|Energy||2018||EIRGRID plc||Shannon Estuary, Ireland|
EirGrid is the Transmission System Operator and Market Operator in the wholesale trading system in Ireland. EirGrid plans to install a marine cable across the Shannon Estuary to connect existing substations at Moneypoint Co. Clare and Kilpaddoge Co. Kerry. A marine survey was required to locate a suitable route which would permit burial of the single circuit 400 kV AC cable.
RINA was contracted to provide offshore geophysical, geotechnical and environmental surveys for the project. Our scope comprised:
- Phase I - Geophysical survey: Multi-Beam Echo Sounder, Single-Beam Echo Sounding, Acoustic Ground Discrimination System, Side-Scan Sonar, Magnetometer, Sub-bottom Profiler, processing, interpretation, and reporting. A topographic survey was performed at 4 landfall areas by using UAV. Tomographic seismic refraction determined thickness and characteristics of stratified substratum
in the landfall areas. Total survey area approximately 7.2km2.
- Phase II - Geotechnical survey: 57 No. vibrocores (penetration depth to 6m at all locations except of No. 8 locations of high sediment mobility where penetration depth is increased to 8m) and 25 No. cone penetration tests (maximum penetration depth to 10m) paired with vibrocores at locations along the proposed subsea cables corridors; Onshore geotechnical and geo-environmental laboratory testing, engineering and reporting.
The main outcomes from the surveys were:
- determine composition and geotechnical properties of the superficial deposits;
- identify obstructions, subsea facilities and any previously unrecorded archaeology;
- locate sand waves or areas of sediment mobility;
- provide geo-environmental data to assess contamination risks during construction