About 2 billion years ago when this planet was a chilling, uninhabitable place, a pre-Cambrian stream laden with uranium-rich gravels emptied into a lake or inland sea just north of what is today the north shore of Lake Huron. About 35 years ago, a prospector named Franc Joubin theorized that uranium could be had in commercial quantities from the buried and hardened gravels. He was right of course, and within the space of about five years something like 20 mines were drilling into the uraniferous paydirt under the rolling bushland of Elliot Lake, Ont. Some are still at it today. Denison Mines has its big operation, clad in its distinctive yellow and green, perched on the shores of Quirke Lake. Rio Algom Ltd has three mines — Quirke II and Panel mines, both of which are across the lake from Denison’s, and Stanleigh, which is south and nearer the actual townsite.
On a recent visit to the area, The Northern Miner Magazine toured the Panel operation, a mine that rode the uranium rollercoaster to the 1950s peak and eventual bust in the early 1960s. It was closed in 1961. Armed with new uranium supply contracts, mostly from the United Kingdom and the United States, Rio Algom decided in the mid-1970s that Panel could be resurrected. In 1975, mine dewatering and rehabilitation began. The first yellowcake from this second go-round came out of the mill in 1979. Currently, the mine produces at a rate of 4,700 tons per day and, to the delight of its amiable mine manager, Peter Bedford, it accomplishes that mining rate with the best safety and loss control record going — the mine has the distinction of being the only current mine in the world with a 5-Star safety and loss control rating, which was awarded by the Mines Accident Prevention Association Ontario (MAPAO). The award is based on the International Safety Rating System, which is an international standard for evaluating safety practices and loss control management.
The Panel headframe sits on an island in Quirke Lake. A short causeway connects it to the mill on shore. The island was chosen as the site of the shaft collar because it was the closest piece of real estate to the orebody, which runs south of the island along an east/west- trending direction under the lake. The 5-compartment shaft is 1,848 ft deep. Two, 7-ton skips hoist the ore to surface after a jaw crusher reduces the material to –6 inches.
The ore from production workings is hauled in 140-cu-ft side-dump Granby cars pulled by 12-ton Goodman trolleys. Haulageways, roughly 10×12 ft, have been excavated on five levels — the 2, 4, 6, 9 and 12 levels. The second level is the main station for miners, who are driven by enclosed Teledyne man carriers to the stopes. Production (on a two-shift, five-day work week) is currently split almost equally between the eastern and western portions of the orebody. By 1991, most of the production will come from Panel East. The year following, however, the supply contracts run out. To carry on beyond that year, Rio Algom must sign new long-term supply contracts — an uphill battle with current spot uranium prices sitting at slightly better than $16(US) per lb. Undaunted by (or perhaps because of) the spot market price, Panel’s planners have proposed driving a 3,600-ft- long ramp into the e astern workings 750 vertical ft below surface. At a cost of $1.5 million, this 12×20-ft service incline should save the mine about $1 million a year in operating costs. The work will be done as an in-house project.
On The Northern Miner Magazine’s tour of the underground, which was conducted by Mine Captain Don Rioux and Mike Starnyski, the mine department’s loss-control coordinator, we left the cage at Level 2 and boarded a four-wheel drive jeep. The jeep went along a –20% ramp, past a 6th level repair shop for track equipment, a 5-bay repair and rebuild garage for small tractors and jumbos, an immaculate, computer-connected warehouse and a salvage shop. This latter was set up as a cost-cutting measure. Service crews scour the mine for any pieces of scrap or misplaced equipment — bent pipes, rockbolts, ventilation ductwork, pumps, timber and so on. Anything and everything that can be put right is, and then sold to the appropriate work crew. The system generates considerable savings (at least as much as $20,000 a month).
From the salvage yard we drove east to a development area on the 5th level. Generally, development begins with a sill drift, driven approximately along strike and leading the mining sequence. The heading serves as a travelway, an exploration heading to test mining heights and ore grade, and a service drift for compressed air, electrical power, water and ventilation. From this primary sill drift, stope inclines or declines are driven at an angle to the sill drift to create an apparent dip of 12% in the face. The method of mining is room and pillar. From the inclines or declines, the stopes are slashed out to 50 ft or 65 ft wide depending on the depth from surface. The spacing of the individual stope drifts is dictated by the depth of the ore from surface, a reasonable extraction rate and local ore dip (in the eastern extensions the ore dips 20 degrees ).
Stope drifts are advanced under fan-forced air ventilation along strike or on a shallow apparent dip shaped with a “shanty” back to conform to the dipping orebody. Rib and sill abutment pillars are left, as are other random and wedge pillars that accommodate unexpected geological structures and limit strike spans. Extraction ratios run between 75% and 85%.
Panel is experimenting with a variation on the room-and-pillar theme. As planning engineer Al Scruton explained, rather than driving a stope drift and then slashing out, a parallel series of 35-ft-wide stope drifts running from sill drifts and separated by pillars would be driven. No slashing would be required. While extraction ratios would be slightly lower, the production rate in tons-per-manshift would jump considerably because production jumbos would not have to be moved as often as they are with the current system. Another alternative, though still in the conceptual stage, involves 65-ft-wide openings in stope headings. “The way the ground is we can open up to 65 ft,” Scruton said. “If we do this, we’ll get a better extraction ratio from the wider stopes.”
In general, production is organized into “trackless units” of 16 to 20 workers working on a two-shift basis. Each unit has at its disposal two, 6- or 8-cu-yd LHDs, a two-boom electric/ hydraulic jumbo, a rock bolt jumbo, an ANFO loader truck and support equipment. During the tour of the 500 East development area, Rioux explained that three, 8-man crews are operating the trackless, rubber- mounted equipment. (Crawler-type equipment simply doesn’t work at Panel because the silica-rich rock is too abrasive for metal tracks.) The development-to-stope ratio is about 60:40, according to Rioux, which means that 60% of the production tonnage comes from development ore and the remainder from production stopes. Last year, the mine produced 2.1 million lb of uranium. About 85,000 lb (or about 4%) came from bio-leaching and mine water. In total, the mine has seven, 2-boom, electric/ hydraulic jumbos (both Boart and Atlas Copco) and two, 2-boom pneumatic jumbos. The latter machines were built by Panel’s maintenance department and fitted with Tamrock booms. Conventional jack legs and slushers were being used in the eastern reaches of the orebody, but these are being phased out. It should be noted too that, in the northwest portion of the mine, blasthole methods have been incorporated in a small section of the orebody with a 70 degrees – to-80 degrees dip, which is unusually steep for the Elliot Lake camp.
To save on blasting costs, Panel reduced the diameter of its drillholes in room-and-pillar mining to 1 1/2 inches from the former 1 3/4 inches. “It still gives us a good, clean blast and we save on ANFO,” Rioux told The Northern Miner Magazine. ANFO, carried in 1,000-lb bags, is delivered to the face and loaded by diesel-powered Teledyne carriers. Mucking out is accomplished with trackless equipment — in total, 12, 8-cu-yd LHDs, two 6-cu-yd machines and two 3 1/2-yd, low-profile LHDs. The bulk of these were manufactured by Eimco Jarvis Clark, although several Wagner Scooptrams are also part of the development/production machinery. The trackless haulers include two, 26-ton Eimco Jarvis Clark trucks and two, 13-ton Wagner trucks. The haulers carry ore and waste rock to orepasses and boxholes that lead to haulageways excavated in the footwall of the orebody anywhere from 30 ft to 90 ft below the primary sill drifts. As mentioned earlier, trolley-powered trains haul the ore to the shaft area.
In all openings of the mine, rockbolting is done on a 4×4-ft pattern. Acting mine superintendent Bruce Knack explained the reason for this: “You’ll find that in the history of the Elliot Lake camp, the orebodies are a strong structure, but they have weaknesses in them.” In most areas of the mine, 6-ft mechanical bolts are used, although Swellex bolts are required in the contact zone with soft argillite rock.
Geologically, the Panel orebody differs little from the rest of the Elliot Lake camp. In a written description prepared by Rio Algom, the Elliot Lake geology is explained as follows:
Uranium deposits are found near the base of the Huronian sedimentary strata. The Huronian rocks, consisting of a sequence of quartzites, conglomerates, argillites and minor limestones are preserved in a west- plunging, basin-like structure or syncline. The Huronian strata is about 2 billion years old and rest on still older volcanics, greywackes, iron-formation and granite rocks. The Huronian sequence is marine. The lower units are coarse, first-generation quartzites derived from large areas of deeply weathered granitic rocks lying to the northwest. The basal quartzites were deposited near shore by south-easterly trending drainage into a shallow north- transgressing sea and were distributed laterally by shore currents. The uranium deposits are geological units, consisting of layers of quartz-pebble conglomerate and interbeds of quartzite deposited from a southeast-draining river system. Where the river system was sufficiently large and had flow competence, the sediment deposited downstream from the fall point or debauchment point of the river was the larger resistant detritus, namely the quartz pebbles and heavier sand grains.
The heavier sand grains from the granitic source included minerals that were uraniferous and thorian. Other elements were also concentrated in these piles and are represented by their equivalent heavy accessory minerals. The other elements of interest are yttrium and the rare earths.
The paper goes on to say that the Panel geology consists of uraniferous quartz pebble conglomerates that occur at the base of a thick sequence of Huronian sediments just above a major unconformity. These sediments have been folded into a gently east/ west-striking syncline. Panel is on the north limb of the syncline. Because of faulting, the ore dips are irregular, varying from –70 degrees to flat-lying to a reverse dip in some places. (Most of the orebody dips 10 degrees to 30 degrees .) The `C’ reef is the mineable orebody, which consists of a lower reef of pebble conglomerates, a middle reef (or parting) of intermediate quartz and an upper reef, again of pebble conglomerates. In the western sections of the mine, ore-grade material is extracted from the footwall of the lower reef to the hangingwall of the upper reef. Eastward, the lower reef is usually the only one of the three that is economic. The orebody is situated at depths of 500 to 2,000 ft below surface. “If we can get average grades across the three beds we will mine it,” said Bedford. “But usually we just mine the lower reef.” The lower reef ranges anywhere from 8 ft to 14 ft in width. “You can follow it with the naked eye,” Bedford said of the reefs. “But we sample to ensure that it is ore grade.”
At a cutoff grade of 2 lb U3O8 per ton, reserves stand at about 10 million tons. “We’re good to 1998 at our cutoff grade today,” Bedford said. “Our orebody extends beyond that, but it’s not economic at this time.” Beyond the eastern boundary, surface drill holes have been shot into ore- grade material, he added. Currently, crews working with a rail-mounted Atlas Copco LM 56 mucking machine, a muck car and motor are driving a 2,000-ft exploration drift eastward.
Of course, all this activity might prove fruitless by late 1991, when the current contracts near expiry. But Bedford said that Panel’s crews are doing everything they can to cut costs. (Exactly how high current production costs are, the company’s head office won’t reveal.)
Panel’s workers can only hope that the uranium market perks up significantly between now and that 1991 deadline. — 30 —
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