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ask R R4 Working to Restore Nature During drilling of soil boring B-18, a product line was accidently fractured and product leaked into adjacent soil. RESNA collected a soil sample from 6 feet below the product line (S-6-PL1); gasoline hydrocarbons were detected in this sample. RESNA began monitoring the groundwater in wells MW-1 through MW-4 on October 30, 1991 (RESNA, June 26, 1991, Report 30004-4). Well MW-5 was added to the monitoring program in March 1993. Dissolved hydrocarbons have been detected in monitoring wells MW-1 and MW-5 since monitoring began. In March 1992, EA Engineering, Science, Technology (EA) observed removal of the oil- water separator/clarifier (EA Engineering, Science and Technology, August 1992, Report 80633.01). EA collected one soil sample from beneath the former oil-water separator and one sample from the concrete. Analytical results from the soil samples indicated that oil grease (quantified as total oil and grease [TOG]) was present. Concentration of volatile organic compounds, semi-volatile organic compounds and polychlorinated biphenyls were below detection limits. Total metals were also below detection limits with the exception of arsenic and barium which were detected at concentrations of 0.0051 and 0.12 parts per million (ppm), respectively (see Appendix A). On March 2, 1992, RESNA conducted a vapor extraction test (VET) at the site (RESNA, June 15, 1992, Report 30004-5). Results of the VET indicated that soil beneath the site can be remediated by vapor extraction and the evaluated radius of influence was 30 feet. SUPPLEMENTAL INVESTIGATION Field Work • On November 3, 1993, a RESNA field geologist observed Woodward Drilling of Rio Linda, California drill one onsite soil boring (B-20) and one offsite soil boring (B-21) to 46.5 and 60 feet bsg. Boring B-20 was converted to vapor extraction well VW-4, and boring B-21 was converted to well MW-6. Groundwater was encountered at approximately 47few Our • field methods are described in an Appendix B. The geologist collected soil samples from the borings at approximately 5-foot intervals for possible laboratory analyses and to characterize the geology beneath the site. Samples were logged using visual and manual methods and classified according to the Unified Soil Classification System (Plate 3). Sediments encountered are shown on the Logs of Borings (Plates 4 through 8). RESNA developed well MW-6 on October 8, 1993. Water samples collected after well development did not contain floating product or product sheen. Tom O. Morrow Inc. of l� 1213ccar/30004-5 2. c.