In addition to construction of the main tunnel for the Thames Tideway project in London, two main connection tunnels will be excavated at Greenwich and Frogmore and as part of the West and the East contracts.

On the East contract, contractor JV Costain-Vinci-Bachy will use a Herrenknecht slurry TBM to excavate the 4.5km long connection tunnel that will convey flow from Greenwich to a connection with the main trunk sewer tunnel at Chambers Wharf in Bermondsey. The 6.4m diameter TBM will pass through 4,500m of chalk to excavate the 5.6m i.d. tunnel.

On the West contract, the Balfour Beatty-Morgan Sindall-BAM Nuttall JV will deploy a refurbished Lovat EPBM to excavate the 1.1km long x 2.6m i.d. Frogmore connection tunnel. According to information supplied by Tideway, the EPBM has a greased lubricated triple roller bearing and Lovat grease lubricated sealing system designed to operate in ground/water pressures up to 4 bar.

Back on the East contract at Bermondsey, the Costain-Vinci-Bachy JV has started excavating an operating and working shaft at Chambers Wharf using an electrically powered hydrofraise diaphragm walling machine. The machine runs from mains electricity instead of diesel.

“As well as being more environmentally friendly, the machine is also quieter in operation," said Martin Stanley, Tideway Geotechnical Construction Manager. "This type of hydrofraise machine is thought to be one of the first of its kind in the world. We are to be using it on the project and will continue to look at ways of reducing our carbon footprint and minimising any disruption to our neighbours as the project moves forward.”

The machine, developed by the CVB Costain-Vinci-Bachy JV, started work at the beginning of August.

NFM and Herrenknecht are to supply two TBMs each to the Tideway supersewer tunnel project under the River Thames in London. Following the course of the River, the TBMs will excavate the 25km long tunnel from Acton in the west to Kirtling Street in the centre and on to the Abbey Mills pumping station in the east (Fig 1).

Herrenknecht EPBM for the West contract

Work is underway on the banks of the Thames as Tideway workers excavate a 30m diameter access shaft at Kirtling Street from which the two NFM machines for the Central contract will progress. FLO, the construction JV of Ferrovial-Laing O’Rourke, procured the two 8.84m diameter NFM EPBMs to complete the 12.7km of the Central contract excavating about 5km to the west and 7.7km to the east. NFM Technologies is currently assembling the two EPBMs in its facilities in Le Creusot, France, where they are being prepared for their factory acceptance tests.

Herrenknecht is to supply an 8m diameter EPBM to the BMB Balfour Beatty-Morgan Sindall-BAM Nuttall JV to excavate the 6,950m drive for the West Contract from Acton to Carnwath Road.

The second Herrenknecht machine is an 8.8m diameter slurry TBM for the CVB Costain-Vinci-Bachy JV for the 5,530m East Contract drive from the Chambers Wharf site to the Abbey Mills pumping station.

Fig 1. Elevation of the gravity-fed sewer, the geological profile and boundaries of the three construction contracts

The segments for the tunnel lining of each contract are also moving into production. Segments for the 6.5m i.d. West tunnel are being produced at the Morgan Sindall precast factory at Ridham Dock in Kent. Dramix 4D8060BG steel fibre from Bekaert Maccaferri are in the concrete mix for the fibre reinforced segmental lining.

For Tideway Central, FLO has engaged Pacadar of Madrid, Spain, to cast the 7.2m i.d. lining. The casting yard facility at Thamesport Kent on the Isle of Grain is equipped with 45 moulds supplied by cbe of France to cast the seven segments plus a key in each 350mm thick x 1.8m x 8.5m o.d. x 7.8m i.d. ring of lining.

Segments for the 7.2m i.d. lining rings for the East Contract drive are being manufactured by Tarmac and Max Bögl at a precast factory at Tallington near Stamford in Lincolnshire. Mould suppliers for the East and West tunnel contracts are yet to be confirmed.

The tunnel is scheduled to take seven years to build and will run mostly under the tidal section of the Thames. Along the route the tunnel will intercept 34 combined sewer overflows, connect existing sewer lines to the new Tideway tunel via transfer adits, and will convey all flow to the Beckton Sewage Treatment Works passing through the recently completed 6.4km long x 7m i.d. Lee Tunnel between Abbey Mills and the Beckton treatment plant (Fig 2).

The new supersewer infrastructure is being financed and built by Bazalgette Tunnel Limited (BTL), a consortium of investors comprising Allianz, Amber Infrastructure, Dalmore Capital and DIF, which will also maintain and operate the facility once completed. BTL started the project on 3 November 2015 and is expected to bring the facility into operation in 2023.