Silvertown Tunnel cost rises by £2m

The cost of the Silvertown Tunnel has crept up again, this time by £2m to £179m, according to Transport for London (TfL).

The cost overrun and delay have been revealed in an agenda document for TfL’s next Programmes and Investment Committee meeting on 5 October.

At the previous committee meeting in July, the estimated final cost (EFC) of the project stood at £177m. The new £179m EFC is, however, down from the EFC of £186m forecast earlier this year. TfL managed to bring the forecast down by £9m in the middle of the year through reduction in risk exposure.

According to the agenda document, the EFC is currently £6m over the approved sum of £173m, “owing to inflation increases and the agreed safe stop undertaken because of the coronavirus pandemic”.

The latest £2m increase was “due to a reassessment of some of the key risks, which are being managed and mitigations developed”. TfL said it is looking for “opportunities to reduce cost and risk exposure, which should be achievable to bring us back in line with the [approved sum]”.

As it stands, £117m has been spent on the project with a further £62m currently estimated to be needed to bring the tunnel to completion.

Meanwhile, the opening date of the 1.4km Thames tunnel has been pushed to the second quarter of 2025/26, from the first quarter.

The planned completion date has slipped 18 days, just into the second quarter of 2025/26, following “a change in programme sequencing to allow for equipment installation to take place after the removal 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 bring the permit to use back into Q1 as per previous reports”.

Mitigations are underway to allow for some parts of the TBM to be removed through Greenwich rather than Silvertown. These have already reduced the potential impact of the equipment installation from 49 to 18 days.

In terms of the programme, the TBM reached the rotation chamber in Greenwich in February 2023, completing the tunnelling of the first bore. Following a complex but successful rotation, it started the final leg of its journey in May and completed its drive in July, 62 days ahead of plan.

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Source: Construction News

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