Larne Harbour

The Brief

The challenge presented to AW Solutions by McLaughlin & Harvey was to design and install a specialist access system suitable for the underside of a concrete mooring dolphin, to facilitate repair of the concrete.The level of the work platform needed to be approximately 1.5 metres below the concrete soffit in the mid-tidal range in Larne Lough (tidal estuary).

The client, Port of Larne and McLaughlin & Harvey needed a solution which would have no adverse impact on the daily berthing movements nearby and at intervals of 3 hours of the Larne – Cairnryan ferry.

Floating plant was therefore precluded as a form of access as it would have been an obstacle to ferry movements.

The form of access had to be economical, quick to assemble with sometimes as little as 4 hours daily working dependent on tide levels.

The completed work platform also had to be designed to cope with the ebb and flow of the tide being completely submerged for approximately 10 hours in any 24 hour period.

From the brief presented, AW Solutions were aware of the very onerous working environment for safety and practical reasons, the close proximity of a berthing vessel and the project timescale set by the client.

McLaughlin & Harvey already had a temporary access platform design prepared, prior to AW Solutions getting involved.

The Solution

A revised brief was prepared by AW Solutions and presented to Zenith Structural Access Solutions, knowing their partner company were involved in a specialist access and repair project on a jetty structure in the Forth estuary in Scotland.

The specialist access design which already existed had drawbacks because the members were heavy, not suited to a marine installation working over deep water and would have been difficult to install.

Zenith’s in-house structural engineers prepared an alternative tailored specialist access design for a system which was lightweight for quick installation, yet robust enough to cope with tidal movements and therefore cost effective.

Despite the restricted hours of working due to tide levels, the structural access platform was installed in less than 2 weeks with no need for floating pontoon assistance enabling repair work to start on programme.

The stable platform provided also assists with environmental aspects of the project like the necessary capture of debris avoiding pollution of the Lough