After 50 years of toxic seep, mine cleanup to begin soon

Acid drainage left over from old mine leaking toward Taku River

Posted: Sunday, October 19, 2008

Forty miles northeast of Juneau, just past the Canada border, a bright-orange stream trails from an old mine shaft 100 feet down a bare hillside and into an orange pool. The metals in the orange water have been leaking into the Tulsequah River and on into the Taku for a half-century. After 50 years, the Tulsequah Chief mine is scheduled to reopen. But before they start chasing the gold, silver and other metals, the new miners must clean up after their predecessors. Their operating permit requires it.

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Michael Penn / Juneau Empire
Michael Penn / Juneau Empire

"It's ugly to look at, but it's the way things were done in the 1950s," said Redfern Resources Ltd. project manager Mike Allen. "We've learned from their mistakes. The mining industry has learned."

This cleanup has been a long time coming.

In 1951, Cominco Ltd. opened the Tulsequah Chief mine. Six years later, metals prices dropped and the mine was closed.

They left their tunnels, their railway tracks and yellow railcars, old generators and compressors, surveying equipment and other parts. According to Allen, the miners were so sure they were coming right back that they left dishes laid out on the table at camp, ready for the next shift to be served.

They lay there for decades. The yellow railcars are still parked on the hill to one side of the mine shaft. Allen speaks of the "old-timers," and "legacy." Some of the old tunnels will be filled and sealed, but others will be modernized and used in the new mine.

"The toehold they left here, it's definitely a help for us," Allen said.

They also left their acid mine drainage. It is now leaking at 5 liters per second, according to the company.

Certain kinds of rock, common in this part of the world, generate acid when they're exposed to air or water through the natural process of oxidation. Disturbing those rocks in construction or mining greatly speeds up the process of exposing the rock. Acidic water picks up metals that harm fish and other wildlife.

It doesn't help that the mine was engineered with drainage in mind; the tunnels slope toward the hillside slightly, ensuring that all the acid gets out.

The modern tunnel mine is designed to tip the opposite direction, downward into the hillside, precisely to avoid draining the acid into the watershed.

British Columbia's provincial government first issued a pollution abatement order to Cominco in 1990 to clean up the old mine site. That responsibility shifted to Redfern when it bought the mine in 1992. Redfern is owned by Vancouver-based Redcorp Ventures Ltd.

A Ministry of Environment consultant then reported that tests on rainbow trout showed the discharge was "acutely toxic."

Downstream, algae, normally the fundament of a healthy food chain, were not thriving. Fish and sediments bore high metals concentrations. The report directly linked these troubles in the water to the discharge coming from the old mine shaft, and said the possibility of harming fish was "significant."

Downstream is the Taku River, whose commercial and sport fisheries were worth more than $7 million with an average annual employment of 120 people, according to a 2004 economic impacts report paid for by the United Southeast Alaska Gillnetters. Another report estimated 130 people fished the Taku for personal use.

Canadian permitters did not respond to a request for an interview.

Geophysicist David Chambers, at the Center for Science in Public Participation, estimated from the ministry's 2003 flow data that the old mine was leaking 23,861 pounds of zinc, 5,099 pounds of copper, 122 pounds of lead, 97 pounds of cadmium, and 49 pounds of arsenic a year into the watershed.

Not all the waste rock from the old mine is generating acid. Still, all 60,000 cubic meters of it will be treated as if it were acid-generating rock, and much of it is.

Last year, orange water lined the mine site in a long strip. Now, from the air, it appears largely contained into a holding pond on the Tulsequah riverbank.

Redfern plans to contain the old waste rock near the mine site, isolating it with a liner below and a cap above. Workers will install a drainage system, so that any water that touches the pile heads to a treatment plant before entering the watershed.

Redfern will install the water treatment plant after it finishes building the last and rockiest section of road to the mine site from its main camp and barge landing sites. That has been delayed but is scheduled to be done by the end of the year, Landstad said.

During the mine's life, the old waste rock and the potentially acid-generating rock from the modern mine will be mixed with cement, which neutralizes the acid, and backfilled as a paste into the new mine's tunnels.

As part of the closure of the mine, Redfern will flood the tunnels that haven't been sealed off, keeping potentially acid-generating rock there from oxidizing further. On the surface, Redfern will restore topsoil removed during construction and allow the area to re-seed naturally.

"The goal is shut down, walk away. This will be a flat spot," said Allen, gesturing toward the mine.

Once in production, the mine over eight years is expected to produce 1.7 million ounces of silver, 50,000 ounces of gold, as well as zinc, copper and lead, with the "strong likelihood" that more ore will be found, the company says.

Rivers Without Borders' Chris Zimmer said the benefit of removing toxins from the Taku probably wasn't enough for him to support the development there.

"I think the issue is, this is the wrong mine in the wrong place," he said.

He has organized opposition to the mine's plan to transport materials on a hoverbarge on the Taku, saying it is likely to damage sensitive habitat there.

"They really haven't given (the acid drainage) the attention it deserves, but maybe that's changing now," he said. "The questions are, why is it taking so long here, and how comprehensive is this going to be?"

At the Alaska Department of Natural Resources, permitters have long known about the acid. But they have no jurisdiction over the Canada mine's operations. DNR's large mine permitting coordinator Tom Crafford said the cleanup is a potential benefit of the mine's development.

"That's the hope," he said.

• Contact reporter Kate Golden at 523-2276 or kate.golden@juneauempire.com.



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