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Abandoned underground tanks

Abandoned underground tanks and associated pipework are potentially dangerous and can cause explosions if they have not been made safe.

When a workplace intends that an underground hazardous chemical storage and handling system will no longer be used, or disposed of, the person conducting a business or undertaking (PCBU) must ensure, so far as is reasonably practicable, that the system is removed. If it is not reasonably practicable to remove the system, the PCBU must ensure, so far as is reasonably practicable that the system is without risks to health and safety (section 366 of the Work Health and Safety Regulation 2011).

An underground, partially underground, or fully mounded tank used to store flammable gases or flammable liquids, that is not used for two years or is not intended to be used again (section 367 of the Work Health and Safety Regulation 2011), is considered an 'abandoned tank'.

You must notify the work health and safety regulator as soon as practicable after the abandonment using Form 72 – Notification of an abandoned tank (PDF, 0.16 MB).

Hazards

Abandoned underground fuel tanks can pose significant work and public safety risks and are commonly associated with current or past:

  • service stations
  • kerbside fuel dispensing sites
  • industrial premises
  • transport or fuel depots
  • airports.

Business operators or landowners are often unaware of the presence of abandoned underground fuel tanks or incorrectly assume tanks have been made safe. Some abandoned tanks are found during excavation work decades after being abandoned highlighting the need for tank documentation to be shared between successive owners and suitable exploratory and risk management practices prior to and during excavation.

Work on or around abandoned underground tanks or associated pipework is potentially dangerous due to the likely presence of residual:

  • flammable gases
  • liquids
  • vapours.

Introducing an ignition source (e.g. activities such as grinding, hot cutting or welding), excavating around or disturbing abandoned underground tanks may cause an explosion or other dangerous occurrence.

Tar-like deposits and sludge may have accumulated in the tank and pipe work. Flushing with water may not remove them and vapour testing may not detect this. Exposure of these deposits to air and sunlight under normal temperatures, or work involving heat (e.g. use of grinders or oxy-acetylene cutting), may release vapours creating a potential explosion risk.

It may not be practicable to remove an underground tank due to its close proximity to surrounding structures or underground infrastructure (e.g. building foundations or underground pipework). In such cases, the tank may need to be decommissioned 'in-situ' meaning the tank is left in its existing position and made safe.

Who is responsible?

The PCBU at the workplace who intends that the system no longer be used for the use, handling or storage of hazardous chemicals underground, or intends the system be disposed of, is responsible for the abandonment.

At locations other than a workplace, the occupier of the premises (e.g. property owner, mortgagee in possession, lessee) where the 'dangerous goods' are stored or handled will be responsible for the abandonment. In some instances, more than one person may have duties in respect of an abandoned underground tank.

Notification

When a PCBU has an abandoned underground tank that has been used for storage of flammable liquids, Categories 1-4, (e.g. petrol, resins, ethanol, diesel) or flammable gases (e.g. LP gas), the regulator must be notified as soon as practicable after the tank is abandoned using Form 72 – Notification of an abandoned tank (PDF, 0.16 MB) (section 367 of the Work Health and Safety Regulation 2011). A Form 72 notification must be provided to the regulator with supporting evidence confirming how an abandoned tank has been made safe.

Why do I have to notify?

Notification is to ensure the abandoned underground fuel tanks are made known to the regulator and tanks are made safe in accordance with AS4976: The removal and disposal of underground petroleum storage tanks, or other relevant standard.

Ensuring underground storage and handling systems are safe

A duty holder responsible for an abandoned tank must make the tank safe in accordance with section 366 of the Work Health and Safety Regulation 2011. The application of section 366 also extends beyond abandoned tanks to encompass disused underground systems used at a workplace for the use, handling or storage of hazardous chemicals.

Duty holders for abandoned tanks and disused underground storage and handling systems should be mindful that steps to comply with section 366 must be undertaken in a timely fashion and safety must be maintained while risks are present (if necessary, through the implementation of interim risk controls). Duty holders should not delay or defer steps to eliminate or mitigate risks due to operational or administrative convenience or factors such as the pending sale or redevelopment of premises. The following steps detail how a duty holder can demonstrate compliance with section 366 of the Work Health and Safety Regulation 2011.

Removal

If the abandoned tank was removed, you must provide:

  • a copy of the letter or certificate from a competent person confirming the method of removal was in accordance with AS4976 for flammable or combustible liquids, or other relevant standard. For example, AS1596 for LP gas with confirmation of the tank's gas-free status, or
  • a statement from a competent person confirming the method of removal offered an equivalent or higher standard of work health and safety to the relevant standard, and
  • a statement from a competent person (e.g. engineer) stating that the affected area is suitably stable post removal.

Decommissioning

If removal of the abandoned tank was not reasonably practicable, you must provide:

  • an explanation of why it was not reasonably practicable to remove the tank
  • a copy of the letter or certificate from a competent person confirming the method of decommissioning in situ was in accordance with AS4976 for flammable or combustible liquids, or other relevant standard. For example, AS1596 for LP gas with confirmation of the tank's gas-free status, or
  • a statement from a competent person confirming the method of decommissioning offered an equivalent or higher standard of work health and safety to the relevant standard, and
  • an amended site sketch/plan that identifies the position of the abandoned tank. Suitable dimensions must be included to clearly identify the position and footprint of the abandoned tank relative to a permanent reference point on the site.

Risk management

If decommissioning in situ was not reasonably practicable to ensure a tank is without risks to health and safety, you must provide:

Where a tank risk management approach is applied, and the capacity of one or more tanks exceeds a relevant manifest quantity, the site is treated as a manifest quantity workplace (MQW) and the duty holder for the tank/s needs to comply with MQW-related duties. For example, manifest and emergency plan notification, Hazmat box and risk management duties would apply. Where applicable, the duty holder must ensure amendments to relevant documents such as the manifest and site plan. Sites not considered an MQW would need to develop an emergency plan as required under section 43 of the WHS Regulation and be subject to relevant hazardous chemical requirements under WHS Regulation Part 7.1.

If it is intended that the underground tank be used again (within two years), an option may be to fill the tank with water and a corrosion inhibitor and conduct appropriate maintenance to maintain the system's integrity. Testing the tank's integrity is recommended before returning the tank to service.

If there is a change of duty holders, the outgoing duty holder should support ongoing work and public health and safety by providing the subsequent duty holder with information and documentation about abandoned tanks and underground hazardous chemical storage and handling systems.

More information

More information on the removal and disposal of underground tanks is available in Australian Standards, for example AS4976: The removal and disposal of underground petroleum storage tanks.

This standard also provides guidance for managing a tank that is temporarily out-of-service.

Managing risks of hazardous chemicals Code of Practice 2013 (PDF, 1.46 MB) provides information on abandoning or removing underground tanks.