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 (publication 2001).

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.

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. 

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.

The injection of remedial chemicals must only be performed by suitably qualified professionals with specialist knowledge in groundwater cleanup methods and practices.

A detailed conceptual hydrogeological model (CHM) and conceptual site model (CSM), and detailed knowledge of the interactions between the remedial chemicals and the contamination is required to ensure that risks of harm are understood and able to be managed (minimised) during the injection of remedial chemicals. This will likely include numerical or analytical modelling to understand the hydrogeological system and contaminant movement, potential hydraulic effects of the remedial system and to inform the remedial design and specific monitoring requirements.

Prior to the injection of any remedial chemicals, assessment must be performed to gather information and understand:

• the hydrogeological setting and nature of contamination
• the remedial activity
• the risks of harm to human health and the environment, and risk controls
• monitoring requirements.

Details of these requirements are presented in Assessment requirements for injection of remedial chemicals to groundwater.

All applicable environmental values, and any existing groundwater uses, must be considered when developing measures to minimise risks of harm. The injection of remedial chemicals must result in a demonstrable reduced risk of harm to human health and the environment.

The assessment(s) outlined above must be documented. Documentation should be informed by (and incorporated where applicable) relevant aspects of the CHM and CSM, and provide a detailed description of the discharge activity. While not required to be provided to, or approved by EPA prior to undertaking remedial injections as outlined in this guidance, such documentation will be required to demonstrate compliance with this guideline and therefore must be available for EPA review if requested. Where the effect of the discharge extends beyond the site boundary, information must be provided to all relevant stakeholders (refer to obligations under section 39 of the Act) especially where those stakeholders could reasonably be affected by the discharge as this may affect their duties under the Act. Contaminated land policy (publication 1915) and Contaminated land: Understanding section 35 of the Environment Protection Act 2017 (publication 1940) provide further information regarding obligations under the Act. All stakeholder engagement should be documented.

Application of the guidelines

These guidelines apply from 26 October 2021.

Prior to the injection of any remedial chemicals, assessments must be performed to gather information and understand:

• the hydrogeological setting and nature of contamination
• the remedial activity
• the risks of harm to human health and the environment, and risk controls
• monitoring requirements.

Understanding the hydrogeological setting and nature of the contamination

Assessment requirement

Existing knowledge of the problem, including a remedial action plan or equivalent, including:

• the type, magnitude extent and mass (if practicable) of the contaminants of concern
• the phase of contaminants (aqueous, non-aqueous, sorbed, etc.)
• conceptual hydrogeographical model and conceptual site model,  including pathways and receptors
• numerical an / or analytical models of the hydrogeological system and contaminant migration.

Guidance / reference

Hydrogeological assessment (groundwater quality) guidelines (publication 668)

Guidance for the cleanup and management of contaminated groundwater (publication 2001)

 

 

Understanding the remedial activity

Assessment requirement

• The types, concentrations and volumes of chemicals to be discharged, and the source / quality of water (where water-borne chemicals are used).
• Calculations of the mass of contaminants versus the mass of remedial chemical (or equivalent) required to achieve the remedial goals (including consideration of stoichiometry of remedial chemical reactions with the contaminants).
• The location(s) of discharge, delivery methods (for example, single point bores, bore fields / arrays, infiltration galleries, horizontal bores, injection of permeable reactive barrier etc.) and area likely to be affected by the discharge.
• The expected reaction(s) with the target contaminant, including description of any daughter products generated and toxicity of those products. Where previous remedial injections have been undertaken, consider additive effects and / or adverse reactions (especially where the chemical injected has changed).
• Any reference material, or outcomes of bench trials used in confirming applicability of the chemical for remediation at the site.
• Whether the use of the chemical will inhibit other methods of remediation if required in the future (for example, will it cause aquifer clogging or reduce biological activity).
• The potential for rebound effects and the timescale likely to elapse before such effects may occur (or after which are unlikely to occur) to inform post-remediation actions / monitoring.

Guidance / reference

Thesis remedial activity details will be captured in the remedial action plan (or equivalent).

Guidance for the cleanup and management of contaminated groundwater (publication 2001)

 

 

Understanding the risks of harm to human health and the environment and risk controls

Assessment requirement

• Health and safety information such as material safety data sheet (MSDS) from the chemical provider / manufacturer.
• Short- and / or long-term displacement effects on groundwater, such as mounding, changes in flow direction.
• Short- and / or long-term geochemical changes in soil and groundwater and their likely effect on environmental values or land use.
• Potential for detriment to any environmental values of land, groundwater, surface waters or air (including vapour) beyond the boundary of the premises, as a result the injection.
• Potential for detriment to any existing use of land, groundwater, surface waters or air beyond the boundary of the premises, as a result the injection.
• Change of vapour risk profile, fugitive emission or accumulation of explosive gases, for example, methane during the remediation process.
• The proposed contingency measures should unexpected adverse results / outcomes occur.

Guidance / reference

General environmental duty - a person who is engaging in an activity that may give rise to risks of harm to human health or the environment from pollution or waste must minimise those risks so far as is reasonably practicable.

Environment Reference Standard and the Guide to the Environment Reference Standard (publication 1992)

Hydrogeological assessment (groundwater quality) guidelines (publication 668)

National Environment Protection (Assessment of Site Contamination) Measure, 1999, Volume 3, Schedule B2, Section 10 – Contaminant fate and transport modelling. 

National Environment Protection (Assessment of Site Contamination) Measure, 1999, Volume 5, Schedule B4, Site Specific Health Risk Assessment Methodology. 

National Environment Protection (Assessment of Site Contamination) Measure, 1999, Volume 6, Schedule B5a, Ecological Risk Assessment.

 

 

Understanding monitoring requirements

Assessment requirement

• Specific pre-, during and post-discharge monitoring requirements, mitigation measures and contingency actions.
• Requirements should consider groundwater and / or vapour and / or gas monitoring.
• Indicators to measure the remedial success, or conversely, indicate that the remedial method has not achieved, or is unlikely to achieve the remedial goals.

Guidance / reference 

Context: to ensure that the injection process and effects are consistent with what was planned and to ensure risks of harm are captured.

Other documentation

Assessment requirement

• Tabulation of activities including timing between discharge events (if relevant), the period over which the discharge will occur (including any pilot trials).
• Documentation of previous injections / remedial activities (where applicable).
• Stakeholder engagement activities.

Guidance / reference

Contaminated land: understanding section 35 of the Environment Protection Act 2017 (publication 1940).