FAQs: Donlin Tailings Dam

Addressing Misconceptions About Dam Safety

Storyknife, September/October 2024 edition

Critics of the Donlin Gold Project have shared concern over a potential accidental release of toxic metals or chemicals into the Kuskokwim River.

They cite the failure of tailings dams in other countries, like the 2014 Mount Polley Dam failure in Canada or the 2019 Brumadinho dam failure in Brazil.

Experts involved in engineering and permitting the Donlin project are focused on the greatest level of safety. It’s why they designed the project’s proposed tailings facility to not be susceptible to the failures that occurred at Mount Polley, Brumadinho or other dams in recent times.

When designing a highway, aircraft or tailings dam, an engineer will never say that a project has no risk. “Very unlikely” is as close an engineer will get to saying there is no risk.

Misconceptions about project risks are rampant and it’s important to acknowledge and address concerns, even if a subject matter expert considered and addressed them previously. Here are some of the top concerns we’ve heard about the Donlin tailings dam and our responses.

Would the tailings dam withstand a major earthquake or flood?

Yes, and based on a site-specific study, the earthquake scenario used in designing the proposed dam is the ground motion equivalent to a 1 in 10,000-year earthquake. Also, in its certificate to operate, Donlin will be required to comply with a maximum water level below the crest of the dam to prevent the release of tailings or water during an earthquake or large storm on top of snowmelt. The maximum water level will be based on a site-specific study now underway to provide the most accurate estimate of future precipitation.

If there is a spill from the dam, what’s the likelihood and potential impacts to water quality from cyanide or mercury?

Because cyanide and mercury will be mostly removed from the waste stream ahead of time, the concentrations in the tailings will be too low to impact fish populations.

While the tailings facility is designed to prevent spills, if one happened, it could release tailings that could degrade fish habitat. The tailings include elevated levels of arsenic, antimony and thallium. The impact on habitat would depend on the specific circumstances of a spill. This is less of a risk after mining ends because the water would be drained from the tailings after mining.

Did the project consider a catastrophic dam break?

No, multiple catastrophic scenarios were considered—including a complete tailings dam failure. The catastrophic scenarios were carefully examined by a panel of 24 tailings dam experts who determined them to be “conceivable, but only under extreme circumstances” and very unlikely to happen. The environmental analysis for the project instead focused on spill scenarios that had the largest potential consequences but were reasonably foreseeable.

The dam is designed to prevent any of those scenarios from happening—by placing the tailings facility on bedrock in a valley surrounded on three sides; constructing the dam out of rock instead of earth; not using tailings for structural support; and many additional engineering safeguards.

Doesn’t the dam store materials that pose long-term hazards to the environment, even if the dam is safe?

The tailings won’t be acutely toxic to people or wildlife, but they won’t meet water quality standards. That’s why, under a permit, wildlife needs to be kept away during mining operations.

After mining, all of the surface water will be drained from the tailings, over a period of about 10 years. Then, the tailings will be capped with a soil cover and revegetated. Rainwater and snowmelt that accumulate on the soil cover are expected to meet water quality standards. If they don’t, the water will be pumped to the pit, where it will be treated and discharged in compliance with strict environmental standards.

Who is responsible if there is an accident?

Building and operating the Donlin project in a way that protects our people, the environment, and the resources we depend on is a top priority. Calista and The Kuskokwim Corporation will have oversight, along with dam safety regulators. The tailings dam alone will have weekly, monthly and quarterly reports that must be filed with regulators, but who is responsible for an accident?

Calista General Counsel Walter Featherly states, “Under its lease with Calista, Donlin and its owners are completely responsible for complying with all applicable state and federal environmental laws, and also for all costs and liabilities associated with a tailings release.”

“Donlin Gold—with Barrick and NOVAGOLD as the project owners—would be financially responsible for the cleanup cost of a tailings spill, should that occur,” says Chris Eckert, Donlin Gold Senior Environmental Coordinator.

Additionally, Donlin must create a cleanup fund before operations begin. This fund requires approval by the State of Alaska.