2015:084 - North Quay & The Mall, Drogheda, Louth

Monitoring of slit trenching was carried out between 24 and 28 November 2014 in advance of the upgrade of a watermain at the North Quay and The Mall, Drogheda, Co Louth. The aim of the works was to establish the location of existing services where not previously known and clarify the extent of archaeological deposits and/or features along the proposed route. The work was carried out on behalf of Irish Water under Ministerial Consent (C291) as the route is adjacent to the medieval town wall of Drogheda, a National Monument.
The site is located within the core of the historic town of Drogheda (LH024-041) and is also adjacent to the medieval quay wall. The route of the proposed upgrade has significant archaeological potential and features previously exposed along the line of the watermain include a 13th-century timber revetment along the North Quay, the medieval quay or river wall, a number of structures (possibly representing crane bases, towers or other medieval quayside activity), the precinct walls of the medieval Franciscan Abbey, a medieval stone kiln and St Catherine's Gate and town wall. The proposed upgrade will for the most part be kept within or as close as possible to the line of the previously excavated interceptor sewer so as to minimize the impact on archaeological deposits which have been shown to survive to within 0.4m of the existing street level.
A total of 7 slit trenches were excavated within the site. All were excavated to a depth of 1.2m which represents the invert level for the proposed pipe. Four of the trenches were excavated within the area enclosed by the town wall (Trenches 1-4) and three outside (Trenches 5-7). The slit trenches measured a maximum 0.4m wide and varied in length from 2m to 4m.
All trenches showed signs of significant ground disturbance due to previously excavated services including telecom, watermains and gas. The line of the interceptor sewer which was archaeologically excavated between 1996 and 1997 was also evident in a number of the trenches. Despite the previous disturbance, medieval archaeological deposits were exposed in portions of the four trenches excavated inside the line of the town wall. Two of the three trenches excavated outside the town wall confirmed the deposits in this area represented late 18th- to 19th-century reclamation as has been shown by previous excavations and cartographic evidence (Ravell’s map of 1749). The archaeological deposits exposed inside the town wall along the Mall comprised principally of brown garden soils containing medieval pottery and animal bone similar to what was uncovered during the Drogheda Main Drainage Scheme in 1996-7. Trench 4 excavated directly inside the line of the town wall did not expose the wall but the entire trench consisted of medieval deposits which were exposed at a depth of 0.4m and which produced a medieval green glazed floor tile. The town wall is therefore likely to be present to within 0.4m of the existing ground surface at this location.
The proposed watermain upgrade will be excavated to an invert level of 1.2m and unless it can be laid entirely within the previously excavated Interceptor Sewer, it will impact on archaeological deposits. The limited nature of the slit trenches made it difficult to assess whether archaeological features are present within the medieval deposits exposed but from previous excavations in the immediate vicinity we know that these deposits contained kilns, medieval walls, cobbled surfaces and other features so the likelihood is that further archaeological features will be uncovered during the excavation for the watermain upgrade.

Archaeological Consultancy Services Unit, Unit 21 Boyne Business Park, Greenhills, Drogheda, Co Louth