Phase 4: Rhyd Ddu to Porthmadog

The Aberglaslyn Pass and Tunnels

Phase 4 pages:
Beddgelert: Bridges & Station
Aberglaslyn Pass & Tunnels

Recent updates are underlined and in red.

Click for a map of the Phase 4 route in a separate window.

The route section of the site includes detailed illustrated descriptions - Rhyd Ddu to Beddgelert and Beddgelert to Porthmadog.

The Aberglaslyn Pass is the most famous section of the WHR - and in terms of the restoration of the line, it has also been the most controversial. The line runs along and above the eastern bank of the Afon Glaslyn; the railway may appear to climb away from the river but in fact the river drops away from the railway, which is itself on a falling grade heading south, as the gorge narrows towards its southern end at Pont Aberglaslyn. Before this point the railway turns away eastwards through the longest of its four tunnels (T4 in construction terminology), after two very short tunnels in the Pass (T2 and T3). T4 brings the line out into Cwm Bychan, site of the former Aberglaslyn Halt.

The most significant tasks were done here back in the winter of 2000-1. This was because the Transport and Works Order authorising the reconstruction of the line included a clause making the rebuilding of the line through the Snowdonia National Park dependent on satisfactory stabilisation of rock faces at Aberglaslyn. The main job was increasing the height of the large retaining wall between T3 and T4. Other works included a smaller enlargement to the wall north of T2, and some rockbolting and shotcreting in and around two of the tunnels, T4 in particular. These works were approved by the Snowdonia National Park Authority in April 2001. More details of these works can be found on the Phase 3 Aberglaslyn page.

Developments between then and Phase 4 rebuilding were mostly to do with relocating other closure-period uses of the trackbed in the Pass.


With the impending final loss of the trackbed to walkers there was considerable upgrading of the Fisherman's Path, below the trackbed by the water's edge. This is now accessible to far more walkers than before, after sympathetic improvements to previously precarious sections, and the addition of a gravel surface at the northern end near Bryn y Felin; other sections are stone paved. It provides a through route to Pont Aberglaslyn, as well as giving easy access to the many visitors for whom the Pass itself is the destination. The work was done under the auspices of the Snowdonia Upland Path Partnership.

Water Main

The other significant job was the replacement of the water main that had run alongside the trackbed. Dwr Cymru/Welsh Water made good on the undertaking made to the Official Receiver when the main was installed, that the water authority would relocate it at its own expense if the railway was ever rebuilt. This also applied to the much larger water main which had been placed under the trackbed at Bryn Gloch, which was moved in 2001. Work on replacement of the Aberglaslyn main started in Summer 2006, with trenching work for the new main across National Trust land near Bryn y Felin.

The old main ran along the east side of the trackbed, underground for the most part, but above ground and encased in concrete through the tunnels and at a few other points.

The new main crosses beneath the trackbed between the road and river bridges at Bryn y Felin, and its route then moves up to run along the eastern edge of the road. With contractors working from a base in the layby in the Pass, the trench for the main was started in mid-October 2006, with a first section of road controlled by traffic lights starting immediately south of the road bridge, followed soon after by another towards the south end of the Pass; these sections were moved towards each other as work progressed. In addition, the short narrow and winding section of the A4085 from Pont Aberglaslyn to Nantmor was closed between November 6th and December 22nd, for the water main works and also telecommunications work. The water main works affecting the roads were completed in mid-January 2007, and the last short traffic control at Pont Aberglaslyn was removed.

Trackbed and Fencing

Having been in use as a footpath - albeit relatively rough-surfaced in places - the trackbed through Aberglaslyn was in excellent condition compared to most sections of the derelict trackbed. It did not appear to suffer from any drainage problems, but there were a number of culverts such as the "rustic" slab-built one in the first picture below which required renewal.

The trackbed was previously obstructed between the short tunnels by a base for a WW2 "Blacker Bombard" mortar launcher, identical to the one at Plas y Nant. This has been relocated alongside the trackbed.

The black steel fence posts visible in various pictures were chosen for their unobtrusiveness, and in some places replaced earlier lighter fencing which had suffered vandalism. The fencing wire was being installed in September 2006, as seen below immediately south of Bryn y Felin bridge, together with a new steel gate of matching appearance.

The Tunnels

As explained above, the major work required on the tunnels was done in 2000-1.

T2 (29m)

T2 is the construction sequence number for the first Aberglaslyn tunnel; T1 is the short tunnel immediately south of Beddgelert. This tunnel runs through a rocky outcrop which continues down to the river. Like all the WHR tunnels it was cut with a rough rock interior surface, unlined. The 2000-1 work involved shotcreting (spraying of liquid concrete) parts of the roof.

T3 (9m)

This very short tunnel - not much more than twice as long as it is high - pierces a smaller outcrop. It required more work than T2 in 2000-1, with shotcrete now reinforcing much of the roof, and rock bolting also done where necessary.

The large retaining wall between T3 and T4 was one of the main focuses of the 2000-1 works, during which its height was increased; the new section is still clearly visible, but is weathering in year by year. This traditional style wall masks a massive 1920s concrete retaining structure behind it.

T4 (280m)

By far the longest of the tunnels, T4 includes a curve so that one end cannot be seen from the other, and is one of the WHR's main engineering features. 2000-1 repairs included shotcreting and rock bolting where necessary. At its southern end, the tunnel emerges into Cwm Bychan via a rock cutting.

Trackbed Contract

The contract for trackbed refurbishment to ballasted condition ready for tracklaying was let in February 2007 to G.H. James Cyf. This contract covered the section from Bryn y Felin to Nantmor village.

James moved on site in the week beginning April 16th 2007, working from a compound at Bryn y Felin, with the earthworks proper starting on April 23rd. As part of the setting out works, survey posts were put in place southwards from Bryn y Felin into the Pass.

The trackbed north of the tunnels includes a number of culverts and creeps which needed attention; some of them are at significant depth below track level, increasingly so going south towards T2. The stone construction suggests these may date back to PB&SSR work in the 1900s.

Work got off to a fast start, with grading and hardening of the trackbed running south from Bryn y Felin, including removal of the water main from the eastern side of this section, and a start on its replacement with drainage.

At the south end of this stretch significant embankment repair earthworks were put in hand to the north of the rock cutting leading to T2. At the southern end of this repair the trackbed was excavated down to one of the rectangular culverts, revealing a rough slab roof, with gaps.

The first picture below shows work in hand on May 4th 2007 to re-roof this culvert; the second illustrates prepared trackbed further north, looking towards Bryn y Felin.

The repair site is seen on May 10th 2007, with the formation being made back up. The blue pipes were remnants of the old Nantmor water main.

The pictures below were taken further north on May 15th 2007 and show (left) the headwall on the eastern side of one of the smaller culverts, and (right) drainage work on the eastern side of the trackbed.

On May 25th 2007 work was in progress close to Bryn y Felin (left-hand and middle pictures), and the trackbed approaching T2 had been remade.

At the start of June 2007 work was advanced on the "rustic slab" culvert noted earlier on this page, at the south end of the PB&SSR-built retaining wall just south of Bryn y Felin.

A little further south, culvert UB175 is seen below left on June 7th 2007, with formwork and mesh in place for the deck slab which was cast the same day. The right-hand picture shows trackbed at CH24100, one of the sections that was almost ready for ballasting.

It was recognised that the formation immediately south of Bryn y Felin could be vulnerable to the river in extreme flood conditions, and in light of this a pair of additional flood channels were provided, designated UB174A; they are seen below approaching completion on June 28th 2007.

On the same date, the laying of sub-base northwards had reached the point seen in the left-hand picture below, a short distance south of the new channels.

Laying of ballast northwards from near T2 towards Bryn y Felin started on July 4th 2007; as usual, bundles of sleepers were deposited on or near the new ballast bed as the contractors worked back towards their access point.

By July 12th 2007 ballast was on the approach to Bryn y Felin bridge. James then turned to work on the downstream wing wall before ballasting right up to the bridge itself.

The pictures below show custom track fittings for use on wooden sleepered track - new track screws supplied by Holdtrade (UK) Ltd, Llantrisant (which were in stock at Dinas by mid-July 2007), and new sample track base plates from Majorfax Ltd of Walsall. The plates (approximately 200mm x 150mm) are used on track laid onto wooden sleepers, between the rail and the sleeper, with screws through two of the four holes, securing the rail; 5,000 of these plates were on order in July 2007, enough (together with 10,000 screws) to complete the sections of Phase 4 due to use wooden sleepers.

The views below show ballasted trackbed at the end of July 2007, at which point James had almost finished ballasting southwards to the mouth of T4, working from the Nantmor end. The last section of the water main had been removed from the foot of the T3-T4 retaining wall.

Work on the Tunnels

In the second week of May 2007, access was gained from the Nantmor end for a check on clearances in the three Aberglaslyn tunnels. A structure gauge was fixed to a dumper, which travelled through the tunnels from Cwm Bychan to the north end of T2. The gauge got through all three tunnels without problems, but it was found that in places, clearances were closer than traditionally stated. The survey established how much of the existing fill needed to be remove from the tunnel floor; this fill was then replaced with a thin layer of sub-base, to give the floor the standard 1 in 20 crossfall to shed water into a drain on the western side, before the ballast bed was added.

These pictures inside T4 show lighting strung along the sides of the bore, and a refuge.

Within days, work started on removing the old water main from T4, to aid clearances; the main through the tunnel had been encased in concrete above ground level. The blue water pipe is visible below, being broken out from the concrete. The off-white fragments in the picture were what remained of the polystyrene frost protection wrapper surrounding the pipe. The concrete pipe surround had been broken out through the full length of the tunnel by May 16th 2007.

Within a week the water main had been entirely removed from the tunnel.

The scenes below show the stretch between T3 and T4 on May 31st 2007, with the water main still in place at the foot of the retaining wall.

The main had been removed from T2 when seen on June 7th 2007 (right-hand picture).

On July 6th 2007, T2 is seen (left) with the centre line marked out, while finishing works were being carried out between T3 and T4 (right).

Meanwhile contractors were at work inside T4, clearing material from the tunnel floor.

The lowering of the floor was complete by the end of July 2007. The portable fans visible in the third and fourth pictures had been brought in for ventilation purposes during reconstruction.

Clearances were checked in T3 on August 3rd 2007. The gauge is resting on pieces of wood simulating the rail height, and the yellow paint shows the track centre line. There was adequate clearance here but the dimensions were tight, comparable to T1.

This view north from T4 on August 10th 2007 shows the ballast at the tunnel mouth; G.H. James Cyf started ballasting through the tunnel shortly afterwards.

The ballast bed and sleeper bundles had almost reached the southern portal by August 20th 2007.


Tracklaying pressed onwards from Bryn y Felin into the section covered by this page over the August 2007 Bank Holiday weekend, with the working party extended into Monday.

One more length was laid during the September 1st-2nd 2007 working party, after completion of the loop at Beddgelert.

Unusually, track was laid on a Friday on September 7th 2007. The day was an additional day's track laying to the usual weekend programme and was arranged as a Team Building event for members of the Building Projects Division of Imperial College Support Services. Fourteen members from the Building Projects Team joined members of the Rest of the World Gang, and apart from two, were laying WHR(C) track for the first time.

The Rest of the World Gang pressed on further over the next two days. The first picture shows newly laid top ballast just south of Bryn y Felin, put in place by the hopper wagons.

A visiting Territorial Army group then continued the tracklaying during the week; at the end of work on September 11th 2007 the Head of Steel had edged closer to the tunnels.

By the end of the next day it was at roughly CH24050, just short of the large culvert UB167 in the area where the embankment was remade in April-May 2007. The second picture on the lower row shows the transition from wood to steel sleepers; it had been decided that the track through the tunnels would in fact be laid on steel, to maximise vertical clearances, and this proved a convenient spot to make the transition on a straight.

The following pictures were taken on September 13th 2007.

And by the close of tracklaying on the 14th, the Head of Steel was on the approach to T2.

The Black Hand Gang were laying track just north of the tunnel when pictured on the 15th. By the end of the following day the Head of Steel had passed through T2 and was just short of T3.

As a postscript to the above, Dolgarrog ran out of fuel just short of Beddgelert at the end of the working party on the 16th, and refused to start even with ten litres of emergency diesel added, and so was towed back to Rhyd Ddu by Upnor Castle at 10mph.

The Territorial Army took the Head of Steel on through T3 (which has an awkward curve) in the following days. The third picture shows Conway Castle with a test train comprising carriages 23, 24 and 1001.

The Rest of the World Gang laid the first track in T4 on September 22nd 2007. The first picture illustrates the curvature at T3.

These pictures were taken on the 23rd. The last section of the tunnel had not yet been ballasted ready for track to emerge into Cwm Bychan.

The Head of Steel advanced to 10 metres short of the southern portal over the weekend of September 29-30th; beforehand, the ballast base in the tunnel had been completed and extended some 10m into the cutting beyond.

The "Finished Product"

Well - not quite yet, but these pictures taken on October 6th 2007, the same day track emerged from T4 into the next section, show that the most famous views of the WHR in the landscape were well and truly back with us.

The interior of T4 is seen below from works carriage no. 1001 in July 2008.

Back to WHR Project homepage or the opening Phase 4 page
Maintained by Ben Fisher; last updated July 28th, 2008