Acid Leaching into Salmon-Rich Yukon River Feared Under Proposed Copper Mine

By Bob Weber, THE CANADIAN PRESS

Ask Eddy Skookum about the importance of the salmon-rich waters of the Yukon River to his people and he doesn’t hesitate.

“It’s very, very, very important,” says the chief of the Little Salmon Carmacks First Nation. “It’s just like the blood in your veins.”

But Skookum worries that those waters – home to the longest salmon run in North America – are threatened by a proposed copper mine almost on the banks of a creek a few kilometres upstream from the river. He, like Yukon environmentalists, fears plans to use a mining technique new to the North could result in vast quantities of leaking sulphuric acid.

“We don’t have nothing against mining. We like the employment,” Skookum says as the plan enters the last days of the regulatory process.

“But there are a lot of unanswered questions to be asked.”

Driven by copper prices that have nearly quadrupled in the last five years, Vancouver-based Western Copper plans an $150-million open-pit mine on Williams Creek, about 13 kilometres northwest of Carmacks, Yukon.

The mine, which would create 200 construction jobs and 180 mining jobs at the peak of the project’s estimated eight-year life, was given preliminary approval by the Yukon’s regulator last December. The company hopes to begin construction this spring.

A process called heap leaching would be used to separate the metal from the ore. In heap leaching, ore is crushed, piled on an impermeable plastic liner and soaked with sulphuric acid. The acid dissolves the copper and is pumped out from the bottom of the heap.

The method is cost-effective, produces copper that is 99 per cent pure and is the only way to deal with the type of ore present near Carmacks, said Paul West-Sells, Western’s senior metallurgist.

Western’s heap, on a hillside adjacent to the creek, would eventually cover 31.5 hectares and use 25 kilograms of sulphuric acid for every tonne of ore.

But what happens to that heap when the ore’s all gone?

“That’s when the trouble really begins,” says Gerry Couture of the Yukon Conservation Society.

Western’s plans to clean up the mine involve trying to neutralize the pile’s acidity, covering it with dirt and replanting it.

Couture points out that nobody has ever successfully fully neutralized a leach heap. He says rain and snow will filter down through the dirt cover and eventually bring the water table up over the dirt dike that separates the massive, acid-soaked rockpile from the creek.

As well, he says that the plastic liner under the heap will likely eventually fail, opening another pathway for the acid to drain into the environment.

Heap leaching is most commonly used in dry areas like Arizona. It has never been proven in the North, Couture says.

The Yukon Environmental and Social Assessment Board acknowledged that heaps have only been successfully neutralized in tests.

“These scaled-down tests do not provide absolute certainty with respect to predicting the chemical stability of the heap,” its report says. “Furthermore, the proposed heap leach pad liner and cover may not function optimally.”

Still, the board decided the risks could be managed.

Couture isn’t so sure.

“We feel there’s a substantial chance that sometime in the future this heap is going to start leaching,” he says.

A mistake could jeopardize a major resource of his people for decades to come.

“If the sulphuric acid leaches into the river, I’m pretty sure it’ll kill everything in its path,” he said.

Every year, between 15,000 and 25,000 Chinook salmon run down the Yukon past Carmacks. Williams Creek is also an important nursery stream.

In addition, the Yukon boasts trout, arctic grayling, whitefish, pike and burbot. It supports a small commercial fishery and is a virtual grocery for area aboriginals, including the 500 or so members of Skookum’s band.

“Many of us have a staple diet of fish – at least twice a week,” he says.

Western officials declined to comment on environmental concerns while the regulatory process is ongoing.

Comments on the board’s preliminary approval will be accepted until Feb. 6. The final decision rests with the Yukon cabinet.

The Yukon River, which runs 3,700 kilometres from northern British Columbia through the Yukon and into Alaska before draining into the Bering Sea, has often been contaminated in the past by poor mine cleanups. Skookum wants to prevent that from happening ever again and he insists Western should develop a better cleanup plan.

“We know it’ll be expensive,” he says. “But how expensive is a way of life lost?”