BHP : BWM North Extension Project – EA Amendment Application – Appendix F

Appendix F

Groundwater Impact Assessment

Blackwater Mine - North Extension Project

Groundwater Impact Assessment

BM Alliance Coal Operations Pty Ltd

480 Queen Street

Brisbane, QLD 400

Prepared by:

SLR Consulting Australia

Level 16, 175 Eagle Street, Brisbane QLD 4000,

Australia

SLR Project No.: 620.014601.00006 R01

Client Reference No.: AU.015980

11 December 2023

Revision: v2.3

	11 December 2023
BM Alliance Coal Operations Pty Ltd	SLR Project No.: 620.014601.00006
Blackwater Mine - North Extension Project	R01

Revision Record

Revision	Date	Prepared By	Checked By	Authorised By
V1.0	25 September 2023	D Ashton,	I Epari	FIRST DRAFT
		KJ Wallis
		P Rachakonda
V2.0	9 November 2023	L Mynott	I Epari
V2.2	1 December 2023	M Nariansamy	I Epari	P Allen
V3.0	11 December 2023	M Nariansamy	I Epari	P Allen

Basis of Report

This report has been prepared by SLR Consulting Australia (SLR) with all reasonable skill, care and diligence, and taking account of the timescale and resources allocated to it by agreement with BM Alliance Coal Operations Pty Ltd (the Client). Information reported herein is based on the interpretation of data collected, which has been accepted in good faith as being accurate and valid.

This report is for the exclusive use of the Client. No warranties or guarantees are expressed or should be inferred by any third parties. This report may not be relied upon by other parties without written consent from SLR.

SLR disclaims any responsibility to the Client and others in respect of any matters outside the agreed scope of the work.

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BM Alliance Coal Operations Pty Ltd		11 December 2023
Blackwater Mine - North Extension Project	SLR Project No.: 620.014601.00006 R01
Table of Contents
Basis of Report	i
Acronyms and Abbreviations	ix
1.0	Introduction	1
1.1	Overview	1
1.2	Project Background	1
1.3	Study Objectives	5
2.0	Legislative Requirements and Relevant Guidelines	6
2.1	Legislation	6
2.1.1 Commonwealth Environment Protection and Biodiversity Act 1999	6
2.1.2 Queensland Water Act 2000	15
2.1.3 Environmental Protection (Water and Wetland Biodiversity) Policy 2019	17
2.1.4 Environmental Authority	18
2.2	Relevant Guidelines	18
3.0	Existing Conditions	19
3.1	Climate	19
3.2	Topography and Drainage	21
3.3	Land Use	24
3.3.1 Agriculture	24
3.3.2 Mining	26
3.3.3 Petroleum	29
4.0	Geology	30
4.1	Quaternary Sediments	35
4.2	Tertiary Sediments and Basalt	35
4.3	Triassic Clematis Group	35
4.4	Triassic Rewan Group	35
4.5	Permian Rangal Coal Measures	35
4.6	Burngrove Formation	36
4.7	Structural Geology	36
5.0	Hydrogeology	39
5.1	Groundwater Monitoring	39
5.2	Hydraulic Properties	45
5.2.1 Northern Area	45
5.2.2 Southern Area	48
5.2.3 Faults	49
5.3	Groundwater Distribution, Flow, Recharge and Discharge	50

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BM Alliance Coal Operations Pty Ltd		11 December 2023
Blackwater Mine - North Extension Project	SLR Project No.: 620.014601.00006 R01
5.3.1 Quaternary Sediments (Alluvium)	50
5.3.2 Tertiary Sediments	51
5.3.3 Clematis Group	52
5.3.4 Rewan Group	52
5.3.5 Rangal Coal Measures	53
5.3.6 Burngrove Formation	61
5.3.7 Vertical Flow between Units	61
5.3.8 Groundwater-Surface Water Interactions	64
5.4	Groundwater Quality	64
5.4.1 Physicochemical Parameters	64
5.4.2 Metals	75
5.5	Groundwater Use and Management	76
5.5.1 Groundwater Dependent Ecosystems	77
5.5.2 Springs	83
5.5.3 Wetlands	83
5.5.4 Anthropogenic Groundwater Users (Landholder Bores)	............................................. 83
5.6	Conceptual Hydrogeological Model	86
5.6.1 Groundwater Levels and Flow	86
5.6.2 Groundwater -Surface Water Interaction	87
5.6.3 Groundwater Quality	87
5.6.4 Mining Impacts	87
5.7	Water Levels and Ecohydrogeological Models	89
5.7.1 Approach and Methodology	89
5.7.2 Water levels and Water Table Depth	89
5.7.3 Groundwater Chemistry	91
5.7.4 Summary of Conceptual Hydrological Model	91
5.7.5 Conceptual Ecohydrological Models	91
6.0	Groundwater Numerical Model	95
6.1	Model Objectives	95
6.2	Software	95
6.3	Model Setup	95
6.3.1 Model Grid and Layers	97
6.3.2 Boundary Conditions	97
6.3.3 Temporal Discretisation	100
6.3.4 Calibration Results	101
6.3.5 Calibrated Hydraulic Properties	105

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BM Alliance Coal Operations Pty Ltd		11 December 2023
Blackwater Mine - North Extension Project	SLR Project No.: 620.014601.00006 R01
6.4	Model Predictions	106
6.4.1 Predicted Groundwater Interception	107
6.4.2 Predicted Maximum Drawdowns	108
6.4.3 Incidental Water Impact	115
6.4.4 Post Mining Equilibrium	115
6.5	Sensitivity Analysis	119
6.6	Uncertainty Analysis	119
6.6.1 Uncertainty of Mine Inflows	119
6.6.2 Groundwater Drawdowns	120
6.6.3 Uncertainty of Drawdown at Landholder Bores	126
6.6.4 Uncertainty of Influence on Alluvium and Surface Water Flow	.................................. 128
6.7	Model Limitations	128
7.0	Impacts on Groundwater Resources	129
7.1	Highlands Groundwater Management Area	129
7.2	Potential Impact on Groundwater Users	129
7.2.1 Privately-Owned Supply Bores	129
7.2.2 Groundwater Dependent Ecosystems	131
7.3	Potential Impacts on Surface Drainage	133
7.4	Potential Impacts on Groundwater Quality	133
7.4.1 In Pit Waste Rock Emplacement Areas	133
7.4.2 Final Void	133
7.4.3 Workshops and Storage	134
7.5	Impact of Climate Change on Predictions	134
7.5.1 Climate Impact on Predictions	135
7.5.2 Climate Impact on Long-termPost-Mining Recovery	135
8.0	Management and Mitigation	136
8.1	Mitigation Measures	136
8.1.1 Mine Affected Water	136
8.1.2 Groundwater Use	136
8.2	Groundwater Management	136
8.2.1 Groundwater Monitoring Program	136
8.2.2 Data Management and Reporting	137
9.0	References	138

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BM Alliance Coal Operations Pty Ltd		11 December 2023
Blackwater Mine - North Extension Project	SLR Project No.: 620.014601.00006 R01
Tables in Text
Table 2-1	IESC Information Requirements Checklist	7
Table 3-1	Current Mining Operations and Advanced Projects within 50 km of the Project
	.......................................................................................................................	27
Table 3-2	Exploration Permits within 10 km of ML1759 and ML1762	29
Table 4-1	Summary of Stratigraphy in the Study Area	30
Table 5-1	Monitoring Network	40
Table 5-2	Blackwater Northern Area Slug Test Results	45
Table 5-3	Minyango Falling-Head Tests	46
Table 5-4	Drill stem Test Results (EMM, 2019)	48
Table 5-5	Hydraulic Parameters (South Blackwater Area)	48
Table 5-6	Water Levels at Grouped Standpipe Bores	63
Table 5-7	Summary Statistics of Field pH Observations	65
Table 5-8	Summary Statistics of Field EC Observations	65
Table 5-9	Guideline Values for EA Metals and Metalloids	75
Table 5-10	Existing Private Groundwater Bores within 10 km of the Project Area (DRDMW
	GWDB)	84
Table 5-11	Summary of bores included in the water table mapping (RDM Hydro et al, 2023)
	.......................................................................................................................	90
Table 6-1	Stratigraphy - Model Layer Summary	97
Table 6-2	River and Surface Water Features in the Model	98
Table 6-3	Mining Infrastructure in the Model	99
Table 6-4	Calibrated Recharge	99
Table 6-5	Calibration Statistics	101
Table 6-6	Calibrated Hydraulic Conductivities	105
Table 6-7	Predicted Maximum Drawdown Impact on Landholder Bores (Uncertainty
	Analysis, 95th percentile)	127
Table 7-1	Drawdown Impact on Landholder Bores (Base case scenario)	130
Table 7-2	Final Voids - Equilibrium Water Levels and Groundwater Levels	133
Table 7-3	Change in Rainfall for Different Climate Scenarios (2090)	135
Table 7-4	Final Voids - Equilibrium Water Levels - Climate Extremes	135
Table 8-1	Groundwater Monitoring Locations and Frequency	137

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BM Alliance Coal Operations Pty Ltd	11 December 2023
Blackwater Mine - North Extension Project	SLR Project No.: 620.014601.00006 R01

Figures in Text

Figure 1-1	Project Location	3
Figure 1-2	Project Indicative Mining Progression	4
Figure 2-1	Groundwater Management Areas and Chemistry Zones	16
Figure 3-1	Average Monthly Rainfall, Evapotranspiration and Evaporation at SILO Location
	(1970-2022)	19
Figure 3-2	Long-term Annual Rainfall	20
Figure 3-3	Monthly Rainfall and CRD	21
Figure 3-4	Monthly Rainfall at the BWM Site Station and SILO Data Location (2017-2018)
	.......................................................................................................................	21
Figure 3-5	Topography, Drainage and Water Plans	23
Figure 3-6	Average Daily Water Levels in Blackwater Creek D/S plotted against Daily
	Rainfall	24
Figure 3-7	Surrounding Land Uses	25
Figure 3-8	Surrounding Mines and CSG Projects	28
Figure 4-1	Surface Geology	32
Figure 4-2	Solid Geology	33
Figure 4-3	Geological Cross Section across the Study Area	34
Figure 4-4	Schematic Seam Stratigraphy and Split Diagram (BMA, 2014)	37
Figure 4-5	Local and Regional Faults	38
Figure 5-1	Groundwater Monitoring Network	44
Figure 5-2	Hydraulic Testing Data Locations	47
Figure 5-3	Faulting Conceptual Model Developed by Coffey (2014)	50
Figure 5-4	Standing Water Level in the Tertiary Sediment Bores	52
Figure 5-5	Standing Water Level in the Rewan Group	53
Figure 5-6	Standing Water Level in the Rangal Coal Measures, Northern Area	54
Figure 5-7	Standing Water Level in the Rangal Coal Measures, Bonnie Doon Area	55
Figure 5-8	Surveyed Water Level for Bonnie Doon Surface Water Storage Areas	56
Figure 5-9	Standing Water Level in the Rangal Coal Measures, near TSF	56
Figure 5-10	Standing Water Level in the Rangal Coal Measures, BWM Central	57
Figure 5-11	Standing Water Level in the Rangal Coal Measures - BWM South	58
Figure 5-12	Groundwater Level Contours in the Aries Seam and Pit Lake Elevations (March
	2023)	60
Figure 5-13	Standing Water Level in the Burngrove Formation	61
Figure 5-14	Groundwater Levels at VWP19BWM01 and CRD	62
Figure 5-15	Groundwater Level at VWP19BWM02P and CRD	63
Figure 5-16	Piper Plot - Tertiary Sediments	67

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BM Alliance Coal Operations Pty Ltd	11 December 2023
Blackwater Mine - North Extension Project	SLR Project No.: 620.014601.00006 R01
Figure 5-17	Electrical Conductivity (Field) - Tertiary Sediments	67
Figure 5-18	Field pH - Tertiary Sediments	68
Figure 5-19	Piper plot - Rewan Group	69
Figure 5-20	Electrical Conductivity (Field) - Rewan Group	69
Figure 5-21	Field pH - Rewan Group	70
Figure 5-22	Piper Diagram - Rangal Coal Measures (a. Bonnie Doon; b. South; c. North;
	and d. Central)	71
Figure 5-23	Field EC - Rangal Coal Measures (a. Bonnie Doon; b. South; c. North; and d.
	Central)	72
Figure 5-24	Field pH - Rangal Coal Measures (a. Bonnie Doon; b. South; c. North; and d.
	Central)	72
Figure 5-25	Piper Diagram - Burngrove Formation	73
Figure 5-26	Field EC - Burngrove Formation	74
Figure 5-27	Field pH - Burngrove Formation	74
Figure 5-28	Predicted Terrestrial Groundwater Dependent Ecosystems (BoM and DES
	Predictive Mapping)	79
Figure 5-29	Potential Terrestrial GDE Communities in the Project area (EMM, 2023)	80
Figure 5-30	Mapped Potential Aquatic GDEs in the Vicinity of the Project (BoM/DES)	82
Figure 5-31	Private Bores	85
Figure 5-32	Conceptual Hydrogeological Section of the Project Area and Surroundings....	88
Figure 5-33	Type A - Conceptual ecohydrological model - perched aquifers in alluvium (from
	RDM Hydro et al. 2023)	92
Figure 5-34	Type B - Conceptual ecohydrological model - perched aquifers in alluvium (from
	RDM Hydro et al., 2023)	93
Figure 5-35	Type C - Conceptual ecohydrological model - interaction with Tertiary and
	Permo-Triassic sediments perched aquifers - direct interaction between Coal
	Seams and alluvium (from RDM Hydro et al., 2023)	94
Figure 5-36	Type D - Conceptual ecohydrological model - interaction with Tertiary and
	Permo-Triassic sediments perched aquifers - indirect interaction between Coal
	Seams and alluvium (from RDM Hydro et al., 2023)	94
Figure 6-1	Model Domain, Watercourses and Mine Plan	96
Figure 6-2	Observed vs Computed Target Water Levels	102
Figure 6-3	Transient Calibration Average Head Residuals (m)	103
Figure 6-4	Modelled Depth to Water Table (m) End of Calibration (December 2022)	104
Figure 6-5	Estimated Hydraulic Conductivities vs Calibrated Hydraulic Conductivities ...	106
Figure 6-6	Predicted Cumulative (a) and Incremental (b) Mine Inflows	107
Figure 6-7	Maximum Incremental (a) and Cumulative (b) Drawdown in the Alluvium and
	Tertiary (Layer 1)	110
Figure 6-8	Maximum Incremental (a) and Cumulative (b) Drawdown in the Alluvium and
	Weathered Zone (Layer 2)	111

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BM Alliance Coal Operations Pty Ltd		11 December 2023
Blackwater Mine - North Extension Project	SLR Project No.: 620.014601.00006 R01
Figure 6-9	Maximum Incremental (a) and Cumulative (b) Drawdown in the Aries Seam
	(Layer 8)	112
Figure 6-10	Maximum Incremental (a) and Cumulative (b) Drawdown in the Pollux Seam
	(Layer 12)	113
Figure 6-11	Maximum Incremental (a) and Cumulative (b) Drawdown in the Burngrove
	Formation (Layer 14)	114
Figure 6-12	Indicative Final Void Locations	116
Figure 6-13	Predicted Project Final Void Water Level Recovery over Time	...................... 117
Figure 6-14	Groundwater Table Recovery (200 years Post-Mining)	118
Figure 6-15	Mine Inflow Predictive Uncertainty	119
Figure 6-16	Uncertainty in Predicted 1 m Maximum Incremental Drawdown in the Alluvium
	and Tertiary (Layer 1)	121
Figure 6-17	Uncertainty in Predicted 1 m Maximum Incremental Drawdown in the
	Weathered Zone (Layer 2)	122
Figure 6-18	Uncertainty in Predicted 1 m Maximum Incremental Drawdown in the Aries
	Seam (Layer 8)	123
Figure 6-19	Uncertainty in Predicted 1 m Maximum Incremental Drawdown in the Pollux
	Seam (Layer 12)	124
Figure 6-20	Uncertainty in Predicted 1 m Maximum Incremental Drawdown in the Burngrove
	Formation (Layer 14)	125
Figure 7-1	Potential for impacts to TGDE (EMM, 2023)	132

Appendices

Appendix A-1 Water Level Plots

Appendix A-2 Water Quality Summary Tables and Box-and-Whisker Plots Appendix A-3 Exisiting Water Supply Bores in the Study area / Bore Census Appendix A-4 Groundwater Bore Installation Report

Appendix B Groundwater Modelling Technical Report

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