SuDS Approving Body consent in Wales and what it needs

This article is about Wales. Schedule 3 to the Flood and Water Management Act 2010 was brought into force in Wales on 7 January 2019, which means almost all new construction work in Wales with drainage implications needs sustainable drainage approval from the SuDS Approving Body, known as the SAB, before construction starts. England has never brought Schedule 3 into force, so an English developer moving a scheme across the border meets a consent that has no equivalent at home.

The SAB sits within the local authority, but it is a separate consenting function from planning. Planning permission does not carry SAB approval with it, and SAB approval does not imply that permission will be granted.

Why Wales brought Schedule 3 into force and England has not

Schedule 3 was drafted after the 2007 floods to move surface water management out of the sewer by default. Welsh Ministers brought it into force in January 2019 along with statutory national standards for sustainable drainage design, so in Wales the design of surface water drainage is tested against those standards by a technical body rather than left to a planning condition. In England the same schedule is still not in force and surface water drainage is handled through planning policy, the lead local flood authority as a statutory consultee and conditions.

That difference changes the programme. In Wales you are assembling a technical drainage submission on a defined statutory timetable. In England you are usually satisfying a condition after permission.

A drainage strategy written for an English planning application will not answer the Welsh standards without rework, because the Welsh document is a technical consent submission rather than a policy narrative.

Which construction work needs SAB approval

Approval is needed for construction work with drainage implications where the construction area is 100 square metres or more, and for any development of one dwelling or more. There are exemptions, including work by highway authorities on public roads where separate arrangements apply, and single dwellings built by a self-builder are not exempt.

Two points catch people out. The threshold counts the construction area rather than the built footprint, so hardstanding, access tracks and working areas count. And the requirement applies to construction, so a scheme that already has planning permission still cannot start until the SAB has approved the drainage system.

The national standards the design is tested against

The Welsh Government's statutory standards for sustainable drainage systems are the test. They cover surface water run-off destination and hydraulic control, water quality, amenity and biodiversity, and construction and maintenance. Each standard has to be answered in the submission, not just the hydraulic ones.

A submission that fails usually fails on the same points:

• No infiltration testing, or testing carried out at the wrong depth or in the wrong season, so the discharge hierarchy cannot be evidenced
• Attenuation sized without allowance for climate change over the design life
• Water quality left to a single trapped gully with no treatment train
• Amenity and biodiversity standards answered by pointing at the landscape plan rather than by design
• No maintenance schedule, no access for maintenance vehicles and no named body to carry it out

Getting the pre-application discussion with the SAB early is worth more than any amount of redrafting later, because the officers will tell you which discharge route they will accept.

Sequencing SAB approval against planning permission

The two consents run in parallel, and the drainage design has to be compatible with the layout you are seeking permission for. Attenuation basins, swales and permeable surfaces take land, and a layout drawn to the planning standard of detail often cannot accommodate the drainage once the SAB has finished with it.

1. Establish the discharge route and infiltration potential before the layout is fixed.
2. Reserve land for above ground SuDS features in the masterplan rather than squeezing them into leftover space.
3. Submit the planning application with a drainage strategy that matches the SAB submission.
4. Lodge the SAB application so that determination lands before your intended start on site.
5. Do not start construction until approval is issued, because construction without approval is an offence.

Where the planning permission and the approved drainage system diverge, you will need to vary one of them, and varying the permission under section 73 takes longer than most programmes allow.

Adoption and the maintenance question

Schedule 3 ties approval to maintenance. Where a SuDS scheme serves more than one property, the SAB adopts it if it is built in accordance with the approval, and the authority then maintains it. That makes the construction stage inspection regime meaningful: build it differently and adoption can be refused, leaving the maintenance liability with a management company and a service charge.

Plan for adoption from the start. Features designed for adoption need access, defined boundaries, safe side slopes and a maintenance schedule the authority will accept. Retrofitting those requirements after the layout is approved is expensive.

Discharge hierarchy and evidence of infiltration

The hierarchy runs from infiltration to the ground, then to a surface water body, then to a surface water sewer, then last to a combined sewer. Each step down has to be justified with evidence rather than convenience.

Infiltration testing to a recognised method, at the depth the feature will actually sit, in ground conditions that are representative, is the evidence that decides the top of the hierarchy. Where groundwater is high or the ground is clay, say so with the test results and move down a step. Where a watercourse is available, you will need the consent of the riparian owner or the drainage body, and where a sewer connection is proposed, written confirmation from the undertaker.

Flood risk is assessed separately again. A site in a flood zone still needs the flood consequences assessment that Welsh policy requires, and the flood risk assessment page sets out the English equivalent for comparison. The two documents share survey data but answer different questions, and reviewers reject submissions that fold one into the other.

Our note on drainage evidence for small sites deals with a related constraint in Northern Ireland, where capacity at the treatment works rather than a separate consent is the obstacle. The frameworks are different and so are the documents.

Common reasons approval is refused

Refusals cluster around evidence rather than concept. The design is plausible but the ground investigation is thin, or the climate change allowance is not stated, or the maintenance plan names nobody. Where an applicant has appealed, the appeal goes to Welsh Ministers rather than through the planning appeal route, so it is a different process with its own timescales.

Two habits reduce the risk. Write the submission so each standard has its own heading and its own evidence, and include the calculations in an appendix rather than summarising them. Technical reviewers approve what they can check.

The other avoidable failure is timing. Applicants treat the SAB submission as a post permission task, discover that the approved layout cannot hold the attenuation volume, and then have to choose between a worse scheme and a fresh planning application. Drainage capacity is a design constraint in Wales in the way that daylight or parking is, and it belongs in the first sketch layout.

PlanScope is grounded in English national policy and English local plans, so a Welsh scheme needs the reviewer to check Planning Policy Wales, the relevant Technical Advice Notes and the Welsh statutory SuDS standards. PlanScope drafts the narrative planning documents and flags where site facts are missing. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required, and a SAB submission should be prepared by a drainage engineer.

This is general guidance, not legal advice, and the Welsh standards and application fees are updated from time to time, so check the current position with the SuDS Approving Body at your local authority. Browse the report types on PlanScope to see which supporting documents your application will need.