Interviews

Shaking the timbers

RTM speaks to Network Rail’s Rosie Majer and co-ordinator of the South West Wales Integrated Transport Consortium, Sue Miles, about the reconstruction of the Loughor viaduct and plans to re-double the singled section of the Swansea to Llanelli route. 

The dual-tracking of a six-mile stretch of railway in south west Wales, as part of a wider upgrade to boost capacity and cut journey times in the region, will also necessitate the complete replacement of the timber Loughor viaduct, which would be in danger of buckling under the weight of a modern twin-track railway.

The works as a whole will cost around £40m, split between the Welsh Assembly. Government and Network Rail, which is funding the viaduct works – vital if the improvements from dual-tracking the rest of the six miles are to be fully realised.

Rosie Majer, Network Rail scheme project manager in its Investment Projects Buildings and Civils team, said the works as a whole will increase the amount of services that can operate between Llanelli and Swansea.

She explained: “The Welsh Assembly Government has provided a business case to explain why they’re backing the works, as part of which a couple of structures are going to be strengthened.

“The main structure that needs to be changed is Loughor viaduct, which basically needs to be replaced. Currently it’s unable to support twin-tracks to the loading that we need to run the trains over them.”

160 years of service

The viaduct, built in 1852, carries the line across the tidal estuary of the River Loughor.

Majer explained: “It’s going to be a complete replacement – a new structure. We did a lot of studies on the existing one there, and because it’s wood and has had bits bolted it, engineering consultancy Cass Hayward, who did it first, said it just couldn’t be strong enough to support these two tracks. It was singled in the 1980s because it was buckling.”

She continued: “We looked at doing an off-line solution, which would have been cheaper for us, because we’re not able to shut the railway. However, because of the rail alignment, and the fact there’s a road really close on the north side, and the cost of putting in new embankments, it’s had to be an on-line solution.

“We’re looking at pilings either side of the existing structure, as close as we can get them to it, creating a sort of ‘goalpost’, putting in cross-heads, and then putting in some temporary piles alongside the existing structure. Then we’re going to build the new structure and launch it out adjacent to the existing one. We’ve got a rail closure in January 2013 when we’re going to be able to demolish the existing deck, and slide in the new deck, which will be adjacent, into position. That deck will have the track on it, ready to become the new structure.”

Benefits

A speed restriction is currently in force, with freight services only able to travel at 25mph, Majer said, which will be lifted once the new structure is in place.

She added: “That will be useful, but the main benefit is that the viaduct replacement allows the wider Welsh Assembly Government dual-tracking project to go ahead, and the benefits of that to be realised. The structure needed repair or replacement, but the reason we’re doing it now, and replacing it, is this other project.”

Conservation plans

The viaduct has 18 spans of about 12 metres (40 feet) each. It was originally entirely timber, but has been successively re-decked by wrought-iron and then steel plate girders, though parts of the substructure remain original, according to the Royal Commission. replaced by a fixed span during the nineteenth century. It is the only surviving timber viaduct designed by Brunel and Fletcher, according to the Commission.

Majer said: “It’s a Grade-II listed structure. It was thought the structure was Brunel, but we managed to prove that although the piles that went into the estuary were done in Brunel’s time, the wooden trestles that form the substructure had been replaced over the years. It’s listed now as an ‘example of a timber viaduct on a working railway’.

“We’ve put in our planning application now, and as part of that we’re proposing to leave two of the trestles in on the western side, and one on the eastern side, so people looking at the structure can see what would have been there before. We’re also planning to take two spans of the existing structure, with the trestles and the deck, and put up a little ‘monument’ on the western side, on Network Rail land. People will be able to pull into an existing lay-by and look at that.”

That idea came from a local authority conservation officer, as Network Rail has been keen to involve them in order to find out what the councils concerned considered acceptable in terms of heritage and conservation.

Priority project

Sue Miles, co-ordinator of SWWITCH (the South West Wales Integrated Transport Consortium), a formal alliance of the four unitary authorities in the region, told RTM that combining the dual-tracking plans with the Loughor viaduct replacement would cut both costs and disruption.

She explained: “SWWITCH has been working with the Welsh Government and Network Rail to secure the re-doubling of the rail line west of Swansea for sometime. The fact that the Loughor viaduct was due for replacement provided an ideal situation for a joint approach to the projects between Network Rail and the Assembly, thus reducing overall costs and disruption to passengers.

“The re-doubling of the line is a priority in the SWWITCH Regional Transport Plan 2010-2015 as it is seen as critical to increase the resilience of the current service – and thus fewer delays for passengers – and to enable improved levels of service to be introduced in the future to serve growth in passenger numbers.

“SWWITCH believes the work will make rail a more viable and attractive transport option in south west Wales and encourage more multi-modal journeys in the longer term.”

Improvements

Alongside the dual-tracking of the line between Cockett West Junction and Duffryn West Junction, which should allow two more trains an hour between Swansea and Llanelli, and one more an hour between Swansea and Carmarthen, there will also be station improvements at Gowerton. Network Rail promised a “bigger, accessible and secure” station with two platforms – following the reinstatement of the disused eastbound platform – as well as a new DDA-compliant footbridge with ramps, real-time customer information system, CCTV and better lighting.

The signalling and crossing infrastructure at Duffryn will be upgraded to handle the dual-track railway, and alongside the major viaduct works, smaller scale upgrades will also improve bridges at Traffle Mill, Gypsy Cross and Rhosog.

Mark Langman, route managing director for Network Rail Wales, said: “The scheme promises to bring huge social economic benefits in south west Wales by improving capacity and connectivity to key employment centres such as Swansea, Llanelli, Carmarthen, Fishguard and Milford Haven. There will be an improved passenger experience with shorter journey times and better connections that will also encourage modal shift, potentially removing around 300,000 trips from road to rail and improving the green credentials of rail."

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