Thames Water has launched the search for a main works contractor to deliver the £5.7 billion White Horse Reservoir in Oxfordshire — a nationally significant scheme set to transform water resilience across the South East.

Planned for land south‑west of Abingdon, the 150‑billion‑litre raw water reservoir will be one of the largest of its kind in the UK. Designed as a fully bunded, non‑impounding storage reservoir covering around 6.7 km², the project aims to secure long‑term drought resilience for approximately 15 million people.

The reservoir will also host extensive floating solar installations to reduce operational carbon impact.

Two‑Stage Procurement for a Generation‑Defining Programme

Thames Water is running a two‑stage procurement with early contractor involvement, reflecting the scale, complexity and long delivery horizon of the scheme.

A key component of the project is approximately 4 km of new tunnels, which will transfer water from the River Thames to the reservoir via a new pumping station. These tunnelling works form part of a wider package of major civil engineering activities.

Broad Scope Covering Early Works, Civils and Tunnelling

The call‑off contract includes:

Early enabling works

• Site clearance and mobilisation
• Utility diversions
• Environmental and archaeological surveys
• Habitat creation and species relocation
• Major civil engineering and tunnelling

Large‑scale earthworks and embankment construction

• Borrow pits and replacement flood storage
• Tunnelling and pipeline installation
• New access roads and overbridges
• Intake and outfall structures on the River Thames, supported by a sheet‑piled temporary cofferdam

Transport, logistics and supporting infrastructure

• Temporary rail siding and materials‑handling area on the Great Western Main Line to reduce HGV movements
• Floodplain works and watercourse diversions
• Early works linked to the future restoration of the Wilts & Berks Canal

Structures, M&E and long‑term landscape management

• Concrete structures and buildings
• Mechanical and electrical systems
• Landscaping, habitat management and long‑term environmental stewardship

Long Delivery Window and Economic Impact

The successful contractor is expected to be appointed in August 2027, with involvement running through to March 2043. Construction is anticipated to create around 1,800 jobs, supporting regional economic growth over the long term.

Industry Leaders Highlight National Importance

Thames Water Chief Executive Chris Weston described the reservoir as “one of the most significant investments in water infrastructure the country has seen in decades,” noting its role in supporting millions of customers, enabling new housing growth and creating a new public destination for recreation and nature.

Mohit Farmah, Head of Procurement and Supply Chain, said the utility is seeking a contractor with the capability and vision to deliver “one of the UK’s most significant infrastructure projects” while ensuring long‑term value for customers.