Starting Koala North — North America’s first underground diamond mine
Following initial discovery in 1991, BHP Diamonds Inc. (now part of BHP Billiton) opened Canada’s first diamond mine, the EKATI Diamond Mine, in the Northwest Territories, on October 14, 1998. Four short years later, on November 29, 2002, saw the opening of North America’s first underground diamond mine—the Koala North mine. Nestled between the original Panda open pit and the new Koala pit, which is now in production, Koala North represents the first underground kimberlite mining venture in Arctic conditions outside the new underground mines being developed by ALROSA in the Yakutsk region of eastern Russia.Underground mining represents a key component of the long-term business plan for EKATI. As various open pits reach their economic limit, continued recovery of high-value ore at depth is dependent upon the ability to safely and productively mine the kimberlite pipes by underground methods. As a function of its location, size, and value, the Koala North pipe was ideally positioned to host the first underground mine at EKATI. In addition to being a production source for the operation, Koala North is designed as a learning mine, from which to gain valuable experience in preparation for the potential mining of other larger, higher value pipes by underground methods in the future. The Koala North mine, as described, has been designed and positioned to satisfy the access requirements for the potential future and larger adjacent underground mines at Panda and Koala.Applying the open benching mining method in Arctic conditions brings a unique combination of mining challenges together in a harsh climate and remote environment. For example, how can one support poor-quality kimberlites and deliver and apply good quality shotcrete for ground control in extreme cold? How does one ventilate, dewater, and operate an underground mine in 300 m of permafrost, with mine workings that are open to the environment? To facilitate this period of developing specific local experience and trialing different equipment and processes, the decision was made to establish the mine using contractors, who brought underground northern Arctic mining experience to the project. This enabled EKATI to defer the selection of the future long-term equipment fleet until performance and suitability knowledge was gained as well as the skill set needed for safe and efficient operation.This paper examines the design and establishment of the Koala North mine. Discussion includes experiences gained from site establishment, the first year of development, and production start-up with a description of how each of the mining challenges was addressed in our situation.Since original presentation of this paper at the CIM Conference and Exhibition in 2003, much progress has been made with underground operations at EKATI. The Koala North mine was completed and built up to a full production rate of 1,500 t/day. The subsequent Panda Underground feasibility studies have been completed to BHP Billiton’s rigorous toll-gating process and capital investment standards, and the mine was approved for development in April 2004. The Panda Underground is a US$146 million (BHP Billiton 80% share) project to deliver a 2,600t/day sub-level retreat mine with supporting infrastructure expected to deliver 4.7 million carats of high-quality Panda diamonds to the process plant over a six-year period. As of March 2005, the project is 70% complete and scheduled to reach full production by the second quarter of 2006. The Koala Underground project is currently undergoing a full feasibility study, including an underground access development program to facilitate kimberlite bulk sampling, hydrogeology, and diamond drilling programs in support of project evaluation.