Acid-draining rock poisons water across Montana

The State | Sammy Fretwell

October 14, 2014
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BUTTE, MONT. — Tourism promoters charge people $2 apiece to look at the most notoriously polluted mining site in Montana, an old copper pit filled with toxic water that will likely never be cleaned up.

The Berkeley Pit, which dominates the landscape of Butte, is 1,780 feet deep and holds 42 billion gallons of water tainted by metals and acid. The contamination is so severe that site managers operate equipment to scare birds away from almost certain death.

It’s an extreme example of how acid that leaks from mines can affect the environment – but certainly not the only one. Across the nation, hard rock and coal mines are releasing acids and metals that can be toxic to wildlife and people.

Many are mines in western states with histories of digging for metals. But even in spots such as South Carolina, acids are draining from small gold mines that were abandoned in the 1990s. Today, acid and metals are potential threats from what would be the largest open-pit gold mine ever developed in South Carolina, a 2,612-acre site proposed for north of Camden in Lancaster County.

“If you go down the list of issues you have in mining, probably the most significant one – especially in high-water areas – is acid drainage,” said Glenn Miller, a University of Nevada-Reno environmental professor who studies contamination from metals mines. “It’s almost impossible to stop it.”

Nationally, acid drainage is the primary cause of water pollution at 40 hard rock mines from Alaska to South Carolina, according to a 2013 report from Earthworks, an environmental group that compiled and analyzed government data.

The Earthworks study said up to 27 billion gallons of contaminated water would be generated by the mines annually for hundreds, if not thousands of years. Polluting sites in the study included the now-closed Brewer Gold Mine in South Carolina, as well as three Montana gold mines: the defunct Zortman and Landusky sites and the still-running Golden Sunlight operation. The Berkeley Pit copper site also made the list.

“Perpetual pollution from metal mines has contaminated drinking water aquifers, created long-standing public health risks and destroyed fish and wildlife and their habitat,” the Earthworks study said.

Mining companies say they’ve made strides in attacking the problem of acid drainage and are optimistic their efforts will reduce, and in some cases prevent, the flow of contaminants into the environment. All agree that controlling or stopping acid drainage is important to protect groundwater and prevent river pollution near mines.

Acid drainage results from a natural chemical reaction.

When miners unearth sulfide-rich rocks in their search for gold or copper, they expose the long-buried material to air and water. And when that exposure happens, the rocks – often pyrite – generate sulfuric acid. In turn, the acid releases metals still in the rocks – metals that then trickle into rivers, lakes and groundwater.

When metals dissolve in water, they can contaminate fish or make the water so toxic that fish can’t live there. Water from the Berkeley Pit proved poisonous enough in 1995 that it killed some 300 geese after they lighted on the surface. The birds’ throats were burned from exposure to the water. Today, site managers sound horns and play music to keep birds away.

Miller said acid drainage can go on for hundreds, or even thousands, of years after rock is first exposed, leaving a long-term responsibility to manage and treat the toxic water, sometimes at taxpayer expense.

“You end up with treatment in perpetuity, which is a long time,” Miller said. “What institution has been around for over 500 years or 1,000 years? You still are going to have to worry about that.”

In one spot in England, acid drainage is still “bleeding” into the environment after some 2,000 years, he said.

Butte legacy

Standing on a viewing platform built for tourists at the Berkeley Pit, environmental consultant Jim Kuipers took note of the rock walls surrounding the toxic lake and explained that they are full of material that has created acid drainage.

“This is a good example of how bad it can be,” said Kuipers, a leading authority on environmental problems created by metals mining, who recently worked with environmentalists in South Carolina.

It took more than three decades to dig the 1,780-foot Berkeley Pit as the old Anaconda company sought to reach lucrative copper deposits. But the pit shut down in the early 1980s and pumps that had kept the pit dry for mining were shut off. That allowed groundwater that seeps through the acid-generating rock to begin filling up the pit.

Now, Kuipers said Butte is scrambling to make sure water levels don’t get so high that the contamination starts flowing away from the pit and toward the nearby Clark Fork River. Unfortunately, that’s no short-term project, he said. Water levels will have to be managed forever to protect the river, which already is part of a Superfund cleanup because of other mining pollution.

“In perpetuity, we are going to have to pump it to keep the flow going this way, rather than heading down the Clark Fork River,’’ Kuipers said.

Data collected by the Montana Bureau of Mines show high levels of arsenic, cadmium, copper and zinc in the Berkeley Pit’s brownish-blue water. In each case, the concentration of these metals exceeds safe drinking water standards, sometimes substantially, the bureau reports.

The federal safe drinking water standard for cadmium, a metal linked to cancer, is 5 parts per billion, but recent water tests show cadmium levels exceed 2,000 parts per billion. Copper concentrations are even more pronounced. Copper in the pit exceeds 48,000 parts per billion. The safe drinking water standard for copper is 1,300 parts per billion, according to the Bureau of Mines.

“If ingested a lot over a period of time it would damage your esophagus and things like that,” said Ted Duaime, a hydro-geologist with the Bureau of Mines who monitors the Berkeley Pit. “The water can be toxic to aquatic species, which are more sensitive.”

Ironically, the Berkeley Pit has become a rather dubious tourist attraction for Butte, a city with a storied mining history that once was known as “The Richest Hill on Earth.” Area leaders today maintain the viewing platform that overlooks the Berkeley, as well as a gift shop. On a recent Monday in August, about 200 people stopped by for some pollution tourism, according to managers of the attraction.

“I never dreamed anybody would pay 2 bucks to see a pit lake,” Kuipers said.

Orange creeks

It’s unlikely a gold mining pit would have water as polluted as at the Berkeley. Copper mines typically have more extreme acid problems, Miller and Kuipers said.

Nonetheless, both agreed acid drainage is a concern at gold mines. The problem has been pronounced enough at many gold mines to poison creeks with metals, said Bonnie Gestring, a researcher with Earthworks who has studied the issue extensively.

Gold mines “typically will have other metals associated with gold that can leach out of the rock and be a public health hazard,” Gestring said.

At the Zortman and Landusky mines in north central Montana, American Indians are living the legacy of acid drainage 16 years after owner Pegasus Gold filed for bankruptcy and the mines closed. The property has cost taxpayers more than $23 million for cleanup work that is still years from completion.

Tribal leaders have been widely photographed holding up glasses of orange water tied to acid drainage. To protect water supplies will require perpetual treatment, said Ina Nez Perce, a Native American who manages environmental issues at the Fort Belknap reservation.

“We are seeing visual evidence of the first stages of acid mine drainage,” she said. “It flows right onto our reservation.”

In South Carolina, the old Barite Hill gold mine near McCormick contains a creek that is rusty-colored, a likely result of acid pulling metals from the gold mine’s sulfide rock, said Candice Teichert, a cleanup coordinator for the U.S. Environmental Protection Agency. The Brewer gold mine in Chesterfield County also has acid drainage that has impacted creeks and groundwater, according to the EPA. Both are federal Superfund sites.

To control acid drainage, miners and government officials sometimes rebury exposed rock beneath plastic liners as well as layers of soil and plants. The rocks also sit atop plastic liners, creating what engineers call a “burrito” of plastic that contains the tainted rock inside.

The idea is to prevent water from coming in contact with the material. That’s what is planned at the proposed Haile Gold Mine in South Carolina, where acid-generating rock also is found. The site has shown indications of acid drainage from a previous mining operation in the 1980s. But Romarco Minerals, the company opening the Haile mine, said it’s confident the burrito plan will control the problem.

“If we burrito it up, we can keep the water out,” company executive Jim Arnold said.

A similar system is in place at the Golden Sunlight Mine in Montana. The Treasure State’s last large open-pit gold mine, the Golden Sunlight has put soil over mountains of waste rock that miners have dug up to extract gold since 1982. The mine also has planted vegetation to soak up rainfall. The idea is to prevent water from coming in contact with the rock.

“Acid generation comes from a reaction of pyrite with oxygen and water, so if you can kick one of those three legs out from underneath, you can prevent it from happening,” said Mark Thompson, the Golden Sunlight’s chief environmental officer. “We try to exclude the water.”

Thompson said, however, that different systems to control acid drainage work better in some climates than in others. He said the system in place in Montana, which receives about 12 to 15 inches of precipitation annually, might not work as well in Alaska or South Carolina, the latter of which receives about 45 inches of rain a year.

And Kuipers, the consultant, said it’s difficult to guarantee that a method of controlling acid mine drainage will work forever, even though the companies such as Romarco have seemingly sound plans to control the problem.

“We’re not doing the same things we did 30 years ago,” he said. “But that doesn’t mean we’ve figured everything out, that we can anticipate every problem and that mistakes won’t occur.”

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Tagged with: montana, mining, berkeley pit, acid mine drainage

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