COMAH — Control of Major Accident Hazards Regulations and Petrochemical Site Cleaning Compliance

The Control of Major Accident Hazards Regulations 2015 (COMAH 2015) implement the EU Seveso III Directive in UK law and apply to establishments where dangerous substances are held above specified threshold quantities. COMAH sites include oil refineries, petrochemical plants, chemical manufacturing facilities, fuel storage depots, LNG terminals and some pharmaceutical and agricultural chemical sites. COMAH sites are regulated jointly by HSE and the Environment Agency (or SEPA in Scotland). Cleaning and maintenance on COMAH sites is carried out within a permit-to-work system of exceptional rigour -- the consequences of an ignition event, chemical release or process upset caused by inadequate contractor management are potentially catastrophic. For cleaning contractors working on COMAH sites, the equipment specification, the permit-to-work compliance and the ATEX zone awareness requirements are the most critical operational distinctions from general industrial cleaning.

The COMAH framework

COMAH 2015 -- the two tiers

COMAH sites are classified as lower tier or upper tier based on the quantity of dangerous substances held. Upper tier sites hold quantities above the upper threshold and have more demanding requirements including Major Accident Prevention Policy (MAPP), Safety Report, on-site and off-site emergency plans and regular HSE inspection. Lower tier sites have less demanding requirements but are still subject to significant regulatory oversight.

Safety Management System

COMAH sites operate a formal Safety Management System (SMS) that controls all activities on site including contractor management, permit to work, management of change, and emergency response. Cleaning and maintenance contractors must be inducted into the SMS before commencing work and must work within the permit-to-work system at all times.

Permit to Work

Every cleaning and maintenance activity on a COMAH site requires a permit to work issued by the site authority. Hot work permits cover any activity that could cause an ignition -- welding, grinding, cutting. Cold work permits cover activities without ignition risk but with other hazards. Entry permits cover confined space entry. Electrical isolation permits cover work on or near electrical systems. For cleaning contractors, a permit to work is required before any pressure washing, vacuum cleaning or dust extraction activity on a COMAH site.

ATEX zones on COMAH sites

COMAH sites contain extensive ATEX-classified hazardous zones around process equipment, storage vessels, loading and unloading facilities, and drainage systems. DSEAR 2002 requires ATEX zone classification for all areas where flammable atmospheres may exist. Standard cleaning equipment -- pressure washers, vacuum cleaners, dust extractors -- is not ATEX-rated and cannot be used in classified zones.

For cleaning contractors working on COMAH sites:

All equipment must be assessed for ATEX zone suitability before use in any area of the site
Equipment used in classified zones must hold the appropriate ATEX certification for the zone category
Equipment used outside classified zones but within the site boundary must be intrinsically safe or approved for use on site under the SMS
Petrol and diesel cleaning equipment is generally prohibited on COMAH sites due to ignition risk -- electric and pneumatic equipment is preferred

See: DSEAR and ATEX guidance

Bund and containment area cleaning

Bunds -- secondary containment areas around storage tanks and process vessels -- accumulate rainwater, product spillage and contamination from vessel maintenance. Bund cleaning is a high-frequency cleaning task on COMAH sites. Key requirements:

Bund water must be tested before disposal -- product contamination above threshold levels means bund water is hazardous waste requiring licensed disposal, not trade effluent
Hot work is prohibited in bunds that may contain flammable vapour from product spillage -- all cleaning must be carried out under cold work permit
Bund drains are typically closed to prevent contaminated water from entering the drainage system during normal operations -- check drain position before pressure washing
Vacuum tankers or industrial wet vacuums are typically used to remove accumulated bund water before pressure washing

Wash bay and vehicle cleaning on COMAH sites

Vehicle and equipment wash bays on COMAH sites must be designed and operated to prevent contaminated wash water from reaching surface water drainage or the environment. Trade effluent consent is required for discharge to foul sewer. Interceptors are required to separate hydrocarbons from wash water. Vehicle wash water on petrochemical sites may contain product contamination -- the trade effluent quality monitoring requirements are typically more demanding than for a general vehicle wash facility. See: Environmental Permitting guidance

Major UK COMAH sites by location

Major COMAH sites in the UK include the Fawley refinery (Hampshire), Stanlow refinery (Cheshire), Grangemouth refinery and petrochemical complex (Falkirk), Humber refineries (Immingham and Killingholme), Ellesmere Port (Merseyside), Teesside chemical complex (Cleveland), and numerous fuel storage depots and chemical distribution facilities across the country. V-TUF holds UK warehouse stock with next-day delivery to all major UK industrial areas.

Related legislation and compliance

Related sector pages

Chemical industry hub | Oil, gas and mining hub | Fuel forecourts and tanker cleaning | Manufacturing hub

Trade accounts for COMAH site contractors

V-TUF supplies electric pressure washers, industrial vacuums and extraction equipment to cleaning and maintenance contractors working on COMAH and petrochemical sites across the UK. Equipment suitable for use outside classified ATEX zones. For ATEX-rated equipment requirements within classified zones, contact the V-TUF trade team for guidance on suitable alternatives.

Telephone: 01522 787978. Email through the contact page.