SCS JV completes HS2 ancillary shaft base slab

The first permanent works began at the site in February 2021 when the team poured a 160m3 concrete collar around the ancillary shaft. They then built the first 11m of the 25m internal diameter shaft using precast concrete segments, produced by FP McCann Ltd, before completing the final 19m depth using sprayed concrete lining.

The team of around 30 engineers and operatives have since completed the shaft with a 3.3m-thick base slab constructed in three different pours. The main pour of around 1,000m3 of concrete took place at the end of 2021; the second and third were completed by the end of January 2022, adding another 740m3 of concrete.

The site will provide critical infrastructure for the operation of HS2. As well as the 25m internal diameter shaft, which will provide ventilation and emergency access to the Northolt Tunnels, SCS JV is building a crossover box on the site that will let trains switch tracks on the way in and out of Old Oak Common station.

“We’re constructing eight ventilation shafts along our 13 miles (21km) of twin-bore tunnels in London and this vent shaft is the first to advance to this stage. Work is progressing well at all our other shaft sites so that they are ready for the TBMs to travel through them as our huge tunnelling programme progresses over the next three years,” said SCS JV managing director James Richardson.

The site at Victoria Road also has a crucial role to play in construction. SCS JV will use it to assemble and launch two TBMs that will dig the 3.4-mile (5.47km) eastern section of the Northolt tunnels. The TBMs are due to arrive in early 2023 and will begin the 12-month programme of tunnelling later that year.

The site will also be connected to the Logistics Hub located at the Willesden Euroterminal by a conveyor system that will remove spoil excavated for the tunnels. The conveyor system, which also connects the Logistics Hub to Old Oak Common station site, will become operational later this year and will contribute to reducing lorry movements for HS2, removing around 1million lorries from the road.