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elevations from the three groundwater monitoring wells. Soil samples will be analyzed for total petroleum hydrocarbons and MTBE. This information will be used to determine the extent of contamination and will aid in the design of remediation. 4.0 DISCUSSION 4.1 Waste Oil USTs S-P's Work Plan to determine the extent of contamination from two former waste oil USTs called for the installation of two bore holes; one upstream and one downstream from the tanks. S-P reported groundwater flow in a northeasterly direction to locate these two bore holes. The plan was modified in the field to include four bore holes, one of which was then r , converted into a groundwater monitoring well. Contamination from waste oil and gasoline l (TPHg, BTEX and MTBE) was found in both the soil and the groundwater samples. Bore Ir hole locations are shown in Figure 2 and the analytical results are listed in Appendix A, Table 1. A review of the analytical results indicates that, when the work was completed, soil contamination was generally confined to the area immediately adjacent to the two USTs. Groundwater contamination existed at all locations that were analyzed (MW-2, B-3 and B- 4). Soil contamination included both oil (TPHo) and gasoline, while groundwater contamination was confined to gasoline. Since this time, oil has reached the groundwater at MW-2, as evidenced by an attempted sampling in September 1998. Soil samples showed extremely little or no MTBE present. Slightly different results were obtained from the two analytical procedures — MTBE levels were either 0.06 ppm to 0.09 ppm or ND (detection limit = 0,005 ppm) depending upon which procedure is accepted. In any case, the low levels of MTBE in soil are generally consistent with the behavior of MTBE, BTEX and oil. MTBE sorbs only weakly into the soil and is very soluble in water (50,000 ppm versus 1780 ppm for benzene, the next most soluble component in gasoline). Oil sorbs more strongly in soil and is relatively insoluble in water. BTEX is located in between these two extremes. This results in partitioning of the various components between the soil and the groundwater. It seems reasonable to conclude that (1) the former USTs were the source of both used oil and gasoline contamination, (2) the extent of contamination in the soil has been determined and (3) the contamination in the groundwater has probably Environeering, Inc. Project No. 98-012.01 3