Mining is a relatively minor source of mercury air emissions both nationally and globally.
Most of the rock in the area surrounding the Donlin Gold project has naturally occurring mercury, which is typical of an area 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 the combustion of coal. 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.
In 2010, the EPA finalized 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. To adhere to these new EPA regulations, Donlin Gold is committed to installing and operating state-of-the-art mercury-emissions controls to meet or exceed these standards.