Wells for a half-dozen homes in the Randallstown area have been tested after gasoline contamination was detected in groundwater at a property with a long history of pollution problems, according to the Maryland Department of the Environment.
The tests are a precaution - required because concentrations of benzene and MTBE were found recently in shallow groundwater near Charlie's Service Station on Liberty Road near Wards Chapel Road, said Herb Meade, administrator of the MDE's oil control program.
Recent tests have shown no contamination in the drinking well of the gas station, which is deeper than the monitoring wells where the contamination has been detected, Meade said.
"We don't think we have an off-site impact," he said.
The service station operator is required to submit the additional well testing results by today. It will likely take about a week for the results to be processed, Meade said.
Sampling in June of monitoring wells at Charlie's Service Station showed methyl tert-butyl ether, or MTBE, at more than 100 times the acceptable level, and benzene, a petroleum constituent, at nearly 50 times the acceptable level, according to an MDE report.
The tests are part of the monitoring at the gas station, which is near the Carroll County line, the report shows.
In June, tests of the monitoring wells showed benzene at 239 parts per billion. The maximum acceptable level established by the U.S. Environmental Protection Agency is 5 parts per billion. The level of ethyl-benzene, another petroleum constituent, was 771 parts per billion. The EPA's maximum acceptable level is 770 parts per billion.
And the level of MTBE, an additive removed from Maryland gasoline last summer because of its role in fouling wells, was 2,664 parts per billion, the tests showed. When MTBE reaches the level of 20 parts per billion, MDE recommends filtering or replacing water, because it can be tasted or smelled.
A former Exxon station closed at the location in 1981 after settling a lawsuit with nearby residents whose wells were tainted by gasoline from the station's underground storage tanks, according to the MDE.
Charlie Brocato, who owns Charlie's Service Station but not the property in Randallstown, said he believes the recent contamination detected is left from when the Exxon station was there.
"All my tanks passed the tests," he said. "It's kind of weird, they found it when I put my wells in in May, but it's been there since the 1950s. I wasn't even alive then."
Meade said the contamination could be residual from old underground storage tanks that have been removed from the property. He said the additional tests are designed to determine the extent of the contamination and to determine whether it's being caused by old problem or a new issue.
In Baltimore County, more than 100 properties where fuel has been stored in underground tanks are being monitored by the MDE because of past contamination from gasoline compounds and MTBE, Meade said.
MTBE has caused cancer in lab animals, though its health effects at low levels are unknown.
Added to gas in the early 1990s to help it burn more cleanly, MTBE can spread rapidly in groundwater and persists for years unless treated or exposed to air. It has been largely replaced by ethanol.