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V Y i ATC Associates Inc. �. 1117 Lone Palm Avenue, Suite 201 Modesto, California 95351 209-579-2221 kTc Fax:209-579-2222 A S S O C I A T E S I N C . groundwater were the recommended remedial options. These options were rejected by the Central Valley Regional Water Quality Control Board (CVRWQCB) staff citing an absence of extensive field trial records for the groundwater remedial option selected and the likelihood of a significant permit process involving multiple regulatory agencies. ATC submitted the Feasibility Study Addendum, dated January 9, 2009, in which ozone infusion was recommended as a remedial alternative the site. The San Joaquin County Environmental Health Department (SJCEHD) agreed with the recommendation and requested that L groundwater samples from the site be analyzed for metals and the results evaluated and compared with nearby contaminated UST sites that were using, or conducting bench scale tests for ozone infusion. In correspondence dated April 20, 2009, the SJCEHD approved switching all site monitoring wells to a semi-annual monitoring schedule except for monitoring well MW-11, to which an annual schedule was prescribed. This monitoring schedule was prescribed until such time as more frequent sampling may be needed for monitoring remedial progress. This semiannual sampling regime is consistent with the State Water Resources Control Board (SWRCB) Directive 2009-0042 that required semiannual monitoring replace quarterly monitoring at petroleum UST sites under its jurisdiction in California except if otherwise justified. ATC submitted the Site Geology Comparison, dated September 24, 2009, that summarized data from four contaminated UST sites located within one mile of the subject property that had either conducted ozone infusion bench scale testing, were in the process of conducting ozone infusion for remediation, or had completed preliminary analysis of soil and groundwater for metals evaluation. This report also contained published industry research on behavior and reactions of metals in the subsurface and compared this information with similar information from the Eggiman site. ATC recommended an insitu pilot test, conducted with monitoring and contingency plans in place, to provide site-specific data for evaluation of the applicability of using ozone infusion to remediate the petroleum hydrocarbon contamination at the site. V In correspondence dated October 29, 2009, the SJCEHD agreed with the recommendation in the Site Geology Comparison and directed the submittal of a work plan for conducting an in-situ ozone infusion pilot test. SAMPLING ACTIVITIES On March 24 and 25, 2011, ATC personnel collected groundwater samples from monitoring wells MW1 through MW11 in accordance with the semi-annual monitoring schedule established in April 2009. The locations of the monitoring wells are shown on Figure 2. Prior to collection of �., groundwater samples, the depth to water was measured in each well and the pH, electrical conductivity, and temperature were measured in groundwater purged from the monitoring wells and recorded. At least three well casing volumes were purged from each well prior to sampling. The wells were allowed to recover and samples were collected from each well using a disposable bailer. The groundwater samples collected from each well were submitted to State-certified Argon Laboratories, Inc. (Environmental Laboratory Accreditation Program Certificate No. 2359) in Ceres, California for chemical analyses of TPHg, TPHd, and fuel oil utilizing EPA Method s:\environmental\22493\Reports\QMR 2011 SA1.doc 3 V