The decision to start work on one of Ireland’s greatest engineering projects, Dublin’s Great South Wall, was taken 300 years ago this week. For Dubliners, such as myself, it is an iconic structure and an iconic place. For is is really only known to Dubliners who like nothing better than to walk two miles along it on a balmy summer’s evening watching the ships come and go while the city and its beautiful bay swirl around you. Then you turn back to return passing the Half Moon Fort, now a swimming club, whilst the twinkling lights of the city welcome you back.
Dublin Bay had a long history of troublesome sandbars obstructing the entrance to Dublin Port and was also subject to frequent squalls and stormy conditions. Dublin Bay had a long-running problem with silting, notably at the mouth of the River Liffey, and held major sand banks, notably the North Bull and South Bull (both hard sand dry at low water, to either side of the Liffey mouth, along with the Kish Bank over 11 km out to sea. Between the North and South Bulls, a sand bar existed, rising over time, limiting access to the city quays. Furthermore, the shape of the Liffey estuary was rather different from the present day, with the river channel not fully enclosed, much of Pearse Street (then Lazey Hill) running along the shore, which then bent sharply south, running in a diagonal to Irishtown, with Ringsend being a narrow sand spit projecting north into the bay.
To improve the situation, in 1716, the Ballast Office commenced construction of an embankment from Ringsend along the north aspect of the South Bull sand bank. The first piles of what was to become the South Bull Wall were driven in 1716 with major work beginning in 1717. The Piles, as The Great South Wall was then known, were completed in 1730 to 1731. Construction involved the driving of long thick oak piles into the boulder clay of Dublin Bay. These piles were anchored by baskets of gravel.
Dublin Port’s Poolbeg stone wall linking The Piles to the quays, The Ballast Office Wall, was completed in 1756. It soon became necessary however to strengthen the walls with massive granite blocks taken across Dublin Bay on barges from the quarries in Dalkey.
By 1795 the wall was completed and was 32 feet thick at the base, and 28 feet at the top. At the end of the wall an island of masonry was laid down on which Poolbeg Lighthouse was built. The lighthouse was ready in 1768 before construction of the wall finally finished and initially operated on candlepower, reputedly the first in the world to do so but changed to oil in 1786. It was re-designed and re-built in 1820. The lighthouse is painted red to indicate ‘port side’ for ships entering Dublin Bay and North Bull lighthouse (on the other side of the bay) is painted green to indicate it is ‘starboard’.
In the meantime, in 1791, the Pigeon House Harbour was planned, while in 1793, a gun battery, named the Half-Moon Battery for its shape, was built about 800m shorewards of the lighthouse. Also around 1793, a hotel, the Pigeon House Hotel was opened. While the Great South Wall protected the ships entering the harbour from wind and high waves, it could not stop the sand from filling up the shipping channels. So in 1801 Captain Bligh, the famous captain of the Bounty, suggested the construction of another wall on the northern side of Dublin Bay. The Bull Wall, as it is commonly known, was finished around 1824 and from then on, Dublin Port never filled up with sand again.
Following temporary military arrangements after the 1798 Rebellion, the Pigeon House Fort was created, maintained from 1814 to 1897. At its peak, it included gates with trenches crossed by drawbridges at the beginning of the wall, quarters for officers and men, a hospital, armoury, magazine and stores. In 1897, the complex was sold to Dublin Corporation for development to include the city’s first major electricity generating station and a sewage processing facility, as well as reuse of the hospital. This followed the installation, between 1878 and 1881, of a sewage pipe along the wall, discharging at the White Bank.
Historically, the Ordnance Survey Ireland used the low water mark of the spring tide on the 8th April 1837 at the Poolbeg Lighthouse as a standard height for all its maps, a practice which continued up until 1958.
Poolbeg Lighthouse, now fully automated, is managed by Dublin Port Company . The Great South Wall on which Poolbeg Lighthouse stands, extends from Ringsend over 4km out to sea. It was the world’s longest sea-wall at the time of its construction and remains one of the longest to this day in Europe.
If you’re looking for a beautiful walk by the sea why not try the Great South Wall walk out to Poolbeg Lighthouse? With free parking at the end of Pigeon House Road and the beginning of South Wall it’s very easy to get to. The walk out and back takes around 40 mins and the reward when you reach the Lighthouse is the really stunning views in every direction. You’d never know what ships you may see arriving at, or leaving Dublin Port.
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