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CRYSTAL CREAMERY STOCKTON WKA No. 1628.10 March 12, 2002 Page 2 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-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. All water removed during sampling and purging operations was sealed in labeled 55-gallon drums and stored on site. Findings Groundwater elevations beneath the site ranged from—4.86 to—5.78 feet below mean sea level (msl). The groundwater gradient varied across the site but was on the order of 0.003 feet/foot, with flow towards the northeast. Cumulative groundwater elevation data is summarized in Table 1. Groundwater contours are presented on Plate 2. Groundwater samples from wells MW2,MW3,MW7 and MW8 had no detectable concentrations of TPH as gasoline or BTEX. TPH as gasoline was detected in groundwater samples from wells MW1 (100 pg/L), MW4 (3 60 µg/L) and MW5 (10,000 µg/L). BTEX was detected in MW4 and MW5. Benzene was detected in wells MW4 and MW5 at concentrations of 5.2 pg/L and 2,200 µg/L,respectively. Trace concentrations of MTBE were detected in wells MWl (1.2 pg/L), MW3 (1.1 pg/L) and MW6 (1.2 pg/L). Trace concentrations ofTert-Butanol were also detected in well MWl- Cumulative analytical results are summarized in Table 2. Laboratory analytical reports and Chain-of-Custody documentation are included in Appendix A. Conclusions Groundwater in the vicinity of wells MW4 and MW5 continues to be impacted with gasoline and BTEX. Down gradient wells MW7 and MW8 continue to be free of gasoline, BTEX and fuel oxygenates. Concentrations of TPH as gasoline in well MWl have decreased significantly since 1992,but have been relatively stable for the last two years. Trace concentrations of MTBE were detected in wells MW1, MW3 and MW6. Review of past data reveals no specific trend with regard to TPH as gasoline concentrations in wells MW4 and MW5. Limitations The statements and conclusions in this report are based upon the scope of work described above and on observations made on the date of our fieldwork as presented above. Our work was WALLACE•KUHL ti.,, &ASSOCIATES INC.