Will we have wild salmon in 100 years? The answer depends on how we do at places like Bristol Bay. Photo: Clark James Mishler/TNC
by Matt Miller, senior science writer
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.
The ecological 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. Photo: Clark James Mishler/TNC
Following a report on the findings, The Nature Conservancy’s Alaska board of trustees recommended four conditions that a large-scale mine should have to meet in this watershed to proceed. To summarize:
- The risks and habitat alterations posed by the mine should not be done in a way that puts the long-term sustainability of the salmon fishery at risk.
- Water withdrawals should not be allowed to exceed the ecological flow needs for salmon.
- Mine plans should avoid the need for active water quality management systems that must be maintained in perpetuity to avoid contamination.
- The technology to control this acid mine drainage should not be experimental. It should be demonstrated at similar sites and on similar scales before being attempted at Bristol Bay.
“This is a high bar,” says Albert. “The Nature Conservancy is not against mining. But we believe this is not the place to develop experimental technologies. This is not the place to have a project that requires mitigation in perpetuity.”
Formal mine plans have yet to be released, but now the Conservancy has the tools and framework necessary to evaluate those plans in the near future. It has also provided the data to agencies evaluating the mine, including the Environmental Protection Agency for its watershed assessment, a peer-reviewed plan released this week. The EPA is now soliciting public comments on the plan.
“We continue to be as hard-nosed relying on the data,” says Albert. “Our best role is to inform the broader debate without becoming embroiled in politics. We believe that the board of trustees’ resolution provides a solid basis for moving forward with evaluation of future mining proposals.”
The information gathered will be vital in determining the fate of this place, a place where everything from trees to bears to people are still nourished by salmon.
“Will we have wild salmon in 100 years?” Albert asks. “The answer depends on how we do in places like this.”
Jennifer Miller and guide Taylor Wells bring in a trophy rainbow trout on one of the many rivers of Bristol Bay–one of the finest places for outdoor adventure left on earth. Photo: Matt Miller/TNC
Opinions expressed on Cool Green Science and in any corresponding comments are the personal opinions of the original authors and do not necessarily reflect the views of The Nature Conservancy.