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Pont Briwet: Replaced

Pont Briwet viaduct in Penrhydeudraeth, North Wales

Pont Briwet viaduct in Penrhydeudraeth, North Wales

A project designed to replace Pont Briwet viaduct in Penrhydeudraeth, North Wales, continues to make great progress.

The £20 million scheme began in April 2013 and sees the former Grade II Listed timber viaduct – which crosses the River Dwyryd – replaced with a new, more suitable and durable concrete structure.

The former viaduct –originally constructed in 1860 – comprised a single railway track, which ran from Dovey Junction to Pwllheli, and a single toll road. The speed limit for rail traffic was set at 20mph, whilst a two ton weight limit was imposed on all highway traffic.

Heavier and larger vehicles were not permitted to use the former viaduct and as a result had to travel an eight-mile detour in order to undertake a journey from Penrhydeudraeth to the Harlech road. The imposed weight limit on the existing rail and road routes, as well as the narrow width of the road, also restricted the level of road traffic permitted to use the viaduct.

With a service life of more than 150 years the crossing has proved invaluable for the local community; however it had reached the end of its life and was certainly in need of improving beyond simple repairs. The viaduct replacement project – which is being implemented by Gwynedd Council – will now breathe new life into this crossing, providing welcome relief for road and rail users and a safe crossing for the next 120 years.

Gwynedd Council are overseeing the project which is being part funded by the European Regional Development Fund, through the Welsh Government, who are contributing over £9m to the project. Network Rail are also providing significant funding as is the Welsh Government who have made a substantial contribution of approximately £5 million via the Mid Wales Regional Transport Consortium. All of these funding avenues have allowed for a full replacement of the existing structure rather than continuation of repairs.

Pont Briwet viaduct in Penrhydeudraeth, North Wales

HOCHTIEF (UK) CONSTRUCTION is the main contractor on the project, whilst Hewson Consulting Engineers are the project’s lead designer. HOCHTIEF is a leading international construction company with a vast portfolio of projects, whilst Hewson delivers innovative bridge and civil structural design and construction engineering solutions throughout the world.

Hewson has worked with HOCHTIEF (UK) CONSTRUCTION throughout the entirety of the scheme and were appointed during the tender process. HOCHTIEF (UK) CONSTRUCTION could see there were opportunities to undertake value engineering on the scheme and as Hewson specialise in bridge works were selected by HOCHTIEF (UK) CONSTRUCTION to undertake the design.

Keen to find out more about the Pont Briwet project, Rail Construction News recently caught up with HOCHTIEF (UK) CONSTRUCTION Business Development Director, Graham Parker and Hewson Company Director, Andrew Hodgkinson to get the lowdown on Pont Briwet. Graham and Andrew explained the importance of the project and updated Rail Construction News on the project’s progress.

Graham said:

“The brief we were given for this project was to design and build a new structure which could replace the existing timber viaduct at Pont Briwet. We qualified for the project via Gwynedd Council, but before this we had actually been working with Network Rail on the scheme, who remain as one of the stakeholders in the project.”

Addressing the existing state of the viaduct was the team’s first objective; taking it from what it was to what it truly could be. A key issue was looking at the viaduct’s existing capacity and improving it for road users.

Andrew said:

“Before work began the viaduct was in a very poor state and was in need of regular maintenance. The timber was old and it had reached the end of its life. The toll road was just a single carriageway, controlled by traffic lights, was very narrow and had a 2 ton weight restriction. This was no longer viable for projected traffic use so this project provides a much faster, safer and more direct, two-way, unrestricted crossing.”

Pont Briwet viaduct in Penrhydeudraeth, North Wales

The new structure will be 18 meters in width, rather than the previous 8.5 meters, and will provide a two-lane public highway, a combined cycle route and pedestrian path. Work on the project was divided into two phases and the site’s railway line was reopened to the public on 1st September.

Andrew commented:

“The project is essentially being completed in two phases and this is due to the need to work around the existing viaduct. At present the section of viaduct supporting the railway has been completed, along with all associated railway and highway works and things are coming along as we would expect at this stage.”

Benefits of the new viaduct include better transport links for heavier vehicles – including ambulances, coaches and lorries – as well as no toll charges. In addition, the cycle path and footpaths will link up with the National Coastal Path and the Welsh National Cycle Route 8.

Despite the success of the project so far, the work has not been without its challenges. Working on such a key transport route which includes rail and road networks is demanding in itself, but this project also includes many specialist elements of construction work all to be undertaken within a relatively small site area with limited access.

Pont Briwet viaduct in Penrhydeudraeth, North Wales

Andrew explained:

“Working on a scheme with so many disciplines has presented a few challenges. The viaduct is the centre-piece, but we also have to factor in the highway works, permanent way, major embankments, coastal revetment works, rock cutting and more. All of these works are taking place within an environmentally sensitive estuary, so coming up with a scheme which protects this environment was of paramount importance.”

Graham agreed with Andrew, explaining that protecting the marine life from the ongoing works was extremely important.

Whilst work takes place on the project, every effort is being made to minimise disruption to the public. Sometimes it has been necessary to carry out works during unsocial hours, including overnight and during weekends on critical elements of the works, but this has been kept to a minimum with work being carefully planned. Site working hours normally run from 7.00am to 7.00pm Monday to Friday and 07.00am to 2.00pm on Saturdays, dependent on weather.

With work continuing on the project, Graham and Andrew reflect on the importance of the scheme.

Graham said:

“At HOCHTIEF (UK) CONSTRUCTION we specialise in major structures and infrastructure works and this project demonstrates the high level of technical works that we can deliver. This is very much a key, challenging project for us, but one which we have enjoyed being a part of. The project gives continuity of work to our team and is also an important project for the local area.”

Pont Briwet viaduct in Penrhydeudraeth, North Wales

Andrew added:

“This is an extremely important project for Hewson which demonstrates our ideas in practice. The work we have done here showcases the creative ideas and value engineering that we offer to contractors and clients.”

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