13 November 2009

The Kish Lighthouse

 When I was 10 years old I was brought to the Coal Harbour in Dun Laoghaire to see a most unusual structure being built. It was a series of concentric tubular sections of reinforced concrete designed to slide into one another. Imagine my surprise to hear that it was to be a huge 150' tower built of weighing over 6500 tons - and furthermore it was going to be a lighthouse! Living in Cobh overlooking Cork Harbour including Roches Point has always given me a huge interest in lighthouses - to me this was mind blowing.
This unique feat of engineering was the construction of the Kish Lighthouse tower by a Danish firm for the Commissioners of Irish Lights.
In mid-July 1965 the completed structure had been towed six miles to its eventual resting place and sunk into a prepared seabed and then the telescopic tower was raised to its present height of over 100 feet above sea level.

The telescopic design had been used before by the Swedish Lighthouse Board, but these towers were smaller than the Kish and were located close in-shore. So, in terms of size and location, this the Kish is unique.
In spite of the scale of the structure, the basic principle of the telescopic tower was simplicity itself. It comprised two circular watertight chambers, or caissons, the inner one being the tower itself.

Part of the outer caisson was flooded to sink the structure on to the seabed. Its central chamber was flooded to float the tower through 50 feet to its full height, with final adjustments made by stressing cables and jacks. Gravel was then pumped into the water-filled chamber to give the tower a permanent base.

The Kish Bank had been marked by a Lightship since 1811 and an unsuccessful attempt to put a permanent Mitchell screw pile lighthouse there in 1842. On 7th April 1992 the lighthouse was converted to automatic operation and the Keepers were withdrawn from the station. The white tower with a red band is located some seven miles east of Dun Laoghaire.

 

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