Boulby Potash Mine
14/09/08
I was lucky enough to get invited on a trip to Boulby Potash Mine in North Yorkshire, which is Britain's deepest working mine. Potash, (potassium), is mainly used in fertiliser, and at Boulby they extract about a million tonnes of it a year. The layer of potash is deep underground, about 1km down, so it's a mammoth operation to extract it. We weren't allowed to take any photographs underground as no electrical equipment was allowed down there, not even watches, so most of the pictures on this page come from the owners of the mine, Cleveland Potash Ltd. I couldn't even take any pictures on the surface as it was such a miserable day!
The two columns to the right of the picture are the mine shafts that go just over 1km straight down. One is used for transporting people, and the other to get the rocks up to the surface. The winches are powered by the largest DC motor in the world.
Most of the mining takes place under the North Sea.
The bottom of the shaft. The lift is three stories high, so a lot of people can travel at the same time. It took us about five minutes to travel down. This shaft is also used to force air into the mine. The air is such a high pressure that we had to go through three air-locks before we would enter the lift at the top of the shaft. The sound of air rushing past you as you descend into the darkness is amazing. The air eventually exits the mine via the other shaft. An intricate system of passageways ensures that the air flows properly around the mine, and that the warm air returning from the working face doesn't mix with the cooler air entering the mine. Huge polystyrene blocks are used to ensure the air doesn't go the wrong way.
The main roadways are cut into a layer of rock salt, which is a lot stronger than the layer of potash. We hopped on the back of a transit van to make the 7 mile journey to the working face, out under the North Sea. Very little of it was nicely illuminated like in this photo, and it was a strange feeling to be travelling at speed in the pitch black, with just a few inches clearance above your head.
This is the machine that's used for cutting the roadways.
This is a chunk of rock salt that I got from the wall of one of the roadways, about 4 miles out under the sea. The rock salt from Boulby makes up about half of the salt used for de-icing Britain's roads. They also ship a large quantity of it abroad, mostly to the USA, via a facility in Holland.
The layer of potash sits above the rock salt and this giant machine is what extracts it. It made a great noise! The miner stands behind it with a remote control - think Robot Wars on a massive scale.
The working face. It was really hot down there, about 38 degrees centigrade.
The rocks were then transported on these trucks to a 7 mile long conveyor belt.
A chunk of potash from the working face.
The potash is in a constant state of collapse, so bolts are inserted to keep the ceiling up as long as possible. They also insert 'tell-tales' which show them how much the ceiling is sagging. I asked them what the colours meant, green = good, yellow = beginning to fall, red = run! I then pointed out that several of the tell-tales were on red and they just grinned...
The support pillars are deliberately allowed to crumble to take the stresses away from the ceiling. All the time I was down there I was told to keep away from the edges.
In order to find out where the potash is, long bore holes are drilled which produce core samples 2km long. Once a geologist has looked at them and marked it on their survey, the samples get thrown in a massive heap, so I was allowed to take as much as I could carry. On the left is pure salt. In the middle is salt contaminated with other minerals. On the right is what they're after, potash.
It was an amazing trip, and a real chance of a lifetime. Everybody at the mine was really friendly and happy to answer our many questions. A huge thanks to Neil Rowling who showed us around, and Cleveland Potash Ltd (now ICL Boulby) for allowing the trip.