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Ij <br /> i <br /> i <br /> BASELINE ASSESSMENT REPORT <br /> Site Number 111910 <br /> 1205 East March Lane <br /> Stockton, California <br /> 14r <br /> 1 III <br /> 4. Supplemental Site Assessment Work <br /> EMCON used a PID to measure organic vapors in the h e dspace beneath the dispensers at <br /> each pump island on July 11, 1994. A reading of 0.3 ppm iwas measured at both the east and <br /> west dispensers at the north pump island, and a reading of'2.9 ppm was measured at the west <br /> dispenser at the south pump island. Soil samples were not collected beneath the dispensers. <br /> EMCON conducted supplemental assessment activities at ttie site on December 6, 1994. Four <br /> soil borings, TB-1 through TB-4, were drilled on the site;boring TB-1 was located west of the <br /> gasoline UST, and borings TB-2, TB-3, and TB-4 were drilled around the pump islands <br /> k <br /> (Figure A-1). Borings TB-1, TB-2, and TB-3 were drilled to approximately 20 feet bgs and <br /> boring TB-4 was drilled to 71 feet bgs. Native soils consisted of silty clay, silty sand, and sand <br /> down to 20 feet bgs, underlain by sand and clayey silt to 11 feet bgs. Groundwater was not <br /> encountered in any of the borings. A slight to strong hydrocarbon odor was noted in soil from I <br /> boring TB-4 between 15 and 30 feet bgs and again between 55 and 70 feet bgs. PID readings <br /> were taken every 5 feet; the highest readings were 112 ppm at 30 feet bgs and 84 ppm at <br /> 65 feet bgs. 1 <br /> EMCON submitted eight soil samples, collected at 10 and 20 feet bgs in borings TB-1, TB-2, <br /> and TB-3, and at 30 and 65 feet bgs in boring TB-4, for laboratory analyses. All soil samples <br /> were analyzed for TPH-G, TPH-D, TPH-O and BTEX. 11 <br /> P, le soil sample collected at 20 feet <br /> bgs from boring TB-3 was also analyzed for HVOCs. i!Laboratory Benzene (0.18 ppm), <br /> toluene(0.005 ppm),ethylbenzene (0.031 ppm), and xylenes(0.040 ppm)were detected in the <br /> soil sample collected from TB-4 at 65 feet bgs (Table A-1) In addition, xylenes (0.005 ppm) <br /> were detected in the soil sample collected from TB-2 at 20,feet bgs. TPH-O (up to 10 ppm) <br /> was detected in soil samples collected from TB-1 at 10 feet bgs, TB-3 at 10 and 20 feet bgs, <br /> and TB-4 at 65 feet bgs. <br /> I <br /> I <br /> i <br /> 4 <br /> Brr0S/RPT/11190RPTAI6-94/L.AM/smw:3 Rev.0,02/03/95 <br /> 0952-088.03 <br /> i <br /> i <br /> it <br />