Navigating planning requirements for multi-unit residential developments requires a precise surface water management strategy. Nimbus Engineering recently worked with a client in Horley, Surrey, to deliver a comprehensive SuDS Report and drainage design, successfully securing outline planning permission for a 22-dwelling development.
Project Overview
Nimbus Engineering Consultants were commissioned by Christine Muir to provide a SuDS Report and SuDS Assessment to support a planning application for the construction of 22 dwellings, with associated landscaping areas and roads at Three Acres, Horley, Surrey.
Scope of Work & Expert Details
Our civil engineering team provided a complete surface water management strategy, from initial site investigations to final hydraulic design to satisfy Surrey County Council. The technical work undertaken included:
- Conducting on-site BRE365 percolation testing and site walkovers to definitively assess infiltration feasibility.
- Performing detailed topographical level assessments and a ditch condition survey to confirm the viability of a gravity-fed discharge system.
- Designing a complex SuDS management train using sustainable surface water drainage features, including raingarden planters, filter drains, and attenuation tanks.
- Executing hydraulic calculations to ensure the final discharge to the adjacent watercourse was strictly restricted to the required greenfield run-off rate.
BRE365 Infiltration Testing & Site Assessment
We were initially asked to assess the feasibility of infiltration at the site and carried out BRE365 infiltration testing to establish whether source control methods of SuDS would be viable.
Unfortunately, infiltration was not a viable option at this site. However, due to the presence of a ditch on the site, we were able to identify a suitable alternative means of surface water disposal.
As the ditch was fairly shallow, we needed to ensure that gravity discharge was achievable. We therefore carried out a rigorous levels assessment from the ditch to confirm that all upstream SuDS assets were also shallow enough to make this approach viable without the need for pumping stations.
Following the SuDS Management Train
We ensured a high level of water treatment was provided for all surface water run-off through a combination of raingarden planters, raingardens, and filter drains, prior to attenuation in two large underground attenuation tanks.
This was followed by final storage and treatment in a large raingarden before discharge to the adjacent ditch by gravity at the required greenfield run-off rate, ensuring full compliance with local and national planning policies.
Client Testimonial & Outcome
Christine was a pleasure to work with and kindly provided the following testimonial regarding our work on the project:
“Sadia and her team responded quickly and with diligence when time was of the essence due to Council deadlines, leading to a successful result in gaining outline planning permission. I would not hesitate to come back to Nimbus in the future.”
— Christine Muir
Need a SuDS Report or Drainage Strategy?
Nimbus Engineering specialises in producing planning-ready SuDS Reports, drainage strategies, and Flood Risk Assessments across the UK.
If you require a SuDS Report for a residential development, commercial site, or planning application, contact Nimbus Engineering Consultants for professional, compliant, and cost-effective drainage design solutions.
