New outfall at Swalecliffe
We’re replacing a sea outfall pipe at Swalecliffe as part of a major upgrade to our Wastewater Treatment Works.
What did the works involve?
The engineering project follows sea damage to the existing outfall and will involve installing a much longer pipe in its place.
This will mean any storm water releases from this outfall – which only happen rarely, as a last resort to prevent nearby homes and business flooding – are further out to sea and further from local beaches and bathing waters.
Our work on the beach is scheduled to last for 22 weeks and the project is due to be completed by the end of 2024.
John Penicud, Director of Wastewater Operations at Southern Water, said, “We would like to thank you for your support and patience while we carry out this essential work.”
This project is part of our Clean Rivers and Seas Plan to drastically reduce our use of storm overflows along our coastline.
Updates
As the engineering project came to a close, the team recreated a 100-year old photo taken by one of their grandfathers, showing the original outfall being installed.
The final stage of the project is to reinstate planting along the site boundary, including more than 20 different varieties of trees and shrubs.
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The new pipeline was successfully floated into position on the 18 June 2024 after being towed from the River Medway. Upon arrival at Swalecliffe, it was sunk into the trench by carefully flooding the pipe with seawater and then backfilling the trench. The specialist dredger – the Razende Bol – and excavators continued this work during July.
A second barge, the Neptune, assisted by the tug Barney, constructed the diffuser structure at the end of the pipeline. A ‘duck bill’ valve allows flows out of the pipeline but stops any flow back into the pipe. A 150-tonne precast concrete diffuser protects the valve.
The new outfall entered operation by early August, and is monitored from our Control Centre. Results are displayed via our online spill notification service.
The last phase of this project involved removing the section of the old outfall that is supported on wooden trestles using excavators working from the beach. The remainder of the pipeline has been left in place to avoid disturbing the profile of the beach.
The esplanade was diverted in the middle of May, and piling works started to create a working area adjacent to the sea wall, providing sea defence during the works. Excavators started working on the beach to dig the trench for the new outfall pipeline and a specialist dredger – the Razende Bol – arrived from the Netherlands.
Tugs were also brought in to help the dredger manoeuvre, and a survey vessel checked the excavation of the new trench. The work took place when the tide was out which meant some early starts and late finishes. The area of the beach was cordoned off and marshals were on hand to keep everyone safe.
Owners were asked to keep dogs on a lead near our working area. The new pipeline was due to be floated into position at the end of June, but all our activities are very dependent upon the weather.
On Monday 11 March 2024 we set up our temporary storage area adjacent to the esplanade. This compound was accessed from inside Swalecliffe Wastewater Treatment Works to avoid vehicles travelling along the esplanade, which remained open throughout the construction period. Construction of the pipeline began after Easter, starting inside our treatment works and working towards the beach.
Once the pipeline reached the esplanade, installation stopped while a short diversion of the esplanade was constructed. This diversion was in place from late April to September 2024. It allowed a section of the sea wall to be removed to install the pipeline, which is three metres wide and constructed of concrete, with a similar finish to the existing esplanade.
Residents may have heard us undertake periods of piling, so that we could create a working area at the sea wall and provide temporary sea defence during the works. Piling was scheduled from 17 April 2024 for a period of 24 days and also from 14 June for 15 days. During these periods, the piling was intermittent and lasted for approximately 30% of the working day.