EHG5641 - Excavation - proposed Dalchork substation, Lairg

An archaeological excavation was undertaken by AOC Archaeology in 2020, commissioned by RJ McLeod on behalf of SSE and Balfour Beatty, on four prehistoric roundhouses and a group of clearance cairns situated within the footprint for a new substation site at Dalchork Forest, Lairg, Sutherland. The landscape had been thoroughly affected by ploughing for tree planting and subsequent felling operations. Open-area excavation and subsequent archaeological watching brief was undertaken between during May – September and December 2020 in order to recover archaeological material and information before its loss during development. The excavation methodology followed best practice standards identified in Excavating Prehistoric Roundhouses: Guidance on good practice and effective outcome for future research (Romankiewicz and Mann 2017). Due to the nature of the development, whereby the roundhouse sites would be stripped away during groundworks, full excavation of the roundhouse sites was undertaken. This was required for Sites 1, 2, 3 and 4. Site 5, situated on the periphery of the development was fenced off with a 10m buffer in place. On each roundhouse site, excavation was undertaken by quadrants with cross-section baulks to record stratigraphic relationships. Internal deposits and features were fully excavated by hand. Four slots were excavated through each of the roundhouse wall banks to record wall construction and any identified entrance structures were fully excavated. Recording was undertaken using written records, section and plan drawings and a Trimble DPGS rover. Digital photography recorded all stages of excavation and individual features, to include the use of high-pole photography, drone photography and photogrammetry. Controlled archaeological monitoring of machine stripping of each roundhouse and clearance cairn site was undertaken upon completion of excavation in order to record any further archaeological deposits or features below the roundhouse banks and to the exterior of the sites. Further archaeological monitoring was undertaken during site clearance within a 20m buffer around the roundhouse and cairn group and across further areas of the substation, to include stripping of new roads access and site compounds. Groundworks across low-lying, waterlogged areas were not subject to monitoring. Four very different roundhouses were revealed by the excavation. Site 1 comprised the well-preserved remains of a stone-built house measuring 7m in diameter internally with an entrance to the south. The roundhouse bank measured up to 2.5m wide, faced with orthostats and rubble coursing on the interior and rough boulder facing with some slab coursing on the exterior. It contained a central slab hearth and internal post-ring set approximately 2m from the inner wall face. Site 2 consisted of a mostly turf-built bank with rubble facing stones on the exterior and interior enclosing an internal space measuring 9.2m by 8.2m. A wide (sub-oval) entrance passage on the southwest side of the site contained a slabbed surface representing more than one phase of surfacing. A shallow ditch enclosed the outside of the roundhouse. Within the inner ring and outer ring of post-holes, there was evidence for a considerable period of use represented by re-setting of posts and insertion of new post-holes. Site 3, the smallest roundhouse, measured 5m in diameter internally, with the very degraded remains of an entrance to the south side. The rubble spread of the bank contained internal facing stones and evidence for outer boulder facing. It contained very ephemeral evidence for small internal post settings and a central slabbed hearth. Site 4 measured 12.3m in diameter internally, comprising a rubble bank supported by boulder facing stones on the exterior, while minimal evidence survived for inner face stonework. An alignment of post-holes on the south side of the interior represented a timber entrance passage structure. A single internal post-ring measuring 10m across showed that the posts were set 1-1.5m from the inside of the roundhouse bank. <1>