Halliwick Recreation Ground in Barnet experienced surface water flooding that affected the park itself as well as surrounding roads, properties and local infrastructure. Metis supported SuDS delivery on the Halliwick scheme, by contributing to the drainage design and acting as client representative during construction.

Barnet had identified the wider Muswell Hill area as one of the borough’s top priority Critical Drainage Areas, with historical flooding reports highlighting significant flood risk, including reported flooding in July 2021. To address this, Barnet brought forward a major SuDS delivery and landscaping project designed to divert runoff from nearby roads and the recreation ground into a detention basin in the north-eastern part of the park.

The intention was to reduce pressure on the Thames Water sewer network, lower flood risk to surrounding properties and infrastructure, and improve the park for the community. Metis’s role helped ensure the scheme was delivered safely, efficiently and in line with project objectives. We also supported coordination between design and delivery teams.

The Challenge

Halliwick Recreation Ground and the surrounding streets were affected by surface water flooding, putting nearby properties, roads and infrastructure at risk while reducing the usability of the park. Barnet needed a solution that would both manage runoff effectively and create broader social and environmental value within a well-used urban green space.

The challenge included:

• managing flood risk in a priority urban catchment with known historic flooding issues
• designing a SuDS solution able to intercept runoff from both surrounding roads and the recreation ground
• delivering construction works within a live public park in a mainly residential area
• coordinating drainage, landscape and stakeholder requirements through construction
• responding to technical changes, including foul drainage and utility-related design development, during the life of the project

Our Approach to SuDS Delivery

Metis provided targeted technical and construction-phase support to help Barnet successfully deliver this flagship SuDS scheme. Our role focused on practical design input, responsive construction support and close coordination with the wider project team. We also supported Barnet in obtaining Grant in Aid funding for the scheme.

Pre-construction and design development

Metis provided drainage design support as part of the wider Halliwick scheme development. Additional design tasks undertaken for the project included foul diversion layout and tender information, Thames Water Section 185 application support, InfoDrainage modelling for the SuDS and surface water network, Civil 3D modelling of pipe networks, long sections, plans, manhole schedule development and updates to Thames Water funding calculations.

This helped develop an integrated drainage strategy that:

• captures and stores rainwater on site
• reduces pressure on local drainage networks
• works with the natural landscape and park setting
• enhances biodiversity and public amenity

Construction phase support

During construction, Metis acted as client representative and provided weekly construction-phase design support. This included start-up and close-out meetings on site, monthly progress meetings with the contractor and client, project governance support and additional site visits where required.

Metis also supported coordination of design changes during construction. Final issue drawings were updated to reflect as-built drainage changes, including additional perforated land drains and drainage links discharging into the basin and swale arrangement.

The solution

The Halliwick scheme delivered a multi-functional SuDS and landscape enhancement project that is more than traditional drainage infrastructure. It combines flood resilience with improved ecological and community value.

Key features included:

• a new 3,500m³ flood water basin to capture and manage surface water runoff
• nature-based drainage solutions integrated into the landscape
• enhanced planting and habitat creation to support biodiversity
• improved pathways, furniture, access routes and recreational areas
• associated earthworks, meadow and lawn establishment, and wider public realm enhancements

Outcomes and value delivered

The Halliwick Recreation Ground scheme has been positioned internally as a flagship SuDS delivery scheme in Barnet. Benefits to local residents include:

• reduced flood risk to surrounding homes, roads and infrastructure
• improved resilience to heavy and extreme rainfall events
• creation of attractive, usable green space for the community
• increased biodiversity and ecological value
• better park access, usability and long-term community value

The SuDS delivery scheme demonstrates how sustainable drainage can protect communities, support nature and transform public spaces at the same time. Through design input and client-side construction support, Metis helped Barnet deliver a project that addresses flood risk while improving the quality and resilience of a valued urban park.

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