Southern Water is delivering the Southampton Link Main, a major new underground drinking water pipeline project in Hampshire, UK, to reinforce regional water supply resilience.

• The scheme will install a new ~17–19 km pipeline connecting Otterbourne Water Supply Works with Yew Hill reservoir (near Winchester) and Rownhams Water Supply Works (Southampton).
• The project is part of Southern Water’s Water for Life – Hampshire strategy to manage drought risk and protect sensitive catchments such as the Rivers Test and Itchen.
• Construction began in 2025 and is expected to take around three years (completion circa 2028).
• The estimated project cost is over £100 million.

The pipeline will be largely constructed by open cut trenching and backfilling, with some sections constructed using tunnelling techniques to avoid disruption at key infrastructure and environmental sites.

Tunnel Boring Works

As part of the pipeline installation, tunnel boring machines (TBMs) are deployed in sections requiring deeper underground work:

• A manually operated TBM named “Ancasta” (6,500 kg) has been tunnelling below Hampshire, creating a 1.5 m diameter tunnel and forming part of the Southampon Link Main alignment.
• Two TBMs were named via a local school competition — Ancasta and Mary Anning — to reflect regional heritage and provide tradition-based good luck for tunnelling.
• Major tunnel milestones include completion of a tunnel section beneath the M3 motorway using a remotely operated TBM driven over 32 days without disrupting traffic — a key piece of underground infrastructure delivery on the programme.

These tunnelling activities show structural complexity beyond simple trench pipeline laying, suggesting opportunities for tunnelling contractors, but formal procurement details have not been published on the Find a Tender service for the main contractor role for this project.

Current Contract / Delivery Arrangement

At present, the principal delivery vehicle for the Southampton Link Main pipeline is through a joint venture between M Group Water and Galliford Try (trading as MGjv), under contract with Southern Water.
This work arrangement suggests that the primary construction contractor has already been appointed, at least for the current phase of the works.

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