Fish & Fisheries

Bristol Bay Blog, Part 3: A Future for Salmon?


Editor’s Note: This is the final installment in a three-part blog series on the Conservancy’s recent research at Bristol Bay, conducted to provide a risk assessment of the proposed Pebble Mine.

Can one of the world’s largest mines be built in the headwaters of the world’s largest salmon fishery without disrupting the ecosystem?

That’s a question that generates a lot of controversy for the Bristol Bay watershed.

“There is a lot of vilification and name calling, but we wanted to go past that and get the data,” says Dave Albert, director of conservation science for The Nature Conservancy in Alaska.

The Nature Conservancy in Alaska commissioned an ecological risk assessment to improve understanding of baseline conditions near the Pebble deposit as well as potential risks such a mine could pose to salmon.

The baseline studies showed that juvenile salmon are ubiquitous in headwaters near the Pebble deposit, including documentation of more than 100 miles of previously unknown salmon streams. It also documented the purity of the water. “This is about the cleanest water in the world,” says Albert. “It’s not distilled water, but it’s pretty darn close.”

The ecological risk assessment used a cutting-edge stream modeling system to investigate potential effects of large-scale mining facilities including open pit mines, a tailings impoundment and waste rock dumps on stream headwaters.

The model results indicate potential for significant negative effects, including up to 60 percent reduction in stream flows near the pit and contamination from waste rock that could exceed Alaska water quality standards. The giant waste rock piles generated by mining would require active pumping and water treatment; if these systems failed, the levels of copper in the river could rapidly exceed lethal levels for salmon.

According to the researchers: “Our study shows that while some of the flow and water quality changes brought about by mining could be ameliorated by ambitious mitigation measures and water management plans, severe water quality effects could result from even a brief failure of these systems.”

The proposed mine dwarfs all other mines in Alaska combined; because the ore exists in low concentrations preliminary designs developed by the mining company show the mine covering twenty square miles with a massive tailings impoundment. From preliminary information released by the company, this tailings pond would require perpetual mediation in an area known for active earthquakes.

“We haven’t seen a detailed mine and water management plan, but it would be difficult to envision a project of this scale that does not require active management, basically forever, to avoid contamination,” says Albert.

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