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Fort Knox tailings dam

‘Polluted water spilled at Fort Knox Gold Mine’

Associated Press – May 7, 2010 12:54 PM ET

ANCHORAGE, Alaska (AP) – A 2-acre area at the Fort Knox Gold Mine near Fairbanks is being dug up to remove pollution from a spill of water contaminated with a low concentration of cyanide.

The Department of Environmental Conservation told KTUU that most of the 300,000-gallon spill Wednesday was contained within a building. But, about 35,000 gallons flowed onto a gravel road and parking lot within the site.

The ‘what ifs’ of a similar spill occuring if Pebble Mine is approved would be catastrophic. Even tiny amounts of cyanide leaking into the saturated ground of Pebble would eventually find its way to the headwaters of fertile salmon spawning waters.

Keep in mind, Pebble will mine for gold as well as copper and molybdenum. One of the processes that will most likely be used to extract the ore from fine-ore bearing rocks will be to use xanthate floatation. This method of hard rock mining produces metal concentrates and billions of tons of waste rock based on Pebble’s projected size estimate. The waste rock has a label called PAG or potentially acid generating material. The PAG has the guaranteed effect of generating acid sulfides (i.e., sulfuric acid) when exposed to oxygen.

The processing chemicals of xanthates and *cyanide (*if cyanide extraction is used for removing gold from ore bearing rock as in Fort Knox’s processing method) and other metallic acid sulfide will be present in the billions of tons of tailings waste and would need to be ‘contained’ behind huge man-made earthen dams. The dams will need to be maintained from failure and the waste rock will need to be immersed under water forever. If the waste rock is exposed to air, the abundant oxygen levels will speed up the acidification process.

All of the above information about waste-rock tailings is just one potential scenario the Pebble Partnership may employ. Most of the higher quality ore-bearing rock is located deep within in an area labeled Pebble East. The most likely method for ore extraction in deep underground mines are by way of block caving. In this type of mining, ore-bearing rock is removed via an underground caving method on an industrial scale. In block caving, the method after ore-bearing rock is extracted is to induce collapse. The after-effect of the collapsing ground from above is an inevitable entry of water and oxygen which then is exposed to the waste rock thereby leading to acid sulfide decomposition on a grand scale. What results are high levels of acid sulfide deep underground with the high probability of mixing with and contaminating groundwater.

We cannot put our faith in foreign-owned corporations to protect our entire Bristol Bay region. One look at the BP oil rig explosion and subsequent ongoing massive oil spill is a testament to how even an established foreign-owned corporation doing business in North America is prone to a major failure of epic proportions.

There is no reason to justify cataclysmic risk for such an isolated, momentary reward.

 

FORT KNOX vs PEBBLE MINE 1

TARGET METALS

FORT KNOX – Gold Mine

PEBBLE MINE – Copper Mine w/ Gold and Molybdenum

 

PRODUCTION RATE

FORT KNOX – 36,000 – 50,000 tons/day

PEBBLE MINE – 100,000 – 200,000 tons/day

 

TAILINGS

FORT KNOX  – 200 million tons

PEBBLE MINE – 2.5 billion tons

 

WATER USAGE

FORT KNOX  – 4.9 cfs2

PEBBLE MINE – 114 cfs3

 

PROCESSING

FORT KNOX  – Cyanide Vat Leach

PEBBLE MINE – Xanthate Floatation

 

POTENTIALLY ACID GENERATING WASTE

FORT KNOX  – No

PEBBLE MINE – Yes

1This Fact Sheet was prepared by David Chambers, Center for Science in Public Participation, Feb 2007. It reflects information published by Kinross Gold (Fort Knox) and Northern Dynasty Mines (Pebble) from 2004 -2006.

Other articles:

‘Waste Disposal at the Pebble Mine’

http://www.ourbristolbay.com/waste-disposal.html

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