- 23rd June 2017
- Posted by: Sophie Bunker
- Category: Projects
We have been working with Yorkshire Water to provide the detailed design of three fish passes, at three sites: Jordan’s Dam, Langsett Reservoir and Wharncliffe. These sites were taken from outline design stage to detailed design. We used a joined-up approach between the hydraulic design team at Saltaire and the structural design team at Tadcaster. We also involved the contractor at an early stage to provide much needed input on buildability.
Each site has challenging access constraints. Early contractor involvement has been key to provide a design that works for each site. The Langsett site for example, is within an area visited by tourists and walkers. It is in an isolated location within woodland, with steep narrow access via a bridleway. The setting of Langsett reservoir meant that we also had to be mindful of the natural beauty of the location.
A balance was struck between providing a safe means of access for Yorkshire Water staff to access and maintain the pass, and maintaining public safety as far as reasonably practicable. This involved engagement with the operations and recreation teams at Yorkshire Water and local park rangers. Their involvement was key in providing a solution that was safe. It allowed access to all parts of the fish pass for maintenance whilst restricting public access. This information was recorded in a public safety risk assessment (PSRA).
The pass will be clad in wood, to soften its appearance and help tie it to the local environment. Other options explored but not pursued were the matching of stone to that of the surrounding masonry, by either using the same stone, or by utilising in-pressed concrete to give the effect of natural stone.
The hydraulic performance of technical fish passes, such as the one proposed at Langsett, are highly sensitive to the level and slope of the pass. Therefore the fish passes must be constructed to tight tolerances. To aid Yorkshire Water with the successful construction of them, we are providing site supervision services at the construction phase. We have also aided the contractor by providing part of the temporary works designs, for items such as the crane lifting pad
Langsett is starting on site in late June. It aims to be finished by the first week in October, just in time for the brown trout (Salmo trutta) migration season!
Fish pass schemes such as this, and other river restoration projects, are in response to European legislation which aims to re-naturalise the rivers of Europe. The features imposed on rivers by us to make use of them cannot always be removed. However, a feature such as a fish pass may allow the river to not only continue working for us but also work for its would be inhabitants.
The benefits of the pass are primarily ecological. It allows genetic mixing of the (currently distinct) brown trout populations upstream and downstream of the weir. This in turn delivers ecosystem services to benefit nature lovers and tourists. There is an opportunity to use this fish pass as part of environmental education programmes. This would educate the general public around the importance of fish migration and maintaining and improving the environment in which we live.