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Safe disposal of mine waste, including tailings, is gener- ally recognized as the single largest environmental chal- lenge facing the mining industry worldwide and a major expense for mining companies.
Modern open-pit mining has a very high waste-to-prod- uct ratio (roughly 99 tones of waste to each tone of copper, and even far more waste in gold mining), making waste the major product of mining. The Canadian mineral industry generates about 650 million tonnes of waste per year.1 The storage of this waste poses signifi- cant engineering challenges. All over the world, tailings- dams are leaking, or breaking, and seeping toxins on a daily basis; but recent environmental and social disasters in Romania, Guyana, Spain, and the Philippines—caused by tailings-dams that burst—have served to focus public attention on this problem.
Mine waste poses an environmental threat not only through its volume but also because of its toxicity. Mine tailings commonly contain sulfides as well as metals— such as cadmium, copper, iron, lead, manganese, mercury, silver, and zinc—that occur naturally in the ore body. When sulfides in the tailings are exposed to air they oxi- dize. If oxidized tailings come into contact with water, environmentally toxic sulfuric acid is produced. This process is known as Acid Mine Drainage (AMD). The sulfuric acid also accelerates metal leaching in tailings. Acid Mine Drainage can have a toxic impact on ground and surface water around mines. According to the United States Environmental Protection Agency, water contami- nation from mining poses one of the top three ecological- security threats in the world.
Why Do Mining Companies Want to Use Submarine Tailings Disposal?
Submarine Tailings Disposal is dumping mine tailings into the sea through a submerged pipe. In the Western
￼￼Pacific region, mining compa- nies argue that Submarine Tailings Disposal (STD) 2 is the best solution for tailings disposal. They say that storing tailings on the land in this region is risky—because the Western Pacific experiences earthquakes; has many moun- tainous islands with no place for on-land storage; is an area where land is urgently needed for agriculture; and has high rainfall, making tailings dams vulnerable to collapse. In modern STD systems, mining companies claim that the goal is to deposit tailings into deep waters of the sea where there is little oxygen. They say that therefore tailings will be less likely to oxidize and leach out toxic metals. Mining companies also argue that marine life at these depths is not so abundant and it is not important to the human food chain.
By pumping their tailings into the sea, mining companies remove unsightly tailings on land. They “solve” the prob- lems of maintaining tailings impoundments and dams, and managing acid mine drainage and metal leaching from tailings impoundments, sometimes “in perpetuity” (forever). And in case of a dam failure, mining companies avoid the risks of social rage and of expensive clean up. Unlike on land, if something goes wrong with an STD system, there is little the company, or anyone else, can do. The public may not even discover a problem, because it is out of sight under the sea. Even if a problem becomes known, it is harder to hold a company legally and finan- cially responsible.
STD is also a relatively cheap mine-waste solution. Placer Dome’s Dick Zandee wrote in a 1985 article about their surface disposal system into Calancan Bay in the Philippines that, “operation of the current sea-disposal system costs less than half as much as the operation of the tailings-pond system.”3 For the Kitsault mine in Canada, which was given a special site-specific exemption in 1979 to operate an STD system, it was estimated that STD would save the company $25 million dollars per year in ￼tailings disposal costs relative to the cost of land-disposal. The U.S. Department of the Interior concluded that, on average, STD use resulted in a 17% reduction in capital costs and a 1.6% increase in operating costs…