First major Tideway award

12 January 2010

Concerns amongst the British tunnelling community about rumoured delays in progress in Thames Water’s Tideway project will be alleviated to some extent by the announcement of the first major tunnelling contract. As T&TI went to Press, Thames Water named the MVB joint venture (comprising Morgan Est, Vinci Construction Grands Projets and Bachy Soletanche) as preferred partner for the £400M (US$647M) design-and-build contract for the Lee Tunnel. The tunnel will run from the River Lee at Abbey Mills Pumping Station to the Beckton Sewage Treatment Works on the north bank of the River Thames, east London.

It was feared that no award would be made before Christmas, although construction work will still not commence until April 2010 (originally scheduled for January) with scheduled completion by the end of 2014. The project aims at complying with the EU Urban Waste Water Treatment Directive by intercepting untreated storm-water/sewage flows that enter the River Lee at a single point at Abbey Mills at times of high rainfall and transferring them for treatment at Beckton Sewage Treatment Works (STW).

Work covered by the contract includes the 6.9km-long, 7m i.d. Lee Tunnel, two 25m-i.d. shafts and a 20m-diameter shaft (one at Abbey Mills Pumping Station and two at Beckton STW for pumping and overflow), plus a 38m-diameter pumping station shaft to allow the main Tideway Tunnel to link to the Beckton STW. Associated work will include the installation of pumping and associated equipment in the shafts for effluent management to lift it up to 80m.

The Lee Tunnel route is to be between 65m and 75m in depth and has to pass under the Jubilee and District Lines of Transport for London, the Essex suburban main railway, and main cable tunnels near the Abbey Mills end. It is understood that both of the final bidders for the contract were being expected to draw up designs for the project in exchange for separate fees, thus avoiding further delays after the final contract award whilst the design was drawn up by the winning contractor.

The losing shortlisted contractor is a JV of Murphy and Hochtief, whilst a Laing O’Rourke/Impregilo joint venture, plus FCC of Spain, also shortlisted, had been counted out of the running in June. Morgan-Est had a major advantage with the availability of its nearby precast concrete works at Ridham, which recently completed supplies for the Belfast Sewers Project.

The Tideway tunnels are planned to have a 350mm thick precast segmental primary lining and a 400mm thick cast in situ secondary lining, using fibre-reinforced concrete for the segments in the reference design to cope with high external groundwater pressures and high internal pressures at times. The design life is 120 years.

Spokespersons for Thames Water had been denying that tying in the proposed Tideway Tunnel into the Lee Tunnel was a cost-saving measure brought about by budget scheduling problems due to over-runs in other capital projects. The rumours increased concerns among tunnelling engineers that the Tideway project would be delayed, causing a hiatus of some 12 months in tunnelling activity after completion of Crossrail. The Thames Tunnel was originally due to start in 2012 and Crossrail to finish tunnelling around 2015. Thames Water had also cited planning applications delays with Newham Borough Council before going to the London Thames Gateway Development Corporation and the Olympic Authority for approval.

Site investigation work continues on the route of the main Tideway tunnel with a jack-up barge slowly moving down the River Thames to bore at various sites. The whole Tideway project is valued at some £2 billion (US$3.2bn) - the biggest single sewerage project since UK water utility privatisation - with the Thames Tunnel of the project designed to intercept at least 34 combined sewer overflows (CSOs). Programme manager for the project is US engineering practice CH2M Hill with AECOM as reference designer.