Tailing storage at the Fort Knox Mine : an innovative expansion to continue a history of success

Abstract

Fairbanks Gold Mining, Inc. (FGMI) owns and operates the Fort Knox gold mine and mill, which has been in production since 1996. Tailing are stored behind a cross valley dam. In the summer of 2006, the tail ings storage facility (TSF) dam was raised to its origin ally designed final crest elevation. However, in J anuary 2009, the mill ore reserve was increased above the remain ing capacity of the TSF. A site wide optimization study identified a 52-foot raise to the TSF dam as the pr eferred alternative for expanded capacity, but this posed a challenge. How would the raise be configured to ma intain the necessary level of stability and securit y for the TSF given its hazard consequence classification and other site specific conditions without adopting a conventional downstream raise? The solution was to construct the 52-foot raise with partial placement of the upstream random fill shell over tailings in lieu of a downstream raise as had been the practice throug h 2006. The 52-foot raise then bears largely on engineered fill on the crest and upstream face of the existing dam with a modest construction onto the tailings deposited imm ediately to the upstream. This paper presents the design of the 52-foot raise to the Fort Knox TSF together wit h construction and operational experiences to date, which represents another chapter in the success of the fa cility.