Containment policy affects tank storage sites

Dr Andrew Fowler of HFL Risk Services explains the COMAH CA Containment Policy and the necessary steps to take in order to comply.

Major incidents have highlighted deficiencies in the way hazardous liquids are stored at many sites and the harm such incidents can cause to the environment, people and property.

Such accidents will also involve significant financial costs to the operators of sites.

In response, the COMAH Competent Authority (CA) comprising the Health and Safety Executive, the Environment Agency and the Scottish Environment Protection Agency, has developed a Containment Policy to set out the key principles relating to the bulk storage of hazardous liquids.

The policy, Containment of Bulk Hazardous Liquids at COMAH Establishments, was published in February of this year, following a four month consultation period between 27 June and 19 September 2007.

It describes measures to improve the protection of people and the environment, both on and off site, as well as safeguarding the supply of fuels and chemicals to the country as a whole.

In a nutshell, it calls for increased standards of containment of liquids (particularly flammable liquids and liquids dangerous to the environment) in three ways.

Primary containment refers to the vessel containing the liquids.

Secondary containment applies to the bunding arrangements.

Tertiary containment is the prevention of liquids (including fire-fighting water) leaving the site or contaminating the ground.

On first reading this document, the industry may feel concerned at the potential costs this policy may have.

For example, ensuring all tank bunds, including the floor under the tank, are impervious to the liquids stored could prove to be very expensive.

The tank would need to be emptied and cleaned, raised on jacks, new foundations laid in concrete or other impervious materials - not inexpensive by any means.

Clearly if you are installing a new tank farm then these increased measures are sensible to reduce the potential risks, but the report states that standards should be raised for existing sites, where reasonably practicable.

The term 'reasonably practicable' is the key here, because this is the term used in the legislation.

It relates to the gross disproportion of the costs and the risk reduction achieved.

Spending a lot of money to reduce the risk a little is grossly disproportionate.

Conversely, spending a little amount of money on a measure that significantly reduces the risk is not grossly disproportionate, and hence the CA would expect such measures to be taken.

It should be recognised that just because a new standard has been adopted, it does not follow that all sites need to be upgraded.

What you need to do in practice is carry out a gap analysis between the measures installed against the measures present in the new standard, and you are duty bound to install any additional measures that are reasonably practicable.

What the new policy does mean, however, is that simple like-for-like replacement at the end of an existing tank's life is no longer possible.

It's not all gloom and doom though.

The policy states that because of some of the substantial costs involved, the time frame for compliance can be fairly long - up to 20 years.

This gives you the opportunity to plan ahead and prioritise, and this plan should be agreed up front with the Competent Authority and contain completion dates for each stage of the upgrading programme.

There is an awful lot in practical terms that can be done.

For instance, you can start by assessing all your tanks and bunds and making sure, for example, that the most hazardous liquids are stored in the highest integrity tanks and bunds.

Also, that alternatives to the ubiquitous drain valves on bunds to remove rainwater are replaced with higher integrity systems.

Carry out topographical surveys, determining where liquids will flow if loss of containment, either of the contained liquid or fire-fighting water, occurs.

In many instances simple installation of kerbing can channel flows to safe locations.

You can start thinking then as to how to move these accumulated liquids to elsewhere on site (for example, into other bunds) before the material flows off site.

There may not be the need to install large sumps or lagoons on site at great expense.

The trick is to think about what could happen and plan now how you will deal with it.

If the worst happens and a tank containing flammable liquids has a fire or there is a pool fire in the bund, is it just a case of rolling out the practiced emergency plan or are you going to think on your feet? The latter often results in ineffective fire fighting and environmental pollution from the fire water run-off.

It should be possible to plan for these events so that you can be assured that you know exactly how you are going to fight the fire.

You will also know how much water and foam you need to put out the fire and cool the adjacent tanks.

You will know, and be able to prove it because you've tested the plan in real exercises, that your fire main delivers the flows and pressures necessary for the monitors on site (or the monitors the local fire brigade can provide).

You will know how much contaminated fire water run-off will occur and where it will flow to.

All of this means that the event will be over as quickly as possible with the least damage possible, not only to the environment, but also your business operations and reputation.

Dr Andrew Fowler is principal consultant at HFL Risk Services and a specialist in process safety and COMAH assessment.

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