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Knowledge Bank:

What is Tertiary Containment?

At a basic level spill containment can be thought of in three containment policies or areas; primary, secondary and tertiary. 

Primary containment refers to the main means of preventing leaks and spills, the equipment that directly contains the materials being stored or transported.

Secondary containment is the area immediately around those containers which could include bunds, booms, drip trays, off-gas treatment systems, interceptors/sumps, expansion vessels, double skinned tanks/vessels, concentric pipes and building structures and ventilation. Secondary containment is essentially your second line of defence if the material containers were to fail.  

Tertiary literally means ‘third’ and is your third line of defence when primary or secondary containment fails. At this point this is starting to sound a bit like the Irishman wearing three condoms joke, to be sure, to be sure, to be sure.

So, is tertiary containment necessary?

Tertiary containment is all too often overlooked with engineers and site managers confident of their primary and secondary containment processes and equipment. However there are three instances where tertiary containment becomes increasingly necessary.

Firstly, as we have alluded to already, you will need tertiary containment when primary and secondary defences fail. 

You would hope that with regular, clearly defined and documented testing, primary and secondary spill containment would work as designed, and there would be no need for that third condom. However, inadequacies are amplified in the case of disaster, particularly where mechanical parts are implemented, such as shut off valves. Proper testing procedures are essential where hazardous or pollutant materials are stored and most environmental management plans specify robust testing and, in most cases, that is adhered to. 

Whilst it is rare, primary and secondary containment failures do occur and a tertiary system is generally recommended to provide that extra level of security and peace of mind.

The second instance of when a tertiary containment area will become necessary is in the event of a spill. The tertiary containment is typically  designed to either contain a spill or direct the flow to a designed catchment area where it can be processed, removed or released back into primary and secondary containment.

It is worth noting that if you were to suffer a spill, and more so if you were to suffer a fire, there will be an investigation in which case you may be required to contain the spill materials for a period of time. In the case of a fire that process could take weeks. In these instances it is most likely that the spill materials would be contained in the tertiary area.

The third instance is the most essential. Statistically it is less likely that you will suffer a spill in primary or secondary containment areas as the majority of spills occur at the point of delivery or collection. In most cases delivery vehicles will not have access to the secondary containment area as that is typically bunded.

In the event of a fire the fire tenders will also not be able to access the secondary containment area for the same reason. A fire would be fought from the tertiary area and the the millions of litres of water or foam that could be discharged, combined with whatever materials you may be handling on your site, will need to be contained. Due to the huge volumes of material involved in fighting a fire the tertiary area would be essential in containing the overflow. You can read more about what firewater is here.  

Which systems should you put in place for an effective tertiary system?

Acknowledging that the objective of tertiary systems is to minimise or prevent the release of spills into the environment upon the failure of primary and secondary systems is the first step to designing a suitable tertiary containment system. Specific risk assessment is required as there are no industry regulations for tertiary systems.

An appropriate design should be created that allows for controlled release or containment throughout the sites boundaries and water courses, whether on the surface or through the drainage network. 

New construction designs should take tertiary containment into account from the outset as tertiary systems are more effort to implement retrospectively, although this is achievable often with manual or temporary designs.

The Environment Agency are taking a failsafe approach when specifying tertiary containment systems and in many cases are recommending extensive bunding beyond the secondary containment area.

We are currently having the most success for our customers by spill mapping their sites and using their current infrastructure including existing roads, kerbs, fencing, sealing the drainage networks and implementing purpose designed, remotely powered and controlled valves.  The result is a fail safe, compliant containment system without the huge disruption of large civil works that has saved our customers hundreds of thousands of pounds.

If spill containment and CIRIA736 compliance is currently a consideration for you please do not hesitate to call 0330 223 4372 or email us, we will be very happy to discuss our solutions with you.




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