Exxon Mobil Corp. reported last night that the underground storage tank equipment at a Fallston service station has passed a stringent test for fuel vapor seepage, but a state official questioned the significance of the results.
The company sent the results of the "tracer test" to the Maryland Department of the Environment yesterday. The department is investigating the contamination of 169 wells near the station, at Routes 152 and 165, by the gas additive methyl tertiary butyl ether, or MTBE.
Exxon spokeswoman Betsy Eaton said the test showed the station's underground fuel storage system is in compliance.
"What it shows is that when the test was performed, the system was tight," she said. "The purpose of the test was to determine if any leaks exist, to ensure that this is a top operating system, and that's what it showed."
MDE spokesman Richard J. McIntire said the test, which was required by the agency, did not necessarily absolve the storage tanks of a role in the contamination.
Before the test
He said that before the test, by Praxair Services Inc. of Tucson, Ariz., preliminary checks found small potential leaks in fittings and pumps close to ground level that needed to be tightened before examination of the tank system deeper underground could begin.
Praxair said that if those spots hadn't been tightened, leaks there could have interfered with testing the buried system.
But McIntire said it was possible that those spots tightened before the test could have been a source of the original leakage.
"If there were loose areas that needed to be tightened up, it does perhaps indicate that they did have some degree of seepage," he said. "The way they stand right now, the system may be complete, but obviously they had to make some adjustments. ... It doesn't leave them fully blameless, in my opinion."
Fallston resident Tom Lusardi, who lives a half-mile from the station, urged the state to shut it down until the source of the leak is found.
"Today it passes [the test], but clearly compounds are in the ground and water, and there is a leak," Lusardi said. "They can operate in compliance today, but if the release occurred before, that release needs to be addressed."
MTBE, which is added to gas to help it burn more cleanly, dissolves easily in water and has contaminated groundwater in other states. It has caused cancer in rats that inhaled high doses, but its effects on people who drink small amounts is unknown.
MDE is conducting further investigation to determine the leak's sources, including looking at some possible causes other than the station.
McIntire urged patience from neighbors who say the state hasn't been aggressive enough in addressing the contamination since it was discovered two months ago.
"This is not an overnight, quick-fix kind of situation," he said. "Science takes time. A lot of time and money has been put into making sure this is done right."