While there are many other materials that can risk human health or cause environmental damage, tailings are among the most challenging to contain. Tailings are the by-products of mining.
Keeping them stored is difficult enough, but containing all of the runoff, leachate, and other liquids is a whole challenge unto itself. Certain innate characteristics of the tailing material makes it more challenging to store than less harsh mining by-products like overburden. Since the environmental risk of this material does not fade with time as it does with other materials, the final containment for a facility must be perpetual and permanent. Addressing the specific risks of tailings, when designing containment for them, is key to long-lasting storage and low risk of damage.
Volume of Production
In the earliest days of modern mining, tailings production was mild to moderate. Only the most valuable and concentrated deposits were considered worth the effort to extract, so tailings could be less than 50% by volume of the raw ore removed from the mine. Advancements in ore processing now make far less concentrated ores worth extracting. Today, the sheer volume of tailings produced by mining operations of any kind is the single greatest challenge to storing and containing it alike.
Depending on the particular ore or mineral being processed, up to 80% or more of the raw material removed can end up as relatively useless tailings. With only 10% to 20% of the raw ore removed from a mine consisting of valuable metals or minerals, that means that hundreds of tons of tailings are left from even the smallest operations. Without the generation of large piles of tailings with relatively little value, it’s practically impossible to collect the necessary amounts of metals, minerals, and more. Combine tailings with the volume of overburden, the material removed above any useful ore or deposits, and you are dealing with piles that can reach over 200 feet tall or ponds that must contain millions of gallons.
Cost
Unfortunately, containment is often tied to the value or potential profit of a material. While it obviously makes sense to limit losses of valuable ore or uranium since it directly impacts profit, relatively useless tailings also need costly containment. Yet, they rarely produce much value of their own. This means that the cost of their containment must be considered before factoring out the profitability of the extracted material. If the mine will only be profitable if corners are cut on storage measures for leftovers like tailings, it’s not a truly profitable venture. The profit generated by the most valuable extracted materials must be great enough to easily cover the advanced, permanent containment needed for the by-products.
Radioactivity
Some materials generated by mining, most specifically from uranium processing, are highly radioactive. Uranium tailings can retain up to 85% of the total radioactivity of the original ore, making it a particularly hazardous material to handle and store. Even if the material is removed, leftover radiation continues to be a risk to humans and animals alike until it has a chance to fade. Some tailings need more secure and longer-lasting containment measures than others, just due to the additional risk of both health and environmental impacts if there is a release. Aside from the direct risk of radioactivity, piles of uranium tailings produce a large amount of radon. This radioactive gas can travel far from the facility and affect nearby homes or businesses unless it’s properly contained for the life of the tailings.
Abrasive Materials
Tailings consists of a wide range of different physical materials. The same pile of material left from a single mine may contain large chunks of rock nearly as big as a baseball, smaller pieces that form uneven gravel, and many fine pieces of sand or smaller particles. All of these sizes of material are likely to be somewhat abrasive due to the types of blasting, excavating, and processing techniques used for extraction. Both the mixed nature and abrasiveness of the tailings makes the material hard to store. It’s hard on liners, prone to shifting due to destabilization, and wears out the equipment used to transfer it. Only the toughest reinforced geomembranes can handle even indirect exposure to this kind of abrasive material.
Sludge and Liquids
Not all tailings are kept dry during the processing stages. Many ores require strong acidic treatments to come loose from the tailings, leaving behind a sludge that is mixed with potentially hazardous liquids. Completely liquid runoff from the ore processing pile is technically known as raffinate, but it’s commonly mixed with solid tailings into a hard-to-handle sludge. It’s heavy, difficult to contain, and prone to seepage even with the best liners. Yet, purposefully keeping tailings in sludge form can also help solve containment issues that might be caused by trying to separate the liquids out from it. Each material must be investigated, and a storage method chosen, based on its unique composition and the challenges relevant to the containment area.
Of course, none of these challenges are insurmountable. Tailings simply require a more durable liner than other types of mining waste. BTL Liners has the reinforced polyethylene liners to secure the toughest tailings piles and ponds alike, as well as cover material to prevent wind scouring and erosion.
