2017:162 - Portraine Demesne, Dublin

Excavation became necessary following the discovery of a possible cist burial during a monitored topsoil strip (Licence Ref: 17E0210) over the footprint of the proposed National Forensic Mental Health Services (NFMHS) hospital site at St Ita’s Hospital, Portrane Demesne, Co Dublin. The site was unearthed on 18 May 2017.

The excavation focussed on possible prehistoric remains located in the southern end of the Mental Health Intellectual Disability (MHID) unit of the NFMHS hospital site.

Excavation of the site of the possible cist burial and associated features was carried out between 10 July and 3 August 2017. A team of five archaeologists carried out the excavation. An area measuring 6m north-south by 37m was stripped and excavated to mitigate for the dispersed nature of the archaeological remains.

The natural subsoil was a yellowy-brown, sandy, silty clay of glacial origin, with weathered stone inclusions and a large concentration of roots throughout the site. It should be noted that the possible cist and associated features were unearthed on the edge of the treeline defining the southern edge of the avenue to Portrane House. The frequent root activity was present in almost every feature that was dug, including the possible cist.

During stripping, the topsoil of the site showed a large presence of flint, some of which showed signs of working. The presence of flint increased in frequency towards the western-end, downslope portion of the site.

Ten archaeological features were found at the west end of the site: nine pits and a ditch extending beyond the northern and southern limits of the excavation. The northern limit of excavation is the old avenue to Portrane House while the southern limit is the treeline. It was not possible to extend the excavation beyond these limits.

On the east end of the site, a number of features appeared to be modern post-holes. Excavation indicates that some features are post-medieval to modern in date. These features form an alignment of post-holes, running from the north-east to the south-west. These may have been structural.

The possible cist burial site was contained in an earth-cut pit. The possible cist was formed by 12 upright stones capped by three slabs that partially covered the chamber. These possible capstones, in turn, supported a further tier of side slabs that lined the upper sides of the earth-cut pit to east and west. Above this the cist/pit was sealed by a layer of overlapping flat slabs. These may represent a collapsed corbelled roof structure or the remnants of a covering cairn.

35 Brook Meadow, Avoca, Co Wicklow