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Frequently Asked Questions

Tailings and Tailings Storage Facility

Tailings are a silt-like waste product that can contain metals and other material that should not be released to the environment. Instead, they will be sent to a tailings storage facility (TSF) that has been excavated down to bedrock and covered with a synthetic liner similar to ones used in newly designed city landfills and sewage lagoons.

The TSF, or “tailings dam,” will cover about 2,350 acres and will be about 1 mile wide and 1.75 miles long. The tailings dam will be about 180 feet at the beginning of operations and will be periodically raised, reaching a height of over 460 feet by the time the mine closes. It will have a total capacity of approximately 335,000 acre-feet of mill tailings, decant water, and storm water.

Downstream dams are considered the most stable, particularly in seismically active areas, and the most suitable for retaining large volumes of water. This type of dam has worked exceptionally well for over a century, experiencing only one minor incident since the 1900s. It’s the same type of dam that Kinross built at Ft. Knox that rode out the 7.9 Denali Fault earthquake in 2002 with no problems at all.

Donlin Gold is not located in an active earthquake zone. The tailings dam, however, will be engineered to withstand a large-magnitude earthquake.

The Donlin Gold tailings dam design (downstream) is completely different than the failed Mt. Polley dam design (modified centerline). The rock-filled, downstream design situated on bedrock eliminates the factors that caused the Mount Polley dam failure .

The tailings dam will be regularly inspected and monitored for safety and stability, including daily inspections by Donlin personnel. Independent, third-party engineering reviews will also be conducted periodically by the State of Alaska’s Dam Safety Program.

Yes. Tailings liners are not required by the Alaska Dam Safety Program for permitting tailings dams in Alaska, but the proposed synthetic liner represents best practices, reducing risk of impacts to water resources during operations and over the long term. The project chose to include the liner for extra protection based on input from landowners. The liners have been tested under many conditions, such as freezing, earthquakes, and forest fires.

Cyanide and Mercury

Cyanide is a natural chemical found in low concentrations throughout nature, including fruit, nuts, plants, insects – and the waters of the YK region. It has been used in mining and many other industries (e.g., dying blue jeans) for well over 100 years and can be used safely and without harm to the environment.

A very safe and stable form of cyanide – dry sodium-cyanide briquettes – will be shipped to the mine site in sealed steel ISO (International Standard Organization) tanks. These containers are state-of-the-art in the mining industry and their track record for preventing spills is exceptional.

Cyanide will be used to dissolve the gold from the crushed rock slurry. Dry sodium cyanide briquettes will be shipped to the mine site in sealed steel tanks. The briquettes will be dissolved and used as a low concentration cyanide solution within the enclosed processing facility. You can see where cyanide is used in the mining process on the Project Development page. 

After use in the processing facility, cyanide will be broken down into its component parts (carbon and nitrogen). Before being placed into the TSF, cyanide will be removed by proven methods to levels protective of wildlife.

Mercury occurs naturally in the rock at the Donlin Gold site and would need to be separated, recovered and disposed of properly.

Donlin Gold will capture 99% of mercury air emissions. This emissions level will be well below levels allowed by regulation. There are six points in the ore processing stream where mercury can be captured: pressure oxidation, hot cure, electrowinning, retort, refinery furnace and carbon regeneration kiln. Mercury that is captured during the milling process will be shipped out of state in specially-designed containers to a federally-approved storage facility in the lower 48. All mercury waste will be carefully tracked through each stage of generation, storage and transport. You can see how mercury is handled in the mining process on the Project Development page.

Water Management and Monitoring

While it is true that some “fish supporting” waterways would be removed, most of the miles lost represent very small tributaries that do not support aquatic life populations.

All water that comes into contact with the mine area will be treated prior to discharge. The discharged water will be treated to meet state of Alaska drinking water standards.

Treatment begins before the mine is even operational, continues through the mine’s operating life and for however long it takes after the mine closes. Water will be treated from the wells used to pump groundwater so the open pits can be excavated, along with runoff water from mine facilities, water from a drain below the lined tailings storage facility and dam face and some precipitation water from the tailings pond. The Water Resources Management Plan can be found here.

The Alaska Department of Environmental Conservation regulates discharged water in the state under the Alaska Pollutant Discharge System permit process.

Reclamation and Closure, Ongoing Monitoring, and Financial Assurance

A reclamation and closure plan is required by law to ensure that when mining activities are complete, the mine is closed properly and the land is returned to stable conditions. Reclamation will occur continually over the life of the mine and will include:

  • Removing structures
  • Removing water from tailings
  • Regrading, covering, and revegetating waste rock and tailings facilities
  • Ongoing monitoring

 

To make sure the mine is properly closed – and to pay for water treatment for as long as it is needed – the law requires the mine operator to provide financial assurance to the state. This can take the form of a bond or other financial commitments that are independently verified and approved by regulating agencies.

Donlin Gold will be required to put up enough money and provide rigid financial assurances, like a permanent fund, before any work can be done at the site that there will be enough money for closure and water treatment.

As required by state regulations and permits, Donlin Gold’s Reclamation and Closure Plan addresses both site closure and reclamation, along with long-term care and maintenance, including plans for water management and treatment to meet standards for as long as needed. The financial assurance will cover the costs of these activities. You can find the Reclamation and Closure Plan here.

Feasibility Study

The decision to “build” or “no build.” If the feasibility study concludes with “no build,” then the options are to either go back and do another round of research and planning, stop the project entirely, or let the project go stale until new information arises. The decision on which step to take is based on investor interest. If the feasibility study concludes “build,” the project team looks for investors to move forward with construction.

It is not a regulatory requirement, but it is a tool that investors use to assess their potential investment risk and return. It is used for financial decision-making.

After 10 years, the companies may employ different people than those during the last feasibility study update. It is important to go off current company expertise to ensure they have the technical ability needed for the project.

A third-party compiles information and then writes the feasibility study. It is then reviewed by professionals, including technical groups, engineers, and environmental experts, to ensure accuracy. The final package is shared with investors, as the final product is a document that indicates if the project is a financially sound investment.

Ideally, the information in the study points to the project moving forward.

The timing of the feasibility study is very important. If it is launched before all the research takes place in the technical reports, the study could conclude that there is insufficient information to show that the project is feasible. The project is currently in the phase of collecting this technical information.