Laserfiche WebLink
e. - a, ' -� 3' .x �, -},'-' ' '-z: <br /> � <br /> a <br /> yp ri•t" <br /> F <br /> I <br /> Subsurface Investigation December 12, 1990AGS 38012-5 <br /> Former Unocal Station No. 2859, Stockton, California <br /> In June 1988 Applied GeoSystems observed Datum Exploration Inc.of Pittsburg,California, <br /> drill borings B-1 through B-3 onsite and convert the borings to a ground-water monitoring <br /> wells MW-1 through MW-3. Our methods and results are reported in Applied GeoSystems, <br /> July 2'!, 1488. The well locations are shown on Plate P-2. During drilling,ground water was <br /> encountered at approximately 30 feet below grade. The wells were screened between 20 <br /> and 50 feet below grade. <br /> Laboratory results of soil samples collected at 25 feet below grade in borings B-1 and B-3 <br /> indicated TPHg and BTEX concentrations below detection limits for the methods used <br /> (Table 3). In soil samples collected at 20 and 25 feet below grade in boring B-2, 'rPHg <br /> concentrations ranged from 8 to 28 ppm and BTEX concentrations ranged from 0.10 to <br /> 13.99 ppm. <br /> We developed and sampled the ground water wells on June 6, 1988. Tlie geologist noted <br /> a sheen in the water collected from well MW-2 during the subjective analyses. <br /> Laboratory results indicated the concentration of hydrocarbons were below detection limits <br /> in samples collected from well MW-1 (Table 3). In water collected from well MW-3, the <br /> concentration of TPHg was reported as 170 ppb,benzene as 1.0 ppb, and total xylenes as <br /> 1.6 ppb. The concentration of toluene and ethylbenzene were below detection limits for the <br /> methods used. Laboratory results of water samples collected from well MW-2 indicated <br /> TPHg concentration of 99,000 ppb, and BTEX concentrations of 5,700, 48,800, 5,000 and <br /> 25,000 ppv, respectively. <br /> 7 <br /> AAP1/ed GeOSysteins — <br />