The Billion Dollar Triangle FROM VAL D’OR TO TIMMINS BOUSQUET NO. 2

“We have to drift to the boundary (with the Dumagami mine to the east) on the fifth level,” Brousseau said as he showed us around the mine. “Then, it’s home-free from there. All our development work will then be in ore and will pay for itself.”

The deposit, which is the down- plunge extension of the Dumagami orebody, contains at least seven million tonnes of mineable ore grading 6.4 g gold per tonne (0.186 oz gold per ton) on average. That does not include a low-grade disseminated portion near surface containing about two million tonnes. But it does include a wider, higher-grade zone to the eighth level sandwiched between volcanic rocks in the hangingwall and sediments in the footwall. The gold-bearing structure continues at depth, but reserves there (five to six million tonnes at last count) are still in the uncertain “possible” category.

In 1987, cash-rich LAC Minerals decided to spend $85 million to build a mine to extract that mineable reserve. The decision was based, in part, on the possibility of losing significant gold production from a Supreme Court of Canada decision to hand over to Corona Corp. the Williams mine in Hemlo, Ont. Now that that decision has come down, ending an 8-year court battle, developing Bousquet No. 2 appears to be a wise move for a company trying to save face. Once completed in 1993, the mine should be capable of supplying a mill treating 2,500 tonnes of ore per day. No mill has been designed yet, but Brousseau has the mill site and the tailings areas picked out.

“We’re being conservative on the milling side of things,” Brousseau says. “First we’ll invest in expanded capacity at our mill in Malartic (which treats some ore from Bousquet No. 1 and Doyon) and once we know what the metallurgical characteristics of the ore are, we may decide to invest in a new mill here (at the Bousquet No. 2 mine site).” At 2,500 tonnes per day, the mine should result in gold production of 150,000 oz (4.7 million g) per year.

The mill was designed so that production can be increased to 3,000 tonnes per day. The mine will require somewhere between 195 and 200 people to operate. Those people are being hired by LAC this fall and will be on the mine site in January, 1990.

By then, Dynatec’s development crews will have prepared the first mining block between the fifth and sixth levels up against the common boundary with the Dumagami mine. A joint LAC/Dumagami mining committee is studying ways to establish common blasting parameters, backfill characteristics, mining sequences and ground control measures for the efficient extraction of the boundary ore. Since the vertical projection of the surface property boundary makes a skewed line where it intersects the dipping, plunging orebody, Dumagami will be mining some of LAC’s ore from the seventh level down and LAC will be mining some of Dumagami’s ore above the fifth level.

On the Bousquet side, a ramp is being driven between the fifth and sixth levels from both ends — up from the sixth and down from the fifth. This will provide access to sublevels which will be spaced 60 m apart. Dynatec also has a Robbins raise boring machine in operation, reaming a 12.5-ft-diameter (3.75-m) ventilation raise. We saw the unit in operation, reaming the second 1,620-ft (486-m) leg of a ventilation raise from the fifth level to the first level. To ensure that dust levels are kept to a minimum, Dynatec keeps the bottom of the raise choked with cuttings and hangs a burlap curtain over the opening on to the level to capture any airborne dust. The burlap is kept well- wetted.

The ore will be mined by three methods at Bousquet No. 2, using the technical know-how developed at the near-by Bousquet No. 1. Based on his experience at No. 1, Brousseau expects mine productivity at No. 2 to be in the 54-tonnes-per-manshift range. The avoca method will be used in the upper, disseminated zone; longitudinal longhole open-stoping in the higher-grade zone where the ore width is fewer than 3 m; and primary and secondary longhole open stoping with cemented rock fill where ore widths exceed 3 m. Experience gained from mining the No. 1 mine will prove valuable in operating the No. 2 mine. “We’re doing everything the right way from the beginning,” Brousseau says. “That means good planning and using the best equipment available.” This is Brousseau’s fourth major underground engineering project, so he knows what to avoid.

LAC has decided to use all new electric-hydraulic equipment. Tamrock Data Solo top hammer longhole machines equipped with 4 1/2-inch tube rods will be used for the main production drilling. Similar machines have achieved 125 m of drilling per shift at the Williams mine in Hemlo, a productivity rate that is hard to overlook, Brousseau said. Electric scoops will be used for haulage to the ore passes on the levels and specially- designed 26-ton Wagner trucks will be used for the rock fill. “Wagner was the only manufacturer willing to custom-build the trucks for us,” Brousseau said. By the time mining begins, most of the equipment will be underground and ready to go.

There are several indications that LAC has designed this mine for a long life. First, the company is accumulating data on rock mechanics from Day One. This involves measuring diamond-drilled core to determine the competence of the rock (referred to as a rock quality designation) and mapping the complex structure in all openings. This data will help LAC’s rock mechanics engineer understand the complex system of jointing in the mine. That information will be used to orient mine openings so as to take advantage of the in situ stress field without escalating ground control costs. More important, it indicates that mining will likely continue well below the ninth level.

Another long-term strategy is reflected in the design of the shaft. Two 12-ton skips and one 9.5-ton skip will bring the ore to surface. The 12-ton skips will be run completely under computer control in counter-balance by a 3,000-HP double-drum production hoist manufactured by Nordberg while the 9.5-ton skip is run in combination with the cage. It is run by a smaller, 1,800-HP Nordberg hoist and will be operated manually. The skips can dump into either a 1,000-tonne waste bin or a 2,000-tonne ore bin situated in the 180-ft high headframe. This structure, engineered by V.B. Cooke, is totally enclosed and insulated. Mine ventilation air is drawn into an 80-ft deep ventilation raise situated next to the headframe and is diverted horizontally along a ventilation tunnel and into the shaft. This arrangement is a cleverly designed safety feature that keeps the deck area and headframe in fresh air no matter what emergency arises during the course of operation. The steel shaft could not be upcast, owing to the possibility of corrosion by sulp
hur-laden mine air (the ore has a high sulphide content).

At the time of our visit, electricians were preparing to fire up the 400,000- cu-ft-per-minute main ventilation fans, which are situated below surface so as to suppress noise. The building over the ventilation intake will be equipped with three types of mine air heaters — electric, propane and a glycol heat-exchange system which will draw heat from the mine’s three 3,000-cu-ft-per-minute air-compressors. The system should be ready this fall.

Immediately adjacent to the ventilation building is the LAC-designed slurry plant, the heart of the mine backfill system. (Dumagami was so impressed with the design that it has copied it). The plant is equipped with two 250-tonne, 2 4-m-high silos, one for fly ash and one for portland cement, plus a large mixing tank. A fill raise, yet to be reamed, will provide access into the mine.

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