Construction has been contracted out to pcl Industrial Constructors, which is carrying out the work in conjunction with pcl Constructors Northern (both part of the pcl Construction Group). The company has a crew of 280 people (soon to rise to 350) building a mine with a 10,000- tonne-per-day capacity and an annual production target of 200,000 oz of gold. That capacity is more than three times greater than that of either the Giant Yellowknife or the Nerco Con gold mine, near Yellowknife. The start-up cost for the project has been set at about $190 million, $20 million of which covers exploration and development, $155 million for estimated capital costs and $15 million representing pre-production and start-up capital.
During our visit, Colomac was a madhouse, but one carefully co-ordinated. “I’ve never seen an operation as smooth as this,” said Witte. “Pcl has done a fantastic job. We got in 1,153 loads by winter roads between January and mid-April; all of the material we couldn’t move by air (including the 32-tonne main shaft for the primary crusher and the equally heavy and massive sections of the primary mill bull gear). It was touch and go with the main shaft, but the manufacturers put a rush on the job and beat spring break-up by two weeks.”
Some of the machinery for the project was purchased used and completely refurbished because fabricating new components would have been too time-consuming. “Everything we need is on site now, including 12 million litres of fuel,” Witte said. “Our airstrip can handle a 4-engined Hercules, and we can fly in the few bulky items we didn’t have time to ship by truck.”
The speed with which structures are rising is impressive, the result of pcl’s careful pre-plannng. Before the first truckload roared on to the laydown area, a grid system had been established for stockpiling, served by a network of “streets” which separated materials into 14 main categories and numerous sub-categories. As a result, workers could easily locate equipment. That sort of planning made it possible for powerhouse steel to be almost completely erected in two days. (Colomac will have five generators on stream at any given time, with a sixth on standby and a seventh on maintenance, which can produce 14 mw of power in total. To put that in perspective, consider that the city of Yellowknife alone, with a population of about 12,000, has a power plant that produces 12.5 MW.)
Almost everything is oversized at Colomac. Concrete and activated carbon were delivered in 1-tonne supersacks. The all-weather batching plant can produce 300 cu yd of concrete per day. Robinson’s Trucking of Yellowknife, which built the 220-km-long winter road from Rae-Edzo, carried loads which averaged 30 tonnes.
“We had three sets of priorities,” Witte said. “The first was machinery, equipment and supplies we had to have, and could only get in by road. The second was material we could fly in if we had to, but which would be enormously expensive to ship by air, and the third was everything else.” Adds PCL’s site superintendent Robert Fouty: “It worked just fine except that, at the last minute, we suddenly realized we had hardly any gasoline on site. Diesel fuel had top priority, but we had completely forgotten the pickups, snowmobiles and all-terrain vehicles we were using. But we got that in too.”
Once PCL’s work is done, Neptune plans to buy much of its construction equipment. The equipment includes Caterpillar 992, 13-cu-yd front-end loaders and Caterpillar 777 85-tonne trucks. The PCL construction camp will be converted to mine housing. Neptune also has been fortunate in terms of enviro nmental considerations. Three nearby lakes with negligible fish populations, served by a 6.3-km pipeline, provide an ample tailings area. Metallurgically, the ore is clean, with little in the way of base or heavy metals. “There’s really nothing to interfere with cyanidation and we expect to be able to recycle most of our water from the tailings,” Witte said. Free gold has been found in the deposit and, during the development program, the entire core has been assayed.
For every ton of ore, 3.2 tonnes of waste will be mined. With that level of stripping, vat leaching was first explored because the vats could be constructed from the waste rock. But conventional mill leaching has proved cheaper in tests.
Stripping was scheduled to begin in August. Pre-production plans call for stripping and stockpiling 250,000 tons of start-up mill ore. The official production date is March 1, 1990. By then the 9-inch, down-the-hole Ingersoll-Rand rotary drills will have been broken in. The drill pattern has yet to be selected, but the mine plan calls for 25-ft benches and 60 degrees slopes.
About 40% of the surface plant is up. The Allis-Chalmers primary gyratory crusher is in place, as are the Nordberg 7-ft shorthead cone crushers. The mill will have 12 leach tanks and five carbon-in-pulp tanks. The grinding mills have been erected as well.
For number-crunchers, here is the Colomac low-down: Production costs are now being re-examined, but John Rogers, Neptune’s vice-president operations, expects Colomac’s gold will cost $275 (Canadian) per oz to produce. Mining will cost $6.79 per ton; milling, $7.17 per ton; and general and administrative charges, $2.29. Mill recovery rates should run between 93% and 95%. The current published reserve is 28 million tons grading an average 0.056 oz gold per ton. (In the first four years, the millhead grade will average 0.064 oz per ton.) Erik Watt is a freelance writer based in Yellowknife, N.W.T.
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