Countess Wear Sewage Treatment Works Upgrade (Flood Protection & System Upgrade)
Countess Wear, Exeter, Devon · 2016 (Flood protection project completed); Ongoing investment in Exeter's sewage system over 4 years [Water Projects Online, Instagram] · £140m (across 82 projects to upgrade Exeter's sewage system) [Instagram]; Specific cost for flood protection not explicitly stated, but part of a larger investment.
The judgement call
Account-gated at launchComprehensive ground investigation and hydrogeological modelling to optimise sheet piling extent and depth [Water Projects Online] - Risk-based approach to flood protection, phasing work and utilising natural protection from the canal [Water Projects Online] - Extensive trial hole excavation and ground-penetrating radar (GPR) to locate and mitigate risks from unknown services [Water Projects Online] - Collaborative approach with Environment Agency and local councils for environmental considerations and planning [Water Projects Online]
Key engineering challenges
Protecting the STW from extreme flood events (overtopping and excessive groundwater levels) due to its location on marshland of the River Exe estuary floodplain [Water Projects Online] - Maintaining serviceability during flood conditions and ensuring rapid recovery [Water Projects Online] - Addressing the impact of climate change on flood risk [Water Projects Online] - Upgrading Exeter's combined sewage system to decrease storm overflow spills [Instagram]
Project facts
- Client / owner
- South West Water (SWW)
- Lead contractor
- SWW Delivery Alliance H5O (Balfour Beatty as principal contractor for flood protection) [Water Projects Online]
- Lead designers
- Pell Frischmann (lead designer for flood protection) [Water Projects Online]
- Project type
- upgrade | flood protection
- Scale
- 397m of 10m sheet piling; 112m of 5m sheet piling; 95m of reinforced concrete wall [Water Projects Online]
- Disciplines
- Civil; structural; geotechnical; environmental; process
- Standards & frameworks
- Environment Agency flood protection guidelines; Freshwater Fish Directive (implied by focus on river health)
Sources: Water Projects Online: https://waterprojectsonline.com/case-studies/countess-wear-stw/ (Accessed: 2026-06-10) - Instagram (Luke Pollard MP): https://www.instagram.com/p/DV6LdL8DHez/ (Accessed: 2026-06-10)