GROUNDWATER EVALUATION FOR ANGLO-SAXON MINING PROPOSAL PINJIN AREA, WA APRIL 2014 REPORT FOR HAWTHORN RESOURCES LIMITED (Report No. 165-0/14/01)
GROUNDWATER EVALUATION
FOR ANGLO-SAXON MINING
PROPOSAL
PINJIN AREA, WA
APRIL 2014
REPORT FOR
HAWTHORN RESOURCES LIMITED
(Report No. 165-0/14/01)
Rockwater Pty Ltd165.0/14/01
TABLE OF CONTENTSPAGE
1 INTRODUCTION 1
2 REGIONAL DESCRIPTION 1
2.1 Climate and Rainfall 1
2.2 Topography and Drainage 1
2.3 Geology 2
2.4 Hydrogeology 2
3 WATER SOURCES FOR HAUL ROAD AND MINING 3
3.1 Bore PSWB001 (‘Tropicana Road Bore’) 4
3.2 REBECCA BORE 4
3.3 BORES ALONG HAWTHORN’S HAUL ROAD 4
3.3.1 Bedrock 43.4 Bedrock Bores Drilled in 2013 6
3.5 Palaeochannel BoreS 7
3.5.1 South of Pinjin 73.5.2 South-East of Rebecca Bore 7
4 GROUNDWATER TENEMENTS AND LICENCES 7
5 CHEMICAL ANALYSIS OF GROUNDWATER 8
6 MODELLED GROUNDWATER INFLOW TO THE PIT 8
6.1 MODEL Description 8
6.2 Model Parameters and Boundary Conditions 9
6.3 Modelling Results 9
6.3.1 Pit Inflows 96.3.2 Sensitivity Analysis 10
7 FINAL VOID ASSESSMENT 11
8 SUMMARY 11
REFERENCES 12
Tables
Table 1 : Mean Monthly and Annual Rainfall for Edjudina Station (BOM Station No. 12027)
1900-2013 1
Table 2 : Data from Bores and Wells, Pinjin Area (1991) 5
Table 3 : Data from Bores and Wells, Edjudina area, 1980-81 5
Table 4 : Results of Groundwater Exploration Programme Pinjin, November 2013 6
Table 5 : Aquifer Parameters Adopted In Model 9
Table 7: Model-Calculated Groundwater Flows 10
Table 8: Results of Sensitivity Analysis 10
Table 9: Pit Void Water Balance 11
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TABLE OF CONTENTS(Continued)
Figures
1 Locality Plan with Geology
2 Model Calculated Peak Drawdowns (m) Around Planned Pinjin Pit – A Pit
3 Model Calculated Peak Drawdowns (m) Around Planned Pinjin Pit – A and B Pits
Appendix
I Chemical Analysis of Water Sample from Tropicana Road Bore, by AMDEL
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1 INTRODUCTION
This groundwater evaluation is concerned with the development of water supplies for the
construction and maintenance of a haul road to transport ore from the proposed Pinjin gold
mine of Hawthorn Resources Limited (‘Hawthorn’) to processing facilities at the Carosue
Dam project of Saracen Mines Limited. The estimated water requirement is 0.4
gigalitres/annum.
A preliminary assessment of mine dewatering for the proposed operation, and a final void
evaluation, are presented herein.
2 REGIONAL DESCRIPTION
2.1 CLIMATE AND RAINFALL
The Pinjin area has a semi-arid climate with very hot summers and mild winters. Average
monthly maxima range from 17oC to 34oC and minima from 5oC to 18oC. Rainfall averages
222 mm per year, with mean monthly values ranging from 10 mm in September to 28 mm in
February (Table 1). The small annual rainfall (on average) is derived variably from low-
pressure systems moving from northerly directions in summer and from southerly directions
in winter. The summer rainfall (January to March) tends to be higher and more variable than
winter rainfall (June to August).
Table 1 : Mean Monthly and Annual Rainfall for Edjudina Station (BOM Station
No.12027) 1900-2013
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
21 28 26 19 22 22 19 17 10 11 14 13 222
Evaporation from a free water surface exceeds 3,000 mm per annum. The large excess of
evaporation over rainfall indicates that groundwater recharge would be limited to the
infrequent intense rainfall events.
2.2 TOPOGRAPHY AND DRAINAGE
The topography at Pinjin is subdued, with ground elevations in the range 325 to 440 m AHD.
Steepest topography occurs along narrow ridges of layered “greenstone” rocks, although flat-
lying sand plain underlain by granitic rocks achieves the highest elevation (about 14 km NW
of Anglo Saxon deposit).
Drainage from the Anglo Saxon area is south-westerly towards Lake Rebecca and north-
easterly towards Lake Raeside (Fig. 1). All the drainage lines are ephemeral. Both lakes are
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saline playas that occur along separate palaeodrainages with low gradients to the south-east,
towards the Eucla Basin. The Anglo Saxon deposit, and most of the haul-road route, are in
the Lake Rebecca catchment; the north-eastern part of the haul-road route is in the Lake
Raeside catchment.
2.3 GEOLOGY
A 45 km-wide belt of greenstone rocks extending south-south-easterly through the Edjudina
area is separated by a granite batholith into eastern (Pinjin) and western (Mulgabbie)
segments. The batholith, about 25 km wide, underlies the broad sand plain lying to the west
of the Pinjin greenstones and to the north of Lake Rebecca (Fig. 1).
The Pinjin greenstone belt comprises mainly felsic volcanics, mafic igneous rocks,
metasediments (including thin Banded Iron Formation), and minor ultramafics. It is cut by a
few ENE-trending Proterozoic-age mafic dykes.
Two major northerly-trending shear zones have been interpreted (Swager, 1991); one passes
through the Anglo Saxon deposit, the other is 10 km or more to the west.
A Tertiary-age palaeochannel (fossil drainage channel) of estimated width about 1 km is
located beneath the northern flank of Lake Rebecca, and is thought to run roughly parallel to
the present lake. It has been located by drilling to the south of Pinjin, but is largely undefined.
The palaeochannel contains alluvial deposits, mainly clay and a basal sand bed, to depths of
about 100 m.
2.4 HYDROGEOLOGY
Groundwater occurrence in the Pinjin area may be summarised as follows:
Fresh groundwater (less than 1,000 mg/LTDS) – very rare: small supplies (e.g. bore
LS1 near Relief Hill, Fig. 1) in mafic bedrock.
Stock quality groundwater (less than 6,000 mg/L TDS) – uncommon: small supplies in
bedrock e.g. metasediments, mafics, and granite overburden (e.g. Oldfield well,
Chinamans well).
Highly saline groundwater (generally 40,000 to 200,000 mg/L TDS) – available in
moderate to large supplies near Lake Rebecca in a palaeochannel and in decomposed
bedrock; also found in small to moderate supplies in metasediments, mafics, and
granite overburden.
The lower-salinity groundwater occurs in fractured (permeable) bedrock or overburden in
elevated areas several kilometres from saline playas, at locations where there is opportunity
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for recharge from rainfall as a result of the overburden being of small thickness or high
permeability.
High-salinity groundwater is almost ubiquitous, and reaches hypersaline concentrations near
and beneath the playas.
In the vicinity of the Anglo Saxon deposit and along the proposed haul road, the greenstone
and granitic rocks (and overburden) have been found to be low-yielding. Groundwater
supplies located in test holes to date have been mainly in the range 100 to 200 m3/d (1.2 to
2.3 L/s), or less. Permeability values calculated from 11 slug tests on drill holes in the Anglo
Saxon deposit ranged from 0.04 to 2.3 m/d and averaged 0.47 m/d, indicating generally low
permeability of the weathered bedrock at that location. Gravelly material, penetrated by
Rebecca Bore (interpreted to be palaeochannel deposits) near Lake Rebecca, has yielded quite
large water supplies, 400 to 900 m3/d (4.6 to10.4 L/s). A bore along the Tropicana access road
south of the Pinjin mine is also reported to have yielded moderate supplies (about 4 L/s from
possible palaeochannel deposits.
Groundwater levels stand at depths of 35 to 50 m below ground surface (bgs) in the elevated
bedrock areas, and at very shallow depths, probably 0 to 2 m bgs, at Lake Rebecca. The
relative groundwater levels slope down from 339 m AHD near Anglo Saxon to about 325 m
AHD at Lake Rebecca, reflecting groundwater flow southwards towards the lake. The same
would occur north-eastwards from near Anglo Saxon towards Lake Raeside. When the lakes
become inundated, saline groundwater would flow away from the lakes, in peripheral areas.
3 WATER SOURCES FOR HAUL ROAD AND MINING
The water-supply requirements for constructing and maintaining the 50 km proposed haul
road for the Anglo Saxon project are estimated to be 12.5 L/s (1,100 m3/d), based on an
average usage of 0.25 L/s per km. The water might be drawn from existing bores (owned by
others) adjacent to the project’s mining and miscellaneous tenements, and from new bores
(yet to be constructed) along the haul-road route. The owners of the existing adjacent bores –
AngloGold Ashanti Australia Limited (Tropicana project) to the east and Saracen Mineral
Holdings Limited (Carosue Dam project) to the west – have entered into discussions that may
result in Hawthorn Resources having access to water from the nominated bores: PSWB001
and Rebecca Bore respectively.
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3.1 BORE PSWB001 (‘TROPICANA ROAD BORE’)
The details of Bore PSWB001 are as follows:
Coordinates (MGA): 470,060mE 6,666,470mN
Depth: 100 m
Casing Diameter: 155mm
Casing material: PVC Class 12
Slotted Intervals: 24.5m – 78.5m and 90.5 – 96.5m
Static Water Level: 4m
Water Salinity: 91,300 mg/L TDS
Bore PSWB001 is not currently equipped for use by AngloGold. The pumping rate of 4L/s
(350 m3/d) has been assigned to this bore, subject to confirmation by formal test-pumping.
Higher pumping rates might be sustainable.
3.2 REBECCA BORE
The details of Rebecca Bore are as follows:
Coordinates: 438,435mN 6,682,643mE
Depth: 81m
Casing Diameter: 155mm
Casing Material: PVC Class 12
Slotted Interval: 3-81m
Static Water Level: 23.3m
Rebecca Bore is reported to have yielded 10 L/s when it was newly-constructed in 2003. It
has been pumped for several years, and in 2012-13 it was pumped at average rates in the
range 1.2 to 4.6 L/s for road-watering use by Saracen Holdings. These rates are taken to be
less than the bore’s capacity. Subject to agreement and confirmation by test-pumping, the
pumping rates for Hawthorn’s use could be in the range 3 to 5 L/s. Higher rates might be
sustainable, depending on bore performance and Saracen’s water usage.
3.3 BORES ALONG HAWTHORN’S HAUL ROAD
3.3.1 Bedrock
Groundwater produced from bedrock at rates of 100 m3/d (0.9 L/s) or more are likely to be
useful if located within two or three kilometres of the haul road route. Bore depths will need
to be up to 100 m, as static water levels are 30 to 50 m below ground surface (m bgs) in the
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moderately-elevated areas in the vicinity of the haul road. In low-lying areas near the salt
lakes, the water levels are less than 10 m bgs (e.g. at Ten Mile Well).
The existing bedrock bores and wells in the Pinjin area, listed in Table 2 from the 1991
Rockwater report, are reported to have provided small supplies (up to 30 m3/d) of brackish
water. They appear to have been constructed to only a few metres below static water level and
therefore tap the lowest-salinity groundwater. Deeper bores would be expected to produce
larger supplies of higher-salinity water. Generally the rock types were sheared (schistose) acid
and mafic volcanic rocks, and metasediments.
Table 2 : Data from Bores and Wells, Pinjin Area (1991)
Name Bore or
Well
Depth
m
SWL
m
Salinity
mg/L TDS
Supply
cu m/d
Rock Type
Oldfield W 55 49 4,100 11 schist/ acid volcanic
Bests B ND* ND “good” “small” schist/ acid volcanic
Battery W 49? ND “salty” 27? schist/ basic volcanic
Airstrip W ND 30 4,900 “small” schist/metasediments
Kurrajong W 18 ND 11,000 ND alluvium and granite
Ten Mile W ND 8 8,500 30 alluvium and metasediments
Table 3 contains data from an assessment of the Edjudina area, directly north of Pinjin, in
1980. It is seen that the groundwater salinities range from 670 to 34,000 mg/L TDS in the
nominated bores and wells, which are all located south of the latitude of the Edjudina
homestead. The data show that although there is a wide range of salinities, locally there is
fresh and brackish groundwater that suffices for stock-watering.
Table 3 : Data from Bores and Wells, Edjudina area, 1980-81
Name Bore or Well Water Salinity
mg/L TDS
Monaghan B 3,070
Xmas B 8,800
Kingsley W 7,060
Windy W 670
Byer W 980
Bore Well B 4,700
Soapy Head W 4,050
Loafer W 2,120
Homestead South B 1,350
Station W 1,600
West B 1,070
Lake W 2,190
PW 23A* B 3,000
PW 24C* B 34,000
PW 25* B 1,250
* Located in the Soapy Head – Bore Well area
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3.4 BEDROCK BORES DRILLED IN 2013
Five recently-drilled groundwater exploration holes drilled in the vicinity of the haul road
route gave results that suggested useful supplies (1 to 2 L/s or more per bore) might be
available from production bores at those sites. Larger-diameter holes/bores (drilled at 216 mm
diam.) are likely to provide larger supplies than the 108 mm diam. test holes, although this
would need to be confirmed by test-pumping. A summary of data from the productive
exploration holes is provided in Table 3, and locations are shown in Figure 1.
Table 4 : Results of Groundwater Exploration Programme Pinjin, November 2013
Hole IDMGAmE
MGAmN
DrillDepth(m bgl)
WaterIntersected
(m bgl)
MaxAirlift
Yield (L/s)
Salinity(mg/LTDS)
pHAquifer
Lithology
HWB002 467560 6677630 89 42 2 5,400 7.57 Meta Basalt
HWB003 469264 6679109 93 54 0.9 14,500 8.1 Meta Basaltand BIF
HWB005 468927 6680528 87 52 1-2 34,000 7.59 BIF
HWB010 452693 6681814 74 41 1.8 20,200 7.6 Granite
HWB012 477610 6668978 78 33 0.7 8,100 6.97 Dolerite
One of these test-drilling sites (HWB002) is near Oldfield Well and therefore is probably
limited to Station use.
HWB003 intersected 10 m of BIF at about 54 m depth, and gave an air-lift of 0.9 L/s of
14,500 mg/L TDS water; this location is near a mapped strata-displacement.
HWB005 targeted fractured BIF, which it intersected from 35 to 87 m depth, and yielded 1 to
2 L/s of 35,000 mg/L TDS water.
HWB010, in granite country 4.3 km west of Chinamans Well, gave a maximum airlift yield of
1.8 L/s of 20,200 mg/L TDS water from 67 m depth, although the rate seems to have reduced
to 0.5 L/s at 72 m depth.
While the actual productivity of bores at these locations is not known at this stage, an
individual bore supply of 2 L/s equates to 172 kL/d which would be pumped to storage in a
lined turkey-nest dam, and (based on similar operations) should be sufficient to maintain 8 km
of road.
Additional test-drilling sites have been selected along the haul-road route. There are presently
estimated to be an additional prospective site in BIF strata on Pinjin station and five or more
potential sites (to be confirmed by ground magnetics) underlain by granitic rock along the
WNW-trending haul-road segment on Edjudina Station.
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Two of the groundwater test holes drilled in 2013 near the haul-road route yielded between 1
and 2 L/s and have potential to supply more than 2 L/s each when production bores are
constructed at larger diameter (152 mm). It is realistic that a total of five water bores could be
constructed along the haul-road route, at successful exploration-hole sites.
3.5 PALAEOCHANNEL BORES
3.5.1 South of Pinjin
The position of the palaeochannel would best be determined using a gravity survey for about
5 km along the Kurnalpi–Pinjin road where it crosses Lake Rebecca (Line A-A’, Fig. 1). Sites
for drilling test hole(s) and then constructing a bore to about 90 m depth would be selected
from the gravity data.
A groundwater exploration hole would be drilled at about 152 mm diameter using mud-rotary
method. If sand with aquifer potential is encountered, the hole would be reamed out to
254 mm diameter, lined with 155 mm PVC casing and stainless-steel screens, and sand-
packed in the annulus. The completed bore would be air-lift developed and test-pumped.
It should be noted that the palaeochannel sand aquifer is likely to provide a larger and longer-
lasting supply than the bedrock option, but the water will be considerably more saline and
may not be as conveniently located.
3.5.2 South-East of Rebecca Bore
Given that the aquifer supplying Rebecca bore is described as palaeochannel sand, it most
likely extends south-easterly in a channel parallel to the Lake Rebecca playa. Subject to a
tenement being established, a gravity survey would be conducted (Line B-B’, Fig. 1) to locate
the channel, and test-drilling plus bore construction carried out as for item 2.5.1 above.
4 GROUNDWATER TENEMENTS AND LICENCES
The current 26D licence to construct water bores, from the Department of Water (DoW),
applies to mineral tenements E 31/782, E 31/882, and E 31/1049. Groundwater exploration
drilling on Edjudina Station is being conducted with the permission of the landholder.
Miscellaneous Licences along the haul-road route have been applied-for. It is proposed that
new Miscellaneous Licences be applied-for in areas south-east of Rebecca Bore and south of
Anglo Saxon mine (Fig. 1) for the test-drilling of potential palaeochannel sites.
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5 CHEMICAL ANALYSIS OF GROUNDWATER
Most of the water used for dust-suppression will be hypersaline, being sourced from
Tropicana Road Bore or Rebecca Bore. An analysis of a water sample taken in August 2013
from Tropicana Road Bore, made available by AngloGold Ashanti, is presented in
Appendix I. The sample represents groundwater from palaeochannel strata on the eastern side
of Lake Rebecca. Groundwater from Rebecca Bore is likely to be similar, and will be
analysed in due course.
The analysis of the Tropicana Road Bore water, by AMDEL, indicates a salinity of 91,000 to
93,000 mg/L TDS i.e. about 2.6 times the salinity of sea water. The water contains a relatively
high proportion of magnesium (relative to calcium) compared to sea water, reflecting the
magnesium-rich bedrock and overburden locally. From the analysis, the water appears to
contain no constituents in concentrations that would be detrimental to its use for dust-
suppression. Because of the high water-salinity, preventative measures will need to be
undertaken to restrict surface run-off of saline water into vegetation or drainage lines.
6 MODELLED GROUNDWATER INFLOW TO THE PIT
6.1 MODEL DESCRIPTION
The numerical model constructed to represent the proposed enlarged Anglo Saxon pit consists
of a rectangular grid of 78 columns, 36 rows, and one active layer, covering an area of 2.5 km
east-west by 4.6 km north-south, centred on the Anglo-Saxon deposit. Cell sizes range from a
minimum of 20 m by 20 m at the planned pit to 100 m by 100 m over much of the model area
and 100 m by 500 m near the peripheries of the model area. It utilises Processing Modflow
Pro version 8.0.39 (Simcore Software, 2013) that incorporates Modflow, the finite-difference
groundwater modelling software designed by the US Geological Survey (McDonald and
Harbaugh, 1988).
The water table was assumed to be flat at 338 m AHD, and it is assumed that there are
permeable rocks extending down to 285 m AHD, the base of the model. The crest of the pit is
at an elevation of about 385 m AHD, and mining is planned to extend to between about 335
and 325 m AHD, in the northern and central pit areas (A pit), and to 322 m AHD in the south
(B pit). The required amount of drawdown is therefore small, ranging from a minimum of
about 3 m in the northern pit area, 13 m in the central pit area, and to a maximum of about
16 m in the southern pit area.
Modflow’s Drain package was used to represent in-pit sumps (and/or any dewatering bores).
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6.2 MODEL PARAMETERS AND BOUNDARY CONDITIONS
Hydraulic conductivity was set at 0.08 m/d (horizontal and vertical) and increased to 0.16 m/d
along strike of the pit. This value is the geometric mean of the permeability values (0.04 to
2.3 m/d) obtained from falling head permeability tests (slug tests) on drill holes in the Anglo
Saxon deposit.
No geological structures of locally high or low permeabilities have been included in the
model, and all the rock material is assumed to have hydraulic properties in the ranges noted in
Table 5. An east-west fault that intersects the southern portion of pit A was not included
because the permeability of the faulted rock is unknown and the fault intersects only a small
portion of the required dewatering zone.
There were no pumping-out test-data available for calibration of the model. Instead, the
parameter values were varied within their likely ranges, as part of the sensitivity analysis.
Recharge was assumed to be negligible and excluded in running the model as it will be low,
perhaps one per cent of average rainfall, i.e. 2.2 mm/year.
The model boundaries have been set as a constant-head type.
Table 5 : Aquifer Parameters Adopted In Model
Parameter Units Adopted Value
Hydraulic Conductivity
(horizontal & vertical)m/d 0.08 to 0.16
Specific Yield 0.05
6.3 MODELLING RESULTS
6.3.1 Pit Inflows
The model was run to simulate dewatering of pits A and B for the periods when mining
extends below the water table. Pits A and B are planned to be mined consecutively, for
durations of 12 months per pit. Mining is scheduled to intersect the water table not until the
final three months of mining in each pit when lowering of the water table by 13 m (A pit,
central area) and 16 m (B pit) will be required. Drain conductance (which simulates
dewatering) remains active for the mining period 12 to 21 months; however, in reality the
dewatering operations might not be required during this period if the northern and southern
pits are completed separately.
Model-calculated groundwater flows to pit drains/sumps are given in Table 7. They indicate
that pit inflows are moderately low, with highest average flow of about 5.8 L/s (500 m3/d).
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Table 6: Model-Calculated Groundwater Flows
Months Av. Flows
(L/s)
9 to 12 5.2
12 to 21 2.4
21 to 24 5.8
Model-calculated (peak) drawdowns around pit A at the end of 12 months of mining and 3
months of dewatering are shown in Figure 2. Figure 3 shows the model-calculated
drawdowns at the completion of mining of both pits; measurable drawdowns are predicted to
extend up to 285 m north and 145 m south of the planned pit-perimeter, and about 220 m to
the west and 180 m to the east.
6.3.2 Sensitivity Analysis
Model parameters were varied in turn to determine their effect on the calculated total volumes
of groundwater to be pumped during dewatering. The sensitivity analyses results are given in
Table 8 in the form of percentages of the flows calculated for the adopted model.
Table 7: Results of Sensitivity Analysis
Parameter, and Variation% of Adopted Model
Flows
Horizontal conductivity *2 160
Horizontal conductivity *0.5 64
With barrier boundaries 100
With east-west fault 110
Specific yield *2 127
Specific yield *0.5 81
With 1% recharge 101
The results indicate that the model is sensitive to horizontal conductivity, and to a lesser
degree specific yield; and it is insensitive to the nature of the model boundaries and recharge.
Hydraulic conductivity values, which were obtained from the falling-head permeability tests,
could be more-accurately assessed by conducting pumping tests if a bore or bores were to be
constructed. Values of specific yield can only be determined after the aquifer has been
stressed for an extended period, allowing calculations based on the volume of the drawdown
cone and the total volume of water that was pumped. Consequently, there is a moderately
high probability that actual pit inflow rates could be double or half those calculated; only
minor inflows of about 1 L/s would be expected if actual permeability is in the lower range
(0.01 to 0.04 m/d) of the hydraulic conductivities obtained from the falling-head permeability
tests.
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7 FINAL VOID ASSESSMENT
The numerical groundwater model was used with a water balance to assess the nature of the
final pit void.
Groundwater inflows to the mined-out pit at several pit water levels were estimated using the
model. These are included in the water balance given in Table 9.
Table 8: Pit Void Water Balance
In-Pit WaterLevel
Water Area Inflows Rainfall Evap. Balance
(m AHD) (m2) (m3/d)
375 97055 0 47.2 566 -519
335 12168 37 5.9 71 -28
330 4672 92 2.3 27 67
325 925 139 0.5 5 134
322 300 164 0.1 2 162
The values in the last column “Balance” are groundwater inflows plus rainfall accumulation
minus evaporative losses.
The rainfall accumulation value is taken to be 80 percent of the average annual rainfall within
the planned pit perimeter, on a daily basis. Evaporation losses are taken to be the average
dam evaporation rate (Luke, Burke and O’Brien, 1988) over the area of open water for each
pit water level.
It can be seen from Table 9 that inputs and outputs are in balance when the pit water level is
at about 333.5 m AHD, compared to an initial water level of about 338 m AHD.
The small final pit void has very high probability, therefore, of being a permanent
groundwater sink. The salinity of water in the void will gradually increase, but this will have
no impact on the surrounding groundwater as there will be no flow from the void.
8 SUMMARY
Water-supply requirements for the proposed gold-mining operation by Hawthorn Resources at
Pinjin are estimated to be 1,100 m3/d (0.4 gigalitres/annum), almost all of it to be used for
haul-road dust-suppression. Local groundwater will provide the supplies. Subject to
arrangements with adjacent project-operators, the water will be obtained from the Tropicana
Road Bore or Saracen’s Rebecca Bore. These bores produce hypersaline water from
palaeochannel aquifers. Alternatively or additionally, several small-producing bores could be
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constructed along the haul-road route at locations where groundwater exploration drilling and
geophysical surveys have indicated potentially useful supplies.
The water produced from the palaeochannel aquifers will be hypersaline: for example, about
92,000 mg/L TDS from Tropicana Road Bore. As for other projects in the Eastern Goldfields,
water containment procedures will be designed to prevent incursion of saline water into local
catchments that may be non-saline.
Pit dewatering at between 250 and 1,000 m3/d (3 and 12 L/s) is the estimated range of
maximum pumping rates to lower water levels 13 to 16 m at the final mining depths. The
estimates are based on numerical modelling and sensitivity analysis incorporating some site-
measured permeability values. For most of the mining period, dewatering will be not required,
or it will be at lower rates than those noted.
The final mine void is calculated to become a groundwater sink, with a water level of about
333.5 m AHD, i.e. about 4.5 m lower than the present groundwater level.
Dated: 14 April 2014 Rockwater Pty Ltd
Claire Kasperkiewicz J R Passmore
Senior Hydrogeologist Principal
REFERENCES
Luke, G.J., Burke, K.L., and O'Brien, T.M., 1988, Evaporation data for Western Australia.
Tech. Report No. 65 (2nd Ed), W.A. Dept. of Agriculture.
McDonald, M.G., and W.A. Harbaugh, 1988, MODFLOW, A Modular Three-Dimensional
Finite-Difference Ground-Water Flow Model. U.S. Geological Survey, Washington,
DC. (A:3980), open file report 83–875, Chapter A1.
Simcore Software, 2013, Processing Modflow, An integrated modeling environment for the
simulation of groundwater flow, transport, and reactive processes.
Swager, C.P., 1994, Geology of the Pinjin 1:100 000 sheet: Western Australia Geological
Survey, 1:100 000 Geological Series Explanatory Notes, 22p.
Rockwater Pty Ltd165.0/14/01
FIGURES
CLIENT:
PROJECT:
DATE:
Dwg. No:
LOCALITY PLANWITH GEOLOGY
Figure 1
165-0/Surfer/Rpt 14-01/100k Geology.srf
Hawthorn Resources Limited
Pinjin Project
April 2014
165-0/14/4-1
G 3100004L 3100032
L 3100066
M 3100078
M 3100079
M 3100088
M 3100113
M 3100284
Tropicana Road Bore
Deenya Bore
Rebecca Bore
Chinaman's Well
PW 40
PW 41
PW 41A
PW 42PW 43PW 44
HWB002
HWB003
HWB005
HWB010
HWB012
LS1
436000 440000 444000 448000 452000 456000 460000 464000 468000 472000 476000 480000
Easting (m MGA Zn 51)
6656000
6660000
6664000
6668000
6672000
6676000
6680000
6684000
6688000
6692000
Nort
hin
g(m
MG
AZ
n51)
LEGEND
Test Hole (2013)
Existing Bore or Well
WIN Database Test Hole
Suggested Miscellaneous Licence
Proposed Haul Road
Boundary of Current MiscellaneousLicence (application) & MiningTenements
Proposed Line of Gravity Survey
RELIEF HILL
A
A'
B
B'
B
B'
CLIENT:
PROJECT:
DATE:
Dwg. No:
Hawthorn Resources Limited
Pinjin Project
April 2014
165-0/14/01-2
MODEL-CALCULATED PEAK DRAWDOWNS (m)
AROUND PLANNED PINJIN PIT
A PIT
Figure 2
I/165-1/surfer/14-01/Peak Drawdowns - A Pit.srf
BUSSELL HWY
SUES RD
WONNERUP SOUTH RD1
35
79
11
66
72
00
06
67
22
00
66
72
40
06
67
26
00
66
72
80
06
67
30
00
66
73
20
0
mN
MG
A
473600 473800 474000 474200 474400 474600
mE MGA
3Modelled peak drawdown (m)after 12 months of mining / 3 months of dewatering A Pit
Pit outline
Area to be dewatered
A Pit - planned
B Pit - planned
CLIENT:
PROJECT:
DATE:
Dwg. No:
Hawthorn Resources Limited
Pinjin Project
April 2014
165-0/14/01-3
MODEL-CALCULATED PEAK DRAWDOWNS (m)
AROUND PLANNED PINJIN PIT
A and B PITS
Figure 3
I/165-1/surfer/14-01/Peak Drawdowns - A & B Pits.srf
BUSSELL HWY
SUES RD
WONNERUP SOUTH RD
1
1
1
1
3
3
3
5
5
5
7
7
9
9
11
111
31
5
66
72
00
06
67
22
00
66
72
40
06
67
26
00
66
72
80
06
67
30
00
66
73
20
0
mN
MG
A
473600 473800 474000 474200 474400 474600
mE MGA
3Modelled peak drawdown (m)after 24 months of mining / 3 months of dewatering of B Pit & A Pit
Pit outline
Area to be dewatered
A Pit - planned
B Pit - planned
Rockwater Pty Ltd165.0/14/01
APPENDIX I
Chemical Analysis of Water Sample
from Tropicana Road Bore, by Amdel
Provided by Anglogold Ashanti Australia Limited