In order to provide adequate containment of tank contents in the case of tank failure, bunds need to be sized correctly. For sites covered by EPA IPPC or Waste licenses, local authority Consents to Discharge and general planning conditions the rules are summarised below. Where there is no legal requirement to bund, then the rules below would be considered good practice.
Where a bund contains a single tank, then the bund volume should be 110% of the size of the tank.
Where there is more than one tank in a bund, then the bund volume should be the greater of either 110% of the largest tank or 25% of the total tank volume. It follows from this that it is more economic to place a number of tanks within the same bund. It should be noted that interconnected tanks are treated as one tank.
Based on these rules it is possible to design a bund of the correct volume. However, there are other considerations that need to be taken into account. These include the height of the bund wall (if it is too high it can impeded fire fighting, create a confined space and make inspection difficult), the removal of rain water, distances from tanks to bund wall, jetting failure and so on.
Environmental Efficiency can give appropriate advice on the sizing and construction of bunds to ensure compliance with the rules and avoidance of mistakes. Where there are existing bunds, we can review the bund capacity and construction and make proposals for cost effective changes to bring bunds up to standard.