EHG6283 - Desk-based assessment - proposed Scottish Isles Fibre Optic Project, Eigg-Arisaig

A desk-based assessment was undertaken by ORCA in 2021 to assess potential impacts on the onshore and marine historic environment by the proposed installation of four inter-island fibre optic cables and their associated landfalls within the Inner Hebrides geographical area. The DBA was conducted to identify possible heritage assets within the marine and BMH buffer study areas. Only the Eigg-mainland (Arisaig) cable was within the Highland Council boundary. The study aimed to identify any sites of archaeological or historical importance that might be affected by the landfalls and marine corridors and identify strategies for mitigating and managing any identified issues and impacts concerning the archaeological and heritage resource. The resulting report was intended to support the Environmental Appraisal (MEA) submitted for the Marine Licence Application and planning permission. The marine study area comprised the 500m wide cable corridors that were subject to marine geophysical survey. The desk-based marine study corridor was at least 1km wide in order to capture wrecks that have no precisely known location but could be in the 500m corridor. The onshore study area comprised the onshore landfall corridor between MLWS and the BMH location with a 500m radius onshore study buffer area round the BMH to capture any potential issues in the immediate vicinity that could affect the installation. Originally, the onshore buffer study area was designed to be a simple 500m radius around each BMH location. However, during the project, BMH locations were changed as part of the iterative design process. A decision was made to not revise the search areas and repeat searches after the fourth change of BMH location, except for any large changes of more than 100m. As well as the marine corridor DBAs, SULA Diving were also commissioned to evaluate the marine remote sensing survey data (Multi-Beam Echo Sounder (MBES), Side Scan Sonar (SSS), and Magnetometer (Mag)) obtained by survey company Fugro during 2021 on behalf of GMG and BT. The marine geophysical survey corridors were 500m wide. The marine archaeologist reviewed the contacts and anomalies identified by Fugro as anthropogenic or giving high magnetic responses, along with high quality images of the data to check anything that looked potentially anthropogenic. <1> See EHG6284 for the onshore walkover survey element of this project.