SITE INFORMATION AND CORRESPONDENCE FILE 1

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`q San Joaquin County LnAronmental Health Department DIRECTOR Donna Heran, REFS 600 East Main Street Q: a Stockton , California 95202 -3029 PROGRAM COORDINATORS .. ... Robert McClellan, RENS Jeff Carruesco, REHS, RDI oq�ikoROR� P Website; www.sjgov. org/ehd Kasey Foley, REHS Phone : (209) 468-3420 Fax : (209) 464-0138 July 21 , 2010 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 San Joaquin County Environmental Health Department (EHD) has reviewed Work Plan for Updated Human Health Risk Assessment, Natural Attenuation Analysis and Additional Site Investigation ( Work Plan), dated 01 June 2010, prepared and submitted by Taber Consultants (Taber) on your behalf for the above-referenced subject site. The Work Plan was submitted following a meeting attended by personnel from California Tank Lines , Inc. , Taber, Environeering , Inc. , and EHD on 08 April 2010. Parties in attendance agreed that the work plan to advance three proposed off-site soil borings to the north and south of monitoring well MW-4 (approved by the EHD by letter dated 03 March 2010) would not be implemented and instead , a new work plan would be submitted by Taber. In Work Plan, Taber proposes to revise the Human Health Risk Assessment (HHRH) submitted to the EHD on 25 January 2010; perform a natural attenuation evaluation ; advance two soil borings north and south of MW-4 to delineate the petroleum hydrocarbon contamination in groundwater; install adsorbent socks in MW-2; and monitor the level of silt in MW-1 . It is unclear to the EHD how Taber proposes to revise the HHRA since the same software program [Risk Integrated Software of Clean-ups (RISCO)] that includes the Johnson and Ettinger Model and the Domenico Model will be used to evaluate the same potential exposure pathways as the original HHRH. Please clarify how the HHRA will be updated in conformance with Interim Guidance — Evaluating Human Health Risks from Total Petroleum Hydrocarbons (TPH), dated 16 June 2009 , prepared by the Human and Ecological Risk Division of the California Department of Toxic Substances Control . The EHD does recommend using the concentration of 14, 000 milligrams per kilogram (mg/kg) of total petroleum hydrocarbons (TPH) quantified as diesel (TPH-D) reported for soil sample TK1 -East at fifteen feet below surface grade (bsg) collected on 04 September 1998, instead of 2,300 mg/kg for soil sample MW-1 -20 collected on 04 December 1999; and the concentration of 140 micrograms per cubic meter (Ng/m3) of toluene reported for soil gas sample SV-2 collected on 15 June 2009 , instead of 42 Ng/m3 of toluene reported for soil gas sample SV- 1 collected on 15 June 2009 , when entering data into the RISC4.