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L� June 1993 Quarterly Groundwater Sampling & Analysis Worki%psfe for 9Nafure Quik Stop Market No. 132, Stockton, California F7132.93 a clean PVC-extension. During the pumping, water in the well is kept at a low level by periodic pumping over a period of about 3 hours. Previous measurements indicate that pumping for 3 hours removes approximately 200 gallons of groundwater. Groundwater samples are obtained prior to and at the completion of pumping. The groundwater samples are collected following the procedures outlined in the RESNA groundwater sampling protocol (Appendix B). The samples are transported to a state-certified laboratory and analyzed for TPHG and BTEX. The results of these analysis are included in Table 1. 1 In an effort to further delineate the off-site extent of contamination, RESNA and Quik Stop Markets, with the approval of SJCPHS, elected to conduct a soil gas and shallow groundwater survey along the eastern side of the Taco Bell site and that portion of West Hammer Lane which fronts the Taco Bell site. This survey was conducted on April 29, 1992 with a specially equipped van operated by Tracer Research Corporation (Tracer) of Tucson, Arizona, under the direction of a RESNA geologist. The results of this survey indicated that the contamination detected in the upper aquifer did not extend into the areas investigated in this survey (RESNA, July 1992). In view of the information obtained in the Tracer survey, RESNA recommended the installation of two groundwater monitoring wells on the Taco Bell property. It was clear that obtaining access for the installation of two groundwater monitoring wells on the Taco Bell property would require the assistance of the SJCPHS. Scheduled quarterly groundwater sampling and analysis were continued. In our June 1992 quarterly report (RESNA, October 1992) RESNA recommended that on the basis of an established history of nondetectable TPHG and BTEX the sampling frequency for wells MW-3 and MW-4 be reduced from quarterly to semi-annually. In a letter dated November 17, 1992 to Mr. Jack Griffith of Quik Stop Markets the SJCPHS approved the semi-annual sampling and analysis of these two wells. In November 1992, with the assistance of the SJCPHS, RESNA was granted permission to enter the Taco Bell property and install 2 groundwater monitoring wells. These monitoring wells, designated MW-6 and MW-7, were installed on December 9, 1993. Subsequent laboratory analysis of the soil and groundwater samples collected from MW-6 and MW-7 found that TPHG, BTEX, and fecal coliform were not detected,in either well (RESNA, ' January 1993). On the basis of data gathered from the installation of these two wells and the December 1992 Quarterly Groundwater Sampling and Analysis, RESNA made the following recommendations: • Sampling and analysis of monitoring wells MW-3 and MW4 be discontinued. Quarterly measurement of groundwater elevations will continue. t • Analysis of groundwater samples for fecal coliform be discontinued. • Add monitoring wells MW-6 and MW-7 to the array of wells monitored quarterly. A-3