Project profile | How Tideway tunnels were delivered successfully

Tideway chief technical officer Roger Bailey believes that the undoubtedly successful construction of London’s super sewer – the 25km long Thames Tideway Tunnel – is largely down to early upfront collaborative decisions taken before construction began in 2016. 

When complete, the £4.2bn project will intercept, store and transfer sewage away from the River Thames between Acton in west London and take it to Beckton Sewage Works in east London.

Optimising contractor involvement

But to take the project from concept to reality, Tideway had to supervise three separate joint venture contractors and optimised contractor involvement was essential if productive harmony and long term performance were to be achieved.

“For example, we had to agree on the final system design,” says Bailey. “The project had invested in a major programme of hydraulic research, analysis and modelling, and we had a really robust design.

“Although these were design and build contractors, we strongly discouraged them from making major changes to our proposals. A few minor tweaks were agreed, but essentially the system as built is our original design.”

This was just one example of the early collaborative decisions that were to show their worth over the following seven years, Bailey adds. 

Safety has also been boosted by the collaborative approach. Back in 2012, when Bailey looked at the project’s potential toll of deaths and serious injuries compared to other major projects of Tideway’s scale, he was worried. “Even if we achieved what was then a good standard of health and safety, we could expect 200 life-changing injuries, 150 serious injuries and at least two deaths. This wasn’t acceptable,” he explains.

Working in or next to the river led to tunnelling materials being transported by barge

A collaborative workshop was held. “We asked a simple question: should the client set the safety standards, or should it be left to the individual contractors?” he says.

“The response from the contractors was unanimous – the client. And the client should police the standards.”

Tideway therefore invested heavily in the Employer’s Project Induction Centre (Epic), a whole floor of an office block in Vauxhall that was transformed into a series of rooms replicating building site situations. Here serious accident scenarios could be reenacted by professional actors with site staff watching the incidents unfold and witnessing their social impact, an approach that had a much more emotional effect than typical health and safety training.

Although there were never more than 3,000 operatives on site at one time, staff churn over the years meant that more than 30,000 shared the Epic experience. 

The result of Epic and other safety initiatives means the accident frequency rate on Tideway is lower than on comparable projects.

Around 90% of the spoil from the tunnelling went out by barge

At the planning stage one laudable ambition was to maximise the use of the Thames to transport materials into and out of the project. But when Tideway looked at the practicality, there was simply not enough market capacity to meet its needs.

Bringing in extra tugs and barges would be only a partial solution. The real bottleneck was the lack of trained operatives. Tideway’s answer was to set up a training and validation programme, which eventually produced a pool of 54 master marine operatives along with 49 mates. 

“We basically wrote a code of practice for the river traffic. As a result, around 90% of the spoil from the tunnelling went out by barge.” 

Tideway was acutely aware that the specified 120 year design life for the shafts and tunnels posed a real challenge. 

“This is a single system,” says Bailey. “It’s not like a rail line, where you can do repairs during overnight possessions.

“Any serious problems, with concrete durability, for example, could lead to a major shutdown with sewage overflowing back into the Thames.”

Tideway’s Epic safety training delivered an industry step change

Quality was monitored rigorously throughout the construction process. “Basically we set up a team of supervisors who were present on every site during every shift.” Bailey explains. 

“But we continued to work collaboratively. These are highly competent contractors with rigorous quality control procedures. Our job was to ensure they complied with these procedures, and work with them to sort any problems quickly. The final result was a very high quality finished asset.”

He adds: “The only real cause of delay was Covid, which cost us several months.

One major consideration right from the beginning was the impact the project would have on London before, during and after construction. “There was limited space for our shafts along the river. Some are on land, some in the foreshore,” Bailey points out. 

“That meant that for our main drive sites, some residents would have major construction operations in close proximity for several years.”

Stakeholder engagement

An exhaustive consultation and information exercise was launched. Measures were taken to minimise noise and pollution from the shaft sites. “We went the extra mile to be good neighbours,” Bailey says.

Tideway also looked beyond the project, to its impact on the public realm. “We aim to reconnect Londoners to the Thames,” Bailey adds. “There’ll be seven new riverside areas of up to 3ha open to the public.”

A clean, safe Thames will be the main attraction, for humans and wildlife alike. Sir Joseph Bazalgette’s 1865 sewer system may have been one of the wonders of the Victorian age when it opened. The new super sewer will return the Thames to a purity not seen since the early 19th century. Its impact on London will be as great as Bazalgette’s.

Heavy construction work is due to finish in 2023 with the project then going into its system commissioning phase, with full operational handover to Thames Water in 2025.

• Published in association with Tideway

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