2025:507 - River Deel (Crossmolina) Flood Relief Scheme: Stage (i)a Test Trenching, Mayo

It was originally proposed to excavate 139 test trenches (T1–139), across ten areas, with a total length of 9963 linear metres. Due to various constraints 127 trenches were excavated by mechanical means, with a total length of 9104m.

Test trenching Area T01 was located at the extreme north-west of the scheme, to the west of the River Deel in Crossmolina townland. The area extends across two fields. Eight test trenches (T1–8) were excavated, totalling 407 linear metres of trenching. Nothing of archaeological interest was identified. All features were interpreted as being agricultural in nature, either furrows or infilled remains of previous field systems. A field boundary in T1 is visible on historic mapping.

No test-trenching was conducted for T02 due to invasive knotweed.

Test Trenching Area T03 is the largest on the scheme, from the L1105 in the west, to the R315 in the east, and located within the townland of Cartrongilbert. Topography is undulating, with a shallow hill in the western half of the area, and several low-lying peat areas close to the low-lying elements of the townland boundary with Mullenmore North. Trenches 42 and 67 recorded the greatest depth of peat, at 3.5m and 1.75m respectively.

There were 79 trenches (T17–T95) planned for T03, with a total length of 6122m. Due to constraints at the eastern on of the Area 75 trenches were excavated, totalling 5697m, with Trenches T91–T94 removed from the layout. Only one area of archaeological interest was identified during test-trenching in T39, a small patch of possible burnt mound material (C325) designated Cartrongilbert 1. Other identified features were interpreted as being agricultural in nature, either furrows or infilled remains of previous field systems.

Test trenching Area T04 was located along the southern side of T03, on the southern—Mullenmore North—side of the townland boundary between Mullenmore North and Cartrongilbert. Topography was more elevated at the western end, falling to the east towards the R315. Trenches 102–103 identified peat depths of up to 2.5m. There were nine test trenches (T96–104) planned, totalling 460 linear metres, including T97 across the townland boundary. Due to overhead power lines Trench 104 could not be excavated. However, T103 was extended to the east and additional trenches were excavated around identified archaeological areas, resulting in a total meterage of 498 linear meters.

Two areas of archaeology were identified in T04 in trenches T96 and T98. Mullenmore North 3a was an area of pits filled with charcoal-rich soil and heat-shattered stone (C407–C413 and C418), while Mullenmore North 3b was the remnants of a burnt mound (C415–C416), likely denuded by agriculture. Other identified features were interpreted as being agricultural in nature, either furrows or land drainage features.

Test trenching Area T05 was located at the east end of the scheme, in one large field. There was a pronounced hill in the west of the field which descended to the east and south. The top of the hill afforded good views of Lough Conn to the ESE and Nephin (Doonebreeda) Mountain to the south. All trenches were excavated, but there was a small deviation in one trench T11A/T110, as a mistaken line was trenched.

Potential archaeological features were found at two locations. These comprised a burnt mound deposit (C505) in T105, a pit and patch of in-situ burning (C509 and C511) in T109 and a large pit (C506) in T113. A piece of a post-medieval pottery was retrieved from the large pit. A series of agricultural furrows were recorded crossing the field on a north-east to south-west orientation.

T06 was a small area at the eastern extent of the scheme, alongside Lake Road. Only one trench (T123) was excavated in this area, 30m long. The only identified features were a field drain and an earthing cable for nearby ESB pole.

Test trenching area T07 was located in the east of the scheme. The field dips towards the middle, rising in height to the south. In total seven trenches were excavated, with a total length of 346 linear meters. A burnt mound (C704) preserved in peat was identified at the northern end of trench T129. An area was stripped around this, to define extents, which flooded immediately. Peat depths in this location are in excess of 4m.

Test-trenching area T08 was a low-lying area of grassland in the south-east of the scheme. In total three trenches were excavated totalling 187 linear meters. Trenches were split in the middle due to the presence of a waterpipe and shortened at the northern end due to overhead wires. A small spread of burnt mound material (C804) was identified at the southern end of T133.

Test trenching Area T09 was located directly to the east of T08, separated by stream U05. This was a low-lying grassland area, adjacent to a pond associated with the River Deel, that rose in height towards the lane in the north-east. Trench layout was constrained by silt fence, overhead wires and an underground water service. In total four trenches were excavated, totalling 129 linear meters. Nothing of archaeological interest was identified.

Test trenching Area T10 was located in the south-east of the scheme and was an area of relatively low-lying grassland, only a small section of which lay within the scheme boundary. Two trenches were positioned to avoid overhead lines and underground water services, totalling 34 linear meters. Nothing of archaeological interest was identified.

Nearly all of the identified archaeological features are signs of likely prehistoric activity, with all sites apart from Mullenmore North 2 containing charcoal-rich soil with heat-shattered stone; burnt mounds or fulacht fiadh remains. A total of five sites contained mounds, spreads or pits that contained heat-shattered stone and charcoal typical of this pyrolithic activity (Mullenmore North 1, Mullenmore North 3a and 3b, Mullenmore North 4, Mullenmore North 5 and Cartrongilbert 1). This activity can date from the Late Neolithic period up to the early medieval period but is predominantly Bronze Age in date. The most substantial of these sites is Mullenmore North 4, where it seems that a large mound and related features have survived preserved in peat. Mullenmore North 2 is small number of pit features. These could date to any time period.