SuDS should be treated as an early design input on development in Liverpool, not a final drainage calculation. Liverpool contains a high proportion of previously developed and made-ground sites, so infiltration cannot be assumed from mapping alone. Drainage design should be coordinated with ground-risk information where contamination, variable fill or shallow infrastructure may affect the preferred SuDS route.
What matters on a Liverpool site
- BRE 365 infiltration evidence where soakaways are proposed
- Phase 1 or ground-investigation information where historic land use may affect infiltration
- space for attenuation and treatment within dense redevelopment layouts
- the proposed discharge hierarchy and any sewer connection requirements
The current drainage framework
For development in England, the 2025 National Standards for Sustainable Drainage Systems set out a runoff hierarchy and design expectations covering flood risk, water quality, amenity and biodiversity. Local planning and flood-risk requirements still need to be addressed for the individual site.
National Standards for SuDS provides the national framework; the project still needs a site-specific strategy and evidence appropriate to the proposed development.
Where infiltration testing fits
If infiltration is being relied upon, testing should be located and designed around the proposed drainage features rather than used as a generic site-wide assumption. Where previous land use or made ground could affect water quality, review the ground-risk information alongside the drainage proposal.
What to send us
Send the site boundary, proposed layout, levels or topographical survey where available, drainage concept, planning or flood-risk comments, and any previous ground investigation. We can then identify whether infiltration testing, drainage support or linked environmental work is needed.
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