Abstract
- Geophysics Ltd. (MGX) carried out a geophysical survey consisting of Seismic Refraction surveying for the Belmullet Wave Energy Connection project at Belderra Strand in County Mayo.
- Eleven pairs of seismic profiles were acquired ~ parallel to the seafront and extended from just above high water mark as far as possible towards the low water mark.
- The survey penetrated to > 15m Below Ground Level (BGL) and shows a three layer earth model below the site.
- The overburden consists of a soft / loose layer of sand and shingle at the back of the beach. This layer has low seismic velocities, is 1.2 – 6.0m thick and could be excavated by digging.
- A second thicker overburden layer also consists mainly of sand and shingle. This layer extends across the site and is 2.0 – 15m thick. It has higher seismic velocities and is more compact but could still be excavated by digging. Some possible thin weathered rock, that may need to be excavated by ripping, may be present at the base of the layer.
- The deepest layer consists of strong rock which has a high seismic velocity of 3.7 – 3.8km/s. This rock could be extracted by breaking / blasting.
- The depth to the top of the strong rock varies between ~ 2.0 – 15.0m BGL. The rock is shallowest in the west and far southeast of the site and deepest in the north.
- A narrow ridge of strong rock approximately 10m wide with a depth range of 2.0 -6.0m is well defined on the seismic datasets along the western fringe of the site. Here the rock shallows towards the outcrop just southwest of the site.
- Any future landfall cables which are installed as part of the Wave Energy Connection project should be positioned where the sand and shingle sequences are thickest in the central or eastern part of the site. This will reduce the amount of breaking / blasting of strong rock required in the excavation phase of the project, or breaking may be avoided completely.
Belmullet Wave Energy Connection Belderra Stran County Mayo Geophysical Survey is located in Ireland.