How safe are underground natural gas salt caverns?
Historically, storing hydrocarbons in salt caverns and underground formations has been the safest and most secure method of storage. One of the most significant factors contributing to the safety of cavern storage in Canada is the mandatory requirement by all Canadian jurisdictions that design and operation of cavern storage facilities conform to the requirements of CSA Standard Z341, Storage of Hydrocarbons in Underground Formations. Alton Natural Gas Storage will meet or exceed the requirements of CSA Z341 and all Nova Scotia regulations. There are salt caverns in Alberta and Saskatchewan that have been operating safely and date back almost 60 years.
Some people say that storage caverns like Alton have a failure rate of 65 per cent. Can you explain?
To our knowledge, this statistic comes from a paper produced in 2015 in opposition to a rail-loading and liquid petroleum storage project in New York State. That project is not relevant to the Alton project. For example, at Alton, natural gas will be stored in salt caverns deep underground, not liquid petroleum.
Also, the organization that put forward the New York State project refuted the statistic in regulatory filings, noting that the paper’s author was not qualified, used faulty methodology and had inadequate sources.
Purpose-built storage facilities like Alton are designed to be safe and are continually scrutinized and sanctioned by various regulatory bodies and requirements such as CSA Standard Z341, Storage of Hydrocarbons in Underground Formations. As well, Alton has incorporated high-quality engineering safety in design, industry best practices, additional safety controls and back up features to ensure industry leading levels of safety performance.
Further information can be found about Alton safety and geology in the recent project submission to the Nova Scotia Utility and Review Board. See sections 2.3 to 2.5 in that submission.
Does Alton have an Emergency Response Plan?
Protecting public safety and the environment are core values of Alton Natural Gas Storage. Yes, an Emergency Response Plan (ERP) is presently in place for use in the event of an unplanned event on the Alton Project during construction. A second plan has been developed to address brining operations and the third plan will be in place prior to hydrocarbon storage. Each ERP is intended to provide guidance and direction for responding to unplanned events during a particular stage of the Project. This helps ensure, as the project activities change, that the ERP is appropriate for the current activities. ERP exercises are conducted routinely to evaluate the plan with respect to operator training. All personnel will be properly trained on the ERP.
The Alton Natural Gas Storage facility is being designed with redundant safety controls to prevent natural gas leaks. The inlets and outlets to the facility will have Emergency Shutdown (ESD) valves which will close upon any unsafe condition within the plant. The above-ground storage facilities will be protected by fire detection, gas monitors, isolation systems, emergency shut-down devices, and fire extinguishers.
Will there be training and communication for the Emergency Response Plan (ERP)?
The purpose of an ERP is to ensure Alton personnel have the proper procedures and training to manage emergency situations should they arise.
The ERP will identify residents who could potentially be impacted by an unplanned event at the Alton facilities. During brining operations and construction activities, there is no situation that could result in a need for a response by residents. The brining operation will be ongoing for 24 to 36 months during which time brine and water are being transported to and from the river location. No hydrocarbons will be present at either site during this time.
Once the caverns have been constructed, an ERP will be put in place that will address the risks and potential impacts for hydrocarbon storage operations. Based on the identified events and the potential impact areas, residents located within these areas will receive relevant communications pertaining to Emergency Response Planning.
What is your plan in case there is an incident at the cavern facility?
Protecting public safety and the environment are core values of Alton Natural Gas Storage. Currently, no natural gas is present at the Alton Project site. Prior to mechanical completion of the natural gas storage facilities, an Emergency Response Plan (ERP) will be written in accordance with Canadian Standards Association (CSA) Z731 guidelines. These guidelines address the specific response procedures and actions for emergency situations including natural perils, third party emergencies, and brine or hydrocarbon release.
The ERP will be tested and updated annually and will include a program to demonstrate operator familiarity with the emergency response plan.
The Alton Natural Gas Storage facility will be designed with safety controls to prevent natural gas leaks. The inlets and outlets to the facility will have Emergency Shutdown (ESD) valves which will close upon any unsafe condition within the plant. The above-ground storage facilities will be protected by fire detection, gas monitors, isolation systems, emergency shut-down devices and fire extinguishers.
All Alton personnel will be trained on their roles and responsibilities in the event of an emergency. The ERP will be tested and updated annually through drills.
Details of the emergency response plans are not made public for security reasons.
How will the facility and wells be designed to prevent an explosion?
The Alton Natural Gas Storage facility at the cavern site will be designed with safety controls to prevent natural gas leaks. The inlets and outlets to the facility will have Emergency Shutdown controls and fail safe isolation valves (ESD) which will close upon any unsafe condition within the plant. The above-ground buildings and storage facilities will be constructed of metal and non-combustible material and protected by fire detection monitors, gas monitors, isolation systems, emergency shut-down devices, and fire extinguishers.
All operations personnel will be trained in proper operations of the facility and tested to ensure they possess the knowledge and skills to safely operate the facility, with detailed operating procedures in place for every aspect of operation. The gas operating equipment located at the cavern site, such as pumps and compressors, are situated so as to minimize the risk of fire. Caverns are logged to verify the size and dimensions by using 3D cameras prior to commissioning. This test is conducted every five years for the life of the cavern. All equipment will be subject to ongoing corrosion control, inspection and testing. Emergency shutdown valves (ESD) will be installed on hydrocarbon and brine lines on each well. The valves are capable of automatic activation during an upset condition as well as allowing for manual local activation or remote activation.
A detailed control logic system will be installed to control the operation. This system will have set points to safely shut down the operation in the event of a process upset. The facility is designed to shut down in the event that gas or a fire is detected by site monitoring equipment. The monitoring equipment is integral to the plant operating and monitoring systems.