Assessment requirements for injection of chemicals into groundwater

• 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).