United Utilities’ £30M ‘spongier’ Liverpool: retrofit SuDS design notes for engineers
Reviewed by Tom Sullivan

First reported on New Civil Engineer
30 Second Briefing
United Utilities has announced a £30M programme to retrofit sustainable drainage across Liverpool, aiming to make the city “spongier” by intercepting and attenuating rainfall before it reaches combined sewers. Measures are expected to include permeable paving, rain gardens and other SuDS features on highways and public realm to cut surface runoff volumes and peak flows during intense storms. For civil and drainage engineers, the scheme signals more retrofit SuDS design in dense urban streetscapes, with a premium on hydraulic modelling, utility coordination and constructability in constrained corridors.
Technical Brief
- Utility is lead client, so interventions must integrate with existing wastewater network ownership and asset standards.
- Works will focus within Liverpool’s existing urban footprint, implying brownfield constraints and dense buried services.
- Retrofit SuDS will need to be sequenced around live traffic, requiring phased lane closures and night working.
- Designers will have to coordinate with highways teams for adoption and long-term maintenance.
- Asset performance will likely be monitored via flow/level sensors in retrofitted catchments to evidence sewer load reduction.
- Construction supply chain will centre on small-footprint, repeatable interventions rather than large single-site schemes.
- Programme offers a template for other combined-sewer cities to package city-wide SuDS as regulated utility investment.
Our Take
The Better Rivers programme and the Knutsford stormwater tunnel work suggest that this Liverpool scheme is likely to be integrated with wider efforts to cut combined sewer overflows across North West England, which will influence how storage, infiltration and green infrastructure are sized and phased.
Recent coverage of United Utilities includes deployment of an electric excavator at Davyhulme, indicating that low‑carbon construction methods may be expected on this Liverpool project as clients start to demand embodied‑carbon reductions alongside flood resilience outcomes.
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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