2012:203 - Dublin Castle, Dublin

Works undertaken to improve access to the Revenue Stamping Building in the Lower Courtyard of Dublin Castle were monitored. A series of trenches were excavated to investigate the depth of foundations of the Stamping Building and adjacent perimeter wall, as well as to determine the position and depth of the culverted River Poddle. The main area of excavation was located on the western side of the Stamping Building and was an average of 0.6m deep. Subsoil was not exposed at this level and the excavated material mainly comprised rubble. On the western end of the site was a deposit of soft black organic silt containing fragments of animal bone and shell (012). This deposit extended for c. 2m by 2.5m and was 0.45m deep. It overlaid similar, but firmer clay. A copper alloy pin was recovered from deposit (012).

The location of the Poddle culvert was determined by geophysical survey. The culverted river runs in an east-west direction at the southern end of the site and connects to a manhole at the western end of the Stamping Building. From this point it runs diagonally across the site in a northern direction. Monitoring demonstrated that for most of the length of this area, the Poddle is divided into two culverted channels, which lie 1.3-1.4m below present ground but at the northern end a single culvert lies at 0.5-0.6m.

Wall footings of an earlier boundary wall and the 19^th-century stables that occupied this area were identified on the northern end of the site. No such remains were exposed on the southern end of the site, where the construction of the Stamping Building had caused much more ground disturbance.

The earlier boundary wall was a substantial east-west orientated masonry structure (005) that extended the entire width (9m) of the works area. It was parallel to and c. 4m from the current boundary wall along the south side of Dame Lane. Wall (005) was constructed of regularly coursed blocks of limestone and granite, bonded with lime mortar. It was 1m wide and at least 0.8m high. Abutting its northern face was a north-south-aligned masonry and brick-built wall. This wall was 0.65m wide and was truncated to the north by the existing boundary wall.

In the centre of the site, extending from the southern face of the early boundary wall (005) was a north-south-orientated rubble wall (011). Wall (011) was constructed of stone and red brick bonded with lime mortar and measured 2.2m long, 0.35m wide and 0.34m high. Running eastwards from the northern end of wall (011) and abutting the southern face of wall (005) was masonry wall (010). This wall was truncated to the east by the Stamping Building and its remains measured 4.2m long by 0.6m wide  A surface of crushed red brick occupied the area delimited by walls (011) and (010).

Abutting the western end of the boundary wall (005) and extending south-eastwards from it was a masonry wall (004) measuring 6.5m long, 0.7m wide and over 0.9m high. The southern end of wall (004) abutted an east-west masonry wall (032), 1.4m of which was exposed within the excavation area. This wall was 1m wide and over 0.4m high. Adjoining its southern face was a north-south-aligned masonry wall (033) that was 3.3m long, 0.65m wide and 0.22m high.  Within the room defined by walls (033) and (032) was a surface of crushed red brick and crushed lime mortar with red brick fragments. The latter partially sealed an east-west-aligned masonry wall footing (034) that measured 2.2m long by 0.75m wide. Part of a crushed red brick surface was exposed along the southern side of this wall.

The truncated remains of a rectangular structure were uncovered c. 12m south of wall (034). The structure was at least 6.3m by 7m and had a concrete floor that was probably a later addition. The external walls were constructed of rough-cut limestone blocks bonded with lime mortar. The northern and western walls had been faced internally with red brick and there was an internal wall of red brick construction.

A north-north-west/south-south-east-aligned masonry wall was located c. 9m north-west of the rectangular structure and a 1.7m-long stretch of this wall was uncovered in a drainage trench. The wall was 0.5m wide and 0.5m high. Another stone wall footing was located 1m further north and a 1m by 0.3m stretch of this wall was exposed. A mortared red brick surface was uncovered to the north of this wall and extended beyond the end of the drainage trench.

An 11.3m by 9.4m area was excavated in the car park on the western side of Palace Street, adjacent to the southern side of the Treasury building. The remains of a red brick and gravel surface set into lime mortar were uncovered at a depth of 0.3m at the south-east end of the dig area and extended under Palace Street. Black organic clay lay at 0.4m and was cut by a brick drain.

A 0.6m-wide service trench was excavated across Palace Street, from the south-east corner of the Chapel Royal towards the south-west corner of the Stamping building. The trench was c. 0.2m deep and the remains of a cobbled surface were uncovered towards its eastern end.

The construction works did not necessitate the removal of any of the exposed structural remains. These were covered with heavy-gauge plastic and a layer of ‘804’ gravel.

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