The water company Wessex Water is considering building a huge underground water storage tank in Swanage, Dorset, to prevent the treatment works being overwhelmed when it rains heavily.
It’s being proposed that the concrete storage tank will be constructed underneath Main Beach car park or under the adjoining overflow car park at King George’s playing fields at a cost of £5 million.
A water tank installation similar to this one at Bradford on Avon is proposed by Wessex Water
Concrete underground tank to hold four million litres
It will have the capacity to hold four million litres of waste water which gushes through the combined sewer system during periods of heavy rainfall, until it can be properly processed at the Swanage treatment works..
This is aimed at reducing the amount of storm sewage from the drains which ends up diverting to the overflow at Peveril Point and being discharged into Swanage Bay.
This is called storm sewage as it contains all the rainwater that flows down roads and into drains, as well as everything that goes into household drains including diluted sewage. If it didn’t go to an overflow, it could overwhelm the treatment works.
Currently, the Peveril Point overflow discharges about 20 times a year depending on annual rainfall but the government has set environmental targets for water companies which include not allowing overflows to happen more than 10 times a year.
As part of a five year funding agreement, Wessex Water has had to commit to reducing the use of the Peveril Point overflow by 2030 and this proposal is the solution.
The tank could be installed underground in the Main Beach overflow car park
Alternatively Main Beach car park may have to be used depending on ground water levels
Ground water testing
At this early stage, Wessex Water is undertaking viability studies to see whether the Main Beach car park or the overflow car park area will be suitable for constructing a concrete storage tank.
It has put probes in the ground to monitor the water levels, as the overflow car park field is in a floodplain zone.
At the Swanage Town Council coastal change and beach management advisory committee on Wednesday 22nd April 2026, Wessex Water representative Aaron Barton said that subject to the water level results, it was proposed to start construction in winter 2028 and it would last for 12 months.
He also said that mitigations would have to be put in place to compensate for the loss of parking in Swanage during 2029, while work took place.
Wessex Water is currently assessing ground water levels to see if the area is suitable
The aim is to reduce the number of storm sewage discharges from Peveril Point overflow
Wessex Water drop in event at Swanage Library
Wessex Water is holding a drop in community engagement event at Swanage Library in the High Street between 10 am to 2 pm on Tuesday 5th May 2026. A second event is planned for Tuesday 6th October 2026.
This is an opportunity to discuss water bills, water and sewage services, and ways to save water and prevent sewage blockages. It’s understood there will also be more information about Wessex Water’s plans to reduce storm sewage discharges in Swanage Bay.
Elsewhere in Swanage, according to the Wessex Water storm overflow improvement map, work on the Durlston overflow will also be completed by 2030, while work on the Shore Road overflow near Ocean Bay is planned to take place between 2030 and 2035 although it discharges directly onto the beach, and some would argue is more urgent.
Other areas in Purbeck where Wessex Water is planning to complete work on storm overflows by 2030, includes Studland, Corfe Castle and Wareham.
The Shore Road outfall is where the Ulwell Stream meets the sea, but after periods of heavy rainfall is can also contain storm sewage – Wessex Water says it is planning work between 2030 and 2035 to reduce the frequency of the discharges
Poppy Maltby at her home when she had just installed her greywater recycling system
Water use and eco measures
Householders can also help reduce the problem of storm overflows by separating rainwater and foul water. One way is to divert rainwater from down pipes into water butts. This reduces the amount of rainwater which gushes into the combined sewer during high rainfall.
A Swanage Streams Partnership meeting is being held from 7.15 pm on Wednesday 6th May 2026 at The Swanage School focussing on water use at home, grey water capture, water friendly gardens, rain harvesting, and how to keep drains and streams cleaner.
Speakers include Tim Stevens from Wessex Water on water-saving tips, Langton Matravers resident Poppy Maltby who recycles greywater in her home and garden, and Ella Gardner from Amphibian and Reptile Conservation about creating nature and water-friendly outdoor spaces.
The meeting is free to attend and open to all.
Further information
- More about storm overflow investment by Wessex Water
- Book a free place to the Swanage Streams Partnership meeting
