Fish migration had been severely affected by the installation of stone-built weirs within watercourses, which had been installed to serve local mills. The main objective of the project was to provide safe passage for migrating fish to upper reaches of the water course.
The client had designed a new fish pass which was to be constructed in a neighbouring field to the stone weir. The meant the heritage could be retained, whilst also allowing fish to re-coup lost habitats of yester-year. The fish pass consisted of 20nr bays, which had a constant increase in height of 200mm per bay.
The bays were excavated into the neighbouring field, with erosion of the soils being protected by a new large rock boulder wall. The bays were defined with rocks 500-800mm diameter to act as sills to maintain the difference in levels between bays. The base of the bays was lined with rock 150mm-300mm which were hydraulically compacted.
The bypass channel was largely constructed offline, which minimised the risk of polluting the watercourse, however, over pumping and silt control measures were in place should any pollution occur.
Site access was difficult as it was using a public right of way through a wooded area. Pedestrian and traffic management was put in place to ease the situation.