NEWS |


Final TBM launch for HS2 Northolt Tunnel


TBM finish on Virginia project US – Tunnelling for RiverRenew, a wastewater project in Alexandria, Virginia, has been completed. TBM ‘Hazel’, which was launched in


November 2022, recently broke through after boring a 3.2km-long tunnel under Old Town Alexandria and the Potomac River. The 4.47m-diameter Herrenknecht TBM


broke through in a 30.5m-deep shaft, which in future will collect combined sewage overflows from an existing outfall and direct the flows through the new tunnel to Alexandria’s wastewater treatment provider, AlexRenew. The wastewater will be treated and returned to the Potomac River. Completing excavation of the new


Waterfront Tunnel marks the integration of AlexRenew’s wastewater plant with all four of the city’s combined sewer outfalls (CSOs) that date back to the 1860s. The remaining works include the


Above: Final TBM launched for HS2 Northolt Tunnel PHOTO CREDIT: HS2


UK – The fourth, and final, TBM for HS2’s Northolt Tunnel beneath London, has been launched. TBM ‘Anne’ will bore 5.5km


from Victoria Road in Ealing, near HS2’s Old Oak Common station, to Greenpark Way in Greenford, alongside TBM ‘Emily’ which launched in February. The 13.5km- long Northolt Tunnel will run from Victoria Road in Ealing to West Ruislip in Hillingdon. The other 8km of twin-bored


tunnels has been under construction since 2022, with TBMs ‘Sushila’ and ‘Caroline’ both over halfway through their journey between West Ruislip, on the outskirts of London, and Greenpark Way. The four TBMs on Northolt Tunnel


are to complete their journeys in 2025.


TBM ‘Anne’ – an EPBM


manufactured by Herrenknecht – weighs 1,700 tonnes, is 170m long and has a 9.11m diameter cutterhead. It was lowered in parts into the 25m-deep crossover box at the end of 2023. It will install concrete rings with


an external diameter of 8.78m, an internal diameter of 8.10m, each made up of seven segments. Each segment weighs approximately 7 tonnes and are being manufactured in Hartlepool by Strabag from


6 | May 2024


where they are transported to London by train. HS2’s London tunnels contractor,


Skanska Costain Strabag (SCS) joint venture, has delivered an extensive programme of work for the TBM to launch at the Victoria Road Crossover Box, excavating the caterpillar-shaped box where eventually the trains will cross tracks on their way in and out of Old Oak Common station. TBM Anne is the eighth TBM to


be launched to date across the HS2 project. In all, almost half of the 105km worth of twin-bored tunnels has now been excavated. The London Clay excavated by TBM


‘Anne’ will be taken away from the Victoria Road Crossover Box site via a conveyor, removing the need for local lorry movements. From there, it is transported to HS2’s London Logistics Hub at the Willesden Euroterminal site where it is sorted, before being taken by train for reuse across the UK. In total, 10 machines are building


the HS2 tunnels. Two remaining TBMs, which will eventually be used to dig the final tunnel between Old Oak Common and Euston, in central London, once the government gives approval, are still being built. They are set to be delivered to the UK later this year.


completion of a smaller sewer line along Hooffs Run, fitting out the drop shafts, and constructing a 12-storey underground pumping station at AlexRenew. Work is expected to continue throughout 2025.


Start on Pape Tunnel CANADA – Infrastructure Ontario and Metrolinx recently selected the Pape North Connect team to deliver the Ontario Line Pape Tunnel and Underground Stations contract in Toronto. The Pape North Connect consortium


signed a Development and Master Construction Agreement (DMCA) with Metrolinx, under a progressive design- build contract. The team includes: the construction team of Webuild Civil Work and Fomento de Construcciones y Contratas Canada Ltd; and, the design team of Arcadis Professional Services (Canada) Inc and Aecom Canada Ltd. The DMCA contract incorporates a multi-


stage design process called a development phase, according to the progressive design- build model. The development phase allows for a


collaborative approach between Metrolinx and the consortium to finalise the scope, risk allocation and pricing of various elements of the contract. This phase is expected to take 24 months, though early works can commence start. Follow the development phase, Metrolinx


has the option to sign a final target-price agreement, which would include final agreements on detailed designs and a negotiated price.


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