Boulby Potash Mine 2nd Dec 09
I have waited a long time to visit Boulby mine, I think I am right in saying it is the deepest mine in the UK, and was once the deepest in Europe, I was not disappointed.
We left North Wales in two cars, early on a wet Wednesday morning, Evan volunteered to drive, and Glen, Adam, and I were happy to let him, Marty, Joel, Miles, and Nick, were in the other car.
In our excitement we arrived in Middlesbrough about two hours early, so we had a leisurely breakfast in an industrial café before setting off for the mine.
On arrival, still, half an hour early, the friendly security man sent us to the administration block, where the Lady at the desk asked us to wait in an induction room until our guide arrived.
We were offered tea and coffee, while we waited, and very soon Neil Rowley arrived. Neil is a mine engineer, with a long history in coal and potash mining, and he could not have been more helpful, answering our questions, and pointing out things of interest throughout the day.
Neil spread out maps of the area, and plans of the mine, explaining how the potash had been discovered in the 1930’s by ICI, when they were looking for gas deposits.
We were then shown an interesting slide show detailing the history of the site, up to the present day, during the slide show, we were offered bacon sandwiches which we all partook of, except Marty, (honest).
Neil then explained some of the technical problems of mining potash at these depths, and how these problems have been overcome, now, and historically.
We were now getting close to our allotted time of descent which was twelve o clock, so after some safety instruction, we were kitted out with boots, helmets, overalls, and various bits of PPE, then we got our Oldham lamps and self rescuers, we were given a bottle of drinking water, and a belt to hang everything on, and finally we were ready to descend.
There are two main shafts, one used mainly for man riding, and the other for raising the ore, (potash and salt), we waited at the top of the smaller shaft while the cage came up and disgorged it’s cargo of miners, then at last we handed over our descent tags and entered the cage.
The shaft is twelve hundred and sixty metres deep and we were in the larger of the two cages, which takes five minutes to reach the bottom, the cage started off so slowly that its movement was almost imperceptible, but the speed soon increased to its maximum speed of twenty nine feet per second, before slowing right down again as we reached the bottom.
As we stepped out of the cage I was surprised how cool it was, we had been told that the parts of the mine, we would be visiting, were typically about thirty six degrees centigrade, I soon discovered that the reason for the coolish air temperature around the shaft bottom, was because the man rider shaft is downdraught, so the cold air from the surface has not had time to be heated by the hot rocks around us.
We all clambered into the transit pickup which had been allocated to us, and Neil drove away from the shaft bottom along eight metre wide roads, it soon became apparent how hot, thirty six degrees actually is.
The hottest part of the mine (which we did not visit) is said to be forty six degrees.
The mine was opened in the late 1960s by ICI to exploit the halide rock formations known as evaporate sequences, which formed many millions of years ago in the Permian period, when part of the ocean became isolated, due to sea level changes and movement of landmasses, forming an inland sea similar to the Dead Sea in Israel.
As this sea evaporated away, first the salt (sodium chloride) then the potash (potassium chloride) precipitated out, forming layers of salts which later became buried by sedimentary rocks and compressed to form the halide rocks which we find today.
Neil explained to us that the roadways are cut in the salt layer which lies below the potash, the salt layer being stronger and thicker than the potash, and also because the potash is overlain by a very weak layer of sedimentary rock.
So the roads roughly follow the strata, which dips towards the west, and where they require access to the potassium layer the road is inclined up into the potash workings.
Of course cutting the roads in the salt layer produces a huge amount of salt, this is sold as road salt.
We were first taken to visit a new underground workshop which was being built to assemble equipment, too large to fit down the shaft in one piece.
Then we were taken to the end of a roadway which was being extended forward, really this is two roadways, because the ventilation system requires a flow and a return, so they cut alternately the left and right side of the central column, the huge access doorways between the two tunnels are later filled in with massive polystyrene blocks and sealed with expanding foam.
Fortunately, for us, the huge cutting machine was broken down, which gave us a chance to get a good look at it, as the fitter replaced a pipe and some tungsten carbide picks.
The four metre wide cutter reminded me of a huge lobster as it crouched in the junction between the two tunnels, and the miners operated the cutting drum up and down, to test the hydraulic pipe and fit new picks.
Then it was driven back into the face and we watched it cut twelve tons of salt, in a few seconds, an electric shuttle car then coupled up to the cutter and was loaded with the salt, before driving back down the tunnel to empty its load onto the conveyor.
Two shuttle cars alternate, to empty the cutter, and the cutter, after moving forward several metres, alternately, moves over, four metres, to make the tunnel eight metres wide.
We were now sweltering in the heat, and by the way, we were several miles out, under the sea, amazing to feel so hot with all that sea above you.
We all got back into the transit, and Neil drove us to a site, where they were doing a drilling survey, here they are drilling into new ground, to test the quality of the ore ahead, in order to assess if it can be mined economically.
The core drilling process is fascinating, they drill a horizontal core two thousand, two hundred metres long, yes that is, (2,200 metres), even more amazing, is that this core is drilled in the salt layer, and they want samples from the potassium layer, so every so often, they divert the drill upwards, into the potash, then, after getting their sample of potash, they draw the drill back, before continuing forward in the salt.
I was in awe, as to how this could be achieved, and though the driller explained the process to me, I would find it difficult to explain it here.
After inspecting the drill and the core samples, we were back in the transit, and off to our next adventure.
Obviously when the name Boulby mine is mentioned, the first thing everyone thinks of, is the world famous, dark matter experiment, and that is where we were headed next.
We were shown around the outside of the dark matter laboratory and the cavern in which it is housed, then we had to blow down, with compressed air to remove particles of salt from our clothing and boots before we could enter the building itself.
The dark matter experiment is attempting to prove or disprove the existence of WIMPS, this is an acronym for weakly interacting massive particles, these particles are thought to account for the major part of the matter in the universe and without them most theories of how the universe works, come unstuck.
We were of course, unfortunately, not allowed into the technical parts of the experiment, most of which is automated anyway, the information being sent out in a data stream, for analysis elsewhere.
You may be wondering why the experiment needs to be housed at the bottom of a mine anyway, the reason is that the three thousand odd feet of earth and water above, act as a filter, this filters out interference from cosmic rays and the like, which, because they are much more reactive than WIMPS will have reacted with the earths matter before they can reach such a depth.
Of course WIMPS react so infrequently with ordinary matter that the vast majority of them pass straight through the earth, and the tiny number of reactions recorded each year, have to be massively extrapolated, in order to calculate how many WIMPS are passing through the earth.
After the dark matter experiment, we were back in our transit and on our way to see the central pumping station; this is where all the unwanted water is pumped to the surface.
Frankly, for a mine which extends seven miles under the sea, I was expecting much bigger pumps, and more of them.
All the water, which is actually brine, of course, is directed to this, central area, where it is held temporarily in a large tank, more like a canal actually, before being pumped up to the surface, by two, admittedly, large, multi stage pumps, I just expected more water, and more pumps, somehow.
We learned that the brine, when it reaches the surface is refined into such things as pharmaceutical grade potassium chloride.
Then we climbed back into the transit for last time and we were heading back to the shaft bottom and out.
Though it was now much cooler because we were back in the shaft, we were packed like sardines in the cage, as we were now riding in the second, cage which is much smaller than the one we descended in, although it did travel twice as fast, so we were at the surface in two and a half minutes.
After handing back our tags, to prove that none of us was still down there we had a tour of the winding engines, a superb piece of engineering, by English electric.
Then we had to get changed, and say goodbye to our host and guide Neil Rowley, and to Boulby mine.
I would like to thank Boulby mine for their generous hospitality and especially Neil,
for providing us with such a wonderful tour, we saw some amazing things.
The most amazing of course was Marty, refusing a bacon sandwich.
Subject: Boulby potash mine Dec 09 
Sun 13 Dec 2009, 1:10 pm
