Wavebreak pontoon launched in Plymouth
An innovative new wavebreak pontoon has been launched at the entrance to King Point Marina in Millbay.
The 58 tonne steel floating pontoon was installed by contractors Land and Water Services Ltd and is designed to reduce wave height in Millbay’s historic inner basin, to no more that 0.5 of a metre.
The pontoon, which is 26m long and 4m wide with a draft of 2.5m, is the result of extensive testing and investigative works by Land and Water Services on behalf of Sutton Harbour Holdings plc, which owns and operates King Point Marina, in order to find a more robust alternative to the wave gates previously in place at the site.
The wavebreak pontoon has been designed to span across the entrance lock to King Point Marina when major storm conditions are expected from a south easterly direction, providing safe wave heights and vital flood protection to the entire developing Millbay quarter. The wave pontoon is not deployed in all storms, only when there is a serious flood risk.
The design of the new wave mitigation system meets the criteria for a 1-in-200-year storm event and has the approval of the Environment Agency and other regulatory authorities.
Mark Brimacombe, Marina Manager, said: “We are delighted to see this new wavebreak pontoon launch at King Point Marina following a number of months of carefully managed construction works to install the system.
“We are confident the new pontoon will provide reliable and effective flood prevention for the marina and for the harbour at Millbay.”
King Point Marina opened in Millbay in 2013, offering contemporary berthing for up to 171 vessels in the centre of Plymouth’s newly revitalised Coastal Quarter, and forming the focal point of Millbay’s widespread regeneration being undertaken by lead developer English Cities Fund (ECf).
The wavebreak pontoon will only be used in the inner basin in exceptional circumstances and will remain moored at the marina when not in use. The pontoon is guaranteed to reduce wave heights in the marina but does not affect wind speed.
It is only expected to be needed on rare occasions and is not designed to be deployed in all storm conditions, as the entrances to Millbay Harbour and King Point Marina are already largely protected by Plymouth Breakwater and the natural stone walls.
James Maclean, CEO of Land and Water Services Ltd, said: “The pontoon has been modelled, developed, fabricated and installed following state-of-the-art model testing at Hydraulics Research Wallingford’s wave tank.
“Extensive consultation has taken place with the Environment Agency and Plymouth planners in proposing the solution in preference to traditional steel lock gates, in line with Land & Water’s drive to find creative solutions.
“Developers of the quayside have also approved this innovative solution.”
The steel fabrication was undertaken at Roltech’s works in the Midlands and transported as a single piece to Plymouth, where it was craned into place at the city’s Victoria Wharf. The pontoon was then towed to King Point Marina.
Other aspects of the project included the installation of restraint piles, which the pontoon locks onto when in use, as well as new piles within the marina to enable the pontoon to be stored when not in use.