ANCHORAGE, ALASKA — A company operating one of the world’s largest zinc mines in northwest Alaska said thawing permafrost linked to global warming forced an expenditure of nearly $20 million on water storage and discharge management.
Teck Resources Ltd. says permafrost thaw in the watershed surrounding the massive Red Dog Mine is releasing higher natural levels of dissolved minerals and other particles into streams, Alaska’s Energy Desk reported.
The Vancouver-based company said the release limited the mine’s ability to discharge its treated wastewater into a nearby creek, causing water to back up in its tailings reservoir.
Red Dog can only discharge from the reservoir when the creek’s naturally occurring levels of total dissolved solids fall below a threshold, community and public relations manager Wayne Hall said.
The threshold was never exceeded before the summer of 2019, which saw record high warmth, Hall said.
“In 30 years of Red Dog operation, this is the first time that we’ve ever seen background levels in the creeks to the point where it precluded us from discharging,” Hall said.
Red Dog resumed discharging last week following the construction of a new wastewater treatment system using reverse osmosis.
Teck took various steps to keep water levels in the reservoir from getting too high while the system was built.
The measures included pumping hundreds of millions of gallons water out of the reservoir into the bottom of Red Dog’s active mining pit, forcing the company to mine lower-grade ore toward the top of the pit rather than higher-grade ore below.
The mine also removed millions of gallons more from the reservoir by freezing the water into an ice field and accelerating a planned increase of the reservoir’s dam height.
Red Dog opened in 1989 in a partnership with NANA Regional Corp., the Alaska Native corporation that leases the mine property to Teck.
The mine generated $1.6 billion in revenue last year and $700 million in gross profits, Teck reported.