2021:715 - King John's Bridge, Lucan, Dublin

Archaeological monitoring took place during remedial works at King John’s Bridge in the townland of Esker South, close to Lucan, between 30 September and 07 October 2021. The bridge, a listed monument (DU017-078) in the care of South Dublin County Council, comprised a small bridge arch between two piers on the River Griffeen, Esker South, Co. Dublin. The arch was once the central arch of three arches and currently spans the narrow river which was once wider. The bridge is dated to the late 12^th/early 13^th century. The site was approximately 100m south-west of Esker church and Graveyard, DU017-02201 and DU017-02202.

The entire structure was approximately 4.8m in length north-east to south-west. It was 2.7m in width on the south-west bank and 3.1m in width on the north-east bank. The arch was about 2.6m in span and 1-2m wide, with two sturdy piers on either bank, 1.7m in length (north-east to south-west) on the south bank and 2.3m in length on the north bank.

The bridge was in danger of collapse due to tree-root activity and was in immediate need of remedial care. It was proposed by South Dublin County Council to clear vegetation, including sycamore roots on the bridge and in the immediate area and to carry out localised repair to stonework where required, including excavation of soil to the west bridge abutment, under archaeological supervision.

Ministerial Consent C1060 for the conservation works was granted by the National Monuments Service in July 2021, with licence E5346 for the archaeological monitoring. As a condition of the licence, it was stated (Condition G) in the letter of Consent (07 July 2021) that wicker centring noted in the Sites and Monuments record in 2016, ‘shall be examined and verified as to survival and condition by the applicant and communicated to the NMS in writing prior to the commencement of any works’. In the RMP record, it is stated that ‘just beyond the intrados of the SE arch, the imprint of a short length of wicker centring can be seen at the north side of the arch’.

An examination of the intrados of the south-east arch took place by the licensee and the conservation architect, David Maher, on 30 September and a report was sent to the NMS on 04/10/2021. No evidence of wicker imprint was noted, including on the north side of the intrados. In this area, however, there was a small section resembling linear imprints in mortar and it was assumed, in the absence of any other feature resembling such an imprint, that this is what is being referred to in Condition G.  This survives today but seems to be a feature of pointing or repair of the bridge with mortar. In any case, this area of the bridge was not to be impacted.

Two areas were dug for root removal - one directly to the west of the west pier of the upstanding arch and another, approximately 4m west from the end of the west pier of the upstanding arch. Soil and vegetation was removed on the south-west facing side of the structure.

Area 1: A particularly large sycamore stump with roots was present on the west side of the bridge. Excavation of this area under archaeological supervision took place. This revealed the south face of the west pier. This proved that the ‘pier’ was not an abutment but a central arch pier which would have supported another arch to the west. Records have already stated this, but this is the first physical proof in the 21^st century as records are very scant for works around the bridge. Works here seem to have taken place in the 1980s as well as in the mid to late 19^th century.

An upper layer of stone above the pier would suggest the spring of the west arch of the three arches. At the base, to the west of the pier, there is a large, flat, seemingly deliberately placed stone, flanked by smaller stones. Above this, and to the west of the pier, the ground was made up of dark brown clay with stone, containing some modern rubbish such as a ‘Farmer Brown’s’ crisps bag and a chocolate bar wrapping, both of the early 1980s, suggesting that ground was filled to the west of the bridge at that point.

Area 2: A shallow trench was dug approx. from the west arch pier. This was 1.5m in length and 0.7m wide. It was dug to a depth of 0.12-0.15m to the top of a stone spread, although this was not investigated any further. It demonstrates that a rubble spread continued at least 4m to the west of the upstanding structure and was probably, at least in part, related to the third arch of the bridge on the south-west bank.

Monitoring of soil and vegetation removal on the river bank on the west side of the bridge took place. This was not extensive but revealed a cutwater, hidden in recent years. This was the cutwater of the west pier of the central arch and would further indicate that the structure had another arch to the west of that presently spanning the river.

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