Spill Containment Bund Volume Calculator
Work out the minimum secondary-containment (bund) capacity for stored liquids using the common rule — the greater of 110% of the largest single container or 25% of the total aggregate volume — and, if you give a floor area, the required bund wall height. A fast sanity check for chemical, fuel and oil stores.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the volume of the largest single container in the bund, in litres.
- Optionally enter the total stored volume (all containers combined); leave it blank and the tool assumes just the largest.
- Optionally enter the bund floor area in square metres to get the minimum wall height. Read off the required capacity and which rule governs.
How it works
The required capacity is the greater of two figures: 110% of the largest single container (1.1 × largest) and 25% of the aggregate stored volume (0.25 × total). The tool takes the maximum. If a floor area is supplied, it converts the litres to cubic metres (÷ 1000) and divides by the area to give the minimum wall height in metres. When one big container dominates, the 110% rule governs; with many containers the 25% aggregate rule usually wins.
Worked example
Worked example. A store holds five 1000 L drums (5000 L total). 110% of the largest = 1.1 × 1000 = 1100 L; 25% of the aggregate = 0.25 × 5000 = 1250 L. The greater is 1250 L, so the aggregate rule governs. Over a 4 m² bund floor that needs a wall at least 1250 / 1000 / 4 = 0.3125 m high.
Common mistakes
- Sizing to 110% of the largest container only. With multiple containers the 25% aggregate figure is often larger and governs — always take the greater of the two.
- Forgetting extra allowances. Open (outdoor) bunds may need capacity for rainfall, and space taken by tanks/plant inside the bund reduces the free volume — add margins accordingly.
- Mixing units. Keep all volumes in litres and the floor area in square metres; the height comes out in metres after the litres-to-cubic-metres conversion.
Frequently asked questions
Where does the 110% / 25% rule come from?
It is a widely used containment rule of thumb reflected in AS 1940 (flammable and combustible liquids). The precise requirement depends on the dangerous-goods class, quantity, indoor/outdoor location and your jurisdiction's EPA/WHS rules — always confirm the applicable standard for your store.
Does the bund only need to hold one container's worth?
Not necessarily. The rule takes the greater of 110% of the single largest container and 25% of everything stored, so a bund with many containers must hold at least a quarter of the total even though no single container is that large.
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