7 IMPACT EVALUATION 7.1 Highwall Mining

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7 IMPACT EVALUATION

The project will comprise a coal mine utilising combination of trench and highwall mining.

Based on the mine plan and schedule it is expected that the initial trench should take approximately one year to excavate to full depth allowing for the recovery of coal using the highwall miner from multiple coal seams as the trench excavation continues.

7.1 Highwall Mining

For the project, a continuous miner will operate within an open cut / trench allowing for coal extraction within both the low and highwall. The highwall mining machine will be positioned in front of the exposed seam and makes long parallel rectangular drives into the coal seam.

The coal seam is penetrated by a continuous miner propelled by a hydraulic Pushbeam Transfer Mechanism (PTM). A remote-operated cutter module is pushed into the seam by a string of push beams (unmanned coal-conveying elements) that transport the mined coal back to the entry of the drive onto a stockpile. The whole mining cycle is completed by a three- or four-man crew, with no personnel going underground at any time (CAT, 2011).

The highwall mining equipment will access coal from the purpose-prepared trench, as indicated in the proposed mine plan (Figures 7-2 and 7-3). The highwall mining is planned to penetrate nearly 300 m into the coal seam. Figure 7-1 is an illustration of the highwall mining system.

Figure 7-1 Highwall Mining System (CAT, 2011)

7.2 Highwall Mining Stability

The stability of highwall mining panels is related to a number of rock mechanics factors including:

• Pillar width-to-height ratio;

• Mass coal strength;

• Host rock stiffness;

• Rock/coal interface properties; and

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• Panel configuration.

Panel instability can occur due to pillar crushing, slip along pre-existing faults, and sudden release of energy due to alteration in stress fields.

It is noted that even where pillars fail, in contrast to high-extraction (e.g. longwall) mining, areas of failure involving pillars are not devoid of support. The pillars tend to resist formation of a goaf with significant voids; instead the overburden has a propensity to ‘sit’ en masse on the failing pillars (Holla, 1987).

It is considered that subsidence is unlikely to occur if the mine plan (panels and spacing) is based on rock mechanics so as to reduce the instability risk. In addition, a factor of safety is added to the highwall mining panel layout design to ensure stability.

7.2.1 Instability due to Groundwater Extraction

The relationship between groundwater level decline (in response to mine dewatering) and aquifer (coal seam) compression is considered for the project (not necessarily directly related to highwall mining but rather in response to mine dewatering).

The groundwater level drop in the confined Permian aquifers will cause a reduction in the upward pressure borne by the fluid. If the downward pressure placed on the aquifer by the weight of overlying rock and water, remains constant, then, a reduction in upward pressure borne by the fluid can result in an increase in the effective stress borne by the aquifer; this can lead to compression and possible land subsidence, i.e. If mine dewatering reduces the pressure head in the confined aquifer, the effective stress acting on the aquifer will increase; the aquifer can consolidate (compress) due to this increased stress. This compression can lead to land subsidence and minor changes in elevation (Sun et al, 1999).

In the project area any potential subsidence as a result of mine dewatering is considered to be negligible due to:

• The removal of the target coal seams will reduce the weight of rock overlying the aquifer, reducing the impacts of the reduction of upward pressure;

• Trenching removes large volumes of rock (weight) from the aquifers;

• The confined aquifers do not remain confined as the coal seam aquifers are dewatered; and

• The shallow depth and relatively small mine footprint within a large coal field.

7.3 Mining Process

The proposed mining at the project includes:

• A 21 year life of mine, comprising a southern pit and a northern pit (Figure 7-2);

• The mining plan targets the P08, P072, P071, P14, P162, P161, H152, H151, H52, D31, D302, D301 coal seams. These seams, from upper to lower, will be mined using the highwall mining (HWM) technique; and

• Figure 7-2 indicates the proposed mine sequence from south to north in the Southern Pit, and from north to south in the Northern Pit.

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A geological cross section (Figure 8-1) through the proposed pit indicates the HWM extent and target seams. The mining schedule allows for the removal of coal, from upper to lower, as the trench deepens over time.

7.3.1 Highwall Mining Details

The following mining details were provided with regards to the HWM proposed at Dysart East:

• The dimensions of the HWM holes are a maximum of 300 m long x 3.5 m wide;

• On the north-east (highwall) side of the pit the HWM holes are 300 m long for each seam mined; and

• On the south-west (low wall) side in the pit the length of the HWM hole is 300 m except for cases where the length of the HWM hole is limited to a lesser length by the MLA boundary or the location of the Lake Vermont Spur Railway (i.e. HWM does not extend beyond the MLA boundary or the location of the Lake Vermont Spur Railway).

7.3.2 Mining Schedule Details

The mine scheduling details proposed include:

• Mining occurs over a period of 21 years;

• Mining is initiated in a box cut at the southern end of the southern pit and proceeds in a northerly direction (Figure 7-2). For the northern pit (north side of Downs Creek) mining commences in the north and advances to the south towards the creek;

• Full mine depth is achieved at different rates in different areas of the pit, depending on the HWM schedule. Timing to reach full depth ranges between 2 and 4 years from commencement of mining in that area;

• As mining advances the pit is progressively back-filled and rehabilitated;

• The southern pit (south of Downs Creek) is fully mined within 13 years; and

• Mining of the northern pit commences in Year 10 of operations and continues until Year 21, when a final void remains in the southern area of the north pit.

Figure 7-2 shows that each pit (southern pit and northern pit) are divided approximately into thirds (southern third, middle third, and northern third, for each pit). This nomenclature is utilised for the discussion of pit inflow rates, which is presented in Section 8.5.

File No: Date:Approved:Drawn: Rev.

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GROUNDWATER TECHNICAL REPORT 7-2

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Whilst every care is taken by URS to ensure the accuracy of the digital data, URS makes no representation or warranties about its accuracy, reliability, completeness, suitability for any particular purpose and disclaims all responsibility and liability (including without limitation, liability in negligence) for any expenses,losses, damages (including indirect or consequential damage) and costs which may be incurred as a result of data being inaccurate in any way for any reason. Electronic files are provided for information only. The data in these files is not controlled or subject to automatic updates for users outside of URS.

DYSART EAST COAL MINEBENGAL COAL

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Source: JBT Consulting, May 2013, Stage 1 – Test Pit Comprising MDL 450 Water Management Strategy

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8 GROUNDWATER MODELLING

8.1 SEEP/W Model

The geology below the project is relatively simple; however due the multiple target coal seams, as well as the sequential mine plan, it was judged that the optimum approach to simulate the mining was to undertake 2-dimensional seepage modelling using the Seep/W model package. Seep/W is a finite-element model package capable of simulating groundwater movement and pressure distribution within the project soil and rock.

SEEP/W allowed for the estimate of:

• The rate and extent of change to the phreatic surface;

• Seepage face development; and

• Inflow rates through the sides and floor of the trenches / mine pits.

A representative seepage cross-section (Figure 8-1), location presented on Figure 8-2, was used in the predictive modelling. The model extent includes areas of up to approximately 8 km from the proposed mining. This was considered sufficiently far such that the model boundary conditions (applied at the edges of the model) do not impact on the model results.

Figure 8-1 SW - NE Cross-Section across the proposed trench and highwall mining


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8.2 Model Parameters

8.2.1 Aquifer Hydraulic Conductivity

Aquifer hydraulic properties (hydraulic conductivity), compiled from a number of groundwater studies in the area, were used to calibrate the model. Table 8-1 provides a summary of the aquifer hydraulic parameters compiled during the modelling.

Table 8-1 Aquifer Hydraulic Parameter Summary

Data Source Bore Formation Hydraulic conductivity (m/day)

Comment

AGE(2011) Dysart Coal Project

MB04b S Coal Seam 0.09 to 1.60 Falling head tests

URS (2009) Caval Ridge EIS

Pz07s Alluvium 0.269 Values from slug tests performed on site monitoring bores. Analyses presented for Bouwer-Rice and Hvorslev method. The coal seams encountered at Caval Ridge are the same as those encountered at the Dysart East project site

Pz08s Alluvium 0.088

Pz02 Basalt 0.005

Pz03s Basalt 0.082

Pz06s Basalt 0.138

Pz01 D04 coal seam 0.130

Pz03d D04 coal seam 0.590

Pz04 Q coal seam 0.325

Pz05 D04 coal seam 0.033

Pz06d P02 coal seam 0.079

Pz07d Q01 coal seam 0.330

Pz09 P08 coal seam 0.160

Pz10 H08 coal seam 0.036

Pz11d P08 coal seam 0.037

Pz08d Sandstone interburden 0.034

Arrow Energy model parameters (2011)

Triassic sediments 0.005 Values based on assessment of properties used in other groundwater models in the region

Rangal Coal Measures 0.050

Fort Cooper Coal Measures 0.050

Moranbah Coal Measures 0.010

Back Creek Group 0.005

The hydraulic conductivity values included in the model, for the “best fit” base case model calibration are included in Table 8-2.

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Table 8-2 Model Aquifer Hydraulic Parameter for Base Case

Unit Horizontal (Kh) Hydraulic

Conductivity (m/day)

Kz / Kh ratio Vertical (Kz) Hydraulic

Conductivity (m/day)

Comment

Tertiary sediments 0.30 0.1 0.030

Interburden material 0.01 0.1 0.001 Value taken from testing undertaken at site and from other mines

Coal seams 0.18 0.1 0.018 Average value from testing undertaken at site, and from data available from equivalent coal seams

The modelling assumed at ratio of 0.1 between vertical hydraulic conductivity (Kz) and horizontal hydraulic conductivity (Kh). This value is unknown from field testing; however, sensitive analysis has shown that changes in the Kz/Kh ratio can have a profound effect on the modelled rates of inflow to the mine workings. The impact on pit inflow rates of changes in vertical anisotropy are discussed in Section 8.5.

8.2.2 Aquifer Storage

Seep/W represents the water content and drainage properties of different geological materials using volumetric water content. This concept considers:

• The maximum value for total water content is the same as the total porosity of the unit;

• Total porosity is comprised of specific yield and specific retention;

• The difference between the maximum and minimum volumetric water content is the specific yield (drainable yield) of the unit; and

• Free-draining material (such as gravel) drains at a lower matric suction force than clay, and the transition between fully saturated and fully drained will occur quickly (i.e. the curve will be steep).

Seep/W only considers specific yield and the rate at which drainage is allowed to occur. In other words, the starting porosity (maximum volumetric water content) is not important – it is only the total drainable yield and the rate of drainage (in response to suction forces) that is considered by the model.

Sensitivity analysis conducted during modelling indicates that the model was relatively insensitive to changes in specific yield (Sy) for scenarios that did not include highwall mining (HWM). However for scenarios that did include HWM the model was relatively sensitive to changes in Sy of the interburden material as the majority of water reporting to the HWM holes is derived from the strata above the coal seam (refer to JBT 2013a)

The storage properties utilised in the model are summarised in Table 8-3.

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Table 8-3 Model Storage Values

Unit Specific Yield (Sy) Specific Storage (Ss)

Tertiary / Quaternary sediments 0.05 Not applicable

Permian coal seams 0.05 8.6 x 10-6 / m

Permian interburden material 0.02 8.6 x 10-6 / m

8.3 Model Boundary Conditions

8.3.1 Recharge

A rainfall recharge rate of 2 % of the mean annual rainfall (600 mm/year) was included in the model.

Recharge was not applied to the initial steady-state model as the starting phreatic surface was derived through the use of boundary conditions at the edges of the model set at a distance of approximately 8 km from the mine workings.

8.3.2 Initial Groundwater Levels

The initial steady state groundwater levels were generated across the model domain by applying fixed heads at the east and west boundaries of the model, with heads set at 160 m AHD. This initial head was selected based on available groundwater level data (Section 6.5) and represents the groundwater level just below the base of Tertiary sediments at the location of the model section (Figure 8-2).

8.3.3 Seepage Areas

Seepage though the pit walls and the HWM holes was simulated in the model using the Seep/W boundary condition known as a potential seepage face boundary. This boundary is a flux boundary with total flux (Q) set at 0 m/day. Flux across the boundary can then be measured via the use of flux sections, which measure the rate of flow across the flux section per unit width (1 m) in the model.

8.3.4 Evaporation

Annual average evaporation is 2,025 mm/year (Section 4.2). It is common to apply a pan factor to average evaporation figures to account for the observation that evaporation from a natural environment is generally less than that measured at a Class A evaporation site (where the shallow depth and construction of the apparatus contributes to a higher rate of evaporation than would occur in the natural environment).

To simulate changes in evaporation rate with depth of mining, evaporation was applied in the model as a percentage of total pan evaporation as shown in Table 8-4.

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Table 8-4 Evaporation rates applied in the model

Cut No. Average Mine Depth (mbgl) % of Pan Evaporation

Cut 1 72 90

Cut 2 123 83

Cut 3 155 75

Cut 4 182 68

Cut 5 221 60

mbgl = metres below ground level

8.4 Representation of Mining

Figure 8-1 shows detail from the Seep/W model in the area of the test pit (Figure 8-2 presents the section location). The features evident from Figure 8-1 include:

• The pit has been excavated to full depth (by applying the properties of a void to the region where the pit exists);

• Material was removed from the model in 5 stages to represent the progressive deepening of the mine over time. A sensitivity analysis was undertaken to investigate the impact on pit inflow rates of the removal of material at different rates (to achieve full mine depth in 1 year, 2 years and 4 years);

• The location and extent of the HWM holes. The modelled length of the HWM holes is 300 m on the highwall side of the pit. On the south-west (low wall) side in the pit the length of the HWM hole is 300 m except for cases where the length of the HWM hole is limited to a lesser length by the MLA boundary or the location of the Lake Vermont Spur Railway (i.e. HWM does not extend beyond the MLA boundary or the location of the Lake Vermont Spur Railway).

The Seep/W model represents a single slice of 1 m width through the test pit. Normally the inflow results (which are obtained for a 1 m width of face) are then multiplied by the pit length to obtain an estimate for total pit inflow. The calculated rates of pit inflow are presented in Section 8-5.

8.5 Pit Inflow Estimates

8.5.1 General

Seep/W presents inflow calculations per unit width (i.e. 1 m) width of model. For the model section shown in Figure 8-1 the rate of inflow is calculated from:

• The pit walls;

• The pit floor; and,

• Each of the HWM holes shown on the figure.

In Figure 8-1 the light blue lines represent seepage face boundary conditions. As the coal is removed from each zone (represented by a HWM hole) the seepage face boundary conditions were applied to the upper, lower, and end surfaces of the HWM hole (with the HWM holes

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open at the pit face). The rate of seepage into each HWM hole was calculated via the use of flux sections which are placed around each HWM hole.

The HWM holes mimic large diameter horizontal drains, which capture water from the coal seams as well as water induced from the interburden between the seams. The rate at which water is released from the interburden is a function of the vertical anisotropy of interburden material, i.e. the ratio between the vertical hydraulic conductivity (Kz) and the horizontal hydraulic conductivity (Kh).

The Kz/Kh ratio has a marked impact on the rate of drainage of the interburden sediments, and thus the estimates of groundwater ingress. A range of vertical anisotropy was considered during the modelling.

8.5.2 Sensitivity Analysis - Vertical Anisotropy

In order to test the sensitivity of pit inflow calculations to changes in vertical anisotropy the model was run (using the hydraulic parameters shown in Tables 8-2 and 8-3) using three different vertical anisotropy ratios:

• Kz/Kh = 1 (vertical and horizontal hydraulic conductivity is the same). This scenario is considered unrealistic, but is presented for comparative purposes;

• Kz/Kh = 0.1 (vertical hydraulic conductivity is a factor of 10 lower than the horizontal hydraulic conductivity). This is the default value that is generally applied to groundwater flow models; and

• Kz/Kh = 0.01 (vertical hydraulic conductivity is a factor of 100 lower than the horizontal hydraulic conductivity). This is judged to be a low value with respect to groundwater modelling; however results from site exploration drilling indicate that the interburden is generally dry, therefore a low value for Kz/Kh may be applicable in some areas, particularly in relation to calculated groundwater inflow rates.

The results of the sensitivity analysis are presented below in Table 8-5.

Table 8-5 Calculated Pit Inflow Rates based on Varying Vertical Anisotropy

Time (Years) Pit Depth (mbgl) Calculated Pit inflow rates (L/s) per 300 m wide mining block*

Kz/Kh = 1 Kz/Kh = 0.1 Kz/Kh = 0.01

0.2 72 19.1 -1.8** -6.0

0.4 123 19.5 1.9 -4.3

0.6 155 20.3 4.4 -3.1

0.8 182 19.2 8.6 -0.6

1 220 20.4 12.8 2.6

5 220 6.4 5.2 -1.4

10 220 4.7 1.8 -2.0

20 220 3.2 0.6 -2.4

* Taking into account evaporation ** Negative values (in red) indicate that the rate of evaporation exceeds inflow (i.e. net rate of inflow is zero)

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For comparative purposes the model results, which are generated per 1 m width of face, have been multiplied by 300 (modelled width) to demonstrate the variability in predicted inflow rates over the operational area of mining. In summary:

• For Kz/Kh ratio = 1, the calculated pit inflow rate is approximately 20 L/s for all model cuts up to the full pit depth, with pit inflow rates reducing progressively up to 5 years after mining. This scenario is considered unrealistic as these rates of inflow are generally not seen for Bowen Basin open cut coal mines;

• For Kz/K/h ratio is 0.1 the rate of water ingress increases progressively with depth up to a total inflow rate of almost 13 L/s at 12 months, when full mine depth is achieved. For the first model cut (pit depth = 72 m) the rate of inflow is exceeded by the rate of evaporation, so that the net inflow is zero. In Table 8-5 the inflow results are presented as calculated inflow rate minus evaporation. For cases where evaporation exceeds inflow the net inflow result is a negative number. This is presented for review purposes (with negative values shown in red), even though in practice the actual rate of inflow should be taken to be zero.

• For Kz/Kh ratio is 0.01 the rate of inflow is exceeded by the rate of evaporation for all model cuts except cut 5, where full mine depth is achieved after 12 months. Based on observations from other Bowen Basin mines it is judged that this scenario is unlikely, as it is normally the case that some volume of pit inflow is encountered for mines exceeding 200 m in depth.

Figure 8-3 shows the modelled phreatic surface for each of the vertical anisotropy scenarios described above. Three phreatic surfaces are shown on each model figure, representing the modelled position of the phreatic surface at different model times:

• The initial phreatic surface, which is shown as a line below the interface between the Permian coal measures and the overlying Tertiary/Quaternary deposits. The hydraulic properties of the Tertiary/Quaternary deposits are therefore only considered in the model with respect to the rate at which the sediments will transmit recharge water to the underlying Permian coal measures;

• The phreatic surface at 12 months, i.e. the period at which the mine achieves full depth; and

• The phreatic surface at 5 years after commencement of mining (4 years after the mine achieves full mine depth).

From review of Figure 8-3 the following observations are made:

• For Kz/Kh ratio of 1 the HWM holes fully drain the interburden material within the mining area and result in a lowered phreatic surface at distance from the mine;

• For Kz/Kh ratio of 0.1 the interburden between the HWM holes is almost fully drained after 12 months and the region within the HWM holes is fully dewatered after 5 years. The phreatic surface is lowered to a lesser degree than is the case for the Kz/Kh = 1 scenario;

• For Kz/Kh ratio of 0.01 the phreatic surface is maintained within the interburden between the HWM holes after 12 months and the phreatic surface is impacted to a much lesser degree than for the scenarios described above. This results in a much lower rate of calculated pit inflow than the other modelled scenarios, to the degree where the rate of pit

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inflow is exceeded by the rate of evaporation for all model times except 12 months after commencement of mining (when the mine achieves full depth).

Figure 8-3 Modelled Phreatic Surface at Different Kz/Kh Ratios

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8.5.3 Sensitivity Analysis - Time Taken to Achieve Full Mine Depth

The mining schedule is relatively complex compared to open-cut operations where the coal is progressively removed via conventional truck and shovel or dragline methods.

Review of the mining schedule indicates that full mine depth is achieved in different areas at rates between 1 and 4 years, but generally at rates between 2 and 4 years. The impact on pit inflow rates of mining to full depth at different rates is shown below in Table 8-6.

Table 8-6 Calculated Pit Inflow Rates for Varying Time to Achieve Full Mine Depth*

Pit Depth (mbgl)

Time Taken to Achieve Full Mine Depth (Years)

1 Year 2 Years 4 Years

Time (Years) Inflow Rate (L/s)



72 0.2 -1.8 0.4 -2.6 0.8 -3.1

123 0.4 1.9 0.8 0.9 1.6 -0.1

155 0.6 4.4 1.2 3.2 2.4 1.1

182 0.8 8.6 1.6 6.1 3.2 3.4

220 1 12.8 2 8.8 4 5.3

220 5 5.2 5 3 5 2.2

* Inflow rates (L/s) per 300 linear metres m. Negative values (in red) indicate that evaporation exceeds inflow (i.e. no net inflow rate)

In summary, mining to full pit depth at a slower rate results in a lower peak inflow rate, which is generally achieved when the mine reaches full depth. With a slower rate of mining to full depth the peak inflow rate is also lower; this is because with a slower rate of mining the HWM holes have more time to lower the phreatic surface in the area of the mine. This has the effect of reducing the hydraulic gradient, which in turn reduces the rate of pit inflow as the mine progressively deepens.

8.5.4 Estimated Rates of Groundwater Ingress

The groundwater ingress estimates were based on:

• Aquifer hydraulic properties as presented in Tables 8-2 and 8-3;

• A vertical anisotropy (Kz/Kh) ratio of 0.1; and

• Adopting the provided mining schedule (Figure 7-2).

Pit inflow calculations are presented in Table 8-7. The assumptions relating to mining schedule for each year are presented in the comments section of the table. Inflow rates are calculated for the southern, middle, and northern portions of each pit. These inflow rates are based on the modelled inflow rates for different pit depths and rates of mining, as presented in Table 8-6.

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Table 8-7 Estimated Groundwater Ingress Rates

Year

Southern Pit Northern Pit Total (L/s)

Comment Sth Mid Nth Sth Mid Nth

1 0 0 0 0 0 0 0 Operation of Box Cut

2 2 0 0 0 0 0 2 Mining occurring in southern third of south pit HWM well advanced in P14 Seam, just commencing in H162 Seam

3 7 0 0 0 0 0 7 Mining occurring in southern third of south pit HWM well advanced in H161 seam and commencing in H152/H151 Seams

4 11 0 0 0 0 0 11 Mining occurring in southern third of south pit to full depth HWM well advanced in D52 Seam

5--7 4 2 0 0 0 0 6 Mine at full depth in southern third of south pit HWM advanced to P07 seam in middle third of south pit In-pit dumping commenced over box-cut area

8-9 0 4 2 0 0 0 7 HWM completed in southern third of south pit Mine is at full depth in middle third of south pit - HWM occurring within D301 Seam HWM has advanced to the depth of the P14 Seam in the northern third of the south pit

10-11 0 0 4 0 0 3 7 HWM in the northern end of south pit has progressed to the H161 Seam Dumping in the southern pit has progressed to a point where approximately 500 m of the northern end of the pit remains open HWM in the northern pit has progressed to a point where approximately 500 m of pit is open and HWM has advanced to the P071 seam

12-14 0 0 2 0 2 3 7 HWM at full depth in the northern third of the south pit HWM in the northern third of the north pit has advanced to the H161 Seam HWM as advanced to the P08 Seam in the middle third of the north pit

15 0 0 0 0 0 9 9 HWM mining complete in the southern pit and the pit has been dumped over HWM has advanced to base of mine (D301 Seam) in the northern third of the north pit

16-17 0 0 0 0 2 4 6 HWM mining complete in the southern pit and the pit has been dumped over HWM has advanced to base of mine (D301 Seam) in the northern third of the north pit HWM has progressed to the H162 Seam in the middle third of the north pit HWM has progressed to the P08 Seam in the southern third of the north pit

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Year

Southern Pit Northern Pit Total (L/s)

Comment Sth Mid Nth Sth Mid Nth

18-20 0 0 0 1 4 2 7 HWM is complete in the northern third of the north pit and in-pit dumping has commenced HWM has advanced to base of mine (D301 Seam) in middle third of north pit HWM has advanced to H152 Seam in southern third of north pit

21 0 0 0 4 0 0 4 HWM is finishing in northern third of north pit HWM has been completed in southern and middle and southern thirds of the north pit, and these areas have been dumped over to a point where only a final void remains.

In summary, the predicted mine inflow rates vary between 2 and 11 L/s, however for the majority of the mining period the inflow rates are within the range of 6 to 8 L/s. These estimated ingress rates were converted to ingress volumes per annum for consideration in the Mine Water Balance. These data are included in Table 8-8 and presented in Figure 8-4.

Table 8-8 Estimated Total Ingress Estimates (annual volumes)

Year Southern Pit Northern Pit Total Ingress

Total Ingress

Sth Mid Nth Sth Mid Nth L/s per annum

1 0 0 0 0 0 0 0 0

2 2 0 0 0 0 0 2 63,072 m³

3 7 0 0 0 0 0 7 220,075 m³

4 11 0 0 0 0 0 11 346,896 m³

5 4 2 0 0 0 0 6 189,216 m³

6 4 2 0 0 0 0 6 189,216 m³

7 4 2 0 0 0 0 6 189,216 m³

8 0 4 3 0 0 0 7 220,075 m³

9 0 4 3 0 0 0 7 220,075 m³

10 0 0 4 0 0 3 7 220,075 m³

11 0 0 4 0 0 3 7 220,075 m³

12 0 0 2 0 2 3 7 220,075 m³

13 0 0 2 0 2 3 7 220,075 m³

14 0 0 2 0 2 3 7 220,075 m³

15 0 0 0 0 0 9 9 283,824 m³

16 0 0 0 0 2 4 6 189,216 m³

17 0 0 0 0 2 4 6 189,216 m³

18 0 0 0 1 4 2 7 220,075 m³

19 0 0 0 1 4 2 7 220,075 m³

20 0 0 0 1 4 2 7 220,075 m³

21 0 0 0 4 0 0 4 126,144 m³

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Figure 8-4 Estimated Groundwater Ingress over time

The predicted mine inflow is an estimate total volume of 4.1 Gigalitre (GL) over a 21 year life of mine (an average of 200 megalitres per year (ML/year)). The mine dewatering is projected to result in a decline in the groundwater level within and adjacent to MDL 450 (MLA 70507). The resultant drawdown can result in decreased groundwater resources, and is considered in Section 9.

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9 POTENTIAL IMPACTS

9.1 Groundwater Level Drawdown

Groundwater drawdown impact thresholds are selected on the basis of impact requirements of the Water Act 2000 (section 362), where bore trigger thresholds are defined, for an aquifer, as a decline in the water level in the aquifer of 5 m (for a consolidated aquifer) and 2 m (for an unconsolidated aquifer). Model results are presented as distance from the edge of mining (edge of HWM holes) of the extent of both 2 m and 5 m drawdown.

The predicted extent of drawdown around the mine workings is included in Table 9-1.

Table 9-1 Estimated extent of 2 m and 5 m Drawdown

Mining Stage South-West (Up-Dip/ Low wall side)

North-East (Down-Dip/ Highwall side)

5 m 2 m 5 m 2 m

End of Mining (Year 21) ~ 3,9 km ~ 4,3 km ~ 4,5 km ~ 5,0 km

20 Years after mining Up to 4,9 km Up to 5,3 km Up to 5,5 km Up to 6,0 km

The predicted drawdown extents indicate that:

• The majority of groundwater impact occurs by the end of mining (year 21). The modelled extent of impact then extends relatively slowly over the next 20 years as the system approaches steady-state (Table 9-1);

• Drawdown extends slightly further in the north-east (down-dip) direction than in the south-west (up-dip) direction. This occurs because:

– The HWM holes extend to a greater depth below surface on the highwall (down-dip) side of the mine, which draws the phreatic surface down to a lower level on the highwall side of the operation; and

– The coal seams act as conduits for groundwater flow due to the permeability contrast between the coal seams and the interburden. The coal seams are progressively truncated as they sub-crop on the south west (low wall) side of the model, which acts to limit the extent of drawdown.

9.2 Impacts on Existing Groundwater Users

Based on the predicted drawdown around the mine workings there is the potential to impact on groundwater levels in registered groundwater bores (Section 6.6.1) within an approximate 6 km radius of the mine (Figure 9-1). These bores are considered “at-risk” bores and require assessment.

In order to establish the potential for the mining operation to impact existing groundwater users, it is recommended that a census be undertaken of landholder bores on properties within and adjacent to the proposed mining operation. The bore census should seek to establish details such as bore construction (drilled date, bore depth, screened interval etc.) bore status (e.g. in use, abandoned, destroyed etc.) pumping equipment (installed depth and type), water level (historic and current), water quality, etc.


Figure:

A442627233-g-054.cdr 17-02-2014DCVH

REGISTERED GROUNDWATERBORES WITHIN PROJECTED

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Note that it is not considered necessary to include bores that are located on the far side of other mining operations (e.g. bores 90017 and 90016, which are located to the south-west of Norwich Park mine) or within the footprint of other mining operations (e.g. bore 43639, which is within the footprint of Saraji Mine), Figure 9-1.

9.3 Potential Environmental Impacts

The following observations are made with respect to the potential for the proposed mining to impact the environment (e.g. groundwater dependent ecosystems):

• The surface water system in the area is ephemeral; however, the alluvium is recorded on site as continually being dry. Monitoring bore DMB04a, drilled through alluvium between 2 and 13 mbgl and completed at the base of Tertiary at 22 mbgl, was gauged between April 2012 and June 2013. This bore was either dry or had a groundwater level at 19 to 20 mbgl (below the alluvium) (JBT 2013a).

Therefore the Quaternary alluvium is interpreted to be dry, and the water level in the underlying Tertiary sediments is interpreted to be below the level required to support groundwater dependent ecosystems;

• The groundwater level in the coal measures at the location of bore DMB04b has been recorded between April 2012 and June 2013 to be approximately 31 mbgl, i.e. approximately 9 m below the base of Tertiary/Quaternary sediments.

Based on these data it is concluded that the Tertiary/Quaternary sediments are not in hydraulic connection with the underlying coal measures across the project (though the Tertiary/Quaternary sediments may recharge the underlying coal measures via downward leakage following rainfall events that directly recharge the Tertiary/Quaternary sediments).

It is, therefore, concluded that the mining operation will not impact on any potential groundwater dependent ecosystems within the alluvium as the alluvium is dry within the project area and the regional groundwater levels are recorded to be at a significant depth below the base of the alluvium.

Should drawdown occurs in the regional groundwater system due to mining, the drawdown is unlikely to induce a greater rate of drainage from the alluvium (compared to pre-mining conditions) during times when the alluvium does contain water (e.g. following significant rainfall events and creek flow, where the alluvium is directly recharged).

9.4 Impacts on Groundwater Quality

The groundwater quality of the Permian units is brackish to saline and not suitable for human consumption or irrigation (Section 6.4). During mining operations, groundwater quality within aquifers surrounding the site is not expected to change from pre-mining conditions. This would be a result of all the project water and waste storage facilities infrastructure being designed, constructed, and managed to ensure little or no potential of seepage. In the event that groundwater contamination did occur contaminant migration off site in the groundwater will not occur. This is expected as during mining operations, groundwater will be continually extracted from the trench / open cut workings to ensure a safe working environment. This extraction and the HWM holes drainage will create a depression in the potentiometric (groundwater) surface around the workings such that the net movement of groundwater is towards the workings

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during mine operation. This will prevent the movement of water that may have been impacted by mining from moving away from the mine operation area and into the surrounding aquifers. The resultant drawdown, changing groundwater flow patterns, effectively limits the potential for contaminant plumes to migrate off site via groundwater.

Groundwater quality away from the influence of the project will not deteriorate as these resources will continue to receive recharge via the same processes that occurred pre-mining.

Groundwater quality data (with respect to major anions and cations and dissolved metals) indicate that groundwater in the alluvial aquifers and interburden is of similar quality when compared to the coal seam aquifers of the Moranbah Coal Measures. Hence, any inadvertent mixing of groundwater (during and post mining) by induced downward movement from the overlying units is unlikely to result in a deterioration of groundwater quality in the Permian aquifers.

Another potential source of contamination for groundwater is through contact with mine waste materials (resulting from the coal washing) which may be acid forming or leach salt or metal contaminants to groundwater. A geochemical assessment of the coal and mine wastes (waste rock and tailings) was undertaken for the project (URS, 2014). The study indicates that the overburden (excavated for mine access) and rejects generated by the proposed mining and coal processing operation is predominantly geochemically benign. Any possible seepage and /or surface run-off is expected to be slightly alkaline and have low-to-moderate salinity following surface exposure. Mine waste material is unlikely to generate acid given the lack of oxidisable sulphur content, excess acid neutralising capacity and existing alkaline pH of these materials. As the direction of groundwater flow will be towards the mine workings, the buffering capacity of the groundwater is expected to neutralise any oxidation products of the coal seams due to mine dewatering, and any potential for the development of acid mine drainage is low.

The waste rock dumps, waste placement areas, CHPP and coal stockpiles are located over the relatively saline aquifers of the Permian formations (Moranbah Coal Measures or Fort Cooper Coal Measures). Thus any potential seepage or runoff is unlikely to result in a marked alteration to groundwater quality of the underlying Permian formations.

The quality of the groundwater in the shallow Cainozoic groundwater resources that may exist within the project footprint (i.e. alluvium and Tertiary sediments) have the potential to be impacted by spills and seepage from the CHPP water and waste storage areas where these are in sufficient quantities to leach through the soils to groundwater. Any spills from these areas are typically localised and not regionally significant in terms of groundwater impacts. The risks of groundwater contamination from chemical or fuel spills (fuel storage or workshops) will be minimised by storage and handling of fuels, oils and other chemicals in accordance with Australian standards and requirements of Material Safety Data Sheets. The design of storage and handling facilities will provide full containment, and procedures for immediate clean-up of spills will be available. These measures are standard practice or a legislated requirement at mine sites. Areas of hydrocarbon and chemical storage will have spill control measures in place and a regular inspection regime will be required in order to monitor activities that could potentially lead to contamination of groundwater. Any accidental spills will be assessed on a case-by-case basis and remediated, which may include excavation and disposal of any contaminated soil, in accordance with NRM requirements.

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During mine operation, groundwater quality within aquifers surrounding the mine areas will continue to be suitable for the same purposes applicable during the pre-mining period. The groundwater quality within the aquifers surrounding the project area will be monitored to ensure no marked deterioration in groundwater is occurring as a result of the proposed mining activities.

9.5 Reduced Recharge

Compression and/or sealing of the ground surface associated with the construction of roads and CHPP infrastructure is not expected to greatly alter the permeability of strata immediately beneath the site and, as such, will not markedly reduce rainfall recharge of the underlying aquifers. Works will be limited in the vicinity of the creek, further limiting potential impacts on the Quaternary alluvial aquifer.

9.6 Subsidence

As detailed in Section 7.1.3, the potential for subsidence as a result of groundwater extraction is negligible as:

• The removal of the target coal seams will reduce the weight of rock overlying the aquifer, reducing the impacts of the reduction of upward pressure;

• The confined aquifers do not remain confined as they, the coal seam aquifers, are to be dewatered; and

• The shallow depth and relatively small mine footprint.

9.7 Cumulative Impacts

Cumulative groundwater level impacts (i.e. the cumulative impact of drawdown from the proposed project with existing mining operations) are assessed as follows:

• Three open cut coal mines are located within 10 km of MDL 450 (MLA 70507) (refer Figures 9-2). The mines include Norwich Park (3 km south/ south-west), Saraji (4 km north-west), and Lake Vermont (6 km north);

• The existing mines have all been operating for a number of years. Details of groundwater level impacts of the above mines are unknown; however, based on the configuration of the mines it is possible that MDL 450 (MLA 70507) is located within an area that has already been impacted by the cones of depression from the existing mines;

• Groundwater level data from registered bores in the EHP database indicate that the groundwater level in the coal measures is historically similar to the groundwater level measured from site groundwater monitoring bores such as DMB04b. For example water levels in the coal measures are recorded as:

– DMB04b (site monitoring bore) – standing water level (SWL) of 31.99 mbgl in February 2013;

– Bore 43639 – SWL of 29.5 mbgl in August 1973 (Figure 9-1);

– Bore 89469 – SWL of 36 mbgl in September 1992 (Figure 9-1); and

– Bore 44625 – SWL of 36.6 mbgl in August 1973 (Figure 9-1);


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• Therefore groundwater levels in the coal measures do not appear to have been significantly impacted by the presence of coal mines in the area, which suggests that the extent of impact from the coal mines may be less than would be predicted from groundwater modelling.

It is acknowledged that groundwater models are often conservative (i.e. they over-estimate the extent of impact) when model predictions are compared to long-term post-mining groundwater level data and in practice steady-state impacts are often achieved for a particular groundwater system within tens of years rather than hundreds of years. One possible reason for this is that models assume a continuous porous medium, whereas within consolidated strata groundwater occurrence and movement more generally occurs within the secondary porosity of fracture systems which tend to compartmentalise groundwater and act to limit the rate and extent of impact. In addition, even if fracture systems are hydraulically continuous (in a regional sense), the volume of rock that contributes to groundwater storage and movement is less for a fractured system than for a continuous porous medium where groundwater occurrence and flow occurs through all pore spaces within the rock volume.

It is therefore concluded that the impact from mining will therefore be best observed through the use of groundwater monitoring bores, with impacts on existing private groundwater bores determined via bore surveys and ongoing water level monitoring.

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10 RISK ASSESSMENT

10.1 Methodology

The potential hazards and risks were identified through the use of a preliminary hazard analysis (PHA). The PHA took into consideration the AS/NZS ISO 31000:2009 Risk management – Principles and guidelines and IEC/ISO 31010 Risk management – Risk assessment techniques.

The PHA was carried out in accordance the New South Wales ‘Hazardous Industry Planning Advisory Paper 6: Hazard Analysis (Consultation Draft) 2008’ (DoP 2008) and the probability criteria matrix technique detailed in the IEC/ ISO 31010 Risk management – Risk assessment techniques.

The assessment outlines the implications for, and the impact on, the surrounding land uses. The PHA incorporates:

• Relevant hazards (minor and major);

• The possible frequency of the potential hazards, accidents, spillages and abnormal events occurring;

• Indication of cumulative risk levels to surrounding land uses;

• Life of any identified hazards;

• The effects and rate of usage of the dangerous goods and hazardous substances to be used, stored, processed or produced by the project; and

• The type of machinery and equipment used.

Potential incident scenarios during the project were identified through consideration of:

• The range of activities carried out and facilities present during the construction, operation, and decommissioning phases. These included construction activities, energy supply, coal mining, transport, and wastewater management.

• The range of potentially hazardous incidents that might be associated with each of the activities/facilities identified in association with the project.

Having identified the range of hazards potentially occurring as a result of project activities, the following matters were considered for each hazard:

• Appropriate controls and mitigation factors expected to be put in place for the management of each hazard. These may include prevention and response measures.

• The consequences of each of the hazardous incidents if they were to occur. Consequences might include direct impacts of incidents and the potential for propagation and secondary incidents. Assessment of the severity of the consequences takes into consideration the proposed controls.

• Possible causes and the probability of these causes occurring and leading to the hazardous incident. The probability of each hazardous incident occurring takes into consideration the proposed controls. This information was then tabled to prioritise the risks and evaluate these levels against the concept of practicable.

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• Where an extreme or high risk was identified, appropriate controls and mitigation measures were identified and the hazardous incident reassessed with these controls in place.

10.1.1 Risk Analysis Criteria

The risk assessment matrix, shown in Table 10–1, is based on the probability criteria matrix technique detailed in the IEC/ISO 31010 Risk management – Risk assessment techniques.

A likelihood of occurrence was assigned to each identified hazardous incident based on definitions described in Table 10–2. The contribution of preventative and protective management controls were taken into account when assessing the likelihood of occurrence and potential consequence from each hazardous incident. The probability of occurrence used for this risk assessment is based on the then AS 4360-2004 Risk Management. The risk levels denote residual risk.

The consequences assessed include both threats to health and safety of the public and the workforce and to the natural environment based on definitions shown in Table 10–3. Where a hazardous incident may have several outcomes, each potential outcome was assessed in turn. The severity classes for health and safety type outcomes are based on the then AS 4360-2004 Risk Management, while those for the threat to the natural environment are based on common environmental risk management consequence categories.

Table 10-1 Risk Assessment Matrix

Like

lihoo

d

Consequences

1 2 3 4 5

A High High Extreme Extreme Extreme

B Moderate High High Extreme Extreme

C Low Moderate High Extreme Extreme

D Low Low Moderate High Extreme

E Low Low Moderate High High

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Table 10-2 Likelihood of Occurrence for Hazardous Incidents

Likelihood Rank

Descriptor Description

A Almost certain 80 %chance of occurring; may occur more than once per year; happens often

B Likely 50 % chance of occurring; may occur once in a few years; easily happens

C Possible 20 % chance of occurring; may occur once in 5 years; has happened before

D Unlikely 10 % chance of occurring; may occur once in 10 years; is considered possible

E Rare 2 % chance of occurring; may occur once in 50 years; is considered conceivable

Table 10-3 Consequence Classes for Environmental Impact

Consequence Rank

Descriptor Public / Workforce Health and Safety

Environmental Severity

5 Catastrophic Multiple fatalities (2 – 20), or significant irreversible effects to >50 persons

Unplanned serious or extensive impact on ecosystem or threatened species

4 Major Single fatality or severe irreversible disability (>30 %) to one or more persons

Unplanned major impact on ecosystem or threatened species

3 Moderate Moderate irreversible disability or impairment (<30 %) to one or more persons. Days lost

Unplanned moderate impact to ecosystem or non-threatened species

2 Minor Objective but reversible disability/impairment. Medical treatment injury

Unplanned minor impact to non-threatened species or their habitat

1 Insignificant Low level short-term inconvenience or symptoms. Not medical treatment

Unplanned low level environmental impact

The summary of potential impacts, risks and mitigation measures is included in Table 10-4.

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10.2 Summary of Impacts to Water from Project Activities

Table 10-4 Groundwater Risk Assessment

Potential Impact Pre-mitigation Risk Mitigation Residual Risk

Likelihood Consequence Risk Likelihood Consequence Risk

Potential Impacts during development and operations

Drawdown of Permian groundwater levels as a result of mine dewatering.

Almost certain Minor High Very few groundwater users and no surface water discharge identified near the study area. Mitigation includes a groundwater monitoring network (VWPs) to allow for routine monitoring of water levels throughout project lifecycle. Make good approach will be applied as necessary. It is considered that the groundwater levels will recover over time.

Almost certain Insignificant High

Drawdown of Quaternary / Tertiary groundwater levels as a result of mine dewatering.

Possible Minor Moderate The overlying material needs to be saturated and in hydraulic connection with the underlying confined aquifers. In reality, due to the short periods over which the aquifers are actually saturated and the perched nature of these unconfined aquifers, the potential for induced drawdown will be much less than predicted. Mitigation includes a groundwater monitoring network to allow for routine monitoring of water levels throughout project lifecycle. Make good approach will be applied as necessary.

Unlikely Insignificant Low

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Impacts on groundwater quality

Possible Minor Moderate Baseline studies indicate groundwater quality is not fit for human consumption but is suitable for livestock. Any inadvertent mixing of groundwater during and post mining by induced downward movement from the upper to lower aquifers is unlikely to result in a deterioration of groundwater quality in the Permian aquifers. The groundwater quality within the aquifers surrounding the study area will be monitored to ensure no marked deterioration in groundwater is occurring as a result of the proposed mining activities. Any possible seepage and /or surface run-off is expected to be slightly alkaline and have low-to moderate salinity following surface exposure. Mine waste materials are unlikely to generate acid given the lack of oxidisable sulphur content, excess acid neutralising capacity and existing alkaline pH of these materials. As the direction of groundwater flow will be towards the mine workings, the buffering capacity of the groundwater is expected to neutralise any oxidation products of the coal seams due to mine dewatering, and any potential for the development of acid mine drainage is low. During mine operation, groundwater quality within aquifers surrounding the mine areas will continue to be suitable for the same purposes applicable during the pre-mining period. Groundwater quality away from the influence of the project will not deteriorate as these resources will continue to receive recharge via the same processes that occurred pre-mining. As such, post-mining water quality within all aquifers surrounding the study area is expected to remain similar to pre-mining water quality.

Unlikely Minor Low

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Additional Potential Impacts during development and operations

Compression as a result of groundwater extraction

Rare Moderate Moderate Highwall mining spacing and orientation will be finalised based on geotechnical, rock mechanics, geological structures, and dewatering considerations. Areas of enhanced groundwater potential (such as fractures, faults, and weathering) will be assessed and mining safety considerations employed to reduce instability risks.

Rare Minor Low

Potential Impacts Post-Mining

Long term impacts on groundwater levels

Almost certain Minor High Typically, the mine workings will fill up and groundwater levels will recover over time. The groundwater system will readjust to the new (altered and enhanced) aquifer conditions surrounding and within the mined area with some localised changes to pre-mining characteristics. Groundwater levels and piezometeric pressures within the regional aquifers will, over time, attain a new equilibrium level. This new equilibrium for the groundwater system will have a different potentiometric surface from that which was present pre-mining, owing to the presence of the final void (void remaining at the end of mining the northern pit) and the different hydrogeological parameters (mined out voids in the coal seams). Mitigation includes a groundwater monitoring network (with VWPs) to allow for routine monitoring of water levels throughout project lifecycle.

Likely Minor High

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Impacts on groundwater quality are expected to include a rise in the groundwater salinity within the final void. This will occur as a result of evaporation from the pit resulting in increased salinity.

Almost certain Minor High Groundwater quality within the groundwater units on and adjacent to site are not expected to alter due to induced flow. Groundwater will contribute to water within the final void, which will contain naturally elevated salinity. The groundwater ingress and rainfall runoff will be offset by evaporation resulting in a pseudo steady state water level within the final void over the long term. Salinity will increase due to evaporation but the water within the pit will be at a lower level than the groundwater adjacent to the final void, i.e. the final void will act as a ”sink” which reduces the potential for saline water from the void entering the groundwater and migrating offsite. Groundwater monitoring and revised modelling will be conducted over time to assess groundwater quality and quantity changes due to the final void.

Likely Minor High

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11 GROUNDWATER MONITORING

The existing groundwater monitoring network provides limited information regarding baseline and natural fluctuations within the groundwater resources across the site. This is because several of the bores are drilled dry. In order to best assess site-specific groundwater conditions and predict potential impacts it is recommended that additional groundwater monitoring bores be sited at a number of locations.

Such monitoring bores should be:

• Installed at locations that are adjacent to the pit crest, as well as at distance from the crest in an orientation that creates a line of bores perpendicular to the pit;

• Installed as VWP bores to allow monitoring of a number of vertical intervals (interburden below target coal seam, target coal seam, and overburden above target coal seam);

• Installed in advance of mining to allow monitoring of base line water levels, as well as the rate of water level decline in response to mining; and

• Monitored during mining to provide information on the actual rates of passive drainage vs. predicted rates of passive drainage (in order that geotechnical assumptions relating to the rate of drainage and height of phreatic surface behind the pit face can be assessed).

11.1 Groundwater Monitoring Objectives

The desired outcomes for groundwater management associated with the project are to minimise potential impacts to surrounding landholders and environmental values. These outcomes need to be balanced with coal production requirements.

Effects from mine dewatering (drawdown) are likely to manifest themselves on a more regional scale (up to 6 km radially around the workings). Groundwater quality impacts may occur adjacent to mine water and waste storage facilities but due to drawdown are not predicted to migrate (within groundwater) off site. The monitoring system must be developed to effectively address the potential effects on identified groundwater environmental values (Section 6.7).

The objectives of the groundwater monitoring are to:

• Establish an appropriate monitoring regime, both in space and time;

• Develop a high quality background dataset against which potential impacts can be assessed and gain a better understanding of natural groundwater (level and quality) variability in the region;

• Ensure mining does not detrimentally impact on the availability and suitability of groundwater for agricultural use (stock watering);

• Identify potential impacts from the proposed mining activities with sufficient time to implement management (i.e. make-good agreements, etc.) and/or mitigation measures;

• Water and waste storage facilities to minimise the potential for impact on shallow groundwater aquifers during the life of the mine and after mining ceases;

• Ensure no impact on the major recharge mechanism;

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• Recycle and reuse groundwater intersected during mining for mining activities and operations, so as to limit the need to import or diminish water resources outside of the mine area;

• Enable detection of long-term trends and potential cumulative effects from the project and other existing coal mining operations;

• Generate data against which model predictions can be verified; and

• Obtain high quality (repeatable and representative) data to develop trigger levels and contaminant limits for each aquifer / groundwater unit that could be impacted.

11.2 General Groundwater Monitoring Program

A network of groundwater monitoring bores was previously installed around the project area as shown in Figure 3-1. Additional groundwater monitoring bores and vibrating wire piezometers (VWPs) are recommended (as discussed in Section 11 above).

Further monitoring will be undertaken prior to the commencement of mining to enable the long term monitoring of groundwater levels and groundwater quality, as well as to provide data for updates of the groundwater model.

Routine monitoring during the mining operation will provide early warning of any variation in response of the groundwater system to that predicted. This will enable Bengal Coal to undertake mitigation measures to minimise impact on surrounding groundwater users and the environment, such as the implementation of make good measures. In addition, the groundwater monitoring will enable the identification of any cumulative groundwater level drawdown impacts as a consequence of other mining operations in the area.

The monitoring bores are required to be completed in accordance with the Minimum Construction Requirements for Water Bores in Australia (National Water Commission, 2012), the Water Act 2000, and undertaken by a licensed water bore driller. They must be surveyed for elevation levels of ground surface and monitoring measurement point to allow future groundwater levels to be measured to a consistent, known, datum and allow groundwater sampling as required.

Groundwater level and quality monitoring will be undertaken regularly to enable the detection of seasonal fluctuations and any groundwater level or quality trends or impacts. In turn, the monitoring data (level and chemistry) will be entered into an environmental monitoring database to enable a regular assessment and interrogation to evaluate potential groundwater impacts.

A groundwater monitoring network and program will be developed and implemented for the project to detect any marked change to ground water quality due to activities. This will be consistent with the current suitability of the groundwater for agricultural use (stock watering), and any discharge to surface waters that may occur after significant wet weather events.

Prior to commencement of mining regular monitoring events will be undertaken, across wet and dry seasons, to allow for sufficient baseline data to be compiled to allow for the identification of natural fluctuations in groundwater quality and water levels.

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The monitoring events will record groundwater levels and groundwater quality with analysis of the parameters; pH, electrical conductivity (EC), total dissolved solids (TDS), major cations and anions, nutrients (total nitrogen, nitrous oxides, ammonia, phosphorous), selected dissolved metals (aluminium, arsenic, boron, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, selenium, and zinc), and total petroleum hydrocarbons (for bores monitoring potential fuel spill / seepage sources).

In addition, continuous groundwater level monitoring will be conducted across at least two wet and dry seasons using vibrating wire piezometers automatically recording water levels at regular intervals.

The background groundwater monitoring program will allow for the determination of background groundwater quality, which will be used to determine groundwater contaminant and trigger limits for comparison to the EPP (Water) groundwater quality objectives (Section 2).

On completion of baseline monitoring, groundwater trigger levels, based on the 85th percentile value of groundwater quality results and groundwater contaminant limits based on the 99th percentile of groundwater quality results will be determined.

During mining operations, groundwater monitoring will continue, including:

• Monitored of groundwater levels in standpipe monitoring bores and VWPs.

• Groundwater quality sampling undertaken at least once very wet season and once every dry season.

• Additional monitoring in one or more bores may be undertaken in the event of a significant spill of fuels or other contaminants with potential to cause groundwater contamination.

• Measurement of daily precipitation, evaporation, and mine dewatering volumes will be undertaken through operations.

Groundwater monitoring and sampling will be conducted by a suitably qualified and experienced professional in accordance with the current edition of the EHP Monitoring and Sampling Manual, or subsequent updated versions; and the AS/NZS 5667.11:1998 Australian/New Zealand Standard for water quality – sampling Part 11; guidance on sampling groundwater.

An annual review of the monitoring program will be conducted by a suitably qualified and experienced hydrogeologist. This annual review of the monitoring program will be conducted to evaluate the effectiveness of each monitoring location, to assess where new locations and modifications to the monitoring program may be needed, and to evaluate impacts that may be occurring. These data will, on a regular basis (no longer than three years), be used to validate model predictions.

Post-mining groundwater monitoring will be subject to detailed closure/relinquishment conditions. It is expected that during the operational phase of the project, the groundwater data collected for the region will be comprehensive enough to accurately predict the long term recovery of the aquifers. This will assist in the development and implementation of the closure strategy and the refinement of post-mining groundwater monitoring programs.

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12 REFERENCES

AGE 2004a. Groundwater Depressurisation Assessment, Airstrip South Project – Goonyella, Project No. G1201. Australasian Groundwater and Environmental Consultants Pty Ltd.

AGE 2004b. Groundwater Depressurisation Assessment, Goonyella Lower Seam – Ramp 8, Project No. G1202. Australasian Groundwater and Environmental Consultants Pty Ltd.

AGE, 2010a, Proposed Monitoring Bore Locations – EPC1188 – November, 2010

AGE 2010b, Report on Groundwater Monitoring Program – EPC1188 – Dysart Coal Project, December 2010 ()

AGE, 2011, Draft Report on Dysart Coal Project Bore Completion Report, December 2011

Arrow Energy (2011). Underground Water Impact Report – For Authority to Prospect 1103. Report prepared by Arrow Energy for consultation

Arrow Energy (2013). Underground Water Impact Report – For Authority to Prospect 1031. Report prepared by Arrow Energy for consultation;

BMA (2008) Daunia Coal Project EIS. Chapter 7 – Groundwater;

BMA (2008) Daunia Coal Project EIS. Appendix H - Technical Report: Groundwater Modelling Assessment of Impact of Daunia Coal Mine on Regional Groundwater Aquifers;

Cat, 2011 Factsheet Highwall Mining System, www.mining.cat.com, accessed 13/12/2013

Elliot, L. 1989. The Surat and Bowen Basins. The APEA Journal 402-416.

Fielding, C.R., Falkner, A.J., and Scott, S.G. 1993. Fluvial response to foreland basin overfilling; the Late Permian Rangal Coal Measures in the Bowen Basin. Sedimentary Geology 85 (1993): 475-497

Holla, L., 1987. Surface Subsidence Prediction in the Newcastle Coalfield. Department of Mineral Resources

JBT Consulting 2010. Grosvenor Coal Project Environmental Impact Study Groundwater Impact Assessment, Project JBTO1 007 003.

JBT 2013a, Dysart East Coal Mine Project Test Pit Phase 1 – Water Management Strategy, JBT Consulting May 2013

JBT, 2013b, Stage 1 – Test pit and bulk sample groundwater technical report, JBT Consulting, June 2013

JBT, 2014, Stage 2 Project Groundwater Report, JBT Consulting, January 2014

Matsui, K., Shimada, H., Sasaoka, T., Ichinose, M. and Kubota, S., 2000. Highwall mining system with backfilling, Mine Planning and Equipment Selection, Panagiotou and Michalalopoloulos (eds), Rotterdam

Raymond, and McNeil. 2011. Regional Chemistry of the Fitzroy Basin Groundwater. Brisbane: Department of Environment and Resource Management, Queensland Government.

http://www.mining.cat.com/

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SKM 2009. Isaac Connors Groundwater Project. Report prepared for the Queensland Government Department of Natural Resources and Water.

Sun, H., Shagam, R. and Grandstaff, D. 1999. Land subsidence due to groundwater withdrawal: potential damage of subsidence and sea level rise in southern New Jersey, USA. Environmental Geology 37 (4) April 1999

URS 2009. Caval Ridge Groundwater Impact Assessment. Report prepared or BM Alliance Coal Operations Pty Ltd, 20 March 2009

URS 2012a. Red Hill Project Groundwater Impact Assessment. Prepared for BHP Billiton Mitsubishi Alliance, March 2012. Project No. 42626730

URS. 2014. Draft Mine Waste and Geochemistry Dysart East Coal Project – Environmental Assessment Report. Prepared for Bengal Coal Pty Ltd, January 2014.

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13 LIMITATIONS

13.1 Geotechnical & Hydro Geological Report

URS Australia Pty Ltd (URS) has prepared this report in accordance with the usual care and thoroughness of the consulting profession for the use of Bengal Coal and only those third parties who have been authorised in writing by URS to rely on the report.

It is based on generally accepted practices and standards at the time it was prepared. No other warranty, expressed or implied, is made as to the professional advice included in this report. It is prepared in accordance with the scope of work and for the purpose outlined in the contract 20 November 2013 between URS and Bengal Coal.

The methodology adopted and sources of information used by URS are outlined in this the Report.

Where this report indicates that information has been provided to URS by third parties, URS has made no independent verification of this information unless required as part of the agreed scope of work. URS assumes no liability for any inaccuracies in or omissions to that information.

This Report was prepared between December 2013 and February 2014 information in this report is considered to be accurate at the date of issue and is in accordance with conditions at the site at the dates sampled. Opinions and recommendations presented herein apply to the site existing at the time of our investigation and cannot necessarily apply to site changes of which URS is not aware and has not had the opportunity to evaluate. This document and the information contained herein should only be regarded as validly representing the site conditions at the time of the investigation unless otherwise explicitly stated in a preceding section of this report. URS disclaims responsibility for any changes that may have occurred after this time.

This report should be read in full. No responsibility is accepted for use of any part of this report in any other context or for any other purpose or by third parties. This report does not purport to give legal advice. Legal advice can only be given by qualified legal practitioners.

This report contains information obtained by inspection, sampling, testing or other means of investigation. This information is directly relevant only to the points in the ground where they were obtained at the time of the assessment. The borehole logs indicate the inferred ground conditions only at the specific locations tested. The precision with which conditions are indicated depends largely on the uniformity of conditions and on the frequency and method of sampling as constrained by the project budget limitations. The behaviour of groundwater and some aspects of contaminants in soil and groundwater are complex. Our conclusions are based upon the analytical data presented in this report and our experience. Future advances in regard to the understanding of chemicals and their behaviour, and changes in regulations affecting their management, could impact on our conclusions and recommendations regarding their potential presence on this site.

Where conditions encountered at the site are subsequently found to differ significantly from those anticipated in this report, URS must be notified of any such findings and be provided with an opportunity to review the recommendations of this report.

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Whilst to the best of our knowledge information contained in this report is accurate at the date of issue, subsurface conditions, including groundwater levels can change in a limited time.

Therefore this document and the information contained herein should only be regarded as valid at the time of the investigation unless otherwise explicitly stated in this report.

Except as required by law, no third party may use or rely on, this Report unless otherwise agreed by URS in writing. Where such agreement is provided, URS will provide a letter of reliance to the agreed third party in the form required by URS.

To the extent permitted by law, URS expressly disclaims and excludes liability for any loss, damage, cost or expenses suffered by any third party relating to or resulting from the use of, or reliance on, any information contained in this Report. URS does not admit that any action, liability or claim may exist or be available to any third party.

URS does not represent that this Report is suitable for use by any third party.

Except as specifically stated in this section, URS does not authorise the use of this Report by any third party.

It is the responsibility of third parties to independently make inquiries or seek advice in relation to their particular requirements and proposed use of the relevant property.

Any estimates of potential costs which have been provided are presented as estimates only as at the date of the Report. Any cost estimates that have been provided may therefore vary from actual costs at the time of expenditure.

Documents

7 IMPACT EVALUATION 7.1 Highwall Mining