SuDS approval in Wales: how the SAB process works

Anyone designing in Wales needs a suds approving body wales consent as well as planning permission, and the two are separate processes with separate timetables. Schedule 3 to the Flood and Water Management Act 2010 was brought into force in Wales in January 2019, creating a SuDS Approving Body within each local authority. Construction cannot lawfully begin on a qualifying development until that body has approved the drainage design. This is a Wales-only regime. Schedule 3 has not been brought into force in England, so English practice offers no guide here.

What Schedule 3 brought into force

The regime does three things. It makes sustainable drainage compulsory for qualifying development, it sets national standards the design must meet, and it gives the approving body a duty to adopt and maintain approved systems that serve more than one property.

The approving body sits within the county or county borough council, and is administratively separate from the planning department even where officers work in the same building. Approval is not a planning condition and it is not discharged by the planning case officer.

Applicants sometimes assume that a drainage condition on a planning permission covers the ground. It does not. Both consents are needed, and starting construction with only one of them is a breach.

The trigger and what counts

The requirement applies to construction work with a construction area of 100 m² or more, and to development of more than one dwelling. Single dwellings are caught where the construction area reaches the threshold.

Construction area is measured generously. It covers the building footprint plus hardstanding, access, parking and any other surfaced area forming part of the works, which is why a modest house with a long drive can be caught where the house alone would not be.

Some works are outside the regime, including certain highway works carried out by a highway authority. Check the exemptions against the specific scheme rather than assuming, because the categories are narrower than they first appear.

How it sits alongside planning permission

You can apply for approval before, alongside or after a planning application. Each sequence has a cost.

Applying first gives certainty about the drainage layout before the planning drawings are fixed, which matters because the standards can force a change in levels, in the position of attenuation features or in the amount of open space given over to drainage.

Applying alongside is the usual choice, and it works where the two design teams talk to each other.

Applying afterwards is the route that causes redesign. A layout approved for planning with drainage that cannot meet the standards has to change, and that change may itself need a planning amendment.

The practical advice is to design the drainage first and let it shape the layout. Attenuation, conveyance and treatment features take space at ground level, and squeezing them in at the end produces the tanked solutions the standards are meant to discourage.

The Welsh national standards

The statutory standards cover six areas, and a design has to satisfy all of them rather than trading one against another.

• Surface water runoff destination, applying a hierarchy that starts with collection for use, then infiltration, then discharge to a surface water body, then a surface water sewer, with a combined sewer last.
• Hydraulic control, covering runoff rates and volumes and the events the system must handle.
• Water quality, using a risk-based approach to treatment appropriate to the land use.
• Amenity, expecting drainage to contribute to the quality of the place rather than being fenced off.
• Biodiversity, expecting habitat benefit from the drainage features.
• Design of drainage construction and structural integrity, covering buildability, materials and long-term performance.

Amenity and biodiversity are the standards English-trained designers underestimate. A below-ground cellular storage tank may satisfy the hydraulic requirement and still fail, because it delivers nothing for either.

One further point on treatment. The water quality standard works through a risk-based approach that matches the number and type of treatment stages to the pollution risk of the surfaces draining to them. A car park serving a commercial unit needs more than a roof does, and a scheme that routes everything through a single feature will be asked to show its working.

Infiltration needs evidence. Ground investigation and infiltration testing, with groundwater levels and any contamination risk considered, is expected rather than optional, and an assumed infiltration rate will not be accepted.

What an application to the approving body contains

The submission is an engineering one, more detailed than a planning drainage note.

1. Drainage layout drawings showing every feature, with levels.
2. Hydraulic calculations demonstrating compliance with the runoff standards, including the design events.
3. Ground investigation and infiltration testing results where infiltration is proposed.
4. Evidence supporting the destination chosen, including correspondence where a discharge consent or connection agreement is needed.
5. A treatment train showing how water quality is addressed.
6. A construction method statement and phasing.
7. A maintenance plan covering the design life, with responsibilities and access arrangements.

Maintenance planning deserves more attention than it usually gets, because it is what the adoption decision turns on. Set out the inspection frequency, the tasks, the access route for machinery and the party responsible until adoption takes effect.

Fees are set by regulation and vary with the size of the development. Determination periods are set in the regulations too, measured in weeks and longer for larger schemes, so confirm the current period with the approving body and build it into the programme rather than discovering it late.

Adoption, inspection and the build programme

Where an approved system serves more than one property and has been built in accordance with the approval, the approving body has a duty to adopt and maintain it. That is a significant difference from the English position, where responsibility usually falls to a management company or a water undertaker.

Adoption comes with conditions. The body inspects during construction, and it will want a bond or other security against the possibility that the works are not completed properly. Build the inspection points into the programme, because a feature covered up before it has been seen may have to be opened again.

The sequencing point that catches developers is simple. Approval must be in place before construction begins, and site clearance and enabling works can count as a start. Allow for the determination period, for any request for further information, and for the possibility that ground conditions revealed by testing force a change in approach.

Where a scheme also needs flood risk evidence, the Flood Risk Assessment and the Drainage Strategy should be prepared together and should tell the same story about levels, discharge points and residual risk. PlanScope's drafting is grounded in English policy, so a Welsh submission needs the reviewer to check the design against Planning Policy Wales, the relevant Technical Advice Notes and the Welsh statutory standards. The full list of report types shows what else a Welsh scheme is likely to need alongside.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

Draft the drainage and flood documents for a Welsh scheme on PlanScope, then have them checked against the Welsh standards before submission.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.