Fort Knox Mine

Highlights:

Tailings Storage Facility Design and Construction
Cone Penetration Tests
Static and Dynamic (Earthquake) Analyses
Heap Leach Pad Design
Tender Documentation
Quality Assurance and Quality Control (QA/QC)

Client: Fairbanks Gold Mining Inc. (FGMI)

Location: Fairbanks, Alaska

Completion Date: ongoing

Project Description: The Fort Knox Mine is located near Fairbanks, Alaska. Knight Piésold has provided all engineering design, construction QC services and operational assistance to the tailings storage facility since the onset of initial planning in 1992. The facility is a valley type impoundment and is contained behind a large, cross valley, zoned earthfill/rockfill embankment dam that has been raised in stages using the downstream method. The dam was completed to its original configuration in 2006 to a height of 324 feet. Since then, FGMI identified additional ore reserves, which required a larger tailings capacity and further raises to the facility.

In addition to the tailings storage facility, Fort Knox Mine also has the Walter Creek Valley Heap Leach Pad. This heap leach pad is a 160 million tonne capacity facility to be constructed within the upper end of the Walter Creek drainage above the existing tailings storage facility. At full development, the maximum heap height from toe to crest will be approximately 800 feet and the maximum ore thickness in the pad will be about 500 feet.

Knight Piésold’s Role: The future raises of the tailings storage facility are proposed to follow a modified centerline approach. In support of this new plan, cone penetration tests (CPT) were completed in the tailings just upstream of the dam from a barge to define their strength, liquefaction and compressibility characteristics. Static and dynamic (earthquake) analyses were then completed to confirm that the raises would meet industry accepted standards for large dams. A base platform fill was constructed in 2009 over the tailings as the foundation for the raises.

For the Walter Creek Heap Leach Pad, Knight Piésold completed the design, prepared tender documentation, and provided quality assurance and quality control (QA/QC) during construction. Stage 1 of the construction began in 2007 with the project scheduled to be constructed in five stages.