Major accident hazards

The Control of Major Accident Hazards Regulations 1999 (COMAH) apply to sites where particular quantities of toxic, highly flammable or otherwise dangerous substances are present (Regulation 3). The substances and threshold quantities are set out in Schedule 1. The regulations do not apply to defence establishments, or to substances which present ionising radiation hazards.

The operator, defined as the person in control of the site, must take all necessary measures to prevent major accidents and limit their consequences to people and the environment (Regulation 4). They must prepare and keep a document setting out their major accident prevention policy (MAPP). This must make reference to the safety management system that will be used to put the policy into place (Regulation 5).

The competent authorities (the HSE and Environment Agency acting jointly in England and Wales, and the HSE and Scottish Environmental Protection Agency in Scotland) must be notified of the name and address of the operator; the address of the establishment; the name or position of the person in charge, and details of dangerous substances on site and environmental details (Regulation 6).

There are two thresholds set out in the regulations. If enough dangerous substances are present, additional top-tier duties apply. These are set out in Regulations 7-14. A safety report detailing the safe operation of the site and arrangements for preventing major accidents must be submitted to the competent authority. This should be revised and reviewed at least every five years or sooner if significant changes have been made or there is new knowledge about safety matters (Regulation 8).

Operators must prepare an emergency plan to deal with the on-site consequences of a major accident (Regulation 9). The regulations specifically require operators to consult safety representatives about the preparation of the on-site emergency plan. Operators must provide information to the local authority in order for it to prepare an off-site emergency plan (Regulation 10). Emergency plans must be reviewed and tested at least once every three years (Regulation 11).

Individuals who could be affected by a major accident at the establishment, such as those living in the vicinity, must be given information, including details of the dangerous substances, the possible major accidents and their consequences, and what to do in the event of an accident (Regulation 14). Gas storage in depleted reservoirs is within the scope of the COMAH Regulations 1999, following a European Commission review. Previously, this was regulated by HSE under the Borehole Sites and Operations Regulations 1995.