While overburden represents the largest single stream of waste generated by most surface mining operations, it’s far from the only material that needs special handling on the site. It’s often confused with other mixed ground rock materials like interburden, tailings, and gangue. Yet these materials are all different and are rarely stored together or mixed until it is time to refill the mined area. Other types of by-products may need more processing or more careful containment than overburden to ensure there is no environmental damage or loss. Knowing when to keep materials separate and when to mix them for storage will help you plan out the space necessary for tailings, overburden, interburden, and more.
Overburden vs Interburden
These two materials are easy to confuse for each other since they share similar names. They’re also the materials most likely to be safe to store together and mix before their final use. Overburden refers solely to the material removed from above the first deposit or seam of valuable material. The term interburden is then applied to anything found below that deposit but above further deposits. Even if the two materials are different, such as ore above coal, the rock and sand between them will be referred to as the interburden. This material tends to have a much higher content of valuable oil, ore, or minerals. Thus, it generally is separated from overburden for further processing. Once it’s processed as much as possible, it’s usually added to the overburden pile for containment until reuse for reclamation or construction.
Tailings and Gangue
Tailings are the residues left behind after crushed ore materials are processed to separate the metals from the bulk rock. These materials are full of heavy metals and radioactive elements. Gangue is another term for this rock, but it’s also used to describe rock sorted out from the productive ore earlier in the process. Since tailings and gangue pose far higher environmental hazards than overburden materials, they require far more extensive containment. Secondary containment and leak detection are usually required for tailing ponds but not for overburden storage areas. Avoid mixing tailings and gangue with the less hazardous forms of mining waste until it’s time to remediate the mining area, unless the tailings are stabilized through advanced processing first.
Other By-Products of Mining
All of these rock-based sludges or dry mixtures are not the only types of waste that need storage and containment on the mining site. Even the topsoil above the overburden material can become a hazard if it’s piled and allowed to erode rather than stored with care. Without restoration of the original topsoil layer over the side, recovery at the end of the mine’s operation is far more costly and likely to fail. Overburden alone can’t completely refill and restore the natural habitat removed during mining. Oil sands in particular tend to feature a peat-rich bog material known as muskeg. If it’s not fertile enough to return to the area after mining, it’s often directed for reuse in agriculture or fuel production instead.
Careful separation of the various waste streams produced within a mining operation will ensure success during the remediation stage. Since almost every solid waste produced by the mine can go back in it at the end to refill it and restore the natural environment, these materials must be handled with care until that time. Choose durable liners from BTL Liners to make that containment as easy as possible.
