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.
Assessment requirements for injection of remedial chemicals to groundwater
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).
Updated