Successful Breakthrough at Hinkley Point C Fish Return

Joseph Gallagher Limited (JGL) has successfully completed tunnelling works on the Fish Return System at Hinkley Point C, delivering a major milestone in one of the UK's most significant infrastructure and environmental protection projects. The works form a critical part of the power station's extensive measures to protect marine life in the Bristol Channel.

Working alongside the Kier BAM Joint Venture, JGL delivered the construction of a 620-metre-long, 1.8-metre-diameter sea outfall tunnel using pipe jacking methodology.

The tunnel will safely return fish and marine life that inadvertently enter the cooling water system back to the Bristol Channel, supporting the long-term protection of the local marine ecosystem.

The project presented a number of complex engineering challenges, including restricted working space, offshore tunnelling operations, significant tidal variations, adverse marine weather conditions, vertical double curves within the alignment, and readiness to undertake hyperbaric interventions at pressures of up to 2.4 bar. JGL's specialist tunnelling expertise, combined with innovative engineering solutions and advanced tunnelling equipment, enabled the successful delivery of the works safely and efficiently.

Following five months of tunnelling, the Herrenknecht AVN1800 Tunnel Boring Machine (TBM), named Sarah Guppy by local schoolchildren after the pioneering Bristol engineer, was successfully recovered from above the seabed using a floating crane. The machine will now be refurbished and prepared for future tunnelling projects.

The Fish Return System forms part of a wider £700 million investment in fish protection measures at Hinkley Point C. These measures include acoustic fish deterrent systems and specially designed low-velocity water intake structures, all aimed at minimising the impact of the facility on local marine life.

Throughout the project, sustainability remained a key focus. JGL implemented a closed-face tunnelling methodology, enabling safer construction while protecting the surrounding environment.

All process water was recycled through a dedicated separation system, tunnel spoil was reused on site, and only biodegradable chemicals were utilised during construction. No tunnel effluent was discharged without treatment, reinforcing the project's commitment to environmental stewardship.

"The completion of the Fish Return System tunnel is a significant achievement for our team and project partners. This project required innovative engineering, specialist tunnelling expertise and exceptional collaboration to overcome a range of technical and environmental challenges. We are proud to have delivered this important piece of infrastructure safely, sustainably and to programme, supporting both the future operation of Hinkley Point C and the protection of marine life in the Bristol Channel."