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Plow Shop Pond was once contaminated but cleanup efforts has returned fish to the pond.

DEVENS — When the military base closed in 1996, the Army left behind an unwanted legacy of toxic waste, enough to earn a Superfund designation.

The U.S. Environmental Protection Agency identified 324 potential areas of contamination on the land carved out of three towns. Most sites have been cleaned or have approved plans in place.

Three of them are within a stone’s throw of West Main Street in Ayer. One leaks arsenic into the groundwater. The other two are now clean enough that folks are allowed to fish in the water and the land is home to a threatened bird, the grasshopper sparrow.

As the responsible agency, the Army was tasked with restoring the sites so that they do not pose a present or future threat to human health or the environment. The EPA is the regulatory agency, working with Massachusetts Department of Environmental Protection to provide oversight.

Since these sites are within the boundaries of Ayer, the town is involved. A citizens’ group, People of Ayer Concerned about the Environment, keeps an eye on the whole thing.

Lately, they have some concerns. It seems the Army wants to shut down the arsenic cleanup.

Shepley Hill Landfill

When Devens was added to the EPA’s national priorities list in 1989, the landfill was of particular concern. It posed a significant threat of contaminating groundwater with arsenic.

The cleanup has been an expensive and contentious effort that has not yet succeeded. The Army wants out but the EPA says it needs more information before giving up on the project.

There seems to be no shortage of data, but still more is being gathered. Reports generated since the beginning of the project total up to thousands of pages.

The Army and the EPA agree on some of the basics. Arsenic is entering groundwater. The poison is present in the contents of the landfill and in the surrounding bedrock.

Arsenic levels in some of the monitoring wells has decreased since the Army installed an arsenic treatment plant in 2006. The region also has naturally-occurring arsenic.

The Army’s position

The Army wants to shut the treatment system down.

“It’s been about 12 years. We’ve been saying the pump and treat system is not effective,” said Bob Simeone, the base realignment and closure environmental coordinator.

“It’s not going to reach cleanup goals,” he added. “There really isn’t an effective remedy.”

The Army takes the position that it is not possible to get the levels under 10 parts per billion, the safe level for drinking water, in a reasonable time frame. Arsenic from bedrock dissolving in the water means the level will not significantly decrease in the near future, Simeone said. It might take 100 years.

“Essentially removing the arsenic that’s in solution in the groundwater will never be effective,” he said. “There’s an infinite supply of arsenic.”

The carbon in the peat underlying part of the landfill contributes to allowing arsenic to dissolve in the water, he said. In the absence of oxygen, the process intensifies.

As part of the landfill closure, it was capped. Arsenic levels went up when that happened, said Richard Doherty of Engineering Consulting Resources, Inc. He prepared a response to the Army’s 2015 five-year plan for PACE, the citizens’ group.

The pump-and-treat system is expensive to run and it is not good for the environment, Simeone said. It generates tons of sludge and uses gas containers.

The Army wants a technical impractibility

waiver, an okay to not reach the drinking water safety threshold of 10 parts per billion, Simeone said.

“The EPA has said, ‘No way.’ The state has said, ‘No way,'” he said.

The EPA’s position

The Army has not made its case to close the system, the EPA maintains. The data does not show that naturally-occurring arsenic is the problem.

“The EPA’s position is the bulk of the arsenic is coming from the landfill,” said Lynne Jennings, regional director of the office of site remediation and restoration of the EPA.

As the EPA sees it, the level remains high because the system is not working right.

“Some landfill arsenic is bypassing the collection wells,” Jennings said. “That is why we haven’t seen dramatic reductions.”

The EPA sent a very detailed letter to the Army with a scope of work that needed to be done to collect data to support its conclusion, she said.

“We’re not proceeding until we get this data back,” she said. “Depending on that data, we will make our own conclusions.”

As a regulatory agency, the EPA has kept a close eye the Army’s actions at Shepley Hill Landfill. “They shut it down once,” Jennings said. “We actually went after them and got penalties for them doing that.”

In 2013, the Army shut down the plant due to a lapse in contract funding, said an email from Ginny Lombardo, chief remediation and restoration II branch of the EPA. The “Army informed EPA of the shut down and worked quickly to restart the system. Army paid a $5,000 stipulated penalty in 2013 for this violation.”

The Army has begun work to collect the data the EPA wants, Simeone said. “We’ll be able to move forward and make our requests again,” he said. “Based on the science, it’s likely we’re going to come to the same conclusions.”

Keeping people safe

In 2015, Ayer issued a moratorium on wells on the land impacted by the arsenic from the landfill.

The Army was responsible for contacting the owners and residents of just under 100 parcels along West Main and Shirley streets. No one was using private wells, Simeone said.

If the EPA does grant a waiver, the Army will not be required to bring the arsenic level down to safe drinking water levels. Monitoring and the ban on using well water will stand between people and arsenic exposure.

With the well ban, Doherty said the risk of exposure is minimal. The contaminated groundwater is deep; even digging a hole for a pool would not be a problem.

There is no arsenic in the Ayer public water supply.

The impacted area includes private homes, businesses and a church.

Plow Shop Pond and the Railroad Roundhouse

The cleanup of an area in the path of arsenic coming from the landfill met with more success.

Arsenic entered Plow Shop Pond through groundwater from the landfill. As the chemical rose to the surface, according to an Army report, it oxidized into fine particles like rust. This changed the color of the water and the area became known as Red Cove.

A railroad roundhouse located on the southern shore of the pond left behind another legacy: coal dust and debris. Arsenic, copper, lead, zinc and other chemicals were in the soil at the site and in the sediment in the pond.

The first step was to prevent the arsenic-tainted groundwater from reaching the pond. In 2012, the Army installed an 850-foot long hydraulic barrier wall on bedrock to channel the groundwater north, back into the landfill area.

When that proved successful, sediment removal in the pond and at the site of the roundhouse made the areas safe for recreational use. The pond is open for catch-and-release fishing and the railroad site is zoned as open space/recreational by Devens.

The Army recommended a deed restriction preventing residential development when the roundhouse site is turned over to MassDevelopment. Any excavation by contractors must be done according to guidelines. The site will be inspected yearly.

Both the EPA and MassDEP agreed with the Army report, said Simeone in an email.

The cost for Superfund cleanup is the responsibility of the companies or people that caused the contamination, according to the EPA website.

The railroad owned the roundhouse. Litigation is pending in federal court for the United States vs. Boston and Maine Railroad, Simeone wrote in an email.

How the Army came to own the property

In the late 19th century, Ayer was a hub for north/south and east/west rail lines. Factories, including Ames Plow and a tannery, had access to reliable transportation and to water to generate power.

Levi W. Phelps dammed the Nonacoicus Brook in the 1870s to generate power to run a sawmill, said his great-great nephew Calvin Moore. The dam created was is now called Plow Shop Pond.

The Ames buildings are gone, but the family business, now Moore’s Lumber, is located where the Phelps and Ames buildings were.

Phelps also bought huge tracts of land for lumber, Moore said. He sold the granite hill and marshy land that became the Shepley Hill Landfill to the Army in the early 20th century when Devens was formed.

Moore owns half of Plow Shop Pond, north from the channel of the brook, he said.

When the base closed in 1996, the Army retained ownership of parts of Devens, including Superfund sites.

Follow Anne O’Connor on Twitter and Tout @a1oconnor.

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