groundwater resources - new hope group 06... · the review of other background data available on...

New Acland Coal Mine Stage 3 Expansion Project – Environmental Impact Statement PAGE 6-1

6. Groundwater Resources This Chapter describes the groundwater resources that may be impacted by the Project and identifies the measures required for the mitigation of potential impacts.

The methodology undertaken for the assessment of groundwater resources included:

the review of geological, hydrogeological and groundwater quality data collected for the Mine;

the review of other background data available on local hydrogeology and groundwater use;

the installation of four production and 11 observation bores to characterise the local hydrogeology around the Project site;

the undertaking of aquifer pump testing to determine aquifer parameters (transmissivity and storativity);

the formulation of a hydrogeological conceptual model to serve as the basis for a numerical model;

the undertaking of numerical modelling to estimate likely impacts of the Project on groundwater levels; and

the assessment of potential impacts and mitigation measures.

The following Sections describe the regulatory framework for the Project with respect to groundwater resources and the results of the assessment undertaken to determine the impacts on groundwater resources.

6.1. Regulatory Framework

6.1.1. Queensland Legislation

Groundwater use and management in Queensland is regulated under the W Act and the EPP (Water).

In Queensland, a number of subartesian areas have been declared under the W Act. This means that a water licence is required to take or interfere with subartesian water and a development permit is required to construct or install works that take subartesian water. NAC currently extract groundwater under water licences, refer to Section 6.2.5.

The EPP (Water) aims to protect Queensland’s environments by providing a framework to:

a) identify environmental values for Queensland waters;

b) decide and state water quality guidelines and objectives to enhance or protect the environmental values;

c) make consistent and equitable decisions about Queensland waters that promote efficient use of resources and best practice environmental management; and

d) involve the community through consultation and education and promoting community responsibility.


The values identified in the EPP (Water) under Section 7 are as follows.

The “environmental values” of waters to be enhanced or protected under this policy include:

a) for a water in schedule 1, column 1; and

b) for another water – the qualities in sub-section (2).

The Project site is not listed in schedule 1, column 1 therefore, for the Project, the environmental values (EVs) for groundwater are based on the qualities identified in sub-section (2) which are described as:

Aquatic Ecosystems;

Regional, Agricultural and Industrial Use; and

Drinking Water (Potable).

Within the Project site, groundwater resources are currently used for industrial, agricultural (including livestock watering) and potable use. However, groundwater resources within the Project site are unlikely to contribute any significant baseflow in creeks or aquatic ecosystems within the Project site. Chapter 8 Aquatic Ecology describes the aquatic ecology within the Project site.

6.1.2. Water Resource (Great Artesian Basin) Plan 2006

The Water Resource (Great Artesian Basin) Plan 2006, which is a subordinate regulation to the W Act, covers the management of all artesian and subartesian water in the Clarence-Moreton Management Area. This coverage includes management of the Walloon Coal Measures aquifer, Marburg Sandstone aquifer and Helidon Sandstone aquifer.

6.1.3. Environmental Authority

The Mine operates under an EA in accordance with the EP Act. The EA includes requirements for the monitoring of groundwater levels and quality. These requirements are discussed in Section 6.2.6.

For compliance purposes, groundwater level fluctuations are compared with groundwater levels observed in the reference bores. If the cause is not related to the licensed extraction from the aquifer, this change in level is required to be reported to the DERM.

Under the current EA, NAC has recently received approval from the DERM to allow the use of site specific groundwater quality guidelines for the Mine. These site specific guidelines were developed from a study conducted over a number of years.

6.1.4. National Water Commission

The National Water Commission regional water resource assessment identifies the Project site as being located within the Great Artesian Basin (GAB) Groundwater Management Unit (GMU). The size of the GAB GMU in Queensland is 1 211 km².

In the GAB GMU, groundwater users are required to hold entitlements for groundwater use for irrigation, urban supply, commercial / industrial, farm dams, forestry, floodplain harvesting, drought supply, greywater use, effluent recycling, and aquifer storage and recovery.


Capping of resource extraction volumes is an accepted way to manage overexploitation of groundwater. In the GAB GMU, a water resource cap has been placed on groundwater usage which only applies to irrigation, urban supply, commercial / industrial, forestry and drought supply. The water resource cap does not include stock and domestic supplies, mining / oil and gas, greywater use, effluent recycling, and aquifer storage and recovery.

6.2. Existing Environment

6.2.1. Project Location

The Project site is situated in the western portion of the Clarence-Moreton Basin. The Walloon Coal Measures within the Clarence-Moreton Basin underlie the Project site and regionally contain an estimated coal resource of over 800 million tonnes.

6.2.2. Hydrology and Landforms

The Project site is located in undulating terrain that spans two catchments. The majority of the Project site drains to Lagoon Creek. Both Lagoon Creek and Doctors Creek flow into Oakey Creek which is part of the larger Condamine-Balonne River Catchment.

The hydrology of the Project site is discussed in more detail in Chapter 5 Surface Water Resources.

6.2.3. Geology

This Section outlines the geology of the Project site.

Regional Geology

The Project site lies within the Cecil Plains Sub-Basin which is located within the western portion of the Clarence-Moreton Basin. In Queensland, the Clarence-Moreton Basin merges with the Surat Basin. The Kumbarilla Ridge is a basement high consisting of the Upper Devonian to Upper Carboniferous Texas beds and separates the Cecil Plains Sub-Basin from the Surat Basin. The Clarence-Moreton Basin represents an eastern portion of the Mesozoic GAB. In this portion, the GAB comprises the Marburg Sandstone and Helidon Sandstone.

The economic coal-bearing sediments of the Surat and Clarence-Moreton Basin occur in the Walloon Coal Measures. The Walloon Coal Measures are Middle to Upper Jurassic in Age and are a part of the Injune Creek Group. Although the Kumbarilla Ridge is considered to structurally separate the Clarence-Moreton Basin from the Surat Basin, the Walloon Coal Measures of the Clarence-Moreton Basin are laterally continuous with those of the Surat Basin.

The Injune Creek Group cannot be identified as a distinct unit in the western Clarence-Moreton Basin. However it is broken up into a productive, coal bearing lower unit - the Walloon Coal Measures and a barren upper unit - the Kumbarilla Beds.

Within the Project site, the major coal bearing unit within the Walloon Coal Measures is referred to as the Acland Sequence. The Acland Sequence occurs in the lower coal bearing unit (Taroom Coal Measures equivalent) of the Walloon Coal Measures.


Tertiary Basalts unconformably overlie the Walloon Coal Measures in some areas of the Project site. The Tertiary age was a period of intense volcanic activity during which the eroded Marburg Formation and Walloon Coal Measures palaeo-surface was covered with basalt flows. Basalt filled palaeo-channels occur within the north western and southern margins of the Glen Roslyn Deposits. The Tertiary and Quaternary age alluvium are associated with present day natural drainage channels within the region.

The geology of the region is summarised in Table 6-1.

Table 6-1 Geology of the Region

Age Geological Unit Moreton Basin

Surat Basin Lithology Acland Area

Quaternary - - - Alluvium: sand, clay, gravel

Tertiary Main Range Volcanics - - Olivine basalt, tuff, agglomerate

Upper Jurassic

Injune Creek Group

Kumbarilla Beds

- - Claystone, siltstone, sandstone, minor coal

Middle Jurassic

Walloon Coal Measures

- Springbok Sandstone

Claystone, siltstone, sandstone, coal

Juandah Coal Measures

Kogan

- Macallister - Wonkers Tangalooma Sandstone

Waipanna

Taroom Coal Measures Acland - Balgowan

- Eurombah Formation - - Lower Jurassic

Bundamba Group Marburg Sandstone Hutton Sandstone Sandstone, minor siltstone claystone and coal

Evergreen Formation - Interbedded shale and sandstone

Helidon Sandstone - Interbedded shale and sandstone, quartz sandstone

Carboniferous to Devonian

Texas Beds - - Greywacke, conglomerate, siltstone, mudstone, slate, local phyllite, chert, basalt, limestone and rare tuff

Notes: 1. The age of geological units shown is from most recent (Quaternary) to oldest (Carboniferous to Devonian) in formation. Source: New Hope Coal Life of Mine Plan 2008.


Local Geology

The local geology comprises the following formations which are described below.

Quaternary Deposits

Quaternary deposits consist of recent alluvium deposited by creeks and rivers. Within the Project site, these deposits are likely to occur in association with the Lagoon Creek catchment.

Tertiary Basalt

The Tertiary Basalt unconformably overlies the Walloon Coal Measures in several localities within the Project site. Remnants of Tertiary age basalt flows from the hill tops within the Project site occur as low lying horizontal continuous flows. The presence of weathered basalt below fresh basalt, in combination with relict soil profiles and sedimentary layers, indicate that there has been a succession of basalt flows within the Project site. Two to three distinct flows have been observed during drilling investigations.

Boreholes show that the basalt thickness is variable. Up to 25 m of basalt was recorded in borehole AC2 in the Manning Vale resource area. In excess of 30 m of basalt was logged in the then DNRW boreholes (NS 26, 27, 28, 33, 42 and 44) located on or near the basalt ridge which separates the Mine’s Centre Pit from the former Colliery. Some 33.6 m of basalt was intersected in borehole AC515 and 90.2 m in AC480. AC515 and AC480 are located between the Mine’s Centre and South Pits and west of the North Pit respectively.

The unaltered basalts are black in colour and microcrystalline. Some basalt is porphyritic containing olivine phenocrysts. Vesicular and amygdaloidal basalts are common. Vesicles are often partially or completely infilled with zeolites, calcite and clay minerals. The base of the basalt flows is typically vesicular and the vesicles are infilled with zeolites. Products of the basalts decomposition are red clay in which magnesite is common.

Walloon Coal Measures

The three major coal intervals identified within the Lower Walloon Coal Measures are the Waipanna, Acland-Sabine, and Balgowan. NAC mines the Acland-Sabine sequence within the Lower Walloon Coal Measures. Chapter 3 Project Description outlines the mine plan for the Project.

The Mine currently extracts coal from the Acland-Sabine interval which contains up to 18 m of banded coal. The Acland-Sabine interval contains six seam groups. From the top to bottom these are nominated as A to F. Each seam group contains up to 10 seam plies. Seam plies are discrete layers of coal within a seam group. In total, the Acland-Sabine interval has 47 seam plies. The average thickness of an individual seam pile is 0.23 m.

The Waipanna interval contains six seam groups which contain 53 seam plies. The Balgowan interval contains seven seam groups which contain 21 seam plies.

The regional dip of the Walloon Coal Measures is one to three degrees south-southwest. Local variations of both dip and strike occur due to both folding and faulting. The general geological structure of the Project site can best be described as a fault modified south westerly plunging syncline, with the fold axis centred on the Lagoon Creek drainage structure.


Faulting is known to have occurred from underground mines in the Acland area and has also been interpreted from drilling results. Faulting is developed along two main trends, northeast-southwest and northwest-southeast. Folding has been interpreted from photogeological interpretation, regional drilling and geological interpretation of the drilling results elsewhere in the Clarence-Moreton Basin.

Marburg Sandstone

The Marburg Sandstone is up to 500 m thick and regionally dips to the southwest. The Marburg Sandstone is made up of poorly sorted, coarse to medium-grained, feldspathic subliable sandstone and fine-grained, well sorted quartzose sandstone. Minor carbonaceous siltstone, mudstone, coal and rare pebble conglomerate also occur within the Marburg Sandstone.

Evergreen Formation

The Evergreen Formation is a part of the Bundamba Group which was deposited during the Jurassic Age. The Evergreen Formation has been described on the 1:250 000 Geology Map of Ipswich (Geological Survey of Queensland, 1980) as consisting of sandstone, siltstone, shale, mudstone and oolitic ironstone.

Helidon Sandstone

The Helidon Sandstone is up to 170 m thick and is extensive within the Cecil Plains Sub-Basin. This sandstone crops out near the township of Helidon. This unit is divided into two sections, an upper section of interbedded shale and sandstone with kaolinitic clays and a lower section of fine to very coarse quartz sandstone.

Texas Beds

The Upper Carboniferous Texas Beds consist of greywacke, conglomerate, siltstone, mudstone, slate, local phyllite, chert, basalt, limestone and rare tuff. Generally, the Texas Beds are rich in felsic volcanic detritus which were derived from an active magmatic arc to the west. The Texas Beds are low grade, regionally metamorphosed and variably deformed.

6.2.4. Hydrogeology

The Section provides a summary of the five aquifers which occur within the Project site. Section 6.2.13 provides further information on these aquifers and discusses aquifer parameters including depth to groundwater, aquifer thickness, transmissivity, storativity and hydraulic conductivity.

Quaternary Alluvial Aquifer

The Quaternary Alluvial aquifer is located within the Quaternary Alluvium which consists of clay, silt, sand and gravel deposited by creeks and rivers. The Quaternary Alluvium is limited in extent. The nearest Alluvium with significant groundwater supplies is associated with Oakey Creek approximately 15 km southeast of Acland Township. This aquifer may exist in association with Lagoon Creek.

Tertiary Basalt Aquifer

The Tertiary Basalt aquifer consists of olivine basalts and varies in thickness from 1 m to 90 m. The Tertiary Basalt aquifer is interbedded with clay which has the potential to act as an aquitard within the Tertiary Basalt. There is a minor outcrop of the Tertiary Basalt aquifer in the northern section of the Project site.


The Mine currently draws groundwater from the Tertiary Basalt aquifer. This potable water supply is currently covered under a license for 160 ML/year. Groundwater extraction from the Tertiary Basalt aquifer is also undertaken by nearby private groundwater users.

Walloon Coal Measures Aquifer

The Walloon Coal Measures aquifer consists of shale, siltstone, carbonaceous mudstone, minor sandstone and coal layers. This geological unit outcrops over much of the Project site with the coal seams being the principal conduit for groundwater.

The Mine uses groundwater which flows into the mine pit from the Walloon Coal Measures aquifer. The inflow is used for a variety of industrial purposes. Neighbouring farm properties also use groundwater from the Walloon Coal Measures.

Marburg Sandstone Aquifer

The Marburg Sandstone aquifer consists of sandstone, minor coal and conglomerate rock types. These water bearing units are interbedded with less permeable rock units such as mudstone, siltstone and shale.

The Marburg Sandstone aquifer is a confined aquifer which occurs at a depth of approximately 150 mBGL within the Project site. Aquitards within the Walloon Coal Measures act as effective confining layers for the Marburg Sandstone aquifer.

The Mine currently extracts groundwater for industrial and potable use from the Marburg Sandstone aquifer and has an allocation of 300 ML/year. The Mine and other nearby private groundwater users are the main sources of groundwater extraction from the Marburg Sandstone aquifer.

Helidon Sandstone Aquifer

The Helidon Sandstone aquifer is the deepest aquifer underlying the Project site and underlies the Marburg Sandstone Aquifer. This aquifer is extensive within the Cecil Plains Sub-Basin and has been divided into two sub-aquifers. The upper aquifer consists of interbedded shale and sandstone. The lower section is made up of fine to very coarse quartz sandstone. Groundwater occurs within a confined, primary porosity aquifer and is isolated from the overlying aquifers by the relatively impermeable Evergreen Formation.

The Mine currently extracts groundwater from the Helidon Sandstone aquifer for industrial use and has an allocation of 710 ML/year. The Mine and other nearby private groundwater users are the main sources of groundwater extraction from the Helidon Sandstone aquifer.

A decline in groundwater levels in the Helidon Sandstone aquifer has been observed in a monitoring bore close to the Mine. Groundwater extraction from the Mine is the most likely cause of the decline in groundwater levels.

6.2.5. Groundwater Use Groundwater Use adjacent to the Mine

A facility survey of the DERM database was conducted in relation to the Project site. This survey identified a total of 321 registered groundwater bores within a 3 km radius of the Project site. The location of these bores is shown in Figure 6-1. The status of these groundwater bores is shown in Table 6-2.


Table 6-2 Status of DERM groundwater bores

Existing Abandoned or Destroyed Proposed

Number of Bores 287 22 12

A review was undertaken of the available aquifer details for the identified bores. Only 131 bores had information regarding which aquifer the bore extracts groundwater from. Table 6-3 provides a summary of the bores which have been installed in each aquifer.

Table 6-3 Number of Bores Installed in Each Aquifer

Quaternary Alluvial Tertiary Basalt Walloon Coal Measures

Marburg Sandstone

Number of Bores 5 24 88 14

The available bore data was further reviewed to identify groundwater quality, yield and standing water levels (SWL) in each aquifer for these groundwater users. This information is summarised in Table 6-4.

Table 6-4 Groundwater Quality, Yield and SWL in Each Aquifer

Registration Number Aquifer Quality Yield (L/sec) SWL (mBGL)

86723 Alluvium Potable 6.1 13 94996 Tertiary Basalt Brackish 1.9 45 107255 Tertiary Basalt Potable 0.52 11 107357 Tertiary Basalt Potable 2.05 Not Available 83742 Walloon Coal Measures Potable 2.15 48.7 87379 Walloon Coal Measures Potable 3.9 21 94873 Walloon Coal Measures Potable 1.84 28.7 94887 Walloon Coal Measures Not Available 0.8 30 107011 Walloon Coal Measures Brackish 1.89 31.6 107083 Walloon Coal Measures Potable 3.31 103 107349 Walloon Coal Measures Not Available- 0.48 Not Available 107364 Walloon Coal Measures Potable 0.36 Not Available 107882 Walloon Coal Measures Not Available Not Available 22.2 107883 Walloon Coal Measures Salty Not Available 21.5 107884 Walloon Coal Measures Salty Not Available 23 119397 Walloon Coal Measures Brackish 2.4 20.6 119420 Walloon Coal Measures Brackish 1.51 52 87941 Marburg Sandstone Potable 3.16 49.6 94298 Marburg Sandstone Not Available 0.44 Not Available 94997 Marburg Sandstone Potable 3.66 121 107121 Marburg Sandstone Potable 5.37 Not Available

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NEW ACLAND STAGE 3COAL MINE EXPANSION

Location of DERM Registered GroundwaterBores Existing Within a 3km Radius

FIGURE 6-1

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LEGEND# Locality!( DNRW Groundwater Bore

Road3km RadiusPit Boundary

CadastreExisting Mining LeaseStage 3 Mining Lease ApplicationStage 3 MDL

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Only one bore (Registration Number 86723) constructed in the alluvium contains information for this aquifer. Groundwater in the alluvial aquifer is shallow in depth (13 mBGL) and is potable. Groundwater yield in the alluvial aquifer is moderate to high, with data indicating a yield of 6.1 L/sec.

Investigations undertaken during the Stage 2 EIS show that groundwater use for stock and domestic purposes occurs locally in the Tertiary Basalt aquifer. There is a concentration of bores in the Tertiary Basalt aquifer to the west of the Project site. The DERM survey data shows that groundwater in the Tertiary Basalt aquifer has levels which range from 11 m to 45 mBGL and is generally of potable quality. The groundwater yield from these bores is low, with yield ranging from 0.5 L/sec to 2 L/sec.

The Walloon Coal Measures aquifer supplies both potable water and brackish water for livestock use. Groundwater levels in this aquifer range from 20 m to 103 mBGL. The DERM survey data suggests that this aquifer generally produces yields which range from 0.4 L/sec to 4 L/sec. All neighbouring farm properties surveyed have groundwater extraction bores which mainly extract water from the Balgowan interval.

Within the Walloon Coal Measures, the Acland-Sabine interval which is mined by NAC is hydraulically separate from the underlying Balgowan interval. In the vicinity of the Project site, the Balgowan interval is approximately 30 m deeper than the lowest Acland-Sabine seam and is separated by clay-matrix sandstones which lack primary porosity and act as an aquitard between the two coal sequences.

Stock watering and municipal supplies are extracted from the Marburg Sandstone aquifer. The majority of the Marburg bores are to the east of the Project site. Groundwater levels in this aquifer ranges from 49.6 mBGL to 121 mBGL. The DERM survey data show that this aquifer is generally of potable quality and produces yields ranging from 0.44 L/sec to 5.37 L/sec.

Currently, only AMH Beef City and the Mine extract groundwater from the Helidon Sandstone at comparable rates.

Groundwater Use at the Mine

The Mine’s main operational water supply is from groundwater sources supplemented by surface water captured in environmental dams and mine pit inflows. NAC currently holds water licenses to extract groundwater from the Cecil Plains Sub-Basin of the western section of the Clarence-Moreton Basin. Table 6-5 summarises the groundwater allocations currently in use at the Mine.

Table 6-5 Groundwater Use at the Mine

Aquifer Licence No. Current Allocation (ML/year) Use

Helidon Sandstone 172533 710 Industrial / Potable Marburg Sandstone 174733 and 403871 300 Industrial / Potable Tertiary Basalt 189547 160 Potable

The locations of the Mine’s extraction bores are shown in Figure 6-2.

Once operating, the WWRF Pipeline will remove the Mine’s reliance on the GAB’s Helidon and Marburg Sandstone aquifers for industrial use.

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6.2.6. Existing Mine Groundwater Monitoring

A groundwater monitoring program is currently in place for the Mine in accordance with the conditions outlined in NAC’s EA.

The groundwater monitoring program outlined in NAC’s EA is summarised in Table 6-6. The locations of the groundwater monitoring bores for the Mine are shown in Figure 6-3.

Table 6-6 Groundwater Monitoring Program defined by NAC’s EA

Site ID Type Aquifer Groundwater Level Monitoring Frequency

WQ1 Monitoring Frequency

WQ2 Monitoring Frequency

P2007 Reference Walloon Coal Measures Monthly Half Yearly Quarterly P2008b Reference Tertiary Basalt Monthly Half Yearly Quarterly 15Pc Compliance Walloon Coal Measures Monthly Half Yearly Quarterly 16Pc Compliance Walloon Coal Measures Monthly Half Yearly Quarterly 17Pc Compliance Walloon Coal Measures Monthly Half Yearly Quarterly 18Pc Compliance Walloon Coal Measures Monthly Half Yearly Quarterly 25Pc Compliance Walloon Coal Measures Monthly Half Yearly Quarterly 26Pc Compliance Walloon Coal Measures Monthly Half Yearly Quarterly 27Pc Compliance Walloon Coal Measures Monthly Half Yearly Quarterly 28Pc Compliance Walloon Coal Measures Monthly Half Yearly Quarterly 843b Compliance Tertiary Basalt Monthly Half Yearly Quarterly 848c Compliance Walloon Coal Measures Monthly Half Yearly Quarterly

Notes: 1. WQ1 = Aluminium (Al), Arsenic (As), Selenium (Se), Copper (Cu), Fluorine (F), Iron (F), Total Nitrogen (Total N), Manganese (Mn); Calcium (Ca), Chloride (Cl), Potassium (K), Magnesium (Mg), Sodium (Na), Sulphate (SO4), Bicarbonate (HCO3), Carbonate (CO3), Total Dissolved Solids (TDS). 2. WQ2 = Electrical Conductivity (EC); Acidity/Alkalinity (pH).

Groundwater quality monitoring from compliance bores is conducted on a half yearly and quarterly basis. The parameters monitored are shown in the notes at the end of Table 6-6. Section 6.2.10 provides a summary of the groundwater quality monitoring results for the Mine.

Groundwater level monitoring from compliance bores is conducted on a monthly basis. Groundwater levels which have been recorded at the Mine are summarised in Section 6.2.8.

In addition to the EA compliance monitoring sites, NAC undertakes groundwater level monitoring from additional groundwater monitoring bores. These are summarised in Table 6-7.


Table 6-7 Additional Groundwater Monitoring Sites

Site ID Type Aquifer Groundwater Level Monitoring Frequency

18Pb Additional Tertiary Basalt Monthly P2008c (tape) Additional Walloon Coal Measures Monthly 10Pb Additional Tertiary Basalt Quarterly 13Pb Additional Tertiary Basalt Quarterly 21Phs Additional Marburg Sandstone Quarterly 24Phs Additional Marburg Sandstone Quarterly 30P Additional Not Specified* Monthly 31P Additional Tertiary Basalt Monthly 32P Additional Tertiary Basalt Monthly 35Pb Additional Tertiary Basalt Quarterly 40Pc Additional Walloon Coal Measures Quarterly 41Phs Additional Marburg Sandstone Quarterly 42Pc Additional Walloon Coal Measures Quarterly 48Phs Additional Marburg Sandstone Quarterly 78Pcl Additional Clays (Alluvium) Monthly 79Pcl Additional Clays (Alluvium) Monthly 80Pcl Additional Clays (Alluvium) Monthly 81Pc Additional Walloon Coal Measures Monthly 82Pc Additional Walloon Coal Measures Monthly 83Pc Additional Walloon Coal Measures Monthly 84Pb Additional Tertiary Basalt Monthly

Note: * aquifer details for this bore have not been specified.

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Mine Groundwater MonitoringBore Locations

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LEGEND# Locality") Water Monitoring Location





6.2.7. Project Baseline Groundwater Monitoring

The purpose of the Project baseline groundwater monitoring was to expand the monitoring undertaken for the Mine to include the Project site. This expansion involved the installation of 15 groundwater monitoring bores at the Project site, which comprised four production bores and 11 observation bores. The locations of the additional groundwater monitoring bores are shown in Figure 6-4.

A summary of the bore details is provided in Table 6-8. Logs for the bores are provided in Appendix G.1

Table 6-8 Summary of Monitoring Bore Details

Bore ID Type Screen From (m) Screen To (m) Screened Aquifer

112PGC Production 35.5 41.25 Walloon Coal Measures 113PGCA Observation 27 34 Walloon Coal Measures 113PGCB Observation 43 50 Walloon Coal Measures 121WB Production 27 34 Walloon Coal Measures 117PGC Observation 73.5 83.5 Walloon Coal Measures 118P Observation 49 56 Walloon Coal Measures 120WB Production 73.5 83.5 Walloon Coal Measures 111PGC upper Observation 28.5 33.5 Walloon Coal Measures 111PGC lower Observation 39.5 45.5 Walloon Coal Measures 110PGC Production 39.5 54.5 Walloon Coal Measures 109P Observation 98 102 Tertiary Basalt 116P Observation 42 58 Walloon Coal Measures 119PGC Observation 28.3 45.3 Walloon Coal Measures 114P Observation 71 80 Walloon Coal Measures 115P Observation ABANDONED - -

Baseline groundwater monitoring was undertaken to assess the following attributes within the Walloon Coal Measures aquifer at the Project site:

groundwater levels;

groundwater quality; and

aquifer parameters including transmissivity, storativity and hydraulic conductivity.

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FIGURE 6-4

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6.2.8. Groundwater Levels Groundwater Levels at the Mine

Groundwater level monitoring has been undertaken on a monthly basis since 2001. These bores provide groundwater levels in various aquifers, in particular the Tertiary Basalt and Walloon Coal Measures aquifers. Reduced water levels (mAHD) for the groundwater monitoring sites within the Walloon Coal Measures are shown in Figure 6-5.

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Groundwater Levels (mAHD) in the Walloon Coal Measures

15Pc 16Pc 17Pc 18Pc 27Pc 28Pc 40Pc

42Pc 81Pc 82Pc 83Pc 848c P2007 P2008c

Figure 6-5 Standing Water Levels (mAHD) within the Walloon Coal Measures

There are 14 monitoring bores in place to monitor groundwater level changes in the Walloon Coal Measures aquifer. Monitoring commenced in early 2002 in most bores and is ongoing. The above figure shows that the commencement of groundwater monitoring in groundwater bores 28Pc, 18Pc, 27Pc, P2007, 15Pc and P2008c occurred at a later date in comparison to the remaining bores.

Groundwater level monitoring is normally undertaken on a monthly basis as required by the EA. A number of general groundwater monitoring bores not used for compliance purposes are monitored on a quarterly basis.

Monitoring bores completed within the Walloon Coal Measures aquifer show only minor fluctuations in water levels with no discernable trend with the exception of bores 27Pc and 42Pc.

Bore 27Pc showed little change with time until late 2006 when a rapid decline in water level of about 20 m was recorded which persisted until late 2007 when the water level recovered by approximately 5 m to 6 m.


Based on the available data, this response is likely to be due to the drawdown of groundwater from the Walloon Coal Measures by the Mine for dewatering.

Bore 42Pc demonstrated apparent pumping induced fluctuation from early 2002 to mid 2003 then stabilised for much of the remaining monitoring period to late 2007.

Figure 6-6 shows the groundwater levels (mAHD) for the groundwater monitoring sites within the Tertiary Basalts.

350

360

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380

390

400

410

420

430

440

450Groundwater Levels (mAHD) in the Tertiary Basalts

10Pb 13Pb 18Pb 31P 32P 35Pb 84Pb 843b P2008b

Figure 6-6 Standing Water Levels (mAHD) within the Tertiary Basalts

There are nine monitoring bores in place to monitor groundwater level changes in the Tertiary Basalts aquifer. Monitoring commenced in early 2002 in most bores and is ongoing. Figure 6-6 shows that the commencement of groundwater monitoring in groundwater bores 31P and 18Pb occurred at a later date in comparison to the remaining bores.

As previously explained, groundwater level monitoring is normally undertaken on a monthly basis as required by the EA. A number of general groundwater monitoring bores not used for compliance purposes are monitored on a quarterly basis.

Site ID bores 13Pb, 31P, 32P and 35Pb exhibited slight or no change during the monitoring period. The groundwater levels for bore 18Pb shows a slight upward trend from late 2006.


Bores 84Pb and P2008b display a drawdown of about 15 m from mid 2004 to late 2006. This change is indicative of sustained pumping from the Mine’s Stage 2 production bore 8WB in the Tertiary Basalt aquifer.

The rise in water level in bore 10Pb of about 10 m in mid 2007 may be caused by measurement error or a change in the pumping regime in the vicinity of this monitoring bore.

Groundwater Levels for the Project site

Groundwater level monitoring results for the Project site are shown in Table 6-9. The majority of bores were screened in the Walloon Coal Measures except bore 109P which was screened in the Tertiary Basalt.

Table 6-9 Groundwater Level Results for Recently Constructed Bores

Groundwater Bore Production/ Observation Bore Depth to Water Level (mTOC)

121WB Production 10.31 113PGC A Observation 10.82 113PGC B Observation 10.85 118P Observation 13.11 117PGC Observation 15.63 109P Observation 28.23 111PGC lower Observation 22.18 111PGC upper Observation 20.79 119PGC Observation 18.62 116P Observation 38.10 114P Observation Dry 110PGC Production Dry 112PGC Production 45.87 (muddy)

Note: mTOC is depth from the top of the borehole casing to groundwater in metres.

The depth to groundwater within the Project site ranges from 10.3 mTOC to 45.9 mTOC in the Walloon Coal Measures. The depth to groundwater observed in the bore constructed in the Tertiary Basalt was 28.2 mTOC.

6.2.9. Groundwater Movement

The movement of groundwater often mirrors topographic surface terrain in a more subdued manner. Figure 6-7 shows the groundwater levels in the Walloon Coal Measures aquifer in the Project site. The data is based on data collected from monitoring bores installed for the Project and historical data from the Mine.

The groundwater level data indicates that the overall direction of groundwater flow in the Walloon Coal Measures aquifer within the Project site is to the south. This direction of flow is consistent with the topographic surface and the downward direction of the Walloon Coal Measures to the south-southwest. As there is no groundwater monitoring bores within the mine pit, the groundwater level data does not show local drawdown influences as a result of mine pit dewatering. Notwithstanding this, the data does indicate that the Mine is currently not having a significant drawdown impact on groundwater levels in the Walloon Coal Measures within the Project site.

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FIGURE 6-7

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LEGEND!( Exisiting Monitoring Bore

Groundwater Level Contour (mAHD)Direction of Groundwater FlowPit Boundary

Existing Mining LeaseStage 3 Mining LeaseApplicationStage 3 MDL

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6.2.10. Surface Water and Groundwater Interaction

Based on the studies undertaken as part of Stage 2 EIS, streams are assessed as being ephemeral and there are no perennial water holes present within the Project site. A comparison of groundwater levels and stream bed levels indicates that groundwater does not contribute to surface water flow within these creeks and streams. After significant rainfall events which result in runoff to surface water drainage lines, it is anticipated that a component of surface flow will infiltrate and a small amount will reach the Quaternary Alluvial aquifer which is generally several tens of metres below the stream beds. The majority of the infiltrated water is likely to be lost by direct evapotranspiration along the stream banks.

6.2.11. Groundwater Quality

The following sub-sections provide a summary of the water quality data collected for the Mine and the Project site. The data used in this assessment includes existing information (Waste Solutions, 2008) and sampling undertaken for this assessment. Appendix G.2 contains the sample location data sheet. The existing data has been compared to the following guidelines based on the EVs of the Project site. The guidelines include:

ANZECC Guidelines; and

Australian Drinking Water Guidelines 2004 (ADW Guidelines).

Groundwater results were not compared to ANZECC Guidelines for the protection of aquatic ecosystems for reasons outlined in Section 6.1.1.

Groundwater Quality for the Mine

A groundwater quality monitoring program is undertaken at the Mine in accordance with the requirements of the EA. The program targets the Walloon Coal Measures aquifer and the Tertiary Basalt aquifer. The following provides a summary of the groundwater monitoring results which have been collected since the commencement of the program.


The results for pH from groundwater bores in the Walloon Coal Measures are shown in Figure 6-8.

Based on the results obtained from groundwater monitoring bores installed in the Walloon Coal Measures, pH was generally neutral to slightly alkaline and ranged from 6.8 to 9.6. The ADW Guidelines suggest that the pH of drinking water should be between 6.5 and 8.5. The majority of the results were within this guideline limit.

The results for electrical conductivity (EC) from groundwater bores in the Walloon Coal Measures are shown in Figure 6-9. EC within the Walloon Coal Measures ranged from 530 µS/cm to 11 000 µS/cm.


pH for the Walloon Coal Measures

6.5

7

7.5

8

8.5

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9.5

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Ground Water Bore 848c Ground Water Bore 82Pc Ground water Bore 83Pc Ground Water Bore 958

Ground Water Bore P2008c Ground Water Bore 81Pc Ground Water Bore P2007 Ground Water Bore 18Pc

Ground Water Bore 27Pc Ground Water Bore 28Pc Ground Water Bore 16Pc Ground Water Bore 17Pc

Figure 6-8 pH results for the Walloon Coal Measures

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Total Dissolved Solids (mg/l) for the Walloon Coal Measures




Figure 6-9 Electrical Conductivity results for the Walloon Coal Measures


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Electrical Conductivity (uS/cm) for the Walloon Coal Measures




Figure 6-10 Total Dissolved Solids for the Walloon Coal Measures

Figure 6-10 shows the results for Total Dissolved Solids (TDS) for groundwater bores in the Walloon Coal Measures.

TDS results ranged from 330 mg/L to 6,900 mg/L. The tolerance of the livestock to TDS in drinking water has been identified in the ANZECC Guidelines. In order for no adverse effects to occur to animals, the upper limit for TDS is 4,000 mg/L. The majority of results from the groundwater monitoring in the Walloon Coal Measures are within these guideline limits and therefore suggest that the quality of water in the bores monitored is acceptable for livestock use. However bores, 16Pc, 17Pc, 27Pc, 28Pc and 848c had results above 4,000 mg/L which exceed the upper limit of the ANZECC Guidelines. The ANZECC Guidelines also state that when TDS ranges from 4 000 mg/L to 10 000 mg/L, animals may have an initial reluctance to drink, however, they should eventually adapt to these conditions without a measurable loss of production.

It is noted that Bore 958 recorded a TDS value of 32 000 mg/L on one occasion in the period monitored. On the basis that this result was not repeated and similar levels were not found in any other bores, the result has been considered to be anomalous and was removed from the dataset.


The results for pH in the Tertiary Basalts are shown in Figure 6-11.


pH in the Tertiary Basalts

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7

7.5

8

8.5

9

Ground Water Bore 84Pb Ground Water Bore 843b Ground water Bore 18Pb

Figure 6-11 pH results for the Tertiary Basalts

The results for pH within the Tertiary Basalts ranged from 7.0 to 8.6, which indicates that groundwater quality within the basalts is neutral to slightly alkaline. An increase in pH levels is noted for groundwater bore 18Pb from March 2004 to October 2005. A slight increase in pH levels is also noted for groundwater bore 843b. The majority of the results were within the ADW Guideline limit of 6.5 to 8.5.

The results for EC from groundwater bores in the Tertiary Basalt are shown in Figure 6-12.

Figure 6-13 shows the results for TDS for groundwater bores in the Tertiary Basalt.

The groundwater salinity in the Tertiary Basalts is lower than the Walloon Coal Measures, with TDS ranging from 250 to 2 600 mg/L (i.e., 550 to 4 300 mg/L EC). Accordingly, a greater number of users extract groundwater from this aquifer for livestock and domestic purposes.

Figure 6-13 displays an increase in TDS result for groundwater bore 84Pb. TDS and EC recorded in groundwater bore 18Pb remained relatively consistent. Groundwater 843b displays a slight increase in TDS and EC from April 2006 to October 2006. All of the groundwater monitoring results from the Tertiary Basalts were within the ANZECC Guidelines for livestock use of 4 000 mg/L.


Electrical Conductivity (uS/cm) in the Tertiary Basalt

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Figure 6-12 Electrical Conductivity results for the Tertiary Basalts

Total Dissolved Solids (mg/l) in the Tertiary Basalts

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Figure 6-13 Total Dissolved Solids results for the Tertiary Basalts


Groundwater Quality for Project site

Groundwater quality monitoring was undertaken from monitoring wells installed within the Walloon Coal Measures at the Project site.

Physico-chemical results from the Project baseline groundwater monitoring program are summarised in Table 6-10.

Table 6-10 Physico-chemical Results from Project Groundwater Monitoring (October 2007)

Site Number Dissolved Oxygen % Saturated

TDS (mg/L) Electrical Conductivity (µS/cm)

pH Redox (mV) Temperature (ºC)

121WB (E012*) 25.9 3 140 - 7.05 275 28.9 113PGC A (E012*) 34.0 3 770 6020 6.81 -178 30.1 113PGC B (E012*) 18.4 2 930 4770 6.95 -280 25.9 118P (E016*) 33.7 6 610 10340 7.06 -216 24.6 117PGC (E016*) 43.4 2 740 4530 7.43 -250 26.7 109P (E003*) 15.2 330 - 8.17 -270 26.4 111PGC lower (E014*) 27.8 2 940 - 7.11 -2 24.2 111PGC upper (E014*) 23.4 4 220 6740 7.04 -299 23.4 119PGC (E019*) 30.5 1 280 2130 7.37 -32 24.5 116P (E021*) 47.9 1 240 2260 7.38 85 31.3

Note: *The mine site numbers are also known as these site numbers (E series) and have been identified here for reference purposes.

As shown in Table 6-10, pH in groundwater ranged from neutral to slightly alkaline (6.81 to 8.17). All of the results were within the ADW Guideline limit for pH.

The EC results indicate that the groundwater is generally brackish. The TDS results ranged from 330 to 6 610 mg/L. The majority of results from the groundwater monitoring in the Walloon Coal Measures are within the ANZECC Guidelines of 4 000 mg/L for TDS and therefore suggest that the quality of groundwater is acceptable for livestock use. Bores 118P and 111PGC had results above 4 000 mg/L which exceed the upper ANZECC Guideline limit.

The DO results ranged from 15.2% to 47.9 % saturation with redox results ranging from 275 mV to 299 mV.

A single round of major ion and dissolved metals chemical analysis was undertaken in October 2007. The laboratory results for the analysis are included in Appendix G.3. Table 6-11 provides a summary of the results.


Table 6-11 Groundwater Quality Results from Project Groundwater Monitoring

Analyte ADWG Drinking Water

ANZECC Irrigation

ANZECC Livestock

No. of Samples Minimum Median Maximum

Hydroxide Alkalinity as CaCO3

- - - 10 <1 <1 <1

Carbonate Alkalinity as CaCO3

- - - 10 <1 <1 <1

Bicarbonate Alkalinity as CaCO3

- - - 10 108 412 527

Arsenic 0.007 0.1 0.5 10 <0.001 0.0025 0.003 Cadmium 0.002 0.01 0.01 10 <0.0001 0.001 0.001 Chromium 0.05 0.1 1 10 <0.001 0.008 0.008 Copper 2 0.2 0.5 10 <0.001 0.002 0.004 Lead 0.01 2.0 0.1 10 <0.001 0.005 0.009 Nickel 0.02 0.2 1 10 <0.001 0.002 0.002 Zinc 3 2.0 20 10 0.005 0.011 0.046 Mercury 0.001 0.002 0.002 10 <0.0001 <0.0001 <0.0001

Note: All results and guideline values are reported in mg/L

Based on the comparison of physico-chemical and groundwater quality results to the ANZECC Guidelines and ADW Guidelines, groundwater from the Walloon Coal Measures within the Project site is considered suitable for livestock watering.

The normalised results from major ion chemistry analysis are presented as a Piper tri-linear diagram in Figure 6-14. Based on this plot, groundwater quality in the Walloon Coal Measures is generally brackish (saline) with sodium chloride ions dominating. However, slight variations in water chemistry within the Walloon Coal Measures were present which indicates the occurrence of different levels of water-rock interaction. This characteristic is due to the residence time of the groundwater, weathering processes and recharge inputs.


Figure 6-14 Piper tri-linear diagram showing groundwater composition type in the Project site

Comparison of Groundwater Quality Data to the Environmental Values in the EPP Water

The following provides a comparison of the groundwater quality data with respect to the EVs for the Project site as listed in the EPP (Water).

Aquatic Ecosystems

Groundwater quality is likely to be ‘non pristine’ due to the level of anthropogenic development existing within the Project site. Groundwater in the Project site is observed to be moderate to good quality and has been identified as being suitable for drinking water, irrigation and livestock. Studies undertaken as part of Stage 2 EIS compared groundwater levels to stream bed levels under average conditions and found that groundwater does not contribute to surface water flows. Accordingly, it is considered unlikely that baseflow systems exist within the Project site. As a result, the potential for mining to impact on the Quaternary Alluvial aquifer which may influence aquatic ecosystems is considered low.

Calcium(Ca) Chloride(Cl) + Fluoride(F)

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Recreational, Agricultural and Industrial Use

Recreational uses for groundwater encompass primary and secondary contact such as swimming and boating respectively. Given that the depth to groundwater is generally greater than 10 mBGL, it is unlikely that there is input from the groundwater to water bodies which may be used for recreational purposes. Therefore, recreational use of groundwater within the Project site is considered negligible.

Agricultural uses of groundwater in the Project site are dominated by livestock watering and to a lesser extent irrigation. Groundwater use for livestock purposes has been identified to occur locally in the Tertiary Basalt aquifer. The Walloon Coal Measures aquifer supplies brackish livestock water and is generally low yielding (up to 1 L/sec). Livestock watering and municipal supplies have also been identified to be extracted from the Marburg Sandstone aquifer.

The Mine currently extracts groundwater for use at the Mine from the Heildon Sandstone, Marburg Sandstone and Tertiary Basalt aquifers. Groundwater flowing into the existing mine pits from the Walloon Coal Measures aquifer is also used by the Mine.

Drinking Water

A comparison of the groundwater quality data to the ADW Guidelines indicates that groundwater within the Tertiary Basalt, Marburg Sandstone and Helidon Sandstone aquifers is generally suitable for potable use. Groundwater quality data demonstrates variability between and within aquifers. Groundwater use for domestic purposes has been identified to occur locally in the Tertiary Basalt aquifer.

Groundwater within the Walloon Coal Measures is generally unsuitable for potable use, primarily due to elevated salinity levels.

6.2.12. Aquifer Testing in the Walloon Coal Measures

Aquifer testing was conducted at two locations within the Project site. The locations of these bores are shown in Figure 6-15. Each location consisted of a production bore and two nearby observation bores, namely:

Location 1: 120WB (Production bore) and 118P and 117PGC (Observation bores); and

Location 2: 121WB (Production bore) and 113PGCA and 113PGCB (Observation bores).

The aquifer tests targeted the Walloon Coal Measures as the primary aquifer that will be affected by the Project. Hydraulic properties of this aquifer were obtained by conducting a step test and a constant rate test at each pumping test site. The methodology used for aquifer testing and the data collected is provided in Appendix G.4.

Aquifer pumping test results were analysed to derive the hydraulic properties (transmissivity and storativity) for the Walloon Coal Measures aquifer within the Project site. Transmissivity and storativity characteristics of the Walloon Coal Measures aquifer are discussed below.

Transmissivity

Transmissivity is a parameter which describes an aquifers ability to transmit water. It is calculated as the volume of water flowing through a cross-sectional area of an aquifer that is a certain thickness under a


certain hydraulic gradient in a given amount of time. Transmissivity values derived for the Walloon Coal Measures aquifer are summarised in Table 6-12. Outputs from these analyses are included in Appendix G.4.

Table 6-12 Transmissivity Values

Location Bore ID Transmissivity (m2/day) Deep/Shallow Bore

Location 1 120WB 6.5 Deep 117P 8.2 Deep

Location 2 121WB 47 Shallow 113PGCA 31* Shallow

*Note: Value was derived using the Hantush-Jacob (1955) leaky aquifer solution. All other values derived using the Theis (1935) confined aquifer solution.

An assessment of the results suggests that Location 1 is representative of transmissivity values for the deeper coal seams where as Location 2 reflects transmissivity values for the shallow coal seams.

Pumping tests conducted during the Stage 2 EIS indicated that transmissivity values of 30 m²/day were observed within the Walloon Coal Measures aquifer. This result is consistent with transmissivity values observed at Location 2 (113PGCA - Observation bore).

Storativity

Storativity is a parameter which describes an aquifers ability to release or store water under certain conditions. Storativity values for the Walloon Coal Measures aquifer are summarised in Table 6-13. Outputs from these analyses are included in Appendix G.4.

Table 6-13 Storativity Values

Location Bore ID Storage Coefficient (dimensionless) Deep/ Shallow Bore

Location 1 120WB - Deep 117P 0.00006 Deep

Location 2 121WB - Shallow 113PGCA 0.006 Shallow

*Note: Value was derived using the Hantush-Jacob (1955) leaky aquifer solution. All other values derived using the Theis (1935) confined aquifer solution.

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Location 1 is screened in the deeper aquifer and has a lower storativity compared with Location 2 which is screened in the shallow aquifer. Although the results suggest that the lower aquifer is fully confined at this location compared with the shallow aquifer which is semi-confined, it is likely that the lower aquifer is also semi-confined (i.e., leaky aquifer system).

Summary

Results obtained from the pumping tests undertaken at the two locations suggest that the Walloon Coal Measures is a single system with variable aquifer parameters. A semi-confining layer consisting of carbonaceous mudstone and siltstone exists within the coal measures. Although short-term pumping tests indicate that the coal seams behave as discrete aquifers separated by carbonaceous mudstones and siltstones, it is likely that over the long-term the seams will behave as one aquifer system when stressed by dewatering during mining operations.

Pumping tests conducted as part of the Project baseline assessment suggest that a leaky aquifer system exists. Vertical movement of groundwater occurs where the confining layer of carbonaceous mudstone and siltstone is thin or absent within the coal measures.

6.2.13. Hydrogeological Conceptual Model

A hydrogeological conceptual model has been formulated for the Project site based on the geological and hydrogeological data for the Mine and the Project. The data indicates that the geology and hydrogeology of the Mine is similar to that found within the Project site.

The hydrogeological conceptual model describes the aquifers present within the Project site, how they interact with each other and surface waters and their attributes such as groundwater depth, thickness, transmissivity, storativity and hydraulic conductivity. The hydrological conceptual model for the Project site is shown in Figure 6-16.

The aquifers present within the Project site include the following:

Quaternary Alluvial aquifer;

Tertiary Basalt aquifer;

Walloon Coal Measures aquifer;

Marburg Sandstone aquifer; and

Helidon Sandstone aquifer.

These aquifers are described further in the following Sections.


The Project siteTertiary Basalt (aquifer)

Depth of faulting is unknown

Quaternary Alluvial aquifer

The MineAcland

NORTHSOUTH 0 m

Texas Beds (aquitard)

Walloon Coal Measures aquifer

Marburg Sandstone aquifer200 m

400 m

600 m

800 m

Evergreen Formation (aquitard)

Helidon Sandstone aquifer

Figure 6-16 Hydrogeological Conceptual Model

Quaternary Alluvial Aquifer

The shallow Quaternary Alluvial aquifer is limited in aerial extent and may exist in association with Lagoon Creek at the Project site. During periods of intense rainfall when Lagoon Creek is flowing, groundwater in this aquifer may interact with surface water. However, Lagoon Creek is predominately dry and consequently during these dry periods there will be no groundwater and surface water interaction. Accordingly, this aquifer is considered to be minor within the Project site.

Areas of recharge and discharge exist along Lagoon Creek. The predominant mechanism for recharge is direct infiltration. Discharge is likely to occur via evapotranspiration and infiltration to underlying aquifers.

Due to the minor nature of this aquifer and its low use within the Project site, data on groundwater yield and quality within the Project site was not obtained. Furthermore, there is no requirement for the Mine to monitor the water quality or quantity of this aquifer under the EA.



There is a minor outcrop of the Tertiary Basalt aquifer in the northern section of the Project site. The location of this aquifer in relation to the Project’s mine pits means that this aquifer is unlikely to be affected by the Project.

Where present in the Project site, the Tertiary Basalt aquifer consists of olivine basalts and varies in thickness from 1 m to 90 m. The Tertiary Basalt aquifer is interbedded with clay which has the potential to act as an aquitard within this aquifer.

Permeability within this aquifer is considered to consist of both primary and secondary porosity; however the latter is expected to dominate. The Tertiary Basalt aquifer has relatively shallow depth to groundwater at the Project site. Groundwater yield in the Tertiary Basalt aquifer can be up to 10 L/sec. An average bore yield of approximately 3 L/sec to 5 L/sec was reported in the Stage 2 EIS.

Pumping test data obtained from the Stage 2 EIS indicate a transmissivity of 150 m²/day and storativity ranging from 0.001 to 0.05. Based on this data and assuming a 90 m thickness in the Tertiary Basalt, hydraulic conductivity has been estimated as 1.6 m/day. The storativity values suggest that the aquifer is unconfined to semi-confined.

The DERM uses a uniform value of 80 mm of groundwater recharge per annum for basalt aquifers in the local area as part of water allocation assessments. This factor has been calculated to be approximately 12.7% of annual mean rainfall based on 629 mm mean annual rainfall observed at the Oakey Aero station. This suggests that recharge rates are high. Therefore, given this aquifer outcrops in the northern section of the Project site, the main recharge mechanism is direct infiltration from rainfall.

The Mine currently draws groundwater from the Tertiary Basalt aquifer. This potable water supply is currently covered under a license for 160 ML/year. However, the Mine uses only approximately 20 ML/year of this allocation. Groundwater extraction from the Tertiary Basalt aquifer is also undertaken by nearby private groundwater users. Groundwater salinity in the Tertiary Basalt aquifer is generally lower than in the Walloon Coal Measures aquifer. This fact is reflected by a greater number of livestock and domestic users in the Tertiary Basalt aquifer.


The Walloon Coal Measures will be the main aquifer which will be affected by the Project. The Walloon Coal Measures outcrop across much of the Project site with coal seams being the principal conduit for groundwater. Pumping tests undertaken in this aquifer, suggests that it is semi-confined with seams being up to 30 m in total thickness. Groundwater within the Walloon Coal Measures regionally flows from the north-east to south-west in accordance with the regional dip of the coal seams. Groundwater flow within this aquifer at the Project site is to the south and south southwest.

Recharge into the upper portions of the Acland Sequence, is likely to be predominantly via coal subcrop areas on the upthrown side of faults and through deep drainage from the overlying alluvium. The comparatively higher salinity of groundwater in the lower seams of the Acland-Sabine interval and underlying Balgowan interval suggests that recharge zones for these measures are progressively more remote and groundwater has longer residence times and longer migration paths. Leakage from underlying and overlying seams within the Walloon Coal Measures to these lower-lying coal seams is likely to be insignificant.


Discharge from the Walloon Coal Measures aquifer is likely to occur via mine pit dewatering and coal outcrop areas within the Clarence-Moreton Basin.

Significant surface water and groundwater interaction is unlikely for the Walloon Coal Measures aquifer. Groundwater has been identified as not contributing to surface water flows within nearby creeks and streams. Groundwater levels within the Walloon Coal Measures underlying the Project site range from 10.3 mTOC to 45.9 mTOC.

The Walloon Coal Measures aquifer varies from being confined to semi-confined by low permeability mudstones and siltstones which occur in between the coal seams. Short term pumping tests indicate that the coal seams behave as separate aquifers. However, it is considered likely that over the long term the seams would behave as one aquifer system when stressed by dewatering in association with mining operations. Results from these tests suggest that a leaky aquifer system is likely to exist with vertical movement of groundwater occurring where the confining layer is thin and via fractures within the coal measures aquifer system.

Transmissivity values within the Walloon Coal Measures were estimated to range between 7 m2/day to 47 m2/day. Based on the transmissivity values, a hydraulic conductivity of 0.1 m/day has been estimated for this aquifer.

Transmissivity values obtained from pumping tests undertaken for the Stage 2 EIS are consistent with those observed in groundwater observation bore 113PGCA. This result demonstrates that the transmissivity of the Walloon Coal Measures aquifer is similar from the Mine to the Project site.

Storage coefficients were estimated to range between 0.006 and 0.00006 for the shallow and deep aquifers respectively. Groundwater yield has been estimated to be 1 L/sec or less based on V-notch tests from bores within this aquifer. Groundwater quality in the Walloon Coal Measures at the Project site is slightly acidic to slightly alkaline and is generally brackish with sodium chloride ions dominating.

Marburg Sandstone Aquifer

The Marburg Sandstone aquifer underlies the Walloon Coal Measures and is up to 500 m thick. This aquifer exists as a confined aquifer at a depth of about 150 m within the Project site and is part of the GAB.

Aquifer parameters based on pumping tests conducted for the Stage 2 EIS indicate a transmissivity of 14 m²/day and a storativity of 0.003. Based on this data, hydraulic conductivity for this aquifer has been estimated as 0.028 m/day.

Aquitards within the Walloon Coal Measures act as effective confining layers for the Marburg Sandstone aquifer. Groundwater levels obtained from on and off site bores ranged from 410 m AHD to 425 m AHD. Typical production rates range from 5 L/sec to 25 L/sec within this aquifer. The higher yields indicate that the transmissivity of the aquifer may be larger than 14 m2/day as indicated in the Stage 2 EIS pumping tests.

Infiltration of groundwater from overlying or underlying aquifers, in the unstressed state, is considered negligible given the confined nature of the Marburg Sandstone aquifer. The comparatively lower water quality in this aquifer reflects greater concentration and / or greater water-rock interaction associated with longer groundwater residence times. Recharge within this aquifer is likely to occur from surface water infiltration where the geological formation crops out to the northeast of the Project site.


The Mine currently extracts groundwater for industrial and potable use from the Marburg Sandstone aquifer and has an allocation of 571 ML/year. The Mine and other nearby private groundwater users are the main sources of groundwater extraction from the Marburg Sandstone aquifer.

Groundwater extraction from the Marburg Sandstone aquifer for industrial use will cease in late 2009 once the WWRF Pipeline is in operation. The cessation of this extraction is anticipated to be of positive benefit to the GAB which is a stressed groundwater resource.

The Marburg Sandstone aquifer is a confined aquifer located below the Walloon Coal Measures. Therefore, the Project’s mine pits and final voids will not have an impact on this aquifer.

Helidon Sandstone Aquifer

The Helidon Sandstone is the deepest aquifer at the Project site and is part of the GAB. This aquifer is separated from overlying aquifers by the relatively impermeable Evergreen Formation and is up to 170 m thick.

Pumping test data indicates the transmissivity of this formation is likely to vary between 45 m²/day to 200 m²/day. Based on this data, hydraulic conductivity has been estimated to range from 0.26 m/day to 3.9 m/day. Recharge to the Helidon Sandstone aquifer occurs where the aquifer outcrops in the northeast. This area represents the primary source of recharge to the aquifer via infiltration of rainfall and overland surface water flow.

The Mine currently extracts groundwater from the Helidon Sandstone aquifer for industrial and potable use and has an allocation of 710 ML/year from this aquifer. The Mine and other nearby private groundwater users are the main sources of groundwater extraction from the Helidon Sandstone aquifer.

A decline in groundwater levels in the Helidon Sandstone aquifer has been observed in a monitoring bore close to the Mine. Groundwater extraction from the Mine is the most likely cause of the decline in groundwater levels. Groundwater extraction from the Helidon Sandstone aquifer for industrial use will cease in late 2009 once the WWRF Pipeline is in operation. The cessation of this extraction is anticipated to be of positive benefit to the GAB which is a stressed groundwater resource.

The Helidon Sandstone aquifer is a confined aquifer and is located below the impermeable Evergreen Formation, which in turn is located below the Marburg Sandstone. Accordingly, the Project’s mine pits and final voids will not have an impact on this aquifer.

6.3. Impact Assessment

The Project will include a series of mine pits and final voids which will intersect the Quaternary Alluvial aquifer and the Walloon Coal Measures aquifer. The Quaternary Alluvial aquifer is considered to be a minor aquifer within the Project site and is not a significant groundwater resource. It is unlikely to be impacted by the Project due to its limited use and limited interaction with surface water.

The Walloon Coal Measures is the major groundwater aquifer intersected by the Project. There are 88 registered bores in this aquifer within 3 km of the Project site. As a result, potential impacts from the Project are predominantly associated with the Walloon Coal Measures aquifer. The assessment of potential impacts on the Walloon Coal Measures aquifer is the focus of this Section.


The following discussion provides an assessment of the potential impacts from the Project on the Walloon Coal Measures aquifer and to a lesser extent the Quaternary Alluvial aquifer. The assessment includes potential impacts on:

groundwater level;

groundwater use and users;

groundwater quality; and

groundwater dependent ecosystems.

This Section does not include an assessment of potential impacts from the Mine’s current groundwater extraction in the Tertiary Basalt, Marburg Sandstone and Helidon Sandstone aquifers. Approval for the extraction of groundwater from these aquifers has already been obtained. Groundwater extraction from the Marburg Sandstone and Helidon Sandstone aquifers for industrial use will cease in late 2009 once the WWRF Pipeline is in operation. The cessation of this extraction will be a positive benefit to the GAB which is a stressed groundwater resource.

The Project’s mine pits and final voids will not impact on the Tertiary Basalt, Marburg Sandstone and Helidon Sandstone aquifers for reasons described in Section 6.2.13.

6.3.1. Impacts on Groundwater Levels

Throughout the operational phase of the Project, the mine pits will intersect the water table and some groundwater will discharge to them. Groundwater discharge into the mine pits will cause drawdown in groundwater levels in the Walloon Coal Measures aquifer. The mine pits will be excavated as a series of strips which will be backfilled and rehabilitated after each strip has been mined. Following cessation of mining, groundwater will continue to discharge to the main final void until water levels within the Walloon Coal Measures aquifer recovers to equilibrium.

Numerical groundwater modelling has been conducted to determine the potential magnitude and extent of impact of mining on groundwater levels within the Walloon Coal Measures aquifer, including the potential impact on neighbouring groundwater users. The following Sections summarise the numerical modelling undertaken and the predicted impact on groundwater levels in the Walloon Coal Measures aquifer.

Analytical modelling to assess the impact of mining on groundwater levels was also considered. However, it was determined following assessment that this modelling method was unable to replicate the mine expansion and rehabilitation process, multilayered nature of the geology and the complex faulting in the region. Due to these limitations the impacts were evaluated using a numerical model. The full details of the groundwater model are presented in Appendix G.5.

Numerical Groundwater Modelling

A fully transient three dimensional finite difference groundwater flow model of the Mine and its surroundings has been developed in the MODFLOW 2000 code using Visual Modflow Version 4.3. The model is subdivided vertically into four separate layers corresponding to hydrogeological units derived from interpreted drill hole information. Permeability values for the faults were refined during the model calibration process.


Assumptions and hydrogeological parameters used in the numerical model are based on the hydrogeological conceptual model developed in Section 6.2.13 and the life of mine plan described in Chapter 3 Project Description.

The current mine plan extends for a 20 year to 25 year period to 2042. As a consequence, the groundwater model assumed a sequence of time periods up to 25 years. The migration of the mined area is simulated in the model as a series of 12 zones which are activated in the model when they are scheduled to be mined and de-activated as they are planned to be rehabilitated. At the completion of mining the last zone to be mined (zone 12) remains active to simulate the final mine void. Groundwater meddling zones and the Proejcts mining schedule are depicted in Figure 6-17.

The model was calibrated by steady state simulations that represent pre-mining conditions at the Project site. This process was used to demonstrate that the model is able to replicate measured groundwater levels at the Project site and in order to attain stable and consistent starting conditions for subsequent transient models. Measured groundwater levels from 16 monitoring bores in the Walloon Coal Measures, 9 bores in the Tertiary Basalts and 16 bores in the Quaternary Deposits, were chosen for calibration purposes.

Other critical assumptions for the model include the mine pit depth and the cumulative area of the mine pits. Further information on the numerical model prepared, the modelling process, model assumptions and results is provided in Appendix G.5.

Based on the numerical modelling undertaken, the predicted impact on groundwater levels in the Walloon Coal Measures aquifer is discussed in the following Sections for the operational and post-mining phases of the Project.

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LEGEND# Locality

RoadCadastreExisting Mining LeaseStage 3 Mining Lease ApplicationStage 3 MDL

MINING SEQUENCE Year Zone

2002 - 2004 02005 - 2007 12008 - 2012 22013 - 2015 32016 - 2018 42019 - 2021 52022 - 2024 62025 - 2027 72028 - 2030 82031 - 2033 92034 - 2036 102037 - 2039 112040 - 2042 12

Groundwater Modelling Zonesand the Project Mining Schedule


Impacts on Groundwater Levels During Mining

Groundwater discharge into the mine pits will lead to a depression or drawdown of the groundwater levels in the Walloon Coal Measures aquifer within the vicinity of the Project site. The numerical model was used to estimate groundwater level drawdown in the Walloon Coal Measures aquifer at six different time periods to assess the impact of drawdown over time as depicted in Figure 6-18.

In summary, the results show that over the life of the Project, drawdown in areas outside the boundary of MDL 244 is less than 5 m. During the first 11 years of mining, drawdown occurs entirely within MDL 244’s boundary, except for a small area of drawdown of approximately 1 m to 5 m that occurs 1 km beyond the north eastern boundary. After the first 11 years of mining, the area affected by drawdown outside MDL 244’s boundary gradually extends to the north-west and south-east to approximately 5 km from the boundary. The results also show the centre of drawdown migrating across the mine area as each new mining zone is excavated, followed by recovery of water levels after mining ceases in each zone.

An assessment on the potential impacts to groundwater users from drawdown is provided in Section 6.3.2.

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Impacts on Groundwater Levels Post Mining

After cessation of mining in 2042, groundwater levels are predicted to gradually recover so that there is less than 0.5 m drawdown outside MDL 244’s boundary as depicted in Figure 6-19. Drawdown in the last zone to be mined (zone 12) is predicted to remain high (approximately 50 m) due to the ongoing groundwater discharge into the main final void.

The amount of groundwater discharge into the main final void after mining was completed would normally be expected to decline as de-watering operations cease and groundwater gradually fills the main final void. However, with an actual evaporation rate of 756 mm, the volume of water lost from the main final void due to evaporation alone is estimated to be 1 400 ML/year which is significantly greater than the predicted discharge rate of 250 ML/year as defined in Figure 6-20 at the completion of mining. Due to the evaporation rate being significantly larger than the groundwater discharge rate, it is unlikely that groundwater will collect in the mine void in any significant quantities, and as a result, groundwater discharge may continue at a rate similar to that in the last year of mine operation.

As a dynamic system, the quantity of water remaining in the main final void will be influenced over time by other factors, such as climate (e.g. ambient temperature and humidity profiles, rainfall patterns, and wind conditions) and the amount of overland flow directed to the main final void. Nevertheless, it is still surmised that the evaporative loss from the main final void will remain greater than the sum of the water inputs, especially as overland flow is planned to be diverted away from the main final void.

As a result, a permanent drawdown cone is expected to form around the main final void resulting in drawdown values of less than 0.5 m outside MDL 244’s boundary.

Although the recharge characteristics and hydraulic properties of the backfill have not been quantified, the backfill is expected to be less stratified and less consolidated than the original formation and as a result, the aquifer storativity is predicted to increase which, in turn, is expected to cause an increase in the recharge rate to the Walloon Coal Measures aquifer. The amount of increased recharge into the aquifer is difficult to ascertain due to the expected variability of the porosity, consolidation rate and vertical hydraulic conductivity of the backfilled sediments. An increase in recharge may, in the medium term (5 years to 50 years), result in slightly less drawdown than predicted by the current groundwater model.


Mineral Development Lease Boundary

Figure 6-19 Predicted drawdown in the Walloon Coal Measures 50 years after cessation of mining


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Figure 6-20 Predicted groundwater discharge rate into the mine during and after mine operation

6.3.2. Impacts on Groundwater Users Impacts to Groundwater Users During Mining

Based on the estimated groundwater level drawdown in Section 6.3.1, the influence of dewatering on adjacent groundwater users can be estimated. The numerical model predicts that the impact of groundwater drawdown on surrounding properties at the end of the mine life extends to approximately 5 km from the centre of the Project’s mine pits. Properties within 2 km of the centre of the Project mine pits will have the greatest impacts with drawdown in the Walloon Coal Measures between 2 m to 5 m.

Drawdown in the Marburg Sandstone is calculated to be less than 5 m outside the MDL 244 boundary. However, the amount of drawdown is relatively minor and is unlikely to have any effect on the yield or access to water in existing bores. Properties with bores situated more than 5 km from MDL 244’s boundary are unlikely to experience drawdown effects. The groundwater quality within bores is not expected to change during mining as described in Section 6.3.3.

Impacts to Groundwater Users Post Mining

Groundwater drawdown outside MDL 244’s boundary is predicted to gradually decline from 1 m to 5 m to less than 0.5 m in both the Walloon Coal Measures and the Marburg Sandstone.

The groundwater quality within bores is not expected to change following the cessation of mining as described in Section 6.3.3.


6.3.3. Impacts on Groundwater Quality Impacts on Groundwater Quality During Mining

The Mine has not had a detrimental impact on groundwater quality and therefore, the Project is not expected to have a detrimental impact on the groundwater quality.

Potential sources of contamination to groundwater may include incidents involving significant fuel or oil spills. In the event of this type of incident occurring, potential impacts would be contained on the surface and unlikely to impact on groundwater resources. In addition, fuel, oil and other hydrocarbons are managed in an environmentally responsible manner at the Mine to minimise the risk of adverse impacts to the receiving environment. This management approach will continue for the Project and will involve actions, such as bunding around storage tanks, the use of oil-water separators for stormwater collection at workshops, the development of standard operating procedures, the maintenance of accurate inventories of materials stored on site, the use of spill kits and other similar devices and the continued use of an up-to-date emergency response plan.

To date, net acid generation resulting in the lowering of pH in water in the mine pits has not occurred at the Mine and is not expected to occur within the Project’s new mining areas, due to the shared geological and depositional formation.

The extraction of groundwater within the Project site will create a depression in groundwater levels. As a result, groundwater in the Walloon Coal Measures aquifer surrounding the Project site will move towards this depression. The aquifers surrounding the Project site will continue to receive recharge via the same processes that occurred prior to the operational phase of the Project. Therefore, the groundwater in the vicinity of the Project should be of similar quality to its current physico-chemical state.

As previously explained, due to the confined state of the underlying Marburg Sandstone and Helidon Sandstone aquifers, potential impact to these aquifers is negligible. The Tertiary Basalt aquifer is not expected to be affected by the Project.

In summary, the operational phase of the Project is not expected to impact on groundwater quality. Groundwater quality will continue to be monitored throughout the life of the Project to confirm that potential impacts are not occurring.

Impacts on Groundwater Quality Post Mining

The final voids will potentially collect and accumulate water from:

groundwater ingress from the Walloon Coal Measures aquifers;

direct rainfall; and

overland runoff.

Water quality in the final voids is anticipated to be saline due to inflows of saline groundwater from the Walloon Coal Measures. Saline groundwater collected in the final voids will probably be further concentrated by evaporation. Section 6.3.1 predicts that the volume of water captured by final voids in the long term will be minimal or nil due to evaporation significantly exceeding the combined inflows. Therefore, the quantity of saline water captured by the final voids is not expected to be significant. Certain inflows into the final voids,


such as rainfall, will also have a positive effect by diluting any captured saline water. Finally, the final voids will act as groundwater sinks and as a result, will not permit water to flow outwards into the regional system. Therefore, any captured saline water should remain confined within the final voids.

It is unlikely that water captured in the final voids will become acidic from oxidation of pyrites in the Walloon Coal Measures because of the neutralising effect of the surrounding sediments which are alkaline by nature. Monitoring of water bodies associated with the Mine supports this assumption with no evidence of acid generation demonstrated on the Mine site to date.

Whilst not expected to occur, there is potential for density driven flow to groundwater in the Walloon Coal Measures aquifer immediately adjacent to the final voids. Should this occur, it is likely to be a localised impact immediately around the final void areas and of limited duration for the reasons outlined above. Chapter 3 Project Description outlines the location of the final voids remaining after the cessation of mining activities.

Water in the final voids will be at a lower level than the Quaternary Alluvial aquifer and therefore, cannot discharge to this aquifer. Water in the finals voids will not discharge to the Marburg Sandstone aquifer due to the drawdown in the Walloon Coal Measures.

In summary, the Project is not expected to impact on groundwater quality post mining.

6.3.4. Impacts on Groundwater Dependent Ecosystems

Groundwater Dependent Ecosystems (GDEs) are ecosystems which have their species composition and natural ecological processes determined by groundwater (ARMCANZ & ANZECC, 1996). Hatton and Evans (1998) defined four functional groups of GDEs including terrestrial vegetation, river baseflow systems, aquifer and cave systems and wetlands. Clifton and Evans (2001) expanded this list to include fauna and estuarine systems dependent upon groundwater discharge.

The health of the GDE is generally defined by four parameters: flux, level, pressure and quality (Clifton and Evans, 2001), with dependence potentially being a function of one or all of the above factors. Groundwater dependency can also vary spatially and temporally and is dependent upon whether the system represents a local or regional GDE.

The occurrence of potential GDE’s in the vicinity of the Project site has been determined by reviewing published DERM and Regional Ecosystem (2005) mapping data. Chapter 7 Terrestrial Ecology describes the Project related terrestrial ecosystems in detail. A review of the ecosystems existing within the vicinity of the Project site indicates that the water requirements for these species are likely to be derived from depths less than 10 m below ground level. Given that the depth to the water table in the Walloon Coal Measures aquifer is between approximately 10 m to 50 m below ground level, there are likely to be no GDEs present within the Project site.


6.4. Mitigation Measures

This Section describes the measures proposed to mitigate the potential impacts assessed in Section 6.3.

6.4.1. Groundwater Monitoring

Groundwater monitoring will be conducted on a regular basis during the operation of the Project. The primary aim of undertaking groundwater monitoring on site is to ensure sufficient baseline data is gathered for consideration of the following hydrogeological aspects:

temporal and spatial variations in groundwater levels;

temporal and spatial variation in groundwater quality; and

groundwater level or quality impacts (e.g., early detection of drawdown or groundwater quality caused by mine pit dewatering).

The groundwater monitoring program currently being undertaken by the Mine will be extended to include five extra locations in the Project site. Each of these locations will consist of a nested groundwater piezometer. Therefore, 10 additional bores will be installed in the Project site within the Walloon Coal Measures aquifer as indicated in Figure 6-21. The additional bores will be placed adjacent to each mine pit. The bores will be positioned so that the effects of mine dewatering and inflows can be monitored and distinguished from pumping undertaken in the Tertiary Basalt, Marburg Sandstone and Helidon Sandstone aquifers.

Groundwater bores 116P, 114P, 117P, 118PGC, 120WB, and 109P which were installed as part of the baseline investigations. All of these bores, except 114P, have been identified to exist outside of mine pit areas and therefore are not anticipated to be mined as part of the mining process. These bores will also be monitored as part of the monitoring program. In total, the groundwater monitoring program for the Project site will include 16 bores. The location of the monitoring bores is shown in Figure 6-21.

The monitoring program will be established prior to the commencement of mining to ensure there is sufficient baseline information on groundwater levels and quality. The monitoring program will target the Walloon Coal Measures aquifer, Tertiary Basalt aquifer and Quaternary Alluvium aquifer.

During operations, the monitoring program will provide data on groundwater levels, seasonal variation and the likelihood that nearby groundwater users may experience potential impacts. This information will enable NAC to determine the appropriate mitigation measures should an impact to a groundwater user occur.

Groundwater quality parameters monitored will be consistent with NAC’s current EA requirements.

Towards the end of the mine life and as part of mine closure planning, the need for groundwater monitoring and further modelling post-mine closure will be negotiated with the DERM.

6.4.2. Mitigation Measures for affected Groundwater Users

NAC will investigate all groundwater complaints related to the Project both during the operational phase and following mine closure. NAC will ensure all legitimate groundwater complaints are addressed in an expedient manner, and if possible, to the satisfaction of the affected party. If required in these circumstances, NAC will provide an alternative water supply arrangement. Due to the progressive nature of


drawdown within aquifers, the provision of alternative supplies may be staged. Options for possible alternative supplies include:

the installation of new pumps capable of extracting groundwater from greater depths within existing bores;

the deepening and / or refurbishment of existing bores; and

the installation of a new bores at other locations on the affected landholder’s property.

NAC will ensure its groundwater monitoring regime is adequate to identify possible impacts to neighbouring groundwater users from the Project’s operations (i.e., in relation to drawdown levels and water quality). NAC will ensure its groundwater monitoring regime is reviewed and updated on a regular basis in line with the progression of mining over the life of the Project. The Project’s groundwater monitoring regime will be periodically updated in the Mine’s current Environmental Monitoring Plan, which forms a supporting document to the Mine’s Plan of Operations.

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6.5. Conclusion

Five aquifers exist within the Project site. The Quaternary Alluvial aquifer is limited in spatial extent and is likely to exist in association with Lagoon Creek within the Project site.

A review of bore logs from drilling undertaken as part of the Project baseline assessment demonstrates that there is only a minor outcrop of the Tertiary Basalt Aquifer in the northern section of the Project site.

The Walloon Coal Measures aquifer outcrops over much of the Project site. Results obtained from the pumping tests undertaken suggest that the Walloon Coal Measures aquifer is a single system with variable aquifer parameters. Results suggest that a leaky aquifer system exists with vertical movement of groundwater occurring where the confining layer is thin or absent within the Walloon Coal Measures aquifer. The Walloon Coal Measures is the major groundwater aquifer intersected by the Project.

The Marburg Sandstone and Helidon Sandstone aquifers are a part of the Great Artesian Basin and are the deepest semi-confined to confined aquifers underlying the Project site. These aquifers will not be affected by the Project.

As part of the impact assessment, a numerical groundwater model was used to predict the impact of groundwater drawdown from mine pit dewatering. The modelling was used to assess the amount of drawdown and hence the potential impact of mine pit flows on existing groundwater users. The worst case scenario (high transmissivity and at the end of mine life) indicates that the radius of influence within the Walloon Coal Measures aquifer (zero drawdown) extends approximately 5 km from MDL 244’s boundary . Drawdown in the Walloon Coal Measures outside MDL 244 is between 1m to 5 m during mine operation decreasing to less than 0.5 m fifty years after cessation of mining operations. A drawdown of 5 m is unlikely to have any impact on the operation of existing pumping bores in the Walloon Coal Measures or Marburg Sandstone Aquifers.

Post closure, it is expected that groundwater will flow towards the main final void and as a result, the depression of the potentiometric surface within the vicinity of the final voids will act as a groundwater sink and will not permit water within the final voids to flow outwards into the regional system.

The groundwater monitoring program currently being undertaken by the Mine will be extended to include additional locations within the Project site. The groundwater monitoring program that will be undertaken on the Project site will include a minimum of 16 bores. Groundwater monitoring will be conducted on a regular basis and will provide information to detect any significant variations to the existing groundwater system over the life of the Project. The primary aim of undertaking groundwater monitoring on site is to ensure sufficient baseline data is gathered for consideration of the following hydrogeological aspects:

temporal and spatial variations in groundwater levels;

temporal and spatial variation in groundwater quality; and

groundwater level or quality impacts including early detection of groundwater drawdown caused by dewatering of the mine pits.

The Project is not expected to have a detrimental impact to the groundwater quality in the proximity of the Project site. The vulnerability of the underlying aquifers to pollution is expected to be minimal.


Mitigation measures can be put into place should the effects of dewatering require alternative water supplies such as installation of new pumps, deepening of existing bores or installation of a new bore at another location on the property. However, it is highly unlikely that these measures will be required.

After mining has ceased and decommissioning and rehabilitation works are complete, NAC will seek to relinquish its Mining Leases. Prior to relinquishment and as part of mine closure planning, NAC will discuss and agree with the administering authority, the need for on-going groundwater monitoring.

A comprehensive groundwater model will be constructed throughout the course of the mine life to accurately predict long-term behaviour of the aquifers. This modelling will assist the refinement of post mining groundwater monitoring programs.

groundwater resources - new hope group 06... · the review of other background data available on...

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