Crickhowell Bridge is a 17th Century, Grade 1 Listed, multi-span masonry arch structure carrying the A4079 Principal Road over the River Usk in the Town of Crickhowell. The road above the structure is a single 3.2m wide carriageway with a footway to the upstream side approx 1.7m in width. Permanent single working traffic lights are in 24 hour operation at the bridge.
Following a survey carried out by Kaymac, it was identified that scour protection repairs were required to protect the piers of the structure. Kaymac Marine & Civil Engineering were commissioned by Powys CC to carry out these repairs.
The scour protection was required in various isolated areas throughout the masonry invert. The masonry to the invert has been washed out completely, resulting in large voids up to 1.2m deep (from water level).
As the works involved disturbing the existing bed material and pumping concrete into the watercourse, there was a danger of harming the surrounding environment. Kaymac worked closely with the Environment Agency to plan the works to ensure minimal impact on the environment. The works were carried out in stages, diverting the flow through surrounding spans using a temporary sand bag bund as required. This enabled the works to be carried out in relatively dry conditions.
Once installed and the working area had been de-watered, the excavation works began to remove the bed material to the formation level. Once removed, concrete with an underwater additive was pumped into the voids and then masonry sets embedded into the top layer in accordance with CADW requirements.
Together with the scour protection works, removal of vegetation, re-pointing and various masonry repairs works were carried out by Kaymac.