As the investigation of groundwater contamination around Fallston drags on, residents of the Harford County community are questioning the Maryland Department of the Environment's handling of a problem that has troubled their area off and on since 1991.

Some fault state environmental regulators for failing to adequately investigate leaking fuel tanks in the area years ago, and they are asking why the Upper Crossroads Exxon service station has continued to sell gasoline, even though MDE has declared the station "at least partly responsible" for the gas additive methyl tertiary butyl ether, or MTBE, now found to be fouling 169 wells in the vicinity.

"People are just really infuriated that MDE hasn't done their job, that Exxon hasn't done their job," said Tom Lusardi, a geologist who lives about a half-mile northwest of the station. He says he has more than a decade's experience with environmental issues, including underground storage tanks. Though his well is clean, a neighbor's is tainted.

The scope of the contamination, meanwhile, continues to expand - as does information about other possible sources. An underground pipeline, which runs from Texas to New Jersey, snakes through the region, carrying millions of gallons of gasoline and other fuels. Also, inspectors recently found a trove of home heating oil tanks being cut up for salvage in a nearby yard.

Exxon Mobil Corp., which owns the station at Routes 152 and 165, contends the facility has been in full compliance with state regulations for preventing fuel leaks, and tests have not found any problems with the station's four underground fuel storage tanks or piping.

The company has yet to report on more sensitive testing it performed last month for possible seepage of fuel vapors into the soil and groundwater. Exxon Mobil expects to report this week on the testing, spokeswoman Betsy Eaton said Friday.

State officials did not respond to requests for comment late last week, although MDE spokesman Richard J. McIntire said in an e-mail Friday that the oil company would be sampling the soil at the station over the weekend as the investigation continues.

Station still open

Last month, Herbert M. Meade, head of MDE's oil control program, said the state would allow the Exxon station to continue operating as long as leaks could be quickly found and repaired.

"If not," Meade said at the time, "then, yes, we shut them down."

Lusardi and others contrast Maryland's apparent reluctance to close the Crossroads Exxon with a case in New Hampshire, where regulators ordered last month a Shell station believed to be contaminating nearby wells to find and fix the leaks in its tanks within 90 days or empty them of gas.

"If gasoline constituents have gotten into the groundwater, all we are looking for is to get the constituents out and make sure the tank is not leaking anymore," Lusardi said. But if authorities have been unable to find out exactly where the leak is, he added, "shut them down until you resolve the problem."

His views are shared by many others in the Fallston area, who have watched with growing frustration an investigation that has run, in fits and starts, since 1991 - but that most just learned of barely two months ago.

Among elected officials, Del. Joanne S. Parrott, a Republican who represents the area, said she thought the station should have been temporarily closed back in March, when a test detected 26,000 parts per billion of the additive in a pool of water beneath the station's fuel tanks. The state recommends consumers either filter their water or find another source when the MTBE level exceeds 20 parts per billion, since some can smell or taste it then.

MTBE has been added to gas to help it burn more cleanly since 1979, but its use was vastly increased in the early 1990s to curb air pollution in smoggy areas like Baltimore. It dissolves easily in water, and has contaminated groundwater in many states where MTBE-treated gas is sold. It has caused cancer in rats that inhaled high doses, but the health effects on people drinking relatively minute amounts is unknown.

According to a tally released last week by MDE, 11 wells around the Exxon station have MTBE concentrations in their water above the 20 parts per billion deemed advisable by the state. Another 158 have lower levels of the additive. The oil company has offered bottled water to everyone within a half-mile of its station, and is installing carbon filtration systems to remove the contaminant on almost all the wells with any MTBE found.

But the state-mandated investigation is focusing mainly on the area within a half-mile of the station, and many homeowners who live farther away have paid private labs to test their wells. Of 60 who reported their results recently to the Harford County Health Department, about one-third registered traces of MTBE, according to a tally the department provided to The Sun last week. Three of those were above the state threshold.

'Heads in the sand'

Carroll and Barbara Haynes, who live a mile southwest of the Exxon station, are waiting to hear from MDE after reporting more than a week ago that a lab test they paid for found 64 parts per billion MTBE in their well - three times the state threshold.