Fort Knox Mine
The Fort Knox Mine consists of two open-pit gold mines (Fort Knox and True North) and mill facilities. It is located about 25 miles northeast of Fairbanks. Learn more about the mine and NAEC's involvement in on-going operations.
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Overview
The Fort Knox mine complex currently consists of two open-pit gold mines (Fort Knox and True North), and the Fort Knox mill, where gold is recovered through the cyanide vat leach process and cyanide heap leaching. Fort Knox began operations in 1996 as a stand-alone mine. It was converted to a regional gold processing facility with the permitting and development of the True North satellite open-pit mine in 2001. The mine is operated by Fairbanks Gold Mining, Inc. (FGMI), a wholly owned subsidiary of Kinross Gold Corporation. A Canadian gold company, Kinross is currently the world's seventh largest primary gold producer.
Location
The Fort Knox mine is located approximately 25 miles northeast of Fairbanks and two miles from the community of Cleary Summit (click here for map), which consists of an aurora-viewing business and bunkhouse and several year around residences. The satellite True North mine is situated on the western side of Pedro Dome, 11 miles northwest of Fort Knox. A dedicated ore haul road connects the two properties.
Type of Ore and Current Production
Fort Knox
The Fort Knox deposit is a low-grade gold deposit hosted in and along the margins of quartz veins, shears, fractures, and pegmatites within a granite intrusion. Gold is associated with anomalously high bismuth and it is a low-sulfide deposit. In 2009, FGMI mined 11.96 million tons of mill grade ore, 4.11 million tons of transition grade ore, and 12.70 million tons of leach grade ore, producing 263,260 gold equivalent ounces . Average grade of ore is 0.024 ounces/ton. As of December 31, 2002, the current proven and probable reserve (based on a gold price of $300/ounce) was 2.4 million ounces of gold contained in 100 million tons of ore.
Initially, Fort Knox was given a life estimate of eight years. In February 2008 the mine’s operator began the construction of the Walter Creek heap leach facility to process large volumes of low grade ore and mineralized waste material. Construction of the heap-leach facility was completed in 2010, extending the life of the mine to 2018 and increasing Fort Knox’s production to an average 370,000 gold ounces per year for five years.
True North
At the end of 2004, mining the True North Mine was terminated and in 2009, the mine’s operator decided to permanently cease operations at the site. In the summer of 2009, FGMI began final reclamation of the site.
Operation
The Fort Knox pit covers approximately 332 acres, and is roughly a half a mile wide by a mile long. Mining occurs below the water table, thus there are dewatering pumps that keep the pit dry during mining. At True North, mining was done only above the water table, in an oxidized ore zone. Mining techniques used include standard drilling and blasting. In 2009, Fort Knox produced 20.03 million tons of waste rock, which is stored in massive rock dumps on each property.
The Fort Knox mill uses cyanide to recover gold from the ore, processing between 36,000 and 50,000 tons of ore a day; in 2009, it processed 14.14 million tons of ore. First, the ore is crushed into a fine powder, then, after thickening, it flows into leach tanks, where cyanide dissolves the gold. Next, activated carbon is used in the Carbon-in-Pulp (CIP) circuit to absorb the gold from the cyanide solution. Screening removes the gold-laden carbon from the slurry. The pregnant carbon particles are put through the gold recovery circuit and recovered gold is melted into dore bars and shipped to an off-site refinery for final processing. The slurry is piped to the tailings impoundment. The Walter Creek heap leach facility began production in 2009; a cyanide solution is sprayed over piles of low grade ore and allowed to leach through, dissolving the gold that is later recovered from the solution.
The 300-400 acre tailings storage pond, created by the construction of an earthen dam, is in the upper Fish Creek drainage. The dam, keyed into bedrock, is raised each year as more and more tailings are stored behind it. In its final configuration, it will require approximately 23 million cubic yards of fill, and measure 350 vertical feet from the toe of the dam. A series of pump-back wells installed below the dam keep tailings fluid from seeping into ground water. During mine life, Fish Creek is diverted around the impoundment.
Mine Reclamation
Fort Knox
In 2009, reclamation at Fort Knox focused on disturbed areas associated with the Tailings Storage Facility (TSF) seepage interceptor system and the lower seal pit.. Reclamation efforts included regrading, seeding, and fertilizing. FGMI is currently revising the reclamation plan for the Fort Knox Mine to reflect changes to the life of mine plan of operations including the expansion of the pit, raising the TSF dam, and the Walter Creek heap leach facility, and to address disturbances from the expansion of the mine pit and associated changes to waste rock dumps.
The current financial assurance for the mine and mill is a $39.6 million dollar letter of credit; an additional adjustment to the financial assurance for Fort Knox and True North is anticipated for 2010.
Given the proximity to Fairbanks and the impact on local rivers and watersheds, the NAEC monitors the mining and milling activities at Fort Knox, and submits comments on plan revisions or mine expansions to ensure protection of waters and habitats.
True North
Following the decision not to conduct additional mining at the True North mine, FGMI began final reclamation of the site in 2009. (Initial reclamation of True North began in 2005.). The True North reclamation performed in 2009 and the work planned for 2010 is focused on completing the major earthwork. In 2010, FGMI plans to complete all major reclamation activities of the site. After 2010, FGMI will monitor the success of the reclamation activities and address areas as needed. FGMI is in the process of revising and updating the True North reclamation plan.
Click here to download a factsheet about Fort Knox.
last modified Mar 26, 2010 05:14 PM
