ODDS’N’SODS — A river runs through it (September 04, 1995)

Reading the recent Odds `n’ Sods article about the Quirke mine flood of 1956 (T.N.M., Aug. 14/95) brought back a “flood” of memories of yet another water inflow at the Elliot Lake operation, some 33 years later.

Near the end of April, 1989, I learned that an inflow of around 1,000 gallons per mine had started, causing everything to shut down.

Upon inspection, I learned that the stope in question, 059, was in the C-reef, in a remote area of the mine below the Serpent River. The crown pillar was 100 ft. and considered to be very safe. The stope was accessible by a long ride along a haulage drift, a slow ride in a 250-ft. Alimak elevator, and a walk up a 450-ft.-long stope dipping at 30!.

As we approached the face of the last raise round (blasted a month before), a roar like that of Niagara Falls could be heard — 1,000 gallons per minute were shooting out of a series of cracks, at high pressure. And judging by its freezing temperature, there was no doubt it was coming from the Serpent River, 150 ft. above. Scaffolding had been jammed into cracks in the face, in a heroic but futile attempt to stop the flow.

An emergency response team was immediately assembled, and several consultants were already on site or on their way, among whom was Jim Roxburgh, operations manager. I was mine manager and Jim was senior to me. Somehow Jim ended up working day shift and I ended up working nights.

The primary plan was to drill a fan of diversion or relief holes into the rock mass behind the face, from both sides of the face. If the water was reaching the face by a series of fractures connected to the Serpent River and if these fractures could be intersected, then the water could be diverted away from the face. Holes could then be drilled into the face, and the fractures grouted.

The fan holes were drilled through valves. The work went on around the clock. Many of the fan holes did hit water and the flow at the face slowed to a trickle. Wooden wedges with oakum and burlap were hammered into the cracks; grout holes were drilled into the face; and a water reactive polymer grout was pumped in.

After allowing an hour to let the grout cure, the relief valves were closed and the face was pressurized. There was still some minor leaking, which additional chemical grout soon took care of. Soon, the inflow was under control.

While the crews at the face were working around the clock, other crews worked intently at other projects. Five diamond drill holes were put in by Morissette from rapidly constructed gravel pads pushed out into the Serpent River. These holes intersected the fracture system, and cement grout was pumped in to seal the fractures.

Because of the difficulty of delivering concrete and grout to the 059 stope, the decision was made early on to put down an access bore hole from surface to the stope. Redpath’s crew arrived and had drilled 230 ft., then grouted the hole to ensure that the bore hole did not deliver even more water to the stope. The hole was then completed to 260 ft., within inches of the target.

Once the bore hole was drilled, concrete was delivered to the 059 stope through a 4-inch pipe. There was some concern about how feasible it was to run concrete down an almost vertical, 260-ft. drop followed by a few hundred feet of pipe going uphill at 30!, but the crews were soon competing to see whether the day shift or night shift could pour more concrete. (Despite Jim’s claims to the contrary, those of us on night shift consistently outperformed the day shift crew.)

The concrete was used to reinforce several faces which we now considered vulnerable to water inflow. Bulkheads were poured to ensure there would be no future problem.

The flood had been caused by the connection of the mining face to the Serpent River by a series of fractures. Although little water seeped in for a month after the last round was blasted, the silty sand infilling the fracture zone slowly washed out, until it let go.