Effects of gasoline formulation on methyl tert-butyl ether (MTBL) contamination in private wells near gasoline stations

The extent of methyl tert-butyl ether (MTBE) contamination in private wells near gasoline stations, which lack the relative protection afforded many p ublic waters supplies through zoning;and routine testing, was examined. Sam ples were collected from 74 private wells near 21 randomly selected gasolin e stations and from 21 control wells, one per facility. Two hypotheses are tested: (1) private wells downgradient and close (<0.5 mi) to gasoline stat ions (case wells) are more likely to have MTBE contamination than private w ells upgradient and distant (>1.5 mi) (control wells); and (2) private well s near gasoline stations selling oxygenated gasoline are more likely to hav e MTBE contamination than private wells near gasoline stations selling conv entional gasoline. Data on the concurrence of MTBE and other gasoline const ituents are presented. Results: MTBE concentrations ranged from <1.0 <mu>/L (mu /L) to 61 mug/L, with a mean of 12.0 mug/L. MTBE contamination of grea ter than or equal to1 mug/L was detected more frequently in case wells (28% ) than control wells (5%) (p = 0.015). MTBE contamination of greater than o r equal to1 mug/L occurred more frequently in private wells near facilities selling oxygenated gasoline (38%) than private wells near facilities selli ng conventional gasoline (20%) (p = 0.11). Statistical significance may hav e been achieved with a larger sample size. Benzene (0.5 mug/L) was found co ncurrently with MTBE in only one well, which also had the highest concentra tion of MTBE.