2014:607 - RANDALSTOWN: 161 Portglenone Road, Groggan, Antrim

The site is located at 161 Portglenone Road, Randalstown, Co. Antrim, approximately 2.5km north-west of Randalstown. The proposed development area (PDA) covers an area approximately 85m (north-west/south-east) x 80m and currently comprises a residential dwelling and associated garden space. The site is bounded by Portglenone Road at south-west, Coolsythe Road at south-east, and by agricultural land on all other sides. The current development proposal provides for the redevelopment of existing dwellings, grounds and adjoining infill site to provide 20 dwellings.

Monitored test trenching at the site revealed the remains of a large oval enclosure within the centre of the development site consisting of a subsoil-cut ditch which was between 5.5–6.5m wide and potentially up to 2m deep. Extrapolation of the sections of ditch which were uncovered within each of the test trenches suggests that it is oval in shape and between 30–33m in diameter. The location of this enclosure fits well with its marked location on the early 19th-century 1st Edition OS 6” map and as such clearly represents the monument ANT043:031 recorded within the historic mapping and within the NI Sites and Monuments database.

Within the eastern portion of the enclosure, the ditch was uncovered beneath a 0.4m deep topsoil layer and was capped with a 0.3–0.4m thick deposit of re-deposited subsoil—a subsoil/topsoil mix—which contained fragments of modern pottery. This suggests that the ditch had remained open until at least the beginning of the 20th century, perhaps surviving as a shallow hollow encircling the field and had been deliberately backfilled in order to provide for a more level surface. Construction of the modern buildings appears to have removed most of the overlying topsoil where the building once stood with the building foundations being cut into the upper 0.2–0.3m fill of the ditch (silting deposit F3). Partial excavation of the ditch at several points along its length revealed that it is a substantial feature, up to 6m wide and at least 1.6m deep with the lower half of the ditch being filled with a thick (at least 0.4m thick) deposit of peat material which contained a considerable quantity of brushwood together with larger tree branches which still contained their bark. Either the enclosure ditch was deliberately backfilled with trees/shrubs once it had been “decommissioned” or it had spent a considerable period of time overgrown, perhaps with large deciduous trees and undergrowth/shrubs. In either case this must have occurred a long time ago allowing for the natural waterlogged nature of the ditch to encourage peat development which occurs at a rate of 1mm per year under favourable (wet) conditions.

The enclosure is marked as a “Fort” on the 1st Edition OS 6” map suggesting that it may represent the remains of an early Christian/early medieval rath. The re-deposited subsoil fill may represent the remains of an associated enclosing bank which was pushed back into the ditch when it was backfilled.

Should a bank have once survived along the inner edge of the ditch, and assuming it was between 2–4m wide, this would have allowed for an occupation area of 23m x 17m in extent within the internal area of the monument. No evidence of internal occupation was uncovered during the test trenching. Whether this is the result of removal of any occupation deposits as a result of the construction of the modern dwelling and outbuildings on the site or if in fact the enclosure served some other function such as a livestock enclosure or prehistoric burial monument remains uncertain.

It was recommended that measures be taken which will allow for the integration of the monument into the proposed development design so as to allow for its preservation in situ.