Seagreen Onshore Cable Route, Angus

A 19km cable route was to be installed as part of the onshore transmission for two offshore wind farms being constructed in the Firth of Forth by Seagreen Wind Energy. As part of the pre-commencement works, an overarching Written Scheme of Investigation had been commissioned and agreed by the developer. This outlined the required works in general terms, but when the Principal Contractor Nexans were appointed, they realised that there was a significant potential for delays to their programme because of the intended archaeological works. Whilst a watching brief on the entire route might be low impact in terms of the size of archaeological team required, the risk of finding unexpected archaeology late in the day which needed full excavation before the cable works could proceed was unattractive. They knew the archaeology needed to be dealt with correctly, but they needed a more flexible and pragmatic approach which would fit with their timescales.

A team from Headland Archaeology made up of specialists from both the Consultancy and Contracting departments worked closely with Nexans to treat archaeology as ‘risk’ and map the level of that risk across the route. Historic Environment Record data was obtained from the local authority and detailed discussions held with the local archaeological advisor to understand their key concerns and where alternative mitigation approaches might be possible. By focussing client communication on practical and logistical matters at site manager level, it was possible to get a true understanding of the client’s required programme and where the non-negotiable pinch points lay.

The result was a detailed risk register accompanied by field-by-field mapping with specific mitigation strategies for each field, including how several stages of mitigation might be undertaken without delays through lengthy liaison with the archaeological advisor. A system of sign off within 72 hours was devised for any areas where archaeology was clearly not present, which allowed construction on a fast-moving cable construction project to move ahead.