Winston Lake A WINDOW ON THE WORLD OF ZINC

To the people of a tourist town located in a non-mining part of the country, a 10-year mine life doesn’t sound like much — certainly not enough to justify spending $73 million today to scoop 600,000 tons of zinc and about 38,000 tons of copper out of the ground and then simply pack it in and leave town. That sounds too much like the boom-and-bust cycle that has been the death song of many a Canadian mining town. But it reflects a misunderstanding of how mining has changed in the 1980s. Managers of mining companies today can no more justify multi-million-dollar mine developments on the potential of finding 100 years of reserves than managers could 20 years ago. They have to base their decisions on proven reserves. However, that is not to say that, if you have 10 years of mine life now, more reserves won’t be proven up over time. That takes a strong corporate commitment to exploration spending even after a mine has been built on its initial reserves.

This is exactly what Minnova Inc. of Toronto is banking on at Winston Lake, a short distance north of Schreiber, Ont., on the north shore of Lake Superior. With reserves of 3.4 million tons grading 1% copper, 16% zinc, 0.03 oz gold and 0.88 oz silver per ton, Minnova has decided to put this deposit into production at a rate of 1,000 tons per day. Located just west of Hemlo, in relatively virgin geological terrain, this area is ripe with base-metal possibilities. Although the decision to build the mine was based on that 10-year mine life, the orebody remains open at depth and to the south. As John Carrington, vice- president of operations says, “We’re confident we’ll be there a lot longer than 10 years.”

Joint-venture partner Zenmac Zinc has diligently worked this area since 1964 — a testament to that company’s confidence in the mine-making potential here. (Minnova’s 100% ownership of the Winston Lake mine is subject to a 10% royalty on the net proceeds of production, payable to Zenmac Zinc after Minnova has recouped the expenditures it incurs in placing the mine into production. Zenmac has notified Minnova that it considers itself to have an option to become a 20% joint-venture participant in the mine by reimbursing Minnova for 20% of the expenditures incurred to date. The matter is still unresolved).

Although Carrington says Minnova is prepared to pack it in after just 10 years, the company is committed to extending the present mine life. In fact, another massive sulphide deposit, about a mile southwest of the Winston Lake deposit, has already been delineated by the company. It is known as the Pick Lake deposit (see our Core Shack story on page 39). And Noranda Exploration has been working for three years on ground at Victoria Lake, to the southeast, looking for the same kind of deposit Minnova discovered at Winston Lake in 1982. If these programs click, sustained economic growth may very well be in the cards for this part of Ontario.

By then, Minnova will already have much of the necessary infrastructure in place to make further mine development less expensive. Some $3 million has been spent upgrading the 8 1/2/-mile gravel road that provides access to the mine site. Another $1 million has been spent on electric power lines into the site.

Minnova was known as Corporation Falconbridge Copper until August, 1986, when Noranda-controlled Kerr Addison Mines took over the company. Now, under new management, the company is doing everything it can to ensure that capital costs of the 1,000-ton-per-day milling complex are kept to a bare minimum.

Winston Lake is a rarity in that it’s one of only two zinc deposits likely to come into production in North America in the near future. Cominco’s Red Dog deposit in Alaska is expected to come on stream in the 1990s, adding 700,000 tons of low-cost lead/zinc concentrates to world markets every year. But, according to Carrington, the development schedule at Red Dog had no influence on Minnova’s plans to bring the property to production as quickly as possible. Production at Winston Lake is slated for the end of the first quarter of 1988.

One piece of good fortune, which has influenced the $73-million capital cost of the project, is the company’s idle mill at Sturgeon Lake, 125 miles away. The mill was dismantled and trucked piece by piece to Winston Lake. Being able to attract competitive construction contracts in a relatively stagnant northern Ontario construction market hasn’t hurt either.

Most of the major components of the Sturgeon Lake mill have many years of useful life left. They will be re-used in the newly-constructed Winston Lake mill building. The milling circuit, designed by Leslie Engineering, is a relatively simple grinding, flotation, thickening and filtering circuit. It has been designed to produce two concentrates from the unique ore that will come from the underground mine at Winston Lake. The original metallurgical studies were done by Lakefield Research of Peterborough, Ont., between 1983 and 1986.

The only new milling equipment Minnova has purchased to complete the circuits were 26 flotation cells manufactured by O&K of Finland and two automatic pressure filters manufactured by Larox. Even the mill’s X-ray analysis machine is not new. It is an old, refurbished model that came from Sturgeon Lake. Minnova decided to have it digitized by Harrison Cooper of Salt Lake City, Utah instead of purchasing a new on-stream analyser, because the top-of-the-line unit could handle only eight process streams at the time. Since that decision was made, O&K has come out with a 10- stream unit. “So much for trying to stay abreast of technology,” says Mill Superintendent Bill Mills.

The mill was scheduled to be turned over Dec 15. It is expected to employ 22 people. “We’ll get it up and running, then get fancy with process controls later,” Mills says.

Concentrates will be trucked in covered trucks by sub-contractor Trans Provincial to the railway siding in Schreiber. From there, cp Rail will take the copper concentrates to Noranda’s Horne smelter in northwestern Quebec and the zinc concentrates to the Canadian Electrolytic Zinc refinery in Valleyfield, Que. The mill is scheduled to produce 330 tons of zinc concentrates and 30 tons of copper concentrate per day. Precious metals will be contained in the copper concentrate.

Another prudent move made by Minnova has been the company’s hiring policy. Minnova is bringing a highly-trained group of young, though relatively inexperienced, people into the project right from the start so they can see the operation grow. But the company is not putting them in charge right away. Mine Manager, Tom Dickson, and his four superintendents: Bill Mills (Milling), Jim Koski (Construction), Bill Brosko (Mining), John Smrke (Employee Relations), and Colin Crown (Office Manager) have accumulated a total of 130 years in the mining industry. They are the “teachers”, if you like, at Winston Lake, and the young employees are the “students.” Minnova has tried to keep the student-to-teacher ratio down to about eight-to-one or 10-to- one in an attempt to avoid problems such as those which plagued the Quintette coal mine in B.C. during its start-up in 1984.

Hiring seasoned consultants for the job of developing the mine was also a key move on Minnova’s part. A total of 16 different contractors and sub- contractors on the site when The Northern Miner Magazine paid a visit this fall. Environmental Protection

Protecting the environment has been high on the list of priorities of many of these consultants. A lot of thought and careful planning has gone into the problems of how to treat tailings from the mill; how to reclaim water from the mill tailings; and how to divert branches of the Whitesand River. The Ontario Ministry of the Environment is not going to let the company come in and pollute the local streams. The minesite garbage dump, for example, was intentionally located at an elevation above the tailings pond. That way, any run-off water makes its way into the tailings pond where it is contained, rather than going directly into the Whitesand River downstream of the d
am to contaminate this fine little trout stream.

Before constructing the main tailings dam, Geocon of Mississauga, Ont., the geotechnical consultants on the project, removed all the overburden from a 20-ft-wide strip of bedrock along the length of the dam. Then, to clean out all the cracks and crevases, 30 people using screwdrivers and brushes worked on their hands and knees for several days removing all the loose material from the bedrock. A so-called “tooth cap” of concrete was poured to provide a level working surface on which to place the glacial till which makes up the relatively impermeable core of the dam.

A line of permeability test holes, spaced evenly along the length of the dam site, was drilled to test for possible leakage through fractures in the bedrock under the dam. Once Geocon grouted these fractures with concrete and was assured there was no leakage, construction of the dam went ahead.

Downstream of the tailings pond, Minnova has decided to construct a polishing pond to allow more time for even more heavy metals to settle out of the tailings water. By adding lime to the pond, ph levels will be raised so that most of the heavy metals will precipitate out of solution. Although not required in the past, polishing ponds have become standard features in the construction of new Canadian mines.

Minnova is in the final stages of working out the details of an environmental protection agreement with the provincial government concerning the clean-up of old mine dumps left by the old Zenmac mine, which operated at a time when environmental regulations were far more lax. Underground Development

Underground, the first stope to be mined will probably be a longhole stope on the bottom (615-ft) level, at the southern end of the orebody. The longhole method was chosen here because of the narrowness of the orebody. About 30,000 tons will likely come from this stope.

The wider, upper portion of the orebody will be mined by cut-and-fill methods. A captured ramp (one which does not extend all the way to surface) will provide access to the various sublevels. The sublevels are spaced every 65.6 ft and are driven in the hangingwall of the orebody. Consisting of gabbro and cherty tuffs, these rocks are more competent than the altered volcaniclastic and mafic flows that make up the footwall. Development workings are normally located in the footwall of underground mines, but in this case the hangingwall is more competent, so the shaft was driven here instead. It cuts through the orebody at about the 625-ft level. A 164-ft shaft pillar was designed by Golder Associates, Consulting Geotechnical & Mining Engineers of Rexdale, Ont.

Crosscuts, spaced every 197 ft along the strike length of the orebody, will be driven from each sublevel drift. There is an estimated 1,476 ft of lateral development required on each level, making this a rather expensive method of mining. Mining contractor J.S. Redpath prepared the pre-production underground development work.

Ore and waste passes extend from the 455 level, down to the 615 level. They were driven using the Alimak method.

On the 615 level a Roxon-Rammer hydraulic rock-breaker will be used to break oversized chunks of ore caught by the grizzly. Oversized ore boulders in the stopes will be broken by a hydraulic hammer attached to a mobile piece of equipment. The openings on the grizzly measure 12×14 inches and it has been designed so that it can be lifted out and a new one quickly “dropped in” with the help of an overhead crane. Kent Air supplied a hammer and boom as well as a sound- proof booth for the operator.

The coarse ore will be skipped to surface for storage in an 800-ton bin. The mine will operate for five days a week, and the mill will run seven days a week. So ample ore storage is required.

Ore will be crushed by a 36×46-inch jaw crusher, then a 5 1/2-inch short-head cone crusher before being conveyed to the mill. The jaw crusher came from the Sturgeon Lake mine and the cone crusher came from the Manibridge nickel-copper mine near Wabowden, Man. The ore storage bin was also salvaged from Sturgeon Lake.

The waste pass will serve double duty: both for waste rock and as a fill raise. Backfill consisting of classified mill tailings or waste rock for mined- out stopes will be transported from the raise to the stopes with a scoop instead of a truck. This way, the company can eliminate the expensive chutes that would be needed if trucks were used.

Underground equipment was being assembled in underground garages at the time of our visit. Equipment will include three Tamrock, single-boom jumbos, three Eimco-Jarvis-Clark 6-cu-yd scoops, two used Eimco- Jarvis-Clark 5-cu-yd scoops and two new Eimco-Jarvis-Clark 285 scoops. The company will also use two second-hand 13-ton trucks (one from Eimco-Jarvis-Clark and one from dux). Auxiliary equipment includes two scissor trucks.

Total mining costs are expected to be about $40 per ton of concentrate, making this mine a profitable one for Minnova if zinc and copper prices stay at their current levels or rise even higher.