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June 25, 1992 • ARCO Service Station No 2076, Lodi, California PREVIOUS WORK w In October 1990, RESNA observed the drilling of three soil borings near the tank complex (tanks T1 through TS) and two soil borings east of the station building in the area designated as new tank cavity on Plate 2. The purpose of the work was to evaluate soil for possible residual hydrocarbons before the underground tanks were removed. Soil borings near the former tank cavity were terminated at 30 feet below grade because ground water was encountered Analyses of soil samples (Table 1) indicated concentrations of benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) were below 0 052 parts per million (ppm) in samples from borings B-1 and B-3, residual hydrocarbons were not detected in soil samples analyzed from borings B-2, B-4, and B-5 (Applied GeoSystems,December 18, 1990) In July 1991, we observed the drilling of three additional soil borings (B-6, B-7 and B-8) and �. installation of three vapor-extraction wells VW-1, VW-2, and VW-3 Boring and well locations are shown on Plate 2 The purpose of the additional work was to evaluate the feasibility of vapor extraction in the case remediation of soil is warranted in the future at ` the site Residual hydrocarbons were not detected in soil samples analyzed from borings B-6, B-7 and B-8 (Table 1). After installing the wells, we conducted a vapor-extraction test Results indicated vapor extraction is a feasible method of remediating soil at this site and vapor-extraction wells will produce an influence on an area with a radius of 30 feet (RESNA, September 12, 1991) FIELD WORK Field work performed by RESNA on behalf of ARCO at the site was conducted in accordance with our Interim Soil Remediation Work Plan dated September 16, 1991, and our Site Safety Plan dated August 26, 1991. The site safety plan, field procedures, and Chain of Custody protocol used during the investigation are discussed in Appendix A 3OM-3 2