The triangular plot of land in Weymouth where Enbridge plans to build a natural gas compressor station is contaminated with arsenic, coal ash, and an underground pool of old diesel fuel. The site was previously used by Boston Edison to store coal for a nearby coal-fired power plant, and it appears coal ash and other materials were dumped there. An above-ground storage tank that leaked diesel fuel for decades also contributed to the pollution. State law requires Enbridge to test the soil and groundwater and design a cleanup plan before construction. Tests confirmed contamination from heavy metals and residual fuel, which has raised health concerns from local officials.

1. On the banks of the Fore River in Weymouth, just west of Kings Cove Park and north of Route 3A, there s a triang
lar plot of fenced-in land. The future home of a natural gas compressor station, the space looks like any other grassy
rea. But just below the surface, a legacy of pollution from power plants fired by coal, oil and gas lingers.
Documents filed with the state show the dirt contains arsenic and coal ash, the lightweight, heavy-metal rich substan
e left after coal burns. And below ground, there s a pool of old diesel fuel that one environmental expert working o
the site said could have the consistency of peanut butter.
For background on what the compressor station is, and why Enbridge wants to build it, read our explainer here.
Exposure to heavy metals has been linked to cancer, impaired neurological development and other health problems,
hich is why Enbridge, the company behind the project, is promising to take precautions during construction and help
clean up the property. But some in the Weymouth community including the mayor, who has called the area a "ha
ardous waste site" are skeptical of the company's plans.
So what s in the dirt? And what s the cleanup plan? Here s what you need to know.
How Did The Site Get Polluted?
The peninsula jutting into the Fore River north of 3A a piece of land comprising a wastewater pumping station, a
atural gas metering station, Kings Cove Park and the future site of the compressor station is known locally as the
north parcel." Much of the ground there, like in Boston's Back Bay, is made from landfill.
It's unclear when the fill process began and ended, but the shoreline that exists today was in place by the mid-1920s,
hen Boston Edison built the coal-fired Edgar Steam-Electric Station nearby. The company, which used the north par
el primarily to store coal, appears to have also dumped coal, coal ash and "clinkers" hard, non-combustible materi
l left after burning coal. There are also old furnace bricks scattered across the site, which many in the community wo
ry contain asbestos (a claim Enbridge disputes).
The Edgar Power Station. (Library of Congress, Prints & Photographs Division, HAER MASS,11-WEYMO,6-)The
dgar Power Station. (Library of Congress, Prints & Photographs Division, HAER MASS,11-WEYMO,6-)
In 1974, the company put an 11.2 million gallon above-ground storage tank on the north parcel. For decades, this tan
leaked diesel fuel into the soil. Over time, the leaked fuel partially solidified and pooled underground (this is what o
e engineer said had the consistency of peanut butter). This substance is technically referred to as a light non-aqueous
phase liquid (LNAPL), and to this day exists in viscous puddles under parts of the north parcel. In documents, Enbri
ge says tests show "limited or no LNAPL mobility," meaning it's not spreading or mixing into the groundwater.
The Edgar plant shut down in 1970. On the same site, the Fore River Energy Center, a natural gas plant, opened in 2
03. Around that same time, the fuel tank was removed and the Massachusetts Water Resources Authority built a was
ewater pumping station on the north end of the peninsula.
Enbridge purchased the property in 2016 and announced its plan to build the compressor station. Following state law
the company hired environmental experts to test the soil and groundwater. The results of those test confirmed what
as widely known: the site is contaminated.
What Does State Law Say About This Contamination?
The Massachusetts Department of Environmental Protection (MassDEP) oversees hazardous waste site assessment a
d cleanup in the state, though its employees don t do the actual work themselves. The job is privatized and contract
d out to a licensed site professional.
Enbridge hired TRC Environmental Corporation to test the soil and design the cleanup plan for the Weymouth site. (

2. or the sake of simplicity, this article will refer to Enbridge s cleanup plans and reports, but just know that independ
nt experts with TRC are the ones doing the work.)
So, after notifying the government of its plans to build a compressor station, Enbridge next had to figure out what ex
ctly is in the soil and groundwater on the site, and whether the contamination poses a significant risk as defined
by MassDEP.
The state uses a complicated formula to determine significant risk, but a lot depends on what the land will be used fo
a plot of land that s going to house an apartment building needs to be cleaner than one with a manufacturing pl
nt on it, for example.