A history of problems with the 200 year old, four span arch Brynich aqueduct on the Monmouthshire & Brecon canal led British Waterways to seek advice from Mouchel. This appointment followed the award of a 270 bridge assessment contract which BW had made to the firm in the light of its research on the behaviour of arch bridges.
A programme of investigative work was instituted identified a complex mechanism, involving shortening and settlement of the arches through mortar wash out, followed by dropping of the spandrel causing diagonal cracking and subsequent lateral movement.
Any remedial strategy had to consider both the requirements of Welsh Historic Monuments and the short winter closure window before Easter reopening. The preferred scheme was removing all the existing saturated fill, waterproofing and reconstruction of a new, watertight channel. Particular care was needed to avoid instability of the arch during the works and any change in the appearance of the structure.