2.3.5.2 Hazard analysis


Hazard analysis is a critical part of the BA as it rigorously and systematically identifies the potential impacts (hazards) on water-dependent assets arising from whole-of-life-cycle CSG and coal mine activities. Only hazards identified through this process are considered further in a BA.

A hazard analysis conducted for the Galilee subregion (Bioregional Assessment Programme, Dataset 1) was based on the proposed CSG operations and coal mines (as outlined Section 2.3.4.1) and their water management (Section 2.3.4.2). The hazard analysis for the Galilee subregion was completed during a one-day workshop in March 2015 with experts from CSIRO, Geoscience Australia and the Department of the Environment.

2.3.5.2.1 Coal seam gas operations

The hazard analysis identified some 260 activities associated with CSG projects. However, not all of the activities listed were applicable to the Galilee subregion or had potential to impact water. Further information on hazards that are within scope for the Assessment is outlined in Section 2.3.5.2.3.

The hazard scores from the IMEA help to pinpoint what would potentially be the more serious hazards. The top 30 hazards and their associated activities and impact modes are outlined in Figure 30 and identify the following potential effects to aquifers including:

  • hydrostatic depressurisation of the aquifer (target coal seam and non-target aquifers)
  • fault-mediated depressurisation caused by faults opening or closing due to CSG operations
  • aquitard-mediated depressurisation (i.e. an aquitard is absent or the integrity of the aquitard is compromised in some parts of the subregion)
  • connection of previously disconnected aquifers by hydraulic fracturing, incomplete casing of wells or incomplete seal integrity
  • disruption to natural surface drainage.

After impacts on aquifers, the potential impacts associated with storage, processing and disposal of treated water were all identified as potentially important in this context.

Although a number of hazards have been identified, hazards for CSG operations were not included in groundwater and surface water modelling undertaken for the CRDP (Section 2.3.4.1) as the potential for development of CSG projects to full production in the Galilee subregion may be still be some years into the future.

Figure 30

Figure 30 Highest ranked hazards (and their associated activities and impact modes) for coal seam gas operations, ranked by midpoint of the hazard priority number

The x-axis shows the hazard priority number and hazard score for potential hazards. The intervals between the highest and lowest hazard priority number are shown in dark blue; the intervals for hazard score are shown in light blue. The same hazard may appear multiple times, as it may arise from a number of different life-cycle stages and activities. Hazards are listed with the syntax [Life‑cycle stage][Activity]:[Impact mode], where life-cycle stages are indicated by (E) for exploration and appraisal, (C) for construction, (P) for production and (D) for decommissioning.

Typology and punctuation are consistent with Dataset 1.

Data: Bioregional Assessment Programme (Dataset 1)

2.3.5.2.2 Open-cut and underground coal mines


The hazard analysis identified some 274 activities associated with open-cut and underground mines. However, not all of the activities listed were applicable to the Galilee subregion or had potential to impact water. Further information on hazards that are within scope for the Assessment is outlined in Section 2.3.5.2.3.

The hazard priority number scores from IMEA help to pinpoint what would potentially be the more serious hazards. The top 30 hazards and their associated activities and impact modes are outlined in Figure 31. Issues associated with underground longwall mining such as fracturing and subsidence and disruption to surface drainage were some of the highest ranked hazards.

The potential impacts of leaching is associated with 8 of the 30 highest ranked hazards, including leaching from:

  • in-pit waste rock dumps and backfill
  • waste rock dumps outside of the pit
  • coal stockpiles (in and out of the pit)
  • run-of-mine (ROM) plants
  • tailings decant water dams.

Leaching ranks fairly high due to difficulties in detecting whether leaching of mine or coal-related materials is taking place and if leachate changed quality of the nearby groundwater.

The following are identified as having the potential to link, or cause leakage between, aquifers:

  • incomplete or compromised cementing of groundwater supply and monitoring bores
  • mine expansion too close to a water body
  • abandoned exploration and appraisal bores.

These – together with dewatering and enhanced aquifer interconnectivity caused by post-closure water filling the open-cut and underground mine workings – are identified as potentially important hazards. The remaining 30 highest ranked hazards include:

  • soil erosion caused by heavy rainfall or failure to successfully rehabilitate abandoned mines
  • artificial groundwater recharge (following pit abandonment).

Figure 31

Figure 31 Highest ranked hazards (and their associated activities and impact modes) for coal operations, ranked by midpoint of the hazard priority number

The x-axis shows the hazard priority number and hazard score for potential hazards. The intervals between the highest and lowest hazard priority number are shown in dark blue; the intervals for hazard score are shown in light blue. The same hazard may appear multiple times, as it may arise from a number of different life-cycle stages and activities. Hazards are listed with the syntax [Life‑cycle stage][Activity]:[Impact mode], where life-cycle stages are indicated by (E) for exploration and appraisal, (C) for construction, (P) for production and (D) for decommissioning.

Typology and punctuation are consistent with Dataset 1.

Data: Bioregional Assessment Programme (Dataset 1)

2.3.5.2.3 Hazard handling and scope

A full list of hazards (Bioregional Assessment Programme, Dataset 1) has been generated for both CSG operations and coal mines, as described in Section 2.3.5.2.1 and Section 2.3.5.2.2 This section describes the scope of subsequent work, which addresses only a subset of the full list of hazards.

The hazards of primary focus from a BA perspective are those that extend beyond the development site and that may have cumulative impacts, as these are consistent with the regional focus of BA, and are where BAs will add greater value beyond site-specific environmental impact statements (EIS). Ultimately, however, BAs need to be able to address all identified hazards by considering the scope, modelling, other literature or narratives, and specifying where science gaps may exist.

BAs are constrained by considering only impacts that can happen via water, and so hazards such as dust, fire or noise are deemed out of scope and are addressed by site-based risk management unless there is a water-mediated pathway.

Leading practice is assumed and accidents are deemed to be covered adequately by site-based risk management procedures and are beyond the scope of BA; for example, the failure of a pipeline is covered by site-based risk management.

Hazards that pertain to the development site and with no off-site impacts are important to acknowledge but will typically be addressed by site-based risk management procedures.

For CSG operations, the following hazards are considered out of scope in the Galilee subregion because they are deemed to be covered by site-based risk management and regulation:

  • abandonment practice
  • hazards addressed by site management, no water-mediated pathway (dust, fire or noise)
  • containment failure due to poor construction or design
  • equipment/infrastructure failure (e.g. pipeline failures)
  • leaching/leaking from storage ponds and stockpiles
  • spillages and disposals (diesel, mud, cuttings, fluid recovery)
  • vegetation clearance and subsequent soil erosion following heavy rainfall.

Hydrological effects associated with CSG operations that are considered to be in scope are detailed in companion submethodology M05 (as listed in Table 1) for developing a conceptual model of causal pathways (Henderson et al., 2016) and listed below:

  • surface water quality
  • surface water direction
  • surface water flow
  • aquifer properties
  • groundwater composition
  • groundwater flow (reduction)
  • groundwater level
  • groundwater pressure.

The hydrological effect of an activity such as ‘water and gas extraction’ depends on the impact cause and impact mode. For example, ‘depressurisation’ (impact cause) that causes ‘subsidence’ (impact mode) affects ‘surface water direction’ (hydrological effect) and ‘aquitard leaks’ (impact cause) that cause ‘non-target, non-reservoir aquifer depressurisation’ (impact mode) affects ‘groundwater pressure’ (hydrological effect)

Activities, impact modes and hydrological effects are assigned to a specific series of causal pathways (Table 13, Table 14). A causal pathway describes the logical chain of events – planned or unplanned– that link coal resource development to changes in groundwater or surface water, and then to impacts on water-dependent assets. The various combinations of activities, impact modes and effects have common themes relating to causal pathways. Hence causal pathways can be grouped further into four main causal pathway groups (Table 13, Table 14). The companion submethodology M05 (as listed in Table 1) for developing a conceptual model of causal pathways (Henderson et al., 2016) provides further detail on causal pathways and causal pathway groups that were utilised for BAs.

CSG projects are included in the CRDP but have not been modelled (Section 2.3.4.1). Although cumulative hazards and potential causal pathways by CSG operations are recognised (as noted in Section 2.3.4.1), the timing and nature of future CSG production (beyond small-scale pilot operations) is currently unknown, but unlikely to occur within the next 10 to 15 years.

Table 13 Top 30 coal seam gas (CSG) activities, associated impact modes and causal pathway groups for the Galilee subregion


Component

Life cycle

Activity

Impact mode

Hydrological effect

Causal pathway group

Causal pathway

Wells

C

Hydraulic fracturing

Connecting aquifers

GW composition, GW quality

Subsurface physical flow paths

Hydraulic fracturing

Wells

C

Cementing and casing

Incomplete/compromised cementing/casing (linking aquifers)

GW quality

Subsurface physical flow paths

Failure of well integrity

Wells

C

Cementing and casing

Incomplete/compromised cementing/casing (gas leak)

GW quality

Subsurface physical flow paths

Failure of well integrity

Wells

C

Hydraulic fracturing

Contaminate target aquifer (chemical)

GW quality

Subsurface physical flow paths

Hydraulic fracturing

Wells

C

Hydraulic fracturing

Changing target aquifer properties (physical or chemical)

Aquifer properties

Subsurface physical flow paths

Hydraulic fracturing

Wells

C

Groundwater monitoring bore construction

Incomplete/compromised cementing/casing (linking aquifers)

GW composition, GW quality

Subsurface physical flow paths

Failure of well integrity

Wells

C

Drill cutting disposal

Groundwater and/or surface water contamination

SW quality, GW quality

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Wells

C

Hydraulic fracturing

Contaminate non-target aquifer (chemical)

GW quality

Subsurface physical flow paths

Hydraulic fracturing

Wells

D

Pressure concrete durability

Seal integrity loss

GW quality

Subsurface physical flow paths

Failure of well integrity

Wells

E

Abandonment

Bore leakage between aquifers

GW composition, GW quality

Subsurface physical flow paths

Failure of well integrity

Wells

E

Abandonment

Bore leakage to surface

SW quality

Subsurface physical flow paths

Failure of well integrity

Wells

P

Groundwater monitoring bore construction or expansion

Incomplete/compromised cementing/casing (linking aquifers)

GW composition, GW quality

Subsurface physical flow paths

Failure of well integrity

Wells

P

Water and gas extraction

Aquifer depressurisation (coal seam)

GW pressure

Subsurface depressurisation and dewatering

Groundwater pumping enabling coal seam gas extraction

Wells

P

Water and gas extraction

Aquifer depressurisation (non-target, non-reservoir)

GW pressure

Subsurface depressurisation and dewatering

Unplanned groundwater changes in non-target aquifers

Wells

P

Water and gas extraction

Aquifer depressurisation (aquitard-absent)

GW pressure

Subsurface depressurisation and dewatering

Unplanned groundwater changes in non-target aquifers

Wells

P

Water and gas extraction

Aquifer depressurisation

GW flow (reduction)

Subsurface depressurisation and dewatering

Unplanned groundwater changes in non-target aquifers

Wells

P

Water and gas extraction

Aquifer depressurisation (fault mediated)

GW pressure

Subsurface depressurisation and dewatering

Unplanned groundwater changes in non-target aquifers

Wells

C

Waste disposal

Groundwater and/or surface water contamination

SW quality, GW quality

No specific causal pathway in bioregional assessments

Addressed by site-based risk management procedures

Roads and infrastructure

C

Construction of access roads and easements (e.g. for drilling rigs and equipment)

Soil erosion following heavy rainfall

SW quality

Surface water drainage

Altering surface water system

Processing facilities

C

Hypersaline brine ponds

Disruption of natural surface drainage

SW volume, SW quality

Surface water drainage

Altering surface water system

Processing facilities

C

Gas processing plant

Disruption of natural surface drainage

SW volume, SW quality

Surface water drainage

Altering surface water system

Processing facilities

C

Gas-gathering pipeline networks

Disruption of natural surface drainage

SW volume, SW quality

Surface water drainage

Altering surface water system

Processing facilities

C

Brine storage ponds, pumps and water disposal pipelines

Disruption of natural surface drainage

Surface water flow

Surface water drainage

Intercepting surface water runoff

Processing facilities

C

Treated water pond

Disruption of natural surface drainage

Surface water flow

Surface water drainage

Altering surface water system

Processing facilities

C

Water treatment plant (RO, fixed resin, fixed disc, electrochemical etc.)

Disruption of natural surface drainage

SW volume, SW quality

Surface water drainage

Altering surface water system

Processing facilities

P

Untreated co-produced water storage, processing and disposal (pilot stage only)

Leaching from storage ponds

GW quality

Operational water management

Storing extracted water

Processing facilities

P

Hypersaline brine ponds

Leaking

SW quality, GW quality

Operational water management

Storing extracted water

Processing facilities

P

Brine storage ponds, pumps and water disposal pipelines

Leaking

SW quality, GW quality

Operational water management

Storing extracted water

Pipelines facilities

C

Trunk gas pipelines and associated easements (processing plant to town)

Disruption of natural surface drainage

SW volume, SW quality, GW quantity

Surface water drainage

Intercepting surface water runoff

Pipelines facilities

C

Trunk gas pipelines and associated easements (processing plant to town)

Soil erosion following heavy rainfall

SW quality

Surface water drainage

Altering surface water system

aLife-cycle stages are indicated by (C) for construction, (E) for exploration and appraisal, (P) for production, (D) for decommissioning and (W) for work-over.

bTable rows are ordered according to component and life cycle.

GW = groundwater, SW = surface water, RO = reverse osmosis

The full list of identified hazards is available from Bioregional Assessment Programme (Dataset 1). Typology and punctuation are consistent with this dataset.

Data: Bioregional Assessment Programme (Dataset 1)

For open-cut and underground coal mines, the following hazards are considered out of scope for the Galilee subregion because they are deemed to be covered by site-based risk management and regulation and do not have cumulative effects on water in the subregion:

  • addressed by site management, no water-mediated pathway (dust, fire or noise)
  • bore and well construction (integrity, leakage)
  • disruption of surface drainage network for site-based infrastructure, plant and facilities, roads, creek crossings
  • equipment/infrastructure failure (e.g. pipeline failures, plant failures)
  • leaching/leaking from storage ponds and stockpiles
  • loss of containment (due to construction or design, slope failure)
  • re-contouring, compaction and settlement following backfill
  • spillages and disposals (diesel, mud, cuttings, fluid recovery)
  • vegetation clearance and subsequent soil erosion following heavy rainfall.

Of those hazards that are in scope, some will be addressed by the BA numerical modelling, while for others (e.g. water quality hazards) it will only be possible through informed narrative. In the full list of hazards (Bioregional Assessment Programme, Dataset 1), the hazard priority number or hazard score indicates the relative importance of the hazard. Hazards with low scores are of lower priority.

Hydrological effects associated with coal mines that are considered to be in scope for the Galilee subregion are listed below:

  • surface water quality
  • surface water direction
  • surface water flow
  • surface water volume
  • change to zero flow days
  • groundwater quality
  • groundwater direction
  • groundwater flow (reduction)
  • groundwater quantity/volume
  • groundwater pressure.

Activities, impact modes and hydrological effects for open-cut and underground coal mines are assigned to causal pathways that can be aggregated into causal pathway groups (Table 14). The companion submethodology M05 (as listed in Table 1) for developing a coal resource development pathway (Henderson et al., 2016) provides further detail on causal pathways and their groupings that were utilised for BAs.

Table 14 Top 30 open-cut and underground mine activities, associated impact modes and causal pathway groups for the Galilee subregion


Component

Life cycle

Activities

Impact mode

Hydrological effects

Causal pathway group

Causal pathway

Open pit

D

Post-closure water filling the pit

Artificial point of recharge

GW quantity/volume, GW quality

Surface water drainage

Altering surface water systems

Open pit

D

Post-closure water filling the pit

Creation of artificial lake

SW quality

Surface water drainage

Altering surface water systems

Open pit

D

Pit backfill

Compaction/settlement

SW directional characteristics, GW directional characteristics

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Open pit

D

Waste rock blasting, excavation and storage

Leaching: waste storage

GW quality, SW quality

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Open pit

D

Rainwater runoff diversion

Change to natural surface drainage

SW volume/quantity, SW quality, GW quantity/volume

Surface water drainage

Intercepting surface water runoff

Open pit

D

Waste rock blasting, excavation and storage

Disruption of natural surface drainage

SW directional characteristics, SW volume/quantity, SW quality, GW directional characteristics, GW quantity/volume, GW quality

Surface water drainage

Altering surface water systems

Open pit

D

Dam construction for tailings storage

Soil erosion following heavy rainfall

SW quality

Surface water drainage

Altering surface water systems

Open pit

D

Dam construction for mine water storage

Soil erosion following heavy rainfall

SW quality

Surface water drainage

Altering surface water systems

Open pit

D

Topsoil and waste rock dump site preparation

Disruption of natural surface drainage

SW volume/quantity, SW quality, GW quantity/volume

Surface water drainage

Altering surface water systems

Open pit

P

Waste rock blasting, excavation and storage

Disruption of natural surface drainage

SW directional characteristics, SW volume/quantity, SW quality, GW directional characteristics, GW quantity/volume, GW quality

Surface water drainage

Altering surface water systems

Open pit

P

Pit backfill

Leaching: in-pit waste rock dump

GW quality

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Open pit

P

Waste rock blasting, excavation and storage

Leaching: waste storage

GW quality, SW quality

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Open pit

P

Pit wall (stabilisation) dewatering, treatment, reuse, and disposal

Deliberate

GW flow, GW directional characteristics, GW quantity/volume, GW pressure, SW flow

Subsurface depressurisation and dewatering

Groundwater pumping enabling open-cut coal mining

Open pit

P

Coal onsite transport: stockpiles

Leaching

GW quality, SW quality

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Open pit

P

Topsoil excavation and storage

Runoff changes

GW quantity/volume (changed recharge), SW flow

Surface water drainage

Altering surface water systems

Open pit

P

Waste rock dump rehabilitation

Leaching

GW quality, SW quality

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Surface facilities

P

Run-of-mine plants

Leaching

GW quality, SW quality

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Surface facilities

P

Product coal stockpiling

Leaching

GW quality, SW quality

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Underground mining

D

Development of mine panels (construction of roadways)

GW dewatering

GW level

Subsurface depressurisation and dewatering

Groundwater pumping enabling underground coal mining

Underground mining

D

Waste rock removal and storage during construction of mine access (adit/shaft/incline)

Leaching

GW quality, SW quality

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Underground mining

D

Groundwater monitoring bore construction

Incomplete/compromised cementing/casing (linking aquifers)

GW composition, GW quality

No specific causal pathway in BAs

Addressed by site-based risk management procedures

Underground mining

P

Longwall coal extraction

Subsurface fractures

GW pressure, GW flow, GW quality, GW quantity/volume, SW flow, SW volume/quantity

Subsurface physical flow paths

Subsurface fracturing above underground longwall panels

Underground mining

P

Longwall coal extraction

Subsidence

SW directional characteristics

Surface water drainage

Subsidence of land surface

Underground mining

P

Longwall coal extraction

GW dewatering

GW level

Subsurface depressurisation and dewatering

Groundwater pumping enabling underground coal mining

Underground mining

P

Subsidence management and monitoring

Poor management and monitoring

SW flow, SW directional characteristics, SW quality, GW flow, GW level, GW directional characteristics

Surface water drainage

Subsidence of land surface

Underground mining

P

Longwall coal extraction

Subsidence

GW quantity/volume, GW quantity/volume (changed recharge), GW connectivity

Surface water drainage

Subsidence of land surface

aLife-cycle stages are indicated by (C) for construction, (E) for exploration and appraisal, (P) for production and (D) for decommissioning.

bTable rows are ordered according to component and life cycle.

BA = bioregional assessment, GW = groundwater, SW = surface water

The full list of identified hazards is included in Bioregional Assessment Programme (Dataset 1). Typology and punctuation are consistent with this dataset.

Data: Bioregional Assessment Programme (Dataset 1)

Last updated:
17 December 2018