The Environmental Protection Agency’s five-year remedial investigation of the Hidden Lane Landfill in Sterling, first linked to trichloroethylene contamination in 1989, has concluded, allowing for a treatability study to begin.
At an open house meeting June 2, project manager Fred Mac Millan answered questions from the community and explained the EPA’s proposed method of dealing with the plume of TCE stemming from the landfill.
The preferred method at the moment, which will be tested for effectiveness during the treatability study, is to inject treatment compounds into the soil over the plume, which will help speed up the natural breakdown of TCE.
Mac Millan said. “It goes through a biodegradation process so that instead of trichloroethylene, it’s dicholoroethylene, take another [chlorine molecule] off, it’s monochloride, but that breaks down pretty quick to ethene which breaks down to ethane, which is just a long-chain carbon molecule and the bacteria continue to work on that and basically it just goes away.”
This method was devised after considering the site-specific challenges of this contamination.
One major challenge is the depth of the TCE plume at around 400 feet underground makes it hard to reach. This is made more problematic by the fact that TCE is only partly water-soluble, which means pumping water into the ground in order to force the chemical to the surface would be almost impossible.
Though the proposed method solves the issue of depth, it faces another challenge. The presence of fractures underground could result in the treatment compounds following an unexpected path and missing their target.
Mac Millan said, “We’ve mapped out a lot of these fracture zones, one of them is right near the area where we want to work. What we may try to do is… ride the fracture right down into [the plume].”
Though the remedial investigation gave initial information to determine how to fix the contamination, there is still the potential for unexpected variables.
“The only way to make sure this will work is to test it in the field,” Mac Millan said.
If the EPA’s tests show this method to be ineffective, they will have to find a new process.
In the meantime, residences with water supplies contaminated by TCE are protected by whole house filtration systems installed in 2005 in order to guard against health risks of the chemical, which includes probable carcinogenic effects, among others.
The treatability study will begin this summer, but the duration of the clean up is indeterminate depending on how quickly the study returns positive results.