Pat Rabbitte (Dublin South West, Labour)

I am grateful to the Senator for his contribution to this debate.

I am advised by the independent expert consultants engaged by my Department to monitor compliance with the conditions of the Corrib consents under the gas and petroleum Acts that pipelines are normally designed taking account of the largest loads they are likely to experience during their lifetime, including transport, loading, installation and operation. Operational loads include those due to the pressure and flow of the fluid they contain and externally imposed loads from the environment, both normal and accidental, such as earthquake loading. The normal practice is to design the pipeline to withstand the largest of these loads taking account of the likelihood of extreme events.

I am further advised that, in the case of the Corrib pipeline, the original design pressure of 345 bar and the forces imposed during the laying of the offshore section will have determined the strength and, therefore, material and wall thickness of the pipe. In the North Sea and north Atlantic regions these loads dominate over the environmental or accidental loadings and provide a margin of safety for loadings due to earthquakes experienced in the region. The risk of earthquakes of magnitude five or more is assessed by the British Geological Survey as less than very low, the lowest risk assigned to any area. I am advised that earthquakes of magnitude less than five in these low-risk areas will not give rise to forces on the pipeline greater than its design allows for. The Corrib pipeline design documentation states that as the area is categorised as less than very low for earthquake risk, in accordance with the relevant codes, the pipeline design incorporates no specific provision for seismic activity. The design documents also considered seismic events leading to a release from the subsea equipment and onshore in the qualitative risk assessment. However, based on the code criteria, these were screened out as being a non-credible cause for loss of containment. It should also be noted that the British Geological Survey reference on which this is based only addresses events of magnitude five and higher. The magnitude 4.0 earthquake that occurred 60 km off the north Mayo coast on 6 June was located in a geological fault system that drops the Slyne-Rockall basins down to the west of the Irish shelf. These naturally occurring faults, formed millions of years ago, have had a long geological history and are related to the continuing opening of the Atlantic Ocean. While the location and magnitude of this event were, as the Senator noted, unexpected, there is a clear geological reason for it. I am advised that future seismic activity along the fault system may be anticipated but not of significantly larger magnitude.

The magnitude was far below the threshold for generation of a seismogenic tsunami or to cause significant structural damage. Shell E & P Ireland Limited has informed my Department that the Corrib wells and manifold were inspected by a subsea support vessel after the earthquake and that it has confirmed there has been no impact on the facilities. A report will follow to confirm this, which will be reviewed by my Department in liaison with its independent consultants. Shell also has advised that the observations of the pipeline system confirm that there is no issue with the integrity of the pipeline. The Corrib pipeline is scheduled to be inspected this summer and survey reports will follow. These reports also will be considered by my Department and reviewed by the consultants. Before the Corrib gas project can commence production of gas, it will be the subject of a safety assessment in accordance with the Commission for Energy Regulation's recently published petroleum safety framework.