2008:150 - Aghada Power Station, Aghada, Cork

Monitoring of the excavation of a marine pipeline trench and intake apron was undertaken adjacent to Aghada Power Generation Plant, Aghada, Co. Cork. These in-water constructions are part of the extension/upgrading works to the power plant facility and include the provision of an outfall pipeline to discharge cooling-water from the plant turbine and dredging an intake apron to provide coolant to the turbine. The outfall pipeline extends c. 450m from the existing shoreline (north-west/south-east orientation) and a pipe-trench was dredged to accommodate a 2m-diameter outfall pipe. The dredged footprint for the trench was 39m in width, with maximum slopes graded at a ratio of 1:6 (dependent on material encountered), dropping to a base width of 3m. The trench was backfilled with dredged material. The outfall pipe terminates at a rising diffuser head, above which a maintenance platform has been constructed to allow maintenance access to the diffuser. A 31m (east–west) by 34m area of seabed was dredged to a depth of 3m to accommodate the intake pipe. The dredging process was undertaken by backhoe dredger, using differential GPS, to allow accurate excavation of material at both locations.
A pre-construction assessment of the pipeline route and intake location was undertaken by ADCO Ltd. in June 2004 (Excavations 2004, No. 184, 04D011, 04R038). No archaeologically significant material, structures, or deposits were encountered as part of this assessment.
Monitoring of pipeline dredging was undertaken on a 14-hour basis on 1–7 February 2008, changing to a 24-hour programme on 8–14 February. The intake apron was dredged on 24 March and 2–3 April 2008. It was monitored on a 12-hour basis.
The removal of all seabed material was monitored. Seabed deposits were largely sterile and very little man-made material was observed as part of the monitoring process. The seabed was primarily composed of a grey silty clay deposit with frequent angular gravel and oyster shell inclusions. Across the south-eastern extent of the dredging works the seabed composition changed to a deposit composed of angular gravel and rock fragments, material believed to be overspill from land reclamation that has taken place at Aghada Power Plant. Only one archaeologically significant object, a large iron cannon ball, was encountered during the monitoring programme. The cannon ball is believed to be an isolated find and, due to its size, is thought to be associated with land-based artillery rather than shipboard cannon.