In 2014–15 NAA carried out a desk-based assessment, walkover survey and then monitoring and excavation during renewal of two sections of water pipeline in Swaledale, North Yorkshire, with a total length of 15km. The pipelines connect with service reservoirs at Angram, Gunnerside and Reeth, and the scheme included the construction of pumping stations at Low Whita and Thwaite. The pipeline routes were largely rural, crossing fields bounded by drystone walls, and archaeological recording was carried out on 69 of those walls disturbed by the works. In most areas the new pipeline was laid into an open-cut trench within a c.7m-wide easement stripped of topsoil; however, directional drilling was used to minimise disturbance in several sensitive areas including some of potential archaeological significance.

The area around the works contains a wealth of archaeological remains, including possible Neolithic long-barrows, Bronze Age round-barrows, cairns and possible settlements, and extensive evidence for later Iron Age and Roman settlements and field systems. Several linear earthworks in the area, the Grinton Dykes and Fremington Dykes, are believed to be of Early Medieval origin. Some of the settlements in the area, including Reeth, Grinton and Fremington, were recorded in the Domesday Book and have Old English names. Hamlets and villages further up Swaledale tend to have names of Scandinavian origin such as Thwaite, Muker and Gunnerside. During the medieval period, the dale supported a mixture of moor and riverside pasture, while arable land along the valley sides is indicated by lynchets (earth terraces caused by ploughing) on steeper slopes and areas of ridge and furrow on the more level land.

The majority of archaeological remains identified during the works were agricultural in nature, such as field banks, walls, stone-built culverts and field barns, and were mostly post-medieval in date. Cumulatively, the evidence indicated a long-lived early agricultural landscape characterised by smaller fields with regular boundaries. Frequent sub-surface remains of demolished walls along the pipeline route indicated incremental development and the gradual creation of larger enclosed units. Wall-construction technique and style appeared to have changed little over time since the medieval period. An exception was observed in the area directly west of the village of Healaugh, where walls constructed from natural boulders formed enclosures of irregular sizes and shapes which are believed to represent remnants of more ancient field boundaries.

Along the pipeline route, small numbers of worked flints of Neolithic and Early Bronze Age date were found at several locations. The largest group of this material was in the soil overlying a low stone bank, just north of Thwaite village; however, too little of this structure lay within the stripped corridor and its full form and date could not be determined. 

At Dyke Heads, to the west of Gunnerside, two possible burial mounds were identified inside the construction easement; they were cordoned off and left undisturbed, with the new pipe routed around them. A third possible mound or cairn found nearby during soil stripping was retained in situ, with the pipeline installed in that area by directional drilling.

The pipeline route passed immediately to the south of the Scheduled Monument of How Hill, located on a natural mound on the Swale floodplain near Low Whita. The site has not been excavated but is thought to be of Iron Age or Roman date and comprises concentric earth and stone banks and ditches, possibly enclosing hut platforms. Work on the new pipeline revealed evidence of previously unknown elements of external outworks associated with the entrance, including a curving bank which probably served to manage livestock rather than having a defensive function. The pipeline also passed close to an area south of Scabba Wath Bridge which contains evidence for a settlement platform that is also thought to be Late iron Age or Roman in date; during the work, two levelled banks forming part of its associated field system were recorded.

Just north of Thwaite village, we found a previously unrecorded road or trackway, aligned north-west to south-east and flanked by drainage gullies on both sides. The road/track was c.5.4m wide and surfaced with several layers of limestone rubble laid over an ‘agger’ (a raised embankment) of gravel and sand. More stones lying to the north of the road, interpreted as having tumbled from its upper surface, included part of a Roman-period glass bangle and a fragment of possible samian ware.

The Dales were once an important source of lead, which had been mined since Roman times. Scabba Wath is an ancient ford across the River Swale with a name of Old Norse origin and was probably an important focus for mining activity during early medieval times. Just to the west of the ford we found deposits rich in charcoal and lead slag overlying burnt natural gravel. These were initially interpreted as the probable remains of a bale mound where ore was roasted; however, the slag was subsequently identified as residue from a later blackwork oven. The ovens were often situated adjacent to bales, the improved technology making it possible to extract more lead from the bale slag. Significantly, hazel charcoal extracted from some of the slag gave a calibrated radiocarbon date range of AD1027–1166. Pottery found nearby was of a similar date (11th or 12th century) and suggests that Scabba Wath was an area of activity around the time of the Norman Conquest.

The pipeline renewal works demonstrated the wealth of archaeological evidence of all periods that can be found during developments in the Yorkshire Dales. In this case, a continuing dialogue between the monitoring archaeologists and the contractors meant that adjustments to the pipeline route and construction methodology could be undertaken as new discoveries were made. This meant that it was possible to retain many archaeological features in situ and reduce damage to others. As well as preserving the sites, a significant bonus of this co-operative and flexible approach to the works was a reduction in construction delays and the overall cost of the project.