The overall project consists of the following three elements:
i) Replacing damaged and missing coping stones with new stones.
ii) Construction of a fish pass together with.resting pools
iii) Construction of access path, viewing platform, new fencing and seat
Repairing the Stonework
The new coping stones will be secured to the existing structure by drilling and grouting stainless steel dowel bars into the lower courses of stone. In view of the nature and importance of the structure, it is a requirement of the listed building consent that the stonework should match the existing and that lime mortar should be used to bed the blocks. Samples of the masonry and mortar have been taken by the Advanced Concrete and Masonry Centre of the University of Paisley and are currently being analysed.
The New Fish Pass
The River Calder is classified as a salmonoid river and trout and salmon have been seen near the foot of the falls. Upstream of the waterfall there is approximately 4 miles of excellent spawning ground for salmon and both the local angling clubs have been trying to have a fish pass constructed for some years. The proposed renovation of the dam structure is an ideal opportunity to achieve this aim
After much consideration and consultation with the planning authority it was decided that the most appropriate design for the fish pass would be a Denil type consisting of a rectangular aluminium or stainless steel channel with baffle plates. It was decided to locate the fish pass on the west bank to reduce the danger of interference by poachers and because of the topography of the bank. There would be an intermediate resting pool formed of natural stone on the bank. Two small dams will be constructed in the channel downstream of the falls to raise the water level enough for fish to jump into the first pool which will be formed on an existing rock ledge at the base of the falls.
The connection of the fish pass to the sill of the falls will require detailed hydraulic and structural analysis. Model tests to facilitate this have been carried out in the School of Engineering and Science at the University of Paisley. A geophysical survey of the site has also been carried out by the University of Paisley to establish if there is a natural rock ledge at the site but this has so far not yielded any conclusive results.
The Construction of a Viewing Platform
At present, access to the falls is via a very dangerous section of narrow wall with no protection from a fall of about 5 metres onto rocks underneath the waterfall. There is therefore clearly a need to provide a safe access to the site including access for disabled people. The viewing platform will be formed by widening the existing narrow wall on the east side of the falls to provide full disabled access with safety railings. It is intended that the stonework of the viewing platform should match that of the dam itself. To this end, about 50 of the coping stone blocks which had washed away from the sill of the dam, have been recovered by volunteers. Most of these stones are too worn or damaged to be used in the reconstruction of the dam sill, but they could be easily cut to form stones for use in the construction of the viewing platform.