Network Rail’s £30million refurbishment of Barmouth bridge on the Cambrian Line in West Wales is now complete, it reopened on 2nd December 2023. The work has been some of the most challenging ever undertaken on the bridge, replacing the steel spans with like for like new steelwork. The 154 year old, Grade II* listed single track structure is the oldest and longest timber viaduct in Wales, at 820m (900 yards) long, with a pedestrian and cycle pathway alongside the railway.
It runs across the Mawddach Estuary between Morfa Mawddach and Barmouth stations and was designed and constructed by the Aberystwyth and Welsh Coast Railway on its line between Aberystwyth and Pwllheli.
Construction started in 1864, it opened in October 1867. The line had already been absorbed into the Cambrian Railways in 1866. A drawbridge was included when it was built to allow the passage of tall ships up the Afon Mawddach, which got replaced by a manually turned swing bridge in 1899.
Severe corrosion was found in the underwater ironwork in 1899 and it took until 1902 to finish repair work. In 1980 marine woodworm (Teredo navalis) caused serious damage to the piles, there were concerns it could be closed and demolished. Local councils did research and found about 40% of the tourism in the Cardigan Bay area was rail related, and it was an important transport link, so a reprieve was won and it underwent extensive repair during 1985 and 1986. Greenheart hardwood was used to replace 48 of the piles, with 330 other strengthened in glass-reinforced concrete jackets. Greenheart is a sustainably sourced tropical hardwood known for its resistance to rot and most insect attacks. Other upgrades at the time included signalling, track renewals and installing automatic level crossings, at a cost of £4.5m.
The swing bridge was last used operationally in the 1960’s and a final test opening took place in 1987. Continuous welded rails have since been laid across the bridge and the estuary is now heavily silted, so only small boats can navigate upriver. After the end of the 1980’s restoration the structure was awarded a Grade II* listing.
The footbridge alongside the line is part of the Network Rail structure, but Gwynedd County Council have a licence to use it, paying a contribution of 10% of the annual cost of maintaining the Bridge, currently around £30,000 per annum. The toll house was operated by the council until 2013, but was replaced by an honesty box with a suggested £1 toll.
Plans were initially drawn up in 2013 for the restoration. The project details were released in May 2020, after discussions with CADW (Welsh historic monuments organisation) in regard to safeguarding the listed components. Initial plans looked at repairing and replating the steelwork, but investigation showed that replacement was the only feasible option, so new identical components were manufactured
Work on site started in 2020, split into several phases over three years to minimise impact on rail services and the local community. The timber work was restored during the first two phases and the final, and largest phase, was replacement of the steel spans and renewal of track at the northern end. The location makes the project a lot more complex, with limited space available near the bridge. Four sites across Barmouth were used to enable the works.
Further complications with the location include a 33,000 volt electric cable running across the estuary, its exact location is unknown, preventing the use of shear legs to lift the spans directly into position. The estuary has a tidal range between 3 and 5 metres, and a very strong current, with tidal streams of up to 6 knots flow. To allow pontoons to be positioned under the bridge, additional moorings were sunk into the estuary.
The new spans arrived in sections by road south of the estuary and the task of moving them was tested on a temporary track section before being moved along the bridge on rail trolleys at the start of September. Arriving on site directly inside the old spans they were secured to temporary supports on the bridge piers with a gantry system installed on top. Two travelling hoists, custom built for the project were lifted onto the gantry.
The old spans were cut into sections weighing around twenty tonnes, then lowered onto powered pontoons in the estuary below and removed to the beach for cutting up.
The complexity of deconstruction, along with the difficult working environment meant that just two sections per day were removed from the structure at slack high tide. The weather conditions also caused delays, with several days downtime for Storm Agnes and other inclement weather that prevented safe working.
After the old sections were removed, the new spans were jacked out to their final position, then new underbridge sections were lifted into position from pontoons floating underneath.
Although the main work is complete, the process of clearing the worksites will take several months, as it includes a temporary concrete base with a length of track, used for testing the process of moving the bridge spans
Despite the extensive restoration, the bridge’s long lateral structure gives it limited stability, meaning that maximum speeds of 20 mph (32 km/h) for passenger trains and 10 mph (16 km/h) for freight will remain in place.
Whilst the possession was in place between Dovey Junction and Pwllheli other work was carried out along the route on several viaducts, and track renewal at Felga Fach and Pwllheli Stations.
The projects are part of a wider multi-million pound investment on the Cambrian Line, that also incorporates track work, drainage improvements and station refurbishments, safeguarding the route, described by many people as one of the most scenic in the UK, for many years to come.
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