SDO12240 - Poole Harbour Channel Deepening, Archaeological Diving Inspection of Geophysical Anomalies.

Maritime Archaeology Ltd were contracted to provide an archaeological diver for the inspection of a range of anomalies located in the area to be dredged ahead of the Poole Harbour Channel Deepening project. Geophysical survey of the area to be dredged had been undertaken, processed and analysed by Wessex Archaeology. This survey identified anomalies which were then classified as either ‘high’, ‘medium’ or ‘low’ archaeological potential. Diving operations between the 4-8 July 2005 were undertaken to inspect all anomalies identified as being of ‘medium’ potential and 50% of anomalies identified as being of ‘low’ potential. Methodology for inspection involved the installation of a shot line in the position of the anomaly, this was undertaken by Poole Harbour Commissioners. The dive platform moored adjacent to the shot line and the divers used a circular search pattern to locate the anomalies. A total of twenty three anomalies were inspected, the results were as follows: • 9 anomalies could not be located • 12 anomalies had no archaeological potential • 2 anomalies had low to medium archaeological potential Where the anomalies could not be located a thorough search of the seabed was undertaken. As the geophysical survey was undertaken almost a year prior to the diving searches it is possible that the anomalies could have been covered by seabed deposits, or the anomalies could have been mobile material that has moved around the seabed. As these anomalies could not be located their archaeological potential has been recorded as ‘unconfirmed’. In order to account for the sites where no anomalies were discovered consideration should be given to the following mitigation: • Re-examination of geophysical survey data to compare the signatures gained for sites that have been positively identified by diver ground truthing against those which could not be located. Similarities in geophysical traces could help determine archaeological potential. • Provision of a watching brief on dredging operations. This would mean an archaeologist was on hand to inspect any items of potential archaeological interest. It would be advisable to supply the skipper of the dredger with the positions of sites where there is a chance that items could remain buried. The anomalies with recorded archaeological potential were: • A wreck site (Anomaly: 6171) Inspection demonstrated that this site consisted of a mixture of scattered metal and wooden remains. The identity of this wreck has not been confirmed although the initial assessment suggested it was relatively modern and it is believed to be of low to medium archaeological potential. • Group of materials (Anomaly: 6196) A group of two metal objects and one stone object were discovered within four metres of each other. These items did not appear to be related and appeared to be isolated find spots, however, the stone object may be of some archaeological interest. Recommendations for further work includes a further diving inspection of the wreck site (Anomaly: 6171) over a slack tide window to enable a more comprehensive assessment of its archaeological potential. Consideration should be given to the recovery of the stone object (Anomaly: 6196) prior to dredging works.