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1 6.2 Extent of Groundwater Contamination f The groundwater, which starts at seven feet below grade, is impacted with petroleum products. Four monitoring wells were installed. MW-1 is located 40 feet northwest of the tank site, MW-2 is located 60 feet southeast of the tank site, MW-3 is located 40 feet south of the tank site, and MW-4 is located 10 feet north of the tank site. MW-2 and MW-3 have remained non detect for TPH-G during the different sampling periods. MW-1, which was positive for TPH-G, has shown a slight decline in levels from 200 ppb, to 170 ppb, to 160 ppb. MW-4 has the heaviest concentrations of TPH of all the existing monitoring wells. It has also shown a decline from free product in 1992, to 4500 ppb and then 4100 ppb in 1993. Water samples were also taken from sax of the seven soil borings. Sample results found no contamination at 60 feet north of the tank site (BH-1) and 20 feet east of the tank site (BH-3). Contamination was observed 10 feet east of the tank site at 3100 ppb of TPH (BH-2) , 30 feet west of the tank site at 20,000 ppb TPH (BH-6), 10 feet northwest of the tank site at 160,000 ppb of TPH (BH-4) , and 10 feet southwest of the tank site at 300,000 ppb of TPH (BH-5). I 7. 0 PROPOSED REMEDIATION WORK PLAN 71. Soil Contamination Pacific Ram Environmental proposed to remediate the contaminated soils at the same time as the site will be characterized. Appendix III shows the suspected area contaminated. Soil boring BH-3 and BH-7, which were non detect, are on the edge of the suspected area and they define the outh&rn and western lateral_ extent of the soil plume. The soil area north and west of the tank ate have not been fully characterized. `��^ During the remediation of the soil plume an additional 60 borings will be constructed within the suspected contaminated area. Barings will first be constructed around the property boundaries. Soil borings will move toward the tank removal site, the suspected contaminated area, in ten feet increments. As soon as a detectable amount of contamination is observed, this boring will be marked as the lateral extent of the plume. Additional borings, at five feet increments, will then be constructed, as specified in the remediation plan. All i soil found inside the lateral boundaries of the plume will be considered contaminated and will be remediated. If soil borings indicate that the contamination is not coming from the tank excavation area, all construction of additional borings, or soil remediation will cease. Barings will then be constructed to determine the new location of the contaminants and this information will be detailed in the Site Assessment Report. 7. 2 Water Contamination Pacific Rim Environmental have agreed to remediate the contaminated groundwater at the same time as the site will be characterized. Appendix III shows the suspected areas of water contamination. Since the existing monitoring wells MW- 2 and MW-3 are non detect, this will be rpnr-th and eastern extent of the ,�� contaminated plume. M-1 will be considered the western ex ent of the plume. MW-1 is not at non detect, but since it is on the edge of the property lane, it� should be assumed that the plume is not traveling in this direction. 3