Hope Brook entering production

On the remote southwest coast of Newfoundland, where the caribou outnumber the people, a gold mining crew is feeling triumphant. Its year-long struggle with the elements is starting to pay off. The heap leach pad is being loaded with ore and cyanide will begin sprinkling any day now at the Hope Brook Gold mine, 50 miles east of Port Aux Basques. While it won’t officially open until September, 1988, the operation expects to pour its first bullion at the end of this month.

“We’re very proud of this project,” says General Manager W. J. Fotheringham, “and we’ll be even prouder once we start cranking out the gold.”

With an average gold recovery rate of 126,000 oz per year, Hope Brook will be the sixth largest gold producer in Canada (the 11th largest in North America), according to parent company BP Canada. In addition, it is the only gold mine on the island and one of the biggest heap leach operations in the country (N.M., Aug 4/86).

An inclined ramp was begun in February and has progressed almost 600 m toward the first development level. But the underground operation is not expected to enter full production until the fall of 1988. In the meantime, reserves are to be mined via open pit because the orebody outcrops at surface.

Open pit reserves of 1.1 million tons grading 0.13 oz per ton will be scooped out at the rate of 1,750 tons per day. This ore, plus an additional 86,200 tons from development of the underground mine, will be heap leached to extract an estimated 75,420 oz gold (28,070 oz in 1987 and 47,350 oz in 1988). Underground reserves have been estimated at 10.6 million tons grading 0.13 oz per ton.

The heap leach operation was put in place principally to generate early cash flow in the order of $21 million throughout 1987 and 1988, says Mr Fotheringham.

“The mill circuit is designed so that both heap leaching and conventional carbon-in-pulp milling can be carried out concurrently. One reason for this is so we can draw revenue from the heap leaching while the mill is being commissioned (structural steel was being erected at presstime). Another reason is so that any lower grade ore from the open pit or from underground development can be heap leached, if we choose to do so. Of course, that decision will depend on the price of gold and on the availability of such lower grade ore.”

Mine Manager Julian Bennet explains: “What you must understand about Hope Brook is that it was necessary to enter production quickly in order to generate early revenue. The reason is that Hope Brook is not the most robust of projects. Grade is relatively low.”

In fact, the size of the open pit has been increased so that 1.1 million tons can now be extracted instead of the original 754,000 tons. This will help supplement the ore which is to be processed during the first 4-6 months of underground development.

The heap leaching operation is standard. After the ore is crushed, the cyanide solution is allowed to percolate through it, dissolving the gold, which is subsequently extracted from the solution with the aid of carbon columns. Recovery from the process is only 70% (1,760 tons per day) compared with 91% (3,300 tons per day) from the future mill.

About 48,840 tons of — 3/8/-in material have been laid on the heap leach pad. This layer serves to cushion the liner from the heavy equipment that will be loading the — 1/2 -in material. The pad is scheduled to last a year and a half, after which time carbon-in-pulp milling will occur.

Meanwhile the underground ramp is being driven at a gradient of –12% from surface, which will allow both the service access and the ore haulage exit from the mine. A ramp was decided on because the 400-m orebody is not deep enough to justify sinking a shaft.

“Our main target is to develop the first and second levels so we can start mining the ore between those two levels,” says Bill Leathem, underground superintendent. The workings, which consist of five levels at 65-m intervals, will be mined using blast-hole open stoping with delayed fill.

Total gold production of 1.16 million oz is expected throughout the underground mine’s 11-year life span.

Operating costs from the heap leach will be $162(US) per oz of gold, while costs for the underground production and conventional milling are estimated at $190 per oz. That works out to an over- all average production cost of $188 per oz.

Over-all construction of the minesite is 34% complete, with the heap leach phase (including gold refinery) 90% complete. All construction is on schedule with the exception of the permanent accommodation complex, which was delayed three months because of severe winter weather.

However, workers are expected to begin occupying the complex later this month. Also, the size of the construction camp had to be increased at a cost of about $1 million. (The total capital cost of developing the mine is $150 million, including up to $40 million for infrastructure alone.)

There will be about 250 permanent employees on the project when the construction phase is completed on July 31, 1988.