When I first heard about Pebble Mine, I thought it was a great idea. Development of stranded resources and jobs and economic development in rural areas is good for Alaska. But, the more I learn about the Pebble mine area, the more I am deeply troubled, and have increased doubts that it can be done in a manner that does not harm others.
Having been a professional miner for the past several years and being a scientist by nature, I have a greater understanding of what is involved in such a mining project than the typical theater student, lawyer, or ad agency.
My mining has been for placer gold, which has been naturally freed from the host rock over hundreds of millennia, and has been soaking is sea water for perhaps thousands of years. My “mining waste” is simply any rock that I move, not a very valid use of the term “waste” but that is what it is called.
The Pebble Project would most certainly be a hard rock mine. Such mines extract ore from rocks by crushing them and sometimes bathing the crushed rock in acid to dissolve the copper and gold, other times they simply remove the newly freed metals via a gravity separation process. Modern mines typically use both methods, gravity first, then acid. Now as scary as the term “acid” is to people, that is really not the danger of modern mines that are built to existing standards required by State and National law. It is my understanding that these acids are well contained, highly unstable, and photo-degrade.
The true risk with Pebble comes from the crushing process of the natural rocks. As the Bristol Bay region was formed, in relatively recent geologic time, natural processes have broken up the rocks and dissolved into aqueous solution the various natural minerals of these rocks. The rate of this natural leaching depends on the surface area of the rock and the rate of the flow of water around it. This is how we get hard water.
Mining in Pebble would most certainly increase the surface area of the rocks several thousand times, by making them into many very small rocks. The process would also “fluff the material making it easier for water to flow more easily through. The result would be a very dramatic increase in the levels of various minerals in the water, which could reach a level toxic to fish.
One way to deal with this issue is to sequester the crushed rock tailings in a place that has very limited hydrology, such as a plateau or a dammed area. Finding a stable area that does not have water running through it might be hard to do at Pebble. Building a large enough dam area that would be stable enough for long enough may also be problematic.
As a scientist, I cannot prejudge the project until I have their project plan to evaluate. A plan that I am very interested in seeing. I may be wrong, there may exist proven, reliable, technology that would allow Pebble to proceed without harm to others. But that is a very high burden of proof they would have to meet before I would support them.