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Tue August 16 2022

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Super sewer could deliver threefold return

6 Nov 15 Construction of the Thames Tideway Tunnel, London’s so-called super sewer, will deliver a two- or threefold return, according to latest government analysis.

The Department for Environment, Food & Rural Affairs has published its cost benefit analysis of the Thames Tideway Tunnel project1.

It concludes that best estimate of the whole life cost of the 25km sewer is £4.1bn and the whole life benefits are somewhere between £7.4bn and £12.7bn.

Environment Minister Rory Stewart leapt upon the higher figure to justify the controversial project, and added a little on top.

“This new research reveals the tunnel will bring up to £13bn worth of benefits to the capital’s natural environment,” he said. “It will prevent millions of tonnes of sewage flowing into the river every year and it will mean we will have cleaner water for all to enjoy and improved water quality to better protect the Thames’ precious marine wildlife.”

Work on the tunnel is set to begin next summer and will update the capital’s 150-year-old sewerage system now operating close to capacity, resulting in sewage overflowing into the river on average once a week.

The project had been expected to have reached financial close by now. Bazalgette Tunnel Ltd, a consortium led by insurance group Allianz, was appointed in July to finance, build and own the Thames Tideway Tunnel.

Contractors have also been selected although no deals finalised yet. BMB JV (BAM Nuttall, Morgan Sindall and Balfour Beatty) have the West section; FLO JV (Ferrovial Agroman UK and Laing O'Rourke Construction) have the Central contract; and CVB JV (Costain Vinci Construction Grands Projects and Bachy Soletanche) have the East contract.  Construction is expected to start in 2016 and reach completion by 2023. (See previous report here.)

1. Thames Tideway Tunnel: strategic and economic case, costs and benefits, 2015 update is at

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