Appendix 5 Groundwater Report- GDS€¦ · SHS014 -DTS Doc053 Rev 1 H1 Desktop Hydrogeological...

Appendix 5

Groundwater Report- GDS

H1 Desktop Hydrogeological Assessment

Mt Henry Open Pits

October 2015

SHS014-DTS-Doc053

Revision 1

Proponent

Enviro Department / Higginsville Gold Operations, Metals X Limited

Level 3, 18-32 Parliament Place, West Perth WA 6005.

Tel: +61 8 9039 6006

Email: [email protected]

Service Provider

Groundwater Development Services (GDS) Pty Ltd

149 Grand Ocean Blvd, Port Kennedy WA 6172

Tel: 0448 756 080

Email: [email protected]

Groundwater Development

Services (GDS) Pty Ltd SHS014-DTS-Doc053 Rev 1

H1 Desktop Hydrogeological Assessment Mt Henry Open Pits

1

TABLE OF CONTENTS Page

1.0 INTRODUCTION ........................................................................................ 1

1.1 Background ....................................................................................................... 1

1.2 Location ............................................................................................................. 2

1.3 Higginsville Operations .................................................................................... 2

1.4 Current Licensing ............................................................................................. 4

1.5 Proposed licence application........................................................................... 4

1.6 Proposed Use .................................................................................................... 4

2.0 CLIMATE /RAINFALL ............................................................................... 4

3.0 PREVIOUS INVESTIGATIONS ................................................................. 6

3.1 Preliminary hydrogeological assessment (Venables, 2009) .......................... 6

3.2 Lake Dundas Water Quality and Fauna Surveys (WRM 2013) ....................... 6

3.3 Dewatering Assessment (GRM 2014a) ............................................................ 6

3.4 Pit Closure Assessment (GRM 2014b) ............................................................ 7

4.0 CURRENT BORES .................................................................................... 7

5.0 GEOLOGY ............................................................................................... 10

5.1 Regional Geology ............................................................................................10

5.2 Local Geology ..................................................................................................11

5.2.1 Mt Henry ............................................................................................................ 11

5.2.2 Selene ................................................................................................................ 11

5.2.3 North Scotia ....................................................................................................... 11

6.0 HYDROGEOLOGY .................................................................................. 12

6.1 Regional Hydrogeology ...................................................................................12

6.2 Local Hydrogeology ........................................................................................12

6.2.1 Venables (2009) ................................................................................................ 12

6.2.2 GRM (2014a) ..................................................................................................... 13

6.3 Water Levels .....................................................................................................14

6.4 Groundwater Chemistry ..................................................................................14




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7.0 DEWATERING VOLUMES ...................................................................... 17

8.0 DEWATERING STRATEGY .................................................................... 17

9.0 PIT DRAWDOWN .................................................................................... 18

10.0 EXISTING USE ........................................................................................ 18

11.0 PROPOSED USE .................................................................................... 19

12.0 IMPACT ASSESSMENT .......................................................................... 19

13.0 MANAGEMENT APPROACH .................................................................. 19

13.1 Best Practice ....................................................................................................19

13.2 Mitigation Measures ........................................................................................20

14.0 REFERENCES ......................................................................................... 21

FIGURES Page

Figure 1 Location Map ............................................................................................... 3

Figure 2 2014 Investigation Bore Locations ............................................................... 9

TABLES

Table 1 Summary of Higginsville Licences ................................................................. 4

Table 2 Monthly climatic statistics Norseman (012065, BOM) ................................... 5

Table 3 Monitoring Bores .......................................................................................... 7

Table 4 2014 Drilling Investigation Bores ................................................................... 8

Table 5 Water Quality Analysis ................................................................................ 16

Table 6 Pit Inflows .................................................................................................. 17

Table 7 Maximum Pit Drawdown and Distance of Influence ................................... 18

Table 8 Existing Groundwater Use .......................................................................... 18

Table 9 Preliminary Monitoring Program .................................................................. 20




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APPENDICES

APPENDIX A: Dewatering Assessment, GRM (2014a)

APPENDIX B: Pit Closure Assessment, GRM (2014b)

APPENDIX C: Preliminary Hydrogeological Assessment, Venables (2009)

APPENDIX D: Lake Dundas Water Quality and Fauna Survey, WRM (2013)




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1.0 INTRODUCTION

Higginsville Gold Operations (HGO) plan to develop the Mt Henry Open Pits

Project which is located on mining lease M63/515 and M63/516 in the Dundas

Mineral field. Gold ore from this mine is to be trucked a distance of 85 km to the

Higginsville operation via the Coolgardie Esperance Highway. The location of the

HGO and the Mt Henry Open Pits is shown on Figure 1.

1.1 Background

This report has been prepared to support a licence application for abstraction of

400,000 kLpa groundwater from the Mt Henry Pits Project, which is comprised of

three open pits: Mt Henry, Selene and North Scotia pit (Figure 1).

Dewatering is required to allow mining below the water table in each of the three

pits. Dewatering yield is planned for use in dust suppression within the mine area.

Process water will not be sourced from the Mt Henry area as the ore will be

transported to the HGO mill.

Numerical modelling (GRM, 2014a) indicates that inflows to the three pits will

range from 5.5 lps (173,448 kLpa) to 8.3 lps (261,749 kLpa). Due to the presence

of a thick alluvial sequence in Selene Pit, there is a possibility of increased

groundwater inflows of up to 10 lps (315,360 kLpa) during significant rainfall

events. A licence allocation of 400,000 kLpa will address any contingency

requirements associated with periodic rainfall related inflows.

This report conforms to H1 desktop assessment standard as required by

Department of Water Operational Policy No 5.12. A desktop assessment without

requirement for further field investigation is considered appropriate for this study.

Points assigned for each main factor, as per Policy No 5.12, are summarised

below:

The volume requested is 400,000 kLpa (6 points)

The Level of allocation in the Lefroy-Dundas GSA, combined fractured rock

aquifer is a Level 4 (4 points)

The potential for unacceptable impacts to other users is unlikely (0 points)

The potential for unacceptable impacts to GDE's is unlikely (0 points)

The potential for unacceptable impacts to other users is unlikely (0 points)

The existing salinity (mg/L) is hypersaline (0 point)

Total Points: 6+4+0+0+0=10

Table 1, Decision table for hydrogeological assessments, in Operational policy no.

5.12 (DoW 2009) indicates that for scores of 8 to 12, an H1 Desktop Assessment

is appropriate.




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1.2 Location

The Higginsville Gold Operations are located approximately 55km north of

Norseman and 110km south-east of Kalgoorlie in the Goldfields region of Western

Australia.

The Mt Henry Open Pits project is located 85 km south of the Higginsville Gold

operations and 23 kilometres south of Norseman. The site is accessed from

Norseman by driving 23 km south on the Coolgardie Esperance highway and

turning east along a dirt track for a distance of 3 km. The Mt Henry Open Pit project

is located on the western edge of Lake Dundas and lies within mining tenements

M63/515 and M63/516. The project location is shown Figure 1 and is centred at

approximately 386,000mE and 6,417,000 mN (Zone 52, MGA, GDA94).

The Mt Henry Open Pits project area are located in the Goldfields Groundwater

Area and the Lefroy-Dundas Groundwater Sub-Area.

1.3 Higginsville Operations

Gold mining commenced at Higginsville by Samantha Gold NL in 1989, followed

by Resolute Mining Limited. Mining and ore processing ceased in 2000 and

Resolute sold exploration rights to Western Mining Company who sold onto

Goldfields Australia Limited. Avoca Resources Ltd acquired the Higginsville

Project in June 2004 and commenced development of the Trident underground

mine and construction of the 1Mtpa Higginsville processing facility.

In 2008, construction of the processing plant and associated infrastructure together

with a 160 person onsite village, offices and workshops were completed. In

February 2011, Avoca merged with Anatolia Minerals Development to form Alacer

Gold Corporation.

In October 2013, Metals X Limited, through its wholly owned subsidiary Westgold

Resources Pty Ltd, reached an agreement with Alacer to acquire its Australian

gold operations, including Alacer Gold Pty Ltd and its wholly owned entities which

includes Avoca Resources Ltd in relation to Higginsville Gold Operations.

Mt Henry Open Pits project was acquired by Metals X from a joint venture between

Panoramic Resources and Matsa Resources in October 2015. The Mt Henry Open

Pit project is a developing project which will provide ore to the Higginsville Mill via

the development of open cut pits.




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Figure 1 Location Map




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1.4 Current Licensing

There are no current licenses associated with Mt Henry Open Pits Project. The

Higginsville Mining Operations do have current licences associated with the other

mining areas, which are summarised below in Table 1.

Table 1 Summary of Higginsville Licences

Licence Allocation

(kLpa)

Associated Activities and Areas

GWL160795(5) 500,000

Dewatering of open pits and

underground operations close vicinity

to Higginsville Operation Centre

GWL165489(3)* (1,500,000) Dewatering of the Chalice open pit

and underground operations GWL178699 400,000 Dewatering of existing open pits at

the Lake Cowan Mining Area GWL180185 1,000,000 Dewatering of the Challenger open

pit. TOTAL* 3,400,000

*GWL165489 (3), for Chalice pit, is not in use and will be relinquished when dewatering activities at

Challenge commence. The total allocation will be 1,900,000 kLpa when the GWL165489 (3) is

relinquished.

1.5 Proposed licence application

The proposed licence for the Mt Henry, Selene and North Scotia open pits will

allow for the dewatering of the pits to facilitate mining below the water table. The

licence for the Mt Henry Open Pits project is a request for an allocation of 400,000

kLpa. The licence duration is expected to be 10 years.

1.6 Proposed Use

The proposed use will be dust suppression around the active mining areas.

2.0 CLIMATE /RAINFALL

Climate is semi-arid, typically varying markedly in magnitude from year to year and

in temporal distribution. The nearest long term climate station is at Norseman. Data

from the Norseman sites is summarised on Table 2.

January is the hottest month with a mean maximum of 32.6°. The coolest month

is July with a mean minimum 5.1°.

The mean annual rainfall at Norseman is 288 millimetres. The highest mean

monthly rainfall occurs in May with a record of 30.5 mm. The lowest mean monthly

rainfall occurs in January with a record of 19.9 mm.

Annual evaporation rate approximates 2500 millimetres.




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Table 2 Monthly climatic statistics Norseman (012065, BOM)

Statistic Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual No Yrs

Mean maximum temperature °C

32.6 31.3 28.8 24.6 20.4 17.5 16.8 18.5 21.6 25 28.1 30.7 24.7 61

Mean minimum temperature °C

15.8 15.9 14.5 11.6 8.5 6.3 5.1 5.4 7.3 9.7 12.3 14.1 10.5 61

Mean rainfall (mm) 19.9 24.9 24.4 23.4 30.5 30.1 26.8 24.8 21.4 20.3 20.4 21.4 288 115

Highest rainfall (mm) 116 203 189 112 137 104 80 94.9 75.2 87.2 86.9 151 624 115

Lowest rainfall (mm) 0 0 0 0 0 2.2 2.5 0.8 0.4 0 0 0 138 115

Start: 1951 End: 2012




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3.0 PREVIOUS INVESTIGATIONS

3.1 Preliminary hydrogeological assessment (Venables, 2009)

A desk top study was completed on the Mt Henry and North Scotia pits by Venables

(2009). The Selena pit was not part of the assessment.

The objectives were:

To gain a broad understanding of the hydrogeological conditions at the Mt

Henry and North Scotia Pits.

To identify concerns which could impact on the mining of several shallow

pits.

To establish a monitoring bore database and design a monitoring program

for the bores.

Identify future drilling requirements for the purpose of constructing

dewatering and monitoring bores.

3.2 Lake Dundas Water Quality and Fauna Surveys (WRM 2013)

The results of the study were not used directly in this document.

The objectives were to:

Collect lake sediments for the purpose of species identification

Sample aquatic fauna

3.3 Dewatering Assessment (GRM 2014a)

The GRM (2014a) dewatering assessment has been used extensively in this

document.

The objectives of the assessment were to:

Define the reginal and local geology

Define the regional and local hydrogeology

Drilling investigations to target features identified during earlier studies and

construct monitoring bores in Mt Henry, Selena and North Skotia pits.

Installation of data loggers to assess rainfall and recharge relationships.

Hydraulic testing (slug tests) to determine aquifer parameters (hydraulic

conductivity) of the three pits.

Groundwater flow modelling to define potential drawdown impact,

drawdown extent and pit inflows during 6 year Life of Mine.

Identify a preliminary operating strategy and monitoring regime.




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3.4 Pit Closure Assessment (GRM 2014b, MBS 2014)

The pit closure assessment is based on mine inflows reported in the preceding

study (GRM 2014a) drawing from work completed by MBS in 2014. The primary

objective of this study was to apply pit lake water and solute balance modelling to

simulate post closure conditions in each pit.

The primary output from the study were:

A water balance addressing pit lake storage volume, pit inflows and

outflows.

Residual recovering water levels in each pit with associated recovery rates.

Equilibration water levels of each pit after 300 to 400 years.

Salinity, acidity and metal concentrations after 400 years.

4.0 CURRENT BORES

Sixteen monitoring bores were constructed during previous site investigations

(GRM 2014a) which comprised:

Nine in-pit monitoring bores

One ex-pit monitoring bore

Six shallow lake monitoring bores

The monitoring bores associated with each pit are summarised below in Table 3

and locations shown in provided in Figure 2.

Table 3 Monitoring Bores

Pit Bore Number Target Area

Mt Henry MTHEWE02-07 6 Pit

MTHMB01 1 Lake Edge

Selene SELWE04-05 1 Pit

SeLWE01-03 3 Lake Edge

North Scotia

SCOWE01-3 3 Pit

SCOMB01-02 2 Lake Edge




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Table 4 2014 Drilling Investigation Bores

Area Tenement Bore ID Easting Northing Collar RL

mAHD Hole Depth

(mbgl) Purpose

Mt Henry M63/515 MTHWE02 385,798 6,417,514 285 78 Pit Area


Mt Henry M63/515 MTHWE04 385,803 6,417,337 284.5 73 Pit Area




Mt Henry M63/515 MTHMB01 386,070 6,416,694 251 12 Lake Edge

Selene M63/516 SELWE05* 385,548 6,412,946 253 78 Pit Area

Selene M63/516 SELWE04 385,446 6,413,218 246 102 Pit Area

Selene M63/516 SELMB02 385,601 6,413,466 246 12 Lake Edge

Selene M63/516 SELMB03 385,629 6,413,030 247 12 Lake Edge

North Scotia M63/516 SCOWE01 385,036 6,411,272 251.5 60 Pit Area

North Scotia M63/516 SCOWE02 384,949 6,411,295 252 54 Pit Area

North Scotia M63/516 SCOWE03 384,966 6,411,095 247 67 Pit Area

North Scotia M63/516 SCOMB01 385,135 6,411,427 250.5 12 Lake Edge

North Scotia M63/516 SCOMB02 385,105 6,411,183 246.5 12 Lake Edge

*SELWEO5 was a dry bore and decomissioned.




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Figure 2 2014 Investigation Bore Locations




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5.0 GEOLOGY

5.1 Regional Geology

Regional geology has been described in previous reporting (GRM 2014a) and is

reproduced below.

The Mt Henry project lies within the southern portion of the Norseman-Wiluna

greenstone belt of the Eastern Goldfields Yilgarn Block. Norseman is the southern-

most gold mining centre of the Norseman-Wiluna gold belt which hosts over 270

million ounces of gold. The Norseman region has been a major gold producer with

in excess of 5.5 million ounces of gold produced since 1935.

Although the greenstone sequence from the Norseman area can be broadly

correlated with those of the Kalgoorlie-Kambalda region, they form a distinct terrain

which is bounded on all sides by major regional shears. The Norseman Terrane

has a prominent banded iron formation sequence which distinguishes it from the

Kalgoorlie-Kambalda Terrane.

The regions’ greenstone succession has been subdivided into four formations in

the vicinity of the project (Doepel 1973), which trend north-south and dip steeply

to the west. A description (from lowest to highest) of the four formations is

presented below:

Penneshaw Formation – A greenstone sequence on the eastern side of

the project, comprising mafic volcanics interfingered with felsic

volcaniclastic and sedimentary rocks. The Penneshaw Formation is

intruded by the Buldania Granite Complex in the east.

Noganyer Formation – A banded iron formation, with chert sandstone

and shale units, which structurally overlies the Penneshaw Formation.

The Noganyer Formation hosts the gold mineralisation at Mt Henry and

Selene.

Woolyeenyer Formation – A sequence of mafic volcanic rocks with

minor ultramafic and sedimentary units, which conformably overlies the

Noganyer Formation. The Woolyeenyer Formation hosts the Norseman

style quartz reef gold mineralisation, including the North Scotia deposit.

Mt Kirk Formation – Felsic volcanic and sedimentary rocks intruded by

thick mafic sills that disconformably overlie the Woolyeenyer Formation.

The Mt Kirk Formation subcrops to the west of the project and is

bounded by a granite-gneiss complex.

The bedrock geology is overlain by Quaternary and Tertiary deposits, comprising

aeolian dune deposits, alluvium and colluvium. These include Tertiary Wollubar

Sandstone which forms the basal sand within the palaeochannels. These are

overlain by silts and clays of the Perkolilli Shale, which sub-crop under Lake

Dundas and the greater Lake Cowan palaeochannel system.




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5.2 Local Geology

The local geology has been described in previous reporting (GRM 2014a) and is

reproduced below:

5.2.1 Mt Henry

The Mt Henry resource is hosted in the Noganyer Formation. The main lode is

an elongated orebody, approximately 1.9 km long, 6 to 10 m wide and dips

approximately 70° to the west.

The host rock is predominantly banded iron formation with minor meta-

basalts and dolerites. Sulphide minerals range from trace to 10%, and comprise

pyrrhotite with minor pyrite, arsenopyrite, chalcopyrite and marcasite.

Mineralisation is pervasive within the sheared BIF throughout the length of the

deposit, with discrete shoots containing higher grades and thicker intervals of

mineralization plunging to the north-northwest. The gold occurs within quartz

veins, in clouds with silicate minerals and in close proximity to sulphide minerals,

particularly pyrrhotite.

Late pegmatite dykes cross cut the host rock and stope out mineralization when

they cross the lodes.

5.2.2 Selene

The Selene resource is similar to the Mt Henry deposit, hosted in Noganyer

Formation BIF intruded by numerous dolerite sills. The footwall contact is

characterized by metamorphic sedimentary schist and the hanging wall by the

overlying dolerites of the Woolyeenyer Formation.

The Selene mineralization extends for 1.3 km along strike and extends 550 m down

dip at a shallow angle of around 20°. The mineralization thickens in the central

part of the resource to a true thickness of 35 to 40 m.

The main difference between the Selene and Mt Henry deposits is the

mineralization at Selene occurs in zones throughout the BIF package, whereas

at Mt Henry the mineralization is generally hosted in a shear on the hanging wall

contact of the BIF.

5.2.3 North Scotia

The North Scotia resource covers a strike length of 600 m within the Archean mafic

rocks of the Woolyeenyer Formation.

The Woolyeenyer Formation is host to auriferous quartz veins that have been

mined in the Norseman district continuously for 80 years. Gold mineralization is

hosted by laminated quartz veins which dip at approximately 70° to the west. The

nuggetty gold mineralization is disseminated throughout the 1 to 5 m wide

laminated quartz veins. Sulphides present include pyrite and galena.




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6.0 HYDROGEOLOGY

6.1 Regional Hydrogeology

The regional hydrogeologyl geology has been described in previous reporting

(GRM 2014a) and is reproduced below:

The hydrogeology of the project area is characterized by low relief and easterly draining palaeo-drainage systems, underlain by Archean sequences.

Groundwater typically occurs in:

Regional catchment controlled flow systems in fresh and weathered fractured rock aquifers;

Tertiary palaeochannel sands (Wollubar Sandstone);

Calcrete units that commonly overlie palaeochannel deposits;

Shallow alluvium.

Groundwater is recharged by direct rainfall infiltration or by stream flow during episodic rainfall events. The recharge occurs mainly on or adjacent to the catchment divides, beneath which there are corresponding, subdued groundwater divides. The groundwater moves from these divides to discharge into salt lakes along the palaeo-drainages. In the salt lakes the groundwater is evaporated and concentrated to brine, which then descends and moves downstream in the palaeochannel sand to eventually discharge into the Eucla Basin.

Groundwater salinities typically range from about 1,000 to 200,000 mg/L Total Dissolved Solids (TDS). Low salinity groundwater, ranging from 1,000 to 5,000 mg/L TDS occurs in areas most affected by direct rainfall recharge, e.g. near catchment divides and within shallow alluvium and calcrete units. The highest salinity groundwater occurs low down in the catchments within palaeochannel sands and deeper fractured rock aquifers.

Small supplies of groundwater can be found throughout the area. Large, fresh groundwater supplies are rare, but large, reliable supplies of saline to hypersaline groundwater are obtainable from the palaeochannel sand and site specific shear zones and deeply oxidized zones in the fractured rocks.

6.2 Local Hydrogeology

6.2.1 Venables (2009)

A preliminary desk top study of the local hydrogeology was completed by Venables

(2009) of the Mt Henry and North Scotia pits. The following conclusions were

made:

The southwestern portion of the proposed Mt Henry pit may encounter

significant inflows from the lake. The i n f l o w s w o u l d b e

a s s o c i a t e d w i t h t h e deep weathering a n d presence of a large

pegmatite intrusive which could act as a strong water-bearing conduit.

The northern portion of North Scotia pit has weathered material mainly

above the level of Lake Dundas and little inflow from the lake is expected.




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In the southern portion of North Scotia pit there is a substantial

thicknesses of alluvium, clay and saprolite. It is expected that significant

seepage from the lake into the southern part of the pit can be expected.

In general, it was unclear as to whether either of the two pits will require

dewatering.

Initial significant water inflow is considered unlikely in the North.

The southern ends of the Mt Henry and North Scotia Pits may be prone to

significant inflows from Lake Dundas.

Contingency plans should be made for the possibility of significant inflows

into the southern parts of Mt Henry and North Scotia pits.

It should be noted that after a review of the GRM (2014a) report, the concerns

highlighted by Venables regarding the potential for significant inflows to Mt Henry

and North Scotia pits may have been overstated.

6.2.2 GRM (2014a)

The local hydrogeology described by Venables (2009) was updated by GRM

(2014a) following drilling investigations, construction of monitoring bores, hydraulic

testing and groundwater flow modelling. The conclusions are reproduced below:

The permeability within the proposed pits is confined predominantly to

discrete structural features within the fresh bedrock, as well as the overlying

alluvium and weathered zone.

The Mt Henry pit inflows are structurally controlled and associated with the

contact between the quartz pegmatite and fresh basalt.

Airlift yields of four bores within the pegmatite had airlift yields which ranged

from 1 to 2.2 lps. The remaining 2 bores had negligible flows.

Permeability away from the structural features in each of the three pits is

very low with low storage characteristics.

Selene does not have the significant water bearing structures as seen in

Henry and North Skotia pits. An exploration bore completed in the pit

structures at Selena had a yield of 0.1 lps. Inflows are associated with

shallow alluvium and weathered bedrock, where an exploration bore had a

yield of 0.6 lps.

Similar alluvial sequences observed at Mt Henry and North Scotia were

less thick.

There is connectivity between Lake Dundas and the shallow groundwater

system.

Inflow rates, where the alluvium is thicker, particularly at Selena, are likely

to increase following high rainfall events.

The inflows at the North Scotia pit are associated with quartz veins within

the fresh basalt where airlift yields ranged from 1.7 to 2.5 lps.




14

The volume of pit inflows in each pit estimated from numerical modelling

indicated that the pits were amenable to dewatering by surface water

sumps.

The overall drawdown effect from the numerical modelling was interpreted

to be localised.

6.3 Water Levels

The average ground elevation at the centroid of each pit is:

Mt Henry: 285 m AHD

Selene : 250 m AHD

North Scotia.: 252 m AHD

The open pit mining of reach pit will be to the following depths:

Mt Henry: 90 meters (195 m AHD)

Selene: 150meters (100 m AHD)

North Scotia: 75 meters (177 m AHD)

Groundwater levels measured during previous investigations (GRM 2014a) ranged as follows:

Mt Henry Pit : 250 to 275 m AHD (from south to north)

Selene and North Scotia: 245 to 246 m AHD, respectively.

The groundwater levels associated with the Lake Dundas lie around 245 m AHD, similar to the water levels measured at Selene and North Scotia which are located on the lake margin. The levels are consistent with groundwater flows towards the lake, which forms the regional groundwater sink (GRM 2014a).

For modelling purposes (GRM 2014a), the ambient pre-mining water level in Mt Henry pit was set at 275 m AHD. For Selene and North Scotia pits, the pre mining water level was set at 245 m AHD.

Modelling was run to simulate effective dewatering of the pit area below the proposed depth of pit development.

6.4 Groundwater Chemistry

Laboratory analysis of samples from monitoring bores from the Mt Henry, Selene

and North Scotia pits were completed during previous investigations (GRM 2014a).

Groundwater salinity of the Mt Henry pit ranges from 10,000 mg/L (MTHWE02) in

the north to 121,000 mg/L TDS (MTHWE07) in the south. It was concluded that

groundwater salinity increased down dip of the orebody lithology. Higher salinity

was considered to be representative of the ambient groundwater quality in the

crystalline bedrock.

Groundwater salinity of the Selene Pit was hypersaline with a salinity of 251,000

mg/L TDS, which is consistent with the deposits proximity to Lake Dundas.




15

Groundwater salinity of the North Scotia pit ranged from 239,000 to 274,000 mg/L

TDS, which is similar to the salinity of the Selena pit and associated with the

proximity of the pit to Lake Dundas.

The analytical results have been reproduced below in Table 5. The water quality

results show hypersaline water quality which is representative of groundwater and

surface water in the Dundas Paleodrainage system.




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Table 5 Water Quality Analysis

Analyte Unit SCOWE01 SCOWE02 SCOWE03 SELWE04 MTHWE02 MTHWE03 MTHWE04 MTHWE07

pH 6.5 7 6.1 6.8 7.3 7.5 7.7 7.1

Total Dissolved Solids mg/L 274,000 239,000 243,000 251,000 10,000 17,400 18,200 121,000

Electrical Conductivity mS/cm 220,000 210,000 200,000 210,000 16,000 20,000 27,000 140,000

Bicarbonate alkalinity as HCO3 mg/L 47 140 8 38 240 320 460 170

Carbonate alkalinity as CO3 mg/L <1 <1 <1 <1 <1 <1 <1 <1

Hydroxide alkalinity as OH mg/L <5 <5 <5 <5 <5 <5 <5 <5

Total alkalinity as CaCO3 mg/L 38 120 6 32 190 260 380 140

Chloride mg/L 140,000 140,000 140,000 150,000 4,100 5,700 6,900 63,000

Sulphate mg/L 13,000 12,000 12,000 12,000 2,200 5,100 5,000 9,200

Nitrate, NO3 mg/L <0.05 0.06 0.08 0.84 <0.05 <0.05 0.06 <0.05

Aluminium, Al mg/L <1 <1 <1 <1 <0.02 <0.02 <0.1 <1

Arsenic, As mg/L <1.0 <1.0 <1.0 <1.0 <0.02 <0.02 <0.1 <1.0

Calcium, Ca mg/L 620 720 590 740 290 370 490 450

Cobalt, Co mg/L <0.5 <0.5 <0.5 <0.5 0.01 0.02 <0.05 <0.05

Copper, Cu mg/L <0.25 <0.25 0.49 <0.25 <0.005 <0.005 <0.025 <0.25

Iron, Fe mg/L <1 <1 <1 <1 6.5 <0.02 <0.1 <1

Magnesium, Mg mg/L 11,000 10,000 10,000 9,900 550 800 1,000 5,700

Manganese, Mn mg/L 1.4 2 2 3.1 2.5 2.6 1.7 4.1

Nickel, Ni mg/L 0.42 0.35 0.34 0.46 0.024 0.099 0.062 0.39

Potassium, K mg/L 890 820 790 790 64 84 100 370

Silica, soluble mg/L 7.3 10 9.3 6.7 52 49 52 17

Silicon, Si mg/L 3.4 4.7 4.3 3.1 24 23 24 7.8

Sodium, Na mg/L 97,000 83,000 87,000 91,000 2,600 5,000 5,500 40,000

Zinc, Zn mg/L <0.5 <0.5 0.74 <0.5 0.03 0.09 <0.05 <0.05

Total hardness by calc CaCO3/L CaCO3//L 48,000 44,000 43,000 43,000 3,000 4,200 5,400 24,000


Services (GDS) Pty Ltd SHS012-DTS-Doc051 Rev 2 H1 Desktop Hydrogeological Assessment Mt Henry Open Pit

17

7.0 DEWATERING VOLUMES

Numerical modelling (GRM 2014a) provided estimates of maximum inflows for

each pit over a 6 year mine life. The results are summarised below in Table 6.

Table 6 Pit Inflows

Pit Maximum

Inflows (lps)

Maximum

Inflows

(m3/day)

Maximum Inflows

(kLpa)

Mt Henry 5.5 475 173,448

Selene 5.0 – 10.0* 432 - 864 157,680 – 315,360

North Scotia 8.3 717 261,749

* Seasonal inflows to Selene Pit associated with high rain events

8.0 DEWATERING STRATEGY

A dewatering strategy based on numerical modelling results and hydrogeological

assessment was described in previous reporting (GRM 2014a) and is reproduced

below:

The groundwater inflow rates predicted by the groundwater flow models indicate

dewatering of the Mt Henry, Selene and North Scotia pits will be best achieved by

sump pumping methods. Sumps should be strategically located at low points along

the pit floor.

A sufficient contingency should be considered to allow for short term, higher than

anticipated inflow rates following high rainfall events (Selene) and upon

interception of additional water bearing features in the fresh bedrock (all pits). A

contingency plan could include provision of additional surface water pumps for the

duration required to dewater the excess volumes. An allowance in the groundwater

abstraction licence will also be required to manage incidental rainfall derived

groundwater flowing into the pit void.

All dewatering discharge will be transferred to a process water dam at the surface

for use by the operation for dust suppression. At the predicted dewatering rates

there should be no requirement to discharge mine water to the environment.

Preliminary supply bores will be constructed to provide dust suppression water

prior to dewatering supply being available. The locations are currently hypothetical,

but, it is likely that the southern end of the Mt Henry pit would be an appropriate

location. This would also advance dewatering at that end of the pit and support

operational objectives.



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9.0 PIT DRAWDOWN

Predicted groundwater level drawdown for baseline runs at the end of mine of each

pit were calculated during previous reporting (GRM 2014a). The drawdowns and

maximum distances of influence at the end of mining are summarised below in

table 7.

Table 7 Maximum Pit Drawdown and Distance of Influence

Pit Maximum Drawdown

(m)

Maximum Influence (m)

Mt Henry

End of Mining (6 yrs) 2 1000

20 years 2 500

60 years 0.5 1000

100 years 0.5 <1000

Selene & N Scotia

End of Mining (6 yrs) 2 500

20 years 0.5 200

60 years 0.5 100

100 years 0.5 0

10.0 EXISTING USE

The nearest existing groundwater user is located 4 km south of the project in the

paleochannel aquifer. The next closest users are located 13 and 30 km to the north

in fractured rock aquifers. The existing users, volume of allocation and relative

distance from Mt Henry Open Pits project are summarised below in Table 8.

Table 8 Existing Groundwater Use

Map

Index Licence User

Allocation

(kLpa)

Location with

respect to Mt Henry

Open Pits Project

1 GWL61134 Central Norseman

Gold Corporation

Limited

6,500,000 13 Km to the north

in fractured rock

1 GWL61134 Central Norseman

Gold Corporation

Limited

6,500,000 4 Km to the south

in the paleochannel

2 GWL160161 Main Roads 40,000 30 km north east



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11.0 PROPOSED USE

The primary groundwater use associated with the dewatering of the Mt Henry Open

Pits Project is dust suppression.

12.0 IMPACT ASSESSMENT

Open pit evaporation and mine dewatering in this region are having no visible impact on the general environment or availability of hypersaline water resources.

Potential impacts of taking hypersaline groundwater from the Mt Henry Open Pits area for a short duration of less than 10 years are neutral as groundwater is hypersaline.

The Mt Henry Open Pits water also has no commercial value due to its hypersaline nature and has no impact on the sole beneficial groundwater user other than itself.

Numerical modelling has indicated that maximum drawdown of 2 meters will occur at distances of 1,000 meters from the Mt Henry Pits and 500 meters from the Selene and North Scotia pit. The drawdown impacts away from the immediate mining area are within the range of annual fluctuations in groundwater.

Potential impacts to Lake Dundas from the dewatering of Mt Henry, Selene and North Scotia pits will be negligible, considering the low volumes required and distance from each pit.

There are no groundwater dependent vegetation communities, threatened ecological communities or priority ecological communities that will be impacted by the project (GRM, 2014b).

Groundwater in the project area is hypersaline and low in dissolved oxygen and will not support stygofauna populations. (GRM, 2014b).

The project is located adjacent to Lake Dundas. No significant aquatic fauna species have been recorded in the lake. The project will have minimal impacts on the lake water quality and ecology (GRM, 2014b)

The nearest other licensed user is located 4 km to the south in the regional paleochannel aquifer. The proposed pits are constructed in the regional fractured rock aquifer system and impacts at distances of 4 kilometers are considered to be negligible. Other licensed users are located at distances of 13 and 30 kilometres from the project where potential impacts are assumed to be negligible.

13.0 MANAGEMENT APPROACH

13.1 Best Practice

Groundwater abstraction will be conducted and monitored according to the

operating strategy approved with the groundwater license.

Monitoring bores constructed during the 2014 investigations will be incorporated

into an Operating Strategy. Previous reporting outlined a preliminary monitoring

program which is reproduced below in Table 9.



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Table 9 Preliminary Monitoring Program

Monitoring Sits

Minimum Frequency

Criteria

Mt Henry, Selene, North Scotia

Monthly Abstraction Volume

Monthly In-Pit Water Level

Monthly Electrical Conductivity and pH

Annually Major Component Analysis

Monitoring Bores

Monthly Water Level

The major component analysis would comprise the following parameters:

Physical-chemical parameters – pH, electrical conductivity (EC), total

dissolved solids (TDS), total hardness, and total alkalinity.

Major ions – sodium, potassium, calcium, magnesium, chloride,

sulphate, bicarbonate, carbonate, nitrate.

Minor ions/metals – silica, aluminium, iron and manganese.

Optimum use of the water will be achieved through the use as dust suppression.

A water balance which incorporates the dewatering and dust suppression volumes

will be reviewed annually.

Use of hypersaline water for dust suppression will be restricted to mine areas so

as not to impact on bordering vegetation. Regular monitoring of vegetation will be

conducted on the periphery of the Mt Henry Open Pits project area and any

evidence of impact from dewatering will be subjected to mitigating measures.

13.2 Mitigation Measures

Higginsville Gold Operations will define a monitoring schedule for the Mt Henry

Open Pits project as set out in an Operating Strategy. Monitoring would be

designed to identify any deleterious trends in groundwater levels and/or quality,

which may affect other users, the aquifer or the environment.

Groundwater abstraction for the Mt Henry Open Pits project is not expected to

impact on other groundwater users. However, if a decline in water level is noted in

any bores operated by others, which may be attributable to Mt Henry Open Pits

dewatering operations, then an investigation will be commissioned to determine

the actual cause of the water level decline. If the decline is attributable to project

dewatering operations then the licensee will provide details of the investigation to

the DoW along with a proposed management strategy.

If unexpected declines in the aquifer water levels or change in water quality are

observed due to Mt Henry Open Pits dewatering operations, then an investigation



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will be initiated into the cause of the change and monitoring may become more

frequent. If required, alternative pumping regimes will be investigated.

Groundwater abstraction for Mt Henry Open Pits poses minimal risk to the

environment, in terms of water level drawdown effects on groundwater dependent

ecosystems. However, if any degradation of vegetation occurs, which may be

attributable to the dewatering operations, an investigation will be commissioned to

determine the actual cause of the vegetation degradation. If it is determined that

the degradation is due to Mt Henry Open Pits dewatering operations, mitigation

options will be assessed and implemented as appropriate.

14.0 REFERENCES

Doepel JG 1973 Norseman, WA: Western Australian Geological Survey, 1:125,000

Geological Series Explanatory Notes.

GRM 2014a Dewatering Assessment Mt Henry Gold Project, Prepared for Mt

Henry Gold Pty Ltd, April 2014.

GRM 2014b Pit Closure Water and Solute Balancing Modelling Mt Henry Gold

Project, Prepared for Mt Henry Gold Project Pty Ltd, June 2014h.

MBS Envirionmental 2014, Mt Henry Gold Project it Lake Closure Geochemical

Modelling, Prepared for Panoramic Gold, August 2014.

Venables, T. 2009 Preliminary Hydrogeological Report on the Mt Henry and North

Scotia Pits, Prepared for MATSA Resources Ltd, 25 March 2009.

WRM (Wetland Research and Management) 2013 Lake Dundas Sediment

Rehydration, Water Quality and Aquatic Fauna Surveys, Prepared for Panoramic

Resources Ltd, December 2013



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APPENDIX A –

GRM (2014a)



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APPENDIX B –

GRM (2014b)



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APPENDIX C –

Venables (2009)



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APPENDIX D

WRM (2013)

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