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Quik Stop Markets,Inc. RACAMA 1 Project No. F7132.32 Working To Restore Nature r Page 2 of groundwater removed from each well is noted on the groundwater sampling field log included in Appendix C. Quarterly Well Pumping As agreed upon with the San Joaquin County Public Health Services (see Background' Section— Appendix A),monitoring well MW-5 is pumped out on a quarterly basis. This quarter, pumping was conducted on May 5, 1992. Prior to pumping a groundwater sample was obtained from the well and labeled MW-5. The well was then pumped for about three hours and approximately 200 ' gallons of water was removed from the well. After pumping was complete, another groundwater sample was collected and labeled MW-5A. Laboratory Analyses The groundwater samples were transported to RESNA Environmental Laboratories, a state- certified laboratory, located in Fremont, California. Samples were analyzed for the presence of TPHG following Environmental Protection Agency (EPA) Method 8015 modified and BTEX following EPA Method 80201602. The laboratory analytical report and chain-of-custody document are attached in Appendix D. ' Summary of Results A summary of the analytical results from current and past well samplings is presented in Table 1. Plate 2 shows the groundwater elevation contours based on the water, level data in Table 1. Groundwater elevations declined an average of 0.36 feet since last quarter. The apparent groundwater flow direction remains to the east-southeast at a gradient of approximately 0.002. ' In the Mune quarterly monitoring of wells MW-1R, MW-2,,MW-3, and MW-4,TPHG and BTEX were not detected. ; MW-5i had detectable levels of TPHG and benzene at 650 parts per billion and 2.9 ppb, respectively.- Unknown solvent peaks were reported hi d by the laboratory for groundwater-samples from.MW-1R and'MW-5. An examination of'i&'c. ma[ograms revealed ;that these.solvent-peaks-closely resembled those associated with methyl-tent-butyl ether (MTBE). ' MTBE is a non-metallic (lead-free)antiknock compound used in lead-free gasoline. In the next sampling and analysis, the samples from MW-1R and MW-5 will be analyzed for MTBE. The next quarterly groundwater sampling will be conducted in September 1992. ' Analysis of the samples-collected before and after the May 5, 1992 pumping of MW-5detected i TPHG at a concentration of..610 ppb pnpr-to pumping and at a concentration-of 360 ppb after; ,;pumping was completed(See Table 1). Recommendations Monitoring wells MW-3 and MW-4 have not had detectable TPHG or BTEX since they were first sampled in September 1990. MW-3 is located upgradient of the spill location and MW-4 is located approximately 50 feet laterally from the spill location. In view of these factors,in compliance with the State of California Leaking Underground Fuel Tank (LUFT)Field Manual, 1989, page 61, it is the recommendation of RESNA that Quik Stop request a change in the sampling schedule of