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New Gold's New Afton mine, west of Kamloops, B.C., Feb. 2, 2021.Dennis Owen/The Globe and Mail

One person is presumed dead and another two were injured after an accident at a gold mine in interior British Columbia.

New Gold Inc. said in a release that a mud rush occurred at its New Afton underground gold mine west of Kamloops early Tuesday morning and that a contract driller had likely died. Two other individuals suffered non-life-threatening injuries.

The Vancouver-based miner has suspended production at the site while an investigation into the accident is being conducted by the RCMP, B.C.’s Ministry of Mines and the company’s internal team.

Mud rushes are caused by a sudden and uncontrolled deluge of water and debris breaking through cracks in an underground mine. They are more common outside of Canada because they tend to occur in “block cave” mines, which are a rarity in this country.

Unlike a typical underground mining operation in Canada, which usually involves mining relatively small amounts of rock from targeted stopes, block caving entails moving much larger amounts of rock over wide areas.

The New Afton mine is located about 350 kilometres northeast of Vancouver and is New Gold’s second-biggest operation. It went into production in 2012 and last year produced 64,000 ounces of gold. New Gold also operates the Rainy River mine in Ontario.

“The thoughts of the board of directors and management are with the family, friends and colleagues that have been impacted by this unfortunate incident,” New Gold said.

Shares in New Gold fell by 7.6 per cent on the Toronto Stock Exchange to close at $2.44 apiece.

New Gold was aware mud rushes could happen at New Afton and had taken steps to prevent them.

In a 2007 New Gold technical report prepared by Hatch Ltd., the engineering firm wrote that the potential for mud rushes was elevated at New Afton. Four elements are necessary for mud rushes to occur underground, Hatch said. Those are water, mud-forming materials, an event that could trigger the movement of materials, and cracks through which the deluge can enter the mine.

“All four elements appear to be present at New Afton,” the report said. “There is concern regarding the potential for a mud rush phenomenon to occur.”

Hatch proposed a number of approaches that could minimize the risks of mud rushes at New Afton, including pumping out large amounts of excess water that had accumulated in a large open pit at the surface.

As recently as last year, mining consultant Roscoe Postle Associates Inc. also wrote about the possibility of mud rushes at New Afton. In a technical report published by New Gold, RPA pointed out that while New Gold had systems for monitoring and mitigating the risks, more could be done. RPA said the company could treat tailings stored at New Afton “until the tailings are stable and non-flowable in order to minimize the risk of a mud rush to underground workers.”

New Gold chief executive Renaud Adams declined an interview for this story.

“Once a full investigation is completed, we will be in a position to discuss this incident,” Anne Day, New Gold’s vice-president of investor relations, wrote in an e-mail to The Globe and Mail.

Ryan Henley, a mining analyst with Laurentian Bank Securities, said the accident is unlikely to result in an extended shutdown at New Afton.

“I would assume it’s in a part of the mine that isn’t a main source of ore,” he said. “If this was a big event, this would be impacting 10, 20, 30 people – not three.”

As a mining method, block caving is more common in Australia. Melbourne-based Newcrest Mining Ltd. is considered the industry leader in the method. Block caving is particularly suited to bodies of ore that are uniformly dispersed and large in area.

In many historic underground mining districts in Canada, such a Red Lake, Ont., gold deposits tend to be erratically dispersed and are much more suited to be mined in small blocks about the width of a sidewalk.

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