Tom MacFarlane, the deputy minister at the Department of Natural Resources and Energy Development, offered the estimate to MLAs during a committee meeting recently in Fredericton. 

MacFarlane said the province remains hopeful another company will buy Caribou and resume mining.

"If the mine continues to operate, then we would look at new operators to take that on," MacFarlane said of the water treatment. 

Tom MacFarlane, the current deputy minister in the energy department, said if no new operator steps in, the province would develop a plan to close and remediate the site. (Jacques Poitras/CBC)

The province has taken on more responsibility at the mine after the financial collapse of owner Trevali Mining Corp. 

Production halted at the mine about 55 kilometres southwest of Bathurst last summer, and it was placed into a care and maintenance mode. 

While extraction was stopped last year, acidic water is still being pumped out of the underground mine and needs to be treated before being released. 

This week Trevali's New Brunswick division, Trevali N.B., will be placed into receivership. That's a process to liquidate assets to pay secured creditors. 

Receivership will see the last Trevali employees terminated, leaving no one to continue water treatment and secure the mine site.

The province in court filings has said it will step in with a contractor, though hasn't said what company will be used.

Trevali purchased the mine in 2012. It includes an underground mine, open pit mining sites, a mill, tailings ponds and dams. (Trevali)

The prospect of the province covering water treatment for sometime into the future is a concern earlier this for David Coon, the leader of the New Brunswick Green Party. 

"My concern is that once again, the province of New Brunswick is going to be stuck with having to manage the environmental cleanup and ongoing water treatment at another mining operation, or defunct mining operation, in New Brunswick," Coon said earlier this month.

While MacFarlane said the province hopes a new operator will take over the mine, there was no interest from anyone in buying the mine last fall. 

MacFarlane said if no new operator steps in, the province would develop a plan to close and remediate the site. 

Under a 2013 agreement between the province and Trevali, the New Brunswick government agreed to cover two thirds of the environmental cleanup costs at the mine. 

That meant Trevali provided the province with several million in cash and bonds to cover its share. 

MacFarlane told MLAs the province's two-thirds share is estimated at $42 million. 

It's unclear how long the province would be willing to wait for another operator before proceeding to remediation. 

MacFarlane said once remediation is complete, the water treatment cost would drop to zero.