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CRYSTAL CREAMERY STOCKTON WKA No. 1628.10 January 8, 2003 Page 2 V gasoline(TPHg),Benzene, Toluene, Ethylbenzene and Total Xylenes (BTEX), Tert Butanol, ,r Methyl tert Butyl Ether, Di-isopropyl Ether, Ethyl tent-Butyl Ether, and Tert-Amyl methyl Ether (oxygenates)using EPA Method 8260B. The submersible pump was cleaned with a solution of Liqui-nox® 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. Operation of the system commenced on July 18, 2002. Ozone injection was intermittent during the remainder of the third quarter as bugs were worked out of the system. The system operated on a nearly continuous basis,however, during the fourth quarter of 2002. Findings Depth-to-groundwater measurements at the site ranged from 15.31 to 17.00 feet below top of casing during the three monitoring events. The calculated groundwater flow direction for all three monitoring events varied across the site,but was generally toward the northeast. Hydraulic gradients were in the range 0.003 to 0.005. Cumulative groundwater elevation data is summarized in Table 1. Time plots of groundwater elevations(and TPH gasoline concentrations) for wells MW1, MW4, and MW5 are presented in Charts 1, 2, and 3, respectively. Calculated groundwater flow directions for the second, third, and fourth quarters of 2002 are illustrated on Plate 2. With only minor exceptions, none of the target analytes were detected in samples from wells MW2, MW3,MW6, MW7, and MW8 during the past three quarters. Samples from MWl showed low concentrations of TPH as gasoline, MTBE, and TBA during the second quarter of 2002,but none of the target analytes were detected in that well during the third and fourth quarters of 2002. Wells MW4 and MW5 continued to show elevated concentrations of BTEX compounds and TPH as gasoline during the three monitoring events. Cumulative analytical results are summarized in Table 2. Time plots of TPH gasoline concentrations(and groundwater WALLACE•KUNL Gr ASSOCIATES INC.