The main focus of this product is on quantitatively evaluating the potential impacts and risks due to the development of the seven large-scale coal mines in the central-eastern Galilee subregion. These proposed mines all occur within the surface water basin of the Belyando River and its main tributaries, which are headwater catchments of the larger Burdekin river basin (Figure 12). Consequently, all of the modelled hydrological changes from coal mining activity that potentially cause impacts to water resources and water-dependent assets are restricted to a relatively small part (less than 3% of the total area) of the much larger Galilee assessment extent.
In comparison to the modelled coal mining projects, most of the Galilee subregion coal resource developments that are the focus of the qualitative analysis are outside of the Belyando river basin. There are three main geographic areas of the Galilee subregion where these non-modelled coal resource developments occur:
- Northern Galilee – five potential coal mining projects are situated along the northern margin of the Galilee Basin, spread over an approximately 140 km long corridor to the north and north-east of Hughenden. All of these coal resources are over 100 km north-west from the nearest mine which is modelled in this BA (i.e. the Hyde Park Coal Project)
- Central Galilee – along with one potential new underground coal mine (Alpha West) within the central-eastern Galilee mining fairway, this area also has the three CSG projects that are in the CRDP (see Section 3.6.2)
- Southern Galilee – one potential new coal mine (Blackall) occurs in the southern Galilee Basin, targeting thermal coal resources of the Eromanga Basin, which is geologically younger than the Galilee Basin and overlies it across much of the subregion (Lewis et al., 2014).
3.6.1.1 Coal mine projects in the northern Galilee subregion
There are five potential new coal mining developments near the far northern boundary of the Galilee subregion (Figure 82). These include the Hughenden and Clyde Park coal projects in the Flinders river basin, and the Pentland, West Pentland and Milray projects in the catchment area of the Cape River (which, like the Belyando River, is also part of the larger Burdekin river basin). Similar to the seven modelled mines, all of these projects propose to develop thermal coal resources hosted in the upper Permian coal measures of the Galilee Basin, specifically the Betts Creek beds (companion product 2.3 for the Galilee subregion (Evans et al., 2018b)). Although detailed mine design and resource extraction planning is much less advanced than it is for the seven projects that are modelled, similar types of mining methods and associated mine infrastructure and water management systems are likely to be developed at these sites. Consequently, causal pathways are expected to be similar to those presented in companion product 2.3 for the Galilee subregion (Evans et al., 2018b); these causal pathways describe how an impact from a mining-related hazard may propagate and potentially affect regional hydrological systems and water-dependent assets (as summarised in Section 3.2.2).
Figure 82 Potential coal mining projects in the northern Galilee Basin
To improve presentation and display, not all coal exploration tenements in the northern Galilee Basin are included on this map. Only the main exploration and mineral development tenements associated with identified coal resources at the Hughenden, Clyde Park, West Pentland, Pentland and Milray projects are shown.
Data: Bureau of Meteorology (Dataset 1); Geological Survey of Queensland (Dataset 2, Dataset 3)
One notable point of difference from the proposed coal mines in the central-eastern part of the subregion is that the coal resources in the northern Galilee Basin are much smaller tonnages (Table 50). Some of this difference may be due to the less advanced nature of resource evaluation and appraisal in the northern Galilee Basin, as most of these coal resources have lower levels of geological assurance (i.e. resources mainly fall into the inferred category of the Joint Ore Reserves Committee (JORC) Code) compared to those from the central-eastern basin. However, even for the few deposits that have indicated or measured coal resources as per the JORC Code (indicating an enhanced level of geological knowledge), the total size is typically several billion tonnes less than the massive deposits found at places like Carmichael, China First and Kevin’s Corner (Table 50). The smaller tonnage coal resources targeted for mining in the northern Galilee Basin suggest that:
- The life of mine for these operations will generally be much shorter than the proposed mines in the central-eastern part of the subregion.
- Hydrological impacts will likely be relatively smaller in extent and magnitude (e.g. affect less area of surface water catchments), due to smaller mine footprints and lower extraction rates. The smaller mining operations will also potentially require lower volumes of groundwater to be extracted during mine dewatering. Consequently, aquifer drawdown may be less extensive, although the actual dewatering volume will depend greatly on the local hydrogeological architecture and aquifer characteristics of the target coal-bearing units and associated aquifer systems.
In addition, as the existing Mount Isa to Townsville railway line cuts across the north of the Galilee Basin, the proposed mining operations in the northern Galilee subregion may be able to access and utilise the existing rail network. Access to existing logistical services would reduce the need for development of new rail infrastructure (as is required for the central-eastern Galilee Basin), thereby limiting hydrological effects caused by mine-enabling infrastructure.
Table 50 Comparison of coal resource tonnages for coal mine projects in central-eastern and northern Galilee Basin
NA = data not available
Source: Evans et al, (20018b)
3.6.1.1.1 Coal mine projects in the Flinders river basin
3.6.1.1.1.1 Potential causal pathways
The Hughenden and Clyde Park coal projects are located in the headwaters of the Flinders river basin, between 50 to 70 km north and north-east (respectively) of the town of Hughenden (Figure 83). The main coal resource identified at Hughenden occurs in the north-east of exploration permit for coal (EPC) 1477, which is owned by the Australian-based company TerraCom Limited (formerly Guildford Coal). TerraCom also holds the major stake in the nearby Clyde Park Coal Project in EPC 1260.
The two exploration permits for coal (EPC) that contain identified coal resources at the Hughenden Coal Project are shown on this map, namely EPC 1477 (in the south), and EPC 1478 (in the north). Company announcements by TerraCom Limited indicate that the main area of likely coal mining development occurs in the north-east of EPC 1477. The main coal resource at Clyde Park occurs in EPC 1260, the larger of the two exploration tenements associated with this deposit.
GDE = groundwater-dependent ecosystem
Data: Geological Survey of Queensland (Dataset 3); Bioregional Assessment Programme (Dataset 4)
The black coal resources at the Hughenden Coal Project are between 300 and 600 m below surface (Guildford Coal, 2012). This substantial thickness of overburden means that underground longwall mining would be the most likely type of development for the Hughenden Coal Project. In comparison, coal seams in the Clyde Park area are much closer to surface, and even occur in outcrop in some places near the margins of the Galilee Basin. The coal resources defined at Clyde Park occur from 25 to 300 m below surface, and would likely be mined by a combined open-cut and underground operation. In their 2012 mining lease application for the Clyde Park Coal Project (mining lease application MLA 10369, which has subsequently expired), Guildford Coal suggested that the underground operations would be undertaken using longwall mining, accessed via a highwall entry through the open-cut pit (Guildford Coal, 2012).
There are currently no detailed plans publicly available to indicate the mine layout, development time frame or extraction rates for either the Hughenden or Clyde Park coal projects. However, the overall style of mining operations, whether open-cut or underground, are expected to share many general similarities with the more advanced mining projects of the Galilee Basin, situated about 200 to 300 km away to the south-east. Thus, the Assessment team considers that the four causal pathway groups outlined in companion product 2.3 for the Galilee subregion (Evans et al., 2018b) would also equally apply to both the Hughenden and Clyde Park projects. In particular, the main causal pathways that potentially have the greatest level of impact on hydrology in the central-eastern Galilee subregion would also be critical to further characterise and evaluate for the coal projects in the northern Galilee Basin. These would include the important subsurface dewatering causal pathways of ‘groundwater pumping enabling open-cut coal mining’ and ‘groundwater pumping enabling underground coal mining’, as well as ‘unplanned groundwater changes in non-target aquifers’. The causal pathway ‘fracturing and subsidence above underground mine longwall panels’ and ‘subsidence of land surface’ would be directly applicable to both the Hughenden Coal Project, and any underground operations at Clyde Park. The main causal pathways to consider as part of the surface water drainage group would include ‘altering surface water system’ and ‘intercepting surface water runoff’. Any future qualitative hydrological modelling and risk analysis of the Hughenden and Clyde Park projects in the northern Galilee Basin would benefit from adopting a similar approach to understanding the various causal pathways, as described in companion product 2.3 for the Galilee subregion (Evans et al., 2018b).
Along the north-eastern margin of the Galilee subregion, in the vicinity of the Hughenden and Clyde Park coal projects, the Rewan Group aquitard does not occur between the upper Permian coal measures and the Clematis Group aquifer (see Figure 20 in companion product 2.1-2.2 for the Galilee subregion (Evans et al., 2018a)). The absence of the Rewan Group in this part of the basin suggests either that it was never deposited within this area, or that it has subsequently been removed through a geological process such as faulting or erosion. Whatever the cause, the lack of the Rewan Group aquitard here may have implications for how the effects of subsurface dewatering for mining operations propagate away from open-cut mine pits or longwall panels. In particular, there is potential for a more direct hydraulic pathway in this area between the Clematis Group aquifer and the upper Permian coal measures, the main dewatering target. Consideration would need to be given to impacts to any groundwater assets or GDEs that may be sourcing water from the Clematis Group aquifer (specifically the Warang Sandstone in this region). It would be important for any future groundwater modelling of these mines to accurately represent the likely hydraulic pathways that connect the coal-bearing resource units and the main aquifer systems that may be hydrologically connected (either partially or completely).
Aquifers of the Great Artesian Basin (GAB) form part of the overlying stratigraphic sequence above the coal seams of the Hughenden Coal Project, and this is an important hydrogeological difference from the mines of the central-eastern Galilee Basin. In particular, the Hutton Sandstone to Cadna-owie – Hooray Sandstone and equivalents are important regional aquifers within this part of the Galilee subregion (see Figure 13 and Figure 14 in companion product 2.1-2.2 (Evans et al., 2018a) for distribution of these GAB aquifers). In contrast to Hughenden, the Clyde Park Coal Project occurs about 5 to 10 km to the east of the Eromanga Basin boundary, which means that the aquifers of the GAB are less likely to be directly affected by mining operations at Clyde Park.
The potential for fracturing and subsidence associated with underground mining at Hughenden to affect groundwater systems in these aquifers would need to be considered in future investigations, as well as source aquifers for nearby springs. Springs from the Flinders River spring group are thought to source groundwater from GAB aquifers (Fensham et al., 2016), and several of these occur in the vicinity of the Hughenden Coal Project. Other springs nearby are fed through discharge from Cenozoic basalts that locally overlie the GAB aquifers.
3.6.1.1.1.2 Landscape classes near Hughenden and Clyde Park
To provide an initial assessment of potentially impacted water-dependent landscape classes and assets around the Hughenden and Clyde Park coal projects, spatial overlay analysis using a geographic information system (GIS) was used to identify proximal ecosystems. An approximately 20 km radius zone was centred over the location of each coal resource to define a preliminary area in which to identify nearby landscape classes and assets. Although this 20 km zone has been chosen with regard to the area where the largest groundwater drawdowns are modelled for this BA (see Section 3.3), it is important to note that this does not imply that any future mining-related hydrological impacts associated with either of these projects will necessarily be restricted to this zone. As was the case for this BA, any future impact and risk analysis based on new hydrological modelling will need to use specific data relevant to each coal resource development. This would be critical to more accurately quantify the range of potential hydrological changes for key aquifer systems and surface water networks around each coal project.
Analysis of the spatial query outputs indicates that the ecosystems around both the Hughenden and Clyde Park coal projects are dominated by the ‘Dryland, remnant vegetation’ landscape class (as defined for this BA, see Section 2.3.3 of companion product 2.3 for the Galilee subregion (Evans et al., 2018b)), comprising almost 90% of the total surface area within a 20 km radius of each project. Within the context of the BA for the Galilee subregion, the dryland landscape classes are not considered water dependent as these ecosystems rely on incident rainfall and associated surface water run-off for their water requirements. The main water-dependent landscape class around the Hughenden and Clyde Park coal projects is ‘Non-floodplain, terrestrial GDE, remnant vegetation’, which generally comprises between 8% to 12% of the surface area within 20 km of each site (Figure 83). Other minor water-dependent landscape classes include ‘Wetland GDE, remnant vegetation’ and ‘Floodplain disconnected non-wetland, remnant vegetation’.
Any potential surface water changes resulting from future mining operations at Hughenden and Clyde Park will likely be confined to streams within the Flinders river basin, such as the Flinders River, Dutton River and Porcupine Creek (Figure 82). All nearby stream networks are classed as temporary streams in the BA landscape classification, and include both lowland and upland GDE streams (Figure 83). Several small discharge springs are also mapped within this area.
3.6.1.1.1.3 Water-dependent assets near the Hughenden Coal Project
Within an approximately 20 km radius of the Hughenden Coal Project there are over 60 individual water-dependent assets, as listed in the water-dependent asset register for the Galilee subregion (Bioregional Assessment Programme, 2017). Most of these are ecological assets of the vegetation subgroup, and are typically either GDEs or habitat classed as the potential distribution of a particular species of fauna or flora. Three of the GDEs within this zone cover a total area greater than 50 km2, these being:
- moist to dry eucalypt open-forests to woodlands mainly on basalt areas – this is considered a GDE with moderate potential for groundwater interaction (this asset covers about 93 km2 of the area)
- dry eucalypt woodlands to open-woodlands primarily on sandplains or depositional plains – this GDE has moderate potential for groundwater interaction (about 59 km2)
- Acacia cambagei / A. georginae / A. argyrodendron dominated associations – these GDEs have low potential for groundwater interaction (about 54 km2).
Note that in the three examples above, the classification of these GDEs as having either ‘moderate’ or ‘low’ potential for groundwater interaction reflects the naming conventions in one of the key source datasets used for defining the water-dependent assets in the Galilee subregion. This is the National atlas of groundwater dependent ecosystems (Bureau of Meteorology, 2017), also known as the GDE Atlas, which provides a national-scale inventory of GDEs. The GDE Atlas defines three classes of ecosystems based on their potential to interact with groundwater, namely those with high potential, moderate potential or low potential for groundwater interaction. In these cases, the term ‘potential’ is used to reflect the uncertainty inherent in identifying ecosystems as groundwater dependent using the various desktop methods employed by the authors of the GDE Atlas (Bureau of Meteorology, 2017). This terminology has been adopted to help name the many GDEs that are included as water-dependent assets in the Galilee subregion, and is also used elsewhere in this section.
The main species habitat (potential distribution) includes that of pink gidgee (Acacia crombiei) and the squatter pigeon (southern) (Geophaps scripta scripta), each of which covers about one-third of the area within 20 km of the Hughenden Coal Project. The potential habitat distribution of several species of grass listed as water-dependent assets, including bluegrass (Dichanthium setosum), hairy-joint grass (Arthraxon hispidus) and king blue-grass (Dichanthium queenslandicum), is also widespread across this area.
Other water-dependent assets within the vicinity of the Hughenden Coal Project include:
- Porcupine Gorge National Park, which is recognised multiple times in the asset register for both its ecological and sociocultural values, as well as being an Indigenous asset
- various groundwater features, including the extent of regionally important aquifers such as the Clematis Group, or areas of recharge beds for aquifers of the GAB (e.g. Gilbert River Formation)
- basic water rights (a type of economic asset) in the Flinders East 2 and Flinders East 3 groundwater management units
- various rivers, lakes and other wetlands regarded as ecologically important surface water features.
3.6.1.1.1.4 Water-dependent assets near the Clyde Park Coal Project
The list of water-dependent assets within an approximately 20 km radius of the Clyde Park Coal Project is very similar to that for Hughenden, although there are slightly more listed assets around Clyde Park (about 75 assets). About half of these assets are GDEs of various size, shape and complexity, with dry eucalypt woodlands being the most abundant type. There are several discrete areas of dry eucalypt woodland covering more than 100 km2, although these are considered to have variably low to moderate potential for groundwater interaction (based on the classification scheme used in the source dataset of the GDE Atlas). The other main type of water-dependent asset within 20 km of Clyde Park is the potential habitat of different flora and fauna. This includes nine different plant and grass species, including Acacia ramiflora and bluegrass, three bird species, including the squatter pigeon and black-throated finch (Poephila cincta cincta), as well as one species each of fish (largetooth sawfish (Pristis pristis)), reptile (yakka skink (Egernia rugosa)) and mammal (ghost bat (Macroderma gigas)).
As shown in Figure 82, the White Mountains National Park borders part of the Clyde Park coal exploration tenement. This national park is listed multiple times in the water-dependent asset register for the Galilee subregion, and is recognised for ecological and sociocultural values, as well as being an important place for local Indigenous people (Constable and Love, 2014).
3.6.1.1.2 Coal mine projects in the Burdekin river basin
A cluster of identified coal resources occurs near the small country township of Pentland in the north-east of the Galilee Basin (Figure 84 and Table 50). The Milray, Pentland and West Pentland coal projects are all in the Galilee subregion’s CRDP, as explained in companion product 2.3 for the Galilee subregion (Evans et al., 2018b). However, none of these deposits could be included in the BA hydrological modelling as all have not advanced beyond initial exploration and appraisal stages. There are individual mineral development licences covering both Pentland (MDL 356 owned by Glencore) and West Pentland (MDL 361 owned by United Mining Group, a subsidiary of United Queensland Resources), with the Milray resource occurring in EPC 771 (owned by Glencore). There is relatively scant information publicly available as to how these coal resources will be mined in the future, and when such development is likely to occur.
The Milray, Pentland and West Pentland coal projects are all situated in the Cape river basin (Figure 82). The Cape river basin is immediately north of the Belyando river basin and comprises part of the headwaters for the larger catchment of the Burdekin river basin (Figure 12). The surface water modelling undertaken for this BA included several model nodes along the Cape River, and modelling results for all of these nodes indicated that the Cape River is very unlikely (less than 5% chance) to be impacted by the seven coal mines in the central-eastern Galilee subregion (i.e. the mines modelled in the CRDP for this BA). Consequently, any surface water hydrological changes that may potentially arise from development activities at Milray, Pentland or West Pentland are likely to be the first coal mining impacts experienced within the Cape river basin. However, as the Cape River eventually flows into the Belyando/Suttor rivers just upstream of Lake Dalrymple (the lake created by the Burdekin Falls Dam), these coal mining impacts would largely be expected to be restricted to the Cape river basin. This reflects one of the important outcomes of the hydrological analysis from this BA which indicates that coal mining impacts in the Belyando river basin will not extend beyond the limit of Lake Dalrymple (see Section 3.3.3 and Section 3.3.4 for further detail).
This map does not include all of the coal exploration permits that exist within this part of the north-eastern Galilee Basin. It only focuses on the mineral development licence (MDL) tenements relevant to the Pentland (MDL 356) and West Pentland (MDL 361) coal deposits, and the exploration permit for coal (EPP) that contains Milray (EPP 771).
GDE = groundwater-dependent ecosystem
Data: Geological Survey of Queensland (Dataset 2, Dataset 3); Bioregional Assessment Programme (Dataset 4)
3.6.1.1.2.1 Potential causal pathways
The publicly available information about Milray, Pentland and West Pentland indicate that the coal resources are buried within several hundred metres of the surface. Information in Glencore (2016) indicates that both Milray and Pentland could be mined by a combination of open-cut and underground mining methods. In comparison, most of the coal resource at West Pentland is between 100 and 200 m below surface, suggesting that open-cut mining is a viable option. However, as there is no detailed mine development information available, further mine optimisation and planning is undoubtedly required to evaluate the most suitable style of mining operation. Assuming that any future mining development at Milray, Pentland and West Pentland would involve open-cut, and potentially also longwall mining, then most of the coal mine causal pathways outlined in companion product 2.3 for the Galilee subregion (Evans et al., 2018b) will likely be applicable to this area. The overburden for these coal projects consists largely of sedimentary rocks of the Clematis Group and a variety of shallow Cenozoic sediments closely associated with the main surface water drainages. As is the case for the Hughenden and Clyde Park coal projects (Section 3.6.1.1.1.2), the Rewan Group aquitard is largely absent from this area, which may have implications for hydrological connectivity between the Clematis Group aquifer (specifically the Warang Sandstone) and the upper Permian coal measures. No discharge springs have been mapped in the Burdekin river basin in the vicinity of these three coal projects (Figure 84).
The proximity of coal resources at Milray, Pentland and West Pentland (all are within 30 to 40 km) indicates that there is the potential for mining to cause spatially and temporally overlapping hydrological changes in both the groundwater and surface water systems. Depending on the scale and timing of each operation, this may lead to cumulative impacts to water resources and water-dependent assets. However, with the current understanding of the extent of the zone of potential hydrological change for the Galilee subregion (Section 3.3), it is unlikely that dewatering of the watertable aquifer around the Pentland cluster will overlap with dewatering effects of coal projects further south in the central-eastern Galilee Basin. There may be potential for cumulative drawdown interference to occur in the deeper confined aquifers of the Clematis Group and the upper Permian coal measures (given that drawdown effects propagate further in these confined systems than in the watertable), and further investigation of that possibility may be warranted.
3.6.1.1.2.2 Landscape classes near Milray, Pentland and West Pentland
The tenements that host the Pentland and West Pentland coal projects share a common border (Figure 82), and thus analysis of landscape classes has been undertaken jointly for an approximately 20 km radius zone centred on their shared boundary. The dominant landscape class is ‘Dryland, remnant vegetation’, which covers nearly 70% of the total surface area in the vicinity of Pentland and West Pentland. However, there are some relatively large areas of remnant vegetation associated with terrestrial GDEs (about 13% of area within 20 km of these coal projects), as well as non-floodplain terrestrial GDEs in areas up-slope of the floodplain (about 14% of this area). Further information about floodplain and non-floodplain terrestrial GDEs, including important hydrological response variables, is outlined in companion product 2.7 for the Galilee subregion (Ickowicz et al., 2018).
The distribution of landscape classes within 20 km of Milray is similar to that of Pentland and West Pentland, with the ‘Dryland, remnant vegetation’ class comprising over 75% of the area. Likewise, the two main water-dependent ecosystems are ‘Terrestrial GDE, remnant vegetation’ (about 13%) and ‘Non-floodplain, terrestrial GDE, remnant vegetation’ (about 7%). Although there are 19 different landscape classes that occur within 20 km of Milray, the total combined area of 13 of these amounts to less than 1% of this entire surface area.
The main landscape classes associated with surface water systems around the Milray, Pentland and West Pentland coal projects are ‘Temporary, lowland stream’ or ‘Temporary, lowland GDE stream’. There are no near-permanent streams in these areas, nor are there are any springs mapped within 20 km of these coal projects.
3.6.1.1.2.3 Water-dependent assets near Pentland and West Pentland
The Pentland and West Pentland coal projects occur near the south-eastern margin of the White Mountains National Park (Figure 82). This is an important regional water-dependent asset which is listed multiple times in the BA asset register for a variety of ecological, sociocultural and Indigenous values. The White Mountains National Park is also included on the Register of the National Estate (Sparrow et al., 2015).
There are also a variety of other ecological assets within the vicinity of the Pentland and West Pentland coal projects, including over 40 GDEs, and 15 potential species distributions. These include the potential distributions of eight different types of flora (of which Acacia ramiflora and bluegrass are the most widespread), three types of birds (squatter pigeon, star finch (Neochmia ruficauda ruficauda) and black-throated finch), two reptiles and two mammals (northern quoll (Dasyurus hallucatus) and ghost bat).
3.6.1.1.2.4 Water-dependent assets near Milray
There are about 60 water-dependent assets within an approximately 20 km radius of the Milray Coal Project, most of which are ecological assets of the ‘Vegetation’ subgroup. There are a variety of assets classed as GDEs, with the most widespread types being:
- Eucalyptus populnea or E. melanophloia (or E. whitei) dry woodlands to open-woodlands on sandplains or depositional plains – these are classed as GDEs with low to moderate potential for groundwater interaction (as per the GDE Atlas)
- dry eucalypt woodlands to open-woodlands, mostly on shallow soils in hilly terrain (mainly on sandstone and weathered sedimentary rocks) – these are considered to be GDEs with low to moderate potential for groundwater interaction
- Acacia spp. on residual landforms (species include A. stowardii, A. shirleyi, A. microsperma, A. catenulata and A. rhodoxylon) – these are considered GDEs with low to moderate potential for groundwater interaction.
The other main type of ecological asset near Milray is vegetation habitat forming the potential distribution of particular flora and fauna. This includes habitat for three different bird species, namely the star finch (about 940 km2), squatter pigeon (720 km2) and black-throated finch (540 km2). Additionally, the habitat of a number of different plant species exceeds 100 km2 within an approximately 20 km radius of Milray, including Acacia ramiflora, Kardomia squarrulosa and bluegrass.
Other water-dependent assets within about 20 km of Milray include:
- two economic assets associated with the Barcaldine North 3 groundwater management unit (one being a basic water right and the other a water access right)
- several subsurface groundwater features, including the extent of various regional aquifers such as the Clematis Group, or areas of GAB recharge beds
- a number of surface water features such as rivers, creeks, wetlands and floodplains in the Burdekin river basin.
3.6.1.2 Coal mine projects in the central Galilee subregion
The Alpha West Coal Project is adjacent to the Alpha Coal Project in the central-eastern Galilee Basin (Figure 6). Both projects will largely target the same coal seams, although operations at Alpha West are expected to extract coal using underground longwall mining methods from the more deeply buried coal resources west of the open-cut pits at Alpha (Lewis et al., 2014). Any hydrological and associated ecosystem impacts from underground mining at Alpha West could potentially be cumulative with those associated with other mining operations in this part of the Galilee subregion, especially the adjacent longwall mines planned at Kevin’s Corner to the north, and China First to the south. Although not quantified here due to lack of relevant data, the additional groundwater pumping required for dewatering the proposed longwall operations at Alpha West may lead to some increased drawdown impacts to the near-surface aquifer, as well as to the confined groundwater systems of the Clematis Group aquifer and the upper Permian coal measures.
The current development time frame for Alpha West remains unknown, although it would clearly begin only after open-cut operations at the nearby Alpha Coal Mine were suitably advanced. By the time that Alpha West development began, dewatering at the adjacent Alpha open-cut mine would likely already be lowering the local watertable. Hence, future dewatering operations at Alpha West would need to factor the prior effects of pumping at Alpha, as well as cumulative effects from the other nearby mining operations to both the north and south.
The main causal pathways that will likely impact hydrological systems in and around the Alpha West mining lease are captured by the underground mining causal pathways specified in companion product 2.3 for the Galilee subregion (Evans et al., 2018b) and include:
- ‘groundwater pumping enabling underground coal mining’
- ‘unplanned groundwater changes in non-target aquifers’
- ‘subsurface fracturing above underground longwall panels’
- ‘altering surface water systems’
- ‘subsidence of land surface’.
Given the location of the Alpha West Coal Project, readers are referred to earlier sections of this product for a more detailed analysis of potential impacts and risks to the hydrology (Section 3.3), ecosystems (Section 3.4) and water-dependent assets (Section 3.5) within the central-eastern Galilee subregion.
3.6.1.3 Coal mine projects in the southern Galilee subregion
The Blackall Coal Project is the only operation in the Galilee subregion’s CRDP where the coal resources lie within the geological Eromanga Basin, rather than the upper Permian coal measures of the older Galilee Basin (Lewis et al., 2014). The coal resources at Blackall are hosted in the mid Cretaceous Winton Formation, and are thus about 150 million years younger than the Galilee Basin’s upper Permian coals. The Winton Formation coals are sub-bituminous and have moisture contents of 18% to 22%, meaning that they are coals of lower rank and higher moisture content than most Permian coals of the Galilee Basin. Across much of the Galilee subregion the sedimentary sequences of the Eromanga Basin form the overburden for the underlying rocks of the Galilee Basin. In addition, many stratigraphic units of the Eromanga Basin are major regional aquifers of the GAB and contain extensive, good quality groundwater resources.
3.6.1.3.1 Potential causal pathways
According to published information from East Energy Resources, the coal resources at the Blackall Coal Project will be mined using open-cut mining methods (East Energy Resources, 2014). The identified coal resource occurs in six main coal seams and the uppermost of these subcrops across much of the tenement area (i.e. it occurs close to the surface). Based upon the results of extensive exploration drilling, a large-scale thermal coal resource has been defined in the area of Mineral Development Licence (MDL) 464. This resource could support a large-scale open-cut mining operation, targeting around 30 Mt/year of mineable coal over at least 30 years life-of-mine.
Considering the suggested large-scale open-cut mining operation at Blackall, the types of hazards and potential impacts to water-dependent assets may be analogous to those associated with similar coal mine projects such as the Alpha Coal Project. The main causal pathways arising from large-scale open-cut mining operations associated with the Blackall Coal Project could include:
- ‘groundwater pumping enabling open-cut coal mining’
- ‘altering surface water systems (coal mining)’
- ‘intercepting surface water runoff’.
Fundamental differences exist between the hydrogeological systems that occur in the Winton Formation and those of the upper Permian coal measures, which will affect how groundwater systems will respond to mine dewatering. Preliminary mine planning indicates that the most likely type of operation will involve open-cut mining to depths of no more than 150 m below surface, and will likely remain within the same stratigraphic unit (Winton Formation). This suggests that mine dewatering impacts will mainly affect the regional watertable in the near-surface aquifer, which in this area is likely to be hosted in the weathered rocks of the Winton Formation. Within the near vicinity of the Blackall Coal Project, there is some potential for impacts to groundwater levels in pastoral and/or stock and domestic bores that tap the near-surface aquifer in the Winton Formation. However, dewatering of the Winton Formation (part of the wider regional Winton-Mackunda aquifer, Ransley et al. (2015)) is unlikely to affect the deeper confined groundwater systems of the GAB, such as those hosted in the Cadna-owie Formation, Hooray Sandstone and Hutton Sandstone. This is because the groundwater systems of the Winton-Mackunda aquifer are separated from the underlying confined aquifers by up to several hundred metres of low permeability strata, which form the basal aquitard sequence of the Rolling Downs Group. These aquitards would be expected to impede the transmission of any near-surface drawdown effects into the deeper GAB aquifers (although this would clearly need to be further evaluated via purpose-built groundwater models).
The isolation of open-cut pits and mine infrastructure areas from the rest of the Barcoo river basin will result in changes to runoff volumes to nearby surface water catchments, such as those of Four Mile Creek and Ravensbourne Creek. The likely reductions in runoff may then affect the volume and timing of any surface water flows that occur in these ephemeral drainages. There may also be localised changes to water quality as a result of mine-related impacts to surface water systems, such as increases in total suspended solid loads in minor streams due to enhanced levels of erosion, which may occur following heavy rainfall events. However, given the distances (at least 150 km) from Blackall to the other coal mines in the Galilee subregion CRDP, and its occurrence in the younger strata of the Eromanga Basin, there is (conceptually) very low potential for cumulative hydrological impacts associated with these other operations.
3.6.1.3.2 Landscape classes near Blackall Coal Project
The Blackall Coal Project is situated in the headwaters of the Barcoo river basin, which is part of the larger Cooper Creek – Bulloo river basin. As for most of the Galilee subregion, the ‘Dryland’ landscape group dominates the area within an approximately 20 km radius of the Blackall Coal Project (Figure 85), comprising over 80% of the surface area. There are only three water-dependent landscape classes that cover more than 1% of the surface area within 20 km of Blackall, these being ‘Terrestrial GDE, remnant vegetation’ (about 13.5%), ‘Floodplain disconnected non-wetland, remnant vegetation’ (about 3.5%) and ‘Floodplain disconnected non-wetland’ (about 1.5%).
The combined area of the ten other landscape classes that occur within 20 km of Blackall Coal Project amount to less than 1% of the total area. Most rivers and creeks are classed as ‘Temporary, lowland streams’, and there are no groundwater-fed springs within this vicinity. The main streams within the Blackall tenement are Bride Creek and Four Mile Creek, which join towards the north of the tenement and flow into the larger Ravensbourne Creek (Figure 85), a tributary of the Barcoo River.
3.6.1.3.3 Water-dependent assets near Blackall Coal Project
In contrast to the areas surrounding the coal projects of the northern Galilee Basin, there are considerably fewer water-dependent assets within about 20 km of Blackall Coal Project. There are approximately 20 ecological assets in the water-dependent asset register, which include:
- ten GDEs of the vegetation subgroup, most of which are location-specific GDEs associated with particular waterways (e.g. Bride Creek GDE, Ravensbourne Creek GDE, and Hope Creek GDE) – many are considered to have only a low potential for groundwater interaction
- four potential species distributions (two plants, one bird and one mammal), as defined by habitat. The plant species are ooline (Cadellia pentastylis) and climbing caustic (Euphorbia sarcostemmoides), and animal species are the painted honeyeater (Grantiella picta) and the koala (Phascolarctos cinereus)
- various groundwater and surface water features, such as aquifer boundaries (e.g. the extent of the Cadna-owie Formation and Clematis Group), GAB recharge beds and several lakes and rivers of the Barcoo river basin.
In addition to the ecological assets, there are six economic assets within 20 km of Blackall Coal Project. These include basic water rights across five groundwater management units in the Barcaldine South and Warrego West groundwater management areas. Each of these basic water rights consists of a variable number of individual groundwater bores which are mainly used for stock and domestic purposes. There is also a single surface water access right in the Barcoo Subcatchment Management Group.
Figure 85 Landscape groups near the Blackall Coal Project in the central Galilee Basin
The identified coal resource at Blackall is in Mineral Development Licence (MDL) 464, which is the only tenement shown on this map. Other exploration permits for coal which occur in this area are not depicted.
GDE = groundwater-dependent ecosystem
Data: Geological Survey of Queensland (Dataset 2); Bioregional Assessment Programme (Dataset 4)
