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1 <br /> and conducting further tests on the storage tanks and abandoned <br /> barge lines that enter the facility from the Southern Pacific <br /> ' right-of-way. <br /> Sequence of Field Operations <br /> During the period February 29 , 1988, to March 11 , 1988, <br /> eleven exploratory test holes and two monitoring wells were <br /> installed at the Tesoro site (Figure 1) . The exploratory test <br /> holes were installed on three separate days, and the monitoring <br /> ' wells were installed last . The first five test holes (TS-1 <br /> through TS-5) were installed on February 29, 1988, around the <br /> tank farm in response to a request from the Central Valley <br /> Regional Water Quality Control Board (RWQCB) that Tesoro install <br /> boreholes to investigate potential sources of gasoline leakage at <br /> ' the facility. No free floating gasoline was observed in any test <br /> holes. in response to continued concerns of the RWQCB on March <br /> ' 2, 1988, Tesoro dug two additional test holes at the site (TS-6 <br /> t and TS-1 ) to determine if the gasoline leakage could be emanating <br /> from sources not previously assessed. No new free floating gaso- <br /> line was observed in the two test holes. The final four test <br /> holes (TS-8 through TS-11) were dug on March 9, 1988, to deter- <br /> mine if new gasoline was flowing onto the Tesoro site from <br /> sources to the north and west . Free floating new gasoline was <br /> ' initially found in two test holes (TS-9 and TS-10) that bordered <br /> the Time Oil property. Test hole TS-8 showed floating product <br /> three days following its installation. <br /> ' - 3 - <br />