Bridges
Bridges & Structures



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Pont Briwet Road and Rail Bridge replacement

Client: Gwynedd Council

Contractors Designers: Hewson

Form of Contract: ICE 5th with amendments

Dates work carried out: 2013 - 2015

Value: £16,450,000

HOCHTIEF completed the design and build Pont Briwet project, in Northern Wales, summer 2015. The scheme involved complex phasing for the demolition and replacement of the ageing timber rail and road viaduct. A critical element of this was to maintain public utilities throughout.

The new structures have a design life of 120 years; therefore they will require less maintenance than those which are being replaced. The carriageway over the structures has been widened to current standards and the footway widths increased providing better and safer access. The railway over the viaduct is carried on a separate deck, capable of an increased line speed and designed to current alignment standards.

The scope comprises:

  • 1km of bi-directional railway line
  • The replacement Bridge is constructed of 6 spans using reinforced concrete piles and piers, prestressed concrete bridge beams and a reinforced concrete deck.
  • Construction of footpaths, cycleways and a new two-car stop railway station.
  • Over 60,000t of imported stone comprising 6F2, 6I, Type 1 sub-base and drainage stone.
  • Over 10,000t of rock armour placed in a tidal environment.
  • Substantial environmental mitigation works in area of SSSI site.
  • Close working links with Natural Resources Wales to model river flows at design stage in both permanent and temporary state to ensure erosion of adjacent saltmarsh is mitigated.

Key relevant features

  • The project required an extremely high level of stakeholder management due to the geographical area, liaising with such parties as Natural Resource Wales, Network Rail, National Grid, Welsh Government Officials, Gwynedd Archaeological Trust, County and Community Councillors, local residents and business holders.
  • Currently going through CEEQUAL assessment process, with the expectation of scoring an ‘excellent’ rating.
  • Working closely with statutory undertakers to ensure supplies of high pressure water mains, high voltage electric and fibre optic maintained throughout the project.
  • As an integrated team working in collaboration with the client and supply chain we were able to ensure that 70% of staff and work force were employed from the local community.
  • In its first year the project secured a high ‘considerate constructors’ score.
  • Community benefits schemes supported design of two children’s playgrounds in the villages of Penrhyndeudreath and Talsarnau.
  • 20, 000 Tonne of material used to create two causeways to access the bridge during the project has been re-used on a local development.



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