EHG5048 - Desk-based assessment - Dounreay Offshore Wind Farm

A desk-based assessment was undertaken by ORCA Marine in 2015 to assess the potential marine historic environment impacts of a proposed three turbine offshore windfarm with an installed capacity of between 15 to 30 MW, approximately 9km off the coat of Dounreay by Hexicon AB. This is part of a floating demonstrator project called Dounreay Tri. It was intended that the technical baseline assessment would identify any marine sites of archaeological or historical significance that might be affected by the proposed development. Eleven potential shipwreck sites were recorded by the desk-based assessment that potentially could be within the Hexicon – Dounreay Demonstration Site and Cable Route Search Area. The listed positions of all of the shipwreck sites are tentative, being derived from an unverified location of loss, but they have been included in this report as the descriptions of their loss indicate they could fall within these areas. One shipwreck (HMT Orsino) would be considered of high importance as it is a war grave (lost during World War I). The others are recorded as being in or close to Sandside Bay and Dounreay, at the south end of the Cable Route Search Area. Eight of these are of low importance, and two of negligible importance. Two Multi-Beam EchoSounder (MBES) anomalies were noted during the assessment of the geophysical data collected by Marine Scotland for the Hexicon – Dounreay Demonstration Site and Cable Route Search Area - one probably natural, the other potentially anthropogenic. In addition, two Non-Sub Contacts were located outside the Hexicon – Dounreay Demonstration Site and Cable Route Search Area. The MBES survey did not cover the north-east corner of the Demonstration Site, the east side of the and Cable Route Search Area or the southernmost 2km of the and Cable Route Search Area, including Sandside Bay. While it is possible that evidence of periglacial occupation (in the form of submerged prehistoric artefacts and paleo-landscape remains) survives on the seabed, there is considered low potential for preservation of such remains due to the flat, exposed nature of the seabed in the Hexicon – Dounreay Demonstration Site and the northern part of the Cable Route Search Area in waters deeper than 50m. However, in the Cable Corridor Search Area in waters shallower than 50m there is moderate potential for preservation of submerged prehistoric artefacts and palaeo-landscape remains. This will be especially true closer to the shore in Sandside Bay. There is a moderately high probability that there will be evidence of submerged landscapes, submerged peat and postglacial tsunami deposits beneath the sands in the bay, the intertidal zone and possibly the dunes. This is all potential evidence of the historic environment and for human activity in the area. The seabed morphology and tidal regime will also affect the preservation of wrecks and their associated artefacts, thus there is low potential for the project to impact on significant unknown, unrecorded wreck remains that may not be visible in the geophysical data. <1> The assessment was used to inform a full Environmental Statement as was inlcluded within the report as Appendix 16.1. <2> The onshore section of the proposed project was also surveyed (see EHG4795).