Equipment removed; time for nature to reclaim Diavik mine pits

Rio Tinto’s Diavik Diamond Mine has begun filling its mine pits with water from Lac de Gras, marking a significant step in the site’s reclamation, says the company.

After a successful decommissioning phase that involved removing equipment from the underground and open pit mines, siphons were activated at Diavik’s A21, A418, and A154 mines over the last several weeks, stated a Thursday release.

Pit filling is expected to take approximately six to 12 months. Each siphon is designed for a peak flow of 850 litres of water flow per second, with nine siphons in total across the three mines.

Diavik Diamond Mine General Manager Gord Stephenson stated: “We are very pleased to have reached this milestone in the progressive reclamation of Diavik.

He continued: “Our goal is to leave the mine site in a safe and stable state and taking this step towards reconnecting our mine pits to Lac de Gras brings us closer to that goal. We remain committed to closing Diavik responsibly, with care, and in collaboration with Indigenous Government partners and regulators.”

The rate of filling will depend on water levels in Lac de Gras, with controls put in place to ensure that the process has minimal impact on the surrounding lake and downstream river. Fish screens have been installed over the siphons to ensure the safety of local wildlife, read the release.

Once filling is complete, Diavik staff, community members and regulators will monitor water quality in the pits.

Once the water quality is deemed to meet acceptable criteria, the pits, which were situated beneath the lake prior to mining activity, will then be reconnected to Lac de Gras.

The filling of Diavik’s mine pits is central to its Final Closure and Reclamation Plan, stated the release, approved in March by the Wek’èezhìi Land and Water Board.

In late July, Traditional Knowledge monitors visited site to observe elements of Diavik’s closure, including the pit filling process. Diavik remains on schedule to complete active closure activities by 2030.

And on Thursday, Cabin Radio reported the GNWT has granted Diavik’s request to shut down an independent oversight board for the diamond mine by the end of March 2027.

The Environmental Monitoring Advisory Board, reports Cabin, was established as a requirement under the environmental agreement for Diavik.