Construction has begun on the UK’s first man-made lake in more than three decades. The £340million Havant Thicket Reservoir in Hampshire is what’s being hailed as a milestone for the country’s future water security. The reservoir, set to hold a staggering 8.7 billion litres of water, spans 160 hectares and is being built by Portsmouth Water in partnership with engineering joint venture Future Water.
Once operational, it will help supply drinking water to the south of England while protecting environmentally sensitive chalk streams like the River Itchen and River Test. “This is a safety-critical piece of infrastructure,” said Future Water project director Terry Fuller.
“The structural components will be subject to extreme conditions. It probably goes without saying that if it fails, it would be catastrophic.”
The reservoir’s main embankment will stretch 2.8km and stand up to 22m high, built using layered clay and compacted to precise specifications.
To make sure everything works as intended, engineers conducted extensive trialling over the last year, including building a full-scale trial embankment and a mock-up of a 3m section of the reservoir’s 240m culvert.
“One of the key things we found was that the contact between layers of clay wasn’t always 100%,” said Coffey Geotechnics’ Derek Smith.
“That led to additional compaction trials to ensure everything ‘knits’ together.”
The culvert, a concrete tunnel allowing water to flow in and out of the reservoir, was also tested to iron out technical challenges like waterproof seals and structural joins.
Vibrating shuttering systems and “letterbox” access slots were trialled to reduce honeycombing in the concrete, caused by trapped air bubbles.
“This is a first-in-a-generation project,” said Portsmouth Water’s Ruari Maybank. “It’s critical that we get it right, not just for safety, but for future-proofing our water supply.”
Major earthworks are set to ramp up this spring, with the trial culvert section being turned into an educational exhibit once the project is complete.
