Regent Street flyover, Leeds, UK

NEC contracts have been used to procure a major flyover replacement in Leeds city centre, UK. The original 1960s structure carried the A64(M) New York Road motorway over the A61 Regent Street dual carriageway via a pair of 100 m long, three-span post-tensioned concrete bridges. With traffic exceeding 40,000 vehicles a day, the bridges had reached the end of their useable life. 

Client Leeds City Council let the demolition and reconstruction work to Balfour Beatty in July 2020 through the Scape civil engineering framework under an NEC4 Engineering and Construction Contract (ECC) Option C (target contract with activity schedule). The contractor engaged its designer WSP under an NEC4 Professional Service Contract (PSC) and subcontractors under NEC4 Engineering and Construction Subcontracts (ESC). Leeds City Council was the NEC project manager. 

The work involved removing and rebuilding each flyover bridge separately so as to keep one carriageway operational throughout the contract. Great care was needed with cutting out the post-tensioned concrete beams just 50 mm away from the adjacent carriagway. Each cut section was lifted onto self-propelled modular transports and broken down for recycling, with only 0.33% going to landfill.

After demolition during weekend closures, new reinforced concrete piers, cross-heads and abutments were built on top of existing piles and the west spans were infilled. A total of 12 braced pairs of steel plate girders measuring 46 m and 31 m long were then lifted into position using a 1000 t crane and bolted together to create two new 76 m long, twin-span bridges. Reinforced concrete decks, road surfacing and street furniture were installed and the bridges re-opened to traffic. 

Despite challenges such as the Covid-19 pandemic, the insolvency of the main steelworks contractor and changes to the scope, the second 120-year-design-life bridge was opened to traffic in May 2022 and the contract was completed on time and within budget in March 2023. The project was shortlisted both for Upgrade and Renewal Project of the Year and Transport Project of the Year in the 2022 British Construction Industry Awards. 

Collaborative working

Leeds City Council principal engineer Robert Ingall says the NEC requirement to work in a, ‘spirit of mutual trust and co-operation’ was fully embraced by the project team. ‘NEC-inspired collaboration started from the outset of the detailed design and early contractor involvement phase in June 2019. Working as a single team in a shared open-plan office space fostered trust, transparency and information sharing.’

As well as carefully planning the construction programme using digital models, he says the team adopted modern methods of construction to do as much fabrication off site as possible. ‘Approaches such as bringing in sections of the bridge with temporary works and deck elements already in place helped to keep the project on track despite the unforeseen circumstances of the Covid pandemic.’

Robert Ingall says ECC Option C was chosen to reflect the nature of the heavy civil engineering works and risk profile associated with the scheme. ‘We recognised the importance of the programme to managing the works given the constraints of working in the city centre and the need to be able to accommodate change.’

Risk management

He says ECC Option C was ideal for the scale and complex risk profile of the scheme. ‘Our focus from the earliest stages was on collaborative risk management, which recognised the contractual ownership of risk but assigned owners for each risk based on their ability to mitigate it’. 

Robert Ingall says the open-book nature of the ECC Option C target cost arrangement and the NEC early warning process provided full visibility of defined cost. ‘This allowed the team to manage the target cost proactively through early dialogue around the impact of actual and potential changes.’ 

He says the client worked closely with the contractor to establish the impact of changes on the programme and ultimately deliver the project on time. ‘Despite events such as the onset of the Covid-19 pandemic in March 2020 and the insolvency of the steelworks supplier in September 2021, the second flyover bridge was successfully re-opened to traffic on schedule in May 2022.’ 

Allowing for completion of some additional scope, such as upgrading drainage systems along the A64(M), Robert Ingall says the contract was completed on programme in March 2023 and within the client’s overall budget. ‘The project has been a great success. A large structure supporting a major arterial route into the city centre has been replaced from a standing start to completion within just 3 years.’

Benefits of using NEC

• NEC requirement to work in a, ‘spirit of mutual trust and co-operation’ was fully embraced by the project team, leading to collaborative working from the outset. 
• NEC-inspired collaboration in the detailed design and early contractor involvement phase helped to ensure a very detailed and achievable construction programme.
• ECC Option C enabled risk to be assigned to those best able to manage it, working as a single team in a shared open-plan office space.
• NEC open-book nature and early warning process allowed the team to manage the target cost proactively and keep within the client’s budget despite significant challenges to the project.