Yew Hill Reservoir and Southampton Link Main: design and resilience notes for engineers
Reviewed by Tom Sullivan
First reported on The Construction Index
30 Second Briefing
Southern Water has unveiled the soon-to-be-filled Yew Hill Reservoir, a twin-cell structure designed to store 9m litres of potable water, supported by more than 170 internal columns and built with over 3,500m³ of concrete and 650t of steel by MGjV (M Group and Galliford Try). The reservoir forms a key node in the £100m Southampton Link Main, which includes a new 19km transfer main and new pumping stations. Once commissioned, the scheme will hydraulically link Otterbourne WSW, Yew Hill and Rownhams WSW to improve regional supply resilience in southeast England.
Technical Brief
- Twin-cell configuration allows one cell to be isolated for inspection while maintaining partial storage capacity.
- Internal column grid implies relatively thin roof slab spans, reducing reinforcement tonnage and shrinkage cracking risk.
- New transfer main will require multiple pressure zones and surge control to manage transient events.
- Hydraulic linkage between water supply works enables bi-directional transfer under differing demand scenarios.
- Integration of new pumping stations will likely require staged commissioning to avoid pressure shocks in existing network.
- Structural design must accommodate full/empty differential loading between the two cells during phased operation.
- Similar twin-cell, column-supported reservoirs are increasingly used in UK schemes for resilience and maintainability.
Our Take
The 19 km Southampton Link Main connecting Yew Hill Reservoir with Otterbourne and Rownhams ties directly to the February 2026 tunnelling piece, where Southern Water and the MGjv team were already driving a 1.5 m diameter tunnel on this same corridor, signalling a long-running, staged delivery strategy rather than a single contract push.
The use of more than 650 t of steel and over 170 columns at Yew Hill Reservoir suggests a robust, long-life buried structure, which will be important for Southern Water given the constrained urban and utility interfaces highlighted in its River Anton enhancement works elsewhere in Hampshire.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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