De Beers Canada is defending its plan to close the defunct Snap Lake diamond mine and reclaim the site and surrounding area amidst some disagreement about the science behind its proposal.
The diamond company faced questions on its application to renew the mine's water licence from the territorial and federal governments and the Mackenzie Valley Land and Water Board at a public hearing in Yellowknife Tuesday.
The current licence is set to expire in 2020 and a new one has to be issued before the final closure and reclamation plan can be approved.
The underground Snap Lake mine, located 220 kilometres northeast of Yellowknife, opened in 2008 and was De Beers' first diamond mine outside of Africa.
While the mine was expected to produce diamonds for 15 years, in December 2015, the company announced it was closing the mine which it said was a "troubled operation" from the start. The site was then put under a temporary closure phase called care and maintenance.
At the hearing, representatives from the territorial government expressed concern about the amount of waste that could be deposited into Snap Lake. They also questioned the accuracy of De Beers' water models, suggesting its estimates are too low.
But De Beers said its application is based on years of research and scientific data and that its proposal prioritizes environmental protection.
"The proposed application submitted will continue to ensure the water will be safe to drink and the fish will be safe to eat," Erik Madsen, lead of corporate affairs for De Beers, told CBC in an email.
He also said when it comes to discharging water into Snap Lake, it will be less than two per cent of the peak water flow when the mine was in operation.
De Beers and the territorial government also disagree about the amount of financial security required. These are funds provided by De Beers that the government will hold and return to De Beers once the mine has been closed and the site reclaimed, or used to complete the project should De Beers abandon it.
The government has recommended the security estimate be increased by $2,047,811 to a total of $87,520,940. But Madsen said the amount De Beers has proposed "reflects the activities that are being proposed for care and maintenance and closure."
A representative from the water management and monitoring division of the territorial Department of Environment and Natural Resources said the review process of De Beers' application is important as Snap Lake is the first of four diamond mines to enter closure in the N.W.T. The representative also said scientific disagreements are common.
The mine was allowed to flood with water at the beginning of 2017 and De Beers announced plans to close it for good. It submitted its final closure and reclamation plan to the Mackenzie Valley Land and Water Board in March 2019.
De Beers' proposal includes two phases. The first spans eight years and includes: decommissioning facilities, capping the North Pile, a surface disposal facility used to store processed kimberlite and waste rock, water management, and reshaping and re-vegetating land. The second post-closure phase is anticipated to last at least ten years and includes long-term monitoring.
That plan has completed the preliminary screening process and De Beers said it expects the plan will be approved in 2020.
The Mackenzie Valley Land and Water Board has the final authority on whether it will renew the water licence and approve the closure and reclamation plan. The public hearing continues Wednesday.