Tideway, the company building London’s new super sewer, has completed 40 percent of construction and is on track to deliver the project on time in 2024.

Five years since the project was given the green light Tideway is now updating its estimate of overall costs based on work left to do. With the first and most unpredictable phase of the project now complete, the Company’s revised estimate is GBP 3.8 billion (US$ 4.98 billion) compared to GBP 3.52 billion (US$ 4.62 billion) [GBP 3.14bn (US$ 4.12 billion) in 2014 prices] which represents an eight percent increase.

There will be no change to the estimated GBP 20-25 annual cost for Thames Water bill-payers, as costs remain well within the original projection for customer charges. The company has already raised enough money to complete the project and requires no further funding as a result of this cost revision.  

The tunnel, which will run from Acton in west London to Stratford in east London, will extend London’s Victorian sewer system, stopping millions of tonnes of raw sewage polluting the Thames.

Construction is taking place at 23 sites across the city and Tideway is using the river instead of roads as far as possible to build the project, cutting the impact on road congestion and air quality. By the end of April 2019, one million tonnes of material will have been moved by river – keeping 60,000 HGV movements off London’s roads so far.

Earlier this year, Tideway announced it had avoided the need to divert a Victorian gas main at Blackfriars, one of its most complex sites. The diversion would have meant a closure of the Embankment to traffic for up to six months. To avoid the diversion, Tideway had to make fundamental changes to the construction methodology for the site, adding costs to the original estimate.

At Tideway’s King Edward Memorial Park site in Wapping the team found difficult and unexpected ground conditions which meant they have had to do significant work to reinforce the ground to make it stable for construction, also adding cost.

Tideway also took the decision to reduce HGV movements, which required additional investment in the infrastructure needed to move materials by river, as well as investment in skills and jobs through the new Thames Skills Academy. This will cut the number of lorry movements by 360,000, reducing impacts on congestion and air quality.