Bunding for Spill Containment in Australia

What is bunding?

Bunding is a form of secondary containment, an impervious physical barrier designed to prevent liquids, such as oil, fuel, and chemicals, from escaping into the surrounding environment in the event of a spill or leak. Its purpose is to stop spilled liquids from reaching stormwater drains, soil, groundwater, or waterways.

When an area is described as bunded, it means it has been intentionally designed to contain the largest spill that could occur within that space.

Common examples of bunded areas include:

• Drum storage areas with floor bunding
• Bunded pallets holding chemical drums or IBCs
• Wash-down areas with bunded perimeters

Liquids that require bunding

• Oils and lubricants
• Fuels and hydrocarbons
• Chemicals and hazardous liquids

These substances are commonly stored or handled in drums, tanks, IBCs, or plant equipment where leaks, overfilling, or equipment failure can occur.

Workplace health and safety

While bunding’s primary purpose is to prevent environmental damage and reduce the scale and cost of clean-up activities. Effective bunding also helps to:

• Reduce slip and fall hazards
• Limit fire and explosion risks
• Minimise worker exposure to hazardous substances

Contained spills are safer and easier to manage.

Regulatory compliance

Australian environmental regulators expect businesses handling liquids to implement preventative containment measures.

Failure to adequately contain spills can result in:

• Operational disruption and reputational damage
• EPA enforcement action
• Clean-up and remediation orders
• Financial penalties and fines

Key point: A bunded area exists for containment only, not treatment or clean-up.

Typical bunded area layouts

Bunded areas are commonly used around:

• Drum storage areas
• IBC storage zones
• Plant and equipment handling liquids
• Wash bays and wash-down areas
• Decanting or transfer points

While layouts vary, the containment principle remains the same.

High-level types of bunded areas

Bunded areas may be formed using:

• Bunded pallets – self-contained units with integrated sump capacity
• Floor bunding – raised kerbing installed on existing slabs
• Concrete bunds – permanently constructed containment walls

These approaches describe how bunding is formed, not whether it meets capacity requirements.

Bunding Requirements in Australia (The 110% Rule Explained)

In Australia, regulators focus on whether a spill can be completely contained on site without reaching soil, stormwater, or waterways.

While requirements vary by state and industry, environmental authorities apply a consistent compliance principle across Australia.

The 110% rule

Australian EPA and Standards

Australian regulators, including EPA NSW, refer site operators to applicable Australian Standards (such as AS 1940 – Storage and Handling of Flammable and Combustible Liquids) when determining capacity requirements.

In practice, this means a bund must be capable of containing at least 110% of the volume of the largest container stored, or 25% of the total stored volume, whichever is greater, to meet accepted secondary containment expectations.

Supporting government references

EPA Victoria – Liquid storage and handling guidelines
https://www.epa.vic.gov.au/liquid-storage-and-handling-guidelines

NSW EPA – Bunding requirements at liquid waste treatment facilities
https://www.epa.nsw.gov.au/your-environment/waste/industrial-waste/hazardous-and-liquid-wastes/bunding-requirements-at-liquid-waste-treatment-facilities

EPA Tasmania – Bunding and Spill Management Guidelines (PDF)
https://epa.tas.gov.au/documents/bunding_and_spill_management_guidelines_dec_2015.pdf

Bund capacity, displacement & common mistakes

Bunding compliance is determined by usable liquid capacity, not just the physical size of the bunded area. * This is where many sites fall into non-compliance without realising it.

Bund capacity vs liquid volume

Bund capacity refers to the actual volume of liquid the bund can hold, not the gross internal dimensions of the bund walls.

What matters is:

• The net available volume, after accounting for displacement from items stored inside the bund

Any object inside the bund that occupies space reduces the volume available to hold spilled liquid.

Displacement explained

Consider a bund used to store one 200-litre drum:

• Compliance requirement (110% rule):
  220 litres minimum containment

However:

• The drum displaces volume inside the bund
• If the bund’s internal volume is exactly 220 litres before the drum is placed inside, it is non-compliant

Why?

• The drum occupies space
• The bund can no longer physically hold 220 litres of liquid

To be compliant, the bund must have sufficient extra capacity to account for both:

• The spill volume, and
• The displacement caused by the drum

Common bunding mistakes

The most frequent compliance issues include:

• Ignoring displacement from drums, pallets, or equipment
• Measuring wall height × floor area only
• Installing floor bunding without checking total volume
• Assuming manufacturer-stated capacity applies after loading
• Failing to reassess capacity when storage layouts change

Key takeaway

Bund capacity is about what the bund can actually hold during a spill, not what it looks like on paper.

If the required spill volume cannot be contained after displacement, the bund does not meet capacity requirements, regardless of intent.

Types of bunding systems

There are multiple types of bunding systems used for spill containment. Each is designed for different site conditions, storage methods, and risk levels. No single system is suitable for every application.

Bunded spill pallets

What they’re for
Self-contained bunded units designed to hold drums or IBCs above an integrated sump.

Pros

• Built-in, known containment capacity
• Quick to deploy with minimal setup
• Suitable for indoor and outdoor use
• Easy to relocate if site layouts change

Cons

• Limited to specific container sizes and quantities
• Not suitable for vehicle traffic
• Capacity is fixed and cannot be expanded

Rubber floor bunding

What it’s for:
Permanent or semi-permanent raised barriers installed on existing floors to create a bunded area.

Pros

• Low-profile and forklift-friendly
• Suitable for vehicle and foot traffic
• Can be retrofitted to existing slabs
• Clean, defined containment zones

Cons

• Requires correct installation and sealing
• Capacity depends on floor area and wall height
• Not easily reconfigured once installed

Flexible floor bunding

What it’s for:
Collapsible bunding that forms a temporary containment area on flat surfaces.

Pros

• Quick to deploy and remove
• Lightweight and portable
• Can be driven over when empty
• Minimal site preparation required

Cons

• Limited height and capacity
• Not suitable for permanent installations
• Requires careful setup to maintain seal integrity

Ideal applications

• Temporary worksites
• Short-term containment needs
• Low-volume spill risk areas

Portable bunding

What it’s for:
Relocatable bunds designed to provide temporary or semi-permanent spill containment.

Pros

• No permanent installation required
• Flexible sizing options
• Suitable for changing site layouts
• Can be reused across multiple locations

Cons

• Requires flat, stable surfaces
• Capacity may be lower than fixed systems
• Setup quality affects performance

Ideal applications

• Construction sites
• Temporary storage zones
• Mobile plant and maintenance activities

Temporary / emergency bunding

What it’s for:
Rapid-deployment systems used to contain spills during incidents or unplanned events.

Pros

• Fast response capability
• Complements spill kits
• Useful for emergency containment

Cons

• Not designed for long-term storage
• Limited capacity and durability
• Requires trained staff to deploy correctly

Ideal applications

• Spill response scenarios
• Equipment failure events
• Interim containment until permanent controls are in place

Installation, maintenance & inspection

Bunding must be correctly installed, regularly inspected, and maintained to remain compliant over time.

Installation

Bunding should be:

• Installed in line with manufacturer instructions
• Positioned on stable, level surfaces
• Properly sealed at joints, corners, and penetrations

Any gaps, cracks, or seal failures are treated as containment failures, regardless of capacity.

Inspection

Bunded areas should also be inspected:

• As part of routine site checks
• After spills or incidents
• Following layout changes or damage

Inspection frequency should reflect spill risk and site activity.

Rainwater and ongoing compliance

For outdoor bunding, rainwater must be managed without reducing available spill capacity, and contaminated water must not be discharged without approval.

A bund that was compliant at installation can become non-compliant over time due to layout changes, added containers, or poor housekeeping

The right Bund Solution for Your Requirements

Choosing bunding is a compliance and risk decision, not a space or cost decision. The correct solution depends on how liquids are stored, handled, and moved on site.

Key factors

• Indoor vs outdoor use
  Outdoor bunding must manage rainwater and runoff. Indoor bunding must contain spills without relying on drainage.
• Vehicle and equipment traffic
  Areas with forklifts or mobile plant require low-profile or traffic-rated bunding. Static storage areas do not.
• Temporary vs permanent operations
  Temporary activities may suit portable systems. Permanent storage typically requires fixed or engineered bunding.
• Chemical compatibility
  Bunding materials must be compatible with the liquids stored. Material failure is treated as non-compliance.
• Compliance risk
  Higher volumes, hazardous liquids, proximity to drains, and regulatory scrutiny require more robust containment.

The right bunding solution meets capacity requirements, suits site conditions, and remains compliant over time.

If you’re unsure which bunding approach suits your site, get in touch with a bunding expert today.

FAQs