Oakenholt, North Wales October 2021

Lead Brook runs into the River Dee where it reaches the sea. It is currently fragmented by a reservoir which impacts the migration of elvers upstream into the headwaters of the brook. To improve their chances of successfully migrating upstream, reservoir spillway retrofit is required.


Eel pass will span approx. 200m

Project requirements

The problem

Design a low maintenance eel pass that would help elvers to migrate upstream along the reservoir spillway and obtain consent from NRW.

Our approach

The solution

A site visit was conducted with NRW and Essity Ltd to discuss potential options for eel passage at the beginning of the project. After a consensus was reached on the best way forward, we prepared outline designs for a mussel spat eel pass and constructed a prototype to aid in the constructability of the design. The outline designs were reviewed by the client and the Environment Agency and NRW were consulted throughout, building on their experience of mussel spat rope eel passes to ensure that the design was as effective as possible. The Eel pass is made of multiple strands of mussel spat rope to create a low flow route along the edge of the spillway which will vegetate up and provide a safe passage route.


Project outcomes

The results

Construction issued designs including buildability statement and designers risk assessment. Consent from NRW.

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Given our commitment to environmental best-practice, we were keen to make this significant investment to help protect European eels that have been in decline over the past 30 years and are on the critically endangered list.  We are grateful to Fairhurst, FiveRivers and the NRW for helping us to meet the requirements of the Eels Regulations.
Keith Lloyd, Essity Area Technology Manager
Jacob Dew - Director of Business Development & Estimating at FiveRivers (5R)

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Jacob Dew

Director of Design & Estimating

Get in touch by either phone or email to speak with Jacob and discuss your needs.