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V CRYSTAL CREAMERY STOCKTON WKA No. 1628.10 August 20, 2003 Page 2 gasoline(TPHg),Benzene, Toluene, Ethylbenzene and Total Xylenes (BTEX), Tert-Butanol, Methyl tert-Butyl Ether, Di-isopropyl Ether, Ethyl tert-Butyl Ether, and Tert-Amyl methyl Ether (oxygenates)using EPA Method 8260B. The submersible pump was cleaned with a solution of Liqui-noxg and water before purging each well to minimize the potential for cross-contamination. In addition,the wells were sampled in order of increasing concentration based on previous sampling results. Well purging data sheets are included in Appendix A. All water removed during sampling and purging operations was sealed in labeled 55-gallon drums and stored on site. Ozone Injection System Operation An ozone injection system and ten injection wells were installed at the site during the third quarter of 2002 (see Plate 2). Operation of the system commenced on July 18, 2002. Ozone injection was intennittent during the remainder of the third quarter of 2002 as bugs were worked out of the system. The system has been operating on a nearly continuous basis, however, through the second quarter of 2003. r Findings Depth-to-groundwater measurements at the site ranged from 15.75 to 16.40 feet below top of casing during the June 4, 2003 monitoring event. The calculated groundwater flow direction for the monitoring event was toward the northeast(see Plate 2)with a hydraulic gradient of 0.005. Cumulative groundwater elevation data is summarized in Table 1. Time plots of groundwater elevations (and TPH gasoline concentrations)for wells MWl, MW4, and MW5 are presented in Charts 1,2, and 3, respectively. With only minor exceptions,none of the target analytes were detected in samples from wells MW1, MW2, MW3, MW6, MW7, and MW8 during the second quarter of 2003. Wells MW4 and MW5 continued to show elevated concentrations of BTEX compounds and TPH as gasoline. Cumulative analytical results are summarized in Table 2. Time plots of TPH gasoline concentrations (and groundwater elevations) for wells MWl, MW4, and MW5 are presented in Charts 1, 2, and 3,respectively. Laboratory analytical reports and Chain-of-Custody documentation are included in Appendix B. .r NNW V WALLACE-KUHL w,,, &ASSOCIATES INC.