Abstract
This report presents results of monitoring of marine mammals during construction of Robin Rigg offshore wind farm in the Solway Firth. Sixty-two monopile foundations were installed by hammer piling between December 2007 and February 2009.
The programme of marine mammal monitoring commenced with baseline surveys in February 2004 running through to January 2005, supplemented by further pre-construction surveys in July 2007. These were vessel based surveys during which marine mammal observers acquired effort-related sightings data as the survey craft followed set transects within the Solway Firth.
Vessel based monitoring continued during the first 12 months of the construction period and was supplemented in December 2007/January 2008 by land-based monitoring in the upper Solway. In addition, a programme of mitigation involving marine mammal observers, soft start piling and deployment of acoustic harassment devices was operated from the foundation installation vessels.
Surveys immediately before construction supported previous work undertaken for the project Environmental Impact assessment, and earlier baseline surveys, in that harbour porpoise and grey seal were identified as the most commonly encountered marine mammal species in the Solway Firth. Marine mammal sightings in and around the wind farm area itself were relatively rare.
Surveys in the wider Solway Firth showed that harbour porpoise continued to be present within the estuary, and exhibited apparently normal behaviour, over the period of piling activity. There was no evidence of standings and piling was never delayed by presence of cetaceans in close proximity to works.
During the initial period of piling measurements of underwater noise were made which suggested that the likely zone of physical harm for marine mammals was much smaller than expected (approximately 40m, compared to the precautionary 500m monitored zone around piling).
In conclusion, marine mammals are extremely unlikely to have been harmed by the wind farm construction works and any wider disturbance does not appear to have had gross effects, such as displacement from the estuary.