A bund drainage system should be designed to retain the contents of a drum or tank if there is a leak. This is not easy to do and requires good design skills. The minimum distance between a drum or tank and the toe of the interior bund wall at ground level should be at least 3 metres. This will also prevent the spill from one tank endangering adjacent tanks within that bund area. Any access points (taps, filling points etc) should also be included in the bund to prevent the soil around them from becoming contaminated by leaking chemicals or fire fighting foam.

Breaches of bunds are a serious problem and can cause significant environmental and economic damage. Breaches can occur where a liquid escapes through the bund walls, floor or any penetration seals (e.g. for pipes). Bunds should be regularly assessed for integrity, with hydrostatic testing or visual inspections carried out if necessary.

Implementing Effective Bund Drainage Systems: Strategies and Considerations

Effective bunds must be able to capture and contain the intended liquid as well as rainwater. This unwanted water may build up in the bund reducing its capacity. Rainwater needs to be removed and the contents of any containers should be tested for contamination before being disposed of or pumped into a suitable control measure (e.g. effluent tank).

The most effective type of bunds are made of stone which is highly resistant to erosion. This reduces the need for extensive maintenance and repairs but they still require periodic checks to ensure they are structurally sound. Concrete bunds, however, require regular maintenance. Their construction must be robust enough to withstand the anticipated dynamic load and they need to be regularly cleaned and maintained to ensure that they can contain the expected amount of liquid.