As new, more sensitive testing began yesterday for the source of a gasoline additive that has contaminated at least 127 Fallston area wells, state environmental officials are weighing new regulations to prevent previously undetected vapor leaks of methyl tertiary butyl ether, or MTBE, from underground fuel tanks across Maryland.
Yesterday, employees of an Arizona-based leak detection firm drilled about 50 holes in the pavement around the four underground fuel storage tanks at Upper Crossroads Exxon suspected by state officials of being a source of the ground-water contamination in the area.
Beginning today, a crew with Praxair Services Inc. plans to inject a chemical into the station's fuel system and monitor the holes around the tanks and pipes for tiny, but potentially significant, leaks of fuel vapor.
"We'll be able to direct the client right to the leak if there is one," said David Rabb, Praxair's business manager. "We're assuming there is not one -- but if there is." The test is expected to take two to four days.
Even before the results are in, however, Herbert M. Meade, chief of oil control for the Maryland Department of the Environment, said his agency is working on new regulations to address a previously unsuspected problem with many of the 13,000 underground fuel storage tanks in the state.
Although previous tests have not detected leaks at the Exxon at Routes 152 and 165, Meade said he and other officials believe -- based on reports in California and elsewhere -- that it's possible MTBE vapor seeped out of the fuel tanks or pipes into the groundwater. "All our regulations are geared to keeping liquid in the tank," Meade said. "We'd not even thought about vapors."
MTBE above the action level has been detected in about 400 private wells statewide, and traces have been found in about 100 public water systems, according to state officials. Meade indicated he suspects vapor leaks in many of the unsolved contamination cases his agency is investigating, when no obvious liquid leak has been found.
The check by Praxair, which claims to be able to pick up tiny leaks well below the detection levels of other testing equipment, may help to prove or disprove that theory. The firm was brought in by Exxon Mobil Corp., owner of the station, at the urging of state and local environmental officials.
Praxair's "enhanced leak detection" method can pinpoint an underground leak of about half a teaspoon an hour from tanks that hold thousands of gallons each, according to Rabb.
Enhanced leak detection is required by state regulation for stations near public drinking-water wells in California, which experienced some of the nation's earliest and worst MTBE contamination.
Testing of about 280 underground fuel storage systems in California using Praxair's technique found leaks in about 7 percent, said Rabb. Most of them had vapor leaks, he added.
'Enhanced leak detection'
This is the first time the firm's "enhanced leak detection" has been tried in Maryland to search for hard-to-find sources of MTBE leaks. If a leak is detected, Exxon Mobil has a construction crew standing by to attempt to fix it, said Betsy Eaton, a spokeswoman for the oil company.
Meade said the station would be allowed to remain open if the leaks are easily repaired. The station had to shut down temporarily yesterday afternoon, however, because the oil company invited news media to witness the start of testing.
Unable to pump any gas, Rick Hicks, who operates the station, watched the proceedings from inside. "We're looking for a good result," he said.
MTBE has been added to gasoline since the late 1970s to help it burn more cleanly. It is credited with helping to reduce air pollution, but the chemical dissolves easily in water and has tainted wells throughout Maryland and across the nation.
It is considered a possible human carcinogen by the Environmental Protection Agency, though health experts do not think it poses a risk when consumed at the low levels generally found in drinking water. The state acts when levels exceed 20 parts per billion because that is the lower limit at which it can be smelled or tasted, rendering water undesirable to drink.
Of 127 wells with MTBE in the Upper Crossroads area, 10 registered levels above the state threshold. They have been provided with carbon water filtration systems at Exxon's expense.
Dr. Andrew Bernstein, Harford County's health officer, said officials are still attempting to identify the extent and source or sources of the contamination at Upper Crossroads.
MTBE traces have been detected in wells more than a half-mile from the Exxon station.
Community meeting in Fallston
At a community meeting last night at Fallston High School, residents reported detecting MTBE through private testing firms in wells as far as two miles from the gas station. They voiced anger at not being informed years ago about the contamination, which has shown up off and on since 1991.
Wallace Waynick, who said a private company found traces of the additive in his well, complained that he was being "left out in the cold" because the investigation has focused mostly within a half-mile of the station.
Earlier, Del. Joanne S. Parrott, a Harford County Republican who lives a little more than a mile from Upper Crossroads, urged wider testing. She and other legislators are drafting bills to ban MTBE in Maryland, and local officials are eyeing a temporary ban on new gas stations.
Beatrice Elmo, who lives about a mile and a half from the station, voiced the frustration that many in the audience of about 400 felt when she questioned why residents had not been alerted five years ago when high MTBE levels were found in water at the station and at nearby businesses.
"This is outrageous," she said. "We should have been notified much, much sooner."
MDE's Meade said state regulations require notifying only those directly affected by contamination, but he apologized, as he has before, for not alerting the community sooner.
Sun staff writer Artika Rangan contributed to this article.
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