A bund wall is a constructed retaining wall around storage areas “where potentially polluting substances are handled, processed or stored” (Pollution Prevention Guideline – PPG 16). Regulations differ across the world but in general they require that bunding should be sized to hold 110% of the largest tank capacity or 25% of the total tank capacity whichever is greater. Bund walls are generally made from concrete, which makes them a solid and long-lasting choice. However, if concrete is used it needs to be designed, poured and cast correctly to ensure that it’s fully impermeable.

It is also advisable to use bund wall construction that’s fire resistant as a fire can weaken the integrity of the base and walls of a bund, which can lead to failure when subjected to dynamic loads. To help protect against this it is a good idea to install firestops or protection plates to the joints in the concrete of your bund walls and at any penetration seals.

Building a Strong Foundation: The Basics of Bund Wall Construction

The height of bund walls can vary from low to high, the lower wall height facilitates firefighting and can limit ventilation but it can be a poor defence against ‘spigot flow’ where a leak in the wall of a tank causes water to jet out and pass over the bund wall before reaching the ground. Taller walls are better against this but constructing them can take up valuable space on a site. Ideally, a 750 mm separation distance should be maintained between a tank and the bund walls but it can be difficult to maintain this at an oil bund where the tanks are often very close together.