Hi David

I don't think that there is a minimum volume, but  given that the standard recommendation is that bunding should be usually such as to contain 110% of the volume of the largest (metal) container if you had lots of very small containers, the bund would be of minimal height and less if the storage is in an area which slopes towards an exterior wall.

Lots of guidance in HSG51 and other sources.

As Peter says 110% of largest container that may leak

https://www.hse.gov.uk/comah/sragtech/techmeascontain.htm

If you look to "off the shelf" solutions for drums & IBC's the bund capacity is a minimum 110% of the container volume.

Then you work to what you have / can fabricate or what you can purchase.

Smallest commercial bund is typically one 205Ltr drum bund capacity @ 230 Litres.

No association https://www.arco.co.uk/search?Ns=PriceGBP%7C0&Ntt=bund

Spill trays can range from 10ltr capacity upwards.

When you are looking to multiple smaller units you need to consider how many could simultaneously leak to size your bund at 110% of this theoretical volume.

e.g. if you have twenty x 50 Litre containers on a pallet is it conceivable all twenty could rupture if the pallet failed? If so you need a bund capacity of 20 x 50 x 110% = 1,100 Litres.

It all comes down to what is the "Risk" if the substance or mixture spills - ground contamination, Efffluent Treatment Plant impacted/ruined, enters drains/waterways/rivers, fine and/or remediation costs from the Environment Agency / Local Water Authority.

Edited by user 10 August 2021 16:04:57(UTC)  | Reason: FFS

If the quantity of liquid was so small that a leak with loss of the whole container contents wouldn't cause a problem, then there would be no reason to bund it.

This is rarely the case.

50 litres of anything is an enormous quantity if it leaks.  So is 5 litres.  Liquid can spread out over an alarmingly large area, and, if outdoors, get into drains.

Normally bund capacity should be 110% of the volume of the largest container or 25% of the total volume whichever is the greater. However, you should consider what is the likelihood of multiple failures at the same time. What it is may come into play. The other aspect is how much of this substance would you be ok with not being contained. 50L of water may not cause you much concern, 50L of oil is hard work to clean up, 50L of something nasty may be unacceptable. Don’t forget disposal costs of the now contaminated substance and any special UN approved containers it may have to be put into. This can make the cost of a bund good value for money.

Chris