County: Dublin Site name: Great South Wall, Dublin
Sites and Monuments Record No.: DU019-029002- Licence number: 15E0454
Author: David J O'Connor
Site type: 18th-century marine structure
Period/Dating: —
ITM: E 722302m, N 733900m
Latitude, Longitude (decimal degrees): 53.341179, -6.163400
Monitoring of ground investigation (borehole) works on the Great South Wall took place between 19 October and 26 November 2015. Five boreholes were drilled in total, located along the length of the wall. The Great South Wall is both a Protected Structure (RPS 6797 & 6798) and a Recorded Monument (RMP DU019-029002-). The works took place following consultation with both Dublin City Council and the National Monuments Service. A Section 5 Exemption Order was issued by Dublin City Council for the works. The National Monuments Service requested an archaeologist monitor the investigations.
Main Findings
The Great South Wall differs in height, ranging from 6.5m (3.66m to -2.84m OD) near Poolbeg Lighthouse to 3.5m (2.35m to -1.15m OD) at White Bank Wharf. The wall appears to be of uniform construction throughout its length, built almost entirely of cut granite blocks and stone gravel (shingle) fill. Some limestone and sandstone was also used in the lower layers. Cut granite blocks were set dry on the sea bed, flanked by two retaining walls. The voids between the blocks were filled with stone gravel (shingle). The blocks appear to have been laid in layers. It also appears tthat up to 6 inches (0.16m) of gravel separated each layer of granite blocks within the core of the wall. In one area sand appears to have been used instead of gravel. The base of the wall sits on up to 10m of sand for its entire length. Strata of gravel, shale and boulder clays occur beneath the sand, while solid rock was found between 30-45m below the top surface of the wall.
Possible Wreck
Borehole BH 3 (Half-Moon Battery) appears to have struck timber 0.5m below the base of the wall (-2.46m OD), within the sand layer. Nothing was recovered from the core but the location and depth would suggest a possible wreck sealed within the sand under the wall.
Conclusions
While no physical evidence was recovered from Borehole BH 3, it is possible, given the machine vibrations, location and depth, that a wreck was encountered at the Half-Moon Battery.
Magnus Archaeology, 57 Grianan Fidh, Aiken's Village, Sandyford, Dublin 18
