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Kerr Addison Underground, Part Two


This article is about working underground in a stope on the 4000-foot level of Kerr Addison Mines Ltd., in 1978. The story I relate is not really specific to the working of Kerr Addison, as all underground hard rock mining would have followed similar processes as they existed in the late 1970's.

Mike Molotkin, 2010
Mike Molotkin in 2010.

I have now arrived at my assigned stope on the 4000 level after once again travelling down the Number Three shaft all the way to the 3850 level, taking the underground subway "man cars" to the internal Number Four shaft and then taking the cage down one level to 4000. I then walk from the level 4000 station to the 48-1/4 shrinkage stope -- a shrinkage stope is usually a narrower area being mined between two normal size stopes.

Once at the entrance to the stope, one is expected to open the hinged door which looks much like a fish net but its made of metal. Swinging the door up and to one side reveals a series of ladders heading down. I climb down in the fairly tight man-way making my way down another 20 feet or so and then enter the stope.

This work area is basically a large area hollowed out from the surrounding rock. Think of a space about twice as high as normal garage -- about three times as long and about the same width -- and you have a stope. Here is where the real mining takes place. Our job today is to drill and blast one set, scale and slush and clean up. So, what does all that mean? Drilling involves taking what amounts to an underground jack-hammer called a jackleg drill and then inserting various lengths of steel that have a small hole running through the centre of each length of steel. This is attached to the end of the jackleg much the same way as a drill bit fits into a hand-held drill. The tip of the steel has a diamond drill bit. This apparatus is then hooked up to a water line and an air line to operate effectively. The water keeps the dust down, and is shot through the steel via the small tube like hole in the steel to the rock surface. The air powers the jackleg as a pneumatic drill. The driller must slowly place the steel and diamond bit on the rock, and start, eventually boring a series of holes the diameter of a bicycle tire tube. My partner and I would drill about 30 holes (15 or so each) which takes about 20 minutes a hole. Then these holes were stuffed with sticks of dynamite. The stuffing takes place with a wooden tamping stick (you wouldn't want a spark to be produced here!). Once all the dynamite (about three or four sticks per hole) is inserted, the blasting fuse is connected and each fuse is then hooked together with lead wire. It is this yellow lead wire that runs to the igniting box, which is a safe distance away and usually up the same ladder we walked down.

We have notified and gathered up all the other miners in the area and they take up the position of guards to ensure nobody comes into the stope during this blasting operation. The miner operating the ignition box yells "FIRE IN THE HOLE!", and depresses the handle, causing all the sticks of dynamite to detonate. The sound is a low rumble punctuated with a clear sound of "pop-pop-pop", or what miners refer to as the "shot". It is important to count the number of shots to ensure they coincide with the number of holes, this way you can be relatively sure that all holes have been blasted.

Now its time for a coffee break or lunch break, to let the gases that are created by the explosion of dynamite to dissipate. Normally it takes about 30 to 40 minutes for this to happen. Kerr Addison had very good air quality and ventilation, so in most cases the gases were all gone and the smoke cleared in about 20 minutes.

Back in the stope we are greeted with a huge jumble of broken rock. The pile can be quite high and almost fills the floor of the stope area. Next, we hook the slusher so that the broken rock can be scooped up and dragged toward the mill hole. This hole, the size of a bath tub, is nearest the centre of the stope and connects the stope to the chute on the level below -- again like a laundry chute.

The slusher is a cylindrical shaped machine with a series of cables wound onto drums. These drums can rotate in opposite directions when levers are activated. The scraper part that actually scoops the rock into the mill hole is tethered to the slusher by wire cables. The operation of this machine takes skill, as the speed and release of cables in and out has to be timed just right to ensure a smooth action in scooping up all the rock.

Once the stope is cleaned out, wooden staging is built using posts, caps and girts to basically raise the work area up another eight feet (the height of a post) so that miners can stand on the square set to begin the drilling and blasting, slushing and cleaning process all over again. Some stopes, remember are mined upward and the next stope adjacent to your work area will be mined downward -- in these cases the floor is detonated and the workings proceed downward, removing sections of the mill hole as you proceed.

The time span to mine an entire stope from level to level (remember at Kerr Addison this was about 200 feet) normally took about four months. Each "breaking of rock" as a result of blasting, would yield about 20 tons of ore (miners call broken rock "ore"). With a ratio of one ounce of gold for every two tons of rock (that was Kerr Addison's consistent ratio) one round of blasting could yield close to 10 ounces of gold, after this ore was picked up by the level below's motor crew, dumped into the ore pass, crushed in the crusher, hoisted by the skip to the surface and then conveyor belted into the mill to be treated and then over to the refinery to be roasted, and finally poured into a brick for the waiting market!

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