Mining companies say they try to minimize dangers, damages

Mining comes with plenty of environmental baggage.

From poisons to air quality to gaping holes in the ground, miners leave a mark on the countryside.

But some of those threats are more real than others.

It might surprise you to know that the cyanide used by mines isn't really that harmful, or that the key danger to human safety that environmental scientists see these days is an abandoned open pit.

Mining companies say they're doing what they can to ease those aftereffects.

Still, there will be "management issues for decades, if not centuries," says Glenn Miller, an environmental chemist and professor of natural resources and environmental science at the University of Nevada, Reno.

How much management is needed depends on the environmental concern.

CYANIDE

Sure, it gets a lot of attention, but people's focus on cyanide used to leach gold from ore isn't quite warranted, Miller says. The state's mining industry uses about 100,000 tons a year, and there have been no human deaths reported from the poison.

"As far as human health and cyanide, the industry has been very, very good," he says.

Plus, cyanide concentrations are low. Barrick Gold Corp. uses 0.25 pounds per ton of water at its heap-leach pads, a solution of .0001 percent cyanide. Companies also sign international codes that require transportation and storage safety precautions.

Cyanide also degrades quickly in the environment, Miller says.

Despite decades of research into less-toxic alternatives, cyanide remains the best chemical for separating gold from low-grade ore, so it'll be around a while.

The biggest problem with cyanide isn't that it's toxic. The real issue is that it allows mining of vast amounts of rock, Miller says.

ACID DRAINAGE

Thanks to high gold prices, it's worthwhile to mine ore that has just $6 or $8 of gold in each ton.

The result? Pile upon pile of waste rock that hasn't seen oxygen or water for millions of years. Freed from the ground, that rock oxidizes and generates sulfuric acid, a corrosive liquid that can burn plants, birds and animals.

"It's very difficult to stop. You get some serious problems that need to be remediated," Miller says.

Other potential contaminants include mercury and arsenic.

Mining companies use leach pad liners of clay and polyethylene to keep the poisons out of groundwater, but "you have to assume some liners are going to leak," Miller says. "The potential for contamination will exist far into the future."

But John Mudge, vice president of environmental and social responsibility for Newmont Mining Corp., says pad liners are robust: "They have 300 feet of rock on them, and they're not fazed at all."

John Hadder, director of Reno-based environmental advocacy group Great Basin Resource Watch, says that won't always be the case.

"The jury's out on liners. They will eventually fail," he says. "The question is whether they'll fail in a long-enough time frame that the rock is no longer contaminated, and no longer a threat to groundwater."

AIR QUALITY

Mining companies acknowledge their business creates air pollution.

Barrick says its biggest emission is dust from roads, rock crushers and conveyor belts that transport ore.

Other emissions come from plants that process ore through mills or roasters. Particulates, sulfur dioxide, carbon monoxide, mercury - all are airborne byproducts of refining.

Both Newmont and Barrick say they suppress dust emissions by wetting roads, crushers and conveyor belts. They also use filters, scrubbers and other measures to limit emissions from refineries.

And, Mudge says, engines on ore-hauling trucks are getting more efficient. They use less fuel, with fewer emissions, per ton of ore.

But Hadder says mercury emissions are an even bigger problem, because mercury is toxic.

Mining companies do a good job following state regulations to prevent mercury emissions from refineries, Hadder says, but there are no rules governing "fugitive" mercury that escapes from leach pads, tailings and waste rock.

Great Basin Resource Watch is in talks with the state about plans to regulate fugitive mercury emissions.

PIT LAKES

Ask Miller and Hadder to name the biggest environmental threat mines pose, and they agree: pit lakes.

The lakes occur when groundwater seeps back into an abandoned open pit. The water can be toxic, with high levels of acid, and Nevada's pit lakes can be 2,000 feet deep - deeper than Lake Tahoe.

Northwest Nevada's Lake Lahontan, created by a dam on the Carson River, is the state's largest man-made lake, at 325,000 acre-feet. But in the next few decades at least three of the four largest man-made lakes in Nevada will be pit lakes, Miller says, and some will approach 450,000 acre-feet. Another 12 to 15 pit lakes will contain more than 50,000 acre-feet, equal to Reno's water consumption for a full year.

It's a big problem because the water that floods pit lakes is drinkable water from underground reservoirs, Hadder says. Along the Humboldt River Basin in Northern Nevada, forecasts call for more than a million acre-feet of water to end up in pit lakes, he says.

"We're losing valuable water to these pit lakes," Hadder says. "We're in a dry state here. We're fighting battles over water."

In addition, pit lakes harm migrating birds and waterfowl. Per regulations in the Migratory Bird Act, Newmont recently had to dump 1,900 tons of caustic soda in its Lone Tree Mine pit lake near Battle Mountain to balance the water's pH and make it safe for birds, Hadder says.

Acidic water is also easy to fix: Add lime to neutralize the pH balance, Miller says.

What's not as manageable is the human tendency to see water and want to play.

"People will want to fish in these lakes, and someone will stock them," Miller says. "But the slopes on these lakes can be very, very unstable. They're almost designed to fail. You may be taking a small raft or boat around a lake, and you can have large rocks come down on you."

Backfilling pits isn't practical because oxidizing rocks could taint groundwater. And the cost of replacing rock - $1 per ton, or $5 billion to replace 5 billion tons of ore mined - "isn't the best use of money or diesel fuel," he says.

Mining companies now fence off pit lakes. Miller says that's not enough to keep people out, but mining companies say they'll eventually do more.

Newmont's Lone Tree pit lake is "totally closed off and not accessible to the public," Mudge says. "Eventually, over the long term, the proper protections will have to be put in so people don't expose themselves. Once we get to the point where we allow public access, we will not let people close to those walls, maybe with a buoy system."

It's the least they could do, Miller says.

"There needs to be a policy established that you make access into the pit lake safe, because you've created an attractive nuisance."

RECLAMATION

Mining companies say they're doing everything possible, and then some, to protect the environment. Both Barrick and Newmont are listed on the Dow Jones Sustainability World Index, a global list of 300 companies identified as leaders in environmental stewardship, safety and social responsibility.

State and federal laws require mining companies to file reclamation plans when they ask for permits.

To comply with regulations, Barrick's Cortez mine has 18 people in its environmental department. The company will spend $5 million on reclamation at Cortez in 2012, including demolition of a retired mill.

The company doesn't wait until it's done mining to contour played-out leach pads and tailings dams to match nearby hills.

Barrick also plants native vegetation on contoured hillsides.

On a drive through reclaimed areas at Cortez, it's almost impossible to distinguish reclaimed hills from natural ones. The only clue you get is from the tour guide, who points out former leach pads.

Both Barrick and Newmont say they go above and beyond to protect Northern Nevada's flora and fauna.

Barrick agreed in 2008 to establish a seed farm employing members of the Shoshone tribe. They are collecting seeds from the adjacent land so the company doesn't have to buy non-native versions from far-flung nurseries.

Newmont is also working the countryside outside of its mines. The company installed fencing and developed new water sources for livestock to keep cattle away from trout habitats near Carlin. The company is working on an off-site plan to help protect the sage grouse.

The efforts "will help as we get approvals for new operations," Mudge says. "But it's also the right thing to do."

Great Basin's Hadder says he believes the mining companies' efforts to right the environment are mostly sincere.

"But they're also having some pretty big impacts on the environment," he adds. "And I would say they aren't really offsetting those impacts."