RIVER ITHON BRIDGE A470 Cwmbach to Newbridge-on-Wye Client
Welsh Government
Location
Builth Wells
Date
2010-2011
Value
Project £36m
The £36m scheme comprised the construction of 6km of single carriageway between Cwmbach & Newbridge-on-Wye on the A470 trunk road, incorporating three significant structures over the existing A470, River Ithon and Central Wales rail link. Nine multiplate arch culverts were provided as mammal underpasses.
Ithon Bridge The Ithon Bridge crosses the River Ithon just South of Newbridge-on-Wye, near Builth Wells. The structure comprises an 85m two span bridge, with reinforced concrete abutments at each end and one centrally located reinforced concrete pier. The over deck comprises a structural steelwork concrete composite construction.
The River Ithon is a designated Special Area of Conservation (SAC) being a tributary of the River Wye, which is located 1 mile downstream.
The north abutment and pier were constructed within a flood plain and
Alun Griffiths (Contractors) Ltd Waterways House · Llanfoist · Abergavenny · Monmouthshire · NP7 9LN Tel. 01873 857211 · Fax. 01873 857679 Email [email protected] · www.alungriffiths.co.uk
were founded upon the bed rock, which leant itself to the design of the spread foundations, minimising excavation depths and over dig. On the south side of the river the existing topography meant that to construct a conventional abutment would have required considerable excavation and increased safety and environmental risks. In conjunction with our designers the abutment was designed to be reversed, bringing works closer to the river and having the effect of minimising the excavation depth and extent.
With such environmentally sensitive conditions the works were very carefully planned and close co-ordination between all concerned parties ensured the bridge was successfully completed without incident.
The bridge deck used “Omnia” permanent formwork reducing the need for temporary works underneath the deck and over the River. The Omnia units were sealed prior to placing the concrete which avoided any risk of grout loss into the water or onto the ground below.
The remainder of the bridge used conventional construction methods for the parapets, waterproofing, surfacing and drainage elements. Careful consideration was given to the chemical composition of the construction materials used to avoid any which may prove harmful to the surrounding environment.