My turn: Kensington Mine will produce toxic tailings

Posted: Friday, December 02, 2005

The Empire recently published a My Turn article on the Kensington Mine that attempted to address the issue of the toxicity of the mine tailings that would be placed in Lower Slate Lake. That author was concerned by the "debate over semantics" about whether the tailings are actually chemically treated, or whether chemical treatment occurs only to the ore and not the tailings.

Both ore and tailings are exposed to the same process chemicals and undergo chemical alteration during this processing. The chemicals used to remove gold minerals from the ore body also remove other metals, such as lead and mercury. While most of the chemicals used during the process will be shipped offsite along with the gold ore concentrate, some of these chemicals will remain in the tailings, along with a portion of the metals that were once held within the ore body. These chemicals and metals make the tailings discharge from the mill process into Lower Slate Lake a toxic discharge. Based on the Tailings Decant chemistry and toxicity testing information provided by the federal agencies in the supplemental environmental impact statement, the tailings discharge would be classified as a toxic discharge. The tailings discharge from the mill is a slurry of half liquid and half solids, and it will be extremely alkaline, approximately equal to that of ammonia. Coeur intends to discharge 210,000 gallons per day of this tailings slurry into Lower Slate Lake. Undiluted, the tailings discharge would likely kill all, or nearly all, fish and other aquatic life in the lake.

The issue addressed by the testing on aquatic life is not whether the tailings are toxic when discharged into Lower Slate Lake, but whether after mill operations cease and the tailings discharges have settled and been diluted by the lake water, the lake will again support aquatic life. These are two separate questions. It is clear that the tailings discharge is toxic. There is a dispute as to whether the lake will eventually become nontoxic.

In the end, the real issue here is whether it is appropriate to use our lakes and streams for the disposal of mining waste. Since the passage of the Clean Water Act in 1972, it has been the position of the federal government, including the Army Corps of Engineers, that mining waste is not an appropriate candidate for fill material in lakes and streams. In 2004, the Army Corps reversed course, now claiming that it can issue a permit allowing a mine to dump its waste into any river, lake, or stream that it deems appropriate. This is both a huge expansion of the Corps' authority, and it raises a significant concern about whether the Corps can carry out the responsibility to protect public waters from long-term contamination and damage. We now have engineers, instead of biologists, responsible for protecting the aquatic values of our streams and lakes from a potentially significant source of mining impact.

The Corps' recent change to allow the disposal of mine tailings into a lake was clearly not done to fix a problem that was preventing mines from being permitted. Hundreds of mines have been successfully permitted since the Clean Water Act was passed, including large gold mines in Alaska. In fact, I know of no mine in the United States that failed to open because the federal government prohibited it from dumping its waste into a lake or river. Other viable waste disposal alternatives have always been available. The Corps' reversal of its long-standing policy was thus completely unnecessary. It creates substantial risks to communities in Alaska and throughout the United States for no reason except to increase the profits of mining companies. This is an industry that is hardly in need of such governmental handouts.

• David M. Chambers is a resident of Bozeman, Mont. He is a geophysicist with the Center for Science in Public Participation, providing technical advice to public interest groups and tribal governments on the environmental impacts of mining.



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