Sustaining the environment in the Yukon Kuskokwim (YK) region is one of the top priorities of the Donlin Gold project. For the past several years, Donlin Gold has been conducting numerous environmental studies to evaluate the possible impacts of the required activity to construct and operate the mine. These studies will be submitted to regulatory agencies in the permitting process. Data from these studies will be used in the design process to ensure that the mine meets and exceeds environmental standards, in addition to the protection of the natural and subsistence resources in the YK region. The data will also provide information about the environment before, during, and after mine operations to ensure that the land is continually protected.
The YK region has a rich supply of fresh surface water, with 15 to 30 inches of annual precipitation, and 40 to 90 inches of annual snowfall. Donlin is committed to protecting surface and groundwater sources from pollution. Surface water quality monitoring and groundwater quality monitoring are being conducted as part of the baseline studies for the Donlin Gold project.
In order to ensure local water supply is not compromised, any water that comes in contact with the mine, such as rainwater or snowmelt would be diverted into a contact water pond. This pond would be used to supply water for a mill. A fresh water reservoir could also provide an additional supply of water for processing, as well as other emergencies and unexpected situations like fires. Before any water is discharged into the environment it will be treated to meet water quality standards.
Donlin Gold is also looking at different methods of recycling water to help reduce water use.
Aquatic biologists have conducted aerial salmon count surveys during the chinook, chum and coho runs on Crooked Creek and its tributaries since 2004. In order to get more reliable counts, a fish weir was installed in 2008. The resistance board fish weir includes a digital video recorder (DVR) to accurately record and count the fish. This video counting method means there is no live trap collection of the fish; they simply pass through the guidance structure and continue upstream.
Resistance board weir and DVR technology has been proven by both the Alaska Department of Fish and Game and the U.S. Fish and Wildlife Service to be effective in streams that experience turbidity issues similar to those of Crooked Creek.
The rock at Donlin Gold has naturally occurring mercury, as do many areas of the world associated with volcanic activity, high heat flows and plate tectonic boundaries. This mercury is released into the atmosphere through natural processes such as weathering of rock, vaporization from soil, wildfires and off-gassing of the world’s oceans. According to the U.S. Environmental Protection Agency (EPA) and other scientific sources, about one-half of the mercury emitted into the air each year is from these natural processes. The primary source of human-generated mercury air emissions is combustion of coal, whereas mining is a relatively minor source of mercury air emissions both nationally and globally. Once released into the atmosphere, mercury may be transported great distances from its original source. For example, according to the EPA, half of the human-generated mercury that is deposited in the western U.S. comes from industrial sources in Asia.
This year, the EPA finalized new national emissions standards for mercury based on maximum achievable control technology (MACT). These new limits are based on the nation’s best-performing gold processing facilities, which are well controlled for mercury. Donlin Gold supports the adoption of these strict regulations and will be implementing methods to meet or exceed these standards. Donlin Gold is committed to installing and operating state-of-the-art mercury emissions controls.
Gold cyanidation, a process where gold is temporarily converted into a water soluble, is the most widely accepted method for efficient and environmentally sound gold extraction. Donlin Gold plans to use this widely accepted practice to extract the gold from the ore, and will follow guidelines provided by the International Cyanide Management Code on how to handle cyanide from its manufacturer, to its transport, storage, use, and disposal. Dry sodium-cyanide briquettes will be shipped to the mine site in sealed steel ISO (International Standard Organization) tanks. The cyanide will be dissolved into a weak, pH-controlled solution for use in gold extraction. After the ore is crushed into smaller sized grains, it will be transported to an on-site leaching plant where the ore will be mixed with cyanide. The cyanide will dissolve the gold into a solution, and then the gold will be precipitated out of the solution. The cyanide solution will go through a destruction process that reduces its concentration. This industry leading detoxification process is being adopted by most of the major gold mining companies world-wide. The trace amounts of cyanide remaining in the tailings storage facility will disintegrate further under the influence of sunlight and air.
Tailings
After extracting the gold, wet tailings resembling silt will be a byproduct of the milling process. A containment dam, engineered to withstand the environmental fluctuations in Alaska, will be built to house the tailings. It will have a synthetic liner similar to those used in city landfills. Donlin Gold will be the first gold mine in Alaska to use this industry recommended liner for tailings storage. The ultimate size of the tailings storage facility will be approximately 1.75 miles long by one mile wide. When the mine is no longer in operation the tailings storage facility will be covered with rock, gravel, and soil.
Operating and powering the mine will require fuel and other supplies to be transported to the site. One way some of these materials will be transported to the project is by barges that will travel up the Kuskokwim River during the shipping season between June and October. However, with the introduction of the proposed natural gas line to supply the required power to the project, barge traffic will be greatly reduced. It is estimated one fuel barge and one supply barge will leave the port each day.
The Donlin Gold project will have an emergency Spill Response Plan ready to implement. The plan will include staged response equipment and trained response crews.
