Frequently Asked Questions - Safety
How safe is an underground gas storage facility?
Safety is paramount and at Canatxx it is our number one priority. We will use engineering standards and management systems which are of the highest standard. The Canatxx Preesall gas storage facility has the additional safety benefit of working at the same pressure range as the NTS pipeline, so it inherits all the proven safety standards of the NTS.
The project will meet all safety regulations from initial construction through to decommissioning and all the caverns will be constructed and tested in line with these regulations. The Health and Safety Executive (HSE) are the statutory body who ensure compliance and Canatxx will continue to work in conjunction with the HSE.
Will the salt caverns collapse?
No. Salt caverns are sophisticated structural systems, carefully engineered, designed and approved by the HSE. No modern, purpose built, gas storage salt cavern has collapsed.
But what about the old caverns which have collapsed?
Salt mining activities at Preesall that occurred prior to the 1950s did create a number of sink holes. The activities that created the sink holes are well understood, well documented and have no effect on the new gas storage caverns.
In the 1960s ICI developed at Preesall one of the first modern salt solution caverns in the world using gas padding to preserve the salt roof, an effect first observed in the 1890s. This is done by injecting sufficient gas into the cavern to maintain a gas ceiling during the washing so the roof salt does not dissolve. This ensures cavern integrity and stability and prevents surface subsidence. Thereafter ICI washed many subsequent caverns at Preesall using this technique.
Canatxx has made sonar surveys of fourteen of these relatively modern caverns and they are in stable condition today, over forty years after their creation.
Salt caverns are sophisticated structural systems, carefully engineered, designed and approved by the HSE. No modern, purpose built, gas storage salt cavern has collapsed.
What safety regulations cover Underground Gas Storage facilities?
Stringent safety standards are applied to underground gas storage caverns and these facilities are treated as major hazard installations.
Any project, in any industry, wishing to store above certain thresholds of particular hazardous substances, must obtain hazardous substance consent from the relevant Hazardous Substances Authority.13 The HSE is a statutory consultee in this process.
Safety issues during construction and operation of the site are dealt with under the Control of Major Accident Hazards Regulations 1999 (COMAH) and under the Borehole Sites and Operations Regulations 1995 (BSO). Oil and gas field storage pipelines running to and from gas storage sites are regulated by the Pipelines Safety Regulations 1996.14
The HSE will assess the safety implications of each proposal on a case by case basis and will consider any risks to people living and working in the vicinity as well as any implications for future surrounding land use. The HSE will advise both the Department for Business, Enterprise and Regulatory Reform (BERR) and local Planning Authorities whether, on the basis of safety, a particular proposed gas storage facility should be given consent.
Underground gas storage in salt caverns is covered by a British (and European) Standard. The Standard states that salt caverns are seen as suitable and preferential sites for the storage of oil and gas. 15
Can storage facilities be sited near populated areas?
Subsurface storage of gas, whether in salt caverns or depleted hydrocarbon reservoirs, occurs hundreds, even thousands, of metres below the ground surface. In the case of depleted reservoirs, they have naturally contained either gas or oil for many millions of years and more recently have co-existed with human activities, with populations living above them. There are examples both in the UK and in Europe where towns and cities have developed over oil and gas fields.For new storage facilities, the HSE assesses the risks, taking into account the quantities of gas to be stored, the installation type and specification and the local population. It provides advice to the relevant Hazardous Substance Authority which takes the final decision whether to grant hazardous substance consent. Safety considerations are always central to this process. 15
Can stored gas be explosive?
Explosions cannot occur in underground storage as positive pressure is maintained, preventing the ingress of air. It would need oxygen added to the gas to be explosive and this simply not the case here.16
Can gas migrate and escape from underground storage?
The BSO (Borehole Sites and Operations Regulations 1995) enforced by the HSE, require the operator to assess the risks and show there is no unacceptable risk due to gas migration from depleted hydrocarbon reservoirs used for gas storage. 17
What is the safety record of gas storage facilities in the UK?
The safety record in the UK for gas salt cavern storage and depleted field storage is extremely good. There have been no incidents involving members of the public. 18
What emergency arrangements cover such sites?
Emergency planning is at the heart of the civil protection duty on the emergency services and local authorities under the Civil Contingencies Act 2004. The Act requires these organisations maintain plans for preventing emergencies; reducing, controlling or mitigating the effects of emergencies; and taking other action in the event of emergencies.
Under the COMAH Regulations, operators of salt cavern storage facilities are required to develop an on-site emergency plan of how they will respond to an incident and seek to minimise the consequences. The local authority for the area is also required to have in place an off-site emergency plan which all of the emergency services work to in dealing with the wider consequences of an incident.
Most gas storage facilities will include pipelines for transporting the gas between the distribution grid and the gas storage area itself. Under the Pipelines Safety Regulations 1996 (PSR) the operator of the gas transport pipeline must have emergency procedures in place for dealing with the consequences of a major accident. Local authorities are required by PSR to prepare an emergency plan for each major hazard pipeline passing through their area. 19
What is the risk associated with salt cavern underground gas storage facilities?
The HSE state that “over 90 years of expertise has now been gained in the technology of Underground Gas Storage (UGS), with around 630 UGS facilities (of different types) currently operational worldwide and there is perhaps a need to put the risks of UGS and Underground Fuel Storage (UFS) into perspective. This is in terms of both actual events and storage types, and relative to other areas of the energy supply chain.” 20
Today the technique of the design and solution mining of salt cavities for the purpose of high-pressure gas storage is now well advanced. 21
Present day design and construction of gas storage caverns includes significant engineering and project management, covering geo-mechanical design work and implementation. Similar to a large building construction, the process of engineering is complex and interlinked with many disciplines and is planned from start to finish. This ensures the long-term safety and stability of the cavern and associated below ground infrastructure. 22
A full Risk Assessment of the project will be conducted with the HSE prior to construction. The HSE will continue to maintain their role as the ultimate safety authority through to decommissioning.
13 - under the Planning (Hazardous Substances) Act 1990 and Planning (Hazardous Substances) Regulations 1992
14 - DBRR “Gas Storage in your Area - Your Questions Answered” July 2007
http://www.berr.gov.uk/files/file40536.pdf
15 - DBRR “Gas Storage in your Area - Your Questions Answered” July 2007
http://www.berr.gov.uk/files/file40536.pdf
16 - DBRR “Gas Storage in your Area - Your Questions Answered” July 2007
http://www.berr.gov.uk/files/file40536.pdf
17 -DBRR “Gas Storage in your Area - Your Questions Answered” July 2007
http://www.berr.gov.uk/files/file40536.pdf
18 - DBRR “Gas Storage in your Area - Your Questions Answered” July 2007
http://www.berr.gov.uk/files/file40536.pdf
19 - DBRR “Gas Storage in your Area - Your Questions Answered” July 2007
http://www.berr.gov.uk/files/file40536.pdf
20 - Health and Safety Executive, “An appraisal of underground gas storage technologies and incidents, for the development of risk assessment methodology”. Prepared by the British Geological Survey for the Health and Safety Executive 2008 P. XV
21 - Health and Safety Executive, “An appraisal of underground gas storage technologies and incidents, for the development of risk assessment methodology”. Prepared by the British Geological Survey for the Health and Safety Executive 2008 P. 19
22 - Health and Safety Executive, “An appraisal of underground gas storage technologies and incidents, for the development of risk assessment methodology”. Prepared by the British Geological Survey for the Health and Safety Executive 2008 P. 21-22