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Slow progress delays work on London power tunnel

National Grid this week denied that work on its London Power Tunnels scheme to upgrade the capital’s electricity supply was running behind schedule.

But one of the tunnel boring machines (TBMs) has only progressed 2.5km since its launch 12 months ago.

The scheme recently celebrated the breakthrough of one of the project’s two TBMs - a 3m diameter dual mode Lovat machine named Evelyn - which has completed 3km of tunnelling since it was launched in March.

Slow progress

The other TBM - a 4m diameter earth pressure balance machine supplied by Herrenknecht, named Cleopatra - was launched on 21 September 2011. But according to a National Grid press statement it has currently only completed 2.5km of its 13km route.

At the time of launch National Grid said that Cleopatra was expected to drive at a rate of 120m per week, suggesting that a year into tunnelling the machine should have completed more than 6km.

Despite the lack of progress National Grid, the power infrastructure operator, has denied that the work is behind schedule.

“The project is due to be complete and operational by 2018 and we are on course to achieve this,” said a National Grid spokesman.

Main contractor Costain had still to comment as NCE went to press, while tunnelling subcontractor Skanska deferred to National Grid for comment.

Readers' comments (1)

  • The author's suggestion that a TBM can achieve a consistent 120m per week immediately after launch until completion of the drive shows a complete misunderstanding of the basic concepts of tunnelling.

    The TBM is likely still able to achieve the completion date the contractor's team will be aiming to go progressively faster as it construction continues.

    It is likely that Costain/Skanska would have for accelerating rates of production, for example, 1.5km in the first 6 months of the drive and 3km in the final 6 months. This would be standard industry practice.

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