Diavik says mine closure on schedule, pits half filled

Diavik diamond mine managers say closure of the Northwest Territories mine is on schedule, with the three open pits about half filled with water from Lac de Gras, Cabin Radio reported.

General manager Gord Stephenson gave the update at a town hall in Yellowknife on Oct. 22. “We’re quite happy to be on track and on schedule with our closure timeline,” he said. Commercial diamond production ended in March after nearly 23 years.

Closure manager Sean Sinclair said filling, which began in July using nine siphons, should finish this winter. The water will be tested against environmental and cultural-use criteria before the pits reconnect to the lake. If it meets standards, the dikes separating the pits from the lake are expected to be breached next summer.

Major reclamation is expected to wrap up by the end of 2028, with final cleanup continuing into 2029. Diavik expects to leave the site by 2030, though environmental monitoring could continue in some areas until 2050.

Several large buildings, including the crusher and backfill plants and a powerhouse, have been removed. Stephenson said demolition started a year earlier than planned.

The workforce has fallen from 1,100 to 1,200 people during operations to about 400, with 150 to 200 on site at a time. Stephenson said employment should hold fairly steady through 2028 and then drop significantly.

The N.W.T. environment minister has approved winding down the mine’s Environmental Monitoring Advisory Board by March 31, 2027. “The wind-down of EMAB does not mean Diavik won’t be regulated,” Sinclair said, pointing to the Wek’èzhìi Land and Water Board and a traditional knowledge monitoring program with Indigenous partners that began this year.

An aerator in Frame Lake will run through a third winter. Fish reintroduction remains on hold, with another update expected next year.

Tom Hoefer, who worked at Diavik for about 11 years, said the company is following through on commitments made in 1998. “It’s the way mining should be done,” he said.

For more on the territory’s finances and mining, see our report on the N.W.T.’s forecast $39-million deficit and on the sale of Yukon’s Eagle gold mine.

Sources: Cabin Radio; Government of the Northwest Territories.

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