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1 Report on Additional Site Assessment and First Quarter 2000 Monitoring 3 7-Eleven,Inc,Store#21756 853 E Yosemite Avenue,Manteca CA February 21 2000 1 Nine soil samples (three from each monitoring well)(Table 1)were analyzed for BTEX, MTBE and ' TPH-G by EPA Methods 8015/8020 The soil samples were also analyzed for MTBE and other oxygenates were analyzed using EPA Method 8260 34 Groundwater Monitoring Well Installation/Surveying On December 20, 1999, three groundwater monitoring wells were installed in the three borings (MW-1, MW-2, and MW-3) at the locations shown on Figure 2 The groundwater monitoring wells were constructed of 2-inch-diameter, Schedule 40 polyvinyl chloride casing with flush threads, and ' 0 020-inch-slot well screen The well screen was installed in the three borings from 10 feet to 25 feet below grade Sand was placed in each well annulus from the bottom to approximately 2 feet above the ' top of the well screen The well annulus was sealed with approximately 2 feet of bentonite pellets saturated in place on top of the sand pack, and neat-cement grout to approximately 10 Inches bgs The wellheads are protected at the surface by locking, water-tight well caps and traffic-rated street boxes ' (with watertight bolted lids)set in concrete Well construction details are shown on the drill logs in Appendix A The top of casing and rim of each well box was surveyed by Morrow Surveying for horizontal position and elevation relative to mean sea level datum (Appendix B) 1 35 First Quarter 2000 Groundwater Monitoring and Sampling On January 25, 2000, depth to water in each well was measured to the nearest 0 01 foot from the top of the well casing using an interface probe (Table 2) Field data sheets are provided in Appendix C 1 Subsequent to monitoring, approximately four well volumes of water was removed from each monitoring well to ensure stabilization of pH, electrical conductivity, and temperature The purge water was stored in DOT-approved 55-gallon drums Prior to groundwater purging, dissolved oxygen was measured in each well using a field instrument The groundwater samples were collected using disposable bailers, then ' transferred to 40-milliliter glass vials filled to zero headspace and acidified to a pH of 2 The samples were sealed using Teflon&septum caps, labeled, placed on Ice In an insulated container, and ' transported under chain-of-custody to a state-certified laboratory for analysis The groundwater samples were analyzed for BTEX, MTBE and TPH-g using EPA Methods 80201modified 8015, and for MTBE and other oxygenates by EPA Method 8260 (Table 2) r s 1 r