£7bn Abingdon reservoir: design-stage progress and value tests for engineers
Reviewed by Joe Ashwell

First reported on New Civil Engineer
30 Second Briefing
Regulators have advised that Thames Water’s proposed £7bn Abingdon reservoir is sufficiently mature to move to the next development stage, unlocking further public funding for detailed design and assessment. The strategic storage scheme, intended to bolster long-term water supply resilience for London and the South East, will now undergo more advanced option appraisal and environmental scrutiny. However, regulators have questioned the scheme’s value-for-money case, signalling closer interrogation of cost assumptions, demand forecasts and alternative supply or demand-management options.
Technical Brief
- Assessment concluded scheme documentation and option development are now at a “sufficiently mature” stage.
- Next phase will require more detailed engineering design, construction phasing and cost-risk breakdowns.
- Environmental appraisal must now move from high-level screening to scheme-specific impact assessment and mitigation design.
- Value-for-money concerns imply closer scrutiny of unit water costs versus alternative supply and demand schemes.
Our Take
At around £7bn, the Abingdon reservoir would sit at the very top end of UK water infrastructure schemes in our Infrastructure coverage, implying unusually high regulatory scrutiny on cost–benefit and alternatives such as leakage reduction or inter-regional transfers.
Thames Water already features prominently in our UK Infrastructure stories, and a scheme of this scale will likely interact with its balance sheet constraints and ongoing regulatory reviews of its asset management plans rather than being treated as a standalone project decision.
Among the 164 Infrastructure stories tagged to Projects and Sustainability, few involve single assets of this capital intensity in the United Kingdom, suggesting Abingdon will become a reference case for how Ofwat and planning bodies treat large, climate-resilience-driven storage proposals.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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