Understanding the Design Process for Achieving Compliance with Local Sewer Authorities

When undertaking new developments, whether residential or commercial, communication and approval from local sewer and water authorities is a critical step. Authorities such as Thames Water, Anglian Water, or Southern Water have structured processes to ensure that new developments align with existing infrastructure capacity and do not exacerbate flood risks.

In this blog, we outline the key steps in the approval process, breaking down how you can navigate sewer authority compliance with ease.

Why Sewer Authority Approval is Essential

The primary role of sewer authorities is to maintain the integrity of their networks and ensure development does not increase the risk of flooding. While they have a legal responsibility to facilitate development, authorities regulate how much and at what rate surface and foul water can be discharged into their network.

Even for smaller developments, such as single homes, approval is necessary. For larger projects like apartment complexes or commercial developments, the same process applies, albeit with potentially stricter scrutiny. While authorities cannot outright refuse a connection, they can dictate discharge rates to safeguard their infrastructure.

The General Approval Process: Step-by-Step

Step 1: Pre-Development Inquiry

The first step involves understanding the development’s impact on the sewer network and applying for capacity. This is referred to as a pre-development inquiry. Here's what this entails:

• What You Submit: Information about the development, including proposed surface and foul water discharge rates, is submitted to the sewer authority. You must demonstrate how runoff will be managed.

• The Greenfield Runoff Rate: Authorities typically require surface water discharge rates to align with the natural infiltration rate of undeveloped land. For Brownfield sites, a discharge rate of 1-2 liters per second is often required.

• Follow the SuDS Hierarchy: You need to demonstrate compliance with the Sustainable Drainage Systems (SuDS) hierarchy. This involves prioritizing methods like infiltration (e.g., soakaways) before considering connection to a sewer.

The sewer authority will review your inquiry, determine the permissible discharge rates, and provide guidance on the next steps.

Step 2: Detailed System Design

Once the pre-development inquiry is complete, use the feedback to design detailed surface and foul water management systems. This step includes:

• System Design: Incorporating the permissible discharge rates into your surface water drainage and foul water systems.

• Integration with SuDS: Ensuring compliance with SuDS best practices, such as rainwater harvesting, permeable paving, and infiltration systems.

Step 3: Connection Application (Section 106)

After completing the detailed design, the next step is to apply for permission to connect to the sewer network. This is done through a Section 106 Connection Application, which includes:

• Connection Type: Whether you’re connecting to an existing manhole, providing a new direct connection, or constructing a new manhole.

• Associated Fees: While pre-development inquiries are free in some cases (e.g., Thames Water), connection applications typically have fees based on the type of connection.

• Detailed Plans: Submit plans showing the connection point, discharge rates, and proposed works. The sewer authority will review, comment, and issue a connection approval.

Step 4: Construction and Inspection

The final step involves implementing the approved connection. Here’s how it works:

• Contractor Management: A contractor will carry out the works as per the approved plans.

• Inspection: Before backfilling the connection, the sewer authority inspects the work to ensure compliance.

• Completion Certificate: Once satisfied, the authority issues a completion letter, which becomes part of the development's documentation.

  
  

Key Considerations

• Mandatory Application: Even if a development reduces flow rates, you still need to submit a connection application since it alters discharge patterns.

• Impact on the Sewer Network: Sewer authorities use your application to update their network models, ensuring future capacity planning.

  
  

In Summary

From small residential projects to large commercial developments, achieving compliance with local sewer authorities is a structured but essential process. By following the steps outlined—pre-development inquiry, detailed design, connection application, and construction—you can ensure your development is aligned with local infrastructure requirements and avoids delays.

Need help navigating the sewer authority compliance process? Contact us today, and we’ll guide you every step of the way.