Scour Monitoring for Jackup Operations, Teesside Offshore Wind Farm (EDF)
Geotechnical investigations form a central element of site investigations for offshore developments, including offshore windfarms. Jack-up barges, which stand on legs penetrating the seabed to conduct operations, are commonly used at shallow (< 40 m) sites. However, in these shallow zones where the seabed is predominantly sandy, the legs are at risk from scour due to either current action or waves, or a combination of both. At the Teesside Offshore Windfarm scour was identified as a risk and Partrac were commissioned to provide a system for monitoring scour in real-time. We deployed a scanning sonar system, strapped to one of the legs and connected via a cable to power and a surface computer, to monitor the evolution of scour in real-time and in high resolution beneath the rig and around multiple legs. The system provided a useful tool for monitoring scour, and the influence of short term, but energetic squalls could be seen in the data.
Pipeline Free Span Vulnerability Assessment (ENI)
Free-spanning can develop in both cables and pipelines where the surrounding sediment matrix has been removed by scour processes. Where this becomes excessive then the free-span can exceed the design parameters, and the situation can become critical. ENI (UK) contacted Partrac when a buried fuel pipeline, which brings gas ashore at Point of Ayr on the northeast Wales coastline, developed an excessive free-span due to scouring. Partrac were charged with conducting a high level study to assess how the situation had developed, what type of immediate mitigation may de-risk the situation and whether the situation was likely to get worse in the foreseeable future. We collated site specific oceanographic, geological, geotechnical and bathymetric datasets, and undertook analysis of some collected sediment samples, to inform these areas. This project is ongoing and we continue to develop our analysis and advise the Client on the collection of new datasets which would be of use.