This section describes the potential cumulative effects of the CRDP in the Maranoa-Balonne-Condamine subregion, which includes five baseline CSG operations, five baseline open-cut coal mines and two additional open-cut coal mines (New Acland Coal Mine Stage 3 and The Range). Coal resource development has the potential to affect aquifers, catchments and watercourses via the four main causal pathway groups discussed previously:
- ‘Subsurface depressurisation and dewatering’
- ‘Subsurface physical flow paths’
- ‘Surface water drainage’
- ‘Operational water management’.
‘Subsurface depressurisation and dewatering’ associated with the five baseline CSG operations, five baseline open-cut coal mines and two additional open-cut coal mines have the potential to directly affect the regional groundwater system, and indirectly affect surface water – groundwater interactions in aquifer outcrop areas. Cross-sections A to A’ in Figure 38 and B to B’ in Figure 39 (cross-section locations are shown in Section 2.3.2, Figure 8) illustrate the location and stratigraphy of aquifers near The Range coal mine. These cross-sections show that the cumulative effect of the baseline and additional coal resource developments near The Range is likely to extend beyond the tenements, potentially affecting connected aquifers and surface water systems. This may include a small portion of Quaternary alluvium associated with Dogwood Creek along the southern boundary. The cumulative effect of subsurface dewatering and depressurisation has the potential to affect groundwater discharge to springs and watercourse springs along the Dawson River (shown in Figure 39). Watertable level contours in the vicinity of The Range (Figure 40) indicate a groundwater flow divide within the proposed mine footprint that corresponds to the surface water divide and subregion boundary. This means that local-scale changes to groundwater flow directions associated with dewatering or operational water management could occur to both the east and west of the mine. Cross-section A to A’ (Figure 38) shows that the Walloon Coal Measures dip in a south-westerly direction away from The Range coal mine, which indicates the potential for interactions with surficial Quaternary and Cenozoic alluvial systems near the mine and with the Springbok Sandstone further to the south. This is consistent with the location of the Springbok Sandstone to the west of the mine shown in cross-section B to B’ (Figure 39).
Also shown is the location of the New Acland Mine.
CSG = coal seam gas, Fm = Formation, WCM = Walloon Coal Measures
Data: Bioregional Assessment Programme (Dataset 6), Geoscience Australia (Dataset 7), Department of Natural Resources and Mines (Dataset 8, Dataset 12), Office of Groundwater Impact Assessment (Dataset 11)
CSG = coal seam gas, Fm = Formation, Sst = Sandstone
Data: Bioregional Assessment Programme (Dataset 6), Geoscience Australia (Dataset 7), Department of Natural Resources and Mines (Dataset 8, Dataset 12), Office of Groundwater Impact Assessment (Dataset 11)
Deep soil drainage and surface water – groundwater interactions in aquifer outcrop areas can also be affected by coal mining. Figure 40 shows the relationship of The Range coal mine footprint relative to the surface geology mapping.
Data: Geoscience Australia (Dataset 9), Department of Natural Resources and Mines (Dataset 10, Dataset 12)
Expansion of New Acland Coal Mine for Stage 3 has the potential to directly affect the regional groundwater system, and indirectly affect surface water-groundwater interactions in connected aquifer outcrop areas. The New Acland Coal Mine is located in the north-eastern surficial extent of the Walloon Coal Measures, surrounded by the Main Range Volcanics and up gradient of the Condamine Alluvium as shown in cross-section C to C’ (Figure 41) and D to D’ (Figure 42). The Condamine Alluvium and Main Range Volcanic aquifers are important water sources for irrigation, stock and domestic and town water supplies.
Surface water flows from elevated areas around the New Acland Coal Mine in a westerly direction to the flatter landscape of the Condamine Alluvium. Groundwater flow is also from east to west along the westward-dipping geological layers (see Section 2.3.2, Figurre 8). The footprint of the New Acland Coal Mine Stage 3 overlies outcropping Walloon Coal Measures as well as Main Range Volcanics and Cenozoic units (Figure 43). Disturbance caused by the mine has the potential to affect Lagoon Creek, a tributary to Oakey Creek that flows through the mine footprint. Disturbance to the Cenozoic cover has the potential to affect Cain Creek to the north, and Doctor Creek to the south of the mine.
Three spring complexes that are associated with the Main Range Volcanics aquifer are located within 20 km of the New Acland Coal Mine. Two of the spring complexes are down gradient from the mine, including the non-GAB Bowenville Springs complex. The cumulative effect of subsurface dewatering and depressurisation in the Walloon Coal Measures for mining and CSG operations has the potential to indirectly affect groundwater discharge to springs and watercourse springs that flow towards the Condamine Alluvium.
Note the surficial extent of the Birkhead Formation/Walloon Coal Measures near the New Acland Coal Mine
CSG = coal seam gas, Fm = Formation, Grp = Group, Qa = Quaternary deposits, Sst = Sandstone
Data: Bioregional Assessment Programme (Dataset 6), Geoscience Australia (Dataset 7), Department of Natural Resources and Mines (Dataset 8, Dataset 12), Office of Groundwater Impact Assessment (Dataset 11)
CSG = coal seam gas, Fm = Formation, Grp = Group, Sst = Sandstone
Data: Bioregional Assessment Programme (Dataset 6), Geoscience Australia (Dataset 7), Department of Natural Resources and Mines (Dataset 8, Dataset 12), Office of Groundwater Impact Assessment (Dataset 11)
Data: Geoscience Australia (Dataset 9), Department of Natural Resources and Mines (Dataset 10, Dataset 12)
Table 17 summarises the main causal pathway groups linking coal resource development to potentially affected parts of the Maranoa-Balonne-Condamine subregion. The table shows that open-cut coal mines and CSG operations that affect ‘subsurface depressurisation and dewatering’ (thus reducing groundwater pressures) can have widespread effects in connected aquifers, and indirectly affect surface water – groundwater interactions in aquifer outcrop areas. Changes to ‘Subsurface physical flow paths’ are likely to be localised within an aquifer or aquifer outcrop area within tenements, but can affect watercourses within and downstream of tenements. The area affected by ‘surface water drainage’ depends on the development location and can potentially affect watercourses within and downstream of tenements. Similarly, the area affected by ‘Operational water management’ depends on the location and geological setting of water management structures and disposal infrastructure. This causal pathway group can potentially affect the alluvium and watercourses in aquifer outcrop areas within and downstream of tenements.
Table 17 Causal pathway groups arising from open-cut coal mines and coal seam gas operations for baseline coal resource development (baseline) and coal resource development pathway (CRDP)
Both the baseline and the CRDP include open-cut coal mines and coal seam gas operations, and therefore the causal pathway groups are the same for both.
