Nimbus Engineering Consultants was commissioned by Tokar Limited, with Derek Page as the primary contact, to provide a Flood Risk Assessment and Drainage Strategy report to support their planning application and deliver a comprehensive drainage solution for a proposed church development in Walberton.
This project demanded expertise in both foul and surface water management. We overcame significant site challenges to meet planning approval requirements within a constrained timeline.
Project Overview
- Project: Church Development – Walberton
- Client: Tokar Limited
- Architect: Knight Consulting – Amy Sign, Point of Contact
- Local Authority: Arun District Council
Foul Drainage Design and Strategy
At Nimbus Engineering Consultants, we specialise in delivering tailored drainage solutions that meet each project’s unique demands.
For this church development, designed to accommodate 340 persons, our team engineered a robust foul drainage system. This system effectively directed wastewater from discharge points to a large-capacity wastewater treatment plant.
Following initial treatment via the wastewater treatment plant, the water was purified through a reed bed system before being safely discharged into a nearby pond, ensuring compliance with local environmental standards.
Surface Water Management and SuDS Integration
In alignment with sustainable development practices, our surface water management and SuDS strategy incorporated overground attenuation features, contributing to on-site Biodiversity Net Gain (BNG).
We designed a 1-meter deep SuDS pond to provide the first level of surface water treatment. The runoff was then filtered through a gravel trench, offering an additional purification layer before being released through a controlled flow chamber at a rate equivalent to greenfield runoff rates. This design mitigates flood risks and enhances the site’s ecological value.
Site Challenges and Solutions
During the initial site investigation, we identified significant challenges related to surface water management. Nearby sites used infiltration as their primary method for managing surface water runoff, so we initially carried out BRE365 tests to assess the feasibility of this approach.
However, all tests conducted across the site failed due to near-stagnant infiltration rates, indicating that infiltration was not viable.
With no nearby public drainage assets available, we focused on utilising the nearby pond for discharge. This approach presented another challenge: proving that the pond was hydraulically connected to the surrounding watercourses and discharged into a flowing river.
The maps the Environment Agency (EA) used did not clearly show these connections. However, with the client’s assistance, we provided photographic evidence demonstrating that swampy areas, which connected various ponds, were part of a continuous system. Additionally, a culvert that the EA did not map was identified, confirming the hydraulic connection required for our drainage strategy.
Achieving Planning Approval
Our thorough and strategic drainage design and the resolution of site challenges played a pivotal role in addressing the Arun District Council’s initial objections.
Thanks to our proactive approach and detailed planning, the local authority recommended the project for approval at the September committee meeting, highlighting our capability to navigate complex regulatory landscapes.
Collaboration and Project Management
Nimbus Engineering Consultants prides itself on a collaborative approach to project management. Throughout the development, we worked closely with Tokar Limited, Knight Consulting, and other stakeholders to deliver the project on time and within budget. Our commitment to regular communication and on-site problem-solving was critical to the project’s success.
Following the approval of the Flood Risk Assessment and Drainage Strategy report for this project at planning, the client has now asked us to provide further detailed design to discharge the SuDS planning condition via a more detailed SuDS design, SuDS report and Foul Drainage Strategy report and detailed design.
Conclusion and Further Assistance
This case study demonstrates Nimbus Engineering Consultants’ expertise in providing innovative and compliant drainage solutions within tight deadlines.
If your project requires specialist Flood Risk support or drainage engineering consultancy, including SuDS and surface water management, please contact us at info@nimbusengineering.co.uk or fill out our contact form.