A mining dam failure similar to the one that killed more than 100 people in Brazil could happen in the U.S., according to a mine engineer who consults with the government.
At the root of the risk is a quilt of differing state regulations, sloppy dam construction, lax maintenance, neglect of decades-old dams that are wrongly assumed to be stable, and stronger storms dumping water into dams that weren’t designed to handle the weight, said James Kuipers, who consults with the Environmental Protection Agency and state governments on tailings dams, which hold mining waste.
“It can happen here,” Kuipers told Bloomberg Environment.
But the industry says tailings dams in the U.S. are safer than they’ve ever been, thanks to advances in technology and design. Rigorous oversight also ensures that dams don’t break, said Ashley Burke, a spokeswoman with the National Mining Association.
“The U.S. mining industry is one of the most heavily regulated industries in the world,” Burke said.
And in the event of a dam break, the risk to human life is lower in the U.S. than in some other parts of the world, including Brazil, because “a lot of our mining, especially metals mining, takes place in areas with low population density,” said David Chambers, a mine engineer and president of the Center for Science in Public Participation, a nonprofit that focuses on mining pollution.
But Kuipers says: “Something could always happen, even where we have the highest level of confidence. There are so many places in the U.S. where we have populations downstream. There are locations that could kill hundreds of people easily.”
Wall of Mud
On Jan. 25, a dam holding back 3 billion gallons of sludgy mine waste burst in southeastern Brazil, killing more than 100 people. A wall of mud quickly engulfed a busy cafeteria full of workers employed by iron ore giant Vale SA, which owned the dam. The deluge then charged through the nearby town of Brumadinho.
Investigators haven’t yet pinned down what caused the dam failure, but another Vale dam failed in a similar, deadly environmental disaster in Brazil late in 2015.
In the U.S., environmental group Earthworks found in 2012 that 28 percent of all U.S. copper mine waste dams had failed at some point.
The biggest potential problem spots in the U.S. are in states like Alaska and Minnesota, which tend to have heavy rains, said Kuipers, principal consulting engineer at Kuipers and Associates LLC. A downpour can rapidly increase the weight of the material inside the dam and liquefy relatively dry mine waste that can then spill out, overwhelming and drowning people in its path, he said.
Earthquake-prone regions like Nevada, Washington, and Wyoming are also worrisome, Kuipers said. For example, the planned Pebble Mine in Alaska would be built close to partly unmapped fault lines that could cross directly through the mine, said Bretwood Higman, executive director of environmental advocacy group Ground Truth Trekking.
“If you have an earthquake, there might be impacts to the mine facility, and liquefaction can lead to failure of the dam or motion of the flow of the tailings,” Higman said.
Pebble’s owner, Northern Dynasty Minerals, has said its facilities “will withstand the greatest possible seismic activity predicted by science.”
‘Risk Goes on Permanently’
The Bruno Creek tailings pond still in use in the Salmon River Mountains of Idaho, is potentially problematic, Kuipers said. Perched high above the Salmon River, the dam currently holds back about 100 million tons of mineral waste, which could plunge at high velocity downstream.
“If they don’t figure out how to close it properly, that risk goes on permanently,” said Kuipers, referring to the Thompson Creek Mining Co.
Suzanne Budge, a Thompson Creek spokeswoman, said the tailings facility “has been closely monitored for decades [and] is managed regularly for stability, material control, water management, and several other technical issues material to the stability of the tailings facility.”
The environmental group Appalachian Voices has raised concern about the massive Brushy Fork pond 40 miles south of Charleston, W.Va., which features a 950-foot dam built to hold back 8 billion gallons of black water that was once used to wash coal.
Should the dam fail, a monstrous surge of water dense with mercury, arsenic, lead, and cadmium could immediately overwhelm local residents and flow into the Coal River, which ultimately joins the Mississippi River, said Erin Savage, a campaign coordinator at Appalachian Voices.
“If a dam in Central Appalachia broke, people would almost certainly die,” Savage said.
Alpha Natural Resources, which owns dam operator Marfork Coal Co., didn’t respond to a request for comment.
Each state has its own regulatory scheme. But even states that do a good job of overseeing the design, operation, and closure of a mine—such as Montana, Alaska, and Nevada—still rely mostly on mining companies to police themselves, Kuipers said.
Tailings facilities don’t generate profits, and dam safety tends to become a low priority for companies, according to Kuipers.
But Burke, from the mining industry group, said the state-by-state system works because it allows for flexibility.
“While various agencies provide guidance in terms of how tailings dams should be constructed and maintained, there is universal agreement that specific construction determinations are made on a case-by-case basis, taking into consideration foundation location and stability issues, potential environmental impacts, and the type of material to be stored,” Burke said.
“There is no simple solution to prevent every incident, but the combination of constant vigilance of industry and the thorough regulation governing it in the U.S. work together to minimize the potential for accidents,” she said.
Inventory of Dams Called For
Developing a complete list of dams across the U.S., then assessing them one by one, is the first step to mitigating any risk, said Bonnie Gestring, Earthworks’ Northwest program director.
That initial assessment is especially crucial for old dams on private lands that are no longer owned by anyone, she said.
Congress and federal regulators also should mandate the technical recommendations that came out of the 2014 Mount Polley dam failure in British Columbia, Gestring said.
And mining companies should be required to post surety bonds to cover the costs of a dam failure, according to Chambers.
While companies do have to bond the cleanup of their mines, those IOUs don’t cover dam failures because federal and state agencies don’t consider them to be reasonably foreseeable events.
A mandatory bond would give mining companies a financial incentive to make sure their dams are safe, Chambers said.
“Tailings dams have to last forever,” Gestring said. “They’re in the landscape in perpetuity.”
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