Ofwat has announced that it is pushing back the Planned System Acceptance Date for the Tideway Tunnel from 28 February 2027 to 31st August 2027 - the date at which the operation of the Thames Tideway Tunnel (TTT) is handed over to Thames Water.

Ofwat explained that the change is considered necessary because if there is a delay to the project and acceptance of the completed asset is not achieved by the Planned System Acceptance Date, Tideway will incur a penalty for the delay.

Currently, the weighted average cost of capital (WACC) that applies to the project was set in the initial competitive bidding process for the project. If the Acceptance Date is delayed beyond 28 February 2027, the Bid WACC will decrease by 1% from that date.

According to the regulator, Covid had impacted the TTT project far more extensively than for any other water or sewerage company, leading to delays in construction and a consequent increase in costs for Tideway.

The three main drive sites, which are all brownfield and at least half the size of a typical “efficient” tunnelling site because of the central London location, faced significant operational constraints.

By way of illustration, the drive sites are 10 times smaller than the HS2 tunneling sites for smaller diameter tunnels.

Setting out its reasons for modifying Tideway's licence to change the date, Ofwat explained it felt that “Tideway managed the disruption caused by Covid-19 well and that they acted for the benefit of the project in a situation that was largely beyond their control.”

Ofwat said has also engaged extensively with Tideway in order to satisfy itself that Tideway was able to differentiate Covid-19 related delay from other delay, commenting:

“We are now satisfied that Tideway has provided sufficient evidence that Covid-19 was the sole cause of five months of delay to the project.”

Ofwat has however, agreed to change the Planned System Acceptance Date by six months, rather than five months to correct an administrative delay that occurred when the licence was first granted in August 2015.

Work started on secondary lining for final, eastern section of super sewer

The final, easternmost section of London’s new super sewer is now having its secondary lining installed, following the completion of the primary lining in April.

Secondary lining will continue on the final 5.5km stretch of the tunnel between Bermondsey and Abbey Mills Pumping Station into next year.

Primary lining was completed for the entire super sewer back in April – now, with much of the secondary lining elsewhere complete, the team at Chambers Wharf has begun the final, easternmost stretch.

The secondary lining is required to provide added strength to the tunnel to ensure the super sewer can do its job for generations to come, while providing a smooth surface over which the sewage flows can travel when the tunnel is up and running in 2025.

Tunnelling work on the super sewer started in 2018, with more than 90% of the excavated spoil removed to create the tunnels removed from site by barge. Now constructed, the tunnel runs 25km from east to west London and at its deepest is around 70 metres deep.

The Tideway project is due to be completed in 2025, following secondary lining, connection and testing works.

Sir Neville Simms, Chair of Tideway described completion of tunnelling as “testament to the hard work and contributions of thousands of people and organisations, over many years.”

To date, the Tideway project has seen the creation of more than 4,000 sustainable jobs and more than 100 apprenticeships across the UK.