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,i <br /> f r <br /> -3- <br /> Borehole Drilling. Oil February 17 , 1986, five boreholes, <br /> ` GL-1 through •GL-5, were drilled at- the Geweke Lodi site to <br /> identifythe vertical and lateral extent of h <br /> contamiation <br /> (Figure 17 . The locations of the <br /> edrocaosed <br /> boreholes were selected on the basis of: proposed <br /> the former underground storage tanks and (3 ) location 2of <br /> ) <br /> information pump islands, (2) <br /> the field work,gained from data review and preliminary stages of <br /> based on her recollection recommendation of a County representative <br /> ollection of where the tanks and pump islands <br /> were formerly located. On site with BC were representatives of <br /> - the County and the Regional Board. The county official was also <br /> on site during removal of the tanks. <br /> The boreho?.ef <br /> s were drilled using a Mobile B-40-L truck-- f <br /> mounted drilling rig equipped with 4-inch outside diameter, <br /> solid-stem, continuous-flight augers. Undisturbed soil samples <br /> were obtained from specific depths using a modified California <br /> drive sampler. Before <br /> and drilling each borehole, the augers <br /> all sampling equipment were cleaned to { <br /> cross-contamination between boreholes, PreVenPossible <br /> Groundwater Sample <br /> wells s .(Figure Tj were The four existing monitoring <br /> purged and sampled during the site <br /> investigation. Prior to sampling, <br /> - the monitoring wells with the depth to water 1 n the order s weremeasuin <br /> 44 <br /> _. feet. The groundwater gradient was to the southwest at 26.8 <br /> feet per mile. Water surface elevations and flow dir. <br /> shown on Fi urs 3_ ection are <br /> g Using a stainless steel bailer, three well <br /> casing volumes were removed from each well prior to sampling. <br /> Electrical conductivity, <br /> _ p ; i <br /> in Py, and temperature were monitored <br /> during purging.g• The stainless steel bailer was rinsed with 1 <br /> deionized water between wells in order to prevent cross- <br /> contamination. After three well casing volumes (roughly 7.5 <br /> gallons) were removed, two glass 40 milliliter <br /> organic analysis (VOA) vials were filled with samplem water.volatThe <br /> samples were turned over to the Regional Board representative on <br /> - site. The samples were <br /> est and <br /> transported to California Analytical Laboratory bychilled cthe hReginal � <br /> Board representative to be analyzed for BTX and TPH. Chain-of- <br /> custody forms were cr;mpleted for all samples. The analytical <br /> results are shown in Table I. <br /> le 7 also <br /> results from groundwater samples coblected by JBows BTX and TPHK. <br /> a <br /> t <br /> 3 <br /> , r <br /> :1 r <br /> ,i <br /> i <br /> e <br /> - tirre � <br />