2001:818 - DERRYCOLUMB 5 BOG, Derrindiff and Derrylough, Longford

This site was excavated as part of the 2001 Bord na Móna Archaeological Mitigation Project. It was recorded in 1999 as 99DBSE0007A-T, a substantial togher composed of oak planks, split timbers, roundwoods, brushwoods and pegs, extending in a east-north-east/west-south-west direction across nineteen fields for a distance of 426m. Four cuttings were excavated during the 2001 Mitigation Project, three 10m by 5m in size and the fourth 15m by 5m, one at each end and two further cuttings along the length of the site.

The first cutting was placed at the westernmost sighting, 99DBSE0007A. It was close to the western margins of the Bórd na Móna (BnM) production bog and as a result the site had been disturbed by drainage works carried out in the bog. The eastern edge of the cutting contained some degraded plank fragments with two possible posts, while the remainder of the cutting was completely devoid of wood.

The second cutting was placed at sighting 99DBSE0007E. The site was visible on the field surface, for a short distance, at both drain edges. The overlying peat was up to 0.53m deep. It was moderately decomposed Sphagnum-rich peat with inclusions of Eriophorum as well as small amounts of ericaceous heather roots and other fibrous matter. The upper walking surface of the trackway was made up of large half-split oak planks. Two planks were exposed within this cutting. The first measured 3.99m in length by 0.66m in width, with an average thickness of 0.18m. It had three D-shaped mortice holes, none of which contained pegs. This plank slightly overlapped the second plank, which was 7.03m long and 0.58m wide, with an average thickness of 0.1m. It had six mortice holes, all of which were somewhat D-shaped, but again none contained pegs. The mortice holes were fairly consistent in size, measuring 0.1m by 0.12m on average, and five were damaged. The upper walking surface was supported by short transverse roundwoods close to the ends of the longitudinal timbers. The transverse roundwoods were in turn supported by longitudinal brushwood and roundwoods which ran underneath and alongside the upper walking surface and were secured in place with long pegs.

The third cutting, placed at sighting 99DBSE0007K, was located close to the drain edge where one of the upper planks was exposed on the field surface as a result of drain-cutting. Little peat cover remained over the site at this location. It was up to 0.1m deep and was Sphagnum-rich, with very frequent patches of Eriophorum and ericaceous heather roots. The excavated cutting contained what appeared to be the northern end of an upper plank. Directly underneath this plank was a roundwood transverse support which appeared to have been stabilised by a large upright post, a half-split roundwood, which had been cut into a rough, wedge-shaped point.

The fourth cutting was recommended in the mitigation strategy to be located as close as possible to the eastern extent of the bog. It was, however, placed at sighting 99DBSE0007Q. While there were three further sightings of the plank track, this location was chosen as it was likely to provide the best-preserved portion of the site. There was up to 0.49m of peat over the site at this location. It was poorly decomposed, Sphagnum-rich and very fibrous in patches, with a large amount of Eriophorum and frequent ericaceous heather roots. This cutting differed greatly from Cutting 2 in the volume of wood present. The site construction was consistent with that in the previous cuttings but there was a lot less substructural wood present. Three planks were exposed in the cutting. The central plank was completely exposed while the other two were partially exposed at the northern and southern edges of the cutting respectively. The central plank was 6.83m long. There were thirteen mortice holes on the three planks, none of which contained pegs. The mortice holes were aligned in pairs except for the single example 1.82m from the southern end of the central plank. When this plank was later removed (see below) the underside was viewed for the first time. There was an incomplete mortice hole directly opposite the single complete hole visible on the flat walking surface of the plank. The transverse roundwoods supporting the ends of the longitudinal timbers were clearly visible in this cutting, while the longitudinal brushwood and roundwoods were more sparsely laid and were a maximum of three deep. There were four large half-split posts placed one on either side of each end of the central plank. These protruded above the level of the surface of the upper planks and were worked along their length like the post from Cutting 3.

From its composition and construction this site appears to be identical to the Bronze Age trackway excavated in 1991 by the IAWU in the adjoining Derrycolumb 4 Bog. This will hopefully be confirmed by dendrochronological dating during completion of the post-excavation work. The variation in the appearance of the site is not unusual in sites of this size and length. Previously excavated plank trackways in County Offaly (OCarroll 2001) and in County Longford (Maloney et al. 1993; Raftery 1997) have shown similar variations.

The central plank from Cutting 4 was removed by machine from the cutting a few weeks after the excavation and was weighed in the BnM offices in Lanesboro’. Although the plank was still slightly waterlogged it had dried out considerably and weighed in at half a ton. This would have required several people to carry it out into the bog. The planks all average 7m in length, and altogether approximately 60 planks alone (roughly 30 tons) would have been required to construct the whole length of the trackway recorded in this bog. The ‘empty’ mortice holes on the planks are thought-provoking but not unusual. There have been many recorded instances of this phenomenon and it is generally agreed that these holes were made in many cases to facilitate the transportation of the planks out into the bog and to allow them to be manoeuvred into place (Raftery 1997; Pryor and Taylor 1992).

References
Maloney, A. et al. 1993 Survey of the raised bogs of Co. Longford. Transactions of the Irish Archaeological Wetland Unit 1. Dublin.
O'Carroll, E. 2001 The archaeology of Lemanaghan — the story of an Irish bog. Bray.
Pryor, F. and Taylor, M. 1992 Flag Fen, Fengate, Peterborough II: further definition, techniques and assessment (1986–1990). In B. Coles (ed.), The wetland revolution in prehistory, 37–46. WARP Occasional Paper 6. Exeter.
Raftery, B. 1997 Trackway excavations in the Mountdillon Bogs, Co. Longford, 1985–1991. Transactions of the Irish Archaeological Wetland Unit 3. Dublin.

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