Australasian Groundwater and Environmental Consultants Pty Ltd (AGE) Report on United Wambo Open-Cut Coal Mine Project Groundwater Impact Assessment Prepared for Umwelt Australia Pty Ltd Project No. G1733 July 2016 www.ageconsultants.com.au ABN 64 080 238 642
Document details and history Document details Project number Document title Site address File name G1733 United Wambo Open Cut Coal Mine Project Groundwater Impact Assessment Golden Highway Jerrys Plains NSW G1733A United GIA EIS_7.docx Document status and review Edition Comments Author Authorised by Date Draft 1 Issued for client comment and review CS JST 16/12/2015 Draft 2 Issued for client comment and review CS JST 28/1/2016 Draft 3 Issued for client comment and review CS JST 18/3/2016 Final CS JST 8/7/2016 This document is and remains the property of AGE, and may only be used for the purpose for which it was commissioned and in accordance with the Terms of Engagement for the commission. Unauthorised use of this document in any form whatsoever is prohibited. AGE Head Office Level 2 / 15 Mallon Street, Bowen Hills, QLD 4006, Australia T. +61 7 3257 2055 F. +61 7 3257 2088 brisbane@ageconsultants.com.au AGE Newcastle Office 4 Hudson Street, Hamilton, NSW 2303, Australia T. +61 2 4962 2091 F. +61 2 4962 2096 newcastle@ageconsultants.com.au
Table of contents Page No. 1 Introduction... 1 1.1 Project description... 1 1.1.1 Approved operations... 1 1.1.2 Proposed Project... 5 1.2 Objectives and scope of work... 5 1.3 Report structure... 8 2 Regulatory framework... 9 2.1 Water Management Act 2000... 9 2.2 Commonwealth Environment Protection and Biodiversity Conservation Act 1999... 10 2.3 Water sharing plans... 10 2.4 State groundwater policy... 11 2.4.1 Aquifer Interference Policy... 11 2.4.2 Groundwater quality protection... 19 2.4.3 Groundwater dependent ecosystems... 19 2.4.4 Groundwater quantity management... 20 2.4.5 Strategic agricultural land... 20 2.5 Water licensing... 20 3 Environmental setting... 22 3.1 Location... 22 3.2 Climate... 22 3.3 Terrain... 24 3.4 Drainage... 26 3.5 Land use... 29 4 Geological setting... 31 4.1 Regional geology... 31 4.2 Local geology... 36 4.2.1 Quaternary to Tertiary aged sediments... 36 4.2.2 Tertiary volcanics... 38 4.2.3 Triassic Narrabeen Group... 38 4.2.4 Permian Newcastle Coal Measures... 38 4.2.5 Permian Watts Sandstone... 38 4.2.6 Permian Wittingham Coal Measures... 38 4.3 Geological structure... 39 5 Hydrogeology... 41 5.1 Existing data and monitoring... 41 5.2 Hydraulic parameters... 41 5.3 Groundwater recharge, distribution and flow... 44 5.4 Groundwater quality... 48 5.4.1 Groundwater characteristics... 48 United Wambo Project - Groundwater Impact Assessment (G1733) i
Table of contents (continued) Page No. 5.4.2 Beneficial use of groundwater... 49 5.5 Groundwater use... 52 5.5.1 Private water users... 52 5.5.2 Groundwater dependent ecosystems... 55 5.6 Conceptual model... 58 6 Numerical groundwater model... 61 6.1 Overview of mining... 61 6.1.1 Proposed mine plan... 61 6.2 Overview of groundwater modelling... 61 6.3 Peer review... 63 7 Model predictions and impact assessment... 65 7.1 Project groundwater predictions... 65 7.1.1 Groundwater intercepted by mining... 65 7.1.2 Drawdown and depressurisation during mining operations... 66 7.1.3 Change in alluvial water resources... 73 7.1.4 Changes to surface water flow... 75 7.1.5 Water licensing... 76 7.1.6 Drawdown in private and mine owned bores... 78 7.1.7 Impact on groundwater dependent ecosystems... 79 7.2 Cumulative drawdown... 81 7.3 Post mining recovery conditions... 88 7.3.1 Post closure groundwater recovery... 88 7.3.2 Permian groundwater intercepted post mining... 95 7.3.3 Change in alluvial flow post mining... 95 7.3.4 Change in surface water flow post mining... 96 7.4 Groundwater quality changes... 97 7.4.1 Overburden emplacement areas and final void lakes... 97 7.4.2 Hydrocarbons... 97 7.4.3 Water storage... 97 7.5 Model uncertainty... 98 8 Compliance with NSW government policy... 99 8.1 Aquifer Interference Policy... 99 9 Compliance with Commonwealth government policy...103 9.1 EPBC Act Significant Impact on Water Resources Guidelines...103 9.1.1 Water availability to users... 103 9.1.2 Water availability to the environment... 103 9.1.3 Water quality... 104 9.1.4 Cumulative impacts... 104 9.1.5 Avoidance or mitigation measures... 104 9.1.6 Tabulated impacts... 105 United Wambo Project - Groundwater Impact Assessment (G1733) ii
Table of contents (continued) Page No. 10 Groundwater monitoring and management plan...107 10.1 Water level monitoring plan...113 10.2 Water quality monitoring plan...113 10.3 Trigger levels...113 10.3.1 Water quality triggers... 114 10.3.2 Water level triggers... 114 10.4 Mine water seepage monitoring...115 10.5 Future model iterations...116 10.6 Data management and reporting...116 10.7 Management and mitigation strategies...116 11 References...117 12 Glossary & Acronyms...119 United Wambo Project - Groundwater Impact Assessment (G1733) iii
Table of contents (continued) Page No. List of figures Figure 1-1 General location plan... 4 Figure 1-2 Proposed Project... 7 Figure 2-1 Productive groundwater... 18 Figure 3-1 Cumulative Rainfall Departure (SILO) and monthly rainfall (Jerrys Plains and site SILO)... 23 Figure 3-2 SILO average monthly rainfall, evaporation and evapotranspiration... 24 Figure 3-3 Terrain and drainage... 25 Figure 3-4 Baseflow in Wollombi Brook at Warkworth (210004)... 26 Figure 3-5 Baseflow in Hunter River at Liddell (210083)... 27 Figure 3-6 Interpolated gaining and losing stream and alluvial zones... 28 Figure 3-7 Historic and existing mining... 30 Figure 4-1 Regional surface geology... 33 Figure 4-2 Conceptualised geological cross section through Project Area... 34 Figure 4-3 Project site surface geology... 35 Figure 4-4 Structure and thickness contours of the unconsolidated sediments... 37 Figure 4-5 Structure and thickness contours of Wittingham Coal Measures... 40 Figure 5-1 Histogram of horizontal hydraulic conductivity (Kh) distribution... 42 Figure 5-2 Hydraulic conductivity vs. depth coal... 43 Figure 5-3 Hydraulic conductivity vs. depth interburden... 43 Figure 5-4 Hydrographs comparing groundwater trends and Wollombi Brook levels... 44 Figure 5-5 Groundwater levels and saturated thickness Quaternary alluvium... 46 Figure 5-6 Groundwater levels and flow direction Wittingham Coal Measures (Vaux Seam)... 47 Figure 5-7 Mg/Na scatterplot and Na/SO 4 scatterplot of groundwater quality... 48 Figure 5-8 Surface water TDS histogram... 49 Figure 5-9 Wollombi Brook TDS over time... 50 Figure 5-10 Groundwater TDS histogram... 51 Figure 5-11 Groundwater use... 54 Figure 5-12 Groundwater dependent ecosystems... 57 Figure 5-13 Schematic section showing conceptual hydrogeology west to east... 59 Figure 5-14 Schematic section showing conceptual hydrogeology south to north... 60 Figure 6-1 Model extent... 64 Figure 7-1 Groundwater intercepted from Permian coal measures... 66 Figure 7-2 Maximum zone of drawdown due to Project Quaternary alluvium... 68 United Wambo Project - Groundwater Impact Assessment (G1733) iv
Table of contents (continued) Page No. Figure 7-3 Maximum zone of drawdown due to Project Wambo Seam... 69 Figure 7-4 Maximum zone of drawdown due to Project Glen Munro Seam... 70 Figure 7-5 Maximum zone of drawdown due to Project Arrowfield Seam... 71 Figure 7-6 Maximum zone of drawdown due to Project Vaux Seam... 72 Figure 7-7 Net change in flow from Permian to Wollombi Brook alluvium due to mining... 73 Figure 7-8 Net change in flow from Permian to Hunter River alluvium due to mining... 74 Figure 7-9 Wollombi Brook baseflow change... 75 Figure 7-10 Hunter River baseflow change... 76 Figure 7-11 Partitioning of water take from streams and alluvium for the Project... 78 Figure 7-12 GDEs and predicted maximum cumulative drawdown in alluvium... 80 Figure 7-13 Predicted groundwater level decline in alluvium at zone GDE1... 81 Figure 7-14 Cumulative drawdown Quaternary alluvium... 83 Figure 7-15 Cumulative drawdown Wambo Seam... 84 Figure 7-16 Cumulative drawdown Glen Munro Seam... 85 Figure 7-17 Cumulative drawdown Arrowfield Seam... 86 Figure 7-18 Cumulative drawdown Vaux Seam... 87 Figure 7-19 Pit lake recovery... 89 Figure 7-20 Post mining equilibrium drawdown and potentiometric surface Quaternary alluvium and regolith... 90 Figure 7-21 Post mining equilibrium drawdown and potentiometric surface Wambo Seam... 91 Figure 7-22 Post mining equilibrium drawdown and potentiometric surface Glen Munro Seam 92 Figure 7-23 Post mining equilibrium drawdown and potentiometric surface Arrowfield Seam. 93 Figure 7-24 Post mining equilibrium drawdown and potentiometric surface Vaux Seam... 94 Figure 7-25 Net change in flow from Permian to alluvium post mining... 95 Figure 7-26 River baseflow change post mining... 96 Figure 10-1 Groundwater monitoring network...112 Figure 10-2 Example of a control chart (after DERM 2010)...114 Figure 10-3 Example of a water level trigger event...115 United Wambo Project - Groundwater Impact Assessment (G1733) v
Table of contents (continued) Page No. List of tables Table 1-1 Summary of historical mine workings and target seams... 2 Table 2-1 Minimal Impact Considerations for Aquifer Interference Activities (DPI Water 2012). 14 Table 2-2 Water licensing... 21 Table 3-1 Climate averages... 22 Table 3-2 Summary of approved mines in Wittingham Coal Measures... 29 Table 4-1 Summary of regional geology... 32 Table 5-1 Existing and usable private bores by stratigraphic unit within 4km of Project... 53 Table 7-1 Groundwater licensing summary during mining... 77 Table 7-2 Predicted cumulative drawdown over 2m in private and mine owned bores... 78 Table 8-1 Accounting for or preventing the take of water... 99 Table 8-2 Determining water predictions...101 Table 8-3 Other requirements...102 Table 9-1 Table 9-2 Summary of impacts to the hydrology of the water resource compared to the DoE guidelines...105 Summary of impacts to the water quality of the water resource compared to the DoE guidelines...106 Table 10-1 Proposed site monitoring network...107 List of appendices Appendix A Appendix B Appendix C Appendix D Appendix E Field investigation report Numerical modelling report Study requirements Peer Review Report Stygofauna assessment United Wambo Project - Groundwater Impact Assessment (G1733) vi
Report on United Wambo Open Cut Coal Mine Project Groundwater Impact Assessment 1 Introduction United Mine (United) and Wambo Mine (Wambo) are situated approximately 16 kilometres (km) west of Singleton in the Hunter Valley of New South Wales (NSW) (Figure 1-1). United is owned 95 per cent by Glencore Coal Pty Limited (Glencore) and 5 per cent by the Construction, Forestry, Mining and Energy Union (CFMEU) and is managed by Glencore. Wambo is an existing coal mining operation and is a neighbour operation to United. Wambo Coal Pty Limited (Wambo Coal) is a subsidiary of Peabody Energy Australia Pty Limited (Peabody). In November 2014, a 50:50 Joint Venture between United Collieries Pty Limited (United Collieries) and Wambo Coal Pty Limited (Wambo Coal) was announced which combines the extraction and exploration rights for a number of mining tenements at United and Wambo. The Joint Venture will look to develop the United Wambo Open Cut Coal Mine Project (the Project) that combines the existing open cut operations at Wambo with a proposed new open cut coal mine at United. The Project is a State Significant Development as defined under State Environmental Planning Policy (State and Regional Development) 2011 and will require development consent under Part 4 of the Environmental Planning and Assessment Act 1979 (EP&A Act). The Project will also require a modification to the existing Wambo development consents under section 75W of the EP&A Act. An Environmental Impact Statement (EIS) has been prepared to accompany these applications. This groundwater assessment has been prepared by Australasian Groundwater and Environmental Consultants Pty Ltd (AGE) for the EIS for the Project. The groundwater assessment has been undertaken in accordance with the Secretary s Environmental Assessment Requirements (SEARs), NSW government requirements and the Commonwealth EPBC Act (Water Trigger). 1.1 Project description The Project Area is within Exploration Lease (EL) 7211, Authorisation (A) 444, Mining Lease (ML) 1572, Coal Lease (CL) 374 (which is stratified and exists below Consolidated Coal Lease (CCL) 775) and CCL775 (Figure 1-1). The Project involves application to modify the Wambo Development Consent (DA 305-7-2003). This groundwater study examined the groundwater related impacts associated with the Project, as well as the cumulative groundwater impacts of approved and reasonably foreseeable mines. 1.1.1 Approved operations The United and Wambo coal mining operations were established in 1989 and the late 1960 s, respectively. There have been a range of underground and open cut coal mining operations at both of these adjoining coal mines since that time, with a number of agreements entered into by United Collieries and Wambo Coal over time in relation to access to underground and open cut coal reserves within mining titles held by each company (Table 1-1). United Wambo Project - Groundwater Impact Assessment (G1733) 1
Table 1-1 Summary of historical mine workings and target seams Reference name Mine area Seam Start date End date Hunter Pit Whynot 1969 2011 Wombat Pit Whynot 1969 2009 Homestead Pit Whynot 1969 2016 South Bates Pit Whynot 1969 2016 Eastern Pit Whybrow 1974 1982 Western Pit Whybrow 1974 1983 Wambo Open cut North Bates Pit Whybrow 1980 1987 Ridge Pit Whybrow 1986 1988 North East Pit Wambo 1988 1998 Whynot Pit Whynot 1991 1998 Wollemi Boxcut Whybrow 2002 2005 Wambo Pit Whynot 2012 2017 Montrose Pit Whybrow 2013 2020 Wambo No.1 Underground Wambo and Whybrow 1969 1977 Ridge Underground Whybrow 1976 1983 Homestead and Wollemi Underground Whybrow 1979 2002 Wambo Underground North Wambo Underground Wambo 2007 2019 South Bates Underground Whybrow and Wambo 2014 2018 Arrowfield Underground (South Wambo)* Arrowfield 2017 2032 Bowfield Underground (South Wambo) Bowfield 2021 2028 Woodlands Hill Underground (South Wambo)* Woodlands Hill 2019 2029 United Open Cut - Whynot to Wambo 1989 1992 United Underground - Arrowfield 1992 2010 Note: * Part of Modification 12 United Wambo Project - Groundwater Impact Assessment (G1733) 2
Whilst open cut coal mining has previously been undertaken at United, over the last two decades the focus has been on underground mining. Underground longwall mining operations were approved to provide up to 2.95 million tonnes per annum (Mtpa) of saleable coal. Operations were suspended at United in March 2010 with the mine entering a period of care and maintenance. At that time, exploration and pre-feasibility works were commenced to determine the potential for future mining activities within United s mining lease. Ongoing exploration has identified substantial reserves of coal suitable for open cut mining. The current existing and approved Wambo open cut coal mine adjoins the United operations, and was planned to produce up to 8 Mtpa of run of mine (ROM) coal up to 2017. The combined Wambo underground and open cut operations, have approval to extract up to 14.7 Mtpa run of mine (ROM) coal, and to transport up to 15 Mtpa product coal via the approved train loading facility until 2025. Open cut mining at Wambo is conducted using a truck and excavator operation. Run-of-mine (ROM) coal is crushed at on-site coal handling facilities. Product coal is transported by conveyor to the Train Load Out facility for train loading. Product coal is transported by rail to domestic customers and the Newcastle Port for export. Wambo Mine operates under development consent (DA 305-7-2003), which is approved until 2025. The open cut operations comprise 14 pits mining down to the Whybrow, Wambo or Whynot seams, as detailed in Table 1-1. For the purposes of this assessment, all approved open cut mining at Wambo is referred to as the Wambo Open cut. Wambo Mine has three main in-pit reject emplacement areas (Homestead, Hunter and Main Homestead). In addition, storage of water within existing longwall panels at United has also been proposed; however this is dependent on operational requirements and is not included within the Project plans. United comprises open cut and underground operations. The United Open cut targeted the Whynot and Wambo seams between 1989 and 1992. The United Underground operations used continuous miner, bord and pillar and then chain haulage systems to mine the Arrowfield Seam (Woodlands Hill) 1 until 2002. From 2002 to 2010, longwall mining was conducted at Longwall panels 1 to 10. Longwall panels 1 to 10 mined the Arrowfield Seam. During active mining, coarse rejects and fine tailings were disposed of in the United reject emplacement area, which includes Tailings Dam 1 (TD1) and Tailings Dam 2 (TD2). Since 2010, United has been in care and maintenance. Approved coal mines are also present to the north, east and south of the Project Area, which are discussed further in Section 3. 1 The Arrowfield Seam is referred to as the Woodlands Hill Seam by United Collieries. United Wambo Project - Groundwater Impact Assessment (G1733) 3
1.1.2 Proposed Project The Project includes open cut mining operations in two areas, the proposed United Open Cut and modified operations in the approved Wambo Open Cut for a period of approximately 23 years. The existing Wambo Open Cut has approval for continued open cut mining until 2017. The Project seeks to modify the approved mine plan for the Wambo Open Cut to access additional resources from within existing mining and exploration tenements held below the Wambo Open Cut. The Wambo and United open cut operations are approved to mine to the Whynot Seam beneath the Wambo Seam. The approved extent of the open cut pits are shown in Figure 1-2. As part of the modification, the United Open Cut and Wambo Open Cut are proposed to be extended and mined to the base of the Vaux Seam and Warkworth Seam, respectively (Figure 1-2). The Joint Venture is anticipated to deliver up to 10Mtpa of ROM coal production in total from the combined management of the United Open Cut and Wambo Open Cut mines. The existing Wambo Coal Handling and Preparation Plant (CHPP) will be utilised for the Project, with no change proposed to the CHPP s approved annual throughput of 14.7 Mtpa ROM coal feed. The Wambo CHPP will also continue to receive coal from the ongoing Wambo underground mine (that is not the subject of this Project). Further details about the geology of the site, including a stratigraphic column showing the sequence of the main coal seams are included in Section 4. The Project also involves a revised final landform, which includes a proposed in-pit tailings facility at South Bates Pit and final voids within the United and Wambo open cuts (Figure 1-2). The voids will replace the currently approved voids located within the Wambo Open Cut (Figure 1-2). 1.2 Objectives and scope of work The objective of the groundwater study was to assess the impact of the Project on the groundwater regime, and address the requirements of the NSW and Federal government legislation and policies. The groundwater study comprised two parts, a description of the existing hydrogeological environment, and an assessment of the impacts of mining on that environment. The groundwater impact assessment included: review and assessment of existing background data and filling data gaps with a program that included additional fieldwork (Appendix A); characterisation of groundwater sources including aquifer properties and quality; assessment on the potential interaction between the alluvium in the Hunter River, Wollombi Brook and Redbank Creek and the potential long term impacts to groundwater quantity and quality; consideration of, and as appropriate, modelling of the interaction between adjacent and nearby historical, current and approved and foreseeable future mining operations; estimation of groundwater make from the proposed operation from each groundwater system, for input into the water balance modelling being completed as part of a separate Surface Water Assessment; conceptualisation and development of a groundwater model in accordance with the National Groundwater Modelling Guidelines (National Water Commission, 2012) and relevant State and Commonwealth guidelines (Appendix B); assessment of cumulative impacts in relation to groundwater; final void recovery and water quality; United Wambo Project - Groundwater Impact Assessment (G1733) 5
assessment of the extent of groundwater impacts as a result of the operation of the proposed mine, including long term impacts on regional groundwater levels and water quality impacts on environmental flows and baseflows; assessment of potential groundwater dependant ecosystem (GDE) impacts resulting from short and/or long term changes in the quantity and quality of groundwater; quantify and assess, the potential third party impacts (i.e. private bores) as a result of changes to the regional groundwater system; detailed assessment against the Aquifer Interference Policy (2012); and provision of recommendations for the management and minimisation of groundwater impacts, including proactive mitigation strategies, and recommendations for monitoring. United Wambo Project - Groundwater Impact Assessment (G1733) 6
1.3 Report structure This report is structured as follows: Section 1 Introduction: provides an overview of the Project and the assessment scope. Section 2 Regulatory framework: describes the regulatory framework relating to groundwater. Section 3 Environmental setting: describes the environmental setting of the Project including the climate, terrain, land uses and other environmental features relevant to the Project. Section 4 Geological setting: describes the regional geology and local stratigraphy. Section 5 Hydrogeology: describes the existing local groundwater regime for the Project Area and surrounding area. Sections 6 and 7 Impact Assessment: provides a detailed description of the proposed mining activities and the potential effects on the local groundwater regime. This section also presents the predicted change on groundwater and the assessment of resulting impacts on groundwater users and the receiving environment. This section includes discussion on findings from the uncertainty analysis. Sections 8 and 9 Compliance with government policy: assesses the compliance of the groundwater assessment and findings to all relevant regulations. Section 10 Groundwater Monitoring and Management Plan: describes the proposed measures for monitoring and management of groundwater impact. Appendix A provides a detailed description of the available field data. This appendix comprises a summary of the investigation methods and includes a detailed summary of bore data for on-site and private bores, groundwater level and quality data for site monitoring bores and permeability data for various hydrogeological units. Appendix B provides a detailed description of the numerical modelling undertaken for the Project, including details on model construction, calibration and validation. Appendix B also describes the uncertainty analysis undertaken on the numerical groundwater model, including details about the purpose and methodology of the assessment. United Wambo Project - Groundwater Impact Assessment (G1733) 8
2 Regulatory framework The Department of Planning and Environment (DP&E) collated the requirements for the EIS from all NSW government departments and provided these for the Project. These are known as the Secretary s Environmental Assessment Requirements (SEARs). SEARs relevant to groundwater are presented in Appendix C, with information provided on where the requirements are addressed within this report. In addition to the SEARs the Project will need to consider the requirements of the following legislation, policy and guidelines for groundwater: NSW Government: o Water Management Act 2000 and the Water Sharing Plan for Hunter Regulated River Water Source, Hunter Unregulated and Alluvial Water Sources and North Coast Fractured and Porous Rock WSP; o Groundwater Quality Protection Policy (1998); o Groundwater Dependent Ecosystems Policy (2002); o Groundwater Quantity Management Policy (Policy Advisory Note No. 8); o o Aquifer Interference Policy (AIP)(2012); Strategic Regional Landuse Policy (SRLU Policy)(2012); and o Strategic Regional Landuse Plan Upper Hunter (2012). Commonwealth Government: o Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and related Independent Expert Scientific Committee (IESC) guidelines for coal seam gas (CSG) and large coal mining development proposals. Sections below summarise the intent of the above legislation, policy and guidelines and how they apply to the Project. 2.1 Water Management Act 2000 The NSW Water Management Act 2000 provides for the protection, conservation and ecologically sustainable development of the water sources of the State. The Water Management Act 2000 provides arrangements for controlling land based activities that affect the quality and quantity of the State s water resources. It provides for three primary types of approval in Part 3: water use approval which authorise the use of water at a specified location for a particular purpose, for up to 10 years; water management work approval; and controlled activity approval which includes an aquifer interference activity approval which authorises the holder to conduct activities that affect an aquifer such as activities that intersect groundwater, other than water supply bores and may be issued for up to 10 years. The Water Management Act 2000 includes the concept of ensuring no more than minimal harm for both the granting of water access licences and the granting of approvals. Aquifer interference approvals are not to be granted unless the Minister is satisfied that adequate arrangements are in force to ensure that no more than minimal harm will be done to any water source, or its dependent ecosystems, as a consequence of its being interfered with in the course of the activities to which the approval relates. United Wambo Project - Groundwater Impact Assessment (G1733) 9
While aquifer interference approvals are not required to be granted, the minimal harm test under the Water Management Act 2000 is not activated for the assessment of impacts. Therefore, the AIP establishes and objectively defines minimal impact considerations as they relate to water-dependent assets and as the basis for providing advice to either the gateway process, the Planning Assessment Commission or the Minister for Planning. The Project is a State Significant Development as defined under State Environmental Planning Policy (State and Regional Development) 2011 and will require development consent under Part 4 of the Environmental Planning and Assessment Act 1979 (EP&A Act). The Project will also require a modification to the existing Wambo development consents under section 75W of the EP&A Act. However, the Project will not require approval under sections 89, 90 or 91 of the Water Management Act 2000 due to the operation of section 75U of the EP&A Act. 2.2 Commonwealth Environment Protection and Biodiversity Conservation Act 1999 The Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) is administered by the Department of the Environment (DoE). The EPBC Act is designed to protect national environmental assets, known as Matters of National Environmental Significance (MNES). Under the 2013 amendment to the EPBC Act, impacts on groundwater resources were included, and are known as the water trigger. The Project was reviewed in accordance with the Significant impact guidelines 1.3 (DoE, 2013) and referred under the water trigger. The Project was then declared a Controlled Action by the DoE on 7 December 2015; therefore approval is required from the DoE for the impacts of the Project on water resources, including groundwater. The IESC is a statutory body under the EPBC Act that provides scientific advice to the Commonwealth Environment Minister and relevant state ministers. Guidelines have been developed in order to assist the IESC in reviewing CSG or large coal mining development proposals that are likely to have significant impacts on water resources. A summary of the IESC guidelines and where they are addressed within the report is included in Appendix C. 2.3 Water sharing plans NSW Water Sharing Plans (WSPs) establish rules for sharing water between the environmental needs of the river or aquifer and water users, and between different types of water use such as town supply, rural domestic supply, stock watering, industry and irrigation. The NSW Department of Primary Industries (DPI) Water is progressively developing WSPs for rivers and groundwater systems across NSW following the introduction of the Water Management Act 2000. The purposes of these plans are to protect the health of rivers and groundwater, while also providing water users with perpetual access licences, equitable conditions, and increased opportunities to trade water through separation of land and water. Three WSP s apply to the aquifers and surface waters affected by the Project. These are the WSP for the: Hunter Regulated River Water Source (Hunter Regulated WSP); Hunter Unregulated and Alluvial Water Sources 2009 (Hunter Unregulated WSP); and Water Sharing Plan for the North Coast Fractured and Porous Rock Groundwater Sources 2016 (North Coast Fractured and Porous Rock WSP). United Wambo Project - Groundwater Impact Assessment (G1733) 10
The North Coast Fractured and Porous Rock WSP commenced on 1 st July 2016 and replaces licensing under the Water Act 1912, which covered seepage of groundwater from the Permian and Triassic groundwater at the site. The proposed modification falls within the Sydney Basin North Coast Groundwater Source of the North Coast Fractured and Porous Rock WSP. The Hunter Regulated WSP covers the Hunter River surface water flows and highly connected alluvials described in the plan. The Hunter Unregulated WSP includes the unregulated rivers and creeks within the Hunter River catchment, the highly connected alluvial groundwater (above the tidal limit), and the tidal pool areas. In total, there are 39 water sources covered by the Hunter Unregulated WSP and nine of these are further sub-divided into management zones. The Project is located within the Wollombi Brook Management Zone within the Lower Wollombi Brook Extraction Management Unit. The Project is also located near the Jerrys Management Zone and Glennies Creek Management Zone. The alluvium along the Hunter River and Wollombi Brook are classified as containing both highly productive and less productive groundwater sources by DPI Water, as discussed further under Section 2.4. 2.4 State groundwater policy 2.4.1 Aquifer Interference Policy The Water Management Act 2000 defines an aquifer interference activity as that which involves any of the following: penetration of an aquifer; interference with water in an aquifer; obstruction of the flow of water in an aquifer; taking of water from an aquifer in the course of carrying out mining or any other activity prescribed by the regulations; and disposal of water taken from an aquifer in the course of carrying out mining or any other activity prescribed by the regulations. Examples of aquifer interference activities include mining, coal seam gas extraction, injection of water, and commercial, industrial, agricultural and residential activities that intercept the water table or interfere with aquifers. United Wambo Project - Groundwater Impact Assessment (G1733) 11
The AIP (Department of Primary Industries, 2012) states that: all water taken by aquifer interference activities, regardless of quality, needs to be accounted for within the extraction limits defined by the water sharing plans. A water licence is required under the WM Act (unless an exemption applies or water is being taken under a basic landholder right) where any act by a person carrying out an aquifer interference activity causes: the removal of water from a water source; or the movement of water from one part of an aquifer to another part of an aquifer; or the movement of water from one water source to another water source, such as: o o from an aquifer to an adjacent aquifer; or from an aquifer to a river/lake; or o from a river/lake to an aquifer. Proponents of aquifer interference activities are required to provide predictions of the volume of water to be taken from a water source(s) as a result of the activity. These predictions need to occur prior to Development Consent approval. After Development Consent approval and during operations, these volumes need to be measured and reported in an annual review. The water access licence must hold sufficient share component and water allocation to account for the take of water from the relevant water source at all times. The AIP states that a water licence is required for the aquifer interference activity regardless of whether water is taken directly for consumptive use or incidentally. Activities may induce flow from adjacent groundwater sources or connected surface water. Flows induced from other water sources also constitute take of water. In all cases, separate access licences are required to account for the take from all individual water sources. In addition to the volumetric water licensing considerations, the AIP requires details of potential: water level, quality or pressure drawdown impacts on nearby water users who are exercising their right to take water under a basic landholder right; water level, quality or pressure drawdown impacts on nearby licensed water users in connected groundwater and surface water sources; water level, quality or pressure drawdown impacts on groundwater dependent ecosystems; increased saline or contaminated water inflows to aquifers and highly connected river systems; to cause or enhance hydraulic connection between aquifers; and for river bank instability, or high wall instability or failure to occur. In particular, the AIP describes minimal impact considerations for aquifer interference activities based upon whether the water source is highly productive or less productive and whether the water source is alluvial or porous/fractured rock in nature. United Wambo Project - Groundwater Impact Assessment (G1733) 12
A highly productive groundwater source is defined by the AIP as a groundwater source which has been declared in regulations and datasets, based on the following criteria: a) has a Total Dissolved Solids (TDS) concentration less than 1500 mg/l; and b) contains water supply works that can yield water at a rate greater than 5 L/s. Highly productive groundwater sources are further grouped by geology into alluvial, coastal sands, porous rock, and fractured rock. Less productive groundwater sources are all other aquifers that do not satisfy the highly productive criteria for yield and water quality. The Hunter River alluvium and Wollombi Brook alluvium have bores that meet the criteria of the highly productive and less productive alluvial water source categories.. The Permian coal measures (porous and fractured rock) are categorised as less productive. The AIP defines the following Minimal Impact Considerations for highly productive and less productive groundwater. Table 2-1 summarises the Minimal Impact Considerations for the highly productive Hunter River alluvium and Wollombi Brook alluvium, and the less productive Permian coal measures. If these considerations are not met the Project needs to demonstrate to the Minister s satisfaction that the impact will be sustainable, or that make good agreements are in place. United Wambo Project - Groundwater Impact Assessment (G1733) 13
Table 2-1 Minimal Impact Considerations for Aquifer Interference Activities (DPI Water 2012) Category 1. Water Table Water Pressure Water Quality Highly productive alluvium Hunter River and Wollombi Brook Alluvium basal sands and gravels 1. Less than or equal to a 10% cumulative variation in the water table, allowing for typical climatic post-water sharing plan variations, 40 m from any: (a) high priority groundwater dependent ecosystem; or (b) high priority culturally significant site; listed in the schedule of the relevant water sharing plan; or A maximum of a 2 m decline cumulatively at any water supply work. 2. If more than 10% cumulative variation in the water table, allowing for typical climatic post-water sharing plan variations, 40 m from any (a) or (b) water sharing plan then appropriate studies(5) will need to demonstrate to the Minister s satisfaction that the variation will not prevent the long-term viability of the dependent ecosystem or significant site. If more than 2 m decline cumulatively at any water supply work then make good provisions should apply. 1. A cumulative pressure head decline of not more than 40% of the post-water sharing plan pressure head above the base of the water source to a maximum of a 2 m decline, at any water supply work. 2. If the predicted pressure head decline is greater than requirement 1. above, then appropriate studies are required to demonstrate to the Minister s satisfaction that the decline will not prevent the long-term viability of the affected water supply works unless make good provisions apply. 1. (a) Any change in the groundwater quality should not lower the beneficial use category of the groundwater source beyond 40 m from the activity; and (b) No increase of more than 1% per activity in long-term average salinity in a highly connected surface water source at the nearest point to the activity. Redesign of a highly connected (3) surface water source that is defined as a reliable water supply (4) is not an appropriate mitigation measure to meet considerations 1.(a) and 1.(b) above. (c) No mining activity to be below the natural ground surface within 200 m laterally from the top of high bank or 100 m vertically beneath (or the three dimensional extent of the alluvial water source - whichever is the lesser distance) of a highly connected surface water source that is defined as a reliable water supply. (d) Not more than 10% cumulatively of the three dimensional extent of the alluvial material in this water source to be excavated by mining activities beyond 200 m laterally from the top of high bank and 100 m vertically beneath a highly connected surface water source that is defined as a reliable water supply. 2. If condition 1.(a) is not met then appropriate studies will need to demonstrate to the Minister s satisfaction that the change in groundwater quality will not prevent the long-term viability of the dependent ecosystem, significant site or affected water supply works. If condition 1.(b) or 1.(d) are not met then appropriate studies are required to demonstrate to the Minister s satisfaction that the River Condition Index category of the highly connected surface water source will not be reduced at the nearest point to the activity. If condition 1.(c) or (d) are not met, then appropriate studies are required to demonstrate to the Minister s satisfaction that: - there will be negligible river bank or high wall instability risks; - during the activity s operation and postclosure, levee banks and landform design should prevent the Probable Maximum Flood from entering the activity s site; and - low-permeability barriers between the site and the highly connected surface water source will be appropriately designed, installed and maintained to ensure their long-term effectiveness at minimising interaction between saline groundwater and the highly connected surface water supply; United Wambo Project - Groundwater Impact Assessment (G1733) 14
Category 1. Water Table Water Pressure Water Quality Less productive alluvial water source surficial alluvium associated with major rivers (Hunter River and Wollombi Brook) and tributaries (Wambo Creek) Less productive porous rock Permian Coal Measures 1. A cumulative pressure head decline of not more than 40% of the post-water sharing plan (2) pressure head above the base of the water source to a maximum of a 2 m decline, at any water supply work. 2. If the predicted pressure head decline is greater than requirement 1. above, then appropriate studies are required to demonstrate to the Minister s satisfaction that the decline will not prevent the long term viability of the affected water supply works unless make good provisions apply. 1. A cumulative pressure head decline of not more than a 2 m decline, at any [private] water supply work. 1. (a) Any change in the groundwater quality should not lower the beneficial use category of the groundwater source beyond 40 m from the activity; and (b) No increase of more than 1% per activity in long-term average salinity in a highly connected surface water source at the nearest point to the activity. Redesign of a highly connected (3) surface water source that is defined as a reliable water supply (4) is not an appropriate mitigation measure to meet considerations 1.(a) and 1.(b) above. (c) No mining activity to be below the natural ground surface within 200 m laterally from the top of high bank or 100 m vertically beneath (or the three dimensional extent of the alluvial material - whichever is the lesser distance) of a highly connected surface water source that is defined as a reliable water supply. 2. If condition 1.(a) is not met then appropriate studies will need to demonstrate to the Minister s satisfaction that the change in groundwater quality will not prevent the long term viability of the dependent ecosystem, significant site or affected water supply works. If condition 1.(b) is not met then appropriate studies are required to demonstrate to the Minister s satisfaction that the River Condition Index category of the highly connected surface water source will not be reduced at the nearest point to the activity. If condition 1.(c) is not met, then appropriate studies are required to demonstrate to the Minister s satisfaction that: - there will be negligible river bank or high wall instability risks; - during the activity s operation and post closure, levee banks and landform design should prevent the Probable Maximum Flood from entering the activity s site; and - low-permeability barriers between the site and the highly connected surface water source will be appropriately designed, installed and maintained to ensure their long-term effectiveness at minimising interaction between saline groundwater and the highly connected surface water supply; 1. Any change in the groundwater quality should not lower the beneficial use category of the groundwater source beyond 40 m from the activity. United Wambo Project - Groundwater Impact Assessment (G1733) 15
Category 1. Water Table Water Pressure Water Quality 2. If the predicted pressure head decline is greater than requirement 1. above, then appropriate studies are required to demonstrate to the Minister s satisfaction that the decline will not prevent the long term viability of the affected water supply works unless make good provisions apply. 2. If condition 1 is not met then appropriate studies will need to demonstrate to the Minister s satisfaction that the change in groundwater quality will not prevent the long term viability of the dependent ecosystem, significant site or affected water supply works. United Wambo Project - Groundwater Impact Assessment (G1733) 16
As indicated under the Minimal Impact Considerations (Table 2-1), the AIP requires that impacts on highly and less productive water sources need to be assessed and accounted for. DPI Water has produced a map of groundwater productivity across NSW, which assigns zones of alluvium as highly and less productive alluvium. The DPI Water groundwater productivity map has been produced based on regional scale geological maps. Therefore, its accuracy was validated using site specific data available for the Project area. Lithological logs, water quality results and geophysical surveys, were used to refine the extent of highly productive alluvium. Geophysical surveys conducted along Wollombi Brook by GeoTerra (2003), GHD (2009) and Groundwater Imaging (2012) provided more detail on the extent of alluvial sediments. The studies found that the extent of alluvium was more restricted along the western banks of Wollombi Brook than is presented in regional mapping. This conclusion was based on identification of lithological characteristics representative of low permeability clay material and more permeable sands and gravels with geophysical interpretation, which was validated with lithological logs and permeability tests conducted at selected monitoring bores. Figure 2-1 shows the DPI Water groundwater productivity map and how the extent of the alluvium was adjusted to account for the Project Area data. The main changes are localised along the western bank of Wollombi Brook, near monitoring bores P15 to P20. The numerical groundwater model was developed and results extracted based on the adjusted extent of highly productive alluvium. The extent and characteristics of the highly productive alluvium is further discussed in Section 4. United Wambo Project - Groundwater Impact Assessment (G1733) 17
2.4.2 Groundwater quality protection The NSW Groundwater Quality Protection Policy (1998), states that the objectives of the policy will be achieved by applying the management principles listed below: All groundwater systems should be managed such that their most sensitive identified beneficial use (or environmental value) is maintained. Town water supplies should be afforded special protection against contamination. Groundwater pollution should be prevented so that future remediation is not required. For new developments, the scale and scope of work required to demonstrate adequate groundwater protection shall be commensurate with the risk the development poses to a groundwater system and the value of the groundwater resource. A groundwater pumper shall bear the responsibility for environmental damage or degradation caused by using groundwaters that are incompatible with soil, vegetation and receiving waters. Groundwater dependent ecosystems will be afforded protection. Groundwater quality protection should be integrated with the management of groundwater quality. The cumulative impacts of developments on groundwater quality should be recognised by all those who manage, use, or impact on the resource. Where possible and practical, environmentally degraded areas should be rehabilitated and their ecosystem support functions restored. Section 5 describes the site-specific groundwater environmental values, quality and use within the Project Area and surrounds. 2.4.3 Groundwater dependent ecosystems The NSW Groundwater Dependent Ecosystems Policy (DLWC, 2002) is specifically designed to protect valuable ecosystems which rely on groundwater for survival so that, wherever possible, the ecological processes and biodiversity of these dependent ecosystems are maintained or restored for the benefit of present and future generations. The policy defines GDEs as communities of plants, animals and other organisms whose extent and life processes are dependent on groundwater. Five management principles establish a framework by which groundwater is managed in ways that ensure, whenever possible, that ecological processes in dependent ecosystems are maintained or restored. A summary of the principles follows: GDEs can have important values. Threats should be identified and action taken to protect them; groundwater extractions should be managed within the sustainable yield of aquifers; priority should be given to GDEs, such that sufficient groundwater is available at all times to meet their needs; where scientific knowledge is lacking, the precautionary principle should be applied to protect GDEs; and planning, approval and management of developments should aim to minimise adverse effects on groundwater by maintaining natural patterns, not polluting or causing changes to groundwater quality and rehabilitating degraded groundwater ecosystems where necessary. United Wambo Project - Groundwater Impact Assessment (G1733) 19
2.4.4 Groundwater quantity management The objectives of managing groundwater quantity in NSW are to (NOW, 2012): achieve the efficient, equitable and sustainable use of the State s groundwater; prevent, halt and reverse degradation of the State s groundwater and their dependent ecosystems; provide opportunities for development which generate the most cultural, social and economic benefits to the community, region, state and nation, within the context of environmental sustainability; and involve the community in the management of groundwater resources. 2.4.5 Strategic agricultural land The NSW Strategic Regional Land Use Policy applies to the Hunter Valley in which the Project resides. Biophysical Strategic Agricultural Land (BSAL) is land with high quality soil and water resources capable of sustaining high levels of productivity. BSAL occurs within the footprint of the Project, along the Hunter River Flood plain. Critical Industry Clusters (CIC) derived from this policy can be biophysical, equine or viticulture zones, (NSW Planning & Environment, 2013). These zones were defined by the following criteria: a concentration of enterprises that provides clear development and marketing advantages and is based on an agricultural product; the productive industries are interrelated; a unique combination of factors such as location, infrastructure, heritage and natural resources; of national and/or international importance; an iconic industry that contributes to the region s identity; and potentially substantially impacted by coal seam gas or mining proposals. Equine zones occur adjacent the Hunter River upstream of the Project. Likewise, Hayes Creek and Parsons Creek tributaries of Wollombi Brook upstream have adjacent viticulture zones. Figure 3-3 shows the locations of these land uses. 2.5 Water licensing Wambo currently hold a groundwater licence to abstract 1006ML/year from the Hunter Regulated WSP (Hunter River) and 70ML year from the Lower Wollombi Brook Water Source under the Hunter Unregulated WSP. Under the North Coast Fractured and Porous Rock WSP (formerly Water Act 1912), Wambo also hold licences to abstract 1647ML/year from the Porous Rock Water Source, plus an additional 24ML/year from licensed bores within the Porous Rock Water Source. United Collieries hold licences to abstract 300ML/year from the Hunter River under the Hunter Regulated WSP. United Collieries also hold a total of 300ML/year under the Hunter Unregulated WSP, with 100ML/year from the Wollombi Brook and an additional 200ML/year from Redbank Creek, which feeds into Wollombi Brook. United Collieries hold a licence to abstract 300ML/year from the Porous Rock Water Source. Under the Joint Venture, the proponents hold 1306ML/year for the Hunter Regulated WSP (Hunter River), 370ML/year for the Hunter Unregulated WSP and 1947ML/year under the North Coast Fractured and Porous Rock WSP (formerly Water Act 1912). The individual water licensing details are included in Table 2-2 below. United Wambo Project - Groundwater Impact Assessment (G1733) 20
Table 2-2 Water licensing Site Licence No. Approved extraction (ML/year) Expiry Abstraction purpose Location United WAL 10541 (20WA200928) 300 Perpetuity Extraction Hunter River Water Source United WAL 18549 (20WA208706) 100 19/11/2022 Extraction Lower Wollombi Brook Water Source United WAL 18445 (20WA208714) 200 13/03/2023 Extraction Lower Wollombi Brook Water Source United 20BL173464 300 2/05/2018 Wambo WAL 23897 70 Perpetuity Dewatering (underground) Wollombi Brook (Well No. 2) Porous Rock Water Source Lower Wollombi Brook Water Source Wambo 20AL200631 1000 Perpetuity Hunter River Pump Wambo 20WA200632 6 30/6/2017 Hunter River Pump Hunter River Water Source Hunter River Water Source Wambo 20BL168017 21/05/2012 Dewatering (Bore No. 2) Porous Rock Water Source Wambo 20BL172061 750 22/03/2014* Dewatering (Bore No.2a) Porous Rock Water Source Wambo 20BL173040 21/05/2017 Dewatering Bore Porous Rock Water Source Wambo 20BL173032 30/11/2016 Dewatering Bore Porous Rock Water Source Wambo 20BL173033 30/11/2016 Dewatering Bore Wambo 20BL173034 450 30/11/2016 Dewatering Bore Wambo 20BL173035 30/11/2016 Dewatering Bore Wambo 20BL166910 25/10/2018 Bore No. 1 Wambo 20BL168643 40 7/08/2013 Dewatering Wambo 20BL167738 57 11/09/2015 Dewatering Bore Wambo 20BL172061 98 3/05/2019 Dewatering Wambo 20BL173844 9 4/11/2019 Dewatering Bore Wambo 20BL132753 243 29/07/2018 Old Well No.1 Wambo 20BL166438 5 Perpetuity Well - Stock Porous Rock Water Source Porous Rock Water Source Porous Rock Water Source Porous Rock Water Source Porous Rock Water Source Porous Rock Water Source Porous Rock Water Source Porous Rock Water Source Porous Rock Water Source Porous Rock Water Source Wambo 20BL166906 19 Perpetuity Spearpoints irrigation Porous Rock Water Source Note: * Renewal lodged United Wambo Project - Groundwater Impact Assessment (G1733) 21
3 Environmental setting 3.1 Location The Project Area is located approximately 15km west of Singleton (Figure 1-1). The closest townships are Warkworth and Jerrys Plains, which are located 1km south-east and 7km north-west of the Project Area, respectively (Figure 1-1). 3.2 Climate The climate in the region is temperate and is characterised by hot summers with regular thunderstorms and mild dry winters. Climate monitoring data collected by the Bureau of Meteorology (BoM) was obtained for Jerrys Plains Station which is located about 6km to the north-west of United Mine. A number of recording stations are closer to the mine, but did not have a long term rainfall record. The Jerrys Plains Station has 131 years of rainfall data dating from 1884 to present. Climate data was also obtained from the Scientific Information for Land Owners (SILO) database of historical climate records for Australia (DSITI 2015). This service interpolates rainfall and evaporation records from available stations to a selected point. The location selected for the SILO data drill resides at longitude 151.00 0, latitude -32.5 0 decimal and elevation 206 mahd. Climatic data was obtained for the period between 01/01/1889 to 19/04/2015. A summary of rainfall and evaporation data for Jerrys Plains Station and SILO are shown in Table 3-1. Table 3-1 Climate averages Source Statistic Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec TOTAL Jerrys Plains (BoM) Site SILO data Mean rainfall (mm) 77.1 73.1 59.7 44.0 40.7 48.1 43.4 36.1 41.7 51.9 61.9 67.5 645.3 Mean evaporation (mm) 220.1 168.0 155.0 120.0 89.9 60.0 71.3 80.6 111.0 164.3 195.0 204.6 1643.6 Evap minus rainfall 143.0 94.9 95.3 76.0 49.2 11.9 27.9 44.5 69.3 112.4 133.1 137.1 998.3 Mean rainfall (mm) 80.2 79.3 66.0 48.3 42.4 51.3 43.1 36.5 42.3 54.3 63.0 68.7 675.4 Mean evaporation (mm) 200.2 156.9 138.6 100.0 69.7 52.5 62.1 86.1 116.1 152.4 174.7 204.7 1514.0 Evap minus rainfall 120.0 77.6 72.5 51.8 27.3 1.2 19.0 49.6 73.8 98.0 111.7 136.0 838.6 SILO data is based on observational records provided by BoM, with data gaps addressed through data processing in order to provide a spatially and temporally complete climate dataset. Based on the SILO dataset, average annual rainfall is 675mm, with January being the wettest month (77mm). Annual evaporation (1,514mm/year) exceeds mean rainfall throughout the year, with the highest moisture deficit occurring during summer. Monthly records from the SILO dataset were used to calculate the Cumulative Rainfall Departure (CRD). The CRD shows graphically trends in recorded rainfall compared to long-term averages and provides a historical record of relatively wet and dry periods. A rising trend in slope in the CRD graph indicates periods of above average rainfall, whilst a declining slope indicates periods when rainfall is below average. A level slope indicates average rainfall conditions. Figure 3-1 shows the CRD and indicates that the district experienced a period of below average rainfall from 2006 until mid-2007. Between 2007 and 2012, the region recorded above average rainfall events, followed by typically average rainfall since 2012. United Wambo Project - Groundwater Impact Assessment (G1733) 22
2000 1000 1800 Rainfall (mm/year) 1600 1400 1200 1000 800 600 400 0-1000 -2000 Cumulative Rainfall Departure (mm) 200 0-3000 Site SILO rainfall (annual) Jerrys Plains Post Office rainfall data (annual) CRD (SILO) Figure 3-1 Cumulative Rainfall Departure (SILO) and monthly rainfall (Jerrys Plains and site SILO) SILO data also provides pan evaporation and calculated plant evapotranspiration (using the Penman-Monteith formulation) (see Figure 3-2). The bimodal plot indicates higher rainfall, evaporation and evapotranspiration during the summer months. During the mid-year winter months evaporation and evapotranspiration is lowest. United Wambo Project - Groundwater Impact Assessment (G1733) 23
250 Rainfall, evaporation, EVT (mm/month) 200 150 100 50 0 Month Monthly rainfall (mm) Evaporation (mm) Evapotranspiration FAO56 (mm) Figure 3-2 SILO average monthly rainfall, evaporation and evapotranspiration 3.3 Terrain At a regional scale, the terrain is characterised by a steep and incised range to the west, which falls generally towards the low lying floodplain of Wollombi Brook in the east (Figure 3-3). The main topographic highpoint is Mount Wambo within the Wollemi National Park, west of the Project Area. The Project Area is gently undulating, with elevation ranging between 60m Australian Height Datum (AHD) in the east and 215mAHD in the west. Outside of the Project Area, the topography grades into the flat alluvial lands associated with the adjacent water courses. The ground levels in the Wollombi Brook alluvial land are around 50mAHD to 60mAHD. West of the Project Area, within the Wollemi National Park, the elevation generally ranges between 300mAHD and 650mAHD. Due to historical farming and mining, the majority of the Project Area is cleared of vegetation. Wollemi National Park is densely vegetated with various plant communities, including open forests dominated by eucalypt species. United Wambo Project - Groundwater Impact Assessment (G1733) 24
3.4 Drainage Figure 3-3 shows the local surface water drainage setting. The Project Area is drained by Wollombi Brook and its minor tributary drainage features. Wollombi Brook flows in a north to northeasterly direction immediately east of Project Area, and joins with the Hunter River approximately 4km east of the Project Area. The minor drainage lines are ephemeral in nature, with flows dependent on rainfall events. North Wambo Creek traverses from the west to the south-east of the Project Area and flows into Wollombi Brook. Redbank Creek occurs within the Project Area, flowing in an easterly direction towards Wollombi Brook. Stony Creek traverses in a south-easterly direction and joins with the northeasterly flowing Wambo Creek over 3km south of the Project Area. Near the Project Area, the Wollombi Brook is classified as the Lower Wollombi Brook Water Source within the Hunter Unregulated WSP. The Hunter River is within the Hunter Regulated WSP. DPI Water monitor stream flow within Wollombi Brook and the Hunter River in real-time with the Hunter Integrated Telemetry System (HITS). The closest gauging station along Wollombi Brook is at Warkworth (station 210004), which is 2.4km east of the Project Area. On the Hunter River the closest station is 6.4km north of the Project Area at Liddell (210083). Stream flow records from the gauging stations were obtained and compared with monthly rainfall data to assess the contribution of baseflow to flows in Wollombi Brook and Hunter River. Figure 3-4 and Figure 3-5 show the estimated proportion of baseflow separated from the total recorded stream flow for Wollombi Brook and Hunter River respectively. The results show that surface water flow is largely a function of rainfall. However, it is estimated that groundwater contributes up to 70ML/day to the flows in Wollombi Brook, and up to 231ML/day to the Hunter River. The baseflow in the Hunter River is likely to be less than estimated due to releases from the Glenbawn Dam that maintains a permanent flow for downstream users. 1400 350 1200 300 Flow (ML/day) 1000 800 600 400 250 200 150 100 Rainfall (mm/month) 200 50 0 Jul-97 Jan-00 Jul-02 Jan-05 Jul-07 Jan-10 Jul-12 Jan-15 Date Rainfall Streamflow Baseflow 0 Figure 3-4 Baseflow in Wollombi Brook at Warkworth (210004) United Wambo Project - Groundwater Impact Assessment (G1733) 26
Flow (ML/day) 2000 1800 1600 1400 1200 1000 800 600 400 200 0 Jul-97 Jan-00 Jul-02 Jan-05 Jul-07 Jan-10 Jul-12 Jan-15 Date Rainfall Streamflow Baseflow 350 300 250 200 150 100 50 0 Rainfall (mm/month) Figure 3-5 Baseflow in Hunter River at Liddell (210083) While there are contributions of alluvial groundwater to the major rivers, losing conditions can also occur in different areas and at different times, due to both natural and anthropogenic processes. Figure 3-6 shows estimated areas of losing and gaining conditions within the major rivers, as well as within the alluvium. Figure 3-6 is based on interpolated water levels within the alluvium, as well as regional topographic surface. As a result the losing and gaining segments are considered indicative only. The figure shows that both the Hunter River and Wollombi Brook are predominantly gaining water from the surrounding alluvium. However, there are also areas where the river recharges the underlying alluvium (losing), particularly around areas of active mining. As with the river zones, Figure 3-6 also shows that the alluvium is largely gaining groundwater from the underlying Permian coal measures, particularly within the Hunter River alluvium downstream of Foy Brook. Losing conditions (flow from alluvium to Permian) are also visible, particularly where active mining is present. United Wambo Project - Groundwater Impact Assessment (G1733) 27
3.5 Land use Land use within the Project Area is primarily coal mining. Surrounding the Project Area land use includes coal mining operations and agriculture. Agricultural and environmental land use includes: cattle grazing in open pastures; dairy farming and horse studs; improved pasture and cropping along the Wollombi Brook and Hunter River alluvial flood plains; and vegetation, including riverine vegetation along drainage lines (i.e. Wollombi Brook) and remnant vegetation within the Wollemi National Park. A small number of olive groves and vineyards are located south and north-west of the Project Area, as shown on Figure 3-3. Areas zoned as CICs are present within the wider area, with an equine CIC 6km to the north-west and a viticulture CIC 5km to the south-east. No coal seam gas (CSG) extraction projects are currently operating or proposed in the vicinity of the Project Area. The Project Area occurs within the Hunter Valley coalfields, which has a long history of mining the Wittingham Coal Measures, dating back to the 1950 s. Table 3-2 summarises the nearby, currently approved mines that intersect the Wittingham Coal Measures, including their approved timeframes and target coal seams. Figure 3-7 shows the locations of the approved mines. Table 3-2 Summary of approved mines in Wittingham Coal Measures Mine Type Timeframe Seams mined Bulga Cumnock Colliery Open cut 1990-2035 Whybrow to Broonie Underground 2003 2035 Whybrow to Woodlands Hill Open cut 1992 2011 Arties and Liddell Underground 1949 2003 Arties to Barrett HVO North Open cut 1979-2021 Mt Arthur to Barrett HVO South Open cut 1997 2028 Bowfield to Bayswater Mt Thorley Warkworth Open cut 1980-2035 Woodlands Hill to Bayswater North Lemington Ravensworth Narama United Wambo Open cut 1971-1999 Warkworth to Vaux Underground 1971-1992 Mt Arthur Seam Open cut 1972-2039 Vaux to Barrett Underground 2007-2024 Pikes Gully to Liddell Open cut 1898-1992 Wambo to Whynot Underground 1992-2010 Arrowfield Open cut 1974-2017 Whybrow to Whynot Underground 1969 2032 Whybrow to Bowfield The potential for cumulative groundwater impacts associated with the surrounding land uses is discussed in Section 7. United Wambo Project - Groundwater Impact Assessment (G1733) 29
4 Geological setting The geological setting has been informed by the following data sources: publicly available geological maps (Hunter Coalfields map sheets) and reports; geological, geotechnical and hydrogeological reports prepared for United and Wambo, some dating back to the 1970 s; publicly available geological and hydrogeological reports for surrounding mine operations; hydrogeological data held on the DPI Water groundwater database (Pinneena) and the National Groundwater Information System (NGIS) for existing private groundwater bores; a 3D geology model developed by the proponent for United; a 3D groundwater model developed by HydroSimulations on behalf of Peabody for Wambo Mine; and lithological logs for coal mining exploration holes. This information provided the structural framework for developing a 3D numerical groundwater model by AGE. Appendix B describes the approach to the groundwater modelling in detail. 4.1 Regional geology The main feature of the regional geology is the Sydney Basin. The basin formed in the Late Carboniferous Early Permian due to igneous rifting and crustal thinning, which resulted in the deposition of Permian and Triassic aged sedimentary sequences. Within the Project Area, Permian sediments form the Wittingham Coal Measures of the Hunter Coalfields. The coal measures plunge in a general west to south-westerly direction, with the Wittingham Coal Measures occurring at outcrop to the east of the Project Area, near the Hunter River. Within the Project Area, the Wittingham Coal Measures comprise economic coal seams, along with overburden and interburden consisting of sandstone, siltstone, tuffaceous mudstone and conglomerate. The Permian sediments are unconformably overlain by thin Quaternary alluvial deposits. These deposits consist of silt, sand and gravel in the alluvial floodplain of the Wollombi Brook. To the east of the Wollombi Brook is a sequence of aeolian sands, known as the Warkworth Sands Formation, that form a thin capping on the underlying Permian bedrock. The Permian coal measures are also unconformably overlain by the Triassic Narrabeen Group, which formed from uplift during the Triassic. The Narrabeen Group comprises fluviatile deposits that form the ridges and a high plateau within the Wollemi National Park, west of the Project Area. Surficial weathering occurs across the Project Area. The weathering profile is typically present as a thin heterogeneous layer of unconsolidated and highly weathered material (regolith) overlying fresh bedrock. Figure 4-1 shows the regional surface geology across the site and surrounds, based on the 1:100,000 scale regional coalfields geological map, published by Department of Mineral Resources (Glen & Beckett, 1993). The Quaternary alluvium in Figure 4-1 has been digitised based on the 1:25,000 Geology Map of Singleton (McIlveen, 1984), Muswellbrook (Summerhayes, 1983), Jerrys Plains (Sniffin & Summerhayes, 1987) and Doyles Creek (Sniffin et al., 1988), which are not available in digital format. Table 4-1 provides a detailed summary of the regional geology and relevant stratigraphic units within the Project Area and surrounds. Figure 4-2 provides a conceptual geological cross section showing the relative distribution of key stratigraphic units across the Project Area. Figure 4-3 shows a map of the local geology at the Project Area, which is informed by previous field studies. United Wambo Project - Groundwater Impact Assessment (G1733) 31
Table 4-1 Summary of regional geology Age Stratigraphic Unit Description Quaternary Quaternary sediments alluvium (Qa) Surficial alluvium (Qhb) Productive basal sands/gravel (Qha) Shallow sequences of clay, silty sand and sand. Basal sands and gravels overlying surficial alluvium along major watercourses (i.e. Hunter River and Wollombi Brook). Aeolian dunes (Czb) Sand Tertiary Silicified weathering profile (Czas) Silcrete Alluvial terraces (Cza) Silt, sand and gravel Jurassic Volcanics (Jv) Flows, sills and dykes Triassic Narrabeen Group (Rn) Sandstone, interbedded sandstone and siltstone, claystone. Localised at Wollemi National Park. Late Newcastle Coal Measures (Psl) Glen Gallic Sub-group Doyles Creek Sub-group Horseshoe Creek Sub-group Apple Tree Flat Sub-group Coal seams, claystone (tuffaceous), siltstone, sandstone and conglomerate. Watts Sandstone Medium to coarse-grained sandstone. Permian Wittingham Coal Measures Jerrys Plains Sub-group (Pswj) Cyclic coal seam sequence with dark-grey to black laminated shale and siltstone. Coal seams include Whybrow Seam, Redbank Creek Seam, Wambo Seam, Whynot Seam, Blakefield Seam, Glen Munro Seam, Woodlands Hill Seam, Arrowfield Seam, Bowfield Seam, Warkworth Seam, Mt Arthur Seam, Piercefield Seam, Vaux Seam, Broonie Seam and Bayswater Seam. Archerfield Sandstone Bronze-coloured lithic sandstone Vane Sub-group (Pswv) Coal bearing sequences with wedges of sandstone and siltstone. Coal seams include Lemington Seam, Pikes Gully Seam, Arties Seam, Liddell Seam, Barrett Seam and Hebden Seam. Saltwater Creek Formation (Pswc) Sandstone and siltstone, minor coaly bands, siltstone towards base. Middle Mulbring Siltstone (Pmmd/Pmmg/Pmm) Siltstone, claystone and minor fine grained sandstone. Note - indicates an unconformable contact United Wambo Project - Groundwater Impact Assessment (G1733) 32
300 A South-West A North-East 200 North Wambo Creek (diversion) Wambo Open Cut HVO South 100 Narrabeen Group UG139 GW117 UG138 0 Newcastle Coal Measures -100-200 Whynot Seam m -300-400 -500-600 Woodlands Hill Seam m Arrowfield & BowfieldSeam m Warkworth Seam m Mt ArthurSeam m Vaux Seam m Bayswater Seam m Jerrys Plains Subgroup Coal Measures Vane Subgroup Coal Measures (mahd) Regolith Clay Basal sand and gravel Narrabeen Group Newcastle Coal Measures Jerrys Plains Subgroup Coal Measures Vane Subgroup Coal Measures Conceptualised geological cross section through Project Area Figure 4-2 United Wambo Project - Groundwater Impact Assessment (G1733)
4.2 Local geology The following main stratigraphic units occur within the Project Area and surrounds (from youngest to oldest): Quaternary sediments; Triassic Narrabeen Group; Permian Newcastle Coal Measures; and Permian Wittingham Coal Measures. Each of the main stratigraphic units is discussed in further detail below. Figure 4-3 shows the surface geology of the Project Area and immediate surrounds. Figure 4-4 to Figure 4-5 present structure contours and thickness contours (isopachs) for each key unit. Jurassic volcanics do not occur within the immediate vicinity of the Project Area. However, these formations have been described below for completeness. 4.2.1 Quaternary to Tertiary aged sediments Site information and geological mapping indicates the localised presence of Quaternary sediments along North Wambo Creek near the Project Area (Figure 4-3). The characteristics of the sediments in the vicinity of the Project Area are well understood from previous investigations and exploration drilling. These sediments are 4m to 7m thick and comprise clays, sandy silts and localised occurrences of medium grained sand. With approved historic mining, North Wambo Creek was re-aligned and the alluvium associated with North Wambo Creek removed where it occurred within the approved disturbance area, as shown in Figure 4-3. Published geological maps and site geophysical surveys show the presence of Quaternary alluvium along Wollombi Brook and the Hunter River flood plains. The Quaternary alluvium commonly comprises two distinct depositional units, the surficial alluvium and productive basal alluvium. The surficial alluvium comprises shallow sequences of clay, silty sand and sands. Along the minor drainage lines the surficial alluvium is typically constrained within 400m of the creeks and is between 7m to 19m thick. Within the Wollombi Brook and Hunter River flood plains the surficial alluvium is commonly underlain by basal sands and gravels that can form a productive groundwater aquifer. The basal sands and gravels do not occur at the Project Area, but are present approximately 370m south-east. The basal sands and gravels make up the AIP highly productive groundwater source, as described in Section 2.4.1. Along the Wollombi Brook flood plain the productive basal sands are typically between 7m and 20m thick. Cainozoic aged silicified weathering profiles (Cza) and alluvial terraces (Czas) also occur outside the Project Area. The Tertiary deposits comprise silcrete, silts and gravels, and are considered comparable with the unconsolidated weathered bedrock (regolith). The structure, distribution and thickness of the Quaternary alluvium and the regolith are shown on Figure 4-4. The thickness of the regolith is based on the Soil and Landscape Grid of Australia released by CSIRO. United Wambo Project - Groundwater Impact Assessment (G1733) 36
4.2.2 Tertiary volcanics Minor Tertiary-age intrusions have been observed at outcrops north-west of the Project Area, and dykes and sills have been encountered at the various mining operations. 4.2.3 Triassic Narrabeen Group The Narrabeen Group comprises quartz-lithic to quartzose sandstone, conglomerate, mudstone and siltstone with rare coal. The unit unconformably overlies the Newcastle Coal Measures and Wittingham Coal Measures to the west of the Project Area. The contact between the Triassic and the underlying Permian is marked by an erosional unconformity. The sequence does not occur at the Project Area, but is present over 500m west. The structure and distribution of the Narrabeen Group was based on existing geological mapping and knowledge and experience in the region. 4.2.4 Permian Newcastle Coal Measures The Permian aged Newcastle Coal Measures (formerly Wollombi Coal Measures) are present south-west of the Project Area. The coal measures unconformably underlie the Triassic Narrabeen Group. At the Project Area the coal measures are generally less than 15m thick and are deeply weathered. The coal measures generally dip less than five degrees to the south-west. The Newcastle Coal Measures comprise tuffaceous claystone, tuff, siltstone, sandstone, conglomerate and minor coal. Coal within the Newcastle Coal Measures generally contains stone and is not considered of economic quality within the region. 4.2.5 Permian Watts Sandstone The Watts Sandstone overlies the Wittingham Coal Measures and comprises medium to coarse grained sandstone sequences, equivalent to the Waratah Sandstone. The unit was deposited during a marine transgression and is heterogeneously distributed. The Watts Sandstone is present to the west of the Project Area, where it occurs as a relatively thin (<15m thickness), deeply weathered unit underlying the Newcastle Coal Measures. 4.2.6 Permian Wittingham Coal Measures The Permian aged Wittingham Coal Measures unconformably underlie the Triassic Narrabeen Group sediments to the west of the Project Area, and the Quaternary to Tertiary sediments to the east of the Project Area. The coal measures outcrop east of the Project Area, towards the Hunter River. The Wittingham Coal Measures comprise coal seams interbedded with siltstone, sandstone and shales. The non-coal portions of the sequence being predominantly sandstones, siltstones, conglomerates and shales are referred to as interburden in the mining context. The Wittingham Coal Measures are up to 450m thick at the Project Area, but regionally range from approximately 250m to 600m thickness. The structure, distribution and thickness of the Wittingham Coal Measures are shown on Figure 4-5. United Wambo Project - Groundwater Impact Assessment (G1733) 38
Within the Wittingham Coal Measures there are 15 main coal seams that are mined across the Hunter Valley. In stratigraphic order (youngest to oldest) and using Wambo nomenclature, they are the Whybrow, Redbank Creek, Wambo, Whynot, Blakefield, Glen Munro, Woodlands Hill, Arrowfield, Bowfield, Warkworth, Mt Arthur, Piercefield, Vaux, Broonie and Bayswater seams. It should be noted that seam nomenclature varies slightly between Wambo, United and HVO. For the purpose of the Project the Wambo nomenclature has been used. The difference in nomenclature between Wambo, HVO and United is summarised below: Wambo s Glen Munro Seam is equivalent to HVO s Woodlands Hill Seam and United s Blakefield Seam; Wambo s Woodlands Hill Seam is equivalent to HVO s Arrowfield Seam and United s Glen Munro Seam; Wambo s Arrowfield Seam is equivalent to HVO s Bowfield Seam and United s Woodlands Hill Seam; and Wambo s Bowfield Seam is a localised split absent at HVO. All other seams have equivalent nomenclature. Each coal seam occurs with various splits and plies, with an average coal thickness of 3m, and a total coal thickness of up to 5.5m for most seams. The coal seams are interbedded with units of siltstone, sandstone and shale. The interburden has an average thickness of 25m, and a maximum thickness of up to 90m. The Permian coal measures occur at outcrop or are unconformably overlain by Quaternary sediments. As a result, the upper Permian stratigraphy underwent a period of weathering. At the Project Area, the weathered profile of the Permian bedrock extends to around 50m below surface. 4.3 Geological structure The Permian coal measures are stratified (layered) sequences that have undergone deformation resulting in strata dipping in a general south-westerly direction at the Project Area. Regionally, the coal measures are influenced by large fold structures, including the Muswellbrook Anticline and the Bayswater Syncline, which occur east of the Project Area and trend in a north to north-west direction. Intrusions (dykes) and minor thrust faulting occurred within the Permian stratigraphy across the Projects area. North-east to south-west trending faults have been mapped within the proposed United Open Cut, which indicate up to 5m displacement of the Permian strata (Figure 4-3). Regionally there are several north-east to south-west trending fault structures. This includes the Hunter Valley Cross Fault and Redmanvale Fault that are north and west to south-west of the Project Area, respectively (Figure 4-1). Little is documented about the Hunter Valley Cross Fault; however drill logs indicate a maximum displacement of approximately 10m. United Wambo Project - Groundwater Impact Assessment (G1733) 39
5 Hydrogeology 5.1 Existing data and monitoring United Collieries and Wambo Coal have a combined groundwater monitoring network that has evolved since 2000. The network comprises 77 bores and 24 vibrating wire piezometers (VWPs), of which 27 bores and 11 VWPs (55 sensors) are currently monitored as part of the groundwater monitoring program (GWMP) for Wambo Coal and the Environmental Monitoring Program (EMP) for United Collieries. Further details about the monitoring network are included in Appendix A. Numerous studies have been conducted at the Project Area and surrounds due to the long history of mining within the region. Historic data includes field hydraulic testing of key lithological units (i.e. packer testing, core tests and slug tests), groundwater levels and water quality. The consolidated results are presented in Section 5.2 to Section 5.4. Additional fieldwork was also completed as part of the Project in order to address data gaps. The fieldwork included collecting water quality samples from some site bores and testing for a full suite of water quality analytes in order to assess the current beneficial use of groundwater. Results from the sampling event are presented in Appendix A and discussed in Section 5.4. A bore census was also conducted within 4km of the proposed extraction area in October 2015. The findings from the bore census are detailed in Appendix A and discussed in Section 5.5. 5.2 Hydraulic parameters Extensive hydraulic testing has historically been undertaken across Hunter Valley using a variety of methods, including packer testing, lab core permeability testing and slug tests. Mackie (2009) compiled much of this data in a single report, which was used for the Project. This was supplemented with data collected within the Project Area and surrounds. The majority of the alluvial data was collected from the Hunter River palaeochannel and highly productive zone (basal sands and gravels) of the Hunter River alluvium, with a total of 59 measurements recorded. Individual coal seams and interburden (siltstone and sandstone) within the Jerrys Plains Sub-group and Vane Sub-group were also tested. In total, there are 303 measurements available for the coal, and 151 measurements for the interburden material. Figure 5-1 shows the distribution in all available horizontal hydraulic conductivity measurements for the alluvium, interburden and coal, based on data collected at the Project Area and surrounds. United Wambo Project - Groundwater Impact Assessment (G1733) 41
120 100 Alluvium Interburden Coal 80 Frequency 60 40 20 0 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 Horizontal hydraulic conductivity (m/day) Figure 5-1 Histogram of horizontal hydraulic conductivity (Kh) distribution The results show that the alluvium has a relatively high hydraulic conductivity, which ranges between 5.3x10-2 m/day and 3.70x10 2 m/day. The coal seams are also relatively permeable, with hydraulic conductivity values generally around 1x10-2 m/day, and a wide range between 5.24x10-7 m/day and 12m/day. The hydraulic conductivity of the interburden and overburden material is also highly variable, ranging between 1.87x10-7 m/day and 1m/day, but typically lower than coal and alluvium. The hydraulic conductivity of the coal seams reduces with depth due to the closure of the cleats with increasing stratigraphic pressure, and possible infilling due from mineral precipitates. Figure 5-2 shows the relationship between hydraulic conductivity and depth relationships for the coal seams. The relationship for interburden is presented in Figure 5-3. United Wambo Project - Groundwater Impact Assessment (G1733) 42
1.E+01 Coal 1.E+00 Trend 1.E-01 1.E-02 Kh (m/day) 1.E-03 1.E-04 1.E-05 y = 0.2e -0.02x 1.E-06 1.E-07 0 100 200 300 400 500 600 700 Depth (m bgl) Figure 5-2 Hydraulic conductivity vs. depth coal 1.E+01 Interburden 1.E+00 Trend 1.E-01 1.E-02 Kh (m/day) 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 y =92.87x -3.07 0 100 200 300 400 500 600 Depth (m bgl) Figure 5-3 Hydraulic conductivity vs. depth interburden United Wambo Project - Groundwater Impact Assessment (G1733) 43
5.3 Groundwater recharge, distribution and flow Groundwater levels measured in bores allow vertical and lateral hydraulic gradients to be calculated and, also can be used to assess relative hydraulic conductivity. Potentiometric surfaces for the key formations were prepared using: groundwater levels recorded in 2015 for site monitoring bores (Appendix A); publicly available water levels recorded by surrounding mines; and recent available groundwater data for private bores and government monitoring bores, as documented within Pinneena (DPI Water). Figure 5-4 shows hydrographs from monitoring points along Wollombi Brook, and Figure 5-5 shows the interpolated groundwater contours and saturated thickness of the Quaternary alluvium, representing current (2015) conditions. Figure 5-6 shows the interpolated groundwater contours (current conditions) for the Vaux Seam of the Wittingham Coal Measures. Historical groundwater levels for all available bores are presented in Appendix A. Figure 5-4 compares groundwater level trends within the alluvium along Wollombi Brook east of the United and Wambo operations. Monitoring of the alluvial groundwater is presented for bore P12 and VWP sensor P33_13m, with water levels within the underlying Permian coal measures recorded by VWP sensor P33_46.5m (Woodlands Hill Seam) and P33_113m (Arrowfield Seam). The figure also shows the surface water level recorded at the DPI Water Warkworth gauging station in Wollombi Brook (station 210004) and rainfall trends (CRD). This allows the groundwater and surface water trends to be compared, and interactivity considered. Further hydrographs for all site bores are included in Appendix B under the model calibration results. 60 1000 Water elevation (mahd) 50 40 30 20 10 500 0-500 -1000-1500 Cumulative Rainfall Departure (mm) 0-2000 Jan-07 Jan-08 Dec-08 Dec-09 Jan-11 Jan-12 Dec-12 Dec-13 Jan-15 Wollombi Brook (210004) P12 P33_13m P33_46.5m P33_113m CRD Figure 5-4 Hydrographs comparing groundwater trends and Wollombi Brook levels United Wambo Project - Groundwater Impact Assessment (G1733) 44
Figure 5-4 shows a correlation between stream water levels and groundwater levels within the alluvial aquifer, indicating the aquifer obtains focussed recharge from stream flow recharge to the Quaternary as well as diffuse recharge from rainfall as well. As shown in Figure 5-4, the groundwater levels within the alluvium associated with Wollombi Brook around active mine areas (bore P12) are generally below stream levels, as recorded at Warkworth (station 210004). However, alluvial water levels are higher than stream levels on the eastern bank of Wollombi Brook (P33_13m), further away from active mining. This suggests reduced baseflow contributions from the alluvium near mining areas. Figure 5-4 also shows that where mining is present the actively mined coal seams are depressurised, recording groundwater levels around 25m to 45m lower than recorded within the alluvium. Therefore, where drawdown due to mining is present, there is limited potential for upward seepage of Permian groundwater to the overlying alluvium. Figure 5-5 shows that groundwater flow within the Quaternary alluvium reflects the topography and stream gradient. The Hunter River alluvium flows in an easterly direction, while groundwater within the Wollombi Brook alluvium flows in a north to north-easterly direction towards the Hunter River. As discussed above, recharge to the Quaternary alluvium occurs via diffuse and focussed recharge; however, away from active mining the alluvium is also recharged by upward flow from the underlying Permian coal measures. As discussed in Section 3.4, the alluvium is largely gaining groundwater from the underlying Permian coal measures, particularly within the Hunter River alluvium downstream of Foy Brook. Losing conditions (flow from alluvium to Permian) are also visible, particularly where active mining is present. The available data for the alluvium indicates that it is largely unsaturated within the more elevated tributaries, with the alluvial groundwater largely restricted to the thicker sequences of sand and gravel (highly productive alluvium) along the Hunter River and Wollombi Brook. The alluvium is an unconfined unit, the upper sequences of the alluvium (approximately upper 8m) are largely clay rich and less permeable than the basal sands and gravels. The Wittingham Coal Measures occur at outcrop over 9km north and east of the Project Area, and also occur beneath weathered regolith and Quaternary alluvium. The Wittingham Coal Measures are saturated across its extent due to the depth of the unit. Figure 5-6 shows groundwater level contours and flow directions for the Vaux Seam, which occurs at outcrop approximately 3km north and east of the Project Area. Groundwater flow largely follows the regional topography, flowing in a north-easterly direction. Groundwater levels within the Wittingham Coal Measures are generally 30m below surface, ranging between 80mAHD to the south-west, beneath the escarpment of the Wollemi National Park, down to 50mAHD where the unit occurs at subcrop to the north-east along the Hunter River. The groundwater levels also show localised drawdown within active mining areas. The groundwater contours for the coal seam indicates recharge by downward leakage from the Narrabeen Group present at Wollemi National Park, as well as from recharge where the unit occurs at outcrop to the north of the Project Area. It is likely that localised downward leakage (losing conditions) occurs from the Quaternary alluvium, particularly where the more permeable coal seams subcrop beneath the alluvium and where active mining is present. Groundwater discharge from the Wittingham Coal Measures currently occurs as discharge to active mining and abstraction bores, as well as upward seepage to the Quaternary alluvium in localised areas. United Wambo Project - Groundwater Impact Assessment (G1733) 45
5.4 Groundwater quality This section reports on the characteristics and beneficial use of groundwater within the various geological units across the Project Area and surrounds. The main units include the Quaternary alluvium ( highly productive and less productive alluvium), Permian interburden (conglomerate/siltstone/sandstone/shale) and coal. Water quality results for surface water (Wollombi Brook) and spoil are also discussed below. Appendix A presents the groundwater quality data collected at site since 2003 and during the 2015 field investigation, as well as available data collected by neighbouring mine operations since 2000. 5.4.1 Groundwater characteristics Major ion chemistry has been presented based on averaged water quality results for each of the major groundwater units, which is discussed further in Appendix A. Figure 5-7 shows the Mg/Na and Na/SO 4 scatter plots for the averaged water quality results of the main groundwater units (alluvium, interburden, coal and spoil) as well as the Hunter River and Wollombi Brook surface water. 1000 10000 Hunter River Hunter River Wollombi Brook Wollombi Brook Mg (mg/l) 100 SO 4 (mg/l) 1000 100 Highly productive alluvium Less productive alluvium Interburden Coal Highly productive alluvium Less productive alluvium Interburden Coal Spoil Spoil 10 10 100 1000 10000 Na (mg/l) 10 10 100 1000 10000 Na (mg/l) Figure 5-7 Mg/Na scatterplot and Na/SO4 scatterplot of groundwater quality Figure 5-7 shows that the surface waters have the lowest concentrations of major ions (Na, Mg and SO 4) on average, closely followed by the highly productive alluvium. Groundwater within the interburden and spoil show the highest average concentrations of major ions (Na, Mg and SO 4). There is generally a linear relationship, with the proportions of the various ions remaining constant as the concentrations increase. The exception is the Na:SO 4 ratio that indicates the proportion of sulfate may be reduced in coal. This is likely due to bacterial reduction of sulfate to H 2S, a process commonly noted in coal seams. United Wambo Project - Groundwater Impact Assessment (G1733) 48
5.4.2 Beneficial use of groundwater Groundwater quality data provides useful information on the beneficial use of the groundwater associated with the major stratigraphic units. Salinity is a key constraint to water management and groundwater use, and can be described by total dissolved solid (TDS) concentrations. TDS concentrations are commonly classified on a scale ranging from fresh to extremely saline. FAO (2013) provide a useful set of categories for assessing salinity based on TDS concentrations as follows: Fresh water <500 mg/l Brackish (slightly saline) 500 to 1,500 mg/l Moderately saline 1,500 to 7,000 mg/l Saline 7,000 to 15,000 mg/l Highly saline 15,000 to 35,000 mg/l Brine >35,000 mg/l Figure 5-8 presents the TDS data for the various surface waters surrounding the Project Area that are monitored by United Collieries and Wambo Coal sorted into the above TDS categories. Redbank Creek North Wambo Creek Wollombi Brook (2004-2014) Wollombi Brook (NOW 1992-2015) 250 Fresh Brackish Moderately saline Saline Highly saline Brine 200 Number of samples 150 100 50 0 0-500 500-1500 1500-7000 7000-15000 14000-35000 >35000 Total dissolved solids (mg/l) Figure 5-8 Surface water TDS histogram The distribution of TDS values in Figure 5-8 shows that the water quality within minor tributaries of North Wambo Creek and Redbank Creek is typically brackish to moderately saline, respectively. The quality of surface water within the Wollombi Brook is largely fresh, and ranges between fresh to moderately saline. United Wambo Project - Groundwater Impact Assessment (G1733) 49
Figure 5-9 presents the concentration of TDS within Wollombi Brook as recorded by United Collieries and Wambo Coal since 2004, and the average monthly results recorded at the DPI Water stream gauge along Wollombi Brook at Warkworth (station 210004). The figure also shows the 5 th and 95 th percentile of the average monthly TDS results for Wollombi Brook at Warkworth (Station 210004), which are 108mg/L and 1,817mg/L, respectively. 4000 3500 Total dissolved solids (mg/l) 3000 2500 2000 1500 1000 500 0 Wollombi Brook (Wambo) Wollombi Brook (210004) DPI Water 95th percentile DPI Water 5th percentile Figure 5-9 Wollombi Brook TDS over time Figure 5-9 shows a relatively good fit between the results collected by DPI Water and Wambo. The historic data from DPI Water shows the salinity of Wollombi Brook peaked between 2003 and 2007, during the millennium drought. Since 2007, water quality has generally been fresher than levels recorded prior to 2003. This likely relates to increased rainfall and a possible reduction in flow of saline water from the Permian stratigraphy due to mining. Figure 5-10 presents all available groundwater TDS data (both laboratory TDS and calculated TDS from available EC data using 1:0.57 ratio for EC to TDS) as a histogram, again sorted into the FAO salinity categories. The alluvial data has been separated into highly productive alluvium or less productive alluvium. Appendix A contains further water quality results. United Wambo Project - Groundwater Impact Assessment (G1733) 50
Highly productive alluvium Less productive alluvium Interburden Coal Spoil 1400 Brackish Fresh Moderately saline Saline Highly saline Brine 1200 Number of samples 1000 800 600 400 200 0 0-500 500-1500 1500-7000 7000-15000 14000-35000 >35000 Total dissolved solids (mg/l) Figure 5-10 Groundwater TDS histogram The results show that groundwater within highly productive alluvium generally has fresh water quality. Figure 5-10 shows that the results range from fresh to moderately saline, with a 5 th and 95 th percentile for TDS (laboratory and calculated from EC) of 131mg/L and 1,499mg/L. The less productive alluvium generally has brackish water quality, with results ranging from fresh to saline. Based on the available data, the 5 th and 95 th percentile for TDS (laboratory and calculated from EC) is 363mg/L and 6,702mg/L, respectively. The higher salinity less productive alluvium likely relates to reduced recharge. The water quality results for the Permian stratigraphy indicates that groundwater within the coal is generally moderately saline, with results ranging from fresh to saline. The interburden units are also generally moderately saline, with results ranging from fresh to highly saline. Similar to the Permian units, the spoil water quality is generally moderately saline and ranges between brackish and saline water quality. For the purposes of this assessment, groundwater quality data has been compared to guideline values from the ANZECC (2000) guidelines for long-term irrigation, livestock watering (beef cattle) and the Australian Drinking Water Guidelines (ADWG) (NHMRC 2011) drinking water guidelines. All available water quality results are presented in Appendix A. The results for the alluvium ( highly productive and less productive ) indicate that the groundwater is not suitable for long-term irrigation according to the ANZECC (2000) guideline levels for total manganese. The results indicate that groundwater within the highly productive alluvium is suitable for stock water supply. The averaged laboratory TDS results (Appendix A) show that salinity is below 1,020mg/L in the highly productive alluvium, and as detailed above, the 95 th percentile for TDS (laboratory and calculated from EC) is 1,499mg/L. These results are below the ANZECC (2000) adverse levels for stock (i.e. sheep, beef cattle, dairy cattle, horses, pigs and poultry). United Wambo Project - Groundwater Impact Assessment (G1733) 51
The averaged laboratory TDS results for the less productive alluvium (Appendix A) show that salinity is generally below 4,610mg/L. However, as detailed above, the 95 th percentile for TDS (laboratory and calculated from EC) is 6,702mg/L. The results show that the less productive alluvium has a higher salinity compared to the highly productive alluvium. In addition, TDS concentrations are recorded above the ANZECC (2000) guideline level for adverse impacts on pigs and poultry (3,000mg/L), dairy cattle (4,000mg/L), beef cattle (5,000mg/L) and horses (6,000mg/L). However, the TDS is below the ANZECC (2000) guideline level for adverse impacts on sheep. Overall, the results indicate that groundwater within the less productive alluvium is not suitable for stock water supply (excluding sheep) in accordance with the ANZECC (2000) guidelines. However, alluvial groundwater is occasionally used for stock (cattle) water supply and some domestic applications (i.e. gardens) within the region. This water use is identified in the bore census presented in Appendix A and is further discussed in Section 5.5. The results for the Permian stratigraphy (coal and interburden) indicate that the groundwater is not suitable for stock water supply due to elevated salinity levels and total aluminium concentrations. Groundwater within the Permian stratigraphy also records total manganese concentrations above the ANZECC (2000) long term irrigation trigger. Total selenium concentrations above the ANZECC (2000) guideline level for short-term irrigation are recorded for the coal. The results for spoil show average sulphate concentrations greater than 1,000mg/L, which is above the ANZECC (2000) trigger for stock water supply (pigs). The results also indicate that groundwater within the Permian coal measures and spoil is not suitable for stock water supply or irrigation according to the ANZECC (2000) guidelines, as presented in Appendix A. 5.5 Groundwater use 5.5.1 Private water users A search of the National Groundwater Information System (NGIS) database 2 identified 66 registered bores within 4km of the proposed extraction area. Figure 5-11 shows the location of the registered bores relative to the proposed extraction area and two un-registered water supply bores identified during a bore census. Details on the bores are presented in Appendix A. Of the 68 bores, 23 have been abandoned and destroyed, and nine have been abandoned but are in a usable condition. Of the remaining 36 existing bores, 18 are located on land owned by the proponents and two are used for groundwater monitoring on Coal & Allied land (GW30740 and GW080963), as shown in Figure 5-11. The remaining 16 are private bores largely used for stock water supply, with some also used for irrigation and domestic use (garden and toilets). Table 5-1 summarises the number of private bores categorised by the screened geology and bore status (existing and abandoned but usable). For bores with no available lithological details, the surface geology map and lithological logs for nearby exploration and registered bores were used to estimate the screened lithology. 2 http://www.bom.gov.au/water/groundwater/ngis/ United Wambo Project - Groundwater Impact Assessment (G1733) 52
Table 5-1 Existing and usable private bores by stratigraphic unit within 4km of Project Screened unit Existing private bores Abandoned but usable private bores Total existing and usable bores within 4km Quaternary alluvium 8 8 16 Triassic Narrabeen Group (sandstone) 5 0 5 Newcastle Coal Measures - coal 2 0 2 Wittingham Coal Measures shallow weathered unit 1 1 2 Total 16 9 25 Note: monitoring bores, bores on land owned by the proponent and abandoned and destroyed bores have been excluded The majority of private bores are screened within the Quaternary alluvium. The NGIS database and the bore census (Appendix A) indicate that the main use of groundwater is for stock, with minor irrigation and domestic use (gardens and toilets). As shown in Table 5-1, five bores intersect the Triassic aged Narrabeen Group sandstones. These five bores are located west of the proposed extraction area, with four located at the foothills of the Wollemi National Park. GW064382 is apparently located at the top of the escarpment within the Wollemi National Park. Whilst this could not be verified, it is unlikely that the bore is currently in use. Two existing privately owned bores (GW018045 and GW018046) are potentially within shallow sequences (less than 30m depth) of the Newcastle Coal Measures. One bore in the township of Warkworth (GW060750) potentially intersects the shallow weathered sequences of the Wittingham Coal Measures. United Wambo Project - Groundwater Impact Assessment (G1733) 53
5.5.2 Groundwater dependent ecosystems The EIS Ecology study identified the following vegetation types occurring in proximity to the Project Area as having the potential to be at least partially groundwater-dependent: Central Hunter Swamp Oak Forest; Hunter Floodplain Red Gum Woodland Complex; Hunter Valley River Oak Forest; River Flat Eucalypt Forest; and Stands of individual river red gum trees (Eucalyptus camaldulensis). Each of these is described in greater detail below. The distribution of this vegetation is shown on Figure 5-12. Central Hunter Swamp Oak Forest This vegetation is considered likely to be potentially dependent on groundwater reserves in certain circumstances such as times of drought. Similar vegetation exists further upstream and in other creek systems where there is unlikely to be any significant alluvial groundwater present. It is dominated by a mid-dense canopy layer of swamp oak (Casuarina glauca), a sparse mid-storey, and a dense layer of leaf litter from swamp oak. This vegetation is not consistent with any community listed under the NSW Threatened Species Conservation Act 1995 (TSC Act) or EPBC Act. Hunter Floodplain Red Gum Woodland Complex The Hunter Floodplain Red Gum Woodland Complex in this area is dominated by forest red gum (Eucalyptus tereticornis) and rough-barked apple (Angophora floribunda). This vegetation is consistent with the Hunter Floodplain Red Gum Woodland in the NSW North Coast and Sydney Basin Bioregion Endangered Ecological Community listed under the TSC Act; however, it is not consistent with any community listed under the EPBC Act. Hunter Valley River Oak Forest The Hunter Valley River Oak Forest comprises a dense canopy layer of river oak (Casuarina cunninghamiana) and occasional emergents of river red gum (Eucalyptus camaldulensis) and rough-barked apple (Angophora floribunda). Groundcover is typically sparse. In this area, Hunter Valley River Oak Forest primarily occurs along Wollombi Brook. This vegetation is not consistent with any communities listed under the TSC Act and EPBC Act. River Flat Eucalypt Forest This vegetation is dominated by a canopy of forest red gum (Eucalyptus tereticornis) and rough-barked apple (Angophora floribunda), occurring in gullies and on lower slopes, away from floodplains. This vegetation is consistent with that of Hunter Lowland Redgum Forest Endangered Ecological Community, which is listed as an endangered ecological community under the TSC Act. However, it is not consistent with any communities listed under the EPBC Act. United Wambo Project - Groundwater Impact Assessment (G1733) 55
River Red Gum Stands (Eucalyptus camaldulensis) River red gum (Eucalyptus camaldulensis) is listed as an endangered population in the Hunter catchment under the TSC Act. It has been recorded at several locations along the within the predicted drawdown zone in the riparian zone of Wollombi Brook and Redbank Creek. These records comprise approximately 20 isolated trees; however more may be present. River red gum is a known phreatophyte (deep rooting plant that draws water from the water table) (Ecoscape (Australia) Pty Ltd 2011) and is subsequently considered to be groundwater dependent. Warkworth Sands Woodland Also occurring nearby is the Warkworth Sands Woodland. It is a highly restricted vegetation community that occupies Aeolian sand deposits in the local area. It is listed as an endangered ecological community under the TSC Act, and is proposed to be listed as a critically endangered ecological community under the EPBC Act. It is understood to be at least partially dependent on groundwater, particularly where it exists in swales between dune ridges, although this groundwater usually sits as a lens or perched aquifer above semi-permeable argillaceous (clayey) material. Stygofauna A baseline stygofauna assessment has also been conducted by Stygoecologia. The assessment is the first conducted across the Project Area, and consisted of field sampling in December 2015. As part of the fieldwork 20 bores/wells, within alluvium along Wollombi Brook and its minor tributaries, were sampled. The results show that stygofauna exist in small isolated populations within the areas assessed. There were no listed threatened species collected; however, as is the case for most assessments in this emerging field, all species are likely to be new to science. The results of the current survey indicate that the ecosystem condition within Wollombi Brook Alluvium is currently stable along this sub-catchment, as indicated by the relatively consistent invertebrate community composition. There appears at this stage to have been no adverse effects on the subterranean aquatic ecosystem as a result of previous mining operations at Wambo or United, although the original extent of the community was not determined. United Wambo Project - Groundwater Impact Assessment (G1733) 56
5.6 Conceptual model This section describes the processes that control and influence the storage and movement of groundwater in the hydrogeological system. Figure 5-13 and Figure 5-14 represent cross-sections through the Project Area from west to east and from south to north, respectively. The location and alignment of the cross-sections is shown in Figure 5-12. The cross sections graphically show the main processes influencing the groundwater regime, including recharge, flow directions and discharge. The main groundwater bearing unit occurring near the Project Area is the Quaternary alluvium, with less productive aquifers occurring within coal seams of the Wittingham Coal Measures. The Triassic Narrabeen Group, present to the south-west of the Project Area, also contains thick sequences of groundwater bearing sandstones, but these are not directly connected with the Project Area. Groundwater flows from areas of high head (pressure plus elevation) to low head via the most permeable and transmissive pathways. The Wittingham Coal Measures outcrop some 8km to the north and east of the Project Area. Recharge occurs from direct rainfall to the ground surface infiltrating into the formations through a thin soil cover and weathered profile. The coal seams also occur at subcrop in localised zones along the Hunter River and Wollombi Brook, and are recharged by the overlying alluvium where gradients promote this flow. Recharge also occurs via downward leakage from the Triassic Narrabeen Group. The potentiometric surface and flow direction is a subdued reflection of topography, with groundwater within the Wollombi Brook alluvium flowing in a north to north-easterly direction towards the Hunter River, which flows in an easterly direction. The Quaternary alluvium is an unconfined groundwater system that is recharged by rainfall infiltration, streamflow and upward leakage from the underlying stratigraphy, particularly along Wollombi Brook. Regionally, the Hunter River and Wollombi Brook are predominantly gaining water from the surrounding alluvium, as well as from rainfall and regulated flow (i.e. dam releases). However, there are also areas where the rivers recharge the underlying alluvium. These losing conditions can occur around areas of active mining, where the hydraulic gradient is increased due to depressurisation of the underlying coal measures. Losing conditions also occur within the more topographically elevated tributaries of the main water courses, where the water table is deeper and not connected directly to the streams. The direction of groundwater flow for the Wittingham Coal Measures is influenced by the local geomorphology and structural geology, as well as the long history of mining within the region. The coal measures form unconfined groundwater systems at outcrop, becoming confined as they dip towards the south-west. United Wambo Project - Groundwater Impact Assessment (G1733) 58
400 B B W Rainfall E 300 200 Wambo Open Cut United Open Cut Wollombi Brook Rainfall 100 0-100 -200-300 -400 Whybrow Seam Wambo Seam Blakefield Seam Arrowfield Seam Bowfield Seam Warkworth Seam Quaternary alluvium Triassic Narrabeen Group Newcastle Coal Measures 2000 4000 6000 8000 10000 12000 Interburden (Wittingham Coal Measures - Jerrys Plains Subgroup) Coal (Wittingham Coal Measures - Jerrys Plains Subgroup) Maximum depth of mining Final landform Ground surface Weathered profile (CSIRO, 2015) Inferred direction of flow Inferred Vaux potentiometric surface post mining Mt Arthur Seam Vaux Seam Bayswater Seam Alluvial water table Inferred Vaux potentiometric surface during mining Schematic section showing conceptual hydrogeology - west to east Figure 5-13 United Wambo Project - Groundwater Impact Assessment (G1733)
C C S N 400 300 200 Wollombi Brook United Open Cut Rainfall HVO South Hunter River Rainfall 100 0 Whybrow Seam Currently spoil Vaux Seam Vaux Seam -100 Wambo Seam Bayswater Seam -200-300 Blakefield Seam Arrowfield Seam Warkworth Seam Vaux Seam -400 2000 4000 6000 8000 10000 12000 Quaternary alluvium Maximum depth of mining Ground surface Alluvial water table Interburden (Wittingham Coal Measures - Jerrys Plains Subgroup) Final landform Weathered profile (CSIRO 2015) Inferred Vaux potentiometric surface during mining Coal (Wittingham Coal Measures - Jerrys Plains Subgroup) HVO South current depth of mining Inferred direction of flow Inferred Vaux potentiometric surface post mining Schematic section showing conceptual hydrogeology - south to north Figure 5-14 United Wambo Project - Groundwater Impact Assessment (G1733)
6 Numerical groundwater model This section presents the results from numerical groundwater modelling and is structured as follows: Section 6.1 describes the proposed open cut mining activities. Section 6.2 provides an overview of the groundwater model developed to assess the impact of mining. Appendix B provides a detailed technical description of the model development, construction and calibration. Section 6.3 outlines the peer review process followed as part of the groundwater assessment 6.1 Overview of mining 6.1.1 Proposed mine plan The Project involves extension of the approved Wambo Open Cut and deepening of the pit down to the base of the Warkworth Seam, and the development of a new United Open Cut that will be mined to the base of the Vaux seam. Mining is proposed to occur for a period of 23 years from the date of approval. For modelling purposes, this has been assumed to be from 2017 to 2039. Where the model results are presented in Section 7, year one results represent 2016 and year two results represent 2017, the year when the Project commences. Open cut mining will target the Wittingham Coal Measures over the full extent of the mining area. Overburden removal will involve the use of truck and excavator pre-stripping. In order to achieve the most efficient extraction of coal, several mining areas may be active at any point in time. As the open cut pit develops and progresses, overburden will be placed progressively within the mined out areas, with final voids positioned at the western extent of the United Open Cut and the south-eastern extent of the Wambo Open Cut. 6.2 Overview of groundwater modelling A 3D numerical groundwater flow model was developed for the Project using MODFLOW-USG. A detailed description of the modelling logic is provided in Appendix B. The model represented the key geological units as 34 layers. The model extended approximately 23km from east to west, and 27.8km from north to south comprising up to 54,382 cells per layer, making it spatially a relatively large model (Figure 6-1). The model was built to represent the conceptual model of the groundwater regime summarised in Section 5.6, and detailed in Appendix B. The numerical model was based on the existing Wambo numerical flow model and updated with data from the United and Wambo geological models as well as publicly available data (i.e. geological maps and groundwater studies for the surrounding region). The model extended north to include the HVO and Ravensworth operations, and east and south to include MTW. The model was used to identify the influence of the Project on the groundwater regime by comparing the impacts generated by the approved and proposed mine plans. All currently approved and foreseeable mine plans within the region (i.e. Wambo, HVO South, HVO North, MTW, Ravensworth) were included in order to account for cumulative impacts. This includes the Wambo underground mine plan within Modification 12, as presented in Section 1.1.1. Mining was represented in the model using the drain package, with the drain cells set to the base of the target coal seam for each pit. Further details about how mining within the region was represented in the model are included in Appendix B. United Wambo Project - Groundwater Impact Assessment (G1733) 61
The selection of appropriate boundary conditions, locations and alignments was based upon a detailed review of all available geological and hydrogeological information, as well as the topography and the proximity of the Project Area to private groundwater users and surrounding mines. The model was calibrated using existing groundwater levels at representative bores located within the model domain that were considered to be reliable. A detailed description of the calibration procedure is provided in Appendix B. The objective of the calibration was to replicate the groundwater levels measured in the site monitoring network and available private bores, in accordance with Australian groundwater modelling guidelines (Barnett et al. 2012). The transient calibration achieved a 3.14% scaled root mean square (SRMS) error, which is well within acceptable limits (i.e. 10%), recommended by the Australian groundwater modelling guidelines (Barnett et al. 2012). Following calibration the model was used to predict the groundwater levels, drawdown and the amount of groundwater intercepted in response to the Project, in accordance with the proposed mine plan. Mining was simulated down to the base of the Vaux Seam at United Open Cut and down to the Warkworth Seam at Wambo Open Cut, defined as layers 29 and 23 in the model, respectively. The model was used to identify the influence of the Project on the groundwater regime by comparing the impacts generated by the approved and proposed mine plans across Wambo and United. All currently approved and foreseeable mine plans within the region (ie HVO South, HVO North, Ravensworth and MTW) were included in order to account for cumulative impacts. Mining was represented in the model using the drain package, with the drain cells set to the base of the target coal seam for each pit. Further details about how mining within the region was represented in the model are included in Appendix B. In order to assess the change in the groundwater regime due to the Project, two model scenarios were run and their results compared. The two scenarios were: Approved - with all currently approved and foreseeable operations within the region, including approved open cut and underground mining at Wambo and United, as well as approved mining at surrounding operations (i.e. HVO South, HVO North, Ravensworth and MTW). Approved + Project which includes all approved and foreseeable operations (as above) as well as the Project. A No United and Wambo model scenario was also developed, which excluded all future mining at United and Wambo (open cut and underground), but included all approved and foreseeable mining at HVO South, HVO North, Ravensworth and MTW. The No United and Wambo scenario was run in order to help quantify total license requirements and compare impacts between the Project and currently approved operations at United and Wambo. However, it should be noted that all currently approved operations at Wambo and United have been approved based on previously completed groundwater assessments. United Wambo Project - Groundwater Impact Assessment (G1733) 62
The sensitivity of the model predictions to the input parameters was analysed. The analysis focussed on varying model parameters and design features that could most influence the model predictions. The model parameters were adjusted to encompass the range of likely uncertainty. Sensitivity analysis included testing the effects of changes in: horizontal and vertical hydraulic conductivity; specific yield and specific storage of all geological units and overburden; and the rainfall recharge rate across the model domain and overburden. Appendix B provides a detailed discussion of the sensitivity and uncertainty analyses and Section 7 describes the groundwater model predictions. 6.3 Peer review An external peer review was conducted by Dr Noel Merrick of HydroAlgorithmics, who has over 40 years of experience in hydrogeological investigations and groundwater modelling. The review was in accordance with the Australian groundwater modelling guidelines (Barnett et al. 2012) and included input and involvement from Dr Merrick over the three main stages of numerical groundwater modelling as follows: conceptualisation and model development; model calibration; and model predictions. The overall peer review report for the groundwater assessment is presented in Appendix D. United Wambo Project - Groundwater Impact Assessment (G1733) 63
7 Model predictions and impact assessment This section describes the numerical model predictions and impacts of the Project including the: groundwater intercepted by mining within the Project Area and the contribution from the Permian coal measures (Section 7.1); drawdown in groundwater levels in the alluvium and coal measures as a result of the Project proposed modification (Section 7.1.2); change in alluvial water resources availability (Section 7.1.3); changes to surface water flow (Section 7.1.4); water licensing requirements (Section 7.1.5); impact on supplies from private bores (Section 7.1.6); and drawdown at potential groundwater dependent ecosystems (Section 7.1.7). Cumulative impacts are outlined in Section 7.2, post closure impacts are discussed in Section 7.3 and groundwater quality changes are presented in Section 7.4. 7.1 Project groundwater predictions 7.1.1 Groundwater intercepted by mining Figure 7-1 shows the water intercepted from the Permian coal measures as part of the currently approved and foreseeable operations (i.e. approved areas of Wambo Open Cut and Wambo Underground) and the Project (shown in red and blue) during the lifetime of the Project. The United open cut is proposed to mine through previous underground workings in the Arrowfield Seam where there is potential for stored water to be present. Figure 7-1 shows only groundwater from undisturbed formations surrounding the mining areas and does not represent stored water in mine workings or spoils. There are no direct flows from alluvium or surface water, as discussed further in Section 7.1.3. United Wambo Project - Groundwater Impact Assessment (G1733) 65
Groundwater volume intercepted (ML/yr) 2500 2000 1500 1000 500 Approved underground operations only Approved open-cut operations only Project only - United Open Cut Project only - Wambo Open Cut 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (years of mining) Figure 7-1 Groundwater intercepted from Permian coal measures As shown in Figure 7-1, groundwater intercepted from the Permian coal measures due to the Project at United Open Cut is predicted to peak in year 5 with 582ML/year of groundwater intercepted. Groundwater intercepted at the Wambo Open Cut peaks in year 8 at 76ML/year. Overall, the additional take of groundwater due to the Project is predicted to peak in year 7 at 633ML/year, and average 234ML/year. When including currently approved and foreseeable open cut and underground operations, the peak take of groundwater from the Permian coal measures occurs in year 5, at a rate of 1778ML/year. From year 5 this rate reduces over the life of the mine, to an average of 982ML/year. 7.1.2 Drawdown and depressurisation during mining operations Figure 7-2 to Figure 7-6 show the predicted maximum drawdown due only to the Project within the Quaternary alluvium, Wambo Seam, Glen Munro Seam, Arrowfield Seam and Vaux Seam. Figure 7-2 shows that the Quaternary alluvium receives drawdown up to 3km north of Wambo Open Cut and 2km east of United Open Cut. It should be noted that the drawdown levels are a reflection of drawdown through the model cells, irrespective of actual saturated thickness of the groundwater systems. Therefore, the drawdowns simulated can exceed the saturated thickness of the alluvium. The most significant modelled drawdowns within the Quaternary alluvium are predicted to occur east of United Open Cut along Wollombi Brook and Redbank Creek, as well as north along the edge of the Hunter River alluvium. United Wambo Project - Groundwater Impact Assessment (G1733) 66
As shown in Figure 7-3, the zone of depressurisation in the Wambo Seam is predicted to extend up to 2.5km south-west of the proposed extraction area. Groundwater level drawdown within the Glen Munro Seam extends up to 2.5km west of the proposed extraction area, and up to 2km south (Figure 7-4). The zone of depressurisation in the Arrowfield Seam is predicted to extend up to 3.5km from the edge of the proposed extraction area (Figure 7-5). In all coal seam layers, the magnitude of the depressurisation is generally less than 10m at a distance of 1.5km from the edge of the pits. The zone of depressurisation in the Vaux Seam (Figure 7-6) is generally less extensive to the south-west (down-dip) compared to the shallower seams, due to the lower permeability of this coal seam within the model. Figure 7-2 to Figure 7-6 show the predicted maximum drawdown due to the Project, as well as the cumulative impacts from all currently approved mine operations within the region. The extent of drawdown due to the Project is generally within the extent of currently approved drawdown to the north, east and south of the Project Area. Increased drawdown extent due to the Project is largely restricted to the west of the Project Area, extending up to 2km from approved and foreseeable cumulative drawdown extents. Drawdown figures for the shallower layers (Triassic Narrabeen Group and Newcastle Coal Measures) have been excluded due to the lack of potential impacts within these shallow units. This includes no drawdown due to the Project within the Triassic Narrabeen Group, which is the main stratum across the Wollemi National Park. The lack of drawdown is due to the strata being largely absent across the proposed disturbance area, as well as the relatively low vertical hydraulic conductivity of the coal measures. United Wambo Project - Groundwater Impact Assessment (G1733) 67
7.1.3 Change in alluvial water resources The change in alluvial water resources was determined by comparing water budgets for alluvial zones using versions of the numerical model that contained and excluded the Project. The two main alluvial resources are alluvium associated with Wollombi Brook, and alluvium associated with the Hunter River. Results for the Wollombi Brook alluvium were based on the full length of the Wollombi Brook within the model domain, divided into highly productive and less productive alluvium. The results for the Hunter River alluvium were based on the full length of the Hunter River within the model, which included sections upstream and downstream of Foy Brook. The Hunter River alluvium budget zone was also divided into highly and less productive alluvium. The results for the total take from alluvium is the combined total flow change within the highly and less productive alluvium. In accordance with the AIP, the model was used to determine the mining interference on this groundwater system. As the Permian strata become depressurised, flow from the Permian to the alluvium within the zone of depressurisation will progressively decrease. This can be considered beneficial as it reduces the inflow rate of higher salinity groundwater from the Permian to the overlying alluvium. Figure 7-7 and Figure 7-8 show the net flow from the alluvium to the Permian due to approved and foreseeable mining (blue line) and approved mining plus the Project (red line). Predicted net flow from alluvium to Permian was also predicted for the No United and Wambo scenario (brown dashed line), as discussed in Section 6.2. The net flow is the difference between groundwater flows into the alluvium (from gaining zones) and out of the alluvium (from losing zones). Figure 7-7 shows the change in flow from the Permian to the Wollombi Brook alluvium for the currently approved mine plans with and without the Project. The approved mining includes the approved and foreseeable mine plans for HVO South, HVO North, Ravensworth and MTW. The positive fluxes in Figure 7-7 indicate Wollombi Brook alluvium is overall gaining flow from the Permian. Net groundwater flux from alluvium to Permian (ML/year) 600 500 400 300 200 100 0 Approved mining Approved + project No United or Wambo 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Additional groundwater take from alluvium (ML/year) 200 180 160 140 120 100 80 60 40 20 0-20 Project only Approved only 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Year Figure 7-7 Net change in flow from Permian to Wollombi Brook alluvium due to mining United Wambo Project - Groundwater Impact Assessment (G1733) 73
The results show the Project reduces flow from Permian to the alluvium along Wollombi Brook by up to 40ML/year. It is therefore a relatively small additional impact on top of the cumulative impacts for currently approved mines. As shown in Figure 7-7, currently approved and foreseeable operations at Wambo and United are predicted to reduce flow from Permian to the alluvium along Wollombi Brook by up to 175ML/year. It should be noted that while the reduction in flow from Permian to the alluvium along Wollombi Brook by up to 40ML/year may reduce water levels within the alluvium, the reduction will also improve water quality within the alluvium. The influence of groundwater mixing between the alluvium and Permian coal measures is discussed under Section 5.4. Figure 7-8 shows the flow from the Hunter River alluvium to the Permian strata, as well as the overall additional water take from the alluvium due to the Project. The negative fluxes indicate Hunter River alluvium is overall losing flow to the Permian. Again, the cumulative impacts are evident in the graph, with increasing losing conditions over the Project life. The relatively small additional impact, on top of the already approved cumulative impact is evident. Net groundwater flux from alluvium to Permian (ML/year) 0-100 -200-300 -400-500 -600-700 -800 Approved mining Approved + project No United or Wambo 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Additional groundwater take from alluvium (ML/year) 70 60 50 40 30 20 10 0-10 -20-30 Project only Approved only 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Year Figure 7-8 Net change in flow from Permian to Hunter River alluvium due to mining Overall the results show that up to an additional 58ML/year of groundwater from the Hunter River alluvium will leak into the underlying Permian coal measures, due to depressurisation of the Permian strata with the Project. As shown in Figure 7-8, currently approved and foreseeable operations at Wambo and United are predicted to intercept up to 45ML/year from the Hunter River alluvium. United Wambo Project - Groundwater Impact Assessment (G1733) 74
7.1.4 Changes to surface water flow Loss of groundwater from the alluvium will also induce some loss of surface water from both the Wollombi Brook and Hunter River. Figure 7-9 and Figure 7-10 show the predicted net river baseflow over the proposed Project life for Wollombi Brook and Hunter River, respectively. The negative flux in Figure 7-9 shows that overall the Wollombi Brook is a net gaining system, with water flowing from the alluvium to the Wollombi Brook (baseflow). Net groundwater flux from alluvium to Wollombi Brook (ML/year) -1600-1500 -1400-1300 -1200-1100 -1000-900 -800 Approved mining Approved + project No United or Wambo 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Loss of baseflow (ML/year) 200 180 160 140 120 100 80 60 40 20 0 Project only Approved only 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Year Figure 7-9 Wollombi Brook baseflow change Cumulative impacts from approved mining (i.e. HVO South, MTW and approved mining at Wambo) reduce the net baseflow to Wollombi Brook from 1,450ML/year to 1,000ML/year. As shown in Figure 7-9, currently approved and foreseeable operations at Wambo and United are predicted to reduce the net baseflow to Wollombi Brook by up to 180ML/year. The Project accounts for between 1ML/year and 37ML/year (Year 8) of the cumulative impacts on baseflow. This is a small proportion of the total baseflow, at around 3% when compared to the modelled approved surface water flux. This was calculated using the peak take in year 8 of 37ML/year, divided by the net flux in year 8 for the approved operations of 1402ML/year. United Wambo Project - Groundwater Impact Assessment (G1733) 75
Net groundwater flux from alluvium to Hunter River (ML/year) -3600-3400 -3200-3000 -2800-2600 -2400 Approved mining Approved + project No United or Wambo 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Loss of baseflow (ML/year) 70 60 50 40 30 20 10 0-10 -20-30 Project only Approved only 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Year Figure 7-10 Hunter River baseflow change Figure 7-10 indicates that there would be a gradual reduction of flow from 3,500ML/year to 2,800ML over the project life due to cumulative impacts. As shown in Figure 7-10, currently approved and foreseeable operations at Wambo and United are predicted to reduce the net baseflow to Hunter River by up to 46ML/year. The Project accounts for up to 58ML/year (Year 11) of the cumulative impact on the Hunter River baseflow. This is a small proportion of the total baseflow, at around 2% contribution. This was calculated using the peak take in year 11 of 58ML/year, divided by the net flux in year 11 for the approved operations of 3226ML/year. When considering the river budgets it is important to note the underlying assumptions in the model. The model assumes direct hydraulic connection between the river and the aquifer, and no limit on the volume of water that can leak from the river into the underlying aquifer. In reality losing zones in the river can be physically separated from the underlying water table in the aquifer by unsaturated zones. In this case drawdown within the alluvium or Permian strata does not increase the rate of flux from the river as it does in the model. Where the river and the aquifer are directly connected through the saturated zone, the water take from the alluvium as discussed above in Section 7.1.3 directly accounts for water take from the river. 7.1.5 Water licensing As discussed in Section 2, the Project Area is under the Hunter Unregulated and Alluvial Water Sources WSP and the Hunter Regulated River Water Source WSP (Hunter River flows). For the Hunter Unregulated and Alluvial Water Sources, the Project Area falls within the Lower Wollombi Brook Water Source and near the Jerrys Management Zone and Glennies Creek Management Zone. Surface water flows in Wollombi Brook are also covered under the Hunter Unregulated and Alluvial Water Sources WSP, and the porous hard rock units (coal and Triassic sandstones) are covered under the North Coast Fractured and Porous Rock WSP. United Wambo Project - Groundwater Impact Assessment (G1733) 76
The predicted annual groundwater volumes required to be licensed over the life of mining at United and Wambo for the currently approved and foreseeable mine plans (open cut and underground) and the Project are summarised in Table 7-1. Table 7-1 Groundwater licensing summary during mining Water Sharing Plan/ Management Zone Source Predicted maximum annual inflow volumes requiring licensing during mining (ML/year) Approved mine plan* Approved and Project Project only Maximum volume required to be licensed for Project (ML/year) Hunter Unregulated and Alluvial Water Sources WSP/ Lower Wollombi Brook Water Source Wollombi Brook (SW) Wollombi Brook alluvium Hunter River alluvium 180 (197) (37) (175) 260 40 (45) (81) (58) 40 Hunter Regulated River Water Source/ Glennies Creek Management Zone North Coast Fractured and Porous Rock WSP Hunter River (SW) Coal measures (porous rock) 46 84 58 58 1287 1778 633 633 Notes: (197) brackets denote predicted take that is not included in the license requirements as the volume is captured within either surface water or alluvial licensed volume (i.e. double accounting) SW surface water * Approved mine plan results derived by comparing interception of groundwater by approved and foreseeable operations (excluding the Project) at Wambo and United, compared to flow budgets of a model run with no mining at Wambo and United from 2016. Maximum take varies by year, therefore the difference between approved and approved with Project does not directly compare to maximum take for the Project only The Hunter Unregulated and Alluvial Water Sources WSP cover alluvial groundwater and flows in Wollombi Brook; therefore, to avoid double accounting the licensed volume under the WSP is based on the take from alluvium. As the Hunter River falls under a separate WSP to the Hunter River alluvium, to avoid double accounting the licensed volume for the Hunter River alluvium excludes the volume accounted for under the Hunter River (surface water). Partitioning of the water licenses is further depicted in Figure 7-11. As reported in Section 2.5, the proponents have a combined total entitlement of 370ML/year assuming full allocation under the Hunter Unregulated WSP, and 1306ML/year under the Hunter Regulated WSP. The model predicts that during the life of the mine, the Project has a maximum groundwater take under the Hunter Unregulated WSP of 40ML/year, and 58ML/year under the Hunter Regulated WSP. Based on the approved, foreseeable and the Project mine plans for United and Wambo, the groundwater model predicts that the maximum take from alluvium per year under the Hunter Unregulated WSP is 260ML/year, which is within the currently held entitlement. The predicted take from the Hunter Regulated WSP is up to 84ML/year, which is within the currently held entitlement. United Wambo Project - Groundwater Impact Assessment (G1733) 77
Combined entitlements held by the proponents for take from the Permian groundwater system under the North Coast Fractured and Porous Rock WSP are 1947ML/year. The groundwater model predicts that during the life of the mine, the Project will intercept up to 633ML/year of groundwater under the North Coast Fractured and Porous Rock WSP. It is also predicted that up to 1778ML/year of groundwater within the Permian coal measures will be intercepted with the Project and currently approved and foreseeable operations at Wambo and United, which is within the currently held entitlement. Figure 7-11 Partitioning of water take from streams and alluvium for the Project 7.1.6 Drawdown in private and mine owned bores Table 7-2 summarises the maximum predicted drawdown in groundwater levels at private bores, other mined owned bores and bores on Wambo owned land. The table presents all bores that recorded a cumulative drawdown of over 2m and with drawdown due to the Project. Table 7-2 Predicted cumulative drawdown over 2m in private and mine owned bores Registered No./Name Screen zone Ground level (mahd) Bore depth (m) Water column (m) Maximum drawdown during mining (m) Project only Cumulative Maximum drawdown post mining (m) Project only Cumulative Land owner GW060780 Pswj 104 25.5 7 6.1 6.7 1.8 3.1 Private GW060750 Pswj 59 24.4 15* 0.5 4.3 1.6 1.7 Coal & Allied GW017799 Pswj 109 12.2 0 7.0 15.4 12.9 19.9 GW017798 Pswj 87 12.2 0 13.3 20.7 12.9 23.8 GW017646 Qa 73 11* 5* 1.6 2.2 0.0 0.6 Wambo owned land Notes: Qa - Quaternary alluvium Pswj Weathered Permian coal measures * - No bore construction details and/or water level information available water column an estimate only MB monitoring bore United Wambo Project - Groundwater Impact Assessment (G1733) 78
During mining operations the Project is predicted to impact one privately owned bore (GW060780), which is located north of the Project Area and installed within the shallow weathered coal measures. The model predicts that private bore GW060780 will experience a maximum 6.7m decline in groundwater levels, with the Project predicted to account for 6.1m of drawdown during active mining. Currently groundwater levels at GW060780 are 6.9m above the base of the bore; therefore, drawdown during mining may impair the capacity of the bore. Following mining the groundwater levels recover and the maximum drawdown post-mining is predicted to be 3.1m below 2015 groundwater levels, of which the project accounts for 1.8m of water level drawdown. It is therefore predicted the bore, if repaired, will remain usable, but with a reduced peak pumping capacity due to the predicted decline in water level. The model also predicts that bore GW060750 (Coal & Allied bore) will experience a maximum 4.3m decline in groundwater levels, with the Project predicted to account for 0.5m of drawdown during active mining. Following mining the groundwater levels recover and the maximum drawdown post-mining is predicted to be 1.7m below 2015 groundwater levels, of which the Project accounts for 1.6m of water level drawdown. The results show that cumulative impacts result in a decline in groundwater levels in excess of 2m; however during operations, the Project has only a minimal contribution to existing impacts and when considered alone does not trigger the AIP minimum impact criteria. Including bores on land owned by Wambo, the greatest decline is predicted for bore GW017798, which is installed within the Permian coal measures within 1km of the proposed Wambo Open Cut. The model predicts a maximum decline of approximately 21m, which is well below the constructed depth of the bore. However, it should be noted that the current status of the bores is unknown, with the model predicting that the bore is currently dry. Groundwater monitoring will continue to be conducted over the life of the mine to confirm the actual extent of groundwater impacts and to validate the conservative predictions, particularly with regard to interference drawdown effects on private bores. As part of operational and mine closure planning, the proponent will make-good any bores that have greater than 2m drawdown interference if it can be demonstrated that this interference is due to mining rather than natural climatic variability. Section 10 describes the groundwater monitoring program in details. 7.1.7 Impact on groundwater dependent ecosystems As detailed under Section 5.5, potential GDEs have been identified primarily in riparian vegetation along the main water courses. Figure 7-12 shows the location of the identified GDEs along with the maximum cumulative drawdown predicted within the Quaternary alluvium. United Wambo Project - Groundwater Impact Assessment (G1733) 79
Figure 7-12 GDEs and predicted maximum cumulative drawdown in alluvium Figure 7-12 identifies two areas within the zone of cumulative drawdown where GDEs may be present. To assist discussion of results, these zones have been labelled GDE1 and GDE2. It should be noted that the drawdown levels are a reflection of drawdown through the model cells, irrespective of actual saturated thickness of the groundwater systems. Therefore, the drawdowns simulated can exceed the saturated thickness of the alluvium. As presented in Section 5.3, the alluvium within these areas has a maximum saturated thickness of up to 10 m. Around 1m in groundwater level decline is predicted at GDE2 due to cumulative impacts from mining (approved mining and the Project). The decline in groundwater levels at GDE2 is along the fringes of Wollombi Brook. This drawdown is relatively limited in area and impacts upon only a small portion of possible Hunter Valley River Oak Forest. At GDE1 groundwater levels are predicted to decline more significantly with mining (approved mining and the Project). Figure 7-13 shows the predicted decline in groundwater levels at location of GDE1 for approved mining only (i.e. HVO South, Wambo, MTW) and for approved mining plus the Project. Figure 7-13 shows that the alluvium near GDE1 becomes largely unsaturated due to cumulative impacts from approved mining. The figure also shows the minimum elevation of 40mAHD for the alluvium near GDE1, in order to show the point where the alluvium becomes unsaturated. United Wambo Project - Groundwater Impact Assessment (G1733) 80
50.0 45.0 Groundwater level (mahd) 40.0 35.0 30.0 25.0 20.0 15.0 Approved mining (GDE1) Approved and Project (GDE1) Unsaturated alluvium Figure 7-13 Predicted groundwater level decline in alluvium at zone GDE1 As shown in Figure 7-13, there is potential for cumulative impacts of the already approved mining (i.e. HVO South, Wambo, MTW) to reduce alluvial groundwater levels below the base of alluvium at GDE1, due to direct take with mining (HVO South) and reduced contributions from the underlying Permian coal measures. The impact of the Project results in this occurring more gradually and some 1 year earlier. Therefore the Project only influences the timing of the impact, not the magnitude. As discussed in Section 5.5.2, stygofauna were identified within alluvium along Wollombi Brook and minor tributaries. Stygofauna are potentially threatened by activities that change the quality or quantity of groundwater, disrupt connectivity between the surface and aquifer, or remove living space. Groundwater levels are predicted to decline within the alluvium. However, as concluded by Stygoecologia, the stygofauna were assessed as having a low risk of mining related impacts based on the level of modelled drawdown within the alluvium. Further details about the stygofauna study and predicted impacts on stygofauna can be found within Appendix E. 7.2 Cumulative drawdown Approved coal mines within the region operate below the water table and therefore extract groundwater and create a cumulative drawdown on the groundwater system. No coal seam gas extraction projects are currently in operation or proposed near the Project Area based on publicly available information. The numerical groundwater model was used to assess the surrounding mine cumulative drawdown. The surrounding mines included approved and foreseeable operations at Wambo, HVO South, HVO North, Ravensworth and MTW that mine the economic coal seams of the Wittingham Coal Measures. The simulation of mining at these sites using the numerical model was derived from publicly available approved mine plans and knowledge of mining in the region. Figure 7-14 to Figure 7-18 show the maximum cumulative drawdown for the key stratigraphic units. Due to the long history of mining within the region, the cumulative drawdown was determined by comparing to 2015 groundwater levels. United Wambo Project - Groundwater Impact Assessment (G1733) 81
Figure 7-14 shows that the cumulative drawdown within the Quaternary alluvium extends along Wollombi Brook and Hunter River, adjacent to mining operations (i.e. Wambo, HVO South, HVO North, Ravensworth and MTW). It should be noted that the model predicted drawdown in certain areas exceeds the saturated thickness of the alluvium. The most significant modelled drawdowns within the Quaternary alluvium are visible east of United Open Cut, along Wollombi Brook and Redbank Creek. Figure 7-15 shows the cumulative drawdown within the Wambo Seam of the Wittingham Coal Measures. Drawdowns are largely within the extent of currently approved cumulative drawdown for the Wambo Seam. Figure 7-16 shows the cumulative drawdown within the Glen Munro Seam of the Wittingham Coal Measures. Drawdowns extend up to 1km west of the extent of currently approved cumulative drawdown for the Glen Munro Seam, but are within the extent elsewhere. Figure 7-17 shows the cumulative drawdown within the Arrowfield Seam of the Wittingham Coal Measures. Drawdowns extend from 3km north-west of the Project Area, down to the MTW operations to the south-east. The most significant drawdowns are visible within the actively mined areas (open cut and underground). Drawdowns extend up to 2.5km west of the extent of currently approved cumulative drawdown for the Arrowfield Seam, but are within the extent elsewhere. Figure 7-18 shows that the cumulative drawdown within the Vaux Seam extends up to 10km north of the Project Area, and 11km south-east of the Project Area. The extent of drawdown in the deeper Vaux Seam is greatest where it occurs at shallow depths and is accessible to mining (i.e. HVO North, HVO South, Wambo and United). Drawdowns extend up to 2km south-west of the extent of currently approved cumulative drawdown for the Vaux Seam, but are within the extent elsewhere. United Wambo Project - Groundwater Impact Assessment (G1733) 82
7.3 Post mining recovery conditions Post mining conditions were also simulated using the numerical model. Appendix B provides details of the model set up and the location of the final voids are shown in Figure 1-2. The sections below describe the post mining predictions of the pit lake levels, potentiometric surface and water table recovery, as well as the changes in water take from the alluvium and stream flow and water quality variation. These predictions are based on the assumption that there would be no future mining within the existing or new mine leases. 7.3.1 Post closure groundwater recovery Post mining conditions were simulated over a period of 1000 years using groundwater levels from the end of mining, using groundwater levels as the starting heads after removal of all mine drain cells in the model. Groundwater inflows to the void during recovery were provided to the EIS surface water consultants and the results were incorporated in a high-resolution surface water model. Pit lake level recovery rates from the surface water model were reinstated to the groundwater model using a series of constant heads over time. This ensured consistency between the surface water and groundwater studies. The final landform developed by the proponent was added to the recovery model, which determined the design and location of the proposed final voids. Based on this landform, the final void within the Wambo Open Cut will be largely rehabilitated with spoil, to a minimum elevation of around 40mAHD. The United Open Cut final void is notably deeper, with depths down to -150mAHD. With the constant heads in place, the groundwater model was run for 1000 years in order to simulate the recover with a higher level of accuracy. The modelling results indicate that the final voids and associated in-pit overburden emplacement will gradually fill with water and groundwater over time. The final voids are predicted to reach a final pit lake level of approximately 55mAHD in Wambo Open Cut and 20mAHD in United Open Cut. These pit lake water levels are predicted to be about 30m to 50m below pre-mining groundwater levels, indicating that the voids will act as a sink in perpetuity with no escape of contained void water. There is no predicted interception of groundwater by the proposed final void within the Wambo Open Cut. This is due to the rehabilitated and shallow final landform. As a result, groundwater is instead drawn in towards the deeper final void within United Open Cut. Figure 7-19 shows the predicted water level within each pit void as it recovers with time. United Wambo Project - Groundwater Impact Assessment (G1733) 88
100 Pit lake level (mahd) 50 0-50 -100-150 -200 2020 2120 2220 2320 2420 2520 Year United Open Cut water level Figure 7-19 Wambo Open Cut water level Pit lake recovery The recovery and filling process will progressively decrease the hydraulic gradient and therefore magnitude of drawdown immediately surrounding the mined areas, and a new equilibrium groundwater level would be established around the final void. Figure 7-20 to Figure 7-24 show the predicted extent and magnitude of drawdown at post mining equilibrium conditions on the Quaternary alluvium and coal seam hydrogeological units (Wambo Seam, Glen Munro Seam, Arrowfield Seam and Vaux Seam). United Wambo Project - Groundwater Impact Assessment (G1733) 89
7.3.2 Permian groundwater intercepted post mining As detailed under Section 7.3.1, the modelling indicates the final void (and associated in-pit overburden emplacement) will gradually fill with water over time. The model predicts a final pit lake level of approximately 20mAHD in the United Open Cut and 55mAHD in the Wambo Open Cut. As the predicted pit lake levels are below pre-mining groundwater levels, the void will act as a sink and have a long term water take. The system equilibrates from approximately 250 years post mining, with the Project (United Open Cut and Wambo Open Cut) predicted to intercept approximately 202ML/year at equilibrium conditions. The approved open cut and underground operations at Wambo and United are predicted to intercept an additional 300ML/year at equilibrium. 7.3.3 Change in alluvial flow post mining Figure 7-25 shows the predicted flow budgets for the alluvium along Wollombi Brook and Hunter River from the post mining recovery model. The figure shows the net flow from the alluvium to the Permian for: approved mining (blue line); and approved mining plus the proposed modification (red line) and surrounding projects. The net flow is the difference between groundwater flows into the alluvium (from gaining zones) and out of the alluvium (from losing zones). Net groundwater flux from Wollombi Brook alluvium to Permian (ML/year) Net groundwater flux from Hunter River alluvium to Permian (ML/year) 600 400 200 0-200 -400-600 -800-1000 600 400 200 0-200 -400-600 -800 Approved mining Approved + project 0 200 400 600 800 1000 Year 0 100 200 300 400 500 600 700 800 900 1000 Figure 7-25 Net change in flow from Permian to alluvium post mining United Wambo Project - Groundwater Impact Assessment (G1733) 95
Figure 7-25 shows that, post mining, alluvial groundwater associated with Wollombi Brook will be recharged by flow from the underlying Permian coal measures. The currently approved operations are predicted to reduce the rate of upward leakage to the alluvium. The difference between the flux line for the approved and the approved plus Project in Figure 7-25 shows the change in flow due to the Project. The Project creates a further reduction in upward leakage of up to 144ML/year, which reduces to 86ML/year at 400 years post mining. The reduction in upward leakage may reduce water levels within the alluvium; however, the reduction will also potentially improve water quality within the alluvium. Figure 7-25 also shows that with the currently approved operations at Wambo and United, the Hunter River alluvium will remain a losing system post mining. The Project is predicted to further reduce baseflow contributions by up to 51ML/year, which reduces to 24ML/year from 400 years post mining. It should be noted that there are slight differences in groundwater flux between the predictive and recovery model runs. This is due to differences in model development and inputs, such as recharge rates. For example, the predictive model utilised average seasonal climatic conditions; however, due to the length of the recovery run, average annual climatic conditions were used. 7.3.4 Change in surface water flow post mining Figure 7-26 shows the predicted flow budgets for the Wollombi Brook and Hunter River (surface water flow) from the post mining recovery model. The negative flux shows that overall the Wollombi Brook and Hunter River are a net gaining system, with water flowing from the alluvium to the surface water feature (baseflow). Net groundwater flux from alluvium to Wollombi Brook (ML/year) Net groundwater flux from alluvium to Hunter River (ML/year) -2000-1800 -1600-1400 -1200-1000 -800-600 -400-4000 -3800-3600 -3400-3200 -3000-2800 -2600 Approved mining Approved + project 0 100 200 300 400 500 600 700 800 900 1000 0 200 400 600 800 1000 Year Figure 7-26 River baseflow change post mining United Wambo Project - Groundwater Impact Assessment (G1733) 96
Figure 7-26 shows that, post mining, both the Wollombi Brook and Hunter River maintain gaining conditions post mining for both the currently approved operations and the Project. The difference between the flux line for the approved and the approved plus Project in Figure 7-26 shows the change in flow due to the Project. The results for the Project indicate a decline in baseflow contribution to the Wollombi Brook of up to 139ML/year, which reduces to approximately 80ML/year from 400 years post mining. It is also predicted that the Project will reduce baseflow contributions to the Hunter River by up to 24ML/year from 400 years post mining. 7.4 Groundwater quality changes This section describes the potential sources of groundwater quality changes associated with the Project. 7.4.1 Overburden emplacement areas and final void lakes Overburden will continue to be placed within the open cut pit and progressively rehabilitated during mining. Under the Project, water will evaporate from the void lake surfaces, and groundwater will be drawn in from the surrounding geological units forming a sink in the environment. Evaporation from the lake surfaces will concentrate salts in the pit lake slowly over time. The AIP specifies that projects should not increase the long-term average salinity in a highly connected surface water source by than 1% per activity at the nearest point to the activity. As noted previously the gradually increasing salinity will not pose a risk to highly connected surface water sources as the final void will remain a permanent sink. In addition, while the alluvium near the Project maintain a losing condition, therefore the salinity of connected streams cannot increase due mining. The project is therefore considered to comply with this minimal harm consideration. 7.4.2 Hydrocarbons There is limited potential for groundwater contamination to occur as a result of hydrocarbon and chemical contamination. All refuelling activities will occur in areas with adequate bunding and/or provision for immediate clean-up of spills. All chemicals will be transported, handled and stored in accordance with relevant Australian Standards. These controls represent standard practice and a legislated requirement at mine sites for preventing the contamination of the groundwater regime. 7.4.3 Water storage Coarse and fine reject materials generated during the mining operations will be disposed into the currently approved Homestead and Homestead Main tailing storage facilities (TSFs) shown in Figure 1-2. In addition, coarse and fine reject materials are proposed to be disposed into a compartment within South Bates open cut pit once mining has completed. Water is also proposed to be stored within the United Underground. The influence of the TSFs was included within the predictive groundwater model, which identified that water associated with the stored fine reject materials would be drawn towards the active mine areas and captured within the Project Area. The potential storage of water within United Underground was not included within the numerical groundwater model. However, it is anticipated inclusion of stored water would buffer the extent and degree of drawdown within the Permian coal measures. This could potentially reduce the predicted impact on groundwater level drawdown. United underground is within the zone of drawdown during active mining. Therefore, it is anticipated that the stored water will be drawn towards the active mine area with little potential for interaction with the Quaternary alluvium and surface water features. As detailed in Section 7.2, it is predicted that the final voids for the Project will recover to a quasiequilibrium level of 20mAHD for United Open Cut and 55mAHD for Wambo Open Cut, which is well below pre-mining groundwater levels. As a result, it is predicted that the final voids will act as sinks to groundwater flow. This means any poor quality water from water storage will be captured in the final void lakes. Evaporation from the lake surface will concentrate salts in the lake slowly over time. United Wambo Project - Groundwater Impact Assessment (G1733) 97
7.5 Model uncertainty The uncertainty in the model predictions was assessed using a traditional sensitivity analysis where model inputs were changed individually to assess the impact upon the predictions. A more complex linear uncertainty analysis was also undertaken where numerous model inputs were changed at the same time. Appendix B presents the results of the sensitivity and uncertainty analyses. The sensitivity analysis identified that changes in hydraulic conductivity had the greatest influence on baseline calibration, pit inflows, alluvial flow and extent of groundwater level drawdown. As detailed in Section 5, Appendix A and Appendix B, extensive field data for hydraulic conductivity is available from studies conducted at site and at surrounding mines. Further details about the sensitivity analysis are presented in Appendix B. United Wambo Project - Groundwater Impact Assessment (G1733) 98
8 Compliance with NSW government policy 8.1 Aquifer Interference Policy Table 8-1 to Table 8-3 below compare the groundwater impact predictions for the Project against the requirements under the NSW AIP (NOW, 2012). Table 8-1 AIP requirement Accounting for or preventing the take of water Proponent response 1 Described the water source (s) the activity will take water from? Based on the AIP, the groundwater system impacted by the Project can be separated into two systems, as follows: porous and/or fractured consolidated sedimentary rock of the Permian coal measures; and groundwater within alluvium associated with the Hunter River and Wollombi Brook alluvium (both highly productive and less productive zones) 2 Predict the total amount of water that will be taken from each connected groundwater or surface water source on an annual basis as a result of the activity? 3 Predicted the total amount of water that will be taken from each connected groundwater or surface water source after the closure of the activity? 4 Made these predictions in accordance with Section 3.2.3 of the AIP? (page 27) Predicted take based on this modelling for the Project include: Permian coal measures: 633ML/year at peak, and 234ML/year on average Alluvium (Wollombi Brook): 40ML/year at peak Alluvium (Hunter River): 58ML/year at peak Surface water (Wollombi Brook): 37ML/year reduced baseflow at peak Surface water (Hunter River): 58ML/year reduced baseflow at peak Numerical modelling indicates that groundwater take due to the Project generally reduces post mining. However, the take from the Wollombi Brook alluvium and Wollombi Brook peaks within 250 years, as follows: Alluvium (Wollombi Brook): 144ML/year peak reduction in upward leakage Surface water (Wollombi Brook): 139ML/year peak reduced baseflow At equilibrium (1000 years post mining), the predicted take based on modelling for the Project includes: Permian coal measures: 202ML/year Alluvium (Wollombi Brook): 86ML/year reduction in upward leakage Alluvium (Hunter River): 24ML/year Surface water (Wollombi Brook): 80ML/year reduced baseflow Surface water (Hunter River): 24ML/year reduced baseflow Based on 3D numerical modelling. United Wambo Project - Groundwater Impact Assessment (G1733) 99
AIP requirement 5 Described how and in what proportions this take will be assigned to the affected aquifers and connected surface water sources? 6 Described how any licence exemptions might apply? 7 Described the characteristics of the water requirements? 8 Determined if there are sufficient water entitlements and water allocations that are able to be obtained for the activity? Proponent response Predicted take during mining based on modelling for the Project include: Permian coal measures: 633ML/year at peak, and 234ML/year on average Alluvium (Wollombi Brook): 40ML/year at peak, which increasing to a maximum of 144ML/year post mining Alluvium (Hunter River): 58ML/year at peak Surface water (Wollombi Brook): 37ML/year reduced baseflow at peak during mining, increasing to a maximum of 139ML/year post mining Not necessary. Surface water (Hunter River): 58ML/year reduced baseflow at peak Refer to surface water assessment The proponents have a combined total entitlement of 370ML/year assuming full allocation under the Hunter Unregulated WSP and 1306ML/year under the Hunter Regulated WSP. The groundwater model predicts that based on the proposed mine plan and already approved operations, the maximum take from alluvium under the Hunter Unregulated WSP is 260ML/year, and from the Hunter Regulated WSP is 84ML/year, which are within the currently held entitlements. Combined entitlements held by the proponents for take from the Permian aquifer under the North Coast Fractured and Porous Rock WSP are 1947ML/year. The groundwater model predicts that up to 1778ML/year of groundwater within the Permian coal measures will be intercepted with the Project and currently approved operations at Wambo and United, which is within the currently held entitlement. 9 Considered the rules of the relevant water sharing plan and if it can meet these rules? 10 Determined how it will obtain the required water? 11 Considered the effect that activation of existing entitlement may have on future available water determinations? 12 Considered actions required both during and post-closure to minimise the risk of inflows to a mine void as a result of flooding? 13 Developed a strategy to account for any water taken beyond the life of the operation of the Project? No cease to pump rules have been established for the Lower Wollombi Brook water source. The Hunter Unregulated WSP requires cease to pump rule be established by year 10 (2019). Via seepage to the mine face a portion will likely evaporate or be removed as moisture in coal and will not enter the site water circuit. Abstraction bores also operate on site, that abstract water from the historic underground workings. Under the Lower Wollombi Brook water source of the Hunter Unregulated WSP, the government has issued total groundwater entitlements of 5,071ML/year. That status and usage of existing entitlements is not available within the public domain. However the Project is predicted to take 40ML/year, which accounts for less than 1% of entitlements. Open cut mine plans have been designed to be located outside of the flood limits of the Hunter River and Wollombi Brook. Refer to the Project Surface Water Assessment for further information. Allocate existing and future water entitlements to the Project water takes to license take of water as necessary. United Wambo Project - Groundwater Impact Assessment (G1733) 100
AIP requirement Will uncertainty in the predicted inflows have a significant impact on the environment or other authorised water users? Items 14-16 must be addressed if so. Proponent response The proponents have secured a large landholding to the north-west and south of the mine. As shown in Section 7.1, the predicted extent of drawdown in groundwater levels due to the Project is largely within the extent of mine owned land. The model results indicate that the Project will contribute to drawdown at one private bore (GW060780) on land not owned by the proponent, resulting in the cumulative drawdown to exceed 2m during and post mining. This bore is not currently serviceable but it is understood to have been installed within the shallow weathered coal measures. The model predicts the bore would experience a maximum 6.7 m decline in groundwater levels, but will not go completely dry. It is therefore predicted the bore, if repaired, will remain usable, but with a reduced peak pumping capacity due to the predicted decline in water level. 14 Considered any potential for causing or enhancing hydraulic connections, and quantified the risk? 15 Quantified any other uncertainties in the groundwater or surface water impact modelling conducted for the activity? 16 Considered strategies for monitoring actual and reassessing any predicted take of water throughout the life of the Project, and how these requirements will be accounted for? The open cut mine plan has been designed to remain outside of the 150m from the edge of the nearest alluvium to ensure that impacts to the alluvial system are minimised as far as possible. A sensitivity and uncertainty analysis has been completed to identify parameters that demonstrate most substantial changes in the predictions. Ongoing monitoring and verification of modelling. Table 8-2 Determining water predictions AIP requirement 1 Addressed the minimum requirements found on page 27 of the AIP for the estimation of water quantities both during and following cessation of the proposed activity? Proponent response Predictions based on modelling made to address the requirements of page 27 of the AIP. Provided in Section 7 United Wambo Project - Groundwater Impact Assessment (G1733) 101
Table 8-3 Other requirements AIP requirement 1 Establishment of baseline groundwater conditions? 2 A strategy for complying with any water access rules? 3 Potential water level, quality or pressure drawdown impacts on nearby basic landholder rights water users? 4 Potential water level, quality or pressure drawdown impacts on nearby licensed water users in connected groundwater and surface water sources? 5 Potential water level, quality or pressure drawdown impacts on groundwater dependent ecosystems? 6 Potential for increased saline or contaminated water inflows to aquifers and highly connected river systems? 7 Potential to cause or enhance hydraulic connection between aquifers? 8 Potential for river bank instability, or high wall instability or failure to occur? 9 Details of the method for disposing of extracted activities (for CSG activities)? Proponent response Refer Section 5 and Appendix A. Water quality and level data has been collected at the Project Area since 2004 for some of the key groundwater units and tested for a selection of analytes. Extensive water quality and level data has been collected at neighbouring mines. No cease to pump rules have been established for the Lower Wollombi Brook water source. The Hunter Unregulated WSP requires a cease to pump rule be established by 2019. The Project has adequate water licences to comply with the requirements of the Hunter Unregulated and Alluvial Water Sharing Plan for the Hunter River and porous rock. One private bore predicted to be impacted >2 m One private bore is predicted to be impacted on land not owned by proponent Risk of drawdown at identified GDEs at two locations, as detailed in Section 7.1.7. Further details are provided in the Project Ecological Assessment No mining activity below the ground surface will occur within 200 m laterally from the top of high bank. Study identified the potential for the Project to increase salt loads post mining within the final void. However, the risk of changing the beneficial use of the water source was considered improbable. No open cut operations are not predicted to enhance hydraulic connection between aquifers. Refer to Surface Water Assessment N/A There are two levels of minimal impact considerations specified in the AIP. If the predicted impacts are less than the Level 1 minimal impact considerations, then these impacts will be considered as acceptable. Where the predicted impacts are greater than the Level 1 minimal impact considerations then the AIP requires additional studies to fully assess these predicted impacts. If this assessment shows that the predicted impacts do not prevent the long-term viability of the relevant water-dependent asset, then the impacts will be considered to be acceptable. The modelling indicates potential for drawdown in one private bore to exceed the Level 1 minimal impact considerations. As discussed in Section 7.1.6, the proponent will make-good any bores that have greater than 2m drawdown interference if it can be demonstrated that this interference is due to mining rather than to rainfall deficits. United Wambo Project - Groundwater Impact Assessment (G1733) 102
9 Compliance with Commonwealth government policy 9.1 EPBC Act Significant Impact on Water Resources Guidelines In June 2013 the Federal Government enacted changes to the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), to provide that water resources are a matter of national environmental significance in relation to coal seam gas and large coal mining development. This change is referred to as the water trigger. In December 2013, the Federal Department of Environment (DoE) released guidelines for proponents of coal seam gas and large coal mining projects to assess the potential for significant impacts on water resources. The guideline outlines a self-assessment process that assists proponents to identify if their project is likely to have a significant impact on water resources. This report considers the impact of the Project on groundwater resources, and if these impacts are significant according to the guidelines. It compares the predicted impacts against the DoE guidelines to determine if the Project could have a significant impact on water resources. It also considers the potential for cumulative impacts with other developments. It is important to note that coal mining will always impact the groundwater regime, as dewatering of the mine workings is essential to extract coal safely. However, we have interpreted the DoE guidelines (Commonwealth of Australia, 2013) to mean that this unavoidable impact is only considered significant where there is a consequence from this impact, i.e. that groundwater users or the environment are affected by changes in the quality or quantity of groundwater. The guidelines indicate that the Project must have a real or not remote chance or possibility that it will directly or indirectly result in a change to the hydrology or water quality of the water resource. This change must be of sufficient scale or intensity as to reduce the current or future utility of the water resource for third party users. Third party users can include environmental and other public benefit outcomes, or to create a material risk of such reduction in utility occurring. Furthermore, Whether or not an action is likely to have a significant impact depends upon the sensitivity, value, and quality of the water resource which is impacted, and upon the intensity, duration, magnitude and geographic extent of the impacts. 9.1.1 Water availability to users Eight bores are present within the zone of drawdown predicted by the model north to north-west of the mining area. One of the bores is apparently screened within the Quaternary alluvium, while seven are apparently within the shallow weathered overburden (siltstones and sandstones). Seven of these bores are located on land owned by the proponent, while one is located on a private property north of the Project Area. The modelling indicates potential for drawdown in one private bore to exceed 2m due to the Project. As discussed in Section 7.1.6, the proponent will make-good any bores that have greater than 2m drawdown interference if it can be demonstrated that this interference is due to mining rather than to rainfall deficits. 9.1.2 Water availability to the environment The numerical modelling indicates the depressurisation due to mining will reduce the flow of Permian groundwater to the alluvial aquifers of the Hunter River and Wollombi Brook. This will potentially result in lowering of groundwater levels around the fringes of the alluvium in some areas. Two potential GDEs are known to occur along Wollombi Brook in proximity to the Project. The cumulative impacts of the already approved mining has the potential to reduce alluvial groundwater levels below the base of alluvium, due to direct take with mining and reduced contributions from the underlying Permian coal measures. The proposed Project will create a small cumulative impact resulting in this occurring some one year earlier. United Wambo Project - Groundwater Impact Assessment (G1733) 103
9.1.3 Water quality It is proposed to emplace coarse and fine reject materials into the South Bates open cut during the years of open cut mining operations, in addition to approved TSFs at Homestead and Homestead Main. Modelling determined that the water levels within the final voids would recover to a quasi-equilibrium level of 20mAHD for United Open Cut and 55mAHD for Wambo Open Cut. This level is approximately 30m to 50m below the pre-mining groundwater level and means that the final void will act as a sink to groundwater flow preventing flow of water back into the groundwater systems. 9.1.4 Cumulative impacts Cumulative impacts in the region of the proposed Project are significant. Large mines targeting the same coal seams surround the proposed Project and all depressurise the Permian strata. Logically the drawdown that is most attributable to the proposed Project is that adjacent to the pit, with the influence of reducing with distance from United and Wambo. Previous sections that outline the cumulative impacts suggest the Project will only add a small to moderate water take to the already approved mines. 9.1.5 Avoidance or mitigation measures The mine plan avoids the flood plain and does not intersect existing alluvial aquifers. The impacts on the alluvial aquifers are therefore indirect, and occur through the depressurisation of the underlying Permian coal measures. Locating the mining outside the alluvial flood plain effectively mitigates the impact upon the alluvial aquifer and connected streams. The groundwater seepage to the mining areas cannot be prevented, and must be removed to ensure safe operating conditions within the mining areas. If the Project interferes with any private groundwater user possessing a water supply work, and mitigation measures are not feasible, make good measures with affected land owners will include: Ensuring the bore owner has access to a similar quantity and quality of water for the water bore s authorised purpose for example by: o bore enhancement by deepening the bore or improving its pumping capacity; o o constructing a new water bore; and providing a supply of an equivalent amount of water of a suitable quality by piping it from an alternative source. The make good agreements will also allow for the provision to the water bore owner of compensation (monetary or otherwise) for the bore s impaired capacity. United Wambo Project - Groundwater Impact Assessment (G1733) 104
9.1.6 Tabulated impacts Table 9-1 and Table 9-2 summarise the conclusions compared against DoE guidelines: Table 9-1 Summary of impacts to the hydrology of the water resource compared to the DoE guidelines Is there a substantial change to the hydrology of the water resource for: flow volume? flow timing? flow duration and frequency of water flows? recharge rates? aquifer pressure or pressure relationships between aquifers? groundwater table levels? groundwater/surface interactions? river/floodplain connectivity? inter-aquifer connectivity? coastal processes? large scale subsidence? other uses? state water resource plans? Comment Yes - flow to alluvial aquifer and baseflow in streams is reduced during mining. However, predicted reduction is comparatively low compared to cumulative impacts. Yes - impacts on aquifers will be more significant during dry seasons No - volumes of baseflow removed are relatively small Yes - recharge rates will potentially increase in the open cut mining area and recharge to alluvium and streams (baseflow contributions) will potentially decrease. Yes pressures will reduce in coal measures and alluvium during the mine life but recover post mining Yes - the groundwater table for the alluvium and coal measures will decline during mining but partially recover post mining Yes water table drawdown within the alluvium will reduce base flow to, or increase leakage from, the interconnected streams. No no impact as no mining proposed in flood plain. There is indirect connectivity through the Permian aquifer to the base of the alluvium and river system None due to the proposed open cut Not applicable None due to the proposed open cut No The proponents have a combined total entitlement of 370ML/year assuming full allocation under the Hunter Unregulated WSP. The groundwater model predicts that based on the Project and approved and foreseeable mine plans for Wambo and United, the maximum take from alluvium under the Hunter Unregulated WSP during mining is 260ML/year, and 84ML/year for the Hunter Regulated WSP, which are within the currently held entitlement. Of this, it is predicted that for the Project only, the maximum take from alluvium during mining under the Hunter Unregulated WSP is 40ML/year, and 58ML/year for the Hunter Regulated WSP. Combined entitlements held by the proponents for take from the Permian aquifer under the North Coast Fractured and Porous Rock WSP are 1947ML/year. The groundwater model predicts that up to 1778ML/year United Wambo Project - Groundwater Impact Assessment (G1733) 105
Is there a substantial change to the hydrology of the water resource for: Comment of groundwater within the Permian coal measures will be intercepted with the Project and currently approved operations at Wambo and United, which is within the currently held entitlement. Of this, it is predicted that for the Project only, the maximum take from the Permian coal measures during mining is 633ML/year. Following mining, predicted interception of groundwater under the Hunter Regulated WSP and North Coast Fractured and Porous Rock WSP are predicted to be lower than during active mining. However, interception of groundwater under the Hunter Unregulated WSP is predicted to peak post mining, to a maximum of 144ML/year (Project only). cumulative impact? Yes - extensive mining within the Wittingham Coal Measures and underlying Vane Sub-group surrounding the Project Area Table 9-2 Summary of impacts to the water quality of the water resource compared to the DoE guidelines Is there a substantial change in water quality of the water resource: Comment create risks to human or animal health or the condition of the natural environment? substantially reduce the amount of water available for human consumptive uses or for other uses dependent on water quality? cause persistent organic chemicals, heavy metals, salt or other potentially harmful substances to accumulate in the environment? results in worsening of local water quality where local water quality is superior to local or regional water quality objectives (i.e. ANZECC guidelines for Fresh and Marine Water Quality)? salt concentration/generation? cumulative impact? if significant impact on hydrology or water quality above, the likelihood of significant impacts to function and ecosystem integrity are to be assessed. The ecosystem function and integrity of a water resource includes the ecosystem components, processes and benefits/services that characterise the water resource No No Yes - salt will accumulate in the final void lake, which is predicted to act as a permanent sink. No - salt accumulating within the final voids will not be released to the groundwater systems due to hydraulic gradients into the pit lakes Yes - salt will accumulate in the final void lake No - the pit will form a sink at closure No no significant impacts identified due to Project, with the exception of predicted drawdown within one private bore of over 2m. United Wambo Project - Groundwater Impact Assessment (G1733) 106
10 Groundwater monitoring and management plan Management at Wambo occurs in accordance with the GWMP, which was prepared in consultation with DPI Water and approved in late 2015. Management at United occurs in accordance with the EMP, which was prepared in consultation with DPI Water and approved in December 2015. The existing groundwater monitoring programs will be continued and revised as required throughout the life of the Project. Additional monitoring bores and VWPs will also be installed as required, in order to ensure a long-term groundwater monitoring network in all key groundwater bearing units. A GWMP will be prepared for the Project in consultation with DPI Water. The updated GMP will include full details on how and when groundwater will be monitored across the Project Area and surrounds. Table 10-1 summarises and consolidates the groundwater monitoring programs for United and Wambo, and Figure 10-1 shows the bore locations. Initial proposed monitoring bores and VWP s have also been included with indicative locations for the purpose of the Project. Table 10-1 Proposed site monitoring network Bore ID Bore type Current status Easting Northing Surface (mahd) Bore depth (mbgl) Target unit Monitoring program P106 MB A 311518 6391084 60 - Alluvium 2m full suite 6 P109 MB A 311215 6390768 62 - Alluvium 2m full suite 6 P114 MB A 311205 6391288 62 - Alluvium 2m full suite 6 P116 MB A 311057 6391293 64 - Alluvium 2m full suite 6 GW13 MB A 313810 6388990 68 15 Alluvium/overburden 2m full suite 6 GW15 MB A 313164 6392807 61 17.4 Alluvium/overburden 2m full suite 6 GW16 MB A 306641 6396034 111 12.15 Alluvium/overburden 2m full suite 6 GW17 MB A 306895 6396048 110 14 Alluvium/overburden 2m* full suite 6 GW22 MB A 311335 6389535 91 54 Alluvium/overburden 2m full suite 6 P301 MB A 309311 6391425 89 - Alluvium/overburden 2m full suite 6 P315 MB A 309091 6391852 98 - Alluvium/overburden 2m full suite 6 P3 MB A 313412 6395006 57 51.02 Interburden 2m* full suite 6 P1 MB A 312199 6395840 86 37 Interburden 2m full suite 6 P11 MB A 312728 6395462 72 31 Interburden 2m full suite 6 GW08 MB A 311793 6392266 61 6.3 Alluvium 2m full suite 6 GW09 MB A 311643 6392563 62 6.2 Alluvium 2m full suite 6 P202 MB A 311859 6391330 59 - Overburden 2m full suite 6 P206 MB A 311772 6391293 59 - Overburden 2m full suite 6 GW02 MB A 309109 6389680 80 - Alluvium 2m full suite 6 GW11 MB A 309228 6389699 79 - Alluvium 2m full suite 6 United Wambo Project - Groundwater Impact Assessment (G1733) 107
Bore ID Bore type Current status Easting Northing Surface (mahd) Bore depth (mbgl) Target unit Monitoring program P16 MB A 313480 6394655 58 11.5 Colluvium 2m full suite 6 P20 MB A 313639 6394166 57 10.6 Colluvium 2m full suite 6 GW14 MB B 312478 6391358 65 18 Alluvium/overburden 2m full suite 6 GW21 MB B 308647 6393378 119 36 Alluvium/overburden 2m full suite 6 GW12 MB B 309841 6391056 99 12.1 Alluvium 2m full suite 6 P12 MB EX 313644 6394797 55 15 Alluvium 2m* full suite 6 13 Unnamed C Seam 19 Unnamed D Seam P33 VWP EX 313757 6394659 57 P34_35m VWP EX 313757 6393961 59 P35_16m VWP EX 313611 6395196 59 UG134 VWP EX 313782 6395767 61 UG135 VWP EX 313831 6396748 65 46.5 Unnamed E Seam 58 Blakefield Seam 113 Arrowfield Seam 35 Glen Munro Seam 68.5 Blakefield Seam 144 Bowfield Seam 16 Interburden 19 Interburden 51 Blakefield Seam 60 Blakefield Seam 112 Arrowfield Seam 45 Interburden 116 Interburden 175 Warkworth Seam 190 Mt. Arthur Seam 198 Piercefield Seam 215 Vaux Seam 50 Interburden 110 Warkworth Seam 129 Mt. Arthur Seam 146 Piercefield Seam 176 Vaux Seam 186 Broonie Seam SWL SWL SWL SWL SWL United Wambo Project - Groundwater Impact Assessment (G1733) 108
Bore ID Bore type Current status Easting Northing Surface (mahd) Bore depth (mbgl) Target unit Monitoring program UG139 VWP EX 306665 6395173 129 UG147 VWP EX 311245 6397207 108 UG166A VWP EX 306488 6398076 142 UG193 VWP EX 313757 6396090 58 UG194 VWP EX 312436 6397191 82 263 Unnamed D Seam 281 Unnamed E Seam 319 Interburden 329 Glen Munro Seam 375 Interburden 382 Arrowfield Seam 402 interburden 90 Glen Munro Seam 157 Interburden 209 Mt Arthur Seam 242 Piercefield Seam?? 249 Vaux Seam?? 260 Broonie Seam?? 130 Unnamed D Seam 153 Unnamed E Seam 183 Blakefield Seam 200 Glen Munro Seam 238 Arrowfield Seam 254 Bowfield Seam 260 Bowfield Seam 27 Glen Munro Seam 61 Arrowfield Seam 85 Bowfield Seam 160 Warkworth Seam 179.5 Piercefield Seam 210 Broonie Seam 20 Blakefield Seam 60 Interburden 100 Blakefield Seam 150 Interburden 190 Interburden SWL SWL SWL SWL SWL United Wambo Project - Groundwater Impact Assessment (G1733) 109
Bore ID Bore type Current status Easting Northing Surface (mahd) Bore depth (mbgl) Target unit Monitoring program UG196 VWP EX 312364 6397122 81 UG220 VWP EX 312522 6397233 82 UG224 VWP EX 313860 6396243 59 UG225 VWP EX 313214 6397095 69 210 Vaux Seam 45 Glen Munro Seam 80 Arrowfield Seam 110 Interburden 137 Interburden 160 Mt. Arthur Seam 230 Broonie Seam 52.5 Overburden 77 Arrowfield Seam 106 Interburden 110 Interburden 136 Warkworth Seam 152 Mt. Arthur Seam 207 Vaux Seam 163 Piercefield Seam 172 Interburden 191 Vaux Seam 23 Overburden 58.5 Arrowfield Seam 93.2 Bowfield Seam 100.5 Interburden 128 Mt. Arthur Seam 178 Vaux Seam SWL SWL SWL SWL P401 MB Proposed 313660 6395336 68 40 Overburden 3m* full suite 3 P402 MB Proposed 313660 6395336 68 120 Arrowfield Seam 3m* full suite 3 P404 MB Proposed 307023 6398634 97 40 Overburden 3m* full suite 3 P405 MB Proposed 307025 6398634 97 110 Arrowfield Seam 3m* full suite 3 P407 MB Proposed 312599 6392933 62 12 Alluvium 3m* full suite 3 P408 MB Proposed 307282 6399576 74 15 Alluvium 3m* full suite 3 P403 VWP Proposed 308565 6397958 133 30 Overburden 125 Arrowfield Seam SWL United Wambo Project - Groundwater Impact Assessment (G1733) 110
Bore ID Bore type Current status Easting Northing Surface (mahd) Bore depth (mbgl) Target unit Monitoring program P406 VWP Proposed 307681 6398872 88 205 Warkworth Seam 260 Vaux Seam 30 Overburden 110 Arrowfield Seam 135 Warkworth Seam 200 Vaux Seam SWL Notes: Coordinates are in MGA94 Zone 56 VWP vibrating wire piezometer MB monitoring bore A: bore currently monitored and assessed under GWMP, with individual trigger level for SWL, ph and EC B: bore currently monitored and assessed under GWMP, individual trigger to be established once sufficient data has been collected EX: existing monitoring bore with baseline data available Proposed: bore proposed to be installed and included in the monitoring network 2m: monitoring frequency every two months, measuring water level, field ph and EC (as is currently in GWMP) 3m: monitoring frequency every three months, measuring water level, field ph and EC Full suite conduct water quality testing every three (full suite 3 ) or six (full suite 6 ) months for full water quality suite, as detailed under Section 10 SWL: VWP sensor records daily water levels download results every six months * water levels also recorded with datalogger Monitoring of water levels and flows from key private bores within, and adjacent to the zone of depressurisation is also recommended, with consultation with adjacent landholders. The sites for the additional monitoring will be developed during the development of the GWMP, in consultation with DPI Water. United Wambo Project - Groundwater Impact Assessment (G1733) 111
10.1 Water level monitoring plan Groundwater monitoring at Wambo and United is undertaken in accordance GWMP and EMP, respectively. Currently manual groundwater level monitoring is conducted on a monthly to bi-monthly basis, in addition to daily readings recorded by the VWP dataloggers. Groundwater levels will continue to be monitored at the groundwater monitoring network locations discussed in Section 10. Ongoing monitoring will enable natural groundwater level fluctuations (such as responses to rainfall) to be distinguished from potential groundwater level impacts due to depressurisation resulting from proposed mining activities. Ongoing monitoring of groundwater levels will also be used to assess the extent and rate of depressurisation against model predictions. Yearly reporting of the water level results from the monitoring network will be included in the annual review. The annual review will also identify if any additional monitoring sites are required, or if optimisation of the existing monitoring sites should be undertaken. 10.2 Water quality monitoring plan Currently groundwater monitoring is conducted at Wambo and United on a monthly to bi-monthly basis for field water quality (EC and ph), and on an annual basis for more comprehensive water quality analysis at selected bores. The more comprehensive water quality analysis includes ph, electrical conductivity (EC), total dissolved solids (TDS), major ions (Ca, Cl, K, Na, Mg and SO 4), hardness, bicarbonate and nitrate. Groundwater quality sampling will continue in order to detect any changes in groundwater quality during and post mining. Where practicable, baseline data will be collected for nearby bores outside of the influence of active mining, and baseline data gaps addressed with the extensive water quality data available within the region, as presented in Appendix A. The full groundwater quality suite will expanded in order to include key analytes to determine any changes in beneficial groundwater use (i.e. livestock drinking water). The revised full suite will include: physio-chemical indicators ph, electrical conductivity, total dissolved solids; major ions calcium, fluoride, magnesium, potassium, sodium, chloride, sulphate; total alkalinity as CaCO 3, HCO 3, CO 3; and dissolved and total metals aluminium, arsenic, barium, boron, beryllium, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, molybdenum, nickel, selenium, strontium, silver, vanadium and zinc. Similar to the water level monitoring yearly reporting of the water quality results from the monitoring network should be included in the annual review. The annual review should consider if any additional monitoring sites are required, or if optimisation of the existing monitoring sites, frequency of sampling and analytical suite should be undertaken. The Water Management Plan should also consider the optimal sites for monitoring of groundwater quality during the life of the Project. 10.3 Trigger levels The aim of trigger levels is to provide mine management with an early warning mechanism that identifies water quality trends departing from historical values. The trigger levels will be derived for water quality parameters as part of the development of the Water Management Plan. This will include an analysis of historical pre-mining water quality data. United Wambo Project - Groundwater Impact Assessment (G1733) 113
10.3.1 Water quality triggers Statistical data for each monitoring bore such as maximum, minimum, average and standard deviation for key parameters such as TDS (EC), sulphate, and ph will be determined as part of the Water Management Plan. Once mining commences, monitoring results for each indicator parameter are plotted against time, with control limits of mean + standard deviation, mean + 2 standard deviations and mean + 3 standard deviations. Control criteria are set such that one observation above mean + 3 standard deviation, or two consecutive observations more than mean + 2 standard deviations, or five successive observations above mean + standard deviation would constitute a trigger or alarm. If there is a period of no alarms (e.g. after, say, 12 observations), the mean and standard deviations could be recalculated and the control lines adjusted to provide better precision. Figure 10-2 is an example of a control chart and when alarms are triggered. Figure 10-2 Example of a control chart (after DERM 2010) Should post mining water quality data for these selected key parameters reach the trigger levels, then further detailed analysis of all water quality data will occur. Should this analysis indicate trends not consistent with historical variation, then the mitigation process and strategies will be implemented. 10.3.2 Water level triggers The numerical modelling indicates that groundwater levels will fall within a zone around the proposed mining areas. An annual review should compare the measured groundwater levels in the monitoring bores with the model predicted levels. Judgement of an experienced hydrogeologist will determine when water levels deviate significantly from that predicted by the groundwater model, and determine the reason for this deviation. The review should consider the impact of mining, and other factors that could result in declining water levels including climatic conditions, rainfall recharge and pumping from private (and mine owned) bores. United Wambo Project - Groundwater Impact Assessment (G1733) 114
Water levels in bores located outside the predicted zone of influence will be assessed annually against a trigger level. If groundwater levels fall below the 5th percentile water level established from the preceding 24 months for a period of 30 days or over, a triggering event occurs. The trigger levels are based on a 7-day moving average water level. These triggers assume dataloggers are installed at all monitoring sites, with a six-hourly sample frequency, and regular downloads. Figure 10-3 shows an example of a bore, not from the Project area that falls below the calculated 5 th percentile level for over 30 days, and therefore triggers an investigation. As described above the investigation will consider the impact of mining, climatic conditions, rainfall recharge and pumping from private bores. It is important to understand that trigger values are not pass or fail compliance criteria, simply a trigger that further consideration needs to be given to the data. Figure 10-3 Example of a water level trigger event 10.4 Mine water seepage monitoring It is recommended that monitoring of mine water seepage be undertaken, particularly to identify seepage rates and quality. Samples should be collected of pumped seepage with the objective of providing an early indication of any mixing of shallow alluvial groundwaters with the Permian strata. Water quality analysis should be similar as for the groundwater monitoring bores. The seepage monitoring program should include: measurement of water pumped from the mining areas using flow meters or other suitable gauging apparatus; monitoring quality of water pumped from the mining areas (full water quality suite); correlation of rainfall records (and catchments) with mining area seepage records so groundwater and surface water can be separated; and monitoring of coal moisture content. United Wambo Project - Groundwater Impact Assessment (G1733) 115