2012:208 - Grand Canal Street District Metered Area, Dublin, Dublin

The Dublin Region Watermain Rehabilitation Project is an initiative which intends to tackle the high level of water leakage from within the water distribution network. The project will seek to identify those areas of watermain infrastructure yielding the greatest sustainable water savings throughout the Greater Dublin Region (GDR). The GDR for the purposes of the project consists of the county council areas of Dublin City, Fingal, South Dublin, Dun Laoghaire Rathdown and parts of Kildare and Wicklow. To date the project has recommended mains in 55 DMAs for rehabilitation.

There are two recorded monuments within the Grand Canal Street District Metered Area (DMA DC000153) that may be affected by the proposed development. The Grand Canal Street DMA lies partly within the zone of archaeological potential for the historic city of Dublin (DU018-020). The other recorded monument (DU018-052) is the site of a grave slab. Watermains rehabilitation is to take place within both of these recorded monuments.

There was a possibility that, should open cut trenching be used, there may have been a moderate direct impact on previously unknown archaeological layers associated with the above recorded monuments.

While an archaeological licence had been issued for archaeological monitoring in 2011, ground works did not commence until 2012; an archaeological presence was required for the monitoring of works in this DMA on occasions between January and May 2012. The works that formed part of the Grand Canal Street DMA consisted of monitoring of open cut trenching within those parts of the DMA that lay within the zone of archaeological potential for Dublin City (DU018-020), which included open cut trenching on Upper Sandwith Street, the southern end of South Cumberland Street and the Fenian Street junction with South Cumberland Street. Open cut trenches and insertion pits were also excavated within 10m of the grave-slab site (DU018-052) on Love Lane.

The process of rehabilitation involved either the exposure of the existing watermain or the excavation of a new trench for a new pipe (new-lay). This was generally carried out with the use of a mechanical excavator of either JCB type or a smaller ‘mini-digger’-type excavator. Where necessary some of the trenches were also excavated by hand.

The trenches typically measured approximately 0.6m in width and ranged from approximately 0.6-1.5m in depth. In some cases larger areas were opened to expose the junction between a number of watermains. Following the removal of the upper surface of tarmac the underlying hardcore/sand was removed.

The excavated trenches and insertion pits on Love Lane were backfilled for the most part with coarse, sticky light brown silty clay with late post medieval/modern deposits typically containing building waste, and cut by large numbers of both active and obsolete service pipes and ducts. The natural subsoil was not exposed in any of the excavated trenches or pits.

The backfill of the extensive open cut trench on Sandwith Street Upper generally consisted of up to 0.6m of loose brown grey-black soil containing moderate-frequent amounts of red brick and mortar fragments, which overlay sticky, fine-grained, light grey silty clay with occasional amounts of red brick and mortar. Patches of rust-coloured discolouration were visible in both deposits, as a result of degraded old cast iron service pipes. In stretches of the trench which necessitated excavation below the sticky silty clay layer, a dark grey-black stony clay deposit was exposed; red brick and mortar fragments were noted on the surface of this deposit but where excavation extended into the deposit it was shown to be sterile and may have been composed of naturally deposited boulder clay.

The majority of the open cut trenching on South Cumberland Street and the Fenian Street junction consisted of shallow road crossings, which generally extended only into the hardcore/sand fills directly below the tarmac; however as a number of large insertion pits were also excavated simultaneously with, and within the vicinity of, the road crossings, these were also monitored. The backfill of these pits consisted for the most part of firm light-mid brown silty clay, with patches of looser, stonier soils; red brick and other post medieval-modern building debris was noted within these deposits and, as with the other monitored areas within the DMA, both active and obsolete service pipes and ducts cut through them.

No archaeological features, deposits or artefacts were revealed during the archaeological monitoring of these ground works.

Archaeological Development Services Ltd. The Printhouse, South Cumberland Street, Dublin 2