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Remediation work paying off at former Cobalt mines

It’s been a quarter-century since Agnico Eagle Mines actively mined silver in Cobalt, yet its presence is ubiquitous as remediation of old mine workings continues. Between 1905 and 1930, 100 mines and 18 mills were operating in Cobalt.
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Remediation

It’s been a quarter-century since Agnico Eagle Mines actively mined silver in Cobalt, yet its presence is ubiquitous as remediation of old mine workings continues.

Between 1905 and 1930, 100 mines and 18 mills were operating in Cobalt. The area’s mining heritage is rich, but it also comes with its share of hazards: tailings discharged in lakes, stopes left uncapped, gaping chasms where veins were mined.

“Here, it’s full of the history of mining,” said Jean-Francois Doyon, Agnico Eagle’s sustainable development specialist. “There are mine hazards everywhere, there are former mills everywhere, there are tailings everywhere, so how do you address that? The law was not written for historic cases like that, so we have to write the book.”

The company originated as Cobalt Consolidated Co. in 1953 as an amalgamation of six companies. By 1957, it had reorganized as Agnico, and in 1972 merged with Eagle Gold Mine to become Agnico Eagle, when it diversified into gold.

In the late 1980s, with a dip in the price of silver, Agnico put all its Cobalt operations on maintenance. Eight years later, it decided to focus exclusively on gold, which was easier to extract and gave a better return on investment, and eventually, it moved out of Cobalt altogether.

The case for remediation came in 1987 when a sinkhole opened up at the Town Site Mine, creating a major safety hazard. It sparked an about-face within government and helped put into play the safety and remediation standards of today, Doyon said.

It’s been a costly and difficult task. Agnico Eagle holds mining rights for more than 200 properties through Cobalt and the surrounding area, so its responsibility is extensive. Doyon and his team monitor remediation work done to date and watch for new hazards opening up.

Over the last five years, Doyon has worked to recapture some information that went missing following the closure of Agnico’s Cobalt office in 2001, poring over annual reports dating back to the 1950s to piece together a list of the properties Agnico owns and gathering details about mine workings.

Invaluable to the process have been former geologists and miners themselves. Doyon said he often brings former Agnico employees who live in the area into the field with him.

“Finally, I know exactly what we have mined over the past 50 years,” Doyon said. “I know exactly what year and what amount of ore we hoisted, I know what amount of ore we’ve milled, which mill we used, which tailings, and what was discharged.”

Remediation can be a frustrating experience. Acceptable standards from the 1990s when Agnico began the work — before the Mining Act was amended — are now obsolete and many areas have to be readdressed.

There is also the human factor. A few years ago, Doyon added warning signs to areas frequented by the public to acknowledge the hazards contained within.
“I have a responsibility to warn them, since I’m the mining rights holder,” he said.

But despite the hazards, people continue to enter restricted areas. It’s not uncommon for Doyon to come across sections of fencing that have been cut open. He reinspects the fencing every two years and does repairs when he finds them, but with 15 kilometres of fencing across its properties, it’s a monumental task.

The site of the former Nipissing Low Grade Mill, now known as the Nip Hill Lookout, is a popular place with visitors for its extensive ruins and sweeping vistas. The massive mill operated from 1912 to 1918.

There are a number of hazards on the site — open cuts where silver was extracted, piles of loose waste rock, and considerable mill ruins — but it’s also one of Agnico’s successful remediation stories.

Formerly a valley filled with tailings, rehabilitation work began there in the 1990s and it’s now almost entirely revegetated. Water monitoring still continues on site, including an extensive surface water study done last year.

“It’s a sampling project to assess the current state, and we’ve established the sampling station upstream and downstream to see how it’s evolving — before and after sources of potential contaminants — and then installed couple of water monitoring wells,” Doyon said.

He’s learned a lot about the resiliency of nature over the years.

At nearby Cobalt Lake, in which tailings were discharged until the 1960s, the natural process of rehabilitation has restarted. It’s still not recommended for swimming, and there’s plenty of work to be done, but aquatic life is returning.

High contaminant levels reported in a government study two years ago caused concern, but Doyon noted that the study also showed the presence of fish and benthic vertebrates.

“If you’re just looking at the contaminant level, it should be a desert and there should be no aquatic life in there,” said Doyon, a fish biologist who studied at Montreal’s McGill University. “But there is some.”

He came up with a hypothesis: if discharge into the lake ceased for 50 years, rain and snow accumulation would provide some natural runoff into the lake, which would filter sediment on top of the tailings. Doyon then discovered a rate of sedimentation in the lake of one millimetre per year. If he applied the same rate over 50 years, he reasoned, there should be five centimetres of sediment, enough for aquatic life to sustain itself.

“So I did a study, and I took a vertical profile, and we realized that there were between four and 10 centimetres on top of the tailings,” Doyon said, noting that fish were also present in the area of study. “You could see the difference in colour and you could see there was some vegetation on top of the sediment.”

Though the work will never be completely done, Doyon estimates within 10 years the company should have a handle on the remediation work.

Government standards require the company to produce an updated remediation plan by the end of the year, and then another one every year for the next four years.

“But with each closure plan, it’s not saying the job is done,” he emphasized. “It’s saying this is the state of the situation, and this has been done, but we still need to do it to protect the environment or the safety of people.”

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