A new approach to unlocking development in constrained catchments

Wealden District Council working with Southern Water have confirmed a new, evidence-based approach to managing foul drainage capacity constraints across the district. This emerging framework, developed following the Old Orchard, Horam appeal case, will enable some sites that were previously held up due to wastewater treatment capacity to move forward, provided they include on-site foul storage and controlled discharge measures.

ECE Planning Director Sam Sykes MRTPI recently attended a briefing session with Wealden planning officers to discuss how the new arrangements will work in practice and what they mean for developers and promoters active in the area.

Why this change was needed

Developers and local authorities across the South East have faced a planning paradox. Even where it has been widely acknowledged that wastewater treatment works were already at capacity, Southern Water rarely objected to new applications. This created uncertainty for both applicants and decision-makers: planning permissions were granted on the assumption that foul water could be accommodated, yet in reality, some networks were already under significant stress leading to environmental and operational risks.

Wealden District Council has challenged this position. Under this new arrangement, Southern Water are likely to now assess applications differently, across Wealden and it is likely the wider Sussex, Kent, Surrey and Hampshire areas, actively considering live network performance data when advising on capacity. This means that planning decisions can be made with clearer evidence about when and how new development can be safely accommodated.

The new foul drainage position

Wealden’s approach allows development in constrained catchments to proceed only where it can be demonstrated that the proposal will not worsen the existing position.

In practice, this will mean:

  • On-site storage tanks that temporarily hold foul flows during periods of high load at the wastewater treatment works.
  • A smart control system, linked to live network monitoring, allowing discharge only when the receiving system has spare capacity.
  • Layouts designed to allow tanker access, typically locating the tank within landscaped or open space areas.
  • Engagement with Southern Water at an early stage to agree potential adoption and technical parameters.

Published guidance is available on the Wealden District Council website including worked examples.

What this means for developers and land promoters

This new foul-drainage requirement represents a significant policy shift for the district and wider region and one that is highly likely to influence how Southern Water and other local authorities manage similar constraints elsewhere in Sussex and the South East.

Developers should now consider:

  • Increased technical and construction costs associated with on-site storage and monitoring;
  • Layout implications to accommodate the required infrastructure;
  • Potential viability impacts, especially for smaller and SME developers who may find the cost proportionally higher; and
  • Affordable housing implications, where increased infrastructure costs could affect scheme deliverability.

While this new approach provides a way forward for stalled sites, it is clear that wider strategic investment will still be required. We are aware that a pilot work at Uckfield may explore a pooled-funding model for earlier improvements than those identified by Southern Water in their five year rolling Asset Management Period plans.

ECE Planning’s role and insight

ECE Planning are currently advising on a number of live projects within Wealden District and across Sussex, Surrey, Hampshire and Kent where wastewater constraints are a key issue. Our role is to help clients interpret emerging policy, engage early with water companies and planning authorities, and ensure that drainage solutions are deliverable, proportionate, and policy-compliant.

We’ll continue to monitor the rollout of this framework and the forthcoming Local Plan policy updates, keeping our clients informed of practical implications for site promotion, viability and affordable housing delivery.

Shaping places across Sussex and the South East

ECE Planning are RTPI Chartered Town Planners with extensive experience across Sussex, Kent, Hampshire, Surrey, London and the wider South East.

Our work combines planning insight with technical understanding,  helping developers and local authorities unlock complex sites in a changing infrastructure landscape.

Contact our Planning Team to discuss how we can support your next project.

View Our Planning Services and find out how to Contact Us here.