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' Page 2,CAP,ARCO n=man below the ground surface EHD therefore requested further assessment of the extent of contamination ' ' 2.2 Soil Investigation Investigation of the extent of soil contamination began in October, 1992, when borings B-1 through B-4 were drilled(Figure 2) B-1 was located near the line leak to investigate the vertical extent of contamination, and was terminated at a depth of 60 feet B-2 through B-4 were drilled to depths of 30 or 40 feet to evaluate the lateral extent Logs of these bonngs are included in Appendix A Contaminated soil was encountered in B-1, B-2, and B-4 below a depth of 20 feet(Table 1) No contamination was encountered in B-3 or below 55 feet m B-1 The contaminated zone in B-1 consists mostly of sand and silt, with a gravel layer at approximately 35 feet Because the contaminated zone appeared to be suitable for in-situ remediation and because excavation and removal of the contaminated soil was not practical, B-1 was completed as a vadose-zone ' remediation well by the installation of perforated 2-inch casing between 55 and 25 feet Groundwater was encountered at 67 feet when the well was drilled Drill cuttings were stored on site in 55-gallon drums until December, 1993, when they were removed and disposed of by Geological Audit Services personnel 2.3 Groundwater Investigation ' Three groundwater monitoring wells (MW-1,MW-2, and MW-3) were installed in January, 1993 to determine whether the unauthorized release had impacted groundwater and to identify the groundwater flow direction at the site During drilling of MW-1, groundwater was noted at a ' depth of approximately 65 feet, and the well was screened from 63-78 feet In MW-2 and MW-3, groundwater was encountered at approximately 64 feet, and these wells were screened in ' the interval 50-70 feet The boring logs and well completion information are included in Appendix A Little or no soil contamination was detected collected while drilling these wells, which are apparently located beyond the limit of the soil contamination plume (Table 1) Gasoline and/or diesel and BTE&X compounds were detected in groundwater samples from each well in January and May 1993 Between May and August, 1993, groundwater rose to a ' depth of 52 feet, and by December 1993 to a depth of 51 feet Groundwater samples collected from MW-2 and MW-3 during those months contained somewhat lower concentrations of hydrocarbons than in previous months, and no hydrocarbons were detected in MW-1 (Table 2) The depth to groundwater has remained relatively constant since December 1993, and