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San Joaquin County <br />Environmental Health Department <br />1868 East HazeIton Avenue <br />Stockton, California 95205-6232 <br />DIRECTOR <br />Donna Heran, REHS <br />PROGRAM COORDINATORS <br />Robert McCleflon, REHS <br />Jeff Carruesco, REHS, RDI <br />Kasey Foley, REHS <br />Linda Turkatte, REHS <br />Rodney Estrada, REHS <br />Adrienne Elfsaesser, REHS <br /> <br />Website: www.sjgov.orgIehd <br />P hone: (209) 468-3420 <br />Fax: (209) 464-0138 <br />September 5, 2014 <br /> <br />Mr. Brian Waite <br />Chevron Environmental Management Company <br />6101 Bollinger Canyon Road <br />San Ramon, California 94583 <br />Subject: <br />Dear Mr. Waite: <br />Former Chevron Service Station No. 98632 <br />575 West Grant Line Road <br />Tracy, California 95376-2551 <br />sEp 10 14 <br />ikteNe" <br />The San Joaquin County Environmental Health Department (EHD) has received and reviewed <br />Low-Threat Closure Evaluation (LTC Evaluation), dated 19 June 2013, and First Semi-Annual <br />2014 Groundwater Monitoring Report (2014 GWMR), dated 28 July 2014. Both reports were <br />submitted by your consulting firm, Conestoga-Rovers & Associates (CRA), on your behalf for <br />the above-referenced site. <br />In 2013 and in 2014, the EHD evaluated the site for possible closure under the Low-threat <br />Underground Storage Tank Closure Policy (LTCP) utilizing the LTCP checklist; the 2014 <br />evaluation currently is available for public review on the State Water Resources Control Board <br />(State Water Board) GeoTracker website. In 2014 GWMR, CRA listed the criteria that were <br />identified by the EHD as not being met as follows: <br />General Criteria, item f — Secondary source has been removed to the extent practicable; <br />Media Specific Criteria: Petroleum Vapor Intrusion to Indoor Air; and <br />Media Specific Criteria: Direct Contact and Outdoor Air Exposure. <br />In 2014 GWMR, CRA stated that the LTCP criteria listed above had already been addressed in <br />LTC Evaluation. Specifically, in response to the first bulleted criterion above, CRA indicated in <br />LTC Evaluation that the secondary source had been removed to the extent practicable, stating <br />that: <br />"Remedial excavation in 1994 removed approximately 650 cubic yards of impacted soil <br />from the former source areas (Figure 2) that was either disposed offsite or aerated and <br />re-used as backfill onsite. Based on overall stable to decreasing concentrations in <br />groundwater, there does not appear to be significant secondary source material <br />remaining that would change these trends." <br />Regarding the second bulleted LTCP criterion, CRA stated in LTC Evaluation: <br />"Although the detected concentrations in soil vapor and soil do not satisfy the <br />characteristics of Scenario 4 of criteria (a) above, under the current land use scenario <br />the site should be considered low threat as there appears to be no significant risk to <br />02A