1999:571 - DROGHEDA: John Street, Louth

This report describes the results of a fourth phase of test excavation at the proposed development site on John Street that is part of the Drogheda Town Centre Bridge Development. The site is adjacent to the McDonalds restaurant on the southern side of the River Boyne. This phase of excavation was carried out between 6 and 9 September 1999 under an extension to an existing licence issued to Edmond O'Donovan for assessment at the site (Excavations 1998, 143). The purpose of the additional test excavation was to find the position and, in particular, the level of the old town wall and its external ditch. It also sought, without damaging them, well-preserved masonry elements of the 19th-century tannery on the site, to more fully address the context and date of other possible masonry features uncovered in earlier assessments (O'Donovan, Phases I–III).

Previous attempts to test the site were significantly hampered by the amount of rubble on site, and without open-area ground reduction an interpretation of possible features was not feasible in slit-trenches. An extremely cautious approach to the presentation of level information was taken as a result, and some levels quoted for possible features in Phases I, II and III had actually been taken from heavy, bonded rubble in the test-trenches.

The Phase IV assessment was designed to record in as comprehensive a manner as possible the archaeological potential of the site, focusing on the level to which structures survived in order to finalise the structural engineering design and impact assessment.

The assessment required the ground reduction of an area measuring c. 400m2 to the base of a rubble infill across the site. The large site possesses the substantial subsurface remains of the old tannery. Before assessment, the site had a slightly raised surface that has been grassed over. A deep deposit of rubble fill derived from the demolition and clearance of the tannery buildings and dumping connected with the John Street Road Improvement Scheme and the main drainage schemes covered the entire site.

During Phase I testing, masonry walls were revealed in two of the trenches (11 and 12). The wall from Trench 11, at the north-east corner of the site, was 4m long and 1.5m wide and was found at 4m OD. In Trench 12 the top of a 1.12m-wide wall was found 1.27m below ground level (3.25m OD). This wall comprised limestone bonded with mortar and was found along the line of the town wall. The Phase II archaeological assessment saw further trenches excavated across the site (Trenches 15–17). Masonry walls were revealed in two of the trenches (16 and 17), along with the remains of a possible stone platform (Trench 15). The wall from Trench 16 lay at 2.1m below ground level; however, it was not possible to determine its orientation or indeed its full dimensions. In Trench 17 the uppermost deposit was clay loosely mixed with red brick and large, angular limestone blocks, 1.4m deep, which overlay a masonry structure (likely to be a wall). This wall appeared to be 1.2m wide and was oriented roughly north-south. It was built from large limestone blocks and was bonded with a sandy, crumbly mortar; red brick was present, bonded onto the upper surface of the structure. Trench 15, at the north-east corner of the site, 8.2m long and 2.4m wide, revealed what was initially thought to be a substantial curved masonry wall and surviving element of a medieval mural tower. The feature comprised a substantial, level, 8.2m-wide masonry platform lying at between 3.53m and 3.73m OD. The platform had a rough masonry surface built from tightly packed angular limestone blocks and was covered by deposits of loose, modern demolition rubble and dump made up of clay loosely mixed with limestone blocks. These deposits were between 0.9m and 0.7m deep.

The projected line of the town wall and ditch bisects the proposed development site. The town wall remained intact up to 1837, shortly after which a large tannery was developed on the site; however, the line of the wall remains evident within the tannery and can be identified on the 1862 OS map. The tannery and any remaining upstanding fragments of the town wall were demolished with the construction of the new Drogheda inner-relief dual carriageway along John Street.

The substantial wall uncovered in Trench 12 and the masonry identified in Trench 11 were interpreted as possible constituents of a circular feature and therefore as possible elements of the medieval defences of the town. Clays and pits thought to be of medieval date were also identified at the eastern end of Trench 12. No clear sign of a ditch or moat was revealed to the west of the projected line of the town wall, a portion of which was uncovered during the excavations carried out before work on the Drogheda Main Drainage Scheme by ACS Ltd. Phases I-III testing was unsuccessful in establishing whether the structures exposed belonged to the tannery or were earlier in date.

Phase IV
An area measuring a maximum of 102m (west-east) by 38m was reduced in level. The supervised mechanical removal of the site's rubble overburden revealed the base level of disturbance, invariably exposing the truncated and foundation remains of the 19th-century tannery. The assessment was directed not to disturb the intact remains of the tannery, and no masonry structures were to be dismantled.

The site was covered by heavy, compacted rubble, representing the collapsed remains of the old tannery, accompanied by dumps of rubble derived from demolition that occurred as part of the John Street Road Improvement Scheme. This overburden varied from 1.5m to 2.4m deep, with a notable concentration of large masonry debris through the central portion of the test area, corresponding with the possible stone platform revealed in Phase II, Trench 15. As a result, no remains of a mural tower were found, and on removal of the rubble, which most certainly had been interpreted as the possible remains of a tower base, the truncated remains of the tannery were found.

Two buildings belonging to the old tannery (Structures 1 and 2) were revealed west and east of the projected line of the town wall. A wall (Structure 4) was found running along the projected line of the town wall, flanked on the west by a covered stone drain (Structure 3) and to the east by a masonry structure (Structure 2) from the tannery. At the north end of this combined structure, extending into the northern section on the western side, lay a series of limestone steps (Structure 5). Lying immediately west of the covered drain, Structure 5 appears to correspond to a section of masonry revealed in Phase II, Trench 17.

Structure 1
A series of conjoined and interrupted walls of a two-roomed tannery structure was revealed along the northern part of the site, west of the projected line of the town wall. The structure was oriented west-south-west/east-north-east and was 32m long (west-east) and 10m wide, with 0.5–0.9m-thick walls, the top of which lay between 2.23m and 2.29m OD. The remains of a path consisting of flat slabs were found adjacent to the western gable end. There was at least one doorway in the north wall. The walls were constructed of rough limestone blocks in double-wall form with a limited rubble core, bonded with a gritty lime mortar and occasionally augmented or repaired with red brick. The interior of the structure was characterised by a 'floor' or spread of tannery waste, including cinder, charcoal and slag, as well as crushed stone and brick, not over 0.1m thick. The internal floor levels were recorded at 2.09m OD on the west, rising to 2.51m and 2.2m OD on the east. This building is immediately west of Structures 5 and 4, flanked by a stone-/brick-lined drain (Structure 3) that lies directly along the projected line of the town wall. The lack of correspondence to any of the structures depicted on the 1862 25-inch OS map confirms that the building represents a later tannery construction.

Structure 2
A series of three conjoined walls with a further interrupted stretch represents a building 14m long by 9m wide. Its alignment, similarity of construction to Structure 1 and associated context define this building as part of the tannery, even though, as with Structure 1, it does not correspond to any of the structures depicted on the 1862 25-inch OS map. Clearly the mapped layout of the tannery changed or, more accurately, was developed over time. The walls of Structure 2 were between 0.5m and 0.9m wide and at least 1.1m high (top between 2.46m and 2.05m OD; base exposed at 1.78m OD). They were constructed of rough limestone blocks in double-wall form with a limited rubble core, bonded with a gritty lime mortar occasionally augmented or repaired with red brick. The interior faces of the conjoined walls were lime-washed, with the 'plaster' surviving up to a thickness of 0.05m. Partial removal of the 'fill' of the structure revealed limestone and brick rubble on the western side and large, compacted, water-rolled stones and boulders on the east. The interior of the structure was quickly inundated with water from the River Boyne during excavation.

Structure 3
Structure 3 comprised the remains of a stone- and brick-lined drain running parallel to a wall (Structure 4) and overlying Structure 5. The drain, which lay directly along the projected line of the town wall, was exposed for a length of 30m, extending beyond the excavated area to the north and south. It was 0.5m wide and up to 0.18m deep. It was built of irregularly shaped limestone and half-bat red brick, portions of which were mortared, and it had a possible cobbled floor. The top of the drain lay at 2.66m OD at highest and 2.29m OD at lowest. The drain lintels were a mixture of flat limestone slabs, slate and large iron plates and bars. The interior of the drain was partially filled with rubble and tannery waste, including fragments of glass, leather, wood and patterned ceramics.

Structure 4
Structure 4 was a limestone masonry wall lying directly along the projected line of the old town wall, flanked on the west by a covered stone-lined drain and by the western corner and wall of the tannery building. In stratigraphic terms Structure 4 pre-dates both adjoining structures, although the dimensions, build and form of the wall strongly suggest that while it lies along the projected line of the town wall it is not a medieval wall. It is nevertheless quite reasonable to assume that both Structures 3 and 4 may encapsulate part of the foundation of the original town wall or, at the very least, were built on its foundation. That the town wall was demolished before the construction of the tannery is not in question; what is questionable is the degree of removal of this structure before the construction of the tannery. The 1862 OS map of the site clearly shows a major north-south wall running through the tannery along the line of the old town wall. A 0.9–2m-wide section of the wall was exposed for a distance of 36m (north-south). The top of the wall was higher to the south, 2.68m OD, and lower to the north, 2.52m OD. Four modern steel uprights, equidistantly spaced at 3.07m, were found driven into the wall. These fixtures are of the type used in modern steel railings and would suggest that, at a late stage in the use of the tannery, the wall, which likely functioned as a boundary, was partially demolished and replaced with metal fencing.

Structure 5
Structure 5 is at the northern end of the excavated area, over the projected line of the old town wall. The constituent masonry remains, though partially disturbed, comprise a series of steps at the southern end. They lie below the drain identified as Structure 3, but their relationship with the adjoining wall, Structure 4, was not fully established, as this would have required the partial dismantling of Structures 3 and 5. On plan, however, it would appear that the drain forms the top step of Structure 5, and, while there are no corresponding steps to traverse the adjoining wall (Structure 4), it would appear that Structure 5 extends beyond the section to the river wall, linked with the drain (Structure 3). In the Phase II assessment, Trench 17, the excavator revealed the remains of a wall up to 1.2m wide, oriented roughly north-south and built of mortared limestone blocks augmented with red brick at a depth of 1.4m below ground level (3.9m OD). Phase IV assessment has now established that this feature represents the continuation of combined Structures 3–5, and possibly Structure 1. The top of Structure 5 corresponds with the top of the drain, being 2.33m OD at highest and 2.29m OD at lowest, and would appear to lead to a series of quayside steps depicted on the 1862 OS map.

Tannery pits
On clearance of the rubble overburden from the site, spreads or deposits of cinder, charcoal and slag measuring on average 10m by 6m were revealed. The deposit varied between 0.05m and 0.12m thick and was also found as floor material within Structure 1. It was found mainly in regular, rectangular spreads to the south of Structure 1, between 2.33m and 2.21m OD, and also to the east of Structures 2, 3 and 4. In the latter area, in particular, regular spreads of this waste material between 2.35m and 2.31m OD suggested the surviving remains of tanning pits/areas, the former containment of which was either by wooden frame, as found in the north-east corner of the excavated area, or stone wall. The position of these tannery pits corresponds with those depicted on the 1862 OS map. Once found, excavation below these structures was avoided, except at one location, where a test-pit was excavated to establish whether the town ditch lay parallel to the projected line of the wall.

Revetment
A test-trench c. 9m by 9m was excavated through the level of the tannery pits/waste spreads to establish whether the town ditch survived in this area. The ditch was not found. However, below an orange clay layer 0.8m deep (essentially the foundation for the tanning pits) lay remains of a wooden, east-west-aligned revetment. The exposed remains comprised a large upright wooden post 0.7m in diameter (1.63m OD) with an upright split wooden plank held or braced by a narrow wooden post set at 45 degrees to the plank. At the western side of the test-trench a split wooden plank, lying horizontally, was found at 1.7m OD. To the north of the line of the revetment was a deposit of grey/blue, compact, estuarine clay, and to the south of the revetment lay wetter, blue clay, also estuary-derived. Nineteenth-century pottery was found within the estuarine clay immediately north of the revetment.

Deposit stratigraphy
In general, immediately below the thin layer of sod that covered the site lay a mixed, rubble-filled deposit comprising loose, brown clay and sand with copious amounts of brick, stone and concrete rubble, as well as quite a number of very large limestone boulders. In most cases the rubble deposit overlay the demolished remains of structures or the truncated remains of tannery pits. Therefore the top of these structures invariably reflects the basal level of the rubble horizon across the site. It should be pointed out that several of the possible structures identified within the test-trench programmes of Phases I–III were misinterpreted as structural remains, owing to the size of the trenches opened, when in fact they represented collapsed and dumped sections of brick or limestone walling. The invariably restrictive nature of the process of narrow test-trenching can, for this site at least, be shown to be insufficient in determining the nature, context, relationship and even the verification of structures.

Summary
No medieval masonry structures were revealed within the excavation area. Of the five building structures recorded, two were tannery buildings, one was a covered drain with associated 'walkway and steps', and one was a north-south wall that, though on the projected line of the old town wall, was in fact an internal division wall within the tannery complex. It seems likely, given the location of Structures 2 and 4, that some remnants of the town wall survived on the site before the construction of the tannery. If this were the case, it is possible that the medieval town wall was used to provide a foundation for later tannery walls.

At the same level as the tannery walls and pits, lay regular spreads of cinder mixed with charcoal, slag and crushed brick (between 2m and 2.35m OD). In the north-east corner of the excavation area, in particular, these spreads, which were largely of cinder, were contained within wood-lined tanning pits. Elsewhere this material, occasionally augmented with fine sand or yellow clay, could be clearly seen cutting into a layer of orange clay. This was most notable to the west of Structures 3 and 4, where the orange clay, up to 0.8m thick in places, was also cut by the foundation of Structure 1. Occasional spreads of light brown/orange, mottled clay were found at the interface between the tannery horizon and the underlying clay 'cap' (2.23m OD). Finds from this particular deposit contained mainly post-18th-century debris; however, a least two sherds of medieval character were recovered. It is possible that this material was redeposited and therefore contaminated with later material; it remains unclear from where it derives. Below the orange clay, on the western side of the excavation, lay several deposits of estuarine clays or silts (2.42m OD) further characterised by the discovery of part of a timber revetment. Material recovered from beneath the orange clay, within the estuarine silt, was post-18th-century in date.

The excavation strategy required that the levels below the rubble be left intact, so, apart from the single test-pit on the western side of the excavation, no further intrusive work was carried out. Medieval deposits, possibly reclamation material, certainly survive at a lower level but will not be affected owing to the proposed construction rafting over the surviving tannery remains.

2 Killiney View, Albert Road Lower, Glenageary, Co. Dublin