Gauging station eel pass design programme

Location: North Wales                                                                    Client: Natural Resources Wales


Habitat connectivity is essential to ensure freshwater ecosystems are able to adapt to climate change impacts. Barriers to fish and eel migration, created by weirs for example, have the potential to significantly disrupt connectivity between water bodies.

As a key regulatory authority with responsibility for enforcing The Eels (England and Wales) Regulations 2009, Natural Resources Wales (NRW) is committed to demonstrating a high level of compliance with this legislation, to meet its statutory obligations under the Water Framework Directive.

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We were commissioned to produce a detailed design for the construction of eel passage solutions at twelve NRW-operated gauging weirs across north Wales. To develop an appropriately robust design, our specialist engineers and freshwater and terrestrial ecologists mobilised to site to develop an ecological and asset condition baseline.

We carried out an optioneering exercise for each site, and the solutions proposed consisted of gravity-fed passes at 7 sites and pumped passes at the remaining 4 sites. We worked with the client to accommodate their desire to incorporate mussel rope into the designs, which would supplement the inclusion of commercially available, dedicated eel pass materials. The design of the pumped passes used our understanding of eel behaviour. These passes incorporated flexible discharges to encourage individual eels off the eel tile media at the apex of the pass, and into a flume pipe which return them to the river upstream of the weir.


Our delivery model was one of collaboration and partnership between JBA and our client. We had continuous and transparent dialogue throughout, to ensure our client was supported during all decision making, and that the production of designs suited their technical and operational needs.

This process included liaison with Fisheries and Hydrometry & Telemetry staff, as well as with our own structural, mechanical and electrical engineers, and our fish ecologists. This was done to achieve technical performance and access criteria, and ensure operational staff are able to safely and confidently maintain the designed solutions.

The project drew on experience of Fisheries staff in both NRW and the Environment Agency, to ensure the designs took advantage of best available technology in eel pass design.

We are looking forward to construction at 3 sites this calendar year, with the others planned for construction in 2022.

Want to know more?

Email Jon Whitmore at our Saltaire office for more information on this project, and about our fish pass design capabilities. You can also visit our Fisheries webpage.

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