WASHINGTON (CN) – The U.S. Supreme Court appeared concerned Tuesday about the practical consequences of siding with a group of Anaconda landowners who live on land contaminated by arsenic and lead and want a more aggressive cleanup of the Superfund site than what has been approved.

“I guess the question is, it’s hard for EPA to go around and try to figure out who’s creating sandboxes,” Justice Elena Kagan said, referring to the Environmental Protection Agency. “And so why should the onus be on EPA to figure out who’s creating sandboxes?”

In its heyday in the early 1900s, the Anaconda Copper Mining Company was one of the world’s largest companies and the most prolific producer of copper. At the heart of its operation was a series of copper smelters nestled in the mountains of Montana that brought in ore from all over the world, sustaining scores of jobs and firing up the state’s economy.

The Atlantic Richfield Company bought a diminished Anaconda in 1977, in a deal Forbes would dub one of the worst mergers of the decade.

A relic of the smelter's 585-foot-tall stack – one of the largest free-standing brick structures in the world – still rises on a hill in Anaconda, serving both as a testament to the economic giant Anaconda once was and as a reminder of the environmental carnage the booming copper industry brought to the region.

Though Atlantic Richfield extinguished the smelter’s fires in 1980, it would burn at the company’s profits again when Congress passed the Comprehensive Environmental Response, Compensation and Liability Act, or CERCLA, in 1980.

Under the law, the EPA in 1983 designated a 300-square-mile area around the smelter as one of the nation’s first and largest Superfund sites and Atlantic Richfield has spent some $450 million over the ensuing decades working to replace soil and vegetation to help mitigate the arsenic and lead the smelter spewed across the land.

But for a group of landowners who live a few miles downwind of the smelter, the efforts were not enough. They sued Atlantic Richfield in Montana state court seeking as much as $58 million to do additional work that would go well beyond what the EPA has required under CERCLA, including replacing more dirt and digging long trenches to filter groundwater.

CERCLA prohibits legal challenges to the EPA’s remediation plans and prevents entities that might be responsible for cleaning up a site from doing so without the agency’s approval. The EPA said the restoration efforts the landowners requested would directly conflict with the agency’s plans for the property.

But the Montana Supreme Court allowed the case to go forward, ruling the landowners’ plans did not conflict with the EPA’s and that CERCLA does not block out state-court challenges like the ones the landowners brought.

Arguing before the Supreme Court on Tuesday, Atlantic Richfield attorney Lisa Blatt said requiring the company to finance the work would put it in violation of the EPA’s orders, making the landowners’ claims preempted by federal law.

The Williams & Connolly attorney also pointed out CERCLA prevents people who might be responsible for cleaning up contamination, known as PRPs, from doing remediation work without the EPA’s signoff.

“Superfund sites contain extremely hazardous substances – lead, mercury, plutonium, to name a few,” Blatt said Tuesday. “Excavation, transportation and disposal of these substances is risky not only to neighbors but the millions of people who live next door to Superfund sites. Whether these risks are worth any benefits should be evaluated by EPA, not juries on an ad hoc basis.”

Christopher Michel, an assistant to the solicitor general who argued for the Trump administration on the side of Atlantic Richfield, made this point as well. He said people who live on Superfund sites have to give up some of their ability to use their land as they please in order to stop the spread of toxic chemicals that might be disturbed with remediation efforts the EPA has not approved.

Some justices, most notably Justice Sonia Sotomayor, seemed interested in a limited ruling that would allow the landowners to press their claims so long as they were able to show the EPA would back their plans to clean up the land.

“So what’s wrong with an opinion that we write that says what you’re missing is the next step?” Sotomayor asked. “You have to be able to show that that remediation will be approved.”

Morrison & Foerster attorney Joseph Palmore, who argued for the landowners, told the justices the EPA’s argument effectively gives the agency unlimited control over vast swaths of land that have been designated Superfund sites, preventing property owners from doing even the most basic work on their land without Washington’s approval.

The work on the Anaconda site is expected to run through 2025 and even then, because arsenic will still be in the soil, the EPA will have a say in what the landowners do. Congress did not intend that large of a federal power grab when it passed CERCLA, Palmore argued.

“So the argument on the other side is that EPA has a permanent easement on my clients’ property requiring them to store Arco’s arsenic and lead forever unless we get EPA permission to remove it,” he said.

Palmore also argued the landowners do not qualify as PRPs, as the EPA has never suggested they might be responsible for cleanup work.

But the justices seemed concerned about what would happen if all people who live on Superfund sites would be able to implement their own cleanup plans without the EPA’s approval by going to court.

“EPA would say if you want to disturb arsenic-infected land, dirt in a way that would not only harm your neighbors but could harm people many, many miles away,” Chief Justice John Roberts said. “I mean, yes, you want to just do things on your land, but you can’t overlook the fact that that is going to have harmful effects on everybody else around you.”

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