Jetty removal at Portsmouth

Enak, a ‘sheerleg’ barge, is making its first visit to Portsmouth International Port. It can normally be found working on complex offshore salvage jobs. However, with a 600 ton lifting capacity the stable vessel is also perfectly suited to assisting in the demolition of the ‘Floating Dock Jetty’. The structure has now been cut up in to sections weighing up to 400 tons by contractors Herbosch-Kiere Marine Ltd.

Enak is a medium sized sheerleg, the name describing the type of fixed crane carried on its deck. The vessel is part of an impressive inventory of equipment and plant available to Herbosch-Kiere. The company has experience of lifting weights of up to 1,300 tons in UK waters.

Removal of the “Floating Dock Jetty”, a large concrete and steel structure built in 1906, will make it possible for much larger vessels to take advantage of facilities at Portsmouth. The demolition work is part of a £5 million investment in creating a more flexible future, removing a navigational hazard that has not been used in decades. The jetty was designed to secure large floating dry docks once used by the Royal Navy for the maintenance of Dreadnoughts.

There has been much preparation for the tightly scheduled operation, with barges, plant and equipment needing to be secured before work started in September. The deck of the jetty, which sits on deep-set cast iron piles that are 12 feet in diameter, has now been ‘sliced’ using specialist-cutting equipment. Each section will be lifted onto a processing barge, where the concrete and steel will be broken into smaller pieces.

The removal of the deck section is expected to take between two and three weeks. Recyclable materials will be crushed and sent on for recycling. Work will then begin to remove the supporting piles. Enak will play a crucial role in this phase of the demolition too. The barge will be fitted with a 90 ton grab, with a 350 ton shutting force, to lift and remove the deep set piles.

Guy Brown, Managing Director of Herbsoch-Kiere Marine Contractors, commented “We share the client’s pleasure in seeing this project advance to work on site, and look forward to successfully completing a challenging heavy lift marine demolition project.”

Martin Putman, Port Manager, Portsmouth International Port, said “It has been fascinating watching Enak start work, easily removing such large sections of the Floating Dock Jetty. After months of planning it is good for everyone at the Port to see progress being made. It is another step forward in the continued development of Portsmouth.”

It is planned that all the heavy lifting work will be completed by Christmas, allowing Enak to move onto its next task, dredging of the site will commence in the New Year. With a navigational level of nine metres below chart datum the newly cleared stretch of water will then be available for use by larger modern vessels.

By Jake Frith