SITE INFORMATION AND CORRESPONDENCE FILE 2

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San Joaquin County �0U'" Environmental Health Department DIRECTOR c 600 East Main Street Donna Heran, RENS -,z� �N t .. .'{ Stockton, California 95202-3029 PROGRAM COORDINATORS � - Robert McClellon. REHS - _ Jeff Carruesco, REHS, RDI C4' .—:.• �;�P Website: www.sjgov.org/ehd Kasey Foley. REHS �iFOR Linda Turkatte, REHS Phone: (209) 468-3420 Fax: (209) 464-0138 April 1, 2011 Mr. R. Ellis, Jr. Ms. Ethyl D. Ellis, Trustee et alia 1991 West Lincoln Road Stockton, California 95207-2462 Subject: California Tank Lines, Inc. 3105 South EI Dorado Street Stockton, California 95206 Dear Mr. Ellis.- The llis:The San Joaquin County Environmental Health Department (EHD) has reviewed Additional Site Investigation, Updated Human Health Risk Assessment and Natural Attenuation Analysis Report (Taber report), dated 21 January 2011, prepared by Taber Consultants (Taber), and California Tank Lines — Report of Investigation of Oil Removal from MW-2 (EI report), dated 18 January 2011, prepared by Environeering, Inc. (EI) on your behalf for the above-referenced site. The EHD also received and reviewed a Corrective Action Plan (CAP) letter (Taber letter), dated 18 March 2011, submitted by Taber. In the Taber report, results are presented from advancing soil borings GP-1 and GP-2, each to total depth of 50 feet below surface grade (bsg) north and south of monitoring well MW-4, and collecting grab groundwater samples (GP-1-GW and GP-2-GW). Soil was collected from both borings for lithological evaluation, and grab groundwater samples, analyzed for petroleum hydrocarbon contaminants, were reported to have concentrations of total petroleum hydrocarbons as gasoline (TPH-G) at 57 micrograms per liter (fag/L), benzene at 2.8 fag/L, and lead at 310 fag/L in grab groundwater sample GP-1-GW; and TPH-G at 61 pg/L, and lead at 83 fag/L in grab groundwater sample GP-2-GW. Based on these low concentrations of TPH-G and benzene detected in groundwater, the EHD believes the impacted plume is adequately defined north and south of MW-4. A revised Human Health Risk Assessment using the RISC4 — Risk Integrated Software for Clean-ups (RISC4) was included in the Taber report that incorporated groundwater results from the advancement of soil borings GP-1 and GP-2 presented above, and the first quarter 2010 sampling event on 11 February 2010. Although the RISC4 results from the calculated hazard quotient of 5.3 exceeded the target level of 1.0 for a child residing onsite, Taber notes that it is not likely that this site will be redeveloped for residential occupancy, and concludes that the "potential risks to human health associated with petroleum hydrocarbons remaining beneath the site to existing receptors are below target levels and that the site is a viable candidate for closure."