It's been more than a month since a 25,000-gallon gasoline leak was reported in Jacksonville, and the usually placid northern Baltimore County community remains one big cleanup zone.
Black plastic pipes are strung across lawns. Generators rumble, supplying power to the machines that pull gasoline and vapor from the ground. The narrow lanes are jammed with trucks, and helmeted workers in bright yellow vests seem to be everywhere.
"It's like we were suddenly invaded by Exxon," says Nanette Odend'hal, who lives at one end of formerly quiet Hampshire Glen Court.
The good news is that the race to recover gasoline before it gets into many residential wells seems to be going just about as well as can be expected, thanks to the lack of recent rainfall and a lucky confluence of topography and geology that has, officials said, kept most of the fuel from fanning out beneath many homes.
With help from more than 100 contract workers and vapor-recovery equipment from as far as California, ExxonMobil Corp. says it has recovered more than 21,000 gallons of the leaked gasoline.
The bad news is that a toxic gasoline additive has turned up in three more residential wells northeast of the Exxon station where the leak occurred, prompting state environmental officials to expand the search in that direction.
While the pipes on lawns will be buried and noisy machinery replaced in the next month or so, it will be necessary to continue pumping groundwater and vapors in the neighborhood for perhaps a decade or longer, officials say. But it is unlikely that all of the gasoline will ever be recovered, said Jim Higginbotham, technical manager of global remediation for ExxonMobil Corp.
"This is as bad a release as I've seen for a retail station," Higginbotham told a group of Jacksonville-area residents last week. But he also said it's one of the most successful cleanup efforts he's worked on, in terms of how fast fuel has been recovered.
Though Jacksonville residents wonder how a leak of nearly 700 gallons a day could have gone undetected for more than a month, oil company and state officials say the timing of the leak, along with its location, was in some ways fortunate.
`Stars lined up'
"There's a few items that the stars lined up on," said Herbert Meade, who oversees underground fuel storage and cleanup of leaks for the Maryland Department of the Environment.
The Exxon station, at the junction of Jarrettsville Pike and Paper Mill and Sweet Air roads, sits on a slight rise in the rolling countryside, uphill from a gully that runs southwest to a stream valley. The flow of groundwater tends to follow the surface of the land. ExxonMobil and state officials believe the saddle-shaped topography - and a linear fracture in the bedrock below - has kept the underground gasoline leak in a narrow channel, away from most homes.
Many leaks go undetected for years, leading to a much broader contamination of groundwater. But because this leak was weeks old when discovered, company officials launched an all-out effort to quickly recover the gasoline that they estimate was flowing as much as 10 feet a day through the fractured bedrock.
They called for vacuum trucks to begin suctioning gasoline floating in monitoring wells at the station. Since then, they have drilled more than 140 wells to find the fuel and pump out hundreds of thousands of gallons of tainted groundwater.
"The philosophy is [to] get the liquid up and out of there," Higginbotham said, while apologizing to residents for digging up their yards and clogging their roads.
The recovery effort has largely succeeded to the southwest of the station, officials say, where gasoline has not reached homeowners' wells on Robcaste Road about a quarter-mile away. Though one homeowner's well there registered low levels of the additive methyl tertiary butyl ether (MTBE), so much water has been pumped out of monitoring wells on that side of the station that the flow of contaminants has actually been reversed, they say.
With about 10,000 gallons of liquid gasoline pumped out of the ground so far, the ExxonMobil remediation expert says most of what is left is either dissolved in groundwater or in vapor form, lingering in the soil. The company estimates it has recovered the liquid equivalent of more than 11,000 gallons of gas vapors in the past six weeks.
The focus of the recovery effort is shifting to suctioning gas fumes from the ground and incinerating them in a large burner trucked in from California. A similar network of pipes is being hooked up to the northeast.
"We were a little fooled" by the spread of gas to the northeast, Higginbotham said. Initial test wells drilled there did not find any contaminants, and it wasn't until a monthly test of a bank branch's well there - already tainted by MTBE from another gas station's leak - showed a dramatic rise in contamination that officials realized that perhaps a fourth of the Exxon leak had run underground in that direction.