How to Discharge Drainage Conditions on Your Planning Permission

You have secured planning permission for your development. Congratulations. But attached to that permission are conditions — and among the most common, and most frequently problematic, are drainage conditions.

Drainage conditions are pre-commencement conditions, meaning they must be discharged (approved by the LPA) before construction can begin. Failure to discharge them before starting work is a breach of the planning permission and can result in enforcement action. More practically, it can cause construction delays, increased costs, and complications with warranty providers and building control.

This article explains what drainage conditions typically require, how to discharge them efficiently, and how to avoid the common pitfalls that cause delays.

Why Are Drainage Conditions Imposed?

Drainage conditions are imposed because, at the planning application stage, the drainage strategy is typically outline or conceptual. The strategy demonstrates that the development can be drained satisfactorily in principle, but it does not provide the detailed design information needed for construction.

The conditions require the developer to submit a detailed drainage design for approval before construction begins. This ensures that:

• The detailed design is consistent with the drainage strategy approved at planning stage
• The detailed design addresses any matters that were left unresolved at planning stage
• The LLFA and water company have an opportunity to review the detailed design
• The LPA can be satisfied that the drainage arrangements are technically sound before construction starts

Common Drainage Conditions

While the exact wording varies between LPAs and between permissions, most drainage conditions fall into a few common categories:

Surface Water Drainage Scheme

The most common drainage condition requires the submission of a detailed surface water drainage scheme. A typical condition reads:

“No development shall take place until a detailed surface water drainage scheme for the site, based on sustainable drainage principles and an assessment of the hydrological and hydrogeological context of the development, has been submitted to and approved in writing by the local planning authority. The scheme shall subsequently be implemented in accordance with the approved details before the development is completed.”

This condition requires:

• A detailed surface water drainage design (not just a strategy)
• The design to be based on SuDS principles
• The design to be informed by hydrological and hydrogeological assessment (including infiltration testing)
• LPA approval before development commences
• Implementation of the approved scheme before the development is completed

Foul Water Drainage Scheme

A separate condition may require details of foul water drainage:

“No development shall take place until a scheme for the disposal of foul water has been submitted to and approved in writing by the local planning authority. The scheme shall be implemented in accordance with the approved details.”

SuDS Management and Maintenance Plan

A condition may require a management and maintenance plan for SuDS features:

“No development shall take place until a SuDS management and maintenance plan for the lifetime of the development has been submitted to and approved in writing by the local planning authority. The plan shall include the arrangements for adoption by any public authority or statutory undertaker, and any other arrangements to secure the operation of the scheme throughout the lifetime of the development.”

Construction Phase Drainage

Some conditions require details of temporary drainage arrangements during the construction phase:

“No development shall take place until a construction phase surface water management plan has been submitted to and approved in writing by the local planning authority. The plan shall demonstrate how surface water runoff will be managed during the construction phase to prevent increased flood risk or pollution.”

Verification Report

An increasingly common condition requires a post-construction verification report:

“Within 3 months of completion of the surface water drainage system, a verification report carried out by a qualified drainage engineer shall be submitted to the local planning authority to demonstrate that the SuDS system has been constructed as per the approved scheme.”

The Discharge Process: Step by Step

Step 1: Review the Conditions

Read all the drainage conditions carefully and understand exactly what each one requires. Pay attention to:

• Trigger points — most drainage conditions are pre-commencement, meaning they must be discharged before any construction work begins (including site clearance and demolition in some cases)
• Specific requirements — some conditions list specific items that must be included in the submission
• Consultees — the LPA will typically consult the LLFA and water company on the submission

Step 2: Gather the Data

To prepare the detailed drainage design, you will need:

Topographic survey. An accurate topographic survey of the site, showing existing levels, drainage features, watercourses, and services.

Ground investigation. If not already completed, BRE 365 infiltration testing and/or borehole logs to determine the ground conditions and infiltration potential.

Pre-development enquiry. If the drainage strategy proposes connection to a public sewer, a formal pre-development enquiry to the water company to confirm the point of connection, maximum discharge rate, and any capacity constraints.

The approved drainage strategy. The detailed design must be consistent with the drainage strategy that was approved at planning stage. Any departures from the approved strategy should be discussed with the LPA and LLFA before submission.

LLFA guidance. Check the LLFA’s published guidance for condition discharge submissions. Many LLFAs have specific requirements for the level of detail, modelling approach, and supporting information that must be provided.

Step 3: Prepare the Detailed Design

The detailed drainage design typically includes:

Drainage layout drawing. A plan showing the proposed drainage network, including:

• All pipes, manholes, and connections
• SuDS features (soakaways, permeable paving, swales, basins, ponds)
• Attenuation storage features
• Flow control devices (hydro-brakes, orifice plates)
• Connections to public sewers or watercourses
• Overland flow routes for exceedance events

Drainage calculations. Computer modelling (typically using MicroDrainage, InfoDrainage, or equivalent software) demonstrating that:

• The drainage system can accommodate all storm events up to the 1% annual probability event with climate change allowance without flooding
• The discharge rate is limited to the agreed rate (greenfield or as specified)
• Attenuation storage is adequate
• The exceedance strategy is effective

Long sections. Longitudinal sections of the main drainage runs, showing pipe sizes, gradients, invert levels, and cover depths.

Construction details. Details of the construction of SuDS features, flow control devices, and other drainage infrastructure.

SuDS management and maintenance plan. A document setting out the long-term management and maintenance arrangements for all SuDS features, including:

• Maintenance tasks and frequencies
• Responsibility for maintenance
• Inspection and monitoring arrangements
• Estimated annual costs
• Arrangements for handover to the management company or adopting body

Step 4: Submit the Application

The submission is made as a “discharge of condition” application (also known as a Section 73 approval or DOC application) to the LPA. The application should include:

• A covering letter explaining which conditions are being discharged
• All the technical documents and drawings listed above
• The appropriate fee (currently GBP 145 per request in England, or GBP 43 for householder applications)

Step 5: Consultation

The LPA will consult the LLFA (for surface water drainage) and possibly the water company (for sewer connections). The statutory consultation period is typically 21 days, but in practice, responses can take longer.

Step 6: Review and Response

The LLFA may:

• Approve the submission without comment
• Approve the submission with minor comments that do not require re-submission
• Request additional information or amendments — this is common, and the most frequent cause of delay
• Object to the submission — this is less common but can occur where the design has significant deficiencies

If additional information or amendments are requested, prepare the response promptly and resubmit. Each round of consultation adds time to the process.

Step 7: Decision

Once the LLFA is satisfied, the LPA will issue a formal approval of the condition discharge. Keep this approval carefully — it is the evidence that the condition has been properly discharged, and it may be required by warranty providers, building control, and future purchasers.

Common Causes of Delay

Insufficient Infiltration Evidence

The most common cause of delay is inadequate infiltration testing. If the drainage strategy assumed that infiltration is not feasible, but the evidence is not convincing, the LLFA will request additional testing before accepting a lower-tier drainage solution.

Solution: Carry out BRE 365 testing early in the development process, ideally before the planning application is submitted. If the conditions require a detailed drainage scheme, the infiltration testing data should be available before the detailed design is prepared.

Inconsistency with the Approved Strategy

If the detailed design departs significantly from the drainage strategy approved at planning stage, the LLFA or LPA may object. Common inconsistencies include:

• Changing the discharge destination (e.g., from watercourse to sewer)
• Increasing the discharge rate above the rate agreed at planning stage
• Removing or downsizing SuDS features
• Changing the attenuation storage volume

Solution: If the detailed design needs to depart from the approved strategy (which can happen as more detailed site information becomes available), discuss the changes with the LPA and LLFA before submitting the condition discharge application.

Inadequate Modelling

The LLFA will scrutinise the drainage calculations. Common modelling issues include:

• Using incorrect rainfall data or climate change allowances
• Not modelling the full range of storm durations (the critical storm duration varies between sites)
• Not demonstrating the exceedance strategy
• Not demonstrating the half-drain time for infiltration features (typically required to be less than 24 hours)

Solution: Use appropriate modelling software and ensure the model parameters comply with the LLFA’s requirements. Check the LLFA’s published guidance for specific modelling requirements.

No Maintenance Plan

A maintenance plan is a standard requirement, but it is frequently overlooked or inadequately prepared. The LLFA will want to see a credible plan that covers all SuDS features, identifies the responsible party, and sets out the maintenance tasks and frequencies.

Solution: Prepare the maintenance plan as part of the detailed drainage design, not as an afterthought. Use the CIRIA SuDS Manual as a guide for maintenance requirements.

Water Company Delays

Obtaining confirmation of sewer capacity and connection agreements from the water company can be slow. Some water companies have long processing times for pre-development enquiries and Section 104/106 applications.

Solution: Submit pre-development enquiries to the water company as early as possible — ideally before the planning application is submitted. This gives the water company time to respond and allows you to factor their requirements into the detailed design.

Timescales

The typical timescale for discharging drainage conditions is:

Stage	Typical Duration
Data gathering (surveys, infiltration testing)	2-6 weeks
Detailed drainage design	3-6 weeks
LPA/LLFA review (first round)	4-8 weeks
Amendments and re-submission (if required)	2-4 weeks
LPA/LLFA review (second round)	3-6 weeks
Total (straightforward)	8-12 weeks
Total (with amendments)	12-20 weeks

These timescales assume that the infiltration testing and water company enquiries have already been completed. If they have not, add the relevant time.

The Verification Report

An increasingly common requirement is a post-construction verification report. This is a document prepared after the drainage system has been installed, confirming that:

• The system has been built in accordance with the approved design
• All SuDS features have been constructed to the correct specifications
• Flow control devices are installed and functioning correctly
• The system has been tested and is performing as designed
• Any departures from the approved design have been documented and justified

The verification report is typically prepared by the drainage engineer who designed the system, based on information provided by the contractor (as-built drawings, test certificates, photographs).

How Aegaea Can Help

Aegaea’s civils team prepares detailed drainage designs for condition discharge across England, Scotland, and Wales. We handle the full process — from data gathering and infiltration testing through to detailed design, LLFA consultation, and post-construction verification.

We understand the specific requirements of different LLFAs and water companies, and we design drainage systems that are both technically robust and cost-effective. Our goal is to discharge your drainage conditions as quickly and smoothly as possible, so that construction can proceed without delay.

If you need to discharge drainage conditions on your planning permission, contact us for a no-obligation discussion and quote.