Breadcrumb

Systematic analysis of water-related hazards associated with coal resource development

Executive summary

This submethodology describes how to apply a type of hazard analysis in bioregional assessments (BAs). The hazard analysis presented here is based on the Failure Modes and Effects Analysis (FMEA) methodology that has been successfully applied to complex industrial systems for many decades. In BAs, it is referred to as Impact Modes and Effects Analysis (IMEA) to recognise that many of the hazards associated with coal resource development do not arise through system failures.

IMEA is a systematic and rigorous technique for identifying and ranking hazards associated with whole-of-life-cycle CSG operations and coal mines. A hazard is an event, or chain of events, that might result in an effect (change in the quality and/or quantity of surface water or groundwater). In turn, an impact (consequence) is a change resulting from prior events, at any stage in a chain of events or a causal pathway (the logical chain of events ‒ either planned or unplanned ‒ that link coal resource development and potential impacts on water and water-dependent assets). An impact might be equivalent to an effect, or it might be a change resulting from those effects (for example, ecological changes that result from hydrological changes).

Using IMEA, the hazards are firstly identified for all the activities (impact causes) and components in each of the five life-cycle stages. For CSG operations the stages are exploration and appraisal, construction, production, work-over and decommissioning. For coal mines the stages are exploration and appraisal, development, production, closure and rehabilitation. The hazards are scored on the following basis, defined specifically for the purposes of the IMEA:

  • severity score: the magnitude of the impact resulting from a hazard, which is scored so that an increase (or decrease) in score indicates an increase (or decrease) in the magnitude of the impact
  • likelihood score: the annual probability of a hazard occurring, which is scored so that a one-unit increase (or decrease) in score indicates a ten-fold increase (or decrease) in the probability of occurrence
  • detection score: the expected time to discover a hazard, scored in such a way that a one-unit increase (or decrease) in score indicates a ten-fold increase (or decrease) in the expected time (measured in days) to discover it.

Impact modes and stressors are identified as they will help to define the causal pathways in Component 2: Model-data analysis. An impact mode is the manner in which a hazardous chain of events (initiated by an impact cause) could result in an effect (change in the quality or quantity of surface water or groundwater). There might be multiple impact modes for each activity or chain of events. A stressor is a chemical or biological agent, environmental condition or external stimulus that might contribute to an impact mode.

The hazard analysis reflects the conceptual models and beliefs that domain experts hold about the ways in which coal resource development might impact surface water and groundwater, and the relative importance of these potential impacts. As a result, the analysis enables these beliefs and conceptual models to be made transparent. It is important to emphasise, however, that even if a hazard is identified as possibly occurring, it does not mean that it will definitely happen.

A case study for the Gloucester subregion is presented as an illustration of how to apply this method to coal resource development. A large number of hazards are identified but some of these are beyond the scope of BA, such as accidents, or are adequately addressed by site-based risk management processes and regulation. While individual chains of events or hazards constitute causal pathways, many of these hazards group naturally by common cause and mode of impact and are represented by a smaller number of aggregated causal pathways for consideration in the BA.

In the Gloucester subregion, coal resource development includes CSG operations and open-cut mines. CSG operations have their immediate impact below ground, with aquifer depressurisation, enhanced inter-aquifer connectivity, and the storage and disposal of co-produced water the main impact modes. Open-cut mines most directly affect surface water flows and aquifers, with disruption of natural surface drainage, inter-aquifer connectivity, and the storage and disposal of water the main impact modes.

Results from hazard analyses (such as for Gloucester subregion) complete the understanding of the causal pathways and priority impacts associated with coal resource development, when the results are combined with:

  • results from surface water modelling and groundwater modelling, which determine the predicted maximum spatial extent of hydrological changes
  • the list of landscape classes that are subsequently impacted
  • the list of assets within these landscapes classes.

The hazard analysis is reported in product 2.3 (conceptual modelling). In addition, the full output of the hazard analysis for each subregion or bioregion is registered as a dataset and cited in product 2.3 (conceptual modelling), to ensure transparency with respect to the underpinning results.

The hazard analysis is an important precursor to the impact and risk analysis. A full risk assessment is outside the scope of a BA; instead, a BA identifies and analyses risks, then others can use these for their own full risk assessment.

Last updated:
11 July 2017