The cost of the Silvertown tunnel has risen again, this time between £2m and £179m, according to Transport for London (TfL).
The cost overruns and delay have been revealed in an agenda paper for the next meeting of TfL’s Programs and Investments Committee on October 5.
At the committee’s previous meeting in July, the estimated final cost (EFC) of the project was £177 million. The new EFC of £179m, however, is lower than the £186m EFC forecast earlier this year. TfL managed to reduce the forecast by £9m by mid-year by reducing risk exposure.
According to the agenda paper, the EFC is currently £6m above the agreed sum of £173m, “due to increases in inflation and the agreed safe shutdown due to the pandemic of coronavirus”.
The latest £2m increase is “due to a re-assessment of some of the key risks, which are being managed and mitigations are being developed”. TfL said it is looking for “opportunities to reduce costs and risk exposure, which should be achievable to bring us back in line with the [approved sum]”.
As it stands, £117 million has been spent on the project and it is currently estimated that an additional £62 million is needed to complete the tunnel.
Meanwhile, the opening date for the 1.4km Thames Tunnel has been brought forward to the second quarter of 2025/26, from the first quarter.
The planned completion date has passed by 18 days, right into the second quarter of 2025/26, following “a change in program sequencing to allow equipment to be installed following the withdrawal of the tunnel boring machine (TBM) “.
However, both TfL and contractor Riverlinx, a joint venture between Bam Nuttall, Ferrovial Construction and SK ecoplant, “are working hard to return permission to use in the first quarter, according to previous reports”.
Mitigations are being undertaken to allow parts of the TBM to be removed via Greenwich instead of Silvertown. These have already reduced the potential impact of equipment installation from 49 days to 18 days.
On schedule, the TBM arrived in the Greenwich rotary chamber in February 2023, completing the tunneling of the first hole. After a complex but successful rotation, it began the final leg of its journey in May and completed its journey in July, 62 days ahead of schedule.
