Vermont officials last month found contaminated drinking water at two locations in Hinesburg — one private well at a home and the well that serves the Hinesburg town garage.
State and town officials are optimistic the contamination is limited to what they already discovered, but scientists who specialize in groundwater contamination say anything downstream is at risk and solving the problem may prove tricky.
At the private residence, the Department of Environmental Conservation discovered unacceptable levels of poly- and perfluoroalkyl substances, commonly known as PFAS, plus methylene chloride and two other volatile organic compounds, contaminants that often come from household products such as paint thinner or bug spray.
At the town garage, the department found PFAS levels significantly above drinking water standards and discovered the water was polluted with diethyl ether and tetrahydrofuran, which are volatile organic compounds.
In a report to the town government, the state said the water should not be consumed. For now, the Hinesburg town government is supplying bottled water to people affected by the pollution.
Studies of the best-known PFAS show links to kidney cancer and testicular cancer, as well as endocrine disruption in humans. PFAS contamination in Bennington, North Bennington and Shaftsbury was discovered in 2015 and has required major efforts to ensure that people have water that’s safe to use.
Standing at the former Hinesburg landfill that sits at the end of Observatory Road, it’s impossible to tell that anything nefarious lies beneath the grassy area. The grass is trimmed short and the land is well kept.
But the landfill, which was capped around 30 years ago, is the likely source of the chemicals leaking into the groundwater, said James “Buzz” Surwilo, an environmental analyst for the solid waste management division of the state’s Department of Environmental Conservation.
Further testing, which is being conducted by the town, should confirm or deny the landfill as the source, he said.
The town of Hinesburg capped the landfill in the early 1990s, putting a big, thick, chemical-resistant plastic sheet over and beneath the waste and then sealing it in an attempt to contain any contaminants.
Although the landfill was sealed off 30 years ago, caring for a landfill is a lifelong job. After Vermont municipalities or private owners cap landfills, they are subject to ongoing monitoring — usually for 25 to 30 years — to make sure contaminants are not leaking out. Monitoring includes checking nearby streams and wells for contaminants and examining the landfill for erosion and cracking, which can signify cap failure.
After that, they have to get the landfill closure certified by the state as safe and effective and must continue watching the landfill in perpetuity.
But the Hinesburg landfill either never got certified or the documentation was lost. Hinesburg stopped monitoring the landfill after 19 years.
No one seems to know why.
“It seems it just sort of fell off the radar,” Surwilo said.
Joy Grossman, Hinesburg assistant town manager, echoed Surwilo, saying that neither the town nor the state could find documentation detailing why the landfill monitoring had stopped, and it just seemed as if monitoring fizzled out.
“Once you cap that landfill, it’s easier to forget that it’s there,” Surwilo said. Still, he said, this is an extremely unusual situation. He could not think of any other instance in which landfill monitoring stopped and was not documented.
Surwilo said it’s possible that documentation that could answer questions and provide more detail was lost in flooding during Tropical Storm Irene in 2011.
The documents that the town and state still have indicate the town stopped monitoring the wells around the landfill in 2009.
The town’s attention was brought back to the landfill in 2016 when development was being considered for a neighboring property. That’s evidently when the town realized there had been a huge lapse in monitoring, and the landfill could be the source of groundwater contamination.
At that point, the state decided there was no reason for the town to try and get the landfill legally certified as adequately closed off.
“We presumed — wrongly — that the Town was maintaining the landfill and that there were no environmental or health threats,” Surwilo said.
But this year, when a new project proposal led to the town to test some of the drinking water supplies near the landfill, it found the water was polluted.
When a solar company started looking into the landfill as a potential project site, the Office of Planning in the Vermont Agency of Natural Resources directed the town government and the company, Acorn Energy Solar, to confirm the project would not adversely affect the landfill and that all was well and good at the site.
That’s when they tested the monitoring wells and nearby drinking supplies and found PFAS and volatile organic compounds.
Despite the failure to take care of the landfill in the past, Surwilo said town leaders are working hard to deal with the landfill, now that they realize there is a problem.
“The town has been really responsible in stepping up and doing the right thing and understanding that they have to take care of their landfill, and so I give kudos to the town,” Surwilo said.
The town is now responsible for finding out where the contamination is stemming from, what the current and potential extent of the problem is, and how much more investigation needs to be done.
It also must create a plan to treat any contaminated water, confirm the effectiveness of the landfill cap and eventually receive post-closure certification from the state, which would officially label the landfill as properly sealed off.
“A [post-closure certification] will formalize an approved post-closure plan, with scheduled maintenance and monitoring requirements to ensure integrity of the gapping system and minimize risk to public health and the environment,” according to a letter written by Surwilo that was sent to the town.
At the same time, the town must create an environmental monitoring program showing that groundwater contaminant levels comply with state and or federal regulations, and that pollutants are stable, decreasing or impossible to detect for a five-year period.
Landfill breaches and consequent contamination are common in the United States and extremely difficult to remedy, said George Pinder, a University of Vermont civil and environmental engineering professor.
“It’s difficult to fix because you have to access underneath the landfill,” he said. “Which would, of course, be tricky.”
Usually, these breaches are managed by installing a series of wells around the contamination site, pumping the wells to pull out all the contaminated water and then treating it, Pinder said. But that’s assuming the landfill cover is effective. If it’s not effective, then groundwater continues working its way through the landfill, and the problem is much bigger.
In that case, solving the problem likely entails installing drains around the landfill to encourage water to flow away from the landfill and then subsequent treatment.
“Either way, anyone downstream has to be careful they’re not encountering the contaminated plume,” Pinder said.
