Future Water Celebrates Major Milestone at Havant Thicket Reservoir

Future Water MJJV is proud to announce the successful completion of a major piece of work at Portsmouth Water’s Havant Thicket Reservoir, an operation that marks a UK first and demonstrates the incredible teamwork between Future Water and Portsmouth Water.

On 14 January 2026, the project team finished the first stage of the Culvert Cut‑Off Wall, a vital part of making sure the future reservoir holds water safely and securely.

What Is the Culvert Cut‑Off Wall?

To help explain this engineering challenge, imagine the reservoir embankment as a giant bathtub, and the large concrete culvert underneath it as the plug hole that will be used to empty the reservoir when water is needed. For everything to work properly, the join between these two structures must be perfectly sealed, just like the silicone seal you’d use around a bathtub at home.

Creating this seal deep underground, beneath a future reservoir, required an innovative and highly precise solution. Coffey Geotechnics Ltd led the design for a special “Cut‑Off Wall”, which acts as an underground barrier to contain the water.

A UK First Engineering Achievement

To build this barrier, Future Water constructed a 20‑tonne steel sheet pile wall on site. Standing at 9 metres high and 13 metres wide, the wall was lifted into place in one piece using a powerful 100‑tonne crane.

Before the lift, a trench was dug 8 metres deep and filled with a bentonite slurry mix. The steel wall then had to be lowered into this mixture within a tolerance of just 25 millimetres. Achieving this level of accuracy with a structure of that size is a major achievement in itself.

This solution is the first of its kind ever used in the UK, designed to meet the unique ground conditions found at Havant Thicket.

72 Hours of Non Stop Teamwork

Because the slurry starts to harden as soon as it is mixed, the team had to work continuously for over 72 hours. Teams from Future Water rotated through day and night shifts to keep the work moving safely and smoothly.

Their commitment ensured the steel wall could be installed before the slurry cured, a race against time that required planning, teamwork, and exceptional focus.

The slurry will now be left to cure for 28 days. Later this year, the steel wall will be connected to the concrete culvert, and the embankment will be built over the top. This will complete the Culvert Cut‑Off ahead of the main embankment construction in 2026 and 2028.

An environmentally-led project

The completion of the Culvert Cut‑Off Wall is a major step forward for Portsmouth Water’s Havant Thicket Reservoir, an environmentally-led project that will play a key role in protecting two internationally renowned chalk streams in Hampshire, the River Test and River Itchen.

This achievement reflects innovation, collaboration, and the shared commitment of everyone involved. Future Water and Portsmouth Water are proud to celebrate this moment as work continues toward delivering the first new reservoir in the region in decades.

“The successful completion of the Culvert Cut-Off marks a critical technical milestone for the Reservoir project. Delivery of this element relied on close collaboration with Keller and Coffey Geotechnical, whose expertise were instrumental in achieving seamless execution. This UK-first solution was specifically developed to suit the site’s ground conditions and provides a robust hydraulic barrier between the culvert and underlain strata, and long-term reservoir performance and enabling the next phase of construction. While the works themselves were completed on site within a matter of days and without hindrance, this efficiency was the direct result of many more hours invested in design development, planning, and preparation, it was a true team effort.”  – Ryan George, Project Manager, Future Water

Visitors to our Havant Thicket Reservoir site were treated to an extraordinary sight recently, a white stag, now affectionately named Casper, roaming near the works. While deer are not uncommon here (we’ve previously seen a stag, does, and even a young fawn), this is the first time we’ve encountered a white deer.

Why is this so special?

White deer are extremely rare in the UK. Their distinctive appearance is usually caused by leucism, a genetic condition that results in reduced pigmentation, or occasionally by albinism. Unlike albino animals, leucistic deer typically have normal eye colour and are perfectly healthy.

Monitoring and Welfare

Our Environmental Team has been monitoring Casper from a distance as a precaution, but we have no concerns about his welfare or his ability to leave the site. He is being left undisturbed to roam freely.

Wildlife at Havant Thicket Reservoir

This sighting highlights the wildlife that continues to flourish around Portsmouth Water’s Havant Thicket Reservoir, as we deliver an environmentally led project that secures vital water supplies while creating new habitats and green spaces for the future.

Future Water was proud to attend the Earthworks 2025 Conference, hosted by the British Geotechnical Society, bringing together leading minds in geotechnical engineering, sustainable construction, and earthworks innovation.

The event kicked off with a welcome reception at the Lapworth Museum of Geology, home to over 4.6 billion years of geological history. Our team was treated to a rare behind-the-scenes tour, where they explored extraordinary specimens, including one of the most well-preserved trilobite fossils ever discovered in the UK. This immersive experience set the tone for a conference focused on the intersection of science, engineering, and environmental stewardship.

The two-day conference featured a series of thought-provoking keynote presentations and technical talks:

• Day One Highlights:
  • A keynote by Dr. John Perry, Independent Consulting Engineer, explored the evolution of earthworks design and construction.
  • Sessions covered topics such as resilient and sustainable earthworks, modern design practices, and risk management through monitoring.
• Day Two Highlights:
  • A keynote on Earth Dam Engineering: Past, Present, and Future.
  • Talks focused on case histories, earthworks trials, specification and treatment techniques, and advances in plant and construction technologies.

Between sessions, Future Water had the opportunity to exhibit our latest work, showcasing how we’re pushing boundaries in sustainable infrastructure and water management. Our stand attracted interest from a wide range of industry professionals, allowing us to connect with like-minded organisations, share project stories, and explore potential collaborations.

This event was not only a chance to learn and reflect—it was a valuable platform for networking and knowledge exchange, reinforcing Future Water’s commitment to innovation and partnership in the geotechnical space.