RWE Renewables is currently developing the 1600MW Offshore Wind Farm (OWF) Södra Midsjöbanken located in the southern Baltic Sea. N-Sea, along with their partner Ocean Ecology, were contracted for late season provision of vessel, equipment, and personnel to perform a geophysical site survey and environmental baseline survey, as well as full data processing, sample analysis, interpretation, and reporting.

The main purpose of the scope of work was to determine the benthic composition of the area. The geophysical survey consisted of: vessel mounted MBES (Bathymetric) Survey and towed Side Scan Sonar with piggy-backed Magnetometer to discover archaeological artefacts, boulders, debris, and other natural / non-natural objects. The environmental survey included investigation of occurring habitat types and benthos. Benthic environments were investigated through grab sampling and drop-down imaging/video capture at each sampling location.

Offshore Wind Farm (OWF) Södra Midsjöbanken, source: N-Sea

A rapid turnaround of vessel mobilisation and execution was required during the pandemic; leveraging the full spectrum of supply chain relationships and personnel resources to ensure correct manning and equipment. HSE and environmental sensitivity were of the highest priority to comply with licensing conditions and mitigate marine mammal disturbance. Operational efficiencies were identified and initiated to minimise schedule duration. Shoreside processing was combined with regular data transfer to enable advanced analysis of data to plan the environmental work scope and real-time QA/QC of acquired data to ensure full coverage and quality. Constant review and communication with the client ensured targets were met with minimal overlap.

“We would like to thank all partners involved in this case study. A solid performance by the vessel, onboard team and collaboration with our partners ensured completion of the offshore scope within the required timelines and delivery to our client’s satisfaction. Excellent SHEQ performance throughout the project, despite logistical challenges and icy conditions. An efficient and transparent data processing and reporting flow contributed to a controlled and efficient approach to acquisition and project success.” said Paul van Waalwijk van Doorn (Managing Director Survey).

N-Sea is an integrated subsea solution provider in Survey, UXO, Power Cables, IRM and Light Subsea Construction. We deliver effective and cost-efficient solutions for subsea infrastructures and assets that meet the needs of the international oil, gas- and renewable industry. Delivering subsea: from inspections and pre-installation surveys through to construction support and maintenance management to decommissioning, working in challenging conditions without compromising on safety.

Source: N-Sea