2007:493 - DUBLIN: National Conference Centre, Spencer Dock, North Wall Quay, Dublin

A programme of monitoring throughout the winter of 2006–7 resulted in the discovery of masonry foundations at the Liffey end of this development site. The masonry structures were located at c. 0m OD and initially appeared to consist of two substantial parallel walls, 33m in length and some 8.5m apart, with evidence for a formalised break or entrance towards the centre of the northern wall. On consultation with the National Monuments Service of the DoEHLG, the monitoring licence was altered to cover the excavation of the structures and this operation commenced on 29 January, finishing on 16 February 2007.

A trench, 35m (east–west) by 15m, was opened and secured around the structures as they were initially exposed and the excavation was effectively undertaken on a platform while the surrounding area was in the process of being bulk reduced.

The primary deposit upon which the structures were founded, F83, was exposed and mechanically excavated after the structures had been recorded and removed. Underneath this were natural waterborne deposits, with little evidence in artefactual terms for the 18th-century reclamation deposits recorded elsewhere along the banks of the river. Within these natural deposits were the Mesolithic fish traps later excavated by Melanie McQuade at minus 4.66m OD under the same licence (see No. 494, Excavations 2007).

The structures recorded were F5, which mainly comprised F28, a substantial masonry and brick wall, constructed with several interior compartments, and F33, which was identified as the foundation of the southern façade of the Midland Great Western Railway terminus, constructed immediately prior to 1864.

Both structures were of similar length, a function of their occupying the same plot width (c. 33m), and demonstrated something of a symmetrical relationship. The walls returning north from F28 were, however, cut by F33. With no obvious intention to tie both structures together it would thus appear that the railway façade and the station behind were constructed at a later date. The significance of the structures from an archaeological perspective lies in the way their foundations were constructed through the soft waterlogged deposits directly underneath and the different means by which their structural stability was maintained.

The earlier structure had no presence on any of the historic maps and consisted primarily of three walls which enclosed an open rectangular area, the northern part of which was truncated by the insertion of the F33 railway structure. The southern wall, F28, was the most substantial, with F51 returning to the north on its eastern side and a similar wall, F52, returning north on the western side. The area thus enclosed was accessed by means of a flight of granite steps through F51.

The southern and most substantial wall, F28, effectively constituted two walls, which converged slightly at the eastern end. Incorporated into the build of the southern wall were ten north-facing recesses, which were in turn accessed by opes through the northern wall. Two of the recesses were inaccessible and this appears to have offered an opportunity to build in a wider foundation at these locations along the northern face of the wall. The recesses may well have been formed by the buttressing of the southern wall of F28; however, they appear to have had their own discrete function as well.

The whole structure spanned the entire width of the excavated area and remained consistent in build over the course of its 33m length (with an 8m central section in brick). It generally survived to a height of 1–1.2m and was 2.4m in width (with the northern wall being noticeably thicker than the southern wall). For the most part the wall was constructed in calp limestone masonry, using roughly squared or regular flat stones. The roughly squared or rectangular blocks measured as much as 0.25–0.36m in length. Longer, thinner blocks, measuring up to 0.45m in length and 70mm in width, were also present in the fabric.

The masonry was held together by means of iron straps, some of which were 1 inch and others 3 inches in width, which were embedded within the binding mortar. Possibly because of there being no timber support for the masonry foundation courses, the structure demonstrated noticeable subsidence at its eastern end.

The principal distinguishing feature of the wall was the two sets of five irregular-sized openings spaced at identical intervals at either side of the brick section facing north towards the open area, some of which had been blocked off in brickwork. The opes initially presented as basement level windows with brick reveals; further investigation indicated that the opes accessed small chambers within the thickness of the wall, or what effectively was two walls.

The four western chambers were vaulted in red brick; their (blocked) opes arched in a similar though not identical brick. There was some evidence of a similar arrangement to the east, where more of the wall had been truncated in antiquity, leaving the chambers open from above. The opes sat over large cut granite sills, flush with the facing masonry of the northern wall. The brick reveals on either side were neatly finished in a similar, though not identical, brick to that in the central section of the structure. The sills had at one stage held upright timbers supported by a recess in the brickwork on the reveals, possibly indicating sluice-type openings.

While the function of these spaces remains unclear, there are at least two possibilities as to their presence within the wall. It is possible they were used to store a dry bulk material, via a shaft ascending up to street level, where the material would have been poured in to fill the space. A sluice arrangement enabled the material to be taken away at the lower level. There was, however, nothing left at the base of the spaces to indicate what had been stored or moved through there and barrels may therefore have been unloaded down the chutes to the lower interior level.

It is additionally possible that the spaces were formed when buttressing was added to support the southern wall of the F28 structure. The whole structure, together with the railway terminus, was built on very soft reclaimed ground with a high water content, and an obvious slope from north to south is evident in all the structures recorded. The granite steps also lean towards the south, suggesting the subsidence and slippage of the structure. Structural instability would have caused some concern and encouraged an effort to secure or consolidate the foundations. The spaces at either side of the buttresses may therefore have been thus created and a particular use put to them.

The function of the F5 structure has not been elucidated; however, it clearly pre-dates the railway terminal to the north. A Brocas engraving of a fire at a milling complex on the North Wall Quay of c. 1810 would appear to depict a substantial structure just to the west of a prominent windmill, the foundations of which were excavated by Melanie McQuade on the adjacent site to the east (Excavations 2004, No. 565, 03E0654). It is therefore possible that the spaces and sluices within the F28 wall were used to discharge grain to the lower surface to be brought over to the mill; however, there was no evidence for residual grain within the spaces and one would have imagined that the traffic would have been in the other direction.

If the F5 structure is part of the milling complex, which on the evidence of the engraving appears to have suffered a serious conflagration, although one must enquire as to the absence of evidence for the fire over the area in question. If the fire did not extend this far to the west, is it likely that the whole complex would have been demolished prior to 1836, presumably to clear the area for renewed development?

The F33 railway wall was a substantial structure founded on six masonry piers connected by infilled stone and brick relieving arches, the whole structure being supported on timber rafts and piles. It spanned the entire width of the plot and a central entrance was signalled by a slightly larger span between piers, which supported massive chamfered granite blocks supporting cast iron supports at the contemporary ground level.

The façade of the railway station initially appeared haphazard, an untidy collection of arches and piers with little consistency apart from the symmetry evident at the central entrance. On more careful evaluation, the structure was seen to have been very carefully built, with the rafts being constructed directly under the piers with some precision, a good standard of masonry applied in the stone and brickwork above with obvious attention given to the structural arches and their relationships to the piers. The structure survived until 1967, when it was destroyed by fire and comprehensively demolished.

The greater picture of the development of the site involves the transformation of the North Wall polder from the initial concept of a residential quarter into what it became, effectively a light industrial area with some residential and commercial functions. There are several reasons related to the trajectory of 18th-century residential development of the city as to why the North Wall polder was never occupied to the same extent as, say, the city’s development of Smithfield was from the 1660s. It was, to begin with, quite far from the commercial centre of the city, which was slow enough to follow the Custom House in its relocation to the north-east. In addition the polder itself does not appear to have been well engineered in terms of its water defences. The depiction of the area on Charles Brooking’s 1728 pictorial representation clearly shows shipping passing through the newly created Liffey channel, with water shown on the northern side of the quay wall. The associated map shows the finished quay wall with an annotation: ‘this part is walled in but as yet overflowed by ye tide’. Large ponds are still evident along the East Wall on the OS map in the 1830s and indeed the problems with water ingress continued into the 20th century, with severe flooding reported in the 1950s. It was found during the excavation that, despite the pile wall surrounding the site, water ingress occurred at c. 0m OD.