Significant underwater erosion is threatening the foundations of Dún Laoghaire harbour's east and west piers, The Irish Times has learned.
The erosion, identified in an underwater survey commissioned by the Harbour Board last year, is expected to cost up to €13 million and take several years to repair.
A planning application for the first stage of the repairs is to be lodged with Dún Laoghaire-Rathdown County Council next week. The application is required as the piers are listed structures in the county development plan.
The first phase of the work will involve repairs to the granite shell and rubble interior of the East Pier, which was built from 1817-1847 and is held in place by granite blocks originally hewn from quarries on Dalkey Hill.
Also in the first phase will be the replacement of the granite surface of parts of the pier, which have become worn, uneven and represent an insurance risk.
The new granite for the harbour is to come from Co Carlow. The cost of repairing the East Pier is estimated at €3 million.
However, the scale of the problem on the harbour's West Pier is even more serious, with the estimated cost of repairs being put at €10 million.
Work on the repair of the West Pier is not expected to begin until a planning application is submitted and approved by the county council.
According to the chief executive of the harbour company, Mr Michael Hanahoe, the work "is serious" but does not have to be all done at once, which, he remarked, suited the company's finances.
"Work will start soon on the East Pier and after that we will have to budget for the repairs on the West Pier on an ongoing basis," he said.
Mr Hanahoe added that while the state of the piers was disappointing, "it is not surprising after about 170 years in place".
The first stone of the harbour was ceremonially laid by Lord Lieutenant Whitworth on May 31st, 1817, and when completed the harbour encompassed 251 statute acres.
Following the completion of the piers other works continued including: Traders Wharf, the Carlisle/Mail Boat Pier, the Coast Guard Station, and TCD Prof Robinson's Anemometer on the East Pier, which measures wind speed and direction.
The total cost of the harbour works was £825,000.
