Construction of London’s NEC-procured ‘super sewer’ now complete

The NEC-procured Thames Tideway Tunnel in London was structurally completed in March 2024. The eight year works programme ended with lifting a 24 m diameter concrete lid over a new 70 m deep shaft at Abbey Mills pumping station at Stratford, allowing commissioning to begin.

The 25 km long 7.2 m diameter tunnel, the biggest project ever undertaken by the UK water industry, was split into three main contracts: west, central and east. Each was let by Thames Water’s infrastructure provider Tideway in February 2015 under an NEC3 Engineering and Construction Contract (ECC) Option C (target contract in activity schedule) with 50/50 pain/gain share arrangements.

The total estimated value of the three contracts when tendered was £1.4–£2.25 billion. The project has since faced the challenges of Brexit, Covid and global inflation, such that total project cost has risen from £4.1 billion to £4.5 billion. Following successful commissioning, the tunnel will be fully operational in 2025.

Collaborative behaviour

Stewart Foster, Tideway’s head of contracts, said: ‘By using the NEC3 ECC Option C target cost contracts for its main works contracts, the Tideway project has been able to drive collaborative behaviour between all parties very effectively.

'The Tideway project has also been able to focus performance through the use of effective mechanisms that reward both timely contract administration and delivery of works as well as being able to provide flexible and powerful incentives.

‘The NEC has provided a bedrock upon which the Tideway project has delivered a complex programme of works in the middle of a capital city whilst navigating such events as the Covid-19 pandemic, the UK’s exit from the EU, and managing a supply chain of hundreds of subcontractors and suppliers.’

The main works contractors were all joint ventures of major international construction companies. The west section was undertaken by BMB, a joint venture of BAM Nuttall, Morgan Sindall and Balfour Beatty; the central section was built by FLO, a joint venture of Ferrovial Agroman and Laing O’Rourke; and the east section was carried out by CVB, a joint venture of Costain, Vinci and Bachy Soletanche.

Systems integration and supply

Tideway also used NEC for systems integration and supply contracts. The main systems integration contract was awarded to Amey under a £10–15 million NEC3 ECC Option E (cost-reimbursable contract) in 2015. The six tunnel-boring-machine supply contracts were let using NEC3 Supply Contracts (SC) worth an average of £15 million each, also in 2015. Three were to Herrenknecht in Germany, two were to NFM Technologies in France and one was to Morgan Sindall in the UK (see NEC case study).

Former programme director Andy Alder said, ‘the NEC3 Supply Contract encouraged the right philosophy to deliver these high-risk, high-profile subcontracts collaboratively and therefore efficiently. NEC’s use of simple English has supported its application for the procurement of the TBMs with international suppliers without the need of costly legal intervention.'