NEW BRIGHTON AIDS TO NAVIGATION STRUCTURES

Project details

New Brighton is a seaside resort forming part of the town of Wallasey within the Metropolitan Borough of Wirral, Merseyside. Located within an area of foreshore known as Fort Perch Rock, 3no. Aids to Navigation Structures were constructed in the 1980’s to mark submerged offshore coastal defences, providing safe navigation within the Mersey Estuary. Following recent inspections of the structures, significant corrosion was identified, resulting in a decision to replace the existing structures, an obligation under the Merchant Shipping Act. The project was subsequently awarded to Southbay as a two stage ECI contract. Phase 1 involved the agreement of target cost and finalising the design of the new structures. Phase 2 involved the onsite construction of the Navigation Structures.

508mm diameter concrete filled monopile complete with sleeve.

The initial proposed design retained the existing tripod arrangement of installing 3no. tubular steel piles. However, due to a restricted budget, and the need to install the piles within a tidal environment, we successfully developed an alternative simplified design. This design involved replacing the tripod arrangement with a single 508mm diameter, concrete filled monopile complete with sleeve.

The 3no. Aids to Navigation structures were installed from a jack up barge due to the need to work within the intertidal zone. The jack up barge included a two-tier piling gate which was used to pitch and install each pile. In addition to a piled foundation, the Navigation Structures also include a superstructure, which consists of a steel gantry complete with handrailing and access ladder. The superstructure was prefabricated off-site, allowing it to be installed in a single lift, thereby minimising the onsite programme. The new Navigation Structures include a single fixed light and daymark which can be seen for three nautical miles. Upon installation of the new structures the existing were removed. The onsite works were delivered across a 5-week programme.

In delivering the project, significant planning was required in relation to the transportation of materials to the 3no. locations. This included the safe trans shipping of 26m long tubular piles from a supporting flat barge to the jack up barge, programmed across a 40-minute tidal window which coincided with high tide. Careful planning of the deck load out of the jack up barge was also required to ensure all materials were within the operational radius of the crawler crane. All barge movements were co-ordinated using a multi-cat and tug vessel.

 

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