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.I � mow" � June 21, 1993 Working To Restore Nature !' ARCO Service Station No. 0548, Stockton, California SOIL BORINGS AND INSTALLATION OF MONITORING WELL On April 8 and 9, 1993, a geologist from RESNA observed Woodward Drilling of Rio Vista, California, drill five soil borings (13-15 through B-19) and construct one ground-water • monitoring well (MW-5) at the site. The locations of the borings and well are shown on Plate 2. The borings were terminated between 46-1/2 to 62 feet below grade. Soil samples were collected from the borings for possible laboratory analyses and to evaluate the geology beneath the site. The geologist logged the samples using visual and manual methods.and classified the samples according to the Unified Soii Classification System (Plate 3). Sediments encountered during drilling are shown on the Logs of Borings (Plates 4 through 14). The geologist also collected soil samples from the stockpiled drill cuttings for analyses to evaluate disposal options. Our field methods are described in an attachment to this report. Soil samples were submitted to Sequoia Analytical Laboratories (Sequoia) in Sacramento, California, which is certified by the State of California for the requested analyses (Hazardous Waste Testing Laboratory Certificate No. 1624). The samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg) and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) using Environmental Protection Agency (EPA) Methods 5030/8015/8020. Select soil samples were also analyzed for total oil and grease (TOG) using Standard Method 5520 E&F. Results of analyses are shown in Table 1 and indicate TPHg and BTEX were not detected in the samples collected from the borings, with the exception of one sample collected from 41.5 feet below grade in boring B-15. This sample contained benzene and total xylene isomers at concentrations of 0.024 and 0.018 parts per million (ppm), respectively. TOG was not detected in the soil samples. The soil samples collected from the drill cuttings were composited into two samples at the laboratory; one sample was analyzed for reactivity, corrosivity, ignitability, STLC lead, and TCLP BTEX, and the other soil composite was analyzed for TPHg and BTEX. Analytical results indicate TPHg, BTEX and lead were not detected,corrosivity was 8.3, ignitability was greater than 100 degrees Celsius and was not reactive with sulfide, cyanide, or water. Dillard disposed of the drill cuttings at BFI Landfill. SAMPLING BENEATH PRODUCT LINE On April 10, 1993, while clearing underground utilities, a product line was accidently fractured and according to the station manager subsequently leaked approximately 78 gallons into adjacent soil. To evaluate the impact of the leak, RESNA collected a soil sample from 6 feet below grade below the product line (S-6-PL1). This sample was submitted to Sequoia for analyses of TPHg and BTEX using EPA Methods 5030/8015/8020. . 0331ccar 30004-8 2 0'