Discharge or deposit of waste to aquifer

Purpose

Under the Environment Protection Regulations 2021 (the Regulations), the discharge or deposit of waste to an aquifer is a 'prescribed permit activity' which requires a permit under the Environment Protection Act 2017 (the Act).

However, an exception applies to the 'injection of water or remediation chemicals which is undertaken for the remediation of groundwater in an aquifer in accordance with relevant guidelines published or approved by [EPA]'.

The following guidelines are published by EPA for the purpose of providing guidance to persons who intend to inject water or remediation chemicals to an aquifer pursuant to this exception, without the requirement to hold a permit. This guidance should be read in conjunction with Guidance for the cleanup and management of contaminated groundwater.

Interpretation of guideline

For the purposes of these guidelines:

Aquifer means a geological structure or formation or an artificial land fill permeated or capable of being permeated permanently or intermittently with water.

Groundwater means any water contained in or occurring in a geological structure or formation or an artificial landfill below the surface of land.

Inject means to introduce a fluid or substance by force into a geological structure or formation. For the avoidance of doubt, it includes the placement of any substance or matter into a well or excavation.

Remediation of groundwater refers to the process of removing or changing the state of the groundwater to reduce or limit the effect of contamination that may pose a risk of harm to human health or the environment.

Scope of guidelines

These guidelines apply to the injection of water or remediation chemicals undertaken for the remediation of groundwater in an aquifer.

In accordance with the Environment Protection Act 2017 (the Act), a 'waste' includes 'matter, including solid, liquid, gaseous or radioactive matter, that is deposited, discharged, emitted or disposed of into the environment in a manner that alters the environment'. Accordingly, the injection of water or remediation chemicals for the remediation of groundwater in an aquifer would involve the discharge or deposit of 'waste' that would otherwise require a permit pursuant to section 46 of the Act.

The remediation of groundwater by way of injection of water or remedial chemicals may include:

• injection of any gaseous matter such as air, oxygen, carbon dioxide, steam, etc.
• injection of water or any water-borne chemical, for example nutrients to assist the growth of bacteria that degrade some contaminants
• injection of any liquid chemical, for example oxidation compound, reduction compound or other amendment
• injection of biological or bacterial mixtures
• extraction, treatment and re-injection of groundwater, for example pump and treat systems
• placement of any matter into a well or excavation, for example installing oxidation compound socks into a groundwater well, spreading of chemicals at the base of an excavation.

These guidelines do not affect the operation of other relevant laws with respect to groundwater. It is important to note that even where a permit is not required under the Act, a licence under section 76 of the Water Act 1989 (the Water Act) may still be required for the 'underground disposal of matter via a bore'. Further, bores constructed to inject or discharge chemicals may need to be licensed under section 67 of the Water Act, and any groundwater extracted may need to be licensed under section 51 of the Water Act.

Discharges or deposits of waste to an aquifer that are not for the purpose of remediation of groundwater will generally require a permit under the Act. Exception may apply for discharges undertaken in accordance with a licence issued under the Act, or where otherwise undertaken in accordance with the Greenhouse Gas Geological Sequestration Act 2008.

Relevance of guidelines to other duties and obligations under the Environment Protection Act 2017

The discharge or deposit of chemical substances to an aquifer, even for the purposes of cleanup or remediation, is an activity which may give rise to risks of harm to human health or the environment. As such, a person who is engaging in such activity must minimise those risks, so far as reasonably practicable, in accordance with the general environmental duty in section 25 of the Environment Protection Act 2017 (the Act).

It is expected that persons undertaking remediation of groundwater will know about the risks of harm arising from such activities. Some examples of risks of harm that may arise from groundwater remediation activities include:

• the generation of persistent daughter or intermediate products that are more toxic than the original contamination
• excess or unreacted remedial chemical itself posing a risk of harm
• unexpected reactions of remedial chemicals
• unexpected migration or displacement of contamination due to the injection method
• change in vapour risk profile or accumulation of explosive gases, for example methane during the remediation process.

To minimise these risks of harm, it is expected that all groundwater cleanup activities are undertaken by suitably qualified professionals with specialised knowledge in groundwater cleanup methodologies and practices. EPA has published guidance on how to work with consultants that may be helpful when engaging a qualified person to undertake cleanup.

Remediation of groundwater may also be undertaken in order to comply with other duties and obligations under the Act, including:

• the duty to take action to respond to harm caused by pollution in section 31 of the Act
• the duty to manage contaminated land in section 39 of the Act
• obligations arising out of a notice or direction given by EPA under the Act.