EDO8074 - Christchurch Solar Farm; geophysical survey 2023

OASIS: Project Methodology: The survey was undertaken using four Bartington Grad601 sensors mounted at 1m intervals (1m traverse interval) onto a rigid frame. The system was programmed to take readings at a frequency of 10Hz (allowing for a 10-15cm sample interval) on roaming traverses (swaths) 4m apart (Illus 8). These readings were stored on an external weatherproof laptop and later downloaded for processing and interpretation. The system was linked to a Trimble R12 Real Time Kinetic (RTK) differential Global Positioning System (dGPS) outputting in NMEA mode to ensure a high positional accuracy for each data point. MLGrad601 and MultiGrad601 (Geomar Software Inc.) software was used to collect and export the data. Terrasurveyor V3.0.37.0 (DWConsulting) software was used to process and present the data. Project Results: Headland Archaeology (UK) Ltd was commissioned by Aardvark EM Limited (the Client), to undertake a geophysical survey on approximately 59 hectares of land north-east of Christchurch, Dorset to inform a planning application for a proposed solar photovoltaic array and associated infrastructure at the site. The results of the survey may also inform future archaeological strategy, if required. The survey has identified a range of anomalies consistent with modern activity and agricultural usage of the proposed development area (PDA) but also of archaeological, uncertain, and possible archaeological origin. These anomalies are identified against a variable magnetic background reflecting changes in underlying sandstone bedrock formations and localised variations in the overlying sand and gravel river terrace superficial deposits. A round barrow and medieval drove track previously recorded in the Dorset Historic Environment Record (DHER) are identified in the northern half of the PDA. A second ring ditch and two right-angled ditch-like anomalies, possibly identifying partial enclosures are also recorded, towards the south-west corner and centre of the PDA respectively. It remains difficult to differentiate many of the linear anomalies in the survey data from across the PDA, though at least eight can be attributed to former boundaries recorded on historic mapping. The nature of many of the remaining anomalies suggest an agricultural cause, such as other unrecorded boundaries, relict field systems and/or stronger cultivation effects. Linear anomalies with a unique magnetic signature and/or alignment are interpreted as of uncertain or possible archaeological origin. Elsewhere, the survey records a faint pattern of ridge and furrow to the east, two services, a possible lightning strike and linear trends deriving from modern cultivation methods. Based on the survey data the archaeological potential of PDA is assessed as moderate to locally high where archaeological remains have been identified and moderate to low across most of the PDA.