SITE INFORMATION AND CORRESPONDENCE_FILE 2

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• 0 San Joaquin County °�'" Environmental Health Department DIRECTOR ._.��.CO Donna Heran, REHS 600 East Main Street v Stockton, California 95202-3029 PROGRAM COORDINATORS Margaret Lagorio,REHS =< 1,,, • -- ---- Robert McClellon,REHS Jeff cq ,., P Website: www.sjgov.org/ehd Kasey Foley, R REHS,RDI F o R d Kasey Foley, REHS Phone: (209)468-3420 Fax: (209)464-0138 December 17, 2009 Stephanie McKenna Chevron Environmental Management Company 6111 Bollinger Canyon Road, Ste. 3652 San Ramon, CA 94583 Subject: Unocal #0187/Chevron Site ID 306415 437 East Miner Avenue Stockton, CA 95202 The San Joaquin County Environmental Health Department (EHD) has reviewed Soil Vapor Investigation Report and Vapor Intrusion Pathway Evaluation (Report) dated November 19, 2009, submitted on your behalf by Arcadis and has the following comments. In the Report Arcadis discusses the results of vapor samples collected from recently installed soil vapor probes. The installation of the probes was reported in the previously submitted Site Assessment and First Quarter 2009 Groundwater Monitoring Report dated July 31, 2009. Vapor samples were collected from the probes on August 4-5, 2009. While a few of the deep probes located near known high concentrations of soil and groundwater contamination reported high concentrations of contamination in the vapor, Arcadis concluded that the results of the sampling indicate that there exists no potential vapor intrusion health risk from the site and recommends that no actions be taken to mitigate the contaminated soil vapor. This was the only recommendation included in the Report. In correspondence dated October 25, 2007 you were directed by the EHD to submit by December 10, 2007 an evaluation of feasible remedial alternatives to address the groundwater contamination remaining at this site. A proposal was submitted to conduct an MIP/CPT investigation to obtain additional data to design and test a biosparge system for remediation. The report of findings of the MIP/CPT investigation, which was submitted to the EHD in July 2008, was to include a detailed proposal for conducting a pilot test for a biosparge system, but it did not contain any proposals or recommendations. In correspondence dated August 22, 2008 the EHD directed submittal of a work plan to conduct a soil vapor study and the overdue feasible remedial alternatives testing. The work plan was due for submittal October 13, 2008. A work plan dated October 10, 2008 was submitted, but it included only a proposal for installation of soil vapor probes. Instead of including the overdue proposal for feasible remedial alternatives testing, Arcadis requested an extension for the submittal until completion of the soil vapor study. The EHD responded to this work plan in correspondence dated October 23, 2008, directing submittal of the overdue proposal for remedial feasibility testing within 30 days. It still has not been submitted.