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.