Chamber delivery

Cape Clear is Ireland’s most southerly island being 6 miles off Cork’s Atlantic Coast in exposed waters just a few miles from the Fastnet Rock Lighthouse. To protect the island’s boating fleet during severe storms the Irish Department of Agriculture Food and the Marine have commissioned hydraulically operated storm gates to enable the inner harbour to be rapidly closed off. These gates require a substantial concrete structure to accurately hold and align the gates, in a water depth varying from 4 to 8 meters.

In response to the Department’s tender invitation L&M Keating Ltd. offered a novel solution involving the precasting of the lock in a dry dock in Cork Harbour and installing temporary steel stop logs to form an enclosed chamber that would float. This chamber was then towed to site and sank on to a prepared concrete base.

After a week of pre tow preparation in the dry dock involving the installation of a deck, emergency pumping arrangements, ballasting, fitting of navigation marks and sea fastening works, the sea structure was towed to sea the morning of Saturday 28th September.

The chamber was towed by the 4,000hp tug Celtic Isle provided by the Mainport Group, and was accompanied out of Cork Harbour by the Port Authorities tug Gerry O’Sullivan.

Once at sea the chamber was towed at an average speed of 3.5kn. The tow was then transferred to the smaller vessels Barracuda and Souris, and was brought into its final position against temporary steel guides. As the tide dropped the chamber followed the guides down until it rested on a concrete bed prepared earlier by divers. Once on the bottom, the chamber was flooded to prevent it floating off again.

The works are part of a €4.3M development which includes a 70m slipway, automated hydraulic storm gates (12x8m) and reconfiguration of the existing harbour entrance.

Work now continues to tie the quay on each side of the structure into the chamber and seal the chamber with grout so work to install the electrical and hydraulic systems can commence.

L&M Keating has offices in Clare and Dublin and continues to work on projects throughout Ireland and the UK. Their civil engineering division is best known for their design and build of marine based developments around coast of Ireland. Recent and current major works include Rossaveel floating ferry terminals, Inishboffin harbour development, Knightstown floating breakwater development and Arklow dredging. L&M Keating’s civil engineering expertise includes dredging, harbour construction, outfalls and piling.

By Jake Frith