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Former Shell-branded Service Station Page 2 <br /> 1160 West Yosemite Avenue September 17, 2010 <br /> Manteca, California 95337 <br /> [ESLs were not available for TPH-g and tertiary-butyl alcohol (TBA)], the ESLs listed in <br /> Appendix 1, Table E-1 b are no longer supported by the SFBRWQCB, and the CRWQCBCVR <br /> no longer uses soil concentrations for soil vapor screening levels. The EHD did compare the <br /> highest soil concentration of TPH-g (340 mg/kg) detected at this site to the current ESL for <br /> TPH-g taken from Screening for Environmental Concerns at Sites with Contaminated Soil and <br /> Groundwater (Interim Final — May 2008) published by the SFBRWQCB, and the soil <br /> concentration exceeded the ESL for gross contamination and direct exposure. <br /> Please address the concern that impacted soil gas may be entering the nearby buildings <br /> through cracks in the foundation or through utility conduits, as well as the above-listed <br /> concerns and demonstrate that soil vapor intrusion is not a problem at this site so that the <br /> EHD can continue to consider this site for closure. In particular, include a technical rational for <br /> discounting a significant health risk or hazard from vapor intrusion into the eastern building <br /> now overlying the uncharacterized former UST pit. if additional data are required to make the <br />,r evaluation, submit a work plan to acquire the needed information. <br /> Please collect groundwater samples from all five monitoring wells and analyze the samples for <br /> TPH-g, BTEX, TBA, and 1,2-dichloroethane (1,2-DCA) during the fourth quarter 2010. Make <br /> appropriate corrections to Site Investigation Report, dated 8 February 2008, and resubmit to <br /> GeoTracker—the State Water Resources Control Board database program. <br /> Please contact Vicki McCartney at (209) 468-9852 or by e-mail at vmccartne sjcehd.com if <br /> you have any questions regarding this letter. <br /> Sincerely, <br /> Victoria L. McCartney, RENS Nuel C. Henderson, Jr., PG <br /> Senior Registered Environmental Health Specialist Engineering Geologist <br /> c: Ms. Ann Rosecrance, Conestoga-Rovers & Associates, 5900 Hollis Street, Suite A, <br /> Emeryville, California 94608 <br /> Mr. .lames L.L. Barton, PG, California Regional Water Quality Control Board Central <br /> Valley Region, 11020 Sun Center Drive, Suite 200, Rancho Cordova, California 95670 <br />