Engineering the Welsh Highland Railway re-build

Engineering the Welsh Highland Railway re-build

15 Aug 2008

Few railway re-instatement projects have captured the imagination more than the Welsh Highland Railway. The origins of this narrow gauge line date back to the 19th century, but it was not completed as a through route between Porthmadog and Dinas (near to Caernarfon) until 1922. It had a chequered history in the ensuing economic climate and mass tourism was not then in sway, at least to the remoter parts of the British Isles. It struggled on through the depression years but closure came in 1939 with much of the infrastructure being ripped up to help the war scrap effort.

Running through spectacular scenery near the south slopes of Snowdon, plans to rebuild the line have been around since the early 1960s. Little progress was made as the task was huge and the amount of money required was colossal. There was also a legal tangle to rescue the line from receivership as it had never been formally abandoned.

The preservation movement in those days was still in its infancy and the rules of the game were not properly understood. The adjacent Ffestiniog Railway was however up and running and this was to prove significant later on. The original Welsh Highland preservation society did eventually manage to build a short spur line from close to Porthmadog main line station to Pen-y-Mount, a distance of about a mile and ran a shuttle train service with both steam and diesel traction. Welcome as this was, it was a mere pin prick in the grander intention to reinstate the whole line.

The Ffestiniog Railway, having restored its line to Blaenau Ffestiniog in the 1980s, was looking for a new challenge and foresaw the opportunity of the Welsh Highland to complement its existing operation and create a narrow gauge transport hub based around Porthmadog. The FR could bring much greater resources and skills to the task than the incumbent society but a certain amount of resentment was caused by this effective takeover. After a protracted period of acrimony, agreement as to how the project would progress was reached and the necessary fund raising effort was started. There are a growing number of articles written on the WHR and there will be many more to describe the line’s full opening in 2009, but this present contribution focuses on the engineering aspects of the project and some of the unique hurdles that have had to be overcome.

The Route described and funding the work

The line will eventually be 25 miles long. Starting in Caernarfon, the first three miles are on the trackbed of the old BR Bangor – Afon Wen line that closed in the 1960s. After Dinas, the line swings onto the Welsh Highland route proper and proceeds via Waunfawr and Rhyd Ddu to Beddgelert, the principal intermediate station. Thereafter it goes through the Aberglaslyn pass to Nantmor and through the town of Porthmadog to Harbour station where it will join end on with the Ffestiniog Railway.

The line has been opened in stages firstly to Dinas (1997), Waunfawr (1999) and currently terminates at Rhyd Ddu (2002). Phase 4 to Porthmadog is by far the biggest and most of the construction work is now complete.

The task has been to construct a virtually new railway. The cost of the completed project will be in the order of £25m, a huge sum in rail preservation circles. A good start was made with £5m coming from the Millennium Commission and £5m from the Welsh Assembly, both bodies having the vision to see the potential for the area. However, the project would have stalled had it not been for generous support from private sponsors, public subscription and a massive input of volunteer labour and expertise. An increasing revenue stream comes from the train service now in operation.

Civil Engineering

The rebuilding of the WHR has been possible because it was never formally abandoned and the formation was largely intact with many of the bridges still in place. That being said, none of it was in particularly good condition - hardly surprising after 70 years of disuse. There existed seven bow-string girder bridges dating from the 1890s - some beyond economical repair. The Glanyrafon lattice girder viaduct near Rhyd Ddu was refurbished, but that at Bettws Garmon was replaced using a redundant structure from near Rotherham.

Almost all the bridges on Phase 4 needed replacing – some of 40 metre span – and were supplied by a local firm at reasonable cost. The bridge over the Aberglaslyn river has proved a challenge as this needed to be combined with a replacement road bridge at Brynyfelin provided by Gwyneth County Council. A temporary level crossing has been needed whilst the work is carried out. A rail bridge over the A4085 at Nantmor had to be replaced. This was a major undertaking, and the bridge was supplied by the same local firm.

At Pont Croesor, the old bridge had long been dismantled but the piers remained and these have been re-fettled to allow a new girder bridge to be installed. Outside Beddgelert station, the bridge over the road at Pont Alyn has been rebuilt in concrete. One side wall has been retained, but it is intended to clad the other concrete wall with local stone to blend in better. Elsewhere, retaining walls have been built from slate block, an attractive natural material that has the resilience to protect against weather and potential slips.

The line has four tunnels, one at Beddgelert and three in the Aberglaslyn pass including a long one. To accommodate the new rolling stock, the floor needed to be lowered in the long tunnel and some shotcreting has been done to stabilise the rock. Some embankments were found to be too narrow and these have been cleared and widened. One needed considerable remedial work to make it fit for purpose.

The years of closure have also meant the degradation of cuttings. At Cae’r Gors between Rhyd Ddu and Beddgelert, the cutting has had to be cleared of all of the material that had slipped in, but the banks still show a tendency to be unstable and may need more stabilising work. In another area, considerable work was necessary to remove quantities of rock and in all cases, major work has been carried out to remedy failed drainage systems.

The track and its components

With a gauge of 597mm, what track to use and where to get the rails was a fundamental question. Rail has been obtained both new and second-hand from a variety of sources, primarily South Africa and Poland. Flat bottomed 60lb rail is preferred. Steel sleepers were acquired from South Africa and thence from India. Pandrol clips come also from India, with a bit of a quality control problem having to be put right along the way.

Steel sleepers need a good track bed as the curved profile makes them difficult to move afterwards and thus much effort has been expended in getting the formation right with good drainage. Ballast has come from the local Minffordd quarry, thus augmenting the policy of sourcing materials and labour from the local neighbourhood wherever possible.

Wooden sleepers are used where a traditional appearance is important or where noise levels are sensitive. Rails are in 18m lengths and joints are non aligned on curves. Track laying is all being done by volunteers. The railway has its own tamper/liner and has built a ballast regulator. Otherwise, it has to rely on power driven hand tools such as Kango hammers.

Crossing the Cambrian

As with the original line, the new railway has to cross the Cambrian Line on the level, where a new flat crossing has been installed. This represents a triumph of co-operation with Network Rail, giving strength to the old adage – where there is a will, there is a way. The crossing is manganese using 113lb rail. The standard gauge section is continuous with notches cut out for the narrow gauge passage. It is a continuous lump of metal with block joints to all four rail connections. A transition section using 80lb rail connects the crossing to the narrow gauge lines either side.

Access to Porthmadog

The railway has to run through urban areas of the town to reach Harbour Station, which involves some street running. To do this, the railway becomes a tramway where the rules of construction and operation are different. Grooved tramway rail has been obtained from Austria and is set into a reinforced concrete base inside a flexible boot. Minor changes to the original route have been made to ensure that the route impinges on the A487 trunk road as little as possible and also to accommodate the new rolling stock.

Remedial under pinning of the buttress near to the river and dealing with contaminated land on the former gas works site has had to be tackled. The crossing of the A487 over the Britannia Bridge to join up with the Ffestiniog line uses a conventional tramway crossing with rails set in the road on a concrete formation. Flashing lights of the AOCL variety will protect this and other road crossings in the town when trains are passing.


The main stations are at Caernarfon, Dinas, Waunfawr, Rhyd Ddu, Beddgelert and Porthmadog, the latter using the FR station by a reverse in move at least for the time being. At the other locations, substantial platforms have been built with passing loops and waiting rooms/shelters. Beddgelert station is on a 1 in 40 gradient, which is causing an operational rules challenge for any train that terminates there with the engine needing to run round. Elsewhere on the route, six halts with basic platform are/will be established, passengers joining or leaving the train from near ground level in true narrow gauge fashion.


Signalling will be by electric token throughout and will be worked on a staff and ticket system. There is no dedicated radio system but train crew will have public network mobiles to communicate in an emergency.

Crossing the Cambrian needs special arrangements, with the main line being at the western end of the Harlech – Porthmadog section controlled by RETB from Machynlleth. The flat crossing is situated between two road level crossings on the Cambrian line. The WHR are required to staff its crossing and all trains must stop. Contact will be made with the signaller at Machynlleth by pressing a plunger and if the line is clear, a signal will allow the WHR train to proceed. Signals protect the road level crossings and thus these are used to protect main line trains approaching the WHR crossing as well. Track circuit sequences on the main line will give clearance to both road and rail crossings once a train is passed.

Trains, rolling stock and service

Much has been written already about the ex-South African Garratts that form the core of the engine fleet. There are four of these, two in service, one being overhauled and one a kit of parts. In addition, there is the original Garratt from Tasmania (K1) and a 2-8-2 from South Africa awaiting restoration. Two diesels complete the traction scene, with one being large enough to haul off peak trains and to act as a stand-by locomotive. New coaches have been built, slightly wider than the Ffestiniog coaches as the loading gauge is bigger. The additional 6 inches both in width and height offer a superior travelling environment compared with the Ffestiniog.

The civil works should be completed and the line finished in an engineering sense by August 08 with the full line due to be opened by August 09. The train service pattern has yet to be finalised but is likely to be four return journeys each day depending on season with an additional Porthmadog – Beddgelert turn-back working. The project has done much to stimulate the local economy and will bring employment prospects to local young men and women. Truly a miracle about to be realised.

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