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o 16112/1995 26:44 9163519357 ANNE M FARR PAGE 66 The unhappy result is that the estimated concentrations of MTBE and gasoline in a sample are not really comparable,except as apples and oranges. In the future we will be concentrating on elimtnatingtbis source of confusion in analyucal results. Case Studies of MTBE/Gasoline Plumes in Maine Our rust case in Maine was in a rural part of North Berwick in the southwestern pan of-he state The case was discovered in mid-1984, and for several reasons is thought to have been a recent spill A farmers tank was found to have been lealung product directly into the fractured 1 schistose bedrock_ Due to the configuration of the bedrock surface, the product plume was t located on the other side of the road. about 150 feet away from the tank (Fig. 4) Product recovered from the pump hose and from the product plume was chromatographically identical. and found to be a leaded gasoline containing about 396 MTBE by volume. The first household to receive contaminated water was the farmer's neighbor across the road, whose 80 ft deep drilled well rather suddenly produced water contaminated with 126,000 Fart per billion oral gasoline including MTBE. Because the spill occu:rcd scar the crest of a ridge, the dissolved plume spread in two directions downslope. Wtthfn months other homeowners only a few hundred yards from the spill site were complaining of water smelling not of gasoline, but of "a funny chemical smell". Two years later and with the plume either stable or enlarging only slowly, most of the plume was an MTBE only plume occurring as a halo around the dissolved gasoline plume (Fig. 4). Water from some wells has been analysed as containing as much as 690 parts per billion MTBE with no detectable gasoline, Table 2 summarizes analyses from a recent sampling run of the nwnitonng wells on the north side of the hill. Table 2: Analyses of MTBE and Gasoline from wells at the Cabbage Hill site 4 in North Berwick, Maine (July, 1986). II Well #I Location Gasoline 11tTBE' (see Fig. 4) (ppb) (ppb) 1 s Plume "hot spot",at water table 304,069 236,250 1 d same, at 60ft depth 4.383 8,941 3 edge of product plume _ 48.543 45,800 I 2 200 feet downgradient _ 6,494 7.534 3 600 feet downgradient 53 219 4 also 600 feet downgradient nd 593 6 750 feet downgradient nd 197 ' note that quantification of gasoline and MTBE can only be compared like apples and oranges (sec previous section). However,it should also be noted that the chromatograms for samples from wells 1-3 show large concentrations of the marry other components of gasoline. much larger than is logically deduced by subtracting the MTBE concentranon from the gasoline concentranon. I I X33