Concrete Refurbishment of Weir to Modify Profile & Ease Passage of Fish
Situated beneath Bridge 106, which carries the West Coast main railway line over the River Lune, this concrete weir, constructed in 1979, is composed of a concrete, two tier slab spanning between the bridge abutments.
Exposed concrete surfaces needed refurbishment to make good the effects of peak flows up to 385m³/s, which often convey large boulders and other debris. The refurbishment work was designed to provide a modified weir profile to assist passage of migrating fish past the weir whilst not collecting debris.
For repairs and repointing, consultants Halcrow Group, specified the use of Monomix, a high build polymer modified mortar that can be applied to vertical faces at thicknesses up to 80mm in a single application. Fastfill was used to reinstate the surface of the lower central channel that had been badly eroded by scour. In order to create some turbulence in the flow to help the fish swim upstream, large pieces of aggregates sourced from the stream were embedded into Fastfill. The products used are non hazardous when cured and would not affect the aquatic environment.