Attenuation basin: how we supported Kingston-upon-Thames’s LLFA duties

Metis successfully delivered a flood alleviation scheme for Sir Francis Barker Recreation Ground, on behalf of the Royal Borough of Kingston-upon-Thames Lead Local Flood Authority.

The scheme comprised an attenuation basin and improved drainage connections from a nearby ditch. These took flows from a surface water catchment that had been causing flooding to the recreation ground and nearby residential properties.

Building on an earlier detailed design, we refined, coordinated and finalised the project into a complete construction‑ready package. We also supported its delivery on site. The completed scheme now provides improved surface‑water management, enhanced usability of the recreation ground, and long‑term resilience for the local community.

The Challenge

The recreation ground and nearby properties had suffered from recurring flooding, driven by an outdated and inefficient drainage system. Stakeholder feedback highlighted several important issues that needed to be resolved through the design process, including:

• Improving connectivity to the existing drainage infrastructure
• Reducing overland flow from the recreation ground overwhelming existing drainage networks and causing flooding to properties
• Relocating excavated material to avoid conflicts with sports pitches
• Enhancing safety and privacy around the children’s play area and attenuation basin
• Protecting established trees and integrating landscape changes sensitively
• Establishing a robust maintenance plan for the new drainage system

The project required coordinated civil engineering and landscape design, along with careful management and engagement with key stakeholders.

Our Approach

Collaborative Project Governance

Metis undertook the role of Principal Designer for the scheme, in line with Construction Design and Management regulations. We put in place a clear governance framework, working closely with the Kingston LLFA, Green Spaces Team, the Recreation Ground Management Committee, BDP, Thames Water and FM Conway throughout the project. Regular online and on‑site meetings ensured smooth progression through design, approvals and construction.

Ground Investigations

To validate ground conditions, we specified and oversaw a programme of ground investigations that were undertaken by FM Conway. The findings informed construction methods, material selection, and costings, and ensured the final design responded directly to on‑site conditions.

Refinement of the Civils Design

We reviewed the detailed design issued in 2023 and incorporated all feasible stakeholder feedback. This included:

• Improving drainage performance and connecting existing ditches
• Identifying suitable locations for re‑use of excavated material
• Addressing privacy and safety concerns between the play area and attenuation basin
• Working with BDP to integrate landscape requirements
• Relaying the tennis court in the recreation ground and directing flows away from this area
• Updating all drawings in line with MCHW standards

The updated design received client approval following one coordinated review cycle.

Thames Water Coordination

We led all technical liaison with Thames Water, including sewer diversion and abandonment requirements. The team produced legal agreement drawings, calculations and coordinated technical approvals, enabling construction to proceed without delay.

Delivery of the Construction Pack

Following approvals, we delivered a full construction‑ready package, including:

• Final engineering drawings and specifications
• Setting‑out information
• Risk registers and hazard elimination logs
• Health & Safety constraints drawings
• Editable source files for future reference

This ensured FM Conway had all the information needed to deliver the works efficiently on site.

Maintenance Schedule and Bill of Quantities

A tailored drainage maintenance schedule was prepared to support long‑term asset care. We also developed a “blank” Bill of Quantities using FM Conway’s Term Maintenance Price List, supporting accurate cost planning and procurement.

Principal Designer Role (CDM 2015)

We acted as Principal Designer throughout the pre‑construction, construction and handover stages. This included preparing pre‑construction information, managing design risks, attending regular site and progress meetings, and completing the final Health & Safety File at project close.

Outcomes

The completed scheme now provides:

• Reduced flood risk across the recreation ground
• A significantly improved and more reliable drainage system
• Safer and more accessible play and sports facilities
• Sensitive landscape integration and protection of existing assets
• A clear maintenance framework for long‑term performance

The project has delivered a more resilient, functional and enjoyable recreation space for local residents. This strengthens Kingston’s wider flood risk management strategy.

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