What are we doing and why is it needed?
We’re helping to protect the town’s popular beaches by increasing capacity and reducing the automatic operation of storm overflows.
We’re constructing an extra nine million litres of additional storage at the Holdenhurst site next to the A338 by building a new 65-metre-long storm tank.
We’ll also boost our ability to remove harmful chemicals, including some that are frequently found in many household products, from wastewater to ensure we protect our rivers and coastlines.
To achieve this, we are constructing two new chemical dosing units that will be in place at the site, including one treatment lane with 50 membranes to help with ammonia removal which will be the largest single-unit installation of this type in the country.
Currently, Holdenhurst serves a population of approximately 180,000 which increases significantly during the summer months. By adding this new equipment on site, we’ll be able to ensure that the treatment of sewage keeps pace with a local population that is projected to grow further.
What about the impact on the local environment?
The extra storage will help to reduce the automatic operation of storm overflows nearby by nearly a third.
Boosted processes for removing chemicals from sewer flows arriving at the water recycling centre can also reduce the impact of nutrients, such as phosphorus, ammonia and nitrogen that can cause excessive growths of algae and damage the ecology of our waterways.
The story so far
Construction of both the chemical removal and storage elements of the enhancement have been continuing throughout 2024.
More than 40 team members are working full time at the site and, since the start of the year, more than 40,000 tonnes of earth have been excavated to house the massive new storage tank next to the A338.
When built, the 6.5-metre deep tank will be able to retain nine million litres of water during storms, reducing automatic discharges to the environment from storm overflows and allowing the storm water to be treated – that’s the equivalent of nearly four Olympic swimming pools.
More than 150 concrete piles - equivalent to 3.5 kilometres – have been constructed as foundations for the new tank and a further three kilometres of steel piles have been driven to allow excavation for the tank.
We’re investing £1 million to reduce groundwater levels to eight metres below the surface to help the tank construction.
In this process, groundwater is being pumped away from the excavation area at up to 100 litres a second – or eight million litres a day.
During the course of the scheme, this will amount to more than 1.5 billion litres of groundwater which is being removed and returned to the environment.
We’re also building two chemical dosing units capable of holding 125,000 and 90,000 litres of water treatment chemicals respectively.
Supplied by Wessex Water’s own Off Site Build team, these will be ready for operation by the end of the year and boost our ability to remove harmful chemicals, including some that are frequently found in many household products, from wastewater to ensure we protect our rivers and coastlines.
A further treatment process, featuring 50 MABR membrane units to help control suspended solids and debris and improve treatment of the wastewater will also be completed by the end of the year – and will be the largest single-unit installation of its type in the country.
The additional storm storage will be ready by March 2025.
Holdenhurst does not have facilities for the treatment of the sludge that arises from the water treatment process.
All surplus sludge is transferred to the nearby Berry Hill Bioresources Centre, where 750 cubic metres of additional sludge storage is currently being built – and existing storage tanks and transfer pumps repurposed – by November 2024.
What else are we doing?
We are committed to reducing overflow discharges and minimising the environmental impact of our sewage treatment processes, with £1.4 billion being spent between 2020 and 2025 on water and sewerage improvements.
We’ve recently re-lined a mile of sewer pipework in Dorset alone to further protect the environment, preventing rainwater from infiltrating the network and sewer flows escaping from them.
Schemes to build a new pipeline along the Jurassic Coast at West Bexington and separate rainwater from sewers around the iconic Portland Bill lighthouse were completed in 2023.
Meanwhile in Lytchett Matravers, near Poole, work is expected to start on a wetland next to a sewage pumping station in 2024. The first of its kind in Dorset, which will provide natural wastewater treatment before it is safely returned to the Poole Harbour catchment.
Real-time monitoring in Bournemouth and Boscombe
As coastal and river water quality is affected by numerous sources, including wildlife and agriculture, we have developed an Artificial Intelligence (AI) app.
Real-time monitoring in Bournemouth and Boscombe will provide a better understanding of the current water quality status, allowing people to make more informed decisions when using bathing waters for recreational use.
We were the first UK company to publish data on storm overflow operations at bathing waters and other recreational areas 365 days a year and provide this information to councils and Surfers Against Sewage.
How can you stay up to date with progress?
We’ll be providing updates throughout the course of the Holdenhurst scheme.
Revisit this page to stay up to date with how the scheme is progressing.