This Stage (iv) Excavation Report details the results of the archaeological excavation at Claggarnagh West 3 (ITM 508030, 786314) in advance of the construction of the proposed N5 Westport to Turlough Road Project, which extends between the townlands of Westport Demesne and Liscromwell in County Mayo. The site was identified during Stage (i) archaeological test excavations of the proposed N5 Westport to Turlough Road Project (A0069: E004621) undertaken by Archaeological Consultancy Services Unit between 10 August and 21 October 2015. The excavation was carried out by Joe Nunan between 16 and 26 September 2016 under Ministerial Direction Number A0069 and Registration Number E004698 issued by the Department of Arts, Heritage, Regional, Rural and Gaeltacht Affairs, in consultation with the National Museum of Ireland. An area measuring 400 mý was stripped of topsoil and excavated at Claggarnagh West 3. This confirmed the remains of a disturbed burnt mound (F03) that was roughly kidney-shaped in plan. It measured 8.45 m in length (E/W) by 4.40 m in width (N/S) and survived to a thickness of 0.35 m but averaged 0.10 m. Upon removal of the burnt mound, a sub-oval-shaped wood-lined trough (F06) measuring 2.20 m (E/W) by 1.35 m (N/S) and up to 0.10 m in depth was exposed. It contained seven decayed timbers (F08) laid horizontally, north-east to south-west, on its base. The horizontal timbers appear to have been associated with four small stones placed on the base of the trough in order to support or level the timbers above. A second trough (F09) was also exposed c. 3 m to the south. It was sub-circular in plan and measured 1.85 m (E/W) by 1.48 m (N/S) by 0.13 m in depth. A stone-lined hollow (F14) abutted the northern side of trough F09 and appeared to operate as a water holding area for overspill from the trough. This water then flowed into a channel (F13) that extended downslope to the north-west and into trough F06. A sample of hazel charcoal (0.2 g) from the fill (F10) of trough F09 returned an Early Bronze Age date of 2204?1979 cal. BC (3710 ñ 35 BP; Poz-99264), while a sample of ash wood (44 g) from the wood lining (F08: Timber 4) of trough F06, returned a Late Bronze Age date of 1215?987 cal. BC (2900 ñ 35 BP; Poz-97439). Given the length of time between these two dates and the stratigraphic relationship between the two troughs via the water management system, it seems likely that the early date represents residual charcoal or old wood that was preserved in the surrounding peat and used for fuel during the Late Bronze Age use of the site for pyrolithic water-boiling activities. A further six fulachta fiadh were also excavated in the same townland as Claggarnagh West 3. Claggarnagh West 1 (E004696) was 50 m to the south-east, Claggarnagh West 2 (E004697) 30 m to the south and Claggarnagh West 4 (E004699) 40 m to the north, while further afield was Claggarnagh West 5 (E004700) and Claggarnagh West 6 (E004701), 160 m and 450 m to the north-east respectively and Claggarnagh West 7 (E005015), 218 m to the NNE. All comprised burnt mounds with various troughs, pits and other associated features also uncovered, and where dated these sites were in use from the Chalcolithic to the Late Bronze Age.