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f THRIFTY OIL.. CO. January 19, 2005 0 53537 Mr Mike Infurna, Tr RWQ B #390652 Senior REHS Glob 05044County of San Joaquin Conflrma Public Health Services/Environmental Health Division 304 East Weber Avenue, 3rd Floor 1 yJAN 7 X019 E Stockton, CA 95202 pf IONM T HEALTH RE Former Thrifty Gil Co. Station 9172 CE$ Circle K Station #2705449 7647 Pacific Avenue Lp P Stockton, CA 95207 4th Quarter 2004, Status Report Dear Mr Infurna Presented herein is the Fourth Quarter 2004, Status Report prepared for former Thrifty Oil Co (Thrifty) Station #172 located at 7647 Pacific Avenue, Stockton, California(Figure 1) This report presents the results of the site monitoring and remediation system operation activities conducted during the fourth quarter of 2004 Thrifty has retained Earth Management Co (EMC) to conduct quarterly monitoring, sampling, and remediation activities at this site Groundwater Monitoring Depth to groundwater is measured in each monitoring well on a quarterly basis Gauging data obtained from June 1991 through November 10, 2004, is presented in Table 1. In general, groundwater occurs under the site at depths ranging from 34 97 feet below top of casing (btc) in monitoring well MW-6 to 40 38 feet bte in monitoring well MW-4 (Appendix A) A groundwater elevation contour map based upon November 10, 2004, data is presented as Figure 2 Groundwater appears to flow to the northwest/southwest at an approximate hydraulic gradient of 0 022 feet/foot This flow direction represents a reversal of flow direction from previous quarters A possible cause is that the system was turned off only one day in advance and the pumps were left in the wells unlike last quarter when the pumps were removed from the wells prior to monitoring Next quarter the pumps will be removed from the wells more than one day in advance to determine if this was the cause for the variation in flow direction Quarterly Groundwater Sampling As part of the groundwater-monitoring program, groundwater samples were obtained from monitoring wells MW-3 through MW-11 (except MW-8,which was abandoned) Groundwater samples were obtained by EMC on November 10, 2004, and delivered in a chilled state, in an ice chest, following strict Chain-of-Custody procedures to a state certified laboratory These samples were analyzed for volatile aromatic compounds benzene, toluene, ethylbenzene, and ixylenes (BTEX) and selected oxygenates (including MTBE) by EPA Method 826013, and for Q� 13116 Imperial Highway, Santa Fe Springs, CA 90670• (562) 921-3581