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The Control of Major Accident Hazard Regulations (COMAH)

The Control of Major Accident Hazards Regulations (COMAH) implemented the Seveso-III (Directive 2012/18/EU) in Great Britain (Control of Major Accident Hazards Regulations (Northern Ireland)), except for land-use planning requirements, which are implemented by changes to planning legislation. They replaced the Control of Industrial Major Accident Hazards Regulations 1984 (CIMAH) which implemented the original Seveso Directive (82/501/EEC). They came into force on 1 April 1999, were amended by the Control of Major Accident Hazards (Amendment) Regulations and subsequently replaced by the current Control of Major Accident Hazards Regulations.

Their purpose is to prevent major accidents involving dangerous substances and limit the consequences to people and the environment of any that do occur. COMAH applies mainly to the chemical industry, but also to some storage activities, explosives and nuclear sites, and other industries where threshold quantities of dangerous substances identified in the Regulations are kept or used.

COMAH is enforced by the Health and Safety Executive (HSE) and the relevant environment agencies – the Environment Agency (EA), the Scottish Environment Protection Agency (SEPA), and Natural Resources Wales (NRW) - working together as the COMAH Competent Authority (CCA). Operators will generally receive a single response from the CCA on all matters relating to COMAH.

The mechanism for determining whether COMAH applies has been simplified: an establishment with any listed substance present above the qualifying quantity is subject to the Regulations. There are two thresholds, known as lower-tier and top-tier. Further details can be found in the COMAH regulations and accompanying guidance.

Even if substances are not present at an establishment in threshold quantities, the establishment may still be subject to the Regulations if specified dangerous substances could be produced in threshold quantities as a result of the loss of control of an industrial chemical process.

Where the Secretary of State holds an exemption with respect to COMAH, the Major Accident Control Regulations (MACR) for the Ministry of Defence (MoD) are intended to discharge the Secretary Of State for Defence requirement to have arrangements in place that are at least as good as those required by statute

More information on the Regulations and how to comply with them can be found on the Health and Safety Executive website.

Lower-tier duties

If the lower-tier threshold is equalled or exceeded, operators must notify the competent authority. The local Health and Safety Executive office should be notified; they will pass the details to the relevant environment agency office.

Operators of all establishments subject to the Regulations must notify certain basic details to the competent authority. The key points that must be included in the notification are:

  • Name and address of the operator
  • Address of the establishment
  • Name or position of the person in charge
  • Details of the dangerous substances on site (a breakdown is required for petroleum products)
  • Site activities
  • Environmental details

Site operators must take all necessary measures to prevent major accidents and limit their consequences to people and the environment.

This is the general duty on all operators and underpins all the regulations. It is a high standard and applies to all establishments within scope. Requiring measures both for prevention and mitigation recognises that all risks cannot be completely eliminated. This in turn implies that proportionality must remain a key element in the enforcement policy of the Health and Safety Executive and the environment agency. Thus, the phrase ‘all measures necessary’ will be interpreted to include this principle and a judgment will be made about the measures in place. Where hazards are high, then high standards will be required to ensure risks are acceptably low, in line with Health and Safety Executive and environment agency policy that enforcement should be proportionate. Prevention should be based on the principle of reducing risk to a level as low as is reasonably practicable (ALARP)’ for human risks and using the best available techniques (BAT) for environmental risks. The ideal should always be to avoid a hazard altogether wherever possible.

The Regulations require lower-tier site operators to prepare a document setting out their policy for preventing major accidents; this is known as a major accident prevention policy or MAPP.

The MAPP will usually be a short and simple document setting down what is to be achieved but it should also include a summary and further references to the safety management system that will be used to put the policy into action. The detail will be contained in other documentation relating to the establishment (e.g. plant operating procedures, training records, job descriptions, audit reports) to which the MAPP can refer.

The MAPP must also address issues relating to the safety management system. The key areas are:

  • Organisation and personnel
  • Identification and evaluation of major hazards
  • Operational control
  • Planning for emergencies
  • Monitoring, audit and review

Top-tier duties

If any top-tier threshold is equalled or exceeded, the operator must comply with additional requirements.

Site operators must prepare a safety report; a safety report is a document that provides information to demonstrate to the competent authority that all measures necessary to prevent and mitigate major accidents have been taken.

The safety report must include:

  • Policy on how to prevent and mitigate major accidents
  • Management systems for implementing that policy
  • Effective methods for identifying any major accidents that might occur
  • Measures (such as safe plant procedures and safe operating procedures) to prevent and mitigate major accidents
  • Information on the safety precautions built into the plant and equipment when it was designed and constructed
  • Details of measures (such as firefighting, relief systems and filters) to limit the consequences of any major accident that might occur
  • Information about the emergency plan for the site, which is also used by the local authority in drawing up an external emergency plan

Safety reports will be available to the public via the competent authority registers, subject to safeguards for national security, commercial and personal confidentiality.

Site operators must update the safety report after significant changes, new knowledge about safety matters or every five years.

Safety reports need to be kept up to date. If there are any modifications to the plant or the way it is operated or if new facts or information become available, the safety report must be reviewed and, if necessary, revised at the time. It must be reviewed after five years even if there have not been any changes. The operator must notify the competent authority of any revision, and also if the five-year review does not lead to a revision.

Site operators must prepare and test an on-site emergency plan

Top-tier operators must prepare an emergency plan to deal with the on-site consequences of a major accident.

Site operators must supply local authorities with information for off-site emergency planning purposes.

Local authorities (the fire and rescue service in London and other metropolitan areas) play a key role by preparing, reviewing, revising and testing external emergency plans for dealing with the off-site consequences of major accidents at top-tier sites. To fulfil this role they need information from operators. Operators will need to hold discussions with their local authorities to determine their exact needs.

Site operators must provide certain information to the public about their activities

People who could be affected by an accident at a COMAH establishment must be given information without having to request it. Safety reports must also be made available to the public via public registers.

Operators planning to build new top-tier establishments must submit information in advance of construction and wait for the competent authority response before starting to build safety-critical parts of the establishment. This is to ensure that safety is considered fully at the design stage.

The COMAH regulations specifically require operators to consult their employees or employees’ representatives about the preparation of the on-site emergency plan. Consultation with those doing the work is crucial in raising awareness of the importance of health and safety and environmental protection. It can make a significant contribution to creating and maintaining a safe and healthy working environment and an effective health and safety culture. In turn, this can benefit the business, making it more efficient by reducing the number of accidents and the number of work-related ill-health incidents.

On receipt of the safety report the competent authority should inform employee representatives and provide the name of the assessment manager. If the competent authority finds serious deficiencies in the safety report, it will copy any related correspondence it has with operators to employee representatives. Similarly, the competent authority will copy the letter informing the operator of its conclusions of the assessment of the safety report, to employee representatives.