Caroona Coal Project Application for Gateway Certificate Appendix C Preliminary Groundwater Assessment

CAROONA COAL PROJECT: GATEWAY APPLICATION PRELIMINARY GROUNDWATER ASSESSMENT

FOR

BHP BILLITON

C. Nicol, T. Liu and Dr N. P. Merrick

Heritage Computing Pty Ltd

trading as

HydroSimulations

Report: HC2013/25 Date: March 2014

EXECUTIVE SUMMARY

HydroSimulations has been engaged by Coal Mines Australia Pty Ltd (CMAL), a wholly owned subsidiary of BHP Billiton, to undertake a Preliminary Groundwater Assessment for the proposed Caroona Coal Project (the Project), for the purposes of assessment under the New South Wales (NSW) Government’s Gateway Application Process. A further groundwater assessment will be undertaken for the Environmental Impact Statement (EIS).

The Project is a proposed underground (longwall) coal mining operation targeting the Hoskissons Coal seam, with an operational life of approximately 30 years. The Project is located in the New England North West Region, approximately 40 kilometres (km) south east of Gunnedah in NSW. The Project area is located within Exploration Licence (EL) 6505.

Consistent with the requirements of the Strategic Regional Land Use Policy Guideline for Gateway Applicants (NSW Government, 2013) (Gateway Application Guidelines), the assessment relies on numerical modelling of potential risks of mine development in terms of the NSW Aquifer Interference (AI) Policy and Gateway Application requirements. This modelling was undertaken in consideration of the Murray-Darling Basin Commission (MDBC) Groundwater Flow Modelling Guideline (MDBC, 2001) and the relatively new National Guidelines, sponsored by the National Water Commission (Barnett et al., 2012).

A review of the data, literature and conceptual hydrogeology associated with other studies from the area and surrounds was carried out as a basis for model development. This was supported by a review of currently available information on geology, rock mass hydraulic properties, and strata geometry in the vicinity of the Project.

The complexity of the numerical groundwater model developed as part of this study is appropriate for this preliminary groundwater assessment by simulating contrasts in hydraulic properties and hydraulic gradients that may be associated with changes to the groundwater system as a result of the proposed development.

The AI Policy framework has been developed by the NSW Government to assist with the assessment and management of activities with potential to affect groundwater resources. The AI Policy framework has been developed by the NSW Office of Water (NOW) which identifies two Levels of minimal impact considerations, as described below:

 Level 1 impact, which is considered acceptable.

 Level 2 impact, which requires further studies to assess whether a project will prevent the long-term viability of a dependent ecosystem or significant site, or needs other arrangements to mitigate the impacts.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment i

Consistent with the Gateway Application Guidelines, this report assesses impacts on groundwater designated as ‘highly productive’ groundwater.

The key findings of the preliminary groundwater assessment with respect to NOW’s AI Policy are as follows:

 The Project meets the Level 1 Minimal Impact Considerations of the AI Policy for ‘highly productive’ groundwater associated with the Namoi Alluvium (i.e. Upper and Lower Namoi Groundwater Sources), and with the Liverpool Range Basalts (i.e. NSW Murray Darling Basin Fractured Rock Groundwater Sources [Liverpool Ranges Basalt MDB]).

 The Project triggers the Level 2 Minimal Impact Considerations of the AI Policy for the ‘highly productive’ Jurassic NSW Murray Darling Basin Porous Rock Groundwater Sources (Gunnedah-Oxley Basin MDB [Spring Ridge]). This is due to a model estimation of more than 2 metres (m) cumulative drawdown at 27 water supply works.

Consistent with the findings of the Namoi Catchment Water Study, BHP Billiton has committed to “make good” provisions for any groundwater users adversely affected by mine operations and associated impacts – i.e. provision of alternative water supply or remedial works (e.g. deepening of existing wells or bores). A Groundwater Management Plan will be developed prior to the commencement of longwall mining to define groundwater level triggers, including a Trigger Action Response Plan, and appropriate management responses and mitigation measures.

The impact assessment presented in this preliminary groundwater assessment will be refined as part of the groundwater assessment to accompany the Project EIS. As part of the Gateway Assessment, a number of bores were inspected to confirm their location, hydrogeological characteristics and usage (i.e. a bore census). BHP Billiton will conduct a second stage of the bore census in consultation with relevant landholders to confirm the status, location and details of the bores not yet inspected in order to inform further impact assessment work planned for the EIS.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment ii

DOCUMENT REGISTER

Revision Description Date

1 Preliminary draft. Data analysis section only. 05/12/2013

Draft for internal and external review. Completed Sections 3 through 8 2 12/01/2014 (model build, calibration and predictions). Draft for external review. Completed Section 2, added predictive 3 24/01/2014 sensitivity, revised sections 4 through 8 (model predictions).

4 Incorporated BHP/Resource Strategies/preliminary Frans Kalf comments. 16/02/2014

5 Final Draft. Incorporated BHP/Resource Strategies/Frans Kalf comments. 03/03/2014

6 Final. Incorporated BHP/Resource Strategies comments. 18/03/2014

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment iii

TABLE OF CONTENTS

EXECUTIVE SUMMARY ...... I 1 INTRODUCTION ...... 1

1.1 NATURE OF THE PROJECT ...... 1

1.2 SCOPE OF WORK ...... 3

1.3 WATER REGULATION ...... 4

1.4 APPROACH TO THE GATEWAY PROCESS ...... 6

1.5 NAMOI CATCHMENT WATER STUDY ...... 7

2 HYDROGEOLOGICAL SETTING AND CONCEPTUALISATION ...... 12

2.1 TOPOGRAPHY ...... 12

2.2 RAINFALL AND EVAPORATION ...... 12

2.3 SURFACE DRAINAGE ...... 15

2.4 GEOLOGY...... 16

2.5 NEARBY MINES AND PROJECTS ...... 18

2.6 GROUNDWATER OCCURRENCE AND FLOW SYSTEMS ...... 18

2.6.1 Groundwater Monitoring ...... 21

2.6.2 Groundwater Recharge ...... 31

2.6.3 Groundwater Use ...... 32

2.6.4 Groundwater Quality ...... 32

2.6.4.1 Salinity ...... 32

2.6.4.2 pH ...... 35

2.6.5 Hydraulic Properties...... 36

2.6.5.1 Hydraulic Conductivity (K)...... 38

2.6.5.2 Specific Yield ...... 41

2.6.5.3 Specific Storage...... 41

2.6.6 Groundwater-Surface Water Interaction...... 42

2.7 CONCEPTUAL HYDROGEOLOGICAL MODEL ...... 43

2.7.1 Hydrostratigraphic Units ...... 43

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment iv

2.7.2 Recharge ...... 43

2.7.3 Discharge ...... 43

2.7.4 Hydraulic Properties...... 44

2.7.5 Impact of Mining on Overburden ...... 44

2.7.6 Water Balance Changes Due to Mining ...... 45

3 GROUNDWATER SIMULATION MODEL ...... 68

3.1 MODEL SOFTWARE AND COMPLEXITY ...... 68

3.2 MODEL LAYERS AND GEOMETRY ...... 69

3.3 BOUNDARY CONDITIONS ...... 71

3.3.1 Watercourses ...... 71

3.3.2 Recharge ...... 72

3.3.3 Evapotranspiration ...... 72

3.3.4 Groundwater Use ...... 72

3.3.5 No Flow Boundaries ...... 73

3.3.6 Mine Workings ...... 73

3.4 HYDRAULIC PROPERTIES ...... 73

3.5 MODEL VARIANTS ...... 76

3.6 CALIBRATION ...... 76

3.6.1 Approach ...... 76

3.6.2 Results ...... 78

3.6.3 Calibrated Model Water Balances ...... 79

3.7 CALIBRATED MODEL PARAMETERS ...... 80

3.7.1 Calibration Sensitivity Analysis ...... 82

4 PREDICTIVE MODELLING ...... 90

4.1 MODEL IMPLEMENTATION ...... 90

4.1.1 Fractured Zone Implementation ...... 90

4.2 MINE SCHEDULE ...... 94

4.3 IMPACT ASSESSMENT APPROACH ...... 94

4.4 SIMULATED MINE INFLOWS ...... 95

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment v

5 POTENTIAL IMPACTS ...... 98

5.1 FRAMEWORK FOR ASSESSMENT ...... 98

5.2 POTENTIAL CHANGES IN BASEFLOW TO THE MOOKI RIVER ...... 98

5.3 GROUNDWATER LEVELS ...... 98

5.4 EXISTING GROUNDWATER USERS ...... 99

5.5 CULTURALLY SIGNIFICANT SITES ...... 104

5.6 GROUNDWATER DEPENDENT ECOSYSTEMS ...... 104

5.7 POTENTIAL IMPACTS ON GROUNDWATER QUALITY ...... 104

5.8 OTHER EFFECTS OF MINING ...... 105

5.9 SUMMARY OF ASSESSMENT IN TERMS OF THE AI POLICY ...... 105

6 PREDICTIVE MODEL SENSITIVITY ANALYSIS ...... 117

6.1 MODELLED MINE INFLOW SENSITIVITY ...... 117

6.2 MODELLED DRAWDOWN SENSITIVITY ...... 118

7 LICENSABLE WATER TAKES ...... 119 8 CONCLUSIONS ...... 122

8.1 RECOMMENDATIONS FOR FUTURE WORK ...... 124

9 BIBLIOGRAPHY ...... 126

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment vi

LIST OF FIGURES

Figure 1 Project Location ...... 8 Figure 2 Relevant Water Sharing Plans ...... 9 Figure 3 Biophysical Strategic Agricultural Land ...... 10 Figure 4 Highly Productive Groundwater ...... 11 Figure 5 Average Annual Rainfall 1961-1990 ...... 46 Figure 6 Annual Rainfall Cumulative Distribution Function for Station 055039 at Spring Ridge from 1922 to 2013 ...... 47 Figure 7 Climate Summary ...... 48 Figure 8 Stream Gauging Stations ...... 49 Figure 9 Stream Flow Exceedance Curves for the Mooki River (May 1979-August 2013) 50 Figure 10 Geological Basins of New South Wales ...... 51 Figure 11 Geological Outcrop ...... 52 Figure 12 Stratigraphy ...... 53 Figure 13 Interpolated Watertable Elevation (February 2010) ...... 54 Figure 14 Interpolated Watertable Depth (February 2010) ...... 55 Figure 15 Potentiometric Head Cross-Sections for September 2009 ...... 56 Figure 16 Existing Groundwater Monitoring Bores ...... 57 Figure 17 Estimated Historical Alluvial Groundwater Use ...... 58 Figure 18 Regional Groundwater TDS Data Summary (from AGE, 2013) ...... 59 Figure 19 Monitoring sites with permeability test method (from AGE, 2013) ...... 60 Figure 20 Coal seam hydraulic conductivity (from AGE, 2013) ...... 61 Figure 21 Summary of Clare Sandstone hydraulic conductivity (from AGE, 2013 and SCT, 2012) 62 Figure 22 Summary of Interburden hydraulic conductivity (from AGE, 2013 and SCT, 2012) 63 Figure 23 Mooki River Flow Gains and Losses between Caroona and Breeza ...... 64 Figure 24 Groundwater Surface Water Interaction at Lower Quirindi Creek ...... 65 Figure 25 Conceptual Hydrogeological Model ...... 66 Figure 26 Conceptual Model of Longwall Mining-Induced Rock Deformation ...... 67 Figure 27 Model Grid and Boundary Conditions ...... 83 Figure 28 Representative Model Cross-Section ...... 84 Figure 29 Subsidence Control Zones ...... 85 Figure 30 Summary of Steady State Model Calibration ...... 86 Figure 31 Summary of Transient Model Verification ...... 87 Figure 32 Spatial Calibration Error and Modelled Potentiometric Contours ...... 88 Figure 33 Calibrated Model Parameter Sensitivities ...... 89 Figure 34 Modelled Mine Schedule ...... 96 Figure 35 Modelled Mine Groundwater Inflows ...... 97 Figure 36 Modelled Mooki River Baseflow Impacts ...... 111 Figure 37 Simulated Drawdown and Recovery – Model Layers 1 and 2 ...... 112 Figure 38 Simulated Drawdown and Recovery – Model Layers 3 and 4 ...... 113 Figure 39 Simulated Drawdown and Recovery – Model Layers 5 and 6 ...... 114 Figure 40 Simulated Drawdown and Recovery – Model Layers 7 and 8 ...... 115 Figure 41 Simulated Drawdown and Recovery – Model Layer 9 ...... 116

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment vii

LIST OF TABLES

Table 1 Gateway Process Requirements ...... 4 Table 2 Relevant Water Sharing Plans and Water Sources ...... 5 Table 3 Gateway Process Preliminary Groundwater Assessment - Modelling Approach 7 Table 4 Average and median annual rainfall at Australian Bureau of Meteorology stations in the regional area...... 13 Table 5 Annual Rainfall Statistics at Spring Ridge (Station No. 055039) from 1922 to 2013 13 Table 6 Project Rainfall Gauge Data ...... 14 Table 7 Average pan evaporation ...... 14 Table 8 Stream Flow Gauging Stations ...... 16 Table 9 Groundwater Yield and Salinity Summary ...... 20 Table 10 Bore Construction Details – NOW bores ...... 22 Table 11 Bore Construction Details - Piezometer bores ...... 23 Table 12 Bore Construction Details - Vibrating Wire Piezometers ...... 26 Table 13 Summary of Groundwater Chemistry - Groundwater Monitoring Piezometers ...... 34 Table 14 Summary of Hydraulic Property Testing ...... 37 Table 15 Core Hydraulic Conductivity Data Summary from the Watermark Project 40 Table 16 Core Hydraulic Conductivity Data from the Watermark Project ...... 40 Table 17 Model Layer Assignment...... 69 Table 18 Initial Hydraulic Properties of Hydrostratigraphic Units ...... 75 Table 19 Transient Verification Data Summary ...... 77 Table 20 Calibrated Steady State Water Balance ...... 79 Table 21 Calibrated Transient Water Balance ...... 79 Table 22 Comparison of Calibrated and Initial Hydraulic Properties of Hydrostratigraphic Units ...... 81 Table 23 Modelled Hydraulic Properties within the Fractured Zone ...... 92 Table 24 Modelled Hydraulic Properties within the Fractured Zone (Subsidence Control Zones) ...... 93 Table 25 Predictive Model Time Discretisation ...... 94 Table 26 Summary of Simulated Groundwater Bore Drawdowns ...... 101 Table 27 Modelled Drawdown at Registered Groundwater Bores in ‘Highly Productive’ Water Sources ...... 102 Table 28 Modelled Drawdown at Groundwater Bores in ‘Highly Productive’ Water Sources Identified in the Project Bore Census ...... 103 Table 29 Summary of AI Policy Assessment – Namoi Alluvium...... 107 Table 30 Summary of AI Policy Assessment – Liverpool Range Basalt ...... 107 Table 31 Summary of AI Policy Assessment – Jurassic Porous Rock ...... 109 Table 32 Summary of AI Policy Assessment – Permo-Triassic Porous Rock ...... 110 Table 33 Project Groundwater Licensing Summary ...... 120 Table 34 Modelled Water Takes from each Namoi Alluvium Zone ...... 121 Table 35 Proposed Scope for a Full Environmental Impact Assessment ...... 125

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment viii

LIST OF ATTACHMENTS

Attachment A IESC Information Requirements

Attachment B Modelled Geological Surfaces

Attachment C Hydraulic Property Zonation

Attachment D Verification Hydrographs

Attachment E Modelled Drawdowns – Sensitivity Run #1

Attachment F Australian Groundwater Modelling Guidelines - Model confidence level classification

Attachment G Modelled Drawdowns at Registered Bores in ‘Less Productive’ Water Sources within BSAL

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment ix

1 INTRODUCTION

The Gateway Process requires a preliminary assessment of risks of the Project on groundwater resources. A broader groundwater assessment will be included in the Project Environmental Impact Statement (EIS). Given that this Gateway Application will be referred to the Independent Expert Scientific Committee (IESC), Attachment A provides a tabulation of where each of the IESC’s information requirements is addressed.

The Project is a proposed underground coal mining operation with an operational life of approximately 30 years. The Project is located in the New England North West Region, approximately 40 kilometres (km) south east of Gunnedah in NSW (refer to Figure 1). The Project is located within Exploration Licence (EL) 6505.

BHP Billiton plans to seek Development Consent from the NSW Minister for Planning and Infrastructure under Division 4.1 of Part 4 of the NSW Environmental Planning and Assessment Act 1979 (EP&A Act).

1.1 NATURE OF THE PROJECT

The key components of the proposed Project comprise:

 an underground mining operation within EL 6505 involving a single longwall in the Hoskissons Seam on Doona Ridge and a second longwall in the Hoskissons Seam on Nicholas Ridge;

 production of approximately 260 million tonnes (Mt) of run-of-mine (ROM) coal over the life of the mine;

 production of up to approximately 10 Mtpa (million tonnes per annum) of saleable thermal coal;

 a mine life of approximately 30 years;

 development and operation of a pit top mine infrastructure area comprising administration offices, bathhouse, workshop, store, coal stockpile areas, coal handling infrastructure, bunded hydrocarbon tanks, laydown areas, car parking, electrical substation, muster area, associated linear infrastructure and access road on Doona Ridge;

 development and operation of a separate men and materials shaft on Doona Ridge;

 construction and operation of an event Coal Preparation Plant (CPP) (1 Mtpa ROM coal capacity) on Doona Ridge for washing of occasional high-ash ROM coal;

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 1

 construction and operation of a coal unloading facility on Doona Ridge to allow transportation of Nicholas Ridge ROM coal to Doona Ridge via rail for washing;

 co-disposal of fine and coarse rejects in an emplacement on Doona Ridge, with rejects to be transported within an infrastructure corridor;

 development and operation of a separate pit top mine infrastructure area comprising coal handling infrastructure, coal stockpiles, an access road, car parking, administration offices, muster area, electrical substation and associated linear infrastructure on Nicholas Ridge;

 relocation of Rossmar Park Road;

 construction and operation of separate rail loops and spurs to connect to the Binnaway-Werris Creek Railway from Doona Ridge and Nicholas Ridge;

 employment of up to approximately 400 operational personnel at peak production;

 employment of an average number of construction employees of approximately 400 and up to 600 at peak construction;

 emplacement of overburden excavated during the construction of access drifts and shafts;

 progressive development of sumps, pumps, pipelines, water storages and other water management equipment and structures (including dewatering infrastructure);

 development and operation of ventilation surface infrastructure and gas drainage infrastructure;

 development and operation of water and gas pipelines to connect the Nicholas Ridge infrastructure area to the Doona Ridge infrastructure area;

 ongoing exploration activities within EL 6505;

 ongoing surface monitoring and rehabilitation (including rehabilitation of mine related infrastructure areas that are no longer required) and remediation of subsidence effects; and

 other associated minor infrastructure, plant, equipment and activities.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 2

1.2 SCOPE OF WORK

The key tasks for this assessment are:

 data analysis and conceptualisation of the groundwater system, including assessment of hydrostratigraphic units (HSU) and their properties, and groundwater recharge and discharge;

 development of a lower resolution regional-scale 3-dimensional numerical groundwater flow model based on data analysis and conceptual model development;

 steady state model calibration to observed groundwater level data, using a single zone of uniform parameters for each hydrostratigraphic unit;

 transient model verification against observed groundwater level data;

 transient prediction for the 30 year mine plan using lower temporal resolution of the extraction schedule, followed by simulation of the post- mining recovery period; and

 preparation of this Preliminary Groundwater Assessment report for inclusion in the Gateway Application documents that includes assessment of potential groundwater impacts of the Project and, where applicable, cumulative impacts with other existing and approved mines in the area associated with the development.

This assessment will focus on the criteria specified by the NSW Aquifer Interference (AI) Policy and the requirements of the Strategic Regional Land Use Policy Guideline for Gateway Applicants (NSW Government, 2013) outlined in Table 1.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 3

Table 1 Gateway Process Requirements

Requirement Section Reference

Estimates of all quantities of water that are likely to be taken from any water source on an annual basis during and following cessation of the Section 7 activity; A strategy for obtaining appropriate water licence/s for maximum Section 7 predicted annual take; Establishment of baseline groundwater conditions including groundwater depth, quality and flow based on sampling of all existing bores in the area potentially affected by the activity, any existing monitoring bores and any Section 2 new monitoring bores that may be required under an authorization under the Mining Act 1992 or the Petroleum (Onshore) Act 1991; A strategy for complying with any water access rules applying to relevant categories of water access licences, as specified in relevant water sharing Section 7 plans; Estimates of potential water quality, level, or pressure drawdown impacts on nearby water users who are exercising their right to take water under Section 5.5 a basic landholder right; Estimates of potential water level, quality or pressure drawdown impacts on nearby licensed water users in connected groundwater and surface Section 5.5 and 5.2 water sources; Estimates of potential water level, quality or pressure drawdown impacts Section 5.6 on groundwater dependent ecosystems; Estimates of potential for increased saline or contaminated water inflows Section 5.7 to aquifers and highly connected river systems; Estimates of the potential to cause or enhance hydraulic connection Sections 2.7, 4.1.1, 5.4, 5.7 between aquifers; and 7 Estimates of the potential for river bank instability, or high wall instability Refer to MSEC (2014) or failure to occur; Outline of the method for disposing of extracted water (in the case of Not Applicable coal seam gas activities). Assess the project against the criteria specified in ‘Table 1 – Minimal Impact Considerations for Aquifer Interference Activities’ in the Aquifer Section 5.9 Interference Policy. Source: NSW Government (2013)

1.3 WATER REGULATION

The NSW Office of Water (NOW) implements water regulation according to the Water Management Act 2000, a primary objective of which is to facilitate the sustainable management and use of water resources, balancing environmental, social and economic considerations.

NOW is in the process of developing Water Sharing Plans (WSPs) throughout the State, which establish rules for sharing and trading both groundwater and surface water between competing needs and users.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 4

The relevant WSPs and the associated water sources for the Project are outlined in Table 2 and shown in Figure 2. The NSW AI Policy is designed to provide a framework for the assessment of impacts of the taking of water under a proposed development. The AI Policy divides groundwater sources into “highly productive” and “less productive” categories based on salinity and groundwater yield, which are also shown in Table 2.

Table 2 Relevant Water Sharing Plans and Water Sources

Water Sharing Plan Water Source Productivity

Upper and Lower Namoi Groundwater Namoi alluvium (Narrabri Fm and Highly Productive Sources 2003 Gunnedah Fm)

NSW Murray Darling Basin Fractured Liverpool Ranges Basalt Highly Productive Rock Groundwater Sources 2011

NSW Murray Darling Basin Porous Rock Jurassic units (Pilliga Sandstone, Groundwater Sources 2011, Gunnedah- Purlawaugh Fm , Garrawilla Highly Productive Oxley Basin MDB (Spring Ridge) Volcanics) Management Zone

NSW Murray Darling Basin Porous Rock Triassic to Permian units (Napperby Groundwater Sources 2011, Gunnedah- Fm, Digby Fm, Blackjack Group and Less Productive Oxley Basin MDB (Other) Management Permian strata) Zone

Note: The Gunnedah–Oxley Basin MDB (Spring Ridge) Management Zone is also separated vertically from the Gunnedah–Oxley Basin MDB (Other) Management Zone, which is not displayed on the Plan Map (refer to Figure 2). Fm: Formation

The AI Policy also specifies ‘minimal impact considerations’ for both highly productive and less productive groundwater zones (Figure 4); these comprise thresholds for watertable and groundwater pressure drawdown, and changes in groundwater and surface water quality. Different minimal impact considerations are specified for highly productive and less productive groundwater zones for:

 Water supply works;

 Listed Groundwater Dependent Ecosystems (GDEs); and

 Culturally significant sites.

The AI Policy framework identifies two levels of minimal impact considerations, as described below:

 Level 1 impact, which is considered acceptable.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 5

1.4 APPROACH TO THE GATEWAY PROCESS

Under the Gateway process, the AI Policy requires estimation of all water takes and impacts during and following cessation of the proposed activity based on a "simple modelling platform" that the Minister determines to be "fit-for-purpose", based on appropriate baseline data. In this report the model is referred as a ‘lower resolution model’ that uses well established numerical simulation procedures.

It is clear from the AI Policy that a risk management approach should be adopted. That is to say, the level of effort in the assessment should be proportional to the likelihood of impacts and the potential consequences of those impacts.

However, some of the other reasons why the groundwater assessment for the Gateway process is only intended to be preliminary include:

 The preliminary groundwater assessment will not have the benefit of information usually provided by associated disciplines (especially surface water hydrology, geochemistry and ecology studies). However it should be noted that some analysis of surface water hydrology has been conducted for this study, primarily in the context of groundwater-surface water interaction.

 Often the available data for hydrogeological conceptualisation and model calibration would be limited; although in this case there is, generally, an extensive dataset.

 There is a limited 90 day period for assessment by the Gateway Panel, who must obtain the advice of the Minister for Primary Industries and the IESC within that period of time.

 There is to be no public consultation or exhibition of submitted documents.

In combination, the above constraints lead to the conclusion that it would be inappropriate to offer the same level of detail and effort that is normally expended in an EIS. Nevertheless, and fortunately for this project, there is already a considerable amount of surface water and geochemical data that is normally only available for an EIS. This was included in the assessment presented herein. Our approach to the modelling for this preliminary groundwater assessment for the Gateway Process is outlined in Table 3.

Consultation with the NOW with regard to the level of detail proposed for the Preliminary Groundwater Assessment has been undertaken. NOW indicated that they were generally satisfied with the proposed approach.

Biophysical Strategic Agricultural Land mapped by the NSW Government and highly productive groundwater is shown on Figures 3 and 4, respectively.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 6

Table 3 Gateway Process Preliminary Groundwater Assessment - Modelling Approach

MODEL FEATURE APPROACH Spatial Scale Coarse (uniform 400 m grid cell size) Coarse (annual or greater stress period durations in the Temporal Scale predictive model) Model Extent 70 km x 97.6 km Stratigraphy 9 Layers Spatial Parameter Variability No Steady-State Calibration Yes Transient Calibration No (verification only) Prediction 30 years Fractured Zone Yes Tracking of Headings Limited to none Sensitivity Analysis Limited Uncertainty Analysis No Recovery Analysis Yes Cumulative Assessment Law of Superposition Climate Change No Mitigation Measures If required Monitoring Program Yes Outputs Focused on AI Policy Licensing Volumes Provisional Software MODFLOW-SURFACT Report Condensed

1.5 NAMOI CATCHMENT WATER STUDY

The Namoi Catchment Water Study was undertaken between 2008 and 2012 by Schlumberger Water Services (SWS) (2012). The Minister for Mineral Resources appointed a Ministerial Oversight Committee to steer the water study. The study involved the development of numerical models which were used to review risks on key water resources in the Namoi Catchment associated with coal mining and coal seam gas extraction (Namoi Catchment Water Study, 2014).

The study consisted of a series of interim reports (Phase reports) and a final report in 2012. The study is considered to be a key reference for the Project groundwater assessment, and consistent with BHP Billiton’s commitment to incorporate the findings of the report, has been frequently referred to during the production of this report.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 7

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Pheasant Uhrs Creek Gully Station Gully 6470000 Legend BHP Billiton ") Town Topography Targeted Exploration Area Caroona Coal Project mAHD )" Village Exploration Licence 221.9 - 300 Figure 1 ") Locality 300.1 - 400 River 400.1 - 500 Project Location Creek 500.1 - 750 DrawingNo: CAR001-001 Waterbody Scale: 480,000 @A4 Rev: C. GDA 1994 MGA Zone 56 750.1 - 1,494.6 Created by: CNicol ° ° Date: 10/02/2014. (C) 2014. While HydroSimulations has taken care to ensure the accuracy of this product, HydroSimulations, Geoscience Australia and NSW Government make no representations or 02.75 5.5 11 16.5 22 warranties about its accuracy, completeness or suitability for any particular purpose and km cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses,

D:\HydroSim\CAR001\GIS\Maps\Deliverable\001_Project Location.mxd 220000 230000 240000 250000 260000 270000 280000 ") 290000 300000 )" CARROLL ") Zone 4 ") Town

PORCUPINE LOOKOUT 6570000 ") GUNNEDAH )" Village ") Locality

WINTON ") River

Creek 6560000 BITHRAMERE CURLEWIS Zone 3 ") MILROY ") Murray Darling ") Basin boundary PIALLAWAY ") Exploration

Licence 6550000 Targeted Exploration Area

BREEZA CURRABUBULA ") )" ")BELGAMBA 6540000

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BURILDA Zone 8 ") WERRIS CREEK ")

BAKANA 6530000 ") ") NARDU TURILAWA ")

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PINE RIDGE )" BORAMBIL ") ") QUIRINDI Black Spring (! 6510000 COOMOO COOMOO ") ") Zone 1

Zone 6 WARRAH RIDGE ") YARRAMAN ") THE SEVEN MILE ") WINDY ") Zone 10 BLACKVILLE WILLOW TREE 6500000 ") ")

OLD WARRAHWARRAH ") ") KANKOOL ")

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") 6480000 6470000 NSW Murray Darling Basin NSW Murray Darling Basin Water Sharing Plan for the Porous Rock Groundwater Fractured Rock Groundwater Upper and Lower Namoi BHP Billiton Sources 2011 Sources 2011 Groundwater Sources 2003 Caroona Coal Project Gunnedah-Oxley Basin Liverpool Ranges Basalt Groundwater MDB (Other) MDB Management Zones Figure 2 Gunnedah-Oxley Basin New England Fold Belt Excluded Alluvial MDB (Spring Ridge) MDB Relevant Water Sharing Plans Sydney Basin MDB (! High Priority GDEs (Macquarie Oxley) (Fractured Rocks) DrawingNo: CAR001-002 Scale: 480,000 @A4 High Priority GDEs Rev: C. Created by: CNicol GDA 1994 MGA Zone 56 )" (Porous Rocks) ° ° Date: 10/02/2014.

(C) 2013. While HydroSimulations has taken care to ensure the accuracy of this product, HydroSimulations, Geoscience Australia and NSW Government make no representations or 02.5 5 10 15 20 warranties about its accuracy, completeness or suitability for any particular purpose and km cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses,

D:\HydroSim\CAR001\GIS\Maps\Deliverable\002_Water Sharing Plans_V2.mxd

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Pheasant Uhrs Creek Gully Station Gully 6470000 Legend BHP Billiton ") Town Targeted Exploration Caroona Coal Project

" ) Village Exploration Licence Figure 3 ") Locality Biophysical Strategic Agricultural Land as shown in Biophysical Strategic River the New England North-West Agricultural Land Creek SRLUP DrawingNo: CAR001-010 Scale: 480,000 @ A4 Rev: B. GDA 1994 MGA Zone 56 Created by: CNicol ° ° Date: 10/02/2014. (C) 2014. While HydroSimulations has taken care to ensure the accuracy of this product, HydroSimulations, Geoscience Australia and NSW Government make no representations or 02.75 5.5 11 16.5 22 warranties about its accuracy, completeness or suitability for any particular purpose and km cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses,

D:\HydroSim\CAR001\GIS\Maps\Deliverable\010_BSAL.mxd 220000 230000 240000 250000 260000 270000 280000 ") 290000 300000 )" CARROLL ")

PORCUPINE LOOKOUT 6570000 ") GUNNEDAH

WINTON ") 6560000

BITHRAMERE CURLEWIS ") MILROY ") ")

PIALLAWAY ") 6550000

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") 6480000 6470000 BHP Billiton Legend Caroona Coal Project ") Town Murray Darling Basin boundary Groundwater Productivity )" Village Exploration Licence Highly Productive Figure 4 ") Locality Targeted Exploration Area Less Productive Highly Productive River Groundwater Creek DrawingNo: CAR001-011 Rev: B. Scale: 480,000 @A4 Created by: CNicol ° GDA 1994 MGA Zone° 56 Date: 10/02/2014.

D:\HydroSim\CAR001\GIS\Maps\Deliverable\011_Groundwater Productivity.mxd

2 HYDROGEOLOGICAL SETTING AND CONCEPTUALISATION

2.1 TOPOGRAPHY

The Project EL6505 lies within the upper Namoi Catchment of the Liverpool Plains. Land surface elevation ranges from 1,500 mAHD (metres above Australian Height Datum) on the Liverpool Ranges in the south down to approximately 265 mAHD near Gunnedah in the north (Figure 1). Drainage is broadly from south to north, with alluvial plains becoming significantly broader to the north as topography flattens out.

Within EL6505, elevation ranges from 300 to 350 mAHD in the south and decreases to around 270 mAHD in the north (Figure 1). Topography in the lease is characterised by Doona Ridge, a north-south trending area of elevated and gently sloping land, which is surrounded by flat to undulating areas of alluvial plain. To the east, the flat topography is disrupted by Nicholas Ridge, a small area of elevated and gently sloping land. Another north-south trending ridge, Spring Ridge, defines the western lease margin. Elevated land also occurs to the south of the lease, which covers a much broader regional area.

2.2 RAINFALL AND EVAPORATION

Climatic data are or have historically been collected by the Bureau of Meteorology (BoM) at a number of monitoring stations throughout the Project area and surrounds (Figure 5). The BoM have interpolated average annual rainfall throughout the area, which is presented in Figure 5. Useful stations near or within the lease are at Spring Ridge (Station No. 055039; 5 km from EL6505), Pine Ridge (Mooki Springs) (Station No. 055037; 6.5 km from EL6505), and Pine Ridge (Billabong) (Station No. 055046; 8.5 km from EL6505). Long-term average annual rainfall at these gauges is approximately 600 millimetres (mm) (Table 4).

The BoM mapping suggests a strong topographic control on average annual rainfall, with up to 1,000 millimetres (mm)/year rainfall in the Liverpool Ranges to the south, and less than 650 mm/year along the lower parts of the catchment and valleys (Figure 5).

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 12

Table 4 Average and median annual rainfall at Australian Bureau of Meteorology stations in the regional area.

Average Median Easting Northing Station Period of Annual Annual Elevation Station Name (mMGA (mMGA Number Record Rainfall Rainfall (mAHD) zone 56) zone 56) (mm) (mm) 1922 to Spring Ridge 055039 599 493.5 238496.6 6523905 314 current Pine Ridge 1886 to 055037 595 484.5 253080.3 6510946 335 (Mooki Springs) 2012 Pine Ridge 1921 to 055046 594.5 474.9 256932.1 6508817 340 (Billabong) current

The range of annual rainfall percentiles for Spring Ridge is shown in Table 5 and Figure 6. The median (50th percentile) of 589 mm is close to the long-term average (599 mm).

Table 5 Annual Rainfall Statistics at Spring Ridge (Station No. 055039) from 1922 to 2013

Percentile 10 20 25 50 75 80 90 Annual Rain(mm) 366 448 481 589 701 786 834

Average monthly rainfall and cumulative deviation from mean rainfall (i.e. the ‘residual mass curve’) for Spring Ridge station 055039 from 1922 to 2013, are shown in Figure 7. Rainfall is highest between the months of October and February (60-80 mm/month), and remain relatively constant between March and September, hovering around 40 mm/month.

The residual mass curve of Figure 7 indicates when rainfall is generally above or below average, with a rising trend indicating an extended period of above average rainfall (when groundwater recharge is likely to be higher) while a downward trend indicates a period of below average rainfall accumulation (when recharge is likely to be lower). Figure 7 indicates the first extended dry period from 1922 to 1948 followed by wet and dry cycles that have occurred between 1948 and 1968. Since 1968 the area has generally observed above average rainfalls, with only a few periods of below average rainfall, such as around 1978-84, 1995-1997, and in the early to mid-2000s.

A meteorological monitoring station was installed at the Project in 2007 (located at easting 254494 / northing 6525314 (GDA94 zone 56)), which uses both a traditional tipping bucket gauge (1/7/2007 to current), and, more recently, a Vasala sensor (20/6/2013 to current). The Vasala sensor’s period of record is currently too short for meaningful analysis, however monthly averages from the tipping bucket gauge between December 2008 and May 2013 are provided in Table 6 and compared to the corresponding average monthly rainfall for BoM Spring Ridge station 055039.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 13

Table 6 Project Rainfall Gauge Data

Average Monthly Rainfall Month Project (mm) Spring Ridge (mm) January 72 58 February 76 91 March 36 68 April 28 29 May 31 36 June 28 26 July 22 40 August 11 13 September 41 53 October 27 36 November 92 88 December 69 42

The closest BoM climate monitoring station to the Project area that collects evaporation data is the Gunnedah Resource Centre (Station No. 055024), located approximately 40 km north-west of the Project. Data collected between 1948 and 2013 indicates an average annual potential evaporation of approximately 1752 mm for the area. Spatially interpolated BoM average annual and monthly pan evaporation data have been used to estimate pan evaporation for the Project lease, which is presented in Table 7.

Table 7 Average pan evaporation

Average Monthly Pan Evaporation (mm) Month Gunnedah Resource Centre BoM Mapping (EL6505) (Station 055024) January 300 238.7 February 250 187.6 March 300 186 April 150 129 May 100 83.7 June 60 57 July 80 58.9 August 100 86.8 September 150 120 October 200 164.3 November 250 198 December 300 238.7 ANNUAL 2,000 1,752 Number of Years 10 (minimum) 66 Start Year 1,975 1,948 End Year 2,005 2,013 Elevation (mAHD) 313 307 Note: Annual values are not the same as the sum of the monthly values.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 14

The actual evapotranspiration (ET) in EL6505 is about 580-600 mm per annum according to BoM (2013). The definition for actual ET is: “... the ET that actually takes place, under the condition of existing water supply, from an area so large that the effects of any upwind boundary transitions are negligible and local variations are integrated to an areal average. For example, this represents the evapotranspiration which would occur over a large area of land under existing (mean) rainfall conditions.”

A comparison between average monthly rainfall at Spring Ridge (Station 055039) and average monthly potential evaporation at Gunnedah Resource Centre (Station 055024) shows that, on average, the area has an excess evaporative capacity over rainfall in all months (Figure 7).

2.3 SURFACE DRAINAGE

The Project area is located in the upper Namoi River catchment of the Murray Darling Basin. The primary drainage channel in the Project area is the Mooki River, which flows from south to north within EL6505, and joins the Namoi River to the north, at Gunnedah (Figure 1). The Mooki River’s headwaters originate from the Liverpool Ranges situated some 45 km south of EL6505 near the Project area southern boundary (Figure 1). Major tributaries that enter east of the Mooki River, from south to north include: Warrah Creek, Quirindi Creek and Werris Creek. The latter two streams originate in the Melville Ranges (Figure 1).

Tributaries flowing from the west are few, and are chacterised by sheet wash (overland flow) with limited channel definition in their lower reaches (Figure 1). This overland flow drains to the Mooki River via Lake Goran and / or Native Dog Gully, which runs west to east along the northern EL6505 boundary. This suggests that their stream flow is ephemeral. Yarraman Creek channel is one of these poorly defined western tributary channels, which enters and extends along the western edge of EL6505.

The Australian Government’s Directory of Important Wetlands (http://www.environment.gov.au/cgi-bin/wetlands/report.pl?smode=DOIW;doiw_ refcodelist=NSW005) states that Lake Goran is an internally draining system that has been modified since the 1970s. Yarraman Creek and Coomoo Coomoo Creek have been artificially diverted into the lake, whereas they once ultimately discharged via sheet flow into the Mooki River. The directory also states that less than 10% of the lake area is regularly waterlogged, and that much of the lake bed is used for cropping most of the time.

Figure 8 shows the locations of five relevant NOW stream gauging stations. Gauging station details are shown in Table 8. Stream flow exceedance statistics for the May 1979 through August 2013 period for the Mooki River gauges are presented in Figure 9. This figure indicates that when Mooki River flows are in the higher range (greater than approximately 50 ML/day) the flows in the river at the Breeza gauge are greater than at the Caroona gauge. Conversely when the Mooki River flows are in the lower range (less than approximately 7 ML/day), the flows at Caroona gauge are greater than at the Breeza gauge. The higher flows at Breeza during higher flow periods is due to the inclusion of stream flows that drain a larger catchment area,

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 15

including stream flow contribution from Quirindi Creek. This is discussed further in Section 2.6.6. The difference in stream flow rate at Breeza and Caroona at low river flows is significant, with no flow periods occurring 20% of the time at Breeza, and 10% of the time at Caroona. Low flows (beyond the 60th percentile) indicate higher, more persistent flows at Caroona than at Breeza. These low flow differences are a response of stream flow to extended dry climatic periods and/or natural losses from surface water to the underlying alluvium, and/or groundwater and surface water usage.

Table 8 Stream Flow Gauging Stations

Gauge Number 419034 419027 419098 419106 419093 Quirindi Quirindi Yarraman Mooki River Mooki River Gauge Name Creek at Creek at Creek near at Caroona at Breeza Greenacres Dury Bridge Spring Ridge Catchment Area (km2) 2540 3630 - - - Easting (MGA) 255749.10 258307.32 261004.00 273895.16 243860.54 Northing (MGA) 6522402.73 6537317.15 6522291.31 6516297.86 6523693.54 Distance from site 1.5 13 4 18 13 centre (km) Record Start 23/05/1979 26/09/1971 22/05/2003 12/04/2011 3/03/1999 Record End 05/09/2013 5/09/2013 8/09/2013 8/09/2013 8/09/2013 Average Flow (over period of record) 209.5 325.48 26.8 17.39 - (ML/day) Zero gauge elevation 300.87 282.58 307.32 340.26 308.43 (mAHD) Average river stage (over period of record) 0.856 0.69 0.88 0.77 0.6 (m) Average river stage elevation (over period 301.72 283.27 308.20 341.03 309.03 of record) (mAHD) Note: - means not been recorded; km2 – square kilometres; ML/day – megalitres per day.

2.4 GEOLOGY

The Project area lies in the geological Gunnedah Basin that is a sub-basin of the central part of the more extensive regional geological Sydney-Bowen Basin (Figure 10). This regional Basin extends 1,700 km from central Queensland to offshore southern New South Wales. All three basins are infilled with a sequence of coal-bearing rocks of Permian to Triassic age (Figure 11 and Figure 12).

Tadros (1993) describes the tectonic evolution of the Gunnedah Basin, which is very briefly outlined here. The basin comprises a series of linearly-arranged troughs and adjacent highs, which formed in a volcanic rift system. Hence basal late Carboniferous to early Permian units comprise volcanics (Boggabri Volcanics and Werrie Basalt). A period of basin-wide subsidence and marine transgression occurred in the mid-Permian, depositing a thick sequence of sediments interleaved with pyroclastic deposits (the Porcupine and Watermark Formations). The eastern part of the Gunnedah Basin experienced a final phase of subsidence in the mid-to late

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 16

Permian, with further, primarily fluvial and lacustrine, deposition (Blackjack Group; Figure 12). Similar periods of subsidence and deposition recurred in the Triassic, depositing the Digby and Napperby Formations.

A period of uplift beginning in the late Triassic in the eastern part of the basin activated extensive volcanism, depositing the Jurassic Garrawilla Volcanics, which were then overlain by the fluvial deposits of the Purlawaugh and Pilliga Formations (NSW Department of Mineral Resources [DMR], 2002). In the Tertiary, the last period of active volcanism occurred, depositing basalts of the Liverpool Range Beds. These basalts and the preceding period of uplift in the eastern basin define the current geometry of the Gunnedah Basin.

Quaternary alluvial deposits cover parts of the basin along the alluvial plains of current and palaeo-drainage systems (Figure 11). These deposits have been subdivided into the basal Gunnedah Formation, which is overlain by the Narrabri Formation (Broughton, 1994; Lavitt, 1999). The distinction between these two units has been made based upon clay content versus coarser components like sand and gravel, which is thought to have resulted from changes in the climate and depositional environment around the Pliocene-Pleistocene boundary (Lavitt, 1999). Lavitt (1999) termed the collective alluvial units in the vicinity of the Project area as ‘Mooki Alluvium’, which are lateral equivalents of the ‘Namoi Alluvium’, occurring to the north of Breeza and Gunnedah, along the Namoi River. The term ‘Namoi Alluvium’ has been used throughout this report for simplicity. There are two main alluvial plains, which are broken by Permo-Triassic outcrop on Doona Ridge and Nicholas Ridge (Figure 11). The alluvial plain to the east of the Doona Ridge is called the Mooki alluvial plain, which is associated with the Mooki River and Quirindi Creek. The Mooki alluvial plain covers a large area (150 km2 from north-east to south-east, and is up 100 m thick. The alluvial plain to the south-west of Doona Ridge is termed the ‘Yarraman alluvial plain’, and is associated with Yarraman Creek. It covers an area of around 92 km2 (Australian Groundwater & Environmental Consultants [AGE], 2013).

Of note is the narrow constriction in the alluvium around Breeza (Figure 11), which is the result of a bedrock high (the ‘Breeza Shelf’ [DMR, 2002]), to the south of which lies the ‘Murrurrundi Trough’, within which the deepest sections of alluvium are found in the vicinity of the project area. Lavitt (1999), and other earlier studies, note the Breeza Shelf’s controlling influence on the distribution of Pliocene alluvial facies within the basin, with a south to north change from alluvial fans through to (coarse) bedload stream deposits ‘backing up’ behind the Breeza Shelf. Over the Breeza Shelf, only clayey overbank deposits are found, to the north of which, along the Namoi River, bedload stream deposits are again found.

The Permian coal measures within EL6505 comprise an interbedded sequence of sandstone, conglomerate, siltstone and claystone with coal seams, minor tuff and tuffaceous sediments (AGE, 2013). These sedimentary units unconformably on-lap the Late Permian and strike in a northwest direction with dips of 2 degrees to the south-west. The coal seams of interest belong to the Black Jack Group, which include

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 17

four main coal seams: Clift Seam, Howes Hill Seam, Caroona Seam and Hoskissons Seam (Figure 12).

The Hoskissons Seam is the most important seam in the Caroona area, containing over half the total coal resource, and hence is the subject of the proposed underground mining at Caroona. The coal seam thickness ranges from approximately 8 m to 16 m within the Project area (Mine Subsidence Engineering Consultants, 2014).

2.5 NEARBY MINES AND PROJECTS

The Watermark Project is a neighbouring proposed coal mine in EL7223, immediately north of the Project’s EL6505 (AGE, 2012). The Watermark Project proposes three open cut coal mining areas down to 195 mAHD in its southern mining area, and 225 mAHD in the eastern mining area. The proposed mine has a 30-year operational lifespan. The open cut areas will be progressively backfilled and rehabilitated. The target coal seams are the Hoskissons and Melvilles seams. At the time of writing, the EIS had been lodged and the Project was under assessment by the NSW Government.

Whitehaven Coal Limited (Whitehaven Coal) operates an existing open cut coal mine 4 km south of Werris Creek, east of EL6505 (Werris Creek Coal Mine - Figure 1). This mine extracts coal from the Greta Coal Measures (of early Permian age, older than the basal Werrie Basalt of Figure 11 and Figure 12).

Whitehaven Coal had until late 2012 operated the Sunnyside Coal Mine, located 15 km west of Gunnedah (Figure 1). It excavated coal from the Hoskissons seam using open cut methods down to a proposed elevation of 295 mAHD. The Sunnyside Coal Mine is currently under care and maintenance. Historically (until 2000), the Hoskissons seam was mined to the immediate south of this area, in the Gunnedah Colliery, using underground (bord and pillar methods) (Geoterra, 2008).

Whitehaven Coal also operates the Narrabri Coal Mine, located some 80 km northwest of the Project. This is an underground (longwall) operation which extracts coal from the Hoskissons seam (Aquaterra, 2009). The minimum mine floor elevation is approximately -50 mAHD. Longwall mining at Narrabri commenced in June 2012 (Whitehaven Coal, 2013).

Other regional mining operations and Projects include Whitehaven’s Tarrawonga Coal Mine, Rocglen Coal Mine, Vickery Coal Project and Maules Creek Coal Project and Idemitsu Australia Resources Pty Ltd’s Boggabri Coal Mine.

2.6 GROUNDWATER OCCURRENCE AND FLOW SYSTEMS

There are three groundwater-bearing geological units of varying water quality, yield and therefore of variable utility as water resources in the Caroona area (Table 9):

 Groundwater within the Mooki and Yarraman alluvial plains. The Mooki alluvial plain includes the deeper Gunnedah Formation and the overlying Narrabri Formation. The deeper Gunnedah Formation consists of sands,

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 18

gravels and associated silts and clay. This formation is the most productive and is the source of groundwater from bores used for irrigation throughout the region. The overlying Narrabri Formation has a much lower yield potential and its use is restricted particularly for irrigation purposes because it contains brackish to saline groundwater. The Yarraman alluvial plain further west has much less groundwater potential as the sediments are less productive and contain generally poorer quality groundwater.

 Porous (and fractured) rock groundwater system belonging to the Jurassic to Permian sedimentary and volcanic formations. The coal seams and some sandstone beds within these strata form the main water-bearing strata. These geological units, particularly the coal seams, generally produce much lower yields of poor quality groundwater. The NOW classifies the Jurassic geological units (Pilliga Sandstone, Purlawaugh Formation, Garrawilla Volcanics) as having highly productive groundwater, whilst the older units (Triassic to Permian age) are classified as having less productive groundwater.

 The fractured basalt of the Liverpool Range Beds. This rock type can provide moderate yields of groundwater of generally good quality, but which is largely restricted to an area some considerable distance south of the Project area, in the Liverpool Ranges.

The surficial regolith (weathered rock) water bearing strata yields very small quantities of groundwater in ridge areas, which is of variable quality (AGE, 2013).

Figure 13 shows the interpolated watertable elevation for February 2010. This is a snapshot of the watertable for illustrative purposes (i.e. it will vary due to climatic conditions and localised extraction/use of groundwater). Groundwater flow is generally from south to north with the Liverpool Ranges in the south being a prime recharge area. The watertable contours rely on observed groundwater levels from the Project groundwater monitoring bores and shallow auger holes, from NOW monitoring bores, and from time of drilling water levels stored within NOW’s Pinneena database. The interpolated watertable elevation is useful for determining regional depths and interpreted groundwater flow directions.

Alluvial groundwater flows along the line of the Mooki River from the south-west to the north, and the Yarraman alluvial plain exhibits the same broad flow direction. The low hydraulic gradients within the alluvial plains reflect the higher transmissivity and overall relatively smaller elevation differences of these deposits, compared to the much higher hydraulic gradients seen in bedrock areas that are the result of much lower transmissivity and steep topography.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 19

Table 9 Groundwater Yield and Salinity Summary

YIELD (L/sec) SALINITY (EC; uS/cm) Management Zone Count Min Max Average Median Count Min Max Average Median

Gunnedah–Oxley Basin MDB (Other) Management Zone 241 0.001 38 0.8 0.5 36 2,950 8,948 773 824

(Permo-Triassic strata)

Gunnedah–Oxley Basin MDB (Spring Ridge) Management Zone 177 0.006 83 6.1 0.8 0 n/a n/a n/a n/a

(Jurassic strata)

NSW MDB Fractured Rock Groundwater Sources 94 0.03 21 1.7 0.9 0 n/a n/a n/a n/a

(Liverpool Range Basalts)

Upper and Lower Namoi Groundwater Sources (and Namoi unregulated alluvial) 1292 0.01 200 14 1.5 2,451 1,180 4,873 420 683

(Upper Namoi Alluvium)

Source: NOW Pinneena database. D:\HydroSim\CAR001\GWModel\CARv2TR\Processing\Prediction\MaxDDN\CARv2TR023\CARv2TR023_MaxDDNs_Bores_V2.xlsx

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 20

Interpolated depth to watertable is shown in Figure 14. Consistent with Figure 13, this is a snapshot of the watertable for illustrative purposes. Interpolated watertable depths in the alluvials in the west and south are relatively shallow, ranging from 2 to 10 m. The shallow areas to the west, particularly around Lake Goran, agree with other information (Directory of Important Wetlands) which reports shallow saline watertable issues in these areas. The alluvials around the Mooki River exhibits a contrastingly deep watertable, ranging from 10 to 25 m over broad areas. A shallower watertable is observed over the Breeza Shelf, where the alluvials thin out and become clay-dominated (see Section 2.4). This area acts as a ‘choke’ point on the alluvial groundwater system, as outlined by Lavitt (1999).

On the regolith areas of the Doona and Nicholas Ridges, estimated watertable depths are much greater, ranging from 10 to 100 m. This suggests low recharge rates to outcropping bedrock given that the rock hydraulic conductivity is low to very low.

North-south and west-east potentiometric head cross sections for September 2009 through the targeted exploration area are presented in Figure 15. This figure is a snapshot, however is broadly indicative of the pattern of potentiometric head cross sections across other periods, given no evidence for vertical gradients changing over time. These were generated using vibrating wire piezometer (VWP) data and deep standpipe piezometer data (see Section 2.6.1). They indicate discharge from the Permo-Triassic geological strata to the alluvium from depths as great as 350 m. The sections are dominated by downward hydraulic gradients, with limited areas of upward gradient to the valley floors. This suggests that local land surface topography is the primary control on the flow system, with little to no evidence of down-geologic basin groundwater flow to the west as suggested by regional data (Lavitt, 1999).

2.6.1 Groundwater Monitoring

A significant groundwater monitoring network was installed by BHP Billiton across EL6505 during the period 2007 to 2012. Data loggers have also been installed in 13 existing NOW alluvial aquifer monitoring bores for the Project (see Table 10). A total of 68 monitoring boreholes has been drilled at 32 sites. These consist of 52 standpipe piezometers installed at 26 sites, 18 VWPs with 113 sensors at varying depths, with up to 8 VWPs installed at various depths in the one borehole. 43 bores have been equipped with data loggers set to automated recording of groundwater levels at 6 or 12 hour intervals. Construction details of the standpipe piezometers and VWPs are summarised in Table 11 and Table 12, respectively.

Figure 16 presents the locations of existing groundwater monitoring bores. It shows 47 bores monitoring the alluvial aquifer at 21 sites - 35 holes on Mooki Alluvial Plain located on 15 sites and 12 holes on Yarraman Alluvial Plain located on six sites. It also shows three boreholes drilled in Nicholas Ridge at three locations and the remaining 18 boreholes drilled in Doona Ridge at eight sites.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 21

Table 10 Bore Construction Details – NOW bores

Top of Depth Water Quality Water Level NOW MGA Coordinates Casing Screen Interval Drilled January 2012 Feb 2010 Monitoring Elevation Aquifer/Strata Screened Bores Easting (m) Northing (m) (mAHD) (m) (m below GL) TDS (mg/L) pH (mAHD) Mooki Alluvial Plain GW030010/1 258212 6530642 298.788 29 Alluvium - Gunnedah Formation 22.9 - 29.0 553 7.28 280.85 GW030010/2 258212 6530646 298.786 50.6 Alluvium - Gunnedah Formation 44.5 - 50.6 377.2 7.36 280.26 GW030012/1 257793 6527757 300.827 15.2 Alluvium - Narrabri Formation 9.1 - 15.2 bore is dry GW030012/2 257792 6527762 300.886 44.2 Alluvium - Gunnedah Formation 38.1 - 44.2 757 7.11 282.33 GW030078 257413 6524637 304.147 39.6 Alluvium - Gunnedah Formation 33.5 - 39.6 891 7.1 285.35 GW030380 257418 6524644 304.094 82.3 Alluvium - Gunnedah Formation 73.2 - 76.2 1,032 7.05 284.64 GW030083/1 261259 6520883 314.744 29 Alluvium - Narrabri Formation 26.8 - 28.9 2,593 6.95 291.5 GW030083/2 261251 6520886 315.220 41.1 Alluvium - Gunnedah Formation 35.7 - 41.8 764 7.18 - GW030063/1 265040 6519781 321.490 33.5 Alluvium - Gunnedah Formation 24.4 - 27.4 604 6.88 296.04 GW030063/2 265048 6519778 322.119 53.3 Alluvium - Gunnedah Formation 50.3 - 53.3 604 6.88 295.87 Yarraman Alluvial Plain GW965576/1 NA 7.2 Alluvium - Narrabri Formation 5.2 - 7.2 6,600 7.91 127.09 GW965576/2 247317 6523457 NA 27.8 Alluvium - Gunnedah Formation 25.8 - 27.8 7,839 7.82 298.54 GW965576/3 NA 37.8 Alluvium - Gunnedah Formation 35.8 - 37.8 6,968 7.65 297.56 Notes: (i) Co-ordinates in MGA 56 (ii) Total Dissolved Solids (TDS) was calculated by multiplying electrical conductivity (μS/cm) by a conversion factor of 0.67 (iii) NA – means not available. (iv) GL – means ground level.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 22

Table 11 Bore Construction Details - Piezometer bores

Top of Groundwater Ground Depth Screen Water Quality MGA Coordinates Casing Level July Borehole Level Drilled Interval February 2012 Site No. Elevation Aquifer/Strata Screened 2011 No. Easting Northing (mAHD) (mAHD) (m) (m below GL) TDS (mg/L) pH (mAHD) (m) (m) Mooki Alluvial Plain Alluvium - Gunnedah C011 CCP0061A 260181.4 6519438 312.33 311.43 74 68-74 376 6.81 292.26 Formation Alluvium - Gunnedah C050 CCP0046A 260062.1 6523063 310.78 310.08 37.23 27.75-33.75 620 6.96 290.4 Formation Alluvium - Gunnedah C076 CCP0051A 256549.8 6524064 305.08 303.98 34.5 27.7-33.7 710 7.2 285.96 Formation Alluvium - Gunnedah C089A CCP0063A 258929 6526611 304.54 303.64 63 54-60 421 7.42 284.84 Formation Alluvium - Gunnedah C102A CCP0067A 256711 6527225 301.61 300.25 37 33-36 515 7.07 283.94 Formation C102B CCP0066A 256712 6527224 301.35 300.2 21 Alluvium - Narrabri Formation 17-20 683 6.44 284.04 C102C CCP0065 256711 6527223 301.26 300.26 155 Clift Seam 148-154 724 7.75 284.64 C102D CCP0064A 256712 6527223 3301.2 300.2 96 Alluvium - Base of 89-95 412 6.96 283.97 C199A-1 CCP0163A 258176 6530161 299.83 299.05 27 Alluvium - Narrabri Formation 20-26 2425 12 282 Alluvium - Gunnedah C199A-2 CCP0161A 258175 6530157 300.01 299.14 58.5 51-57 416 7.36 282.03 Formation C199A-3 CCP0160N 258174 6530147 3300.1 299.08 75.63 Clare Sandstone 68-74 336 7.53 282.004 C199A-4 CCP0159N 258174 6530151 300.09 299.07 90 Howes Hill Seam 84-90 287 7.57 281.9 C199A-5 CCP0158 258175 6530154 300.14 299.09 187.3 Hoskissons Seam 106-112 556 7.45 284.93 Alluvium - Gunnedah C265 CCP0151A 260518 6526559 304.67 303.87 30 20-26 864 7.61 291.94 Formation C268-3 CCP0335N 264250 6526549 NA 308.27 21 Alluvium - Narrabri Formation 12-21 No data logger

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 23

Top of Groundwater Ground Depth Screen Water Quality MGA Coordinates Casing Level July Borehole Level Drilled Interval February 2012 Site No. Elevation Aquifer/Strata Screened 2011 No. Easting Northing (mAHD) (mAHD) (m) (m below GL) TDS (mg/L) pH (mAHD) (m) (m) Alluvium - Gunnedah C282A CCP0153A 257325 6526402 302.03 301.17 76.3 67-73 406 7.46 284.67 Formation Alluvium - Gunnedah C285 CCP0155A 256155 6526331 300.87 300.01 93.4 43-49 557 7.94 284.43 Formation Nicholas Ridge C078A CCP0124A 260941 6524822 318.11 317.28 20 Regolith 13.3-19.3 2955 6.92 308.16 25.5-31.5, C162 CCP0148A 262505 6524592 353.84 353.04 45 Regolith 4650 6.31 317.57 37.6-43.5 C153A CCP0123A 261501 6523496 336.79 335.79 24 Regolith 16.4-22.4 2874 6.33 317.48 Doona Ridge C017 CCP0174A 252730 6519793 343.91 342.57 43 Regolith 37-43 2425 6.77 317.8 C037 CCP0142A 253291.1 6522150 338.13 337.13 35 Regolith 26.3-32.3 1367 7.15 321.9 28.5-34.5, C119A CCP0146A 251301 6528797 357.68 356.97 50 Regolith - - 311.22 40.5-46.5 C168B CCP0147A 253664 6525326 349.66 348.81 46 Regolith 28-34, 40-46 - - 304.58 30.5-33.5, C182-1 CCP0138A 252692 6527567 351.15 349.88 40 Regolith No access Bore is dry 36.5-39.5 211-217, 223- C182-2 CCP0131 252691.3 6527564 350.78 349.87 247.4 Clare Sandstone 750 8.61 310.96 229, 235-241 C188-1 CCP0157A 235506 6528396 344.71 343.73 45 Regolith 39-45 - - 301.07 C188-2 CCP0145 235506 6528396 343.58 343.14 241 Hoskissons Seam 225-241 No data logger 169-175, 181- C193A-1 CCP0141A 253865 6529477 318.76 317.53 226 Clare Sandstone - - 286.78 187, 193-199 C193A-2 CCP0139 253859 6529478 319 317.84 18.5 Regolith 12-18 750 8.3 Bore is dry

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 24

Top of Groundwater Ground Depth Screen Water Quality MGA Coordinates Casing Level July Borehole Level Drilled Interval February 2012 Site No. Elevation Aquifer/Strata Screened 2011 No. Easting Northing (mAHD) (mAHD) (m) (m below GL) TDS (mg/L) pH (mAHD) (m) (m) C243 CCP0187 250907 6522948 311.47 310.55 18 Regolith 12-18 15142 6.31 307.95 Yarraman Alluvial Plain Alluvium - Gunnedah C023 CCP0102A 248203 6520811 311.95 310.88 35 29-32 2144 7.82 309.3 Formation C043 CCP0079A 247309.9 6523279 309.17 308.15 106 Alluvium - Base of 94.5-100.5 1802 6.05 308.7 C113 CCP0039 245733 6531232 298.63 297.53 223 Hoskissons Seam 209-215 7772 6.81 288.28 C151 CCP0127A 249208 6524941 306.13 305.2 31.6 Alluvium - Narrabri Formation 25-28 15209 5.98 303.24 Alluvium - Gunnedah C180A CCP0110A 249967.8 6527530 304.24 303.26 47 39.8-45.8 14740 6.27 301.61 Formation C137-1 CCP0362 254010.73 6530956.05 295.87 186.58 Alluvium – Hoskissons Seam 163- 172 No data logged C137-2 CCP0363N 254010.43 6530954.12 295.84 42.2 Alluvium – Hoskissons Seam 36 – 42 No data logged C137-3 CCP0364A 254010.33 6530952.19 295.86 21.46 Alluvium – Hoskissons Seam 12 -21 No data logged Note: (i) Co-ordinates in MGA 56 (ii) TDS was calculated by multiplying electrical conductivity (μS/cm) by a conversion factor of 0.67(iiii ) “-” means Insufficient water to sample on February2012.

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Table 12 Bore Construction Details - Vibrating Wire Piezometers

Depth Depth of Vibrating Groundwater Borehole MGA Coordinates RL Collar Target Aquifer/Strata of VWP Site No. Drilled Wire Completions Level July 2011 No. (in descending depth order) Easting (m) Northing (m) (mAHD) (m) (m below GL) (mAHD) Mooki Alluvial Plain 105 Below Base of Alluvials 293.88 195 Sandstone/Conglomerate 297.88 C011 CCP0060 260182.29 6519440.34 311.61 592.24 424 Clift Seam 289.97 530 Hoskissons Seam 287.31 90 Base of weathering 283.06 155 Mooki/Springfield Seams Interburden 290.73 217.94 Clift Seam B 292.10 256 Goran Conglomerate C 445.93 C050 CCP0017 260062.13 6523062.94 310.11 433.28 283.98 Lower Breeza Seam 286.43 340 Howes Hill/Caroona A Seams Interburden 288.51 372.5 Hoskisson Sesam 284.30 425.57 Lower Melville Seam 509.82 80 Below Base of Alluvials 284.10 103.5 Yarraman/Doona Interburden2 282.76 C076 CCP0050 256549.8 6524063.8 304.03 330.78 207 Springfield/Clift Seams Interburden 287.29 Caroona Seam/Hoskissons Seams 299 288.62 Interburden 73.75 Springfield Seam B 282.11 C089A CCP0062 258929.4 6526611 303.64 301.12 110 Clift Seam 281.10 150 Goran Conglomerate C 285.14

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 26

Depth Depth of Vibrating Groundwater Borehole MGA Coordinates RL Collar Target Aquifer/Strata of VWP Site No. Drilled Wire Completions Level July 2011 No. (in descending depth order) Easting (m) Northing (m) (mAHD) (m) (m below GL) (mAHD) 217.75 Howes Hill Seam 282.60 Caroona Seam/Hoskissons Seams 236.5 281.84 Interburden 247 Hoskissons Seam 284.00 270 Hoskissons/Melville Seams Interburden 282.34 288.5 Melville Seam 282.18 56 Base of Alluvium+30m 287.62 C265 CCP0135 260521.5 6526558.37 303.85 247.27 105 Clift Seam 287.53 130 Base of Alluvium+30m 278.22 C282A CCP0152N 257321.13 6526401.31 301.17 169.06 160 Base of Alluvium+60m 281.02 Springfield Seam/Waverly Conglomerate 124 279.09 Interburden C285 CCP154N 256155.52 6526327.03 300.07 279.68 150 Waverly Conglomerate 280.44 265 Hoskissons Seam 279.82 Doona Ridge 335 Doona Seam 367.08 436 Clift Seam 212.20 C017 CCP0156 252734.25 6519792.31 342.57 590.2 487 Clare Sandstone B 290.64 537 Hoskissons Seam 277.03 100 Conglomerate 316.62 C037 CCP0144 253291.07 6522150 337.13 428.4 226 Doona Seam 291.15 285 Intrusive 285.48

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 27

Depth Depth of Vibrating Groundwater Borehole MGA Coordinates RL Collar Target Aquifer/Strata of VWP Site No. Drilled Wire Completions Level July 2011 No. (in descending depth order) Easting (m) Northing (m) (mAHD) (m) (m below GL) (mAHD) 338 Clift Seam 283.42 370 Clare Sandstone B 290.72 413 Hoskissons Seam 325.53 181.5 Doona Seam 287.71 275 Clift Seam 285.54 C168A CCP0095 253663.99 6525325.63 348.81 385.22 311 Clare Sandstone B 284.03 363 Hoskissons Seam 284.29 73 Doona Seam Roof 284.43 87 Doona Seam 283.00 120 Clift Seam Roof2 288.70 132.5 Clift Seam Roof1 284.96 C188-3 CCP0128 253514.23 6528391.63 342.84 255.02 145 Clift Seam 283.42 215 Clare Sandstone C 286.08 225 Hoskissons Roof 283.15 236 Hoskissons Seam 281.56 75 Doona Seam Roof 287.19 91 Doona Seam 282.10 120.5 Clift Seam Roof2 282.40 C188-4 CCP0140 253523.88 6528416.2 343.58 255.76 129.5 Clift Seam Roof1 280.53 145 Clift Seam 281.18 215 Clare Sandstone C 283.08 224 Hoskissons Roof 285.08

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Depth Depth of Vibrating Groundwater Borehole MGA Coordinates RL Collar Target Aquifer/Strata of VWP Site No. Drilled Wire Completions Level July 2011 No. (in descending depth order) Easting (m) Northing (m) (mAHD) (m) (m below GL) (mAHD) 235 Hoskissons Seam 281.45 77 Doona Seam Roof 283.26 90.5 Doona Seam 286.81 122 Clift Seam Roof2 283.54 135.5 Clift Seam Roof1 282.79 C188-5 CCP0132 253479.91 6528386.68 345.24 255.75 149 Clift Seam 284.74 217 Clare Sandstone C 282.75 228 Hoskissons Roof 282.26 239 Hoskissons Seam 281.64 72 Doona Seam Roof 293.46 86 Doona Seam 289.05 117 Clift Seam Roof2 286.02 133 Clift Seam Roof1 286.34 C188-6 CCP0136 253541.93 6528366.69 340.92 249.65 145 Clift Seam 286.98 212 Clare Sandstone C 292.81 222 Hoskissons Roof 283.80 233 Hoskissons Seam 284.71 Yarraman Alluvial Plain 150 Intrusion 302.09 302.25 Doona Seam 291.62 C023 CCP089 248202.22 6520806.61 310.85 523 433 Clift Seam 284.88 502.5 Combined Caroona & Hoskissons Seam 276.82

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 29

Depth Depth of Vibrating Groundwater Borehole MGA Coordinates RL Collar Target Aquifer/Strata of VWP Site No. Drilled Wire Completions Level July 2011 No. (in descending depth order) Easting (m) Northing (m) (mAHD) (m) (m below GL) (mAHD) 110 Below Base Alluvials 306.84 193 BHAL/Doona Seam Interburden 305.39 271 Doona Seam 293.93 358 Clift Seam 283.32 C043 CCP0073 247309.9 6523279 307.92 487.02 396 Clare Sandstone C 286.74 424.4 Hoskissons Seam 285.01 444 Hoskissons/Melville Seams Interburden 262.02 461 Melville Seam 257.22 160 Doona Seam 289.60 289 Clift Seam 282.92 C151 CCP0116 249207.6 6524941.76 305.2 355.3 327 Clare Sandstone C 280.63 350 Hoskissons Seam 281.19 68.8 Yarraman Seam 298.90 114 Mooki Seam 294.89 127 Springfield Seam 289.68 C180A CCP0100 249967.7825 6527529.878 303.29 283.12 176 Clift Seam 287.31 199 Clare Sandstone B 284.71 232 Hoskissons Seam 282.90 261.5 Melville Seam 284.09 Note: (i) Co-ordinates in MGA 56.

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2.6.2 Groundwater Recharge

Recharge to the alluvial groundwater system is derived from a range of sources: diffuse rainfall recharge and irrigation recharge primarily on the Mooki alluvial plain. There is also runoff-recharge at the alluvial margins, horizontal and vertical discharge from adjacent (ridgeline) and underlying bedrock, and leakage from streams – during normal flow conditions and during overbank flood events (Merrick, 2001). Recharge to the bedrock units is likely to be significantly lower than to the alluvium, given the bedrock’s comparatively much lower hydraulic conductivity (see Section 2.6.6) and hence its limited capacity to receive and transmit sub-surface water.

Ringrose-Voase et al. (2003) applied the crop-soil-water model APSIM to assess deep drainage throughout the Liverpool Plains under a variety of different cropping regimes and soil types. They estimated long-term average deep drainage rates under current land use in the range of:

 45 mm/year on the alluvial plains;

 39 to 78 mm/year on the basalts; and

 23 to 91 mm/year on the Permo-Triassic rock units.

It must be noted that these estimates do not account for interflow, or soil moisture storage below the modelled soil profile (4 m in the case of Ringrose-Voase et al., 2003), and as such actual recharge to the groundwater system is likely to be lower. This is particularly so in the steeper (Permo-Triassic and basaltic) slopes, where a significant proportion of the modelled deep drainage is likely to be shed laterally as interflow (see Rassam and Littleboy, 2003).

Similar modelling conducted under the Australian Water Availability Project (AWAP) estimated a long-term (1958-2012) average annual recharge rate to the alluvials in the Mooki River catchment of around 20 mm/year. This modelling was used to parameterise NOW’s Upper Namoi groundwater flow model, and included the effects of rainfall, irrigation and flood recharge (C. McNeilage, pers. comm. 2013).

Other investigators estimate very low rates of rainfall recharge on the plains (e.g. Lavitt, 1999; Cox and Raiber, 2011), as indicated by the higher salinity of the Narrabri Formation, compared to the relatively low salinity of the underlying Gunnedah Formation. The comparatively low salinity of the Gunnedah Formation suggests that recharge primarily occurs up-catchment, probably around the margins of the alluvial plain. Young et al. (1996) estimated recharge rates to the alluvium in the Mooki catchment of 20-30 mm/year, but noted that there were a number of samples analysed with no tritium, which suggests old groundwater and very low rates of recharge.

AGE (2012) reported that investigations conducted by the University of New South Wales at their research station at Breeza suggest very low recharge rates, in the order of 0.2% of rainfall (around 1 mm/year) on the black soils of the plains. Higher estimates have been made however, using the chloride mass balance and hydrograph fluctuation methods, in the order of 58 mm/year (Berhane, 2001).

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 31

SWS (2012) (i.e. the Namoi Catchment Water Study) collated a range of recharge models’ and groundwater flow models’ recharge estimations and parameterisations for the area. These generally range from 0.5 to 5% of average annual rainfall.

Section 3.3.2 provides a description of recharge rates applied to the model for the Project.

2.6.3 Groundwater Use

The Gunnedah Formation within the Mooki alluvium is the primary (highest yielding, most utilised) aquifer system in the region. Groundwater from the Gunnedah Formation in this region is used extensively for irrigation, stock and domestic use and for the town water supply at Gunnedah, Breeza, Curlewis, Quirindi and also Caroona (Groundwater Exploration Services, 2014; AGE, 2012). But the same formation in the Yarraman alluvial plain is less productive with much poorer quality groundwater available that limits its usage.

A search of the NOW groundwater bore database identified 5279 registered bores and wells within an area 70 km by 97 km centred EL6505. Based on the NOW Pineena database, 72 bores are owned by mines; 201 bores belong to NOW; 4188 bores are privately owned; 106 bores are owned by local or other government; 11 are owned by schools; 2 are owned by trusts; and 699 have unknown owners. The identified bores are shown in Figure 16, whilst the estimated development of groundwater use over time is presented in Figure 17; these data were extracted from NOW’s upper Namoi groundwater flow model (C. McNeilage, pers. comm. 2013). They show a significant increase in Namoi Alluvium groundwater usage from the early 1970s through to 2002-2003, beyond which time rates of usage decrease significantly, in line with stricter regulation of abstraction.

2.6.4 Groundwater Qualitty

A summary of groundwater chemistry based on sampling from bores in each of the main hydrogeological units is shown in Table 13. The data are derived from 42 monitoring bores – data from 23 bores in the period from June 2008 to August 2012, and data from 15 bores in the period from October 2010 to August 2012. Therefore the data are considered representative of medium term conditions. Total Dissolved Solids (TDS) estimates are summarised in Figure 18; TDS was calculated by multiplying electrical conductivity (μS/cm) by a conversion factor of 0.67.

2.6.4.1 Salinity

Table 10 and Table 11 present field sampling salinity data from the Mooki alluvial plain in January-February 2012. The groundwater samples were collected from the alluvium. Narrabri Formation bores exhibit a low to moderate salinity, ranging from 553 to 2,593 mg/L, and as such most groundwater within the formation in this area can be classified as fresh to brackish. These salinities are fresher than those observed in the Narrabri Formation of the Yarraman alluvial plain, which has distinctly higher salinities, with a range of 6,600 to 15,209 mg/L. The same situation is observed in the Gunnedah Formation: lower salinities ranging from 376 to 1,032 mg/L in the Mooki

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 32

alluvial plain, and higher salinities ranging from 2,144 to 14,740 mg/L in the Yarraman alluvial plain.

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Table 13 Summary of Groundwater Chemistry - Groundwater Monitoring Piezometers

Water Quality Number of Monitoring Number of Laboratory Aquifer Screened TDS (mg/L) pH Bores Samples Collected Range Average Median Range Average Median

Alluvium - Narrabri Formation 296-22579 4623 1755 6.0-12.9 7.6 7.3 9 124

Alluvium - Gunnedah 19 260 369-19966 1636 727 5.7-8.7 7.4 7.4 Formation

Regolith 625-17755 4235 2821 6.3-8.6 7.1 6.9 8 74

Clift Seam 710-6559 1708 804 7.9-9.7 8.8 8.9 1 11

Clare Sandstone 336-1149 682 750 7.5-8.7 8.0 8.0 2 21

Howes Hill Seam 287-374 326 332 7.3-8.0 7.7 7.8 1 10

Hoskissons Seam 551-11189 4954 7203 6.7-8.1 7.3 7.2 2 24

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 34

Table 13 shows that the Narrabri Formation exhibits a generally higher salinity (TDS; median of 1,755 mg/L) than the underlying Gunnedah Formation (median of 727 mg/L). Variability is however similar between the two formations: Narrabri Formation salinity varies from 296 to 22,579 mg/L, whilst that of the deeper Gunnedah Formation is 369 to 19,966 mg/L.

Table 11 presents field sampled groundwater salinity data from regolith monitoring bores on Doona Ridge and Nicholas Ridge. These bores screen between 13.3 m and 45 m depth into the weathered material. The data from the three monitoring bores on Nicholas Ridge indicate that groundwater in the regolith is moderately saline from 2,343 mg/L to 4,183 mg/L. Beneath Doona Ridge, data from four monitoring bores in the regolith indicates a brackish to saline water quality varying from 1,266 mg/L to 15,232 mg/L. The wider salinity range on Doona Ridge could simply reflect the much larger area of Doona Ridge compared to Nicholas Ridge, which would provide greater opportunity for a wider range of groundwater flow path lengths from hillcrest to plain, and hence a wider range of groundwater salinities.

One site which monitors the Clift Seam beneath the Mooki alluvial plain has been sampled (Table 13). Groundwater salinity in this bore is brackish, with an average of 1,708 mg/L TDS.

From the east (shallow subcrop recharge area) to the deep down-dip (discharge) area, groundwater in the Clare Sandstone changes from fresh to slightly brackish (Figure 18), with an average TDS of 378 mg/L on the Mooki alluvial plain and 958 mg/L beneath Doona Ridge.

Groundwater from the Howes Hill Seam has been sampled at one site. This site is located on the Mooki alluvial plain, and the data indicate that groundwater is fresh, with an average salinity of 326 mg/L (Table 13).

Samples were collected from two sites monitoring the Hoskissons Seam, one on the Mooki Alluvial Plain and another on the Yarraman Alluvial Plain. Groundwater is fresh on the Mooki alluvial plain (average 622 mg/L TDS), and saline on the Yarraman alluvial plain (average TDS of 8,358 mg/L). This is the same pattern as observed in the Clare Sandstone: an increase in groundwater salinity in a down-geologic basin direction (from east to west, from shallow subcrop to deep burial).

2.6.4.2 pH

Measured groundwater pH data indicate slightly acidic to highly alkaline conditions, with pH ranging between 5.7 and 12.9 (Table 13). Water from the alluvium has the widest pH range, between 5.96 and 12.9 in the Narrabri Formation and between 5.7 and 8.7 in Gunnedah Formation. Groundwater in the regolith and Hoskissons seam is typically slightly acidic to alkaline. Howes Hill seam pH is generally neutral, varying from 7.3 to 7.97. Groundwater in the Clift seam and Clare Sandstone is mildly alkaline, with average pH values of 8.8 and 8.0 respectively.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 35

2.6.5 Hydraulic Properties

Five hydraulic conductivity test methods have been applied to selected exploration holes for the Project to investigate the rock/alluvial system pore space conductivity and the rock fracture network conductivity (Table 14; AGE, 2013 and SCT, 2012). Figure 19 shows the testing sites and the type of testing undertaken at each site. Details of the hydraulic conductivity test methods follow:

 Packer (Lugeon) Tests: Single-hole in-situ test of formation hydraulic conductivity performed by measuring the volume of water taken in a section of test hole when the interval is pressurised. A total of 377 tests were undertaken at nine sites located on both the alluvium and ridge areas. All packer testing programs have been undertaken by SCT to investigate the conductivity of the pores and fractures.

 Slug/falling head tests: Inserting or removing a slug of water and measuring the rate of recovery back to static level. 16 sites provided 46 tests, all bar two tested the alluvium. These works were completed by AGE.

 Pumping Tests: AGE conducted 24 and 48-hour constant rate pumping tests. A total of four tests were completed at four sites, within the Gunnedah formation, Clare Sandstone and Caroona/Hoskissons seam. The work investigated both pore space and fractured rock mass hydraulic conductivity, and attempted to characterise the degree of hydraulic connection between the alluvium and underlying rock units.

 Core sample hydraulic conductivity tests: SCT analysed 23 core samples in a laboratory to assess pore space hydraulic conductivity of the rock mass.

 Multi-hole interference tests and multi-phase tests: 38 tests were completed by SCT and Multiple Technologies to investigate the borehole horizontal conductivity and reservoir properties in the coal seams and in the Clare Sandstone.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 36

Table 14 Summary of Hydraulic Property Testing

Multi-hole / Multi- Pump Core Packer Phase (SCT and Slug/Falling Strata Out Samples Total (SCT) Multiple Head (AGE) (AGE) (SCT) Technologies) Alluvium - - 19 2 - 21

Interburden -Below 36 - - - - 36 Base of Alluvium

Interburden -Below 14 - - - - 14 Base of Weathering

Digby Conglomerate 6 - - - 1 7

Goran 17 - - - - 17 Conglomerate

Conglomerate 14 - - - - 14

Springfield Seam 9 - - - - 9

Doona Seam 7 3 - - - 10

Nicholas Seam 4 - - - - 4

Mooki Seam 5 - - - - 5

Clift Seam 21 9 - - - 30

Breeza Seam 14 2 - - - 16

Clare Sandstone 57 8 1 1 21 88

Howes Hill Seam 3 3 - - - 6

Caroona/Hoskissons 35 9 1 1 - 46 Seam

Melvilles Seam 10 4 - - - 14

Interburden 125 - - - - 125

Unknown - - - - 1 1 TOTALS 377 38 21 4 23 463 Source: AGE (2013)

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 37

2.6.5.1 Hydraulic Conductivity (K)

Figure 20 presents the hydraulic conductivity of the Hoskissons and Clift Seams at Caroona and testing at other mining and coal seam gas projects in the Gunnedah Basin. The results of the packer testing, interference testing and multiphase testing are sourced from SCT (2012). The interference- and multi-phase test data for the Project estimates high hydraulic conductivities relative to other regional test work, specifically the Project packer testing results, and the regional Watermark and coal seam gas testing data.

Figure 20 shows packer test Clift and multiphase Clift testing data mostly fit in the coal hydraulic conductivity range determined by AGC (1984) and Mackie (2009), however, Hoskissons Seam interference testing data are outside of Mackie’s range. Hence, the high conductivities seen in the Project data are likely a reflection of the test method, which appears to be biased towards higher hydraulic conductivity. All hydraulic conductivity testing values decrease with depth below ground surface due to the increase in overburden pressure (Figure 20).

Testing work at Maules Creek in the Gunnedah Basin estimated a coal seam hydraulic conductivity range between 1E-2 and 1E-1 m/day (AGE, 2011). The Namoi Water Study indicates a hydraulic conductivity range for the Black Jack Group of between 2E-3 and 3E-2 m/day (SWS, 2010). The Watermark Project to the north of Caroona reported coal seam hydraulic conductivity values from 9.6E-5 to 1.1E- 1 m/day, similar to the Caroona Project, based on packer tests and slug tests (AGE, 2012).

It must be noted that the data collected for this Project are all skewed towards measurements of horizontal hydraulic conductivity, with only three interburden core sample tests (at site CCP009), and inverse modelling of head propagation through the interburden providing data on vertical conductivity (discussed below). Accordingly, vertical hydraulic conductivity has been estimated from horizontal measurements using recognised relationships between the two.

As there are no available measurements of coal seam vertical hydraulic conductivity. AGE (2013) estimated that the vertical conductivity is potentially the same as horizontal.

The Clare Sandstone exhibited significant groundwater yields during drilling of two large diameter bulk sampling holes on Doona Ridge. This unit would be fractured and depressurised by the proposed longwall mining if the height of fracturing (cracking) intercepts this geological unit (AGE, 2013), which was the reason for the hydraulic conductivity testing of this unit. Four different hydraulic conductivity test methods were applied in the Clare Sandstone, the results of which are shown in Figure 21. The lowest hydraulic conductivity values are derived from core sample primary conductivity testing, which indicates a range from 9E-5 m/day to 9E-4 m/day. Results from packer tests are higher, in the range of 9E-4 to 9E-1 m/day for depths less than 200 m. Packer test-derived hydraulic conductivity significantly reduces below 200 m depth, in the range of very low or practically zero flow to 9E-4 m/day. SCT (2012) also report that Clare Sandstone hydraulic conductivity is higher in the north-east, in

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 38

shallow subcrop, and progressively lower in the south westerly direction as its depth increases.

The multiphase tests and the falling head tests on the Clare Sandstone report the highest hydraulic conductivity values in the range of 5E-3 to 8E-2 m/day. There has been one pumping test conducted in the Clare Sandstone, at site C182 beneath Doona Ridge. This comprised pumping at a constant rate of 2.7 L/second for 24 hours. This test resulted in the highest hydraulic conductivity value estimate of all testing, at 1.7E-1 m/day. SCT (2012) provide the average horizontal conductivity for the Clare Sandstone in the range of 1E-2 m/day for depths less than 200 m, decreasing to 1E-4 m/day at depths greater than 300 m; SCT’s report states that these values are biased to the higher end of the hydraulic conductivity range however, as core samples were preferentially selected from higher hydraulic conductivity horizons. They estimate that the vertical conductivity could be half that of the horizontal hydraulic conductivity. Testing for the Watermark Project (AGE, 2012) estimated vertical hydraulic conductivity between 1.2 and 2 times lower than horizontal.

Packer testing was the primary method used for the Project to measure the hydraulic conductivity of the interburden, the results of which are shown in Figure 22. Core samples were also analysed for hydraulic conductivity, and this mostly focussed on the Clare Sandstone (Figure 21), but also included four samples from higher porosity interburden units at site CCP009 (Figure 22). Packer testing between base of alluvium and first underlying coal seam, and below first coal seam, indicate the same range of interburden hydraulic conductivity (about 1E-2 to 1E-5 m/day), with only a very weak declining trend with depth. Figure 22 shows that the Clare Sandstone is more permeable than interburden until it reaches depths below 400 m.

To estimate the vertical hydraulic conductivity of the interburden, SCT (2012) applied inverse modelling of head change propagation and attenuation from the alluvials down into the underlying rock strata, as observed in nested VWPs at a range of locations. This approach estimated a vertical conductivity range of 9E-5 to 9E- 4 m/day for depths less than 200 m, and 9E-6 m/day or less for depths greater than 200 m.

Hydrographs at nested bores, located at site 102, were reviewed by AGE (2013). This site contains bores in the Gunnedah and Narrabri formation alluvium, base of alluvium and in the Clift seam. The hydrographs show a consistent response to nearby irrigation pumping in the alluvium, however the Clift seam shows a limited pressure response, indicating that there is a degree of hydraulic separation between the coal seam and the alluvium (AGE, 2013).

The neighbouring Watermark Project collected a significant body of horizontal and vertical core hydraulic conductivity data for the interburden units (AGE, 2012). These data are considered to be relevant to Caroona as the geological units are similar and are summarised and reproduced in Table 15 and Table 16. Freeze and Cherry (1979) recommend that horizontal hydraulic conductivity data are most appropriately summarised using the arithmetic mean, whilst vertical hydraulic conductivity data are best summarised using the harmonic mean. This is because bulk vertical

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 39

conductivity is dominated by the least permeable medium, whilst horizontal conductivity is dominated by the most permeable medium (Freeze and Cherry, 1979). The corresponding means from the Watermark Project are 4.88E-2 m/day (horizontal), and 5.76E-6 m/day (vertical). Freeze and Cherry (1979) also recommend summarising the ratio of vertical to horizontal hydraulic conductivity data using these same means; in this case, the bulk ratio based upon the Watermark data is 1.18E-4.Falling head tests conducted on the Narrabri Formation yield hydraulic conductivities in the range of 2E-2 m/day to 1 m/day. Two constant rate pumping tests at sites C102 and C199 were undertaken to estimate the hydraulic conductivity of the Gunnedah Formation which yielded values above 100 m/day.

Table 15 Core Hydraulic Conductivity Data Summary from the Watermark Project

Hydraulic Conductivity (m/day) Statistic Kz:Kh Ratio Horizontal (Kh) Vertical (Kz) Harmonic mean 1.23E-05 5.76E-06^ 0.32 Geometric mean 6.64E-04 2.71E-04 0.53 Arithmetic mean 4.88E-02^ 2.02E-02 0.64 Median 9.85E-04 4.41E-04 0.66 ^ Ratio Kz / Kh = 1.18E-4

Table 16 Core Hydraulic Conductivity Data from the Watermark Project

Depth Depth Length Bore Unit Kh (m/day) Kz (m/day) Kz:Kh from (m) to (m) (m) WM0291 Alluvium 67.4 67.6 0.2 6.05 x 10 -3 3.12 x 10 -3 0.52 Alluvium 72.9 73.1 0.2 2.15 x 10 -2 no data Sandstone 96.14 96.34 0.2 1.30 x 10 -4 1.12 x 10 -4 0.87 Sandstone 99.2 99.4 0.2 3.80 x 10 -3 2.51 x 10 -3 0.66 Conglomerate 101.33 101.44 0.11 2.07 x 10 -2 2.03 x 10 -2 0.98 Sandstone 102.8 103 0.2 5.44 x 10 -5 2.59 x 10 -5 0.48 Carb Mudstone 105.15 105.3 0.15 8.29 x 10 -3 5.10 x 10 -3 0.61 Conglomerate 131.7 131.9 0.2 2.56 x 10 -4 3.20 x 10 -4 1.25 Mudstone/Siltstone 141.18 141.32 0.14 1.72 x 10 -3 8.00 x 10 -7 4.7 x 10 -4 Sandstone 143.06 143.26 0.2 7.60 x 10 -4 9.68 x 10 -4 1.27 WM0012 Interburden 52 52.2 0.2 no data <8.64 x 10 -7 WM0042 Siltstone 32.8 32.92 0.12 8.64 x 10 -7 8.64 x 10 -7 1 Conglomerate 216.2 216.33 0.13 9.85 x 10 -4 7.43 x 10 -4 0.75 Sandstone 292.24 292.5 0.26 2.76 x 10 -5 no data Maules Creek 318.46 318.66 0.2 8.99 x 10 -3 6.74 x 10 -3 0.75 WM0255 Siltstone 69 69.15 0.15 2.49 x 10 -3 2.14 x 10 -3 0.86 Sandstone 153.03 153.2 0.17 1.04 x 10 -4 8.64 x 10 -5 0.83 WM0074 Sandstone 42.3 42.4 0.1 1.30 x 10 -4 2.51 x 10 -5 0.19 R Sandstone 103.63 103.83 0.2 8.41 x 10 -1 9.85 x 10 -2 0.12 Hoskissons U roof 105.4 105.55 0.15 3.34 x 10 -3 9.07 x 10 -4 0.27

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 40

Depth Depth Length Bore Unit Kh (m/day) Kz (m/day) Kz:Kh from (m) to (m) (m) Sandstone 140 140.3 0.3 2.07 x 10 -5 1.38 x 10 -5 0.67 Dolerite 164.4 164.55 0.15 1.73 x 10 -6 8.64 x 10 -7 0.5 WM0066 Conglomerate 45.67 45.87 0.2 5.49 x 10 -1 4.33 x 10 -1 0.79 Siltstone 116.71 116.91 0.2 1.56 x 10 -4 4.58 x 10 -5 0.29 Carb Mudstone 151.49 151.69 0.2 1.02 x 10 -3 4.41 x 10 -4 0.43 Sandstone 158.81 159.01 0.2 5.18 x 10 -5 3.11 x 10 -5 0.6 Sandstone 185.9 186.05 0.15 8.21 x 10 -3 4.75 x 10 -3 0.58 Sandstone 225.64 225.8 0.16 3.97 x 10 -5 3.28 x 10 -5 0.83 Mudstone 240.76 240.96 0.2 1.73 x 10 -6 8.64 x 10 -7 0.5 Hosk-Mel Interburden 243.24 243.36 0.12 2.71 x 10 -2 7.52 x 10 -4 0.03 WM0239 Sandstone 14 14.2 0.2 4.67 x 10 -5 2.25 x 10 -5 0.48 WM0258 Hosk-Mel Interburden 40.84 40.99 0.15 6.74 x 10 -3 4.84 x 10 -3 0.72

Falling head tests on the Narrabri Formation estimate hydraulic conductivities in the range of 2 x 10-2 m/day to 1 m/day. Two constant rate pumping tests at sites C102 and C199 were undertaken to estimate the conductivity of the Gunnedah Formation which provide estimates above 100 m/day.

AGE (2013) reported on test pumping on bore C102, in the Narrabri and Gunnedah Formations. They reported that: “Alluvial bores C102-B (18 m to 20 m) and C102-A (33 m to 36 m) screened in the Narrabri and Gunnedah Formations respectively and bore C102-D at the base of the alluvium in highly weathered conglomerate, respond in unison showing pressures transmit through the interburden strata. In contrast, the hydrograph of bore C102-C (148 m to 154 m) which is screened in the Clift Seam is relatively flat-lying and only records a pressure response of about 1 m, indicating that there is a degree of hydraulic separation between the coal seam and the alluvium.”

2.6.5.2 Specific Yield

Specific yield (Sy) (together with porosity and specific storage) usually decreases with depth due to increasing overburden pressure. The Watermark model (AGE, 2012) calibrated alluvial Sy in the range of 0.032 to 0.2. Interburden Sy used in that model was in the range of 0.001 to 0.015. Clare Sandstone Sy was estimated to be 0.0012 and Hoskissons Coal Seam 0.0022 in the same model. These are considered to be useful for the Project given the proximity of the projects and similar geology.

2.6.5.3 Specific Storage

Direct testing data are not available for specific storage (Ss) of coal seams or interburden. The Watermark model calibration parameterisations (AGE,2012) suggest that Ss is in the order of 1.7E-5 m-1 for the Hoskissons Coal Seam, 1E-5 m-1 to 5E-5 m-1 for interburden, and 5E-5 m-1 for the Clare Sandstone.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 41

2.6.6 Groundwater-Surface Water Interaction

The increase in stream flows in the downstream direction between Caroona and Breeza during higher flow periods noted in Section 2.3 with reference to Figure 9 can be largely attributed to gains from runoff, rather than gains from the groundwater system as baseflow. There is no evidence of baseflow gains along this reach in Figure 9, given that the low flows at Caroona are greater than they are at Breeza. In addition there are more frequent no flow periods at Breeza than there are at Caroona.

The average flow at the Quirindi Creek at Greenacres gauge (419098) over its period of record (2003-2013), which gauges inflows from Quirindi Creek into the Mooki River between Caroona and Breeza, is 26.8 ML/day. The corresponding average flow on the Mooki River at the Caroona gauge is 155 ML/day, and that at Breeza is 175 ML/day; the inflow from Quirindi Creek to the Mooki River explains more than the average increase in flow along the Mooki River between Caroona and Breeza (20 ML/day), and suggests some loss (at least 6.8 ML/day) of flow along this reach, to the underlying alluvial groundwater system, and / or to surface water usage.

The flow gain/loss analysis along the Mooki River between Caroona and Breeza is further explored in Figure 23, which shows estimated flow gains and losses as calculated using the difference in 7-day moving average flows between Caroona and Breeza, with the inflows along the reach comprising the gauged flows on the Mooki River at Breeza, plus those on Quirindi Creek at Greenacres. The moving average is used to account for channel storage and attenuation, and the resultant lags in gauged flows between upstream and downstream gauges.

Figure 23 confirms that this stream reach does, on average and most of the time, lose water to the underlying groundwater system and /or surface water usage. The reach does however switch between flow gaining and flow losing conditions, with gains observed far more consistently during higher flow periods, with a similar but much weaker trend in the timing of flow losses. This tends to confirm that the observed flow gains are primarily runoff, rather than groundwater- (baseflow-) derived.

NOW maintains a nested (i.e. several bores at the one location, screened at different levels) cluster of groundwater monitoring bores adjacent to the lower Quirindi Creek channel (GW030078 / GW030380;Figure 16). Groundwater level data from these bores has been compared to the estimated stream bed elevation and estimated creek water levels in Figure 24, via extrapolation of the Greenacres gauge data downstream (~4.5 km) based on the topographic gradient along the creek as derived from BHP Billiton’s high resolution elevation (LIDAR) data. The inference that this area of the Mooki River and Quirindi Creek primarily loses flow is supported by Figure 24, which shows that the groundwater potentiometric surface/watertable lies 10 to 12 m below the creek stage and surface water therefore migrates down into the underlying Namoi Alluvium. The data indicate that there is probably a 10 m thick unsaturated zone between the lower Quirindi Creek and the underlying watertable.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 42

The regional depth to watertable mapping of Figure 14 also confirms that the Mooki River between Caroona and Breeza is a losing stream with estimated groundwater levels at about 10 m below the bed of the river. Many groundwater level hydrographs in the Upper Namoi Alluvium (Attachment D) indicate that levels have dropped by 10-15 m since 1980, which is likely in response to the significantly increasing groundwater usage over that time (Figure 17), rather than climate given that there has been a broadly increasing rainfall trend post-1968 (Figure 7). This effect could have potentially altered the system’s state with regard to pre- groundwater development baseflow gains and losses along the Mooki River.

2.7 CONCEPTUAL HYDROGEOLOGICAL MODEL

Figure 25 presents a schematic of the Project’s conceptual hydrogeological model, in the pre-mining state. Figure 26 presents the conceptual model of mining impacts on the system.

2.7.1 Hydrostratigraphic Units

The three major hydrostratigraphic units (HSUs)1 in the vicinity of the Project area are outlined in Section 2.6.

2.7.2 Recharge

Recharge to the alluvial groundwater system is derived from a range of sources including diffuse rainfall recharge runoff-recharge at the alluvial margin, upward discharge from underlying bedrock, horizontal discharge from the bedrock on ridge areas, and leakage from streams into the alluvium. Irrigation recharge occurs only where irrigation occurs on the Mooki and Quirindi alluvial flats. Recharge from stream seepage occurs during normal surface flow conditions, and during overbank flood events. Recharge to the bedrock units and in turn from the alluvial sediments is significantly lower given the Permian strata’s comparatively low hydraulic conductivity (see Section 2.6). Estimates of recharge to the alluvium are highly variable, but are typically in the range of 1 to 5% of rainfall for bedrock units (see Section 2.6.2).

2.7.3 Discharge

Groundwater discharge occurs via evapotranspiration from shallow watertables, groundwater pumping (primarily for irrigation and potable water supply), and via

1 Kansas Geological Survey (KGS, 1996) defines a hydrostratigraphic unit as follows: a rock unit distinguished and characterised by its porosity and hydraulic conductivity. Delineation of these units subdivides the geologic framework into relatively more or less permeable portions and thus aids in definition of the flow system.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 43

baseflow to streams, particularly for streams emanating from the Liverpool Range (although as noted previously the Mooki River is considered a predominantly losing stream with only baseflow accession south of Caroona). A minor component of groundwater discharge is likely to occur via the bedrock down-geologic basin to the south-west due to increasing strata thicknesses, and therefore greater transmissivity and greater groundwater flow rates in this direction. Groundwater flow through the Mooki plain alluvial sediments that does not discharge via groundwater pumping, baseflow or evapotranspiration discharges in a northerly direction towards and beyond Gunnedah in the Namoi system.

2.7.4 Hydraulic Properties

Data collected for the Project and other independent studies suggests that the hydraulic conductivity of the Permo-Triassic units decreases with burial depth. This is attributed to fractures (and pore space) being less prevalent at depth due to increasing overburden pressure. The Permo-Triassic groundwater system ranges from unconfined in outcrop areas to semi-confined at greater depths. The alluvium tends to form unconfined to semi-confined zones that are significantly more permeable than the hard rock units, and therefore transmits groundwater at greater flow rates.

2.7.5 Impact of Mining on Overburden

The impact of mining on the hydraulic conductivity of caved overburden has been based on monitoring experience and groundwater modelling conducted in similar mining environments, including research available on free draining heights.

It is generally accepted that there will be a sequence of deformational zones (Figure 26) usually described as:

 the caved zone;

 the fractured zone, consisting of:

. a lower zone of connective-cracking;

. an upper zone of disconnected-cracking;

 the constrained zone; and

 the surface cracking zone.

The rocks in the connective-cracking part of the fractured zone will have a substantially higher vertical hydraulic conductivity than the undisturbed (‘host’) rocks. This allows the free draining of groundwater downward towards the goaf. Above that in the disconnected-cracking zone the vertical flow of groundwater is impeded.

Depending on the width of the longwall panels, depth of cover and worked coal seam thickness, there is normally a constrained zone in the overburden that

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 44

prevents vertical groundwater flow. In this zone, dilation of strata causes an increase in horizontal hydraulic conductivity.

In the near surface zone, fracturing can occur due to tensional forces, but field evidence indicates this is usually restricted to a depth of less than 20 m from the ground surface.

At the base of the fractured zone, groundwater pressures will reduce towards atmospheric pressure, and consequently over a short time the majority of the fractured/disturbed zone would become a free-draining zone.

2.7.6 Water Balance Changes Due to Mining

These depressurisation impacts, and the resulting mine groundwater inflows, will result in changes to groundwater discharge such as baseflow to streams, down- geologic basin flow, and evapotranspiration. Hydraulic properties will control the spatial (lateral and vertical) and temporal migration of these changes, and ultimately their location, timing and magnitude.

The depressurisation impacts will potentially also take water from groundwater storage, and because mining-induced fracturing of rock strata will alter (increase) groundwater storage properties, in the long term, more water will end up in groundwater storage than was the case pre-mining2. This will in turn cause changes to groundwater discharge.

2 Within the strata portions that remain saturated within the mining footprint. Water is lost from storage overall however due to drawdown.

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 45 !#

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Bureau of Meteorology (2013) # !# # !# !# !# 750.01 - 900 ! 1961-1990 !# !# ! !# !#!# !# River !# !#!# !# !# # !# !# !# !# !#!# !# ! !# 900.01 - 1,050 DrawingNo: CAR001-018 Scale: 480,000 @ A4 # !# !# Creek # !# Rev: b. ! ! !# GDA 1994 MGA Zone 56 # !# >1,050 Created by: CNicol ° ° !#!# !# ! !# Date: 10/02/2014. !# # !# !# # !# !# !# !# !# ! !# # !# !# (C) 2014. While! HydroSimulations has taken care to ensure the accuracy of this product, !# ! !#!#!# HydroSimulations, Bureau of Meteorology, Geoscience Australia and NSW Government 02.5 5 10 15 20 !# # make no representations or warranties about its accuracy, completeness or suitability for any#!# !# km # !# !# ! !#!# !# particular purpose and cannot accept liability of any kind (whether in contract, tort or ! ! !# !# !# !#!# !# !# !# !# D:\HydroSim\CAR001\GIS\Maps\Deliverable\018_Rainfall.mxd # !# !# ! !# !# !# !# # !# !# !# # !# !# !# ! !# # ! !# !# !# !# !# !# !# ! !# !# !# !# !# !# # !# !# !# !# !# !# ! # !# !# # ! # ! ! !# !# !# !# !# # !# # !# ! !# # !# !# ! !# !# ! !# !# # # !# !# !# # !# !# !# ! ! # !# !# !# ! !# !# !# ! !# !# !# !# !## !# !#!# !# ! !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !#!# !# # !# !# !# !# ! !# !# !# # !# !# !# # !!# !# !# !#!# !# !#!# ! !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# # !# !# !# !# !# ! # !# !# !# !#!# ! !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !#!# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# !# # !# !#!# ! 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Figure 6 Annual Rainfall Cumulative Distribution Function for Station 055039 at Spring Ridge from 1922 to 2013

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 47

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Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 50

Source: http://atlas.nsw.gov.au/08ba07004524d3c58bf4ff80f0360a0e/Sedimentary%2BBasins.png

Figure 10 Geological Basins of New South Wales

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 51

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Geology Dz Jgv Pb Pli ") Pnc Puo Pwc Rdc 6480000 Cas Ja Jps Pbr Plt Pps Put Pwf Rns Cbc Jgi Jpx Plf Pmx Psw Pwb Qx Tl

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Town River Seam Subcrop 6470000 (( (( )" Village Creek Thrust Fault BHP Billiton (( ") Locality Targeted Exploration Area Interpreted Fault Caroona Coal Project Exploration Licence Figure 11

Geological Outcrop

DrawingNo: CAR001-013 Rev: B. Scale: 480,000 @ A4 Created by: CNicol ° GDA 1994 MGA Zone° 56 Date: 13/01/2014.

D:\HydroSim\CAR001\GIS\Maps\Deliverable\013_Geology.mxd

Figure 12 Stratigraphy

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 53 )" 220000 230000 240000 250000 260000 270000 280000 290000 ") ") PORCUPINE LOOKOUT

WINTON ") 6560000

BITHRAMERE CURLEWIS ") ") MILROY ")

PIALLAWAY ") 6550000

BREEZA CURRABUBULA " ") ) ") BELGAMBA 6540000

SQUARE BUSH ")

BURILDA ") WERRIS CREEK ")

BAKANA") 6530000 ") NARDU TURILAWA ") SPRING RIDGE CAROONA ") )" QUIPOLLY ") LOWER QUIPOLLY ")

COLLY 6520000 BLUE ") PINE RIDGE )" BORAMBIL ") ") QUIRINDI 6510000

COOMOO BRAEFIELD COOMOO ") ")

WARRAH RIDGE ") YARRAMAN THE SEVEN ") MILE ") WINDY ") WILLOW 6500000 BLACKVILLE TREE ") ")

WARRAH ") OLD") WARRAH KANKOOL ") WARRAH CREEK ") 6490000 ARDGLEN Groundwater flow direction PARRAWEENA ") ") PANGELA ")

CATTLE CREEK BIG JACKS ") LITTLE CREEK JACKS ") MACDONALDS CREEK ") CREEK ") 6480000 Watertable Bores Watertable elevation Exploration Licence (mAHD) Observation Bore Targeted Exploration Area BHP Billiton Time of Drilling 247.19 - 290 Caroona Coal Project ") Town 290.01 - 330 Figure 13 )" Village 330.01 - 370 Interpolated Watertable ") Locality 370.01 - 410 Elevation (February 2010) River 410.01 - 450 DrawingNo: CAR001-015 Creek 450.01 - 490 Rev: C. Scale: 430,000 @ A4 Created by: CNicol ° GDA 1994 MGA Zone° 56 490.01 - 634.92 Date: 10/02/2014.

(C) 2013. While HydroSimulations has taken care to ensure the accuracy of this product, HydroSimulations, Geoscience Australia and NSW Government make no representations or 02.25 4.5 9 13.5 18 warranties about its accuracy, completeness or suitability for any particular purpose and km cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses,

D:\HydroSim\CAR001\GIS\Maps\Deliverable\015_Watertable Contours.mxd 240000 250000 260000 270000

BREEZA

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") 6500000

Watertable Bores Watertable Depth (m) Exploration Licence ") BHP Billiton Observation Bore <=2 Targeted Exploration Area Caroona Coal Project Time of Drilling 2.01 - 5 ") Town 5.01 - 10 Figure 14 )" Village 10.01 - 25 Interpolated Watertable ") Locality 25.01 - 50 Depth (February 2010) DrawingNo: CAR001-016 River 50.01 - 100 Rev: B. Scale: 230,000 @A4 Created by: CNicol ° GDA 1994 MGA Zone° 56 Creek >100 Date: 16/01/2014.

(C) 2013. While HydroSimulations has taken care to ensure the accuracy of this product, HydroSimulations, Geoscience Australia and NSW Government make no representations or 01.25 2.5 5 7.5 10 warranties about its accuracy, completeness or suitability for any particular purpose and km cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses,

D:\HydroSim\CAR001\GIS\Maps\Deliverable\016_Watertable Depth.mxd

Figure 15 Potentiometric Head Cross-Sections for September 2009

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 56 240000 250000 260000 270000

BREEZA

") 6540000

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BURILDA ") C113

C199A-5 GW030010/1 C193A-1 C199A-3 C199A-2 C119A C193A-2 C199A-4 C188-1 C188-3 6530000 C188-2 C180A C188-5 C102A TURILAWA BAKANA") C182-2 C102B C102D C089A C268-3 ") C182-1 NARDU C285 C102C ") C265 C168B C151 C282A C168A C078A C076 SPRING GW030380 C162 GW030078 RIDGE C043 C050 ") C243 C153A )" GW965576 C037 CAROONA

C023 GW030083/1 GW030083/2 C017 C011 GW030063/2 ")

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BHP Billiton Legend Caroona Coal Project ") Town DWE Monitoring Bores Exploration Licence )" Village Vibrating Wire Piezometers Targeted Exploration Area Figure 16 ") Locality Standpipe Piezometer Bores Alluvials Existing Groundwater River NOW Registered Bores Monitoring Bores Creek DrawingNo: CAR001-014 Rev: C. Scale: 200,000 @A4 Created by: CNicol ° GDA 1994 MGA Zone° 56 Date: 13/02/2014.

(C) 2013. While HydroSimulations has taken care to ensure the accuracy of this product, HydroSimulations, Geoscience Australia and NSW Government make no representations or 01 2 4 6 8 warranties about its accuracy, completeness or suitability for any particular purpose and km cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses,

D:\HydroSim\CAR001\GIS\Maps\Deliverable\014_GW Monitoring.mxd 450

400

350

300

250

200

150 Estimated Groundwater Use ML/day 100

0 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Source: NOW Upper Namoi groundwater flow model (C. McNeilage, pers. comm. 2013).

Figure 17 Estimated Historical Alluvial Groundwater Use

18/03/20145:37 PM D:\HydroSim\CAR001\Tech\Groundwater\Usage\NOW_un_GWABS.xlsx (Figure 17)

Figure 18 Regional Groundwater TDS Data Summary (from AGE, 2013)

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 59

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6530000 6520000 0

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Figure 20 Coal seam hydraulic conductivity (from AGE, 2013)

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 61

Samples preferentially collected for high porosity appearance, so results indicative of higher end of likely range.

Figure 21 Summary oof Clare Sandstone hydraulic conductivity (from AGE, 2013 and SCT, 2012)

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 62

Figure 22 Summary of Interburden hydraulic conductivity (from AGE, 2013 and SCT, 2012)

Caroona Coal Project: Gateway Application Preliminary Groundwater Assessment 63 1000 100 BREEZA

100 60

40 10

1 0 Flow Flow (ML/day) Flow Flow Gain / Loss -20

0.1 -40

-60 0.01

-80

0.001 -100 May-03 Nov-03 May-04 Nov-04 May-05 Nov-05 May-06 Nov-06 May-07 Nov-07 May-08 Nov-08 May-09 Nov-09 May-10 Nov-10 May-11 Nov-11 May-12 Nov-12 May-13 Nov-13 May-14

TOTAL REACH INFLOWS (MOOKI @ CAROONA+QUIRINDI @ GREENACRES) Average Median DOWNSTREAM (MOOKI@BREEZA) FLOW Zero Gain / Loss Flow gain: 37.7 4.4 GAIN Flow loss: -43.8 -3.6 LOSS Gain/loss: -7.3 -0.5 Figure 23 Mooki River Flow Gains and Losses between Caroona and Breeza

18/02/20145:20 PM D:\HydroSim\CAR001\Tech\Surface Water\surface water stations_table5fig8.xlsx (419027_streamflow) 305

300

295 Downward potential from Quirindi Creek into the Narrabri Alluvium. Approximately 10m thick probable unsaturated zone beneath creek. No potential for baseflow gains at this location.

290 Elevation (mAHD) Elevation

285

Est. Stream bed RL Est. Stream Water Level GW030378_1 GW030378_2 GW030380_1 280 May-03 Oct-03 May-04 Oct-04 May-05 Nov-05 May-06 Nov-06 May-07 Nov-07 May-08 Nov-08 May-09 Nov-09 May-10

Figure 24 Groundwater Surface Water Interaction at Lower Quirindi Creek

18/02/20145:18 PM D:\HydroSim\CAR001\Tech\Groundwater\GWLevels\GW030380_78_CrossSection.xlsx (Figure 23) Breeza shelf restricts northward alluvial groundwater flow, creates shallow watertables WERRIS CREEK

CAROONA Evapotranspiration from shallow groundwater BREEZA

Diffuse rainfall Diffuse rainfall and recharge on plains irrigation recharge on Mooki plains

Lake Goran (large areas dry)

Poorly permeable bedrock, high runoff, low recharge

Red text: Recharge/runoff process Blue text: groundwater flow/discharge process Groundwater pumping bore Vertical exaggeration: 15 Source: D:\HydroSim\CAR001\WP\Figures_Rev3\Figure 22 Conceptual model.pptx Figure 25 Conceptual Hydrogeological Model