|Towards Porthmadog||Tunnel South|
|Toward Blaenau Ffestiniog||Tunnel North|
There are two Moelwyn tunnels. The first was completed in 1842 and replaced the original 1836 inclines and allowed the FR to have a continuous gradient from end to end. It is 730 yards long. Previously wagons had to travel up and down an incline to go over the top of the tunnel. (Click here for pictures and more detail of the Old Moelwyn Tunnel.)
The second tunnel (275 yards long) was necessary because the pumped storage hydro electric scheme flooded the top end of the old one. Work started on 1st September 1975, breakthrough being achieved on 1st May 1976. It was finished in 1977, although work continued the following winter to "Shotcrete" the inside to hold the cracked rock.
As no one has described the operation of boring the tunnel I will try to do so. My experience is based of a week with the tunnellers in 1975. If I have made errors or omissions then feel free to correct. Our days started before daylight being picked up by Land Rover at Glanypwll. We had the choice of starting later but it would have meant a walk from Tanygrisiau. Once on site the tunnellers would start clearing the rock from the previous day's blasting. Normal practice was to blast just before going home, leaving the dust to settle overnight. The mine loader would go into the tunnel towing a wagon. The operation of the mine loader needs to be described to understand the operation. Imagine a mini JCB on rails. It would scoop up a shovelful of rock but was able to lift this over the driver and deposit it in the wagon behind. When the wagon was full it would shunt it out to a loop line and take an empty from the other line. Once 6 or 8 wagons were full a Simplex diesel would drag the rake out and up an incline to the "Grizzly". This was a grid over a hopper. The wagons were tipped in here and any rocks too big to pass through were persuaded to do so with a sledge hammer. Under the hopper was a conveyer belt which lifted the rock to a grader under which were three lines of wagons ready to receive three grades of rock. These were fines, ballast and anything bigger. The ballast was taken to wherever it was needed, the large rocks were dumped on the inside of the Spiral at Dduallt and I don't remember what happened to the fines. Sorting the rock went on all the time but it would only take an hour or so to clear the rock from the tunnel. Once that was done, the tunnellers started drilling for the next blast. From what I remember they drilled about 6ft per day but on a reduced diameter; once they had gone right through the tunnel they then went back to open it up fully. Unfortunately, the rock was more unstable than expected and the whole tunnel had to be lined with concrete, Shotcreting. Apart form the three tunnellers those employed on the tunnel included Bunny Lewis, Norman Gurley, Martin Duncan and David Payne.