDowell and Davis Towing, 1360 Escalon Ave,Escalon, CA 95320—Site# 1486 <br /> This letter response is being submitted in response to the San Joaquin County <br /> Environmental Health Department review letter dated August 6, 2002. The review letter <br /> requested the following site information use evaluation of the Risk Assessment: <br /> 1) Contaminant sources <br /> 2) Contaminant masses released <br /> 3) Potential contaminant migration pathways <br /> 4) Residual contamination <br /> 5) Data and method used for calculating volumes and average concentrations of <br /> impacted media and resultant calculated contaminant mass. <br /> 6) Sources and ranges of default values used in the RBCA modeling. <br /> San Joaquin County Environmental Health Department further noted that the current <br /> onsite use of the property involves the use of gasoline fuels and solvents, which, in all <br /> probability, exceed the estimated 0.0041 mg/m3 benzene concentration predicted by the <br /> model and requested reevaluation of the risk assessment conclusions in light of current <br /> site usage. A work plan for soil vapor sampling to confirm the soil vapor impacts <br /> predicted by the model, if appropriate,will be submitted under separate cover. <br /> Each of the information requests is addressed below and, where appropriate, text <br /> locations referenced in the Risk Assessment Report. <br /> Contaminant Sources - Contaminate sources are described on page 1, section 1.1, Site <br /> Description and History, as the former tank pit and former dispenser area. The source <br /> location identification was based on the detection of MTBE, TBA, and xylenes in the <br /> former tank pit and TBA and xylenes in the former dispenser area. To our knowledge, <br /> there is no record of releases or failed UST integrity tests for the facility. <br />