Tailings are a part of mining that get a lot of publicity, and managing them responsibly is a key environmental component of our business. In this post, we’ll help you understand what tailings are and how they’re managed.
What Are Tailings?
Tailings are a mixture of solid particles, mostly rock, and water that is left over after the gold extraction process. Tailings must be managed and disposed of safely, so that any impurities do not adversely affect the environment, local communities, or biodiversity in the area.
What Is a Tailings Storage Facility?
A tailings storage facility (TSF) is the name for a storage area for tailings. A TSF is often a tailings pond, where the tailings are stored in process water. Ponds are engineered using dams, which is why you’ll also often hear the term “tailings dam,” and the surrounding environment (for example, valleys). Tailings dams are similar to conventional water dams.
In some cases, like at our Efemçukuru operation (pictured above), tailings are filtered to remove water before they are stored. In this case, a dam isn’t required; the dry tailings are stacked in a way that is stable and matches the local landscape.
What Are the Environmental Risks of Tailings and How Are These Minimized?
Tailings present potential risks to the environment. Tailings solution is mostly water, but can include trace amounts of chemicals from the extraction process, such as acidity or alkalinity and additives.
Environmental risks are minimized in a number of ways. First, extensive studies are done to select TSF sites, which are located away from sensitive environmental areas such as lakes and streams, wetlands, and key biodiversity areas to the extent possible. Second, the extraction process is designed so that the resulting tailings are environmentally stable and contain as few impurities as possible. Third, TSFs are designed conservatively to provide a safe and permanent storage area that can withstand extreme weather events.
Mining companies are required to monitor TSFs on an ongoing basis.
How Are TSFs Regulated?
Regulation of TSFs depends on the operating jurisdiction, but is usually overseen by the country’s environmental government agency. Companies are required to determine the composition of tailings before a mine starts operation, as part of the Environmental Impact Assessment.
Who Conducts TSF Safety Inspections and What Do They Look At?
Safety inspections are completed by qualified engineers who are familiar with the tailings design and other site-specific requirements and conditions. Eldorado also requires our tailings dams to be audited by an independent consultant every three years.
Tailings dams all have an associated Operational, Maintenance and Surveillance Manual. The manual documents the responsibilities of anyone working with the facility, as well as safe procedures for monitoring, maintenance, and spill response. Monitoring procedures typically include visual inspections, comparing the current performance of the dam to the design, gauging the water level (if applicable), and doing environmental testing in the surrounding area.
What Happens to a Tailings Pond Once It’s Full?
Rehabilitation of tailings ponds is site specific. In general, water must be drained from the pond. Then the solids are compacted so the ground is strong enough to support weight. In some cases, the pond area is leveled or altered to match the surrounding landscape. Finally, the area is covered with topsoil and replanted. Monitoring programs for a period of time after closure are usually required by regulatory agencies as a component of the Environmental Impact Assessment process. These ensure the surrounding groundwater and soil are environmentally sound post-closure, or if not, material is collected and treated.
Next week we’ll dig a little deeper and tell you about how we specifically manage tailings at our Tanjianshan mine in China. Subscribe so you don’t miss it!
Find more information on how we approach environmental management.
Looking for more on sustainability at Eldorado? Check out our 2014 Sustainability Report.