EHG3771 - Desk-based assessment - Inner Sound, Pentland Firth

The Orkney Research Centre for Archaeology (ORCA) was commissioned by Xodus Group and MeyGen Ltd to assess the potential impacts of the proposed marine renewable energy development in the Inner Sound, Caithness, between the island of Stroma and the mainland parish of Canisbay upon marine historic environment assets. MeyGen proposes to install the project in a series of phases. Phase 1 will comprise an initial Phase 1a deployment 20 turbines (20MW), followed by a subsequent Phase 1b which will deploy a further 66 turbines (66MW). Phase 2 will comprise the build out of the remainder of the project and will be subject to a separate consent application (see Figure 1). Further details on the project scope are in the design document (Meygen, June 2011). As part of this assessment, Scientific Underwater Logistics And Diving (SULA Diving) was commissioned by ORCA to carry out a desk-based assessment (hereafter DBA) of relevant data sources. ORCA reviewed and interpreted remote sensing survey data obtained by IX Survey, Environmental Research Institute (ERI) and Marine Scotland, which included Multi-beam echosounding (MBES), sub-bottom profiling and side scan sonar survey (SSS) interfaced with and without a magnetometer. Further seabed data was available from the benthic survey undertaken by Aquatic Survey and Monitoring Ltd. In total there were 47 MBES anomalies in the survey area. Eighteen were of low potential. Two were of high potential associated with magnetic anomalies. The rest were medium potential. The high potential anomalies (MB01 and MB40) were associated with magnetometer anomalies. In total there were 41 SSS anomalies in the survey area. One was of high potential associated with a magnetic anomaly. Twelve were of low potential. The rest were of medium potential. Five magnetometer clusters were located in the survey area. They were of high potential because of the high probability of cultural material. It was found that there was low potential for submerged landscapes in the area. There was negligible potential for prehistoric cultural remains to survive in the high energy areas and low potential for significant prehistoric cultural material to have survived in areas sheltered from the current (e.g. in gullies and below gravel and sand deposits). There were no shipwrecks or aircraft crash sites with known locations in the development area, and none was identified by the analysis of the geophysical survey data, even though ships are known to have been wrecked in the general area, including at least one vessel of international importance. There was low potential for the survival of wreckage over much of the lease area due to the conditions, and none had been identified definitively by the analysis of the geophysical survey data, although 73 anomalies with medium to high potential of being cultural remains (e.g. wreckage, fishing material, anchors, or cargo lost overboard) were identified across the whole of the survey area. It was assessed that only 34 geophysical anomalies may be significantly impacted, directly and/or indirectly. If they cannot be avoided, it was recommended that these are further investigated by diver or ROV to identify them in order to evaluate their cultural heritage significance and, if necessary, devise appropriate mitigation strategies. The implementation of the recommended mitigation strategies (such as avoidance, scour monitoring, reporting protocol for accidental discoveries, and - if necessary - wreck survey, salvage, or intrusive archaeological evaluation) will result in the development having a minor or negligible residual impact on marine cultural heritage. <1> The information was used to inform the overall Environmental Statement. <2>