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THRIFTY pIL C10 . <br /> July 13, 1999 <br /> Mr Michael J Infiirna Jr <br /> Senior REHS <br /> Site Mitigation Unit IV/LOP <br /> 304 East Weber St , Fifth Floor <br /> Stockton, CA 95202 <br /> RE Former Thrifty Oil Co. Station #171 <br /> 1250 North Wilson Way <br /> Stockton, CA 95205 <br /> 2nd Quarter Monitoring Report, 1999 <br /> Dear Mr Infurna <br /> Presented herein is the Second Quarter 1999 Monitoring Report prepared for Thrifty Oil Co Station <br /> #171 located at 1250 Wilson Way, Stockton, California(Figure 1) Presented in this report are the <br /> results of the quarterly groundwater monitoring program conducted on May 14, 1999 Thrifty Oil <br /> Co has retained the services of Earth Management Company (EMC) to conduct quarterly <br /> t monitoring and sampling activities at this site Field activities were recorded in the field reports, <br /> copies of which are presented in Appendix A <br /> GROUNDWATER MONITORING <br /> Depth to groundwater is measured in each monitoring well on a quarterly basis Gauging data <br /> obtained from November 1992 through May 1999 is presented in Table 1 In general, measurable <br /> groundwater occurs under water table conditions beneath the station at depths ranging from 38 64 <br /> feet below surface grade(bgs) in monitoring well TB-1 to 48 16 bgs in monitoring well MW-6 A <br /> groundwater elevation contour map based upon the May 14, 1999 data is presented as Figure 1 A <br /> groundwater mound occurs at monitoring well TB-7 The general groundwater flow is into a trough <br /> under the middle of the site which flows to the southeast <br /> QUARTERLY GROUNDWATER SAMPLING <br /> As part of the groundwater monitoring program, groundwater samples were obtained from <br /> monitoring wells MW-3R, MW-4, MW-5, MW-6, TB-1, TB-7, T13-8, and TB-10 Groundwater <br /> samples were obtained by EMC personal and delivered in a chilled state in an ice chest following <br /> strict Chain-of-Custody procedures to a state certified laboratory and analyzed for total petroleum <br /> hydrocarbons as gasoline (TPH-g) by EPA method 8015 modified, and for volatile aromatic <br /> compounds of benzene, toluene, ethylbenzene, and xylenes, by EPA method 8020 Benzene and <br />• TPH concentrations are contoured in Figures 2 and 3, respectively <br /> �Qd)j <br /> 13539 E Faster Rd,Santa Fe Springs,CA 90670-0138•(562)923-9876 <br />