Covid19 restrictions have added a further £233 million to previous cost estimates for the Thames Tideway supersewer project, putting the overall cost of the project at £4.133 billion, while completion has been delayed by 9 months.

News of the revised forecast and delay were revealed in an operational update to investors published yesterday by Bazalgette Finance plc for Bazalgette Tunnel Ltd, trading as Tideway, the company delivering the Thames Tideway Tunnel, following an assessment of the impact of the COVID-19 pandemic on its operations.

The company's latest modelling indicates construction work, which was due to be completed in 2024 (the project 'handover' date), is now likely to be completed in the first half of 2025, adding nine months to its current schedule.

The approved revised forecast adds £233 million to the previous forecast, taking the estimated project cost to £4.133 billion.

Tideway is currently in discussions with Ofwat on a package of measures that would mitigate the financial impact of COVID-19 on the company.

Project promoter Bazalgette Tunnel Ltd, Thames Water’s development vehicle for the project, commented:

“We are making progress in these discussions and we expect to reach a full agreement in the coming months.“

Following a temporary pause of all but essential works at the start of the UK lockdown, construction work recommenced on the majority of the company's worksites in May, albeit at a lower level of activity in order to comply with social distancing requirements.