We often get asked, what does AS1940 say about bunding and what do I need to be aware of?
The Australian Standard AS1940 is available for purchase on the Standards Australia website however here is some points we've found in relation to spill containment bunding in this document that you need to consider.
First of all, what is a bund?
The Australian Standard AS1940 describes a bund as; An embankment or wall which may form part or all of the perimeter of a compound. Industroquip have a large range of bunding products ranging from bunded pallets to rubber hump bunding that can be fixed to your floor and even collapsible temporary bunding for temporary site applications.
A bund is An area bounded by ground contours or by a bund, and intended to retain spillage or leakage. This includes the floor of the compound. Any potential flow of spillage shall be prevented from reaching a
protected place, watercourse or property boundary by such means as the use of natural ground slope, or the provision of a diversion channel, kerb or bund.
Spill Containment Bunding Requirements
Provision shall be made to contain any leaks or spillages, and to prevent them from contaminating the surrounding soil or entering any watercourse or water drainage system.
The following requirements apply:
- A spillage containment compound shall be sufficiently impervious to retain spillage and to enable recovery of any such spillage. The compound shall be chemically resistant and fire resistant as far as is necessary to fulfil its functions.
NOTE: Portable bunding units, e.g. bunded pallets, or flexible bunding units are not suitable for permanent storage as there are no uniform performance criteria for chemical resistance or fire resistance and they can be easily moved to an unsuitable location. They may be suitable for the short-term holding of damaged packages, or where goods are in transit or in manufacturing and handling areas.
- Pipework that is intended to convey any spilt liquid to a remote holding tank or compound shall be resistant to fire. Flashback into the store or flashover between storage compartments shall be prevented.
- The capacity of the spillage containment compound shall be at least 100% of the volume of the largest package plus 25% of the storage capacity up to 10 000 L, together with 10% of the storage capacity between 10 000 L and 100 000 L, and 5% above 100 000 L.
- If a water-based automatic or manual fire suppression system is installed, the compound capacity shall be increased by a volume equal to the output of the system over 20 min. Any drainage system shall be capable of carrying the output of the sprinkler system over the assumed area of operation at the design density of discharge (see AS 2118 series). NOTE: The compound should be designed to provide a minimum surface area for the storage.
- The drainage of any rainwater or fire water to outside the compound shall either be;
- via a suitable interceptor or separator (e.g. a molecular sieve); or
- after sampling and testing of the water.
- Where more than one storage is connected to a common compound, drainage tank or pit, the capacity of the compound shall be equal to the largest compound required for any one store, plus 25% of the capacity of the compounds required for the other stores connected to it.
The net capacity of a bund must be at least the capacity of the largest tank. The capacity of on-site containment shall be increased to include the output of any fire water over a 20 min period. If two or more tanks are operated as a single unit, then the capacity of all such tanks shall be used when calculating the capacity of the compound.
When designing and constructing an earthen bund, account shall be taken of subsidence in the construction materials. In no case shall the bund be less than the nominated capacity. In addition, original height markers shall be installed on earthen bunds..
Design and construction of bunding
A compound and its associated bund shall comply with the following requirements:
(a) It shall be sufficiently impervious to retain spillage and to enable recovery of any such spillage.
NOTE: When earthen bunds are used, consideration should be given to the minimization of penetration of the bund surface, because of permeability, in the event of a spill.
(b) In a fire situation, the bund shall retain the structural integrity.
(c) Any bund or compound floor shall be designed to withstand the hydrostatic head when full.
(d) Any earthen wall 1 m or more in height shall have a flat section at the top at least 600 mm wide.
(e) The slope of any earthen wall shall be consistent with the angle of repose of the material from which the wall is constructed.
(f) A bund shall not be higher than 1.5 m above interior grade unless means for safe and rapid entry and exit are provided.
(g) Any pipe that passes through a bund shall be designed to prevent excessive stresses as a result of settlement or expansion resulting from fire exposure. The joint between the pipe and the bund shall be sealed to prevent leakage.
(h) The location of a bund relative to the closest tank shall be such that the top inside perimeter of the bund is not inside the crest locus limit.
(i) Where flammable liquids are stored, the distance from the top inside perimeter of the bund to protected places or on-site protected places shall be at least one half of the specified separation distance given in Table 5.4 in the standards booklet or 15 m, whichever is less.
1 It is preferable to have moderately high bunds, rather than shallow bunds, so as to minimize the area of fuel burning in the event of a fire.
2 Consideration should be given to access between groups of bunded areas for emergency vehicle access.
3 Alternative methods of construction may be used to ensure containment of spills and tank shell leaks.
Intermediate bulk containers (IBCs) of up to 1.6 m3 capacity may be stored in a package store provided that—
1. They are not connected to any piping or product delivery system;
2. The ventilation and spillage control provisions are adequate to cater for the quantity of IBCs being stored;
3. The IBCs are stored at least 1 m from the bund or edge of the store, unless splash shields or baffles constructed from compatible, non-combustible materials are used;
4. They comply with the ADG Code; and
5. The IBCs are not stacked more than two high unless purpose-built racking is provided.
Bunds shall be maintained so as to retain their designated capacity and in a condition which will prevent the escape of liquid from the compound.
All bunds shall be kept free from extraneous combustible material, e.g. packaging, pallets, tree branches, leaves.
For earthen bunds, original height markers shall be checked regularly and the bund height maintained to those levels.
Vehicle Access over a bund
Any vehicular access over a bund and into a tank’s compound shall be kept barricaded and locked when not in use.
A safety sign with the words NO VEHICLE ACCESS WITHOUT WRITTEN PERMIT, in red letters in 150 mm high on a white background, shall be displayed at the access point.
Unless otherwise specified, extinguishers shall be located within 10 m of the tank and shall be positioned outside of any bund.
Spill Kit Requirements
A spill response kit is now a mandatory requirement for sites handling Class 3 flammable liquids. The kit should consist of “some or all of absorbent pads, booms, loose absorbent and contaminated waste bags that are packed in a readily identifiable reuseable weather-resistant container and are compatible with liquids stored”.
We trust this gives you some outline of what is included in the Australian Standards for bunding, this is a brief outline and does not substitute reading the full AS1940 documents.
For further assistance call our Spill Control team on 1300554192 or browse our huge range of spill bunding and spill control products online.