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.