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• Traffic Incident Management Bulletin

February 2010

The TIM Bulletin has previously featured various initiatives to prevent and mitigate the effects of external incidents which have the potential to cause disruption on the strategic road network.

One of the risks to the network is industrial sites adjacent to the road network. An incident at one of these sites has the potential to close roads on the local and strategic road network, which can have a significant impact on the Highways Agency and their day-to-day operations.

This article gives an insight into Control of Major Accident Hazards (COMAH) and the planning the Highways Agency is currently undertaking to mitigate the risks associated with them.

COMAH regulations

The COMAH regulations were published in 1999, and the Health and Safety Executive (HSE), who are responsible for enforcing the regulations in England and Wales, state the main aim is to:

Prevent and mitigate the effects of those major accidents involving dangerous substances, such as chlorine, liquefied petroleum gas, explosives and arsenic pentoxide which can cause serious damage/harm to people and/or the environment.

The chemicals mentioned above, among others, can be hazardous, and therefore the regulations place requirements on the operators of sites which hold significant quantities of dangerous substances. These are categorised as either top tier or lower tier sites. The quantities involved vary depending on how hazardous the chemical is, and this will determine the categorisation of the site.

Top tier site requirements

The site operator has a duty to prepare a safety report and an on-site emergency plan. The local authority has a duty to prepare a multi-agency off-site plan. This plan will detail the multi-agency response that is required for an off-site incident - one which causes (or has the potential to cause) effects outside the perimeter of the site.

The Highways Agency's Regional Emergency Planning Unit will liaise with the local authority to ensure that the off-site emergency plan includes details about the implications of a COMAH incident on the strategic road network. The plan will state what actions are required by the Highways Agency if an incident occurs at the site. This will include actions to mitigate the immediate effects of the incident on the strategic road network and road users, and also to facilitate other aspects of the emergency response such as evacuation of local people, or access to the scene for the emergency services. This will typically involve implementing road closures and establishing diversion routes. The plan should also include the various sources of information the Highways Agency can provide to the public through its media services.

Lower tier site requirements

The requirements on the operators of lower tier sites are less onerous than the top tier sites, and their predominant requirement is to notify the HSE of various details and to take necessary measures to prevent major incidents and limit their consequences. However, these sites may still impact on the local or strategic road network if an incident occurs.

What is a major incident?

The definition of major incident within the COMAH regulations is:

"An occurrence (including in particular, a major emission, fire or explosion) resulting from uncontrolled developments in the course of the operation of any establishment and leading to serious danger to human health or the environment, immediate or delayed, inside or outside the establishment, and involving one or more dangerous substances".

Impact on the strategic road network

There are two specific elements of COMAH that may impact on the Highways Agency and its road network:

• If the strategic road network is located within the public information zone then there will be a large number of people that could be affected by a major accident. As such the off-site emergency plan produced by the site should identify the risks associated with this and ensure a communication and response strategy is documented and tested to ensure it could be implemented during an emergency
• The off-site emergency plan is likely to include traffic restrictions, and these may include closures or diversions on the local or strategic road network

However, incidents on lower tier sites and, in some cases, on a site containing hazardous materials outside the scope of COMAH may also result in an impact on the strategic road network. It is therefore important for site operators to liaise with the Local Resilience Forum, including the Highways Agency to ensure all emergency plans produced are integrated and feasible.

Operator's off-site emergency plan

An off-site emergency plan is developed by the local authority for all top tier sites. The plan will contain the information which is required by responders to react to an incident on-site, such as:

• Risks and incident scenarios
• Methodology of providing warning and information
• Notification protocol
• Roles and responsibilities of each of the organisations and responders
• Off-site management and public information
• Rendezvous and police control points
• Process for testing and exercising all agencies involved

Emergency planning role and responsibilities

Many responders will have an involvement in assisting in the development of an off-site emergency plan. This will typically involve the site operator, local authority, police, fire and rescue service and the Environment Agency. Where there is a specific risk to the strategic road network this will also include the Highways Agency and its partner organisations. The Highways Agency Emergency Planning Managers, in conjunction with Atkins, have been developing a risk model which will ensure a consistent approach to managing the risk of disruption to the network resulting from accidents at COMAH sites.

The Bulletin has previously reported on Exercise Flagler which demonstrates the approach taken by Durham and Darlington Civil Contingencies Unit to exercising an off-site emergency plan at a local chemical plant.

What happens when an incident occurs?

In many cases, for the Highways Agency a COMAH incident may only involve a routine response such as implementing road closures, diversions routes and providing information for road users. However, there may also be added complexities such as traffic trapped within a hazardous area or traffic trapped for long periods behind the closures or on the diversion routes.

In December 2005 a major accident occurred at the Buncefield Fuel Depot in Hemel Hempstead, Hertfordshire. A flammable vapour cloud spread over and beyond the site and was ignited. This resulted in a violent ignition with explosions and fires in the vicinity of the depot. There was significant damage to both commercial and residential properties and a large area around the site was evacuated. As a result of the incident about 2000 people were evacuated from their homes and sections of the M1 near to the site were closed. The fire burned for five days resulting in a smoke plume covering much of South East England.

The final report of the Major Investigation Board identifies that the closure of the M1 caused "major, temporary transport disruption to this part of the UK". It also recognised an innovative use of the motorway with the "M1 closed to all traffic in the vicinity of Buncefield. This otherwise busy stretch of motorway was for a time used to keep emergency vehicles assigned to the incident response". The report goes on to identify that one of the un-quantifiable financial effects of an incident of this magnitude is the closure of motorways such as the M1, M10 and M25.

The M1 was closed between Junction 6a at the M25 and Junction 10 in both directions. Strategic diversions were implemented across the East of England with diversion routes using the M25, A1, A14, M11, M42 and M40.

Has this article been worthwhile reading? Why not take a moment to send us your comments, thoughts, or questions. Please email TIMBulletin@highways.gsi.gov.uk