Cost of Havant Thicket Reservoir soars to more than £800million - here's why
Increased funding would expand the Havant Thicket Reservoir to support water supplies for over half a million people
The cost of building Havant Thicket Reservoir will more than double to over £800million because of the controversial water recycling project and ground works issues, it has been revealed.
Ofwat is set to approve plans to increase the funding for the project by around an extra £500m. A large portion of the increase - £125.9m - is as a result of the plans to add recycled waste water to it via a new treatment centre which would be created at Budds Farm in Havant and which would require an additional pipeline.
Challenging conditions of the ground has also led to the need for a major redesign of the project, with an extra £186.7m needed for a new embankment design. This is because it was not safe to proceed with the original design as a result of unforeseen shear surfaces and sand formations.
Ofwat has published a draft decision outlining increased funding to around £823m, compared with the original allowance of £339m. A public consultation on this has now been launched, with the site proposed to be in use in 2034 - five years later than originally planned.
Portsmouth Water is building the facility primarily for Southern Water’s Hampshire customers.
Ofwat has said that the expanded plans would ‘unlock a more than fivefold increase in the scheme’s potential water supply capacity’ compared to early designs for the scheme allowing up to around 111 megalitres of water to be supplied each day instead of the originally proposed 21 megalitres.
Senior director of major projects at Ofwat, Chris Taylor Dawson, said: "The Enhanced Havant Thicket Reservoir Project will provide greater resilience – supporting the supply needs of more than half a million people, whilst aiding recovery of Hampshire's internationally important chalk streams.
"We have rigorously scrutinised Portsmouth Water's submission and challenged costs where appropriate. Following that assessment, we are satisfied that while customers are paying more, they are receiving far greater benefits."
As previously reported by The News, the original project centred around creating a water reservoir which could be used in times of drought and was to be supplied by Bedhampton Springs.
But now the new, much larger project has been put forward to ensure there is a constant supply of water, with drier and hotter weather becoming more frequent in what Ofwat described as ‘a fundamental shift in the role of Havant Thicket Reservoir’ (HTR).
In its draft decision it said: “The main changes include a dual pipeline solution between the Enhanced HTR and Bedhampton – initially, this was a single bi-directional pipeline, a larger reservoir inlet pipe, modifications to Bedhampton pumping station, changes to the mixing and control systems, additional security requirements, and a revised treatment solution at Farlington Water Treatment Works.
“They are additional works required to integrate the Enhanced HTR with Southern Water’s Hampshire Water Transfer and Water Recycling scheme and to enable a different operating model from the one originally funded.”
Ofwat also outlined that unforeseen challenging ground conditions were discovered during early construction, which has added £186.7m to the bill.
“Specifically, engineers identified previously unknown shear planes and sand formations at the site, requiring significant redesign of parts of the reservoir and changes to the construction approach,” Ofwat’s report explained.
Portsmouth Water had requested £848.6m for the larger project, but Ofwat has told the water company to find savings of around £25.8m. The project is being funded by Southern Water, with its customers seeing their bills increase by £7.29 per year in 2027-28, £12.22 in 2028-29 and £13.51 per year in 2029-30.
Ofwat has also set out proposed arrangements over how additional costs and savings can be split between Portsmouth Water and Southern Water can be shared. It also outlines that additional costs associated with the creation of a Farlington to Nelson Pipeline to improve distribution needs to be considered separately.
It also sets out some protections for Portsmouth Water, including if the controversial Hampshire Water Transfer and Water Recycling project is not granted planning permission or is delayed by a lengthy planning process.
A Portsmouth Water spokesperson said: “We are continuing to make good progress on the construction of Havant Thicket Reservoir. However, since work began, it has been necessary to make two important changes to the project. This includes updating the design of the reservoir embankment and installing an additional pipeline.
“These changes will help make sure the reservoir remains safe and reliable for decades to come, as well as ensuring it can continue to supply water to customers if maintenance is needed. They also have the potential to reduce disruption for local people and the environment, as well as increase the amount of water it could supply in future if Southern Water's water recycling proposal, known as the Hampshire Water Transfer and Water Recycling Project, is approved in future.
“The changes mean additional investment is needed, and an updated budget was submitted to Ofwat earlier this year. Ofwat has now published its draft decision, which is subject to consultation, before a final determination is made later this year.”
Havant Thicket is first new reservoir to be built in England in more than 30 years. Construction on the reservoir is already underway, with work to start tunnelling due to begin later this month.
Meanwhile the Planning Inspectorate is still considering the plans for the Hampshire Water Transfer and Water Recycling project.
Ben Ring, managing director for capital projects at Southern Water, said: "Ofwat has proposed increased funding based on revised scope to enable the completion of the Havant Thicket Reservoir, including future-proofing for our planned Hampshire Water Transfer and Water Recycling Project. Together, these two projects are key components of our plan to protect water supplies and local rivers.
"We're progressing our Hampshire Water Transfer and Water Recycling Project as fast as we can. If approved, this will allow the reservoir to provide five times more water and deliver even greater value for customers."
Meanwhile Havant’s MP Alan Mak has reaffirmed his opposition to the waste water recycling element of the reservoir plans.
He said: “I support the Havant Thicket Reservoir project in general but I remain opposed to Southern Water’s wastewater recycling plan which does not command public confidence and should be scrapped.”
Ofwat’s draft decision is now open for consultation until October 12 and it welcomes views from stakeholders before a final decision is made.
The draft decision can be found here, including information on how to respond to the consultation.
To learn more about how water recycling works, watch the video embedded in this story
How the Havant Thicket Reservoir plans have changed
- Using a process known as reverse osmosis, purified recycled waste water would be added to the reservoir instead of it being filled solely by Bedhampton Springs and rainfall, increasing its capacity fivefold
- Two pipelines are being installed rather than one. These pipelines will be used to fill the reservoir with water and draw it out when needed and ensure an uninterrupted supply during maintenance periods
- The reservoir would be used all-year round instead of just in times of drought
- The embankment has been redesigned as a result of ground conditions uncovered after construction began including flatter embankment slopes and a larger footprint
- Portsmouth Water and Southern Water are yet to come to an agreement about the control of the reservoir
- The forecast operational date has been pushed back from 2029 to 2034