In June 2011, Associated British Ports (ABP) awarded Mackley Construction the contract to replace the existing breakwater at the Port of Southampton. This is part of a move to embrace advancements in breakwater design and improve conditions within the recently modernised marina.
At a total length of 129 m, width of 5m and depth of 2.8m, the new floating concrete breakwater when fully completed in 2012, will be one of the largest in the UK. Intermarine, as part of the Mackley Group, have been tasked with designing the mooring system, assisting with the UK production and installation of the units, and overall project management.
Traditionally, large breakwater pontoons are manufactured in mainland Europe and transported to the UK by ship. With this project however, Intermarine have broken the mould by having the seven, 18.4 metre floating concrete units fabricated in the Port of Southampton itself, saving an estimated £100K in freight costs alone. By manufacturing on site, British materials and suppliers are being utilised, alongside design expertise from Ørsta Marina Systems Norway, an established European breakwater manufacturer, and onsite production by Ørsta Marina Systems Netherlands.
Over the past 10 years, Ørsta have studied breakwaters in their quest to produce a long-lasting floating concrete system. Numerous wave tank experiments, and intensive computer modeling for optimum wave attenuation, have resulted in a modular system that’s economical, robust and energy efficient.
Cast using a high spec self-compacting concrete mix designed by Ørsta Norway and Sika, and supplied by Hanson, the breakwater units weigh a mighty 65 tonnes each. The units are linked together with a continuous post-tensioned cable system that forgoes the traditional bolted method. This means the loads applied to the concrete units at the pontoon connection points are predominantly compressive rather that tensile, which better suits the properties of concrete.
Additional design enhancements include steel liners installed at the anchor connection points, keel ends splayed to avoid contact with the anchoring system, and an increased cover of concrete to a depth of 50mm.
According to Scott Gaherty, Managing Director of Intermarine: ‘We believe this project has only been made possible by the spirit of cooperation between Intermarine and Ørsta. The result will be an impressive structure at the top end of what is possible when it comes to floating breakwaters.’
Associated British Ports can rest assured the project is in safe hands. The Mackley Group, with long-standing expertise in large-scale civil engineering and construction projects, in partnership with Intermarine, an established designer & supplier of marina pontoons, have the capability to deliver the best of both worlds for the Port of Southampton.
Intermarine are keen to hear from parties interested in the old breakwater units. Also on offer is the opportunity to purchase new breakwater units before the mould returns to the Netherlands.
For further details contact Scott Gaherty at Intermarine on +44 (0) 23 8023 1332