Cwmbach Rail Bridge A470

The Cwmbach Bridge crosses the Central Wales line just North of Builth Road Junction, near Builth Wells. The structure comprised a three span bridge, with reinforced concrete abutments at each end and two centrally located reinforced concrete piers, the over deck was a structural steelwork concrete composite.

Client: Welsh Government
Location: Builth Wells
Date: 2010-2011
Value: Total Project £36m


The structure was designed as a Category 3 structure due to the proximity to the railway. The bridge was constructed over the railway line, during a series of arranged Network Rail T3 possessions at night and between trains under a T2T block possession during the day.

The contract required the client to set up the basic all party agreement (BAPA) with Network Rail, with resultant costs paid directly by the client.

As principal contractor Alun Griffiths (Contractors) Ltd. were charged with direct liaison with Network Rail when obtaining permissions and possessions to carry out the works in proximity to the railway infrastructure.

Meeting with Network Rail helped to establish the requirements that were needed to allow the works to proceed without any delay to the contract or disruption to the service provided by NR.

As an outside party the principal contractor was required to submit methods of work to NR for approval, and supplement any temporary works design with a form “C” Category 3 check.

A site clearance operation was carried out at the commencement of works, using a preferred sub-contractor that had operatives holding the sentinel PTS cards.

The Northern pier was piled in close proximity to the railway. Works were carried out with the railway fully operational after necessary measures were put in place to safe guard the rail infrastructure.
Prior to the piling works, during and after completion of the works, track monitoring was arranged and managed by the principal contractor using one of the NR approved companies.

Project Location