SDO12549 - Grimstone Reservoir, Dorchester, Dorset. An Archaeological Field Evaluation

Context One Archaeological Services Ltd (COAS) carried out an Archaeological Field Evaluation at Grimstone reservoir, Dorchester, Dorset, (centred on NGR SY 64594 95307) over 8 days between 15th June and 12th July 2011. The investigation was commissioned and funded by Wessex Water Services Ltd. The evaluation was requested by Wessex Water Services Ltd on the advice of Mr Steve Wallis (Senior Archaeologist, Dorset County Council) in order to determine the most appropriate location for an extension of Grimstone reservoir. The archaeological work confirmed that anomalies identified by geophysical survey on three sides of the reservoir reflected the underlying archaeology. The orientation of the anomalies strongly suggests that the scheduled field system north of the reservoir was merely part of a larger system which included fields identified from air photographs to its south. The current evaluation and one by Wessex Archaeology in 2008 strongly support English Heritage’s interpretation that the system dates to the Iron Age. More specifically, the finds suggest that it was in active use from at least the 5th century BC until the 1st century BC/AD.The evaluation by COAS has retrieved fragments from vessels dated to the earlier part of this range which would be of significant value to Iron Age research in the region as they are from a period which remains poorly understood. Ideally carbon dating should be applied if suitable material is found in soil samples retained from the evaluation. In any event the pottery ought to be made available to researchers through publication in a journal. A small group of flints found with the pottery appears to have been worked at around this date. This represents a very late use of flint which, although not unexpected, is usually difficult to demonstrate because it is mixed with earlier material. Photographs of five large half discs of chalk have been sent to stone specialists. Combined with the geophysical survey the evaluation has shown that in whichever direction the reservoir is extended important archaeology will be encountered and that mitigation strategies will need to be employed.