Moelwyn Tunnel

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Not to be confused with Old Moelwyn Tunnel
Moelwyn Tunnel
The New Moelwyn Tunnel seen from the North end. Photo: Alastair Littlewood
Type Tunnel
Status In use
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The Moelwyn Tunnel takes the Ffestiniog Railway's Llyn Ystradau Deviation through the hills between Dduallt and Tanygrisiau. This is the second Moelwyn Tunnel built to replace the previous one which had itself replaced a pair of inclines. The second tunnel (275 yards long) was necessary because the pumped storage hydro electric scheme flooded the top end of the old one.

The new tunnel is much larger in width and height than the old which has removed the restrictions it imposed on the railway's loading gauge.

Boring the tunnel[edit]

This had to be blasted through hard abrasive syenite rock and after extensive planning, construction started in September 1975 and was carried out by three Cornish mining engineers, Robin Daniel, Bob Le Marchant and Pete Hughes, supported by generally less than 20 direct labour staff (12 engaged on a government subsidised employment scheme), plus volunteers, and with the aid of a substantial tourist board grant. The support work included the on-site crushing and grading of the excavated rock to make ballast in several sizes for use on the new railway.

The face was advanced by blasting, and the loosened rock removed by an Atlas-Copco pneumatic mine loader, (known as "The Mucker") which was described at the time as probably the most expensive single item ever purchased new by the FR (£5,800), and the first brand-new item of motive power on the line since 1886[1]. This was a four-wheeled unit with an excavator bucket at the front and a footplate for the operator at one side, and emptied its bucket into a wagon behind. It was powered by an external compressor through a flexible hose. A battery-electric loco was obtained to shunt the wagonloads of spoil and it and the Mucker were sold after the end of the job.

Tunnel Boring, a personal account[edit]

Jim Hewett writes:

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 from the three tunnellers, those employed on the tunnel included Bunny Lewis, Norman Gurley, Martin Duncan and Dave Payne.

The new tunnel is 287 yards long. Breakthrough was achieved on 1st May 1976, and excavation was finished in 1977. It was officially opened on the 25th June 1977 for a special train, with regular services from 8 July, although work continued the following winter to "Shotcrete" the inside to stabilise the cracked rock.


Work to replace the ballast and track began early in January 2018 and was scheduled to be the focus for about two months. The new sleepers are made of recycled plastic which it is anticipated will last well in the wet environment. The tunnel is not only wet but the water is also acidic and rails and metal fittings corrode and waste rapidly. In 1994 it was reported that half the rails in the tunnel which were new in 1974 had been replaced.[2] The rails laid in 2018 are the third set including those for the opening so the life of rails in the tunnel is only about 20 years. The old ballast was taken by works trains to infill behind the new sea defences at Boston Lodge and new ballast was back-loaded in daily works trains planned to be the most intensive series since the days of building the Deviation.[3] Due to a shortage of working diesel locomotives many of the ballast trains were steam hauled with Linda, Blanche and Earl of Merioneth sharing the work.

New Tunnel Portals[edit]

It was always intended to replace the concrete portals with something more attractive. For many years there were always higher-proiority projects but eventually progress was to be made. After extensive searching suppliers in Portugal were contracted to supply ready-cut stones. By March 2018 new stone arches were being laid out by stonemasons. It was anticipated that they would be delivered to the railway by May.[4] The new portals were in the Minffordd Yard goods shed by September.[5]

Construction of the new stone tunnel portals began in November 2018, with the North end stone portal unveiled in March 2019 for the start of regular service.[6] The South end portal is more complicated as it incorporates a wing-wall and drainage channels. Groundworks were completed during 2019 and construction of the portal commenced during the 2019/2020 winter shutdown period. It was surrounded with scaffolding as construction moved forward. The scaffolding was removed after the railway was temporarily closed due to the Covid-19 outbreak. By this time, the new portal was largely completed, requiring only a few minor jobs to be completed. [7]

The old style concrete portal, as seen from the South end. Photo: Martin Ellis

See also[edit]


  1. ^ Ffestiniog Railway Magazine, Issue 71, page(s): 17
  2. ^ Ffestiniog Railway Magazine, Issue 144, page(s): 492
  3. ^ Inside Motion, December 2017
  4. ^ Post on Festrail Insider Facebook page, 12 March 2018
  5. ^ "Update on the guessing game", Inside Motion, 5 September 2018
  6. ^ Post on Festrail Insider Facebook page, 28 March 2019
  7. ^ Post on Ffestiniog and Welsh Highland Railways Insider Facebook page 2nd April 2019