ODDS ‘N’ SODS — Beneath the snows of BC

.BS.J. Hunter

Misfortune has befallen many mining ventures, among them the Granduc mine in British Columbia. In February 1965, a massive avalanche engulfed the Leduc campsite, forcing Granduc project managers Merv Upham and Nick Gritzuk to recast the entire program for the operation, which was owned by Newmont Mining.

The challenge facing these men was formidable. The entire focus of development was directed to driving 54,000 ft. of tunnel, as a single entry, from the eastern terminal at Tide Lake. A massive field of glaciers, including the Berendon, Frank Mackie and Leduc systems, blocked the route, reaching thicknesses of 2,400 ft.; there was no alternative but to go underground.

In light of rising copper markets and prices, time was of the essence in bringing the 7,500-ton-per-day mill into production. With delays having already heavily burdened the venture, a close eye was kept on the tunnel’s cost.

The two stalwart mine operators did not waste precious days in review. In short order, they formed a central engineering core and laid out a revised schedule and plan for the tunnel’s completion. Soon, follow-up surface surveys established the finite controls needed for the driving of the single entry.

The tunnel itself was to be 15 ft. wide by 15 ft. high, big enough to accommodate 50-ton ore cars. The track gauge for the 100-lb. rails was set at 42 inches and the gradient set at plus 0.25% to surmount the 140-ft. rise in elevation from the Tide Lake portal to the underground terminal in Granduc Mountain. Previous geological mapping over the surface of the route had already outlined types of rock and their competence, and possible water in-flows.

The critical factors in constructing the tunnel were ventilation, haulage and communication. The ventilation system was designed for a capacity of 15,000 cu. ft. per minute using a 36-inch rigid ventilation pipe. The electrical fans were to be installed at 9,000-ft. intervals in order to maintain adequate pressure at the advancing face. A trolley-phone system would be included with the locomotives, which would be battery-operated.

Three 23-man crews were formed and trained to drill, blast and muck on a 3.5-hour cycle. Also of importance was the assembly and maintenance of the equipment, including a jumbo drill, two mucking machines, seven Goodman trolley locomotives and numerous 10- to 20-ton Granby cars. However, the entire program hinged on the development of a 200-ton Jacobs sliding floor, or “flying carpet,” which would advance with the face to facilitate the switching and operation of equipment.

Upham and Gritzuk attended to these details, and excavation was soon under way. Development lasted from June 1965 to December 1968. Record performances were established: the best one-day advance was 115 ft. and the best advance in a single month was 2,320 ft.

The final cost of the project was $17 million, or about $317 for every foot of the 10.3-mile-long tunnel. According to Upham and Gritzuk, the successful completion of the project was attributable to the integrity, adaptability and efficiency of the Canadian miner.

The two keys to good performance during construction were the judgment of the man at the advancing face and teamwork. Workers overcame challenges such as poor rock conditions and heavy water inflows, both of which complicated the smooth, yet prolonged, construction phase. Nevertheless, the will and resilience of the crews helped them adjust to and surmount each and every difficult situation.

The product of all of this planning and hard work was the longest tunnel of its size and type in North America. The Granduc mine became a reality, and 26 million tons of copper ore was moved along a single track more than 54,518 ft. long.

— The author, a retired mining engineer, resides in Vancouver, B.C.