Let’s look at a common scenario.  You have an intermediate bulk container (IBC) stored out in the open on your site, and it contains up to 1,000 litres of cleaning fluid for your operations.

Do you need to have secondary containment (also known as ‘bunding’) around it?

Can You See a Potential Problem Here?workplace outdoor storage area near stormwater drain


The answer would be… YES.  As a part of your site compliance most primary containers (IBC’s, fuel tanks, drums and so forth) should include a second containment measure to mitigate the risk of liquid spill – should the primary container spring a leak.

You may, at this point, be nodding your head…. or scratching it.  You have spill containment  products. A spill kit – and the container does not leak, right?

Close – but no cigar.

The secondary containment is also required to limit the potential damage that could result from a potential spill.  What if the primary container ruptures, splits or is damaged somehow when you are away from the site or after hours?  No one would see it until morning when it would probably be too late to stop the resulting spill entering a drain or waterway.

So…. what exactly is secondary containment (aka ‘bund’)?

Technically, it is an impervious embankment of earth, brick, stone, concrete or other suitable material, which may form part or all the perimeter of a compound that provides a barrier to retain liquid.  It is used to surround one or more primary storage containers with the ability to collect any hazardous materials that spills from the primary containers – in the event of loss of integrity or container failure (a spill).

But…. it must be compliant.

Aluminium Floor Bunding across the doorwayaluminium floor bunding across warehouse entry


So, how do you know your site is compliant when using secondary containment (or bund).  There are a range of legislative requirements that can vary in accordance with the liquids you are storing, and how they are being stored.  If you have portable containers (such as drums), or permanent ones (such as tanks), it may be a different solution to protect from spills.

The capacity of the bund, its construction, its portability and its environment are all factors that may determine the most suitable form of bund that should be protecting your primary storage containers or hydraulic equipment.

So let’s look a little at compliance.

Firstly, your secondary containment system must be in good condition – free of cracks or gaps that would ruin the impervious nature of the bund.  It is worth your while to inspect the bunds and their accessories (valves, bungs and so forth) regularly.  If you have trouble doing this then have an inspection done by a third party, to ensure their integrity.

Secondly, the bund must have sufficient capacity to contain (generally) at least 110% of the total volume of the largest primary container within the bunded area, or 25% of the total volume all containers, whichever is greater.

Third, the bund should be easily cleaned out, and its capacity should allow room for displacement of the primary container stored within.  If you place a solid object within the bund, does the displacement reduce the overall capacity of the bund?

Hmm, Pythagoras would love our regulatory authorities for this.

Say you have 3 x 200 litre drums, 5 x 20 litre drums and a few 5 litre cans in a bunded area.  To be compliant your bund should have a capacity of at least 220 litres (110% of 200 litres)

How you feeling now?  Confused yet?  But wait… there’s more.

If your bund is outside (as many are) then you also need to be mindful of Mother Nature.  Rainfall could fill your bund so when a spill happens, the bund can overflow.  This may be remedies simply by a cover, or it may require ongoing inspection and pump out.

You need to maintain your facilities, or have someone do it for you. Don’t risk being non-compliant.  Talk to someone who can advise you on the best type and size of secondary containment.