Inside the Tunnel Boring Machine, Southampton Link Main project
A six-tonne tunnel boring machine is digging deep below the ground in Hampshire to help keep the county’s taps and rivers flowing.
A manually operated tunnel boring machine called “Ancasta” has helped with digging underground tunnels and is part of a project called the Southampton Link Main, a 19km drinking water pipeline across Hampshire.
“Ancasta” weighs 6,500kg, is 2.7 metres long and has created a 1.5-metre-wide tunnel. The pipe depth starts at 14 metres. The tunnel work started in September 2025 and will continue through to May 2026.
Tunnel boring machines are traditionally given a female name to provide good luck for the projects, a custom followed around the world.
“Ancasta” was selected from dozens of suggestions put forward by children across our region for the huge drills. Ancasta was worshipped in Roman Britain and was associated with the nearby River Itchen.
The whole Southampton Link Main project will take more than three years to complete and cost more than £100 million. Most of the pipeline will be laid by digging trenches, installing the pipeline and then backfilling them with earth.
However, in some areas, it will be installed by digging tunnels deeper underground to avoid disruption to major roads, railway lines or precious ecological sites.
The manually operated tunnel boring machine is one of two machines that are digging part of the hole, which is part of the project.
Ben Ring, Director, Major Projects at Southern Water, said, “The Southampton Link Main project has been underway since the middle of 2025 and there are many exciting aspects to major projects such as these.
“This is part of a wider set of projects designed to improve the resilience of our water network for our customers in Hampshire. The project will also provide future resilience for the Test and Itchen rivers and their wildlife.”
The new underground pipeline will run from Otterbourne to Yew Hill reservoir, near Winchester, and then south to our Rownhams water supply works on the outskirts of Southampton.
Southern Water are working in partnership with MGjv, a joint venture between Galliford Try and M Group Water, and supply chain partner HB Tunnelling.
