The Havant Thicket Reservoir will be the UK’s first storage reservoir built since the 1990s and is designed to safeguard water resources for south east England.
The Havant Thicket Reservoir in Havant, Hampshire, will be the UK’s first new storage reservoir built since the 1990s, and is designed to safeguard water resources for south east England. The reservoir will span a 160 hectare site between Leigh Park, Havant and Rowlands Castle, and will hold 8.7 billion litres of water.
The project is a joint venture between Portsmouth Water and Southern Water, and as well as providing a vital water supply, it will protect some of the country’s rarest river habitats as well as provide a sustainable recreational space for the local community.
New Civil Engineer reports that the Havant Thicket Reservoir designers will be mindful of the recommendations made in the Coxon report, which was published in 1986 following the failure of the Carsington Dam during construction in 1984.
The engineering team (Future Water MJJV) are carrying out extensive on-site trialling to investigate how the clay materials respond in various conditions. Extensive compaction trials have already been conducted to inform the construction of the main embankment.
Project director Terry Fuller explained: “This is a safety critical piece of infrastructure. The structural components of the project will be subject to extreme conditions. It probably goes without saying that if it fails, it would be catastrophic.”
The embankment will also include a concrete structure consisting of a manhole made up of a metre diameter concrete rings built on top of the dam. The culvert will also be formed with a concrete structure that will be built in 12 metre long sections to make a 240 metre long and 6 foot tall structure with a curved roof.
A trial three metre section of concrete was cast on site, Fuller explains: “In autumn last year we built a trial so we could put instrumentation in it, looking at concrete curing temperatures and the practicalities of building a rounded top using shuttering.” During the trial process, it became apparent that the design process would need to be modified.
Future Water construction manager James Hanson explained: “So while those areas are in abeyance, we’ve had to put them on hold. It means there are a few sections along the length of the culvert that can’t be completed and lends itself better to a ‘hit and miss’ sequence so we can push ahead without affecting the critical path.”
The trial culvert section, which forms an arch shape and is set on a plinth, will go on display in the Visitors Centre Carpark once the project is complete and open to the public. The first concrete pours for the culvert commenced in January and the earthworks are currently underway. The whole project has a scheduled completion date of 2029.
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