The problems at Red Dog, one of the world’s largest zinc mines, show how climate change poses a challenge to the economy of the region, which is warming at triple the rate of the global average.
Vancouver-based Teck Resources Ltd. says to Alaska Public Media that permafrost thaw in the watershed surrounding Red Dog is releasing higher natural levels of dissolved minerals and other particles into streams. That, in turn, has limited the mine’s ability to discharge its own 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” are below a certain threshold", said Wayne Hall, community and public relations manager for the mine to Alaska Public Media.
Record high warmth
"That threshold", he added, "had never been exceeded before the summer of 2019, which saw record high warmth".
Teck had to pump hundreds of millions of gallons water out of the reservoir into the bottom of Red Dog’s active mining pit, forcing Teck to mine lower-grade ore toward the top of the pit rather than the higher-grade ore at the bottom.
Red Dog also removed tens of millions of gallons more from the reservoir by freezing it into an icefield, and accelerated a planned boost to the height of the reservoir’s dam. Teck official said the cost was in the range of $19 million.
Causing permafrost to thaw
The new discharge-related problems at Red Dog come as temperatures in the surrounding Northwest Arctic Borough have risen sharply.
"The borough’s annual average temperature was about 20.5 F in 1990, and since then it’s risen about 5 degrees", according to Rick Thoman, climate specialist at the Alaska Center for Climate Assessment and Policy.
"The warming appears to be causing permafrost to thaw, which releases more sediments and minerals into the watershed upstream of Red Dog", said Hall, the mine official.
And that theory aligns with what one Alaska permafrost expert says that scientists are observing in the region.
Red Dog started up in 1989, in a unique partnership between NANA and Teck. It generated $1.6 billion in revenue last year and $700 million in gross profits, according to Teck.