Tideway ‘super-sewer’ final cost holds steady at £4.5bn


The cost to deliver the Thames Tideway Tunnel remains at £4.5 billion, after the total sum was revised up in April. 

Credit: Tideway.

Tideway, the company behind the 15-mile ‘super-sewer’ infrastructure in London, said the cost of delivery was consistent with its revised estimate revealed earlier this year, as part of the company’s latest annual report. 

Thames Tideway Tunnel
Tideway chief executive, Andy Mitchell. Credit: Tideway.

It comes amid reports Tideway CEO, Andy Mitchell, received a £2.2 million bonus in the last financial year, compared to £421,000 the previous year.   

Started in 2016, construction had been aimed for completion by next year, but was rescheduled owing to delays brought about by the pandemic.   

The major works project had, in 2014, initially been costed at around £3.5 billion.   

Earlier this year, however, the estimate was revised after factoring in the remaining works programme and the cost of inflation.  

Most of the construction work and underground works are now complete, said Tideway, and the company is preparing to commission the new infrastructure in 2024. 

The tunnel is due to be fully operational under Thames Water in the second half of 2025, at which point it could capture up to 95 per cent of overflows from London’s sewerage network, improving the water quality of the Thames, and the environment. 


  • VINCI Construction Grands Projets, Bachy Soletanche, Costain (JV)   
  • Ferrovial, Laing O’Rourke (JV)   
  • Balfour Beatty, Morgan Sindall, Bam Nuttall (JV) 

“The past 12 months on the Tideway project have seen the most significant change in focus since we started work – with the construction phase nearing completion and attention turning to testing this new and vital infrastructure,” said Tideway chairman, Sir Neville Simms.       

“As we look forward to bringing the system on-line next year, our delivery model – which encourages long-term private investment in infrastructure – is showing its worth in delivering value for all stakeholders.” 

Mitchell added: “Awareness of the health of our waterways and our environment has never been higher than it is today, and so I am pleased to report that London is closer than ever to a cleaner, healthier River Thames.” 

Enjoyed this? Try More than 600 ex-staff take legal action against ilke Homes 

Get industry news in 5 minutes!

A daily email that makes industry news enjoyable. It’s completely free.