Boulby Potash Mine

North Yorkshire Moors. Depth 2100m. Length - a few hundred km.

Grade I - as long as the winch is working :-)

John Mills, Michael Rudd, Dave Neesam, Sara McIntyre, Ursula Collie, Steven Verity, Gareth Carson & Paul Brooks.

We arrived at the mine for 4pm, met our guide Neil and were issued with helmets, lamps (Oldhams), self rescuers (escape respirators), goggles, masks and safety shoes. We had a short wait as the lifts were being used to transport steel into the mine for ongoing work on the lift shafts. The man lift is accessed via a 3-door airlock as huge fans blast air down the shaft to ventilate the mine. We handed our tags over to the lift man and stepped into the lift cage. There were 2 levels, each capable of taking 12 men - the other cage is larger and can take 70 men. We were informed that there were about 100 men in the mine that evening, but there could be approx. 400 during the day.

The trip to the bottom lasts about 3 minutes, belying the distance - 3640 feet (1100m) - a long way to prussik! We stepped out at the bottom and moved away from the howling draught from the fans to our transport for the trip - a Ford Transit. They maintain a fleet of these down the mine (we passed the extensive workshops on our trip) and they live and die down there. Apparently they don't rust as the air is very dry, despite the roadways being in the lower salt workings.

The mine currently covers a north - south extent of 15km, containing several hundred km of workings. We went into the shallower northern workings, which extend out under the North Sea. The southern area goes down another 800 - 1000m below the bottom of the lift - over 2000m below ground level.

The northern workings are much cooler (they don't take visitors into the very warm southern area), but it is still balmy. I'm not sure of the temperature (I was told high 30s C before the trip, but I doubt this where we were). They drill ahead to locate the potash, and then mine 4 parallel 'roads', which are about 5m wide by 3m high with connecting cross cuts. The resulting pillars partially collapse, relieving the stress (as does mining the salt levels below). The miners are very impressive machines - remotely controlled on a wandering lead. They munch the potash into a pile on the ground. In a separate operation they pick it up and tip it into 'cars', which transport it to the conveyor belt leading to the rock lift. The miners run forward 12m before moving to another road, then the roof is bolted to stabilise it.

The bolting machine is also very impressive (it makes tapping away with a bolting kit seem really hard work). It drills the hole (in less than a minute), the head turns and resin is fired into the hole by compressed air, then the head turns again and a 1.5m bolt is screwed into position. The bolts are spaced at about 1m over the entire roof. The machinery is all electrically powered (except for a lift truck and the Transits) and they are very careful to suspend the cables out of the way from roof bolts. The cars have a trailing cable, which is reeled in and out automatically. The men work a rotating shift on the machine, taking breaks to keep the operation continuous.

After returning to the surface we visited the winch house. The machinery for the two shafts is housed in the same building. The winch hauling the rock uses the northern hemisphere's largest electric motor - 7000 hp. It can haul 30t loads of potash to the surface in little over a minute. It was interesting to note that the basic system is virtually identical to the water powered winch in Sir Francis Level in Swaledale - just on a slightly larger scale.

The trip was a fascinating insight into a different world - highly recommended!

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