After a massive landslide at the Eagle mine in central Yukon spilled four million tonnes of ore last month, concerns have arisen regarding the heap leach extraction method employed by the mining company.
Understanding Heap Leaching
Heap leaching is a common method used to extract gold from ore by selectively dissolving it, leaving behind the rest of the material. According to mineral engineering professor Jean-François Boulanger, this method is widely utilized in gold mines globally. The Eagle mine utilizes the heap leach method, which is different from the tank leaching method, predominantly used in Canada.
Heap Leaching Analogy
To illustrate heap leaching, engineering professor Claude Bazin analogizes it to a chocolate chip cookie, with the ore as the cookie dough and the gold as the chocolate chips. While not extensively used in Canada, this method is employed in countries like the U.S. and Chile, often in arid landscapes like deserts.
Tank leaching, on the other hand, involves extracting gold in enclosed spaces and necessitates additional processing, such as crushing the ore finely. Both methods employ a cyanide-sodium solution to transition the ore from solid to liquid form, with cyanide selectively targeting gold.
According to Victoria Gold’s technical report, the gold extraction process includes passing the solution through an absorption-desorption-recovery plant and a carbon absorption circuit.
Following the landslide, mining operations at Eagle have been paused, with water recirculation ongoing to manage contaminated water as storage is expanded.
Environmental Concerns and Water Management
An inspector appointed by the government of Yukon, Sevn Bohnet, raised concerns about water management at the Eagle mine, highlighting potential violations of the Yukon Water Act. The mine was required to have the capacity to contain 50,000 cubic meters of contaminated water, equivalent to 20 Olympic pools, but issues were identified with the containment pond not meeting standards.
To address contaminated water, Victoria Gold must submit a plan for treatment, with the government demanding details by a specified deadline. Professor Bazin discussed the breakdown of cyanide using oxidants like hydrogen peroxide to neutralize it effectively.
Victoria Gold’s next steps in treating contaminated water are crucial to safeguard groundwater, necessitating the installation of vertical wells as per the Energy and Mines department’s requirements.
