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McArthur River Mine

Overburden Management Project

Draft Environmental Impact Statement

WAppendix W

Aquatic Ecology Impact Assessment Report

MCARTHUR RIVER MINE OVERBURDEN MANAGEMENT PROJECT:

AQUATIC FAUNA

Prepared for:

McArthur River Mining

PO Box 36821

Winnellie NT 0821

Prepared by:

Indo-Pacific Environmental Pty Ltd

PO BOX 191

Duncraig East, WA, 6023

Phone: (08) 9444 1422

Fax: (08) 9444 1466

ACN 120 114 365

Project ID: 15006

Project ID 15006, Rev 0, February 2017 i

Document Control

Revision Version Author Date Reviewer Date

A Internal Draft D. Thorburn,

S. Longbottom

P. Barden

20-12-2016 D. Thorburn 21-12-2016

B Draft to Client D. Thorburn 22-12-2016 D. Moss (METServe)

C. Wiley (METServe)

G. Taylor (Glencore)

J. Hacker (Glencore)

D. Herbert (Glencore)

S. Rathbone (Glencore)

05-01-2017

C Draft to Client D. Thorburn 12-01-2017 G. Taylor (Glencore)

C. Wiley (METServe)

J. Barker (METServe)

15-02-2017

D Draft to Client D. Thorburn 16-02-2017 C. Wiley (METServe) 20-02-2017

0 Final to Client D. Thorburn 23-02-2017

Disclaimer

This report has been prepared on behalf of and for the exclusive use of McArthur River Mining. Reproduction or

use of any part of this report (including data) is not permitted without the written permission of McArthur River

Mining and Indo-Pacific Environmental. Indo-Pacific Environmental Pty Ltd, however, does not warrant in any way

whatsoever that the material contained in this report is fit for use for any other purpose or by any other party than

those aforementioned.

Project ID 15006, Rev 0, February 2017 ii

CONTENTS

LIST OF TABLES ....................................................................................................................... v

LIST OF FIGURES ..................................................................................................................... v

APPENDICES ............................................................................................................................vi

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

Study Aims and Objectives ......................................................................................... 1 1.1

Approach .................................................................................................................... 1 1.2

Study Area .................................................................................................................. 1 1.3

FAUNA OF CONSERVATION SIGNIFICANCE .......................................................... 4 2.0

Legislation .................................................................................................................. 4 2.1

Species of Conservation Significance ......................................................................... 4 2.2

BASELINE .................................................................................................................. 6 3.0

Aquatic Fauna - Definition .......................................................................................... 6 3.1

Historical Surveys ....................................................................................................... 6 3.2

Current Aquatic Fauna Monitoring Programs .............................................................. 7 3.3

Survey Areas and Locations ...............................................................................8 3.3.1

General Fish Capture methods ......................................................................... 12 3.3.2

Species Diversity and Abundance ..................................................................... 15 3.3.3

Comparison of Natural and Modified Habitats ................................................... 15 3.3.4

Monitoring Movement and Tagging ................................................................... 15 3.3.5

Tissue Metals Analysis ...................................................................................... 16 3.3.6

Project Specific Fauna Investigation – Emu Creek ............................................ 19 3.3.7

Macroinvertebrates............................................................................................ 20 3.3.8

Aquatic Reptiles ................................................................................................ 21 3.3.9

Current Knowledge ................................................................................................... 21 3.4

General ............................................................................................................. 21 3.4.1

Fauna in Natural and Modified Habitats ............................................................ 24 3.4.2

Emu Creek Fauna ............................................................................................. 26 3.4.3

Metal Concentrations in Fauna ......................................................................... 27 3.4.4

Tagging of Teleost Species ............................................................................... 30 3.4.5

Project ID 15006, Rev 0, February 2017 iii

Fish of Conservation Significance ..................................................................... 30 3.4.6

Macroinvertebrates............................................................................................ 35 3.4.7

Aquatic Reptiles ................................................................................................ 36 3.4.8

ECOLOGICAL IMPACT ASSESSMENT................................................................... 42 4.0

Assessment Process and Risk Identification ............................................................ 42 4.1

Risk Assessment ...................................................................................................... 45 4.2

KEY RISKS, MANAGEMENT AND MONITORING .................................................. 57 5.0

Primary Environmental Targets ................................................................................ 57 5.1

Risk identification and Mitigation ............................................................................... 58 5.2

Domain 1 - Open Cut: Operation .............................................................................. 58 5.3

Reduction in Water Quality ................................................................................ 58 5.3.1

Drawdown ......................................................................................................... 60 5.3.2

Domain 1 - Open Cut: Closure.................................................................................. 61 5.4

Fauna Stranding in the Final Void Waterbody ................................................... 61 5.4.1

Discharge of Surface and Groundwater from the Final Void Waterbody to the 5.4.2

McArthur River ................................................................................................................. 64

Reduction in Water, Sediment and Organic Matter in the McArthur River ......... 65 5.4.3

Stability of Final Void Waterbody Walls, Inlet and Outlet ................................... 66 5.4.4

Domain 2 - NOEF ..................................................................................................... 67 5.5

Expansion of NOEF Footprint ........................................................................... 67 5.5.1

Effects on Surface and Groundwater ................................................................ 68 5.5.2

Uncontrolled Release of Water from Runoff Management Dams ...................... 71 5.5.3

Domain 3 - TSF ........................................................................................................ 72 5.6

Groundwater mound.......................................................................................... 72 5.6.1

Uncontrolled Release of Tailings through Spill and Seepage ............................ 73 5.6.2

Confirmation of Modelling ......................................................................................... 75 5.7

REFERENCES ......................................................................................................... 76 6.0

APPENDIX 1 – Survey of fish and crustaceans of emu creek and tissue metal content 2016. ....

.................................................................................................................................. 81

APPENDIX 2 – Habitat preferences of the largetooth sawfish (pristis pristis) and implications for

proposed pit closure. .............................................................................................................. 125

Project ID 15006, Rev 0, February 2017 iv

APPENDIX 3 – Combined results of macroinvertebrate sampling program ........................... 149

Project ID 15006, Rev 0, February 2017 v

LIST OF TABLES

Table 1. Aquatic fauna known to occur or considered to occur in the McArthur River which are

listed under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act),

Territory Parks and Wildlife Conservation Act 2006 (TPWC Act) and Northern Territory

Fisheries Act 1988 (Fisheries Act; Fisheries Regulations – Reg. 9 Certain fish not to be taken).

Table 2. Fishes species recorded within the McArthur River. Species denoted with red have

been recorded post 2012, species denoted with black have only been recorded prior to 2012.

Shading indicates estuarine vagrants.

Table 3. Records of Pristis pristis in the McArthur River since 2006. Records include tag

number, date recorded, location, sex, total length (TL mm), rostrum length (RL mm) and tooth

count of the right and left sides.

Table 4. Likelihood Definitions

Table 5. Environment Consequence Definitions.

Table 6. Risk Rating Matrix. Risk classifications include L: Low, M: Moderate, MH: Moderately

High, H: High and C: Critical.

Table 7. Environmental Risk Assessment indicating rankings (R) for inherent risk (based on

existing mitigation and management actions) and residual risk (based on existing and

additional mitigation and management actions). Risk rankings were quantified by comparing

the likelihood (L) and consequence (C) definitions outline in Section 4.1. Proposed new project

aspects (which has no existing mitigation or management) are indicated by N/A. Justifications

are based on information provided by MRM. These justifications rely heavily on model

predictions. As such, deviation from the modelled predictions may ultimately affect these

outputs.

LIST OF FIGURES

Figure 1. The McArthur River and key locations.

Figure 2. Dry river bed downstream of MRM (SW11) and shallow remnant pool in the diversion

in the late dry season (November) 2016.

Figure 3a. Locations surveyed for aquatic biota for tissue metal analysis in 2016.

Figure 3b. Locations surveyed for aquatic biota in the vicinity of MRM for tissue metal analysis

in 2016.

Figure 4. Macroinvertebrate samples sites.

Figure 5. Species collected for metal and lead isotope analysis in the McArthur River, including

a) Nematalosa erebi, b) Melanotaenia splendida, c) Leiopotherapon unicolor and d)

Project ID 15006, Rev 0, February 2017 vi

Macrobrachium rosenbergii. Samples of e) Hephaestus fuliginosus and f) Lates calcarifer were

also collected in 2014.

Figure 6. Density of fish species (mean number per metre) recorded form electrofished

transects in woody debris and adjacent areas of open bank in 2010.

Figure 7. Mean number of fish and crustaceans captured per metre whilst electrofishing at sites

downstream the diversion, bare bank sites within the diversion, complex habitat sites within the

diversion and complex habitat sites upstream of the diversion during April 2015.

Figure 8. Comparison of mean lead concentrations (mg/kg wet weight) in M. splendida

collected throughout the McArthur River catchment between 2012 and 2015.

Figure 9. Sediment trap to catch flow off haul road (top), low bund at the downstream end of

SW19 (bottom left) and result of excavation of SW19 in the late dry season 2016 after flow has

completely ceased showing complete removal of sediment derived from dust and runoff

(bottom right).

Figure 10. Lead concentration (mg/kg) in the <63 µm sediment fraction recorded from surface

water monitoring sample sites in the vicinity of McArthur River mine between 2011 and 2016.

Figure 11. Locations at which Pristis pristis has been recorded in McArthur River catchment

since 2012.

Figure 12. Clockwise from top left Emydura subglobosa worrelli, Chelodina rugosa, Crocodylus

johnstoni and Acrochordus arafurae.

Figure 13. Locations at which Crocodylus porosus and Crocodylus johnstoni have been

recorded in the McArthur River catchment during Aquatic Fauna surveys since 2012.

Figure 14. Locations at which Acrochordus arafura has been recorded in the McArthur River

catchment during Aquatic Fauna surveys since 2012.

Figure 15. Locations at which freshwater turtles have been recorded in the McArthur River

catchment during Aquatic Fauna surveys since 2012.

APPENDICES

Appendix 1. Survey of Fish and Crustaceans of Emu Creek and Tissue Metal Content 2016.

Appendix 2. Habitat Preferences of the Largetooth Sawfish (Pristis pristis) and Implications for

Proposed Pit Closure.

Appendix 3. Combined Results of Macroinvertebrate Sampling Program.

Project ID 15006, Rev 0, February 2017 1

INTRODUCTION 1.0

Study Aims and Objectives 1.1

McArthur River Mining (MRM) contracted Indo-Pacific Environmental (IPE) to provide a report

on the aquatic fauna found within the McArthur River and its tributaries as part of the

preparation of an Environmental Impact Statement (EIS) for the McArthur River Mine

Overburden Management Project (the Project). The aim of this report was to characterise the

aquatic fauna occurring within and around the study area which may be potentially impacted by

the Project and define well-considered mitigation strategies to reduce the magnitude or negate

these potential impacts. In meeting these aims the specific objectives for aquatic fauna studies

are to:

Document the species of aquatic fauna known to occur in the McArthur River and its

tributaries through a combination of literature review, collation of current monitoring

program data and limited field assessment;

Identify conservation significant aquatic fauna which may be present in the region and

address their occurrence in the vicinity of the Project area and downstream;

Provide an assessment of the impacts of the Project on aquatic fauna, particularly

species of conservation significance; and

Develop strategies to minimise and manage potentially adverse ecological impacts.

Approach 1.2

Aquatic fauna of the McArthur River and its tributaries has been well documented through the

comprehensive and continuous monitoring of the fauna present in riverine waters. The current

report therefore draws upon a robust dataset encapsulating species inventories, targeted

studies on threatened species and past projects which have monitored environmental response

to mine related activities. In addition targeted field work to assess the fauna present in areas

which would be directly influenced by the Project footprint (for example, within the Emu Creek

catchment) was conducted to facilitate any impact assessment with certainty. The full results of

this latter survey can be found in Appendix 1 of this report.

Study Area 1.3

The MRM site is located in the Northern Territory (NT) approximately 65 kilometres south-west

of the township of Borroloola and 120 kilometres south of the Bing Bong concentrate storage


and ship loading facility (Bing Bong) (Figure 1). The project area is located on McArthur River

station, and is covered by mineral leases ML1123, ML1121, ML1122, ML1124 and ML1125.

Consistent with the description provided by METServe (2016) the Project has three major

components (domains) with the potential to directly and/or indirectly affect the aquatic

environment within the Project footprint, in adjacent waters of the McArthur River and

downstream of the mine site. These include:

Expansion of the North Overburden Emplacement Facility (NOEF);

Development of the existing Tailings Storage Facility (TSF); and

Open cut closure scenario with connectivity to the main channel McArthur River.


FAUNA OF CONSERVATION SIGNIFICANCE 2.0

Legislation 2.1

Various legislation exist which afford protection to fauna considered to be of conservation

significance at an Australian Commonwealth Government and/or State Government level. The

legislation referenced during the assessment of the Project included:

The Commonwealth Environment Protection and Biodiversity Conservation Act 1999

(EPBC Act) which provides for the protection of the environment, especially matters of

National Environmental Significance (MNES), and is administered by the

Commonwealth Department of the Environment and Energy;

The Territory Parks and Wildlife Conservation Act 2006 (TPWC Act) which provides for

the conservation and sustainable utilisation of wildlife (in particular Part IV) and is

administered by the Parks and Wildlife Commission of the Northern Territory

Department; and

The Northern Territory Fisheries Act 1988 (Fisheries Act) which was created to

manage aquatic resources in a sustainable manner and is administered by the

Department of Primary Industry and Resources – Fisheries.

Species of Conservation Significance 2.2

A search using the Australian Government Department of the Environment and Energy (DEE)

Protected Matters Search Tool and the Species Profile and Threats (SPRAT) Database

indicated that four species of national conservation significance may be present in aquatic

habitat within the Project area or adjacent to it (Table 1). These include:

One fish species, Pristis pristis (formerly Pristis microdon) (Largetooth Sawfish), which

is listed as vulnerable;

One reptile species, Elseya lavarackorum (Gulf Snapping Turtle), which is listed as

endangered;

One reptile species, Crocodylus johnstoni (Freshwater Crocodile), which is listed as

marine; and

One reptile species, Crocodylus porosus (Estuarine Crocodile), which is listed as a

marine and migratory species.

These searches also indicated that no EPBC listed Threatened Ecological Communities were

present in the Project area.


In relation to species afforded protection under Northern Territory Legislation only one species,

P. pristis is listed which is likely to occur in the Project area or in close proximity to it (Table 1).

Extensive surveys of the aquatic fauna of the McArthur River have been conducted to date.

This includes at least 300 days being spent capturing and documenting aquatic fauna for

monitoring purposes since 2006. While these surveys have collected numerous records of P.

pristis, C. johnstoni and C. porosus in riverine waters of the McArthur River (including those in

the vicinity of MRM), despite the significant survey effort E. lavarackorum has not been

recorded. Subsequent discussion of potential impacts of the Project on these species is

presented Section 3.4.

Table 1. Aquatic fauna known to occur or considered to occur in the McArthur River which are

listed under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act),

Territory Parks and Wildlife Conservation Act 2006 (TPWC Act) and Northern Territory

Fisheries Act 1988 (Fisheries Act; Fisheries Regulations – Reg. 9 Certain fish not to be taken).

Common Name Species Name EPBC Act TPWC Act Fisheries Act

Fish

Largetooth Sawfish Pristis pristis Vulnerable,

Migratory

Vulnerable Protected

Reptiles

Gulf Snapping Turtle Elseya lavarackorum Endangered - -

Freshwater Crocodile Crocodylus johnstoni Marine - -

Estuarine Crocodile Crocodylus porosus Marine,

Migratory

- -


BASELINE 3.0

Aquatic Fauna - Definition 3.1

The aquatic fauna of the McArthur River for the purpose of this study was considered to be the

vertebrate and invertebrate animals which live in water for most if not all of their life in the non-

tidal freshwater reaches of the McArthur River and its tributaries.

Historical Surveys 3.2

In 2005/2006 MRM submitted a proposal to convert its operation from underground to open pit

which included the rechannelling of the McArthur River proper (referred to as the Phase 2

expansion project). In order to properly address the potential impacts of that proposal and

define effective management actions a significant increase in the understanding of the aquatic

fauna and habitat present in the McArthur River was required. As such, a number of monitoring

programs were initiated in those years, with a number of these persisting to date. Prior to this,

aquatic surveys of the McArthur River were limited in both the area investigated and the types

of fauna.

The first aquatic fauna study was initiated by Mount Isa Mines who commissioned a study of

fish in the vicinity of the mine site in 1975 (Midgley 1975). A subsequent survey of fish

occurring in the McArthur River in close proximity to MRM and adjacent streams was

conducted by Midgley (1982).

General surveys of aquatic fauna (fish and macroinvertebrates) were conducted in the mine

project area for the original Draft Environmental Impact Statement during 1992 (Hollingsworth

Dames and Moore 1992, Midgley 1994). At this time a survey of the fish and

macroinvertebrates of Barney and Surprise Creeks was undertaken by the Northern Territory

Museum in 1993 (Hanley 1993).

In 2006 additional fish surveys were undertaken to address data limitations in relation to the

Phase 2 expansion. In particular, questions relating to the presence of P. pristis in waters of the

McArthur River and its occurrence upstream of MRM were addressed with a survey aimed at

capturing this species (RPS Bowman, Bishaw and Gorham 2006). This survey resulted in the

capture of a single P. pristis from Eight Mile Waterhole. Additional anecdotal records from other

locations in the McArthur River were also documented.

In addition to the aforementioned studies which surveyed a range of fauna additional

macroinvertebrate studies were conducted in 2002 and 2003 as part of the Phase 2 expansion,

which saw 12 new sites surveyed within the main channel McArthur River and the Glyde River

(URS/MRM 2005). Similar to the studies of fish, studies of macroinvertebrate studies were


incorporated into an annual monitoring regime as part of the Phase 2 expansion PER

commitments, which continue to date.

Current Aquatic Fauna Monitoring Programs 3.3

Knowledge of the aquatic fauna of the McArthur River and its tributaries has vastly increased

since 2006 due to a number of ongoing monitoring programs run since that time and the

addition of new programs in subsequent years. While the objectives of each respective study

have generally increased over time the current report is based on recent objectives and

knowledge. Annual and ongoing programs currently undertaken by MRM include:

A biannual survey of fish and other aquatic fauna which aims to:

Monitor fish populations in permanent and semi-permanent pools of the

McArthur River;

Monitor the diversity and distribution of species within Surprise and Barney

Creeks;

Monitor populations of P. pristis, a Vulnerable species, and collate data on

sightings, growth rates and movement;

Monitor the recovery/establishment of aquatic habitat in the McArthur River

diversion channel;

Monitor fish passage success through the diversion channel;

Assess the effectiveness of rehabilitation methods within the diversion channel

including the addition of large woody debris; and

Collect size and distribution data on aquatic reptiles.

A biannual study of metals in aquatic fauna tissues which aims to:

Detect the introduction of MRM derived metals in the aquatic food chain;

Compare tissue metal concentrations of fauna of the McArthur River with those

occurring in adjacent catchments; and

Monitor metal levels in species of aquatic fauna commonly consumed by

people residing in the area.

An ongoing fish tagging program which aims to:

Monitor the movement of Lates calcarifer (Barramundi) and P. pristis in the

McArthur River with the use of conventional tagging techniques and more

recently through acoustic tagging.


An annual study of macroinvertebrates which aims to:

Utilise macroinvertebrate assemblages as indicators of environmental health

by comparing on-lease and off-lease faunas.

Survey Areas and Locations 3.3.1

Monitoring of aquatic fauna in the McArthur River is currently catchment wide with annual

programs incorporating routine sampling sites as far upstream as Top Crossing, located

approximately 50 km upstream of MRM, and as far downstream as the Burketown Crossing in

the town of Borroloola (Figure 1). While monitoring of riverine fauna occurs downstream of this

location, the crossing generally represents the tidal limit of the McArthur River. As

aforementioned, for the purpose of this study aquatic fauna was considered to be the animals

occurring in non-tidal freshwaters.

Between Borroloola and Top Crossing the McArthur River has a well-defined main channel with

a low number of major tributaries and very few permanent lowland swamps or waterholes.

While some spring feeding is known to occur in the middle and upper reaches of the river, flow

rates, river height and indeed persistence of water is season driven. After the cessation of rain,

the river rapidly contracts into a series of pools connected by long shallow runs. Indeed, in

years of average rainfall and below average rainfall, the river in the vicinity of MRM exists as a

series of disconnected pools separated by large sections of dry bed by the late dry season

(Figure 2). Drying of the river bed in the vicinity of the mine has, however, been observed to

occur as early as May in years of particularly poor rainfall.

Figure 2. Dry river bed downstream of MRM (SW11) and shallow remnant pool in the diversion

in the late dry season (November) 2016.

Remnant pools which persist throughout the dry season subsequently represent important

refugia for aquatic fauna. In close proximity to the mine these include Djirrinmini, Cattleyard


and Eight Mile waterholes (Figure 1). Water also persists throughout the year in pools within

the Glyde River which adjoins the McArthur River approximately two kilometres downstream of

the mine. Upstream of Eight Mile Waterhole large persistent pools can also be found in the

Kilgour River and at Bessie Springs (located approximately 40 km upstream of the mine).

Pools which persisted throughout the year were not present in the original section of the

McArthur River which was infilled during the conversion of MRM to an open pit operation.

However, intrusion of groundwater into the diversion has led to the creation of additional

aquatic habitat that persists throughout the year. This includes at least two long stretches of

river which hold waters of greater than two metres depth throughout the year.

In relation to fish, survey sites were originally selected on the basis that water was likely to

remain throughout the year and where access to the river was available. Over time, however,

as program objectives changed numerous ephemeral survey sites were added to investigate

seasonal habitat utilisation in both the main channel of the McArthur River and specific

attention has been afforded to tributaries on the MRM mine lease such as Surprise and Barney

Creeks.

A commitment of the Phase 2 expansion Public Environmental Report (PER) was the initiation

of an annual program which monitors the concentration of metals and metalloids in tissue of

various aquatic fauna. Originally the program included sampling at various on-lease locations.

However, this program has gradually expanded to include sample sites in the main channel of

the McArthur River, tributaries and those sections which have been diverted on the mining

lease (Figure 3). Additional locations are also annually surveyed in adjacent river catchments to

provide a regional comparison and act as reference sites.

In relation to macroinvertebrate sampling, these sites have been selected within the context of

the local tributaries, mine facilities and diversions and were designed to sample reference sites,

diversion sites and sites potentially influenced by a gradient of contaminant concentrations

relating to mine operations. Sites were initially selected in consultation with the Northern

Territory Government and where possible were located in close proximity to existing MRM

surface water (SW) sites. Twenty-four sites were initially selected for sampling. However, a

number of these have been removed from the program, have been modified during mine

expansion or were not sampled in some years due to absence of safe access, surface water or

suitable substrates. Additional sites have been added to the program in response to changing

conditions and monitoring requirements, including additional sites on the Barney Creek

diversion, McArthur River diversion and Emu Creek. During the development of the monitoring

program there has been an effort to locate and sample reference sites that support both riffle

and edge habitats.


A number of additional reference sites have been added during the course of the

macroinvertebrate program in an effort to locate suitable reference sites in catchments

removed from mining operations, with sampling undertaken on Leila Creek, Caranbirini Creek,

Amelia Creek, Glyde River, Wearyan River, Foelshe River and Robinson River.

Macroinvertebrate sampling site locations are shown in Figure 4. The sites include:

Five sites on Barney and Surprise Creek upstream of the Barney Creek diversion;

One site on Emu Creek;

Three sites on the Barney Creek Diversion;

One site on the McArthur River below the Barney Creek diversion and upstream of the

McArthur River diversion outlet;

Five sites on the McArthur River diversion;

Three sites on the McArthur River below the McArthur River diversion;

Three sites on the McArthur River above the McArthur River diversion;

Four reference sites on the off-stream rivers (Glyde, Wearyan, Foelshe and Robinson

Rivers); and

Four reference sites on off-stream minor-drainage lines (Leila, Caranbirini and Amelia

Creeks).

General Fish Capture methods 3.3.2

The aquatic fauna surveys outlined in Section 3.3 are conducted annually and consist of two

survey periods, one in the early dry season (i.e. as soon as sites become accessible after the

wet season and flow rates have sufficiently slowed to allow safe access) and the second in the

late dry season when the river is at base flow. Data on community structure and samples for

tissue analysis are collected using a variety of survey methods, which includes fyke, seine and

gill nets and electrofishing equipment. Visual survey and line fishing techniques are also

utilised. The sampling equipment used and the methods of their use aims to avoid mortality of

fish in instances when tissue sample collection is not required.

Fyke (migration) nets are one of the techniques used to monitor the movement of fish through

the diversion and compare the diversity of fish present in the diversion to those occurring in

naturally vegetated stretches immediately up and down stream. Sampling generally occurs at

three sites within the river diversion and at two sites above and below the diversion in each

season. However, in recent years due to low rainfall, and thus river height, fyke nets have not

been used in the late dry season. Fyke nets are a funnel net with two nets being deployed at

each sampling site, one facing upstream and the other downstream. The mouth of the net is


held open by a rigid aluminium frame which was secured in place with the use of star pickets.

The wings of each net are secured to the nearest bank to channel fish into the mouth of the

fyke net. In order to minimise the risk of drowning amphibians and aquatic reptiles the end of

the net (the bunt) is tied up above the water line. Fyke nets were checked early each morning

and the number and length of fishes and other aquatic fauna recorded. Samples for tissue

metal analysis are also collected by this method.

Seine (haul) nets are used at numerous sites throughout the study area. This method was

effective at targeting all species in waters up to one metre depth which were relatively free of

large debris and rock. Seine nets were generally walked out from the bank, stretched parallel to

bank and hauled shoreward. The area over which the seine net was hauled was estimated and

used to subsequently calculate the abundance of fish captured per m2. The number and length

of fishes and other aquatic fauna is recorded.

Electrofishing is conducted using a Smith Root LR-24 backpack electrofisher and scoop nets.

Transects of variable but measured length are electrofished at each sampling site and relative

abundance in the form of fish per metre is calculated. Stunned fish are rapidly released, or if

required, allowed to revive in an aerated tub of freshly-collected water prior to being identified,

measured and released. Electrofishing is conducted at all fyke net sites to ensure that the full

suite of species present is accounted for. This sampling tool is also used at a large number of

other survey locations from below, within and above the diversion in order to provide

comparative data to assess the diversion aquatic fauna against fauna occurring in naturally

vegetated sections of the McArthur River. Electrofishing is also used throughout the catchment

to collect samples for tissue analysis.

Gill nets are utilised at long-term monitoring sites, including below and above the Burketown

Crossing, Djirrinmini Waterhole, and Eight Mile Waterhole, with the aim of assessing the

distribution of P. pristis and larger fish species. In recent years gill nets have been set in the

diversion during the routine monitoring. Gill nets were utilised in Bessie Spring until 2009.

However, the consistency of the fauna observed and distance upstream suggested it was not

suitable habitat for P. pristis. Gill nets are a maximum of 40 m long, and comprised of two

sinking monofilament panels each 20 m long, and of 100 mm and 150 mm stretched mesh,

respectively. Gill nets are generally utilised during daylight hours as most gill net sampling sites

a) are remote, b) have large on-water transiting distances with numerous in-water hazards, c)

are inhabited by both estuarine and freshwater crocodiles, which are more active and thus

captured more frequently at night, and/or d) by-catch mortality is increased at night. The time

the gill net is set for and the length of the net can be used to calculate relative abundance in the

form of fish per metre per hour.

In all surveys field recordings of water temperature (oC), conductivity (mS), salinity (ppt), pH,

and dissolved oxygen (mg/L) are recorded for each sample site as well as the pool length,


width and water depth (m). Notes on the immediate habitat are also recorded (e.g. substrate

type, aquatic flora and riparian vegetation cover etc.) and a photo taken.

Species Diversity and Abundance 3.3.3

One of the key aquatic monitoring commitments outlined in the 2006 MRM PER was to monitor

the overall diversity of fishes occurring in the McArthur River adjacent, directly upstream and

downstream of MRM. This commitment is monitored through the combination of fyke net and

electrofishing abundance data at consistent locations. The combination of data from these two

methods at the sample location provides comprehensive coverage of mobile and cryptic

species.

Comparison of Natural and Modified Habitats 3.3.4

One of the key rehabilitation strategies implemented in the diversion has been the placement of

large woody debris piles to provide aquatic habitat and basic energy input to form the basis of

the food chain. Electrofishing is the primary method used to investigate the effectiveness of the

large woody debris (LWD) piles placed within the diversion by comparing density data with that

collected from bare bank diversion habitats and natural sections of the river directly up and

downstream of the diversion. These habitats are subsequently categorised and reported on as

being either downstream complex, diversion bare bank, diversion complex or upstream

complex in order to investigate finer scale differences in the suite of fishes present at these

various habitat types.

Monitoring Movement and Tagging 3.3.5

The tagging of bony fish has been conducted since 2007. The original aim of the tagging

program was to investigate the passage of fish through the diversion and several different

species were included in the program. Since that time Lates calcarifer and P. pristis have been

identified as key migratory species suitable to satisfy this PER objective and are now the focus

of the tagging program. Several MRM employees residing in the township of Borroloola were

trained in tagging procedures and have been provided with tagging kits for use on L. calcarifer.

In addition, MRM exchanged data with the managers of a separate tagging program run out of

King Ash Bay to maximise the information that could be collected. All tagged fish (and

recapture data) have been entered into a tagging database maintained by MRM. Teleost

species are tagged with individually numbered 40 mm (PDX) or 100 mm (PDS) straw style dart

tags (Hallprint fish tags) depending on size.

As mentioned P. pristis are recognised as a key migratory species that provide an indication of

the ability of fauna to traverse the rechannelled section of the McArthur River. Tagging of

captured P. pristis have also occurred for a number of years as part of the specific


management and monitoring regime put in place by MRM due the species conservation

significance. The tags used for this species are a cattle style tag which are supplied by the

Northern Territory Government Department of Primary Industry and Fisheries (DPIF) and is

placed in the first dorsal fin. This information gained has been used to investigate the

distribution and growth rates of P. pristis with all information as well as a genetic sample from

each animal provided back to the DPIF. At the time of drafting this report a new tagging study

was initiated which aims to use acoustic tags and a series of moored receivers to better

understand the movements of P. pristis and L. calcarifer.

Additionally the elasmobranch Carcharhinus leucas (Bull shark) is tagged on an opportunistic

basis using the method described for P. pristis. As with P. pristis individual C. leucas

information and genetic samples are also provided to DPIF.

Tissue Metals Analysis 3.3.6

Tissue samples of a variety of aquatic species have been collected since 2006 for the metal

tissue monitoring program outlined in Section 3.3. In that year the program was part of the

commitments made by MRM for the Phase 2 expansion involving the conversion of operations

from underground to open pit. A revised project plan which aimed to increase the robustness of

the environmental monitoring program was implemented in 2010 (Indo-Pacific Environmental

2010) which specified the collection of lower order fish species which would reflect the early

introduction of metals into the aquatic food chain and identified 12 survey locations in the

McArthur River and its tributaries from which samples would be collected annually. This

included Nematalosa erebi (Bony Bream), Melanotaenia splendida (Chequered Rainbowfish)

and Leiopotherapon unicolor (Spangled Perch) (Figure 5). The crustacean Macrobrachium spp.

(Giant Freshwater Prawn) and the mollusc Velesunio angasi (Freshwater Mussel) were also

collected when available. Reference samples of the aforementioned species were collected

from the Wearyan and Limmen Rivers in 2011.

In the Environmental Performance Annual Report 2012-2013 (ERIAS 2014) the IM discussed

the reported introduction of metals into Barney Creek directly below the haul road bridge on the

McArthur River Mine site and concerns around on going impact (see Indo-Pacific

Environmental 2012, 2013 and 2014 for original reporting and subsequent discussion). A

subsequent recommendation by the IM was that ‘Fish from a higher tropic level such as

Hephaestus fuliginosus (Sooty Grunter) or L. calcarifer (Barramundi) could be included in the

monitoring of metal concentrations in flesh, as these species are more likely to bioaccumulate

metals’ (see Table 4.49 of that report) (Figure 4). This recommendation by the IM was

considered to be a ‘Medium Priority’.


Figure 5. Species collected for metal and lead isotope analysis in the McArthur River, including

a) Nematalosa erebi, b) Melanotaenia splendida, c) Leiopotherapon unicolor and d)

Macrobrachium rosenbergii. Samples of e) Hephaestus fuliginosus and f) Lates calcarifer were

also collected in 2014.

In July 2014, the Northern Territory Government Department of Mines and Energy (DME) and

the Department of Health (DoH) raised subsequent concerns around the presence of metals in

fish collected below the Barney Creek haul road bridge and concurred with the IM that samples

of, in particular, H. fuliginosus and L. calcarifer should be collected and their tissues analysed.

This was due to the fact that these species were considered to be commonly consumed.

a b

c d

e f


In recognition of comments by the IM, DME and DoH, MRM commissioned Indo-Pacific

Environmental to conduct supplementary sampling of fish species which were considered to be

commonly consumed in July 2014. Prior to that work Indo-Pacific Environmental identified

potential survey locations for these species and sample numbers and referred back to the DME

for comment. In that year the DME also coordinated with the Northern Territory Government

Department of Primary Industry and Fisheries (DPIF) to collect and analyse tissues from a

comparable suite of fauna used in the existing monitoring program as well as L. calcarifer and

H. fuliginosus samples. Fish were collected from several of the same sites annually sampled by

MRM.

By 2015 the number of sites assessed and samples being analysed as part of the MRM

program had doubled in comparison to 2013. Based on comments by the DME and the IM the

monitoring program increased the focus on sites within Barney and Surprise Creeks. Both

environmental indicator species and higher order “food fish” were collected from locations

which can be readily accessed by the public such as the highway crossing of Surprise Creek.

Food fish were also collected from SW19 when available. In addition to a comparison between

sites, concentrations were also compared to the relevant Maximum Permitted Concentrations

(MPC) in foods outlined the Food Standards Australia New Zealand (FSANZ) (2009). In relation

to food fish the methodology outlines by FSANZ (2011) for conservatively calculating the

amount of tissue of a particular sample that could safely be eaten was also used to provide

additional context to these results.

Late in 2015, the DME commissioned an independent review of the data collected by both

Indo-Pacific Environmental and the DPIF (Hydrobiology 2016). This review, however, focused

on the ‘potential effects on human health from consumption of affected aquatic species’ as

opposed to the performance of the environmental monitoring program as per its design. That

report concluded that “the risk to human health posed by consumption of fish, prawns and

mussels from the McArthur River system is considered low”. Hydrobiology (2016) also

identified “ideal scenarios” in a gap analysis “in the context of human health risk assessment”

and acknowledged that the current program was designed to monitor effects on the

environment. Soon after the release of this report the DME issued an instruction to MRM (in

March 2016) which outlined that the “ideal scenarios” need to be addressed.

A response to the DME instruction was prepared by MRM and a revised methodology was

approved by the DME in May 2016. The revised methodology included the collection of

samples in both the early and late dry seasons, community consultation in regards to the

species of food fish collected and site locations for assessment, as well as biannual regional

sampling in the adjacent catchments of the Robinson and Limmen Bight Rivers.

Currently the early dry season program aims to collect samples of N. erebi, M. splendida, L.

unicolor, Toxotes chatareus, H. fuliginosus and L. calcarifer, as well as the crustacean


Macrobrachium spp. and the mollusc Velesunio angasi, from over 20 sites within the McArthur

River catchment. Additionally samples of these species are collected from two sites in the

Robinson River and two sites within the Limmen River. The late dry season program focuses

primarily on “food species” i.e. T. chatareus, H. fuliginosus, L. calcarifer, Macrobrachium spp.

and V. angasi from as many of the early dry season sample sites that retain water.

Additionally in 2015 MRM initiated a citizen science program for the collection of L. calcarifer

frames from interested members of the public. Information posters detailing the program along

with freezers, collection bags and information tags were distributed to various locations within

Borroloola and several outstations. Donated frames are periodically collected by MRM staff for

inclusion in the metals testing program. While data quality issues of this type of program are

acknowledged it has provided a conduit for returning results to specific members of the

community which also provides opportunity for information and discussion of the wider program

to be disseminated.

Ultimately, tissue samples collected are digested and analysed for a range of metals,

metalloids and lead isotope ratios (PbIR) through inductively coupled plasma mass

spectrometry (ICP-MS) and Cold Vapour Generation Inductively Coupled Atomic Emission

Spectrometry (ICP-AES). Results are subsequently compared between sample sites and the

recorded concentrations and PbIR used to determine whether MRM derived metals are present

in the aquatic food chain. In relation to fish which are commonly consumed concentrations of

any measured analyte are investigated using the FSANZ methodology for conservative

calculation of the amount of tissue of a particular sample that could safely be eaten.

Project Specific Fauna Investigation – Emu Creek 3.3.7

As noted in Section 1.3, one of the three major components of the Project is the expansion of

the North Overburden Emplacement Facility (NOEF), with much of the planned expansion

occurring on the northern side of the current NOEF site. Emu Creek which is located to the

immediate north of the NOEF was identified as being potentially impacted by the expanded

footprint. Furthermore, the proximity of Emu Creek to the expanded NOEF represented a

potential pathway for the direct introduction of contaminants into the main channel of the

McArthur River. In consideration that no previous information had been collected in regards to

fish diversity and population within this system a baseline survey of the aquatic fauna of Emu

Creek was undertaken in April 2015 to provide data against which a predictive impact

assessment and post-construction monitoring could be compared. Tissue samples for metal,

metalloid and lead isotope ratio (PbIR) analyses were also collected from the species

mentioned in Section 3.3.6 to facilitate baseline metal levels for this system. An expanded

methodology for the Emu Creek Fauna Investigation can be found in Appendix 1.


Macroinvertebrates 3.3.8

Macroinvertebrates have long been demonstrated to be effective indicators of environmental

health, and comparison of macroinvertebrate assemblages over time can be used to monitor

instream ecosystem change. Monitoring of biota can produce data that is more ecologically

meaningful than physico-chemical measurements, unless contamination or disturbance of

waterways is so severe that the implications of chemical results for the ecology of the river are

obvious (Halse et al. 2007). Macroinvertebrates were chosen as indicator organisms for the

MRM project as they are ubiquitous, have a relatively well-known taxonomy and are easily

sampled (Halse et al. 2007; Jones et al. 2008; Gustafsson et al. 2013).

In the Northern Territory, standardised AusRivAS models have been developed for the Darwin

- Daly region (Lamche 2007). There are however no models available for the eastern section of

the NT. Consequently, the Northern Territory Government recommended that sampling and

laboratory processing should be conducted following established AusRivAS protocols, while

data analysis should employ traditional statistical methods for the assessment of site

conditions and comparison, requiring identification of specimens to lower taxonomic levels.

At each site a range of standard surface water (field and laboratory), fluvial sediment, spatial

and habitat variables were measured during sampling. Environmental habitat variables

generally conform to standard NT and Queensland AusRivAS protocols (Lamche 2007, Lloyd

and Cook 2002). Surface water and fluvial sediment samples were analysed for a range of

parameters, including dissolved and fluvial sediment metals, major cations and ions,

temperature, pH, turbidity, dissolved oxygen, electrical conductivity, total dissolved solids and

turbidity. Environmental variables were measured to assess the extent of the potential impacts

on surface water and sediments by mining activities, the influence of natural habitat factors and

to enable interpretation of differences in macroinvertebrate assemblages between sites and

treatments.

Macroinvertebrate sample collection and laboratory processing closely follow established NT

protocols (Lamche 2007) with reference to Lloyd and Cook (2002) and Queensland

Department of Natural Resources and Mines (QDNRM) (2001) for sampling riffle habitats.

Each macroinvertebrate sample was collected using a 250 micron triangular mesh net with an

opening of 35 cm at the base. Each sample was collected over a 10 m section of habitat.

Samples were collected at edge habitats at all sites and riffle samples were collected if this

habitat was present at a site. The main departures from the Northern Territory AusRivAS

methodology were:

The sampling of habitats other than edge habitat, which is the principal focus of the NT

AusRivAS protocol (Lamche 2007); and

Identification of macroinvertebrate groups to a lower level than Family/Sub-family.


Analysis of the freshwater macroinvertebrate and water chemistry/habitat data were

undertaken using PRIMER-7 and PERMANOVA+ (Clarke and Gorley 2006; Anderson et al.

2008).

Aquatic Reptiles 3.3.9

Over the last five years records of aquatic reptiles have been retained when observed or

captured. In addition the total length of Acrochordus arafurae (Arafura file snake) and shell

length of turtles has been recorded.

Current Knowledge 3.4

General 3.4.1

A total of 47 species of fish have been recorded from freshwaters of the McArthur River above

the Burketown Crossing (Table 2). Twenty eight of these are considered to be freshwater

species, i.e. are capable of breeding in freshwater, while the remaining nineteen species are

estuarine vagrants. Of the estuarine vagrants recorded within the non-tidal waters of the

McArthur River three belong to the subclass Elasmobranchii (cartilaginous fishes). Specifically

Himantura dalyensis (formerly known as Himantura chaophraya) has been recorded close to

the Burketown Crossing while C. leucas and the EPBC Act listed P. pristis have been regularly

captured as far upstream as Eight Mile Waterhole.

In general, recent early dry season surveys consistently observe or capture 26 to 30 of these

47 species. However, as these surveys aim to produce the least mortality possible

Glossogobius and Oxyeleotris species are generally reported at a genus level as species

differentiation of these groups generally requires microscopical investigation of dead

specimens. As these congeners occupy a comparable ecological niche in the McArthur River

system it has been considered appropriate to record these species in this fashion and ensure

the successful live release of captured individuals. The number of species observed or

captured during late dry season surveys is less consistent (varying between 17 and 30

species), although further investigation shows this variation is directly related to the number of

locations retaining water in the later part of the year.

Baseline sampling conducted between 2006 and 2008, i.e. prior to the opening of the diversion,

indicated M. splendida to be the most abundant species occurring in the McArthur River during

both the early and late dry seasons. Leiopotherapon unicolor, Ambassis maclaeyi, Ambassis

mulleri, Amniataba percoides and Glossogobius giurus were also captured in high abundances

between 2006 and 2008. In recent years, species distribution data collected within the wider

McArthur River catchment has been seen to be comparable to those recorded during pre-

diversion investigations. During the most recent sampling event in May 2016, M. splendida was


Table 2. Fishes species recorded within the McArthur River. Species denoted with red have been recorded post 2012, species denoted with black have only

been recorded prior to 2012. Shading indicates estuarine vagrants.

Scientific Name CAAB Common Name

Area Recorded

Above Burketown Crossing

Immediately Below MRM

Surprise / Barney Cks

Within Diversion

Djirrinmini Eight Mile Upstream of Eight Mile

Carcharhinus leucas Bull Shark ● ● ●

Himantura dalyensis Freshwater Whipray ●

Pristis pristis Freshwater Sawfish ● ● ● ●

Ambassis macleayi Macleay's Glassfish ● ● ● ● ● ● ●

Ambassis mulleri Northwest Glassfish ● ● ● ● ● ●

Amniataba percoides Barred Grunter ● ● ● ● ● ● ●

Anodontiglanis dahli Toothless Catfish ● ● ● ● ●

Arrhamphus sclerolepis Snubnose Garfish ●

Brachirus selheimi Freshwater Sole ● ● ● ● ● ● ●

Chanos chanos Milk Fish ● ● ● ● ●

Cinetodus froggatti Smallmouth Catfish ●

Craterocephalus stercusmuscarum Flyspecked Hardyhead ● ● ● ● ● ●

Elops hawaiiensis Giant Herring ● ● ●

Gerres filamentosus Threadfin Silverbiddy ● ●

Glossamia aprion Mouth Almighty ● ● ● ● ● ● ●

Glossogobius aureus Golden Flathead Goby ● ● ● ● ● ● ●

Glossogobius giurus Tank Goby ● ● ● ● ● ● ●

Hephaestus fuliginosus Sooty Grunter ● ● ● ● ● ● ●

Lates calcarifer Barramundi ● ● ● ● ● ● ●

Leiopotherapon unicolor Spangled Perch ● ● ● ● ● ● ●

Liza alata Diamond Mullet ● ● ● ● ● ● ●

Liza subviridis Greenback Mullet ●


Scientific Name CAAB Common Name

Area Recorded

Above Burketown Crossing

Immediately Below MRM

Surprise / Barney Cks

Within Diversion

Djirrinmini Eight Mile Upstream of Eight Mile

Liza vaigiensis Diamondscale Mullet ● ● ●

Megalops cypinoides Oxeye Herring ● ● ● ● ● ●

Melanotaenia splendida Eastern Rainbowfish ● ● ● ● ● ● ●

Mogurnda mogurnda Northern Purplespotted Gudgeon ● ● ●

Nematalosa erebi Bony Bream ● ● ● ● ● ● ●

Neoarius paucus Shovelnose Catfish ● ● ● ● ● ●

Neoarius berneyi Highfin Catfish ● ● ● ● ● ●

Neoarius graeffei Blue Catfish ● ● ● ● ●

Neoarius leptaspis Boofhead Catfish ● ● ●

Neosilurus ater Black Catfish ● ● ● ● ● ● ●

Neosilurus hyrtlii Hyrtl's Catfish ● ● ● ● ● ● ●

Oxyeleotris lineolata Sleepy Cod ● ● ●

Oxyeleotris selheimi Blackbanded Gudgeon ● ● ● ● ● ● ●

Oxyeleotris sp A Gudgeon ●

Pisodonophis boro Estuary Snake Eel ● ● ● ●

Porochilus rendahli Rendahl's Catfish ●

Rhinomugil nasutus Popeye Mullet ●

Selenotoca mutlifasciata Striped Scat ●

Scatophargus argus Spotted Scat ●

Scomberoides commersonnianus Giant Queenfish ●

Scortum ogilibyi Gulf Grunter ● ● ● ● ● ●

Strongylura kreffti Freshwater Longtom ● ● ● ● ● ● ●

Valamugil buchanani Bluetail Mullet ●

Toxotes chatareus Sevenspot Archerfish ● ● ● ● ● ● ●

Zenarchopterus novaeguineae Fly River Garfish ●


again found to be the most numerous fish species encountered followed by L. unicolor,

Oxyeleotris selheimi, Nematalosa erebi, Glossobius spp. and A. percoides.

Fauna in Natural and Modified Habitats 3.4.2

McArthur River 3.4.2.1

The introduction of large woody debris was considered to be a vitally important rehabilitation

strategy for aquatic habitats within the diversion. Large woody debris not only provides habitat

and protection for smaller (prey) species but encourages the deposition of river sediments.

Sandy (as opposed to rock) benthos is known to favour a number of species occurring in the

McArthur River. Furthermore accumulated sediments which advance up the banks of the

diversion provide establishment sites for riparian vegetation.

Woody debris has been introduced into the diversion since June 2010 and was shown to be

immediately effective in providing aquatic habitat with both species diversity and abundance

being found to be vastly higher in woody debris sections as opposed to bare bank sections of

the diversion (see Indo-Pacific Environmental 2011). This can be seen graphically in Figure 6.

This result was compounded by the fact these fauna densities were recorded after woody

debris had been in place for only four months. Despite being the most numerous fish in the

McArthur River, M. splendida was not recorded in the diversion prior to this time despite

significant survey effort being undertaken.

Figure 6. Density of fish species (mean number per metre) recorded form electrofished

transects in woody debris and adjacent areas of open bank in 2010.

In late 2014 the scale of woody debris introduction was seen to vastly increase with intensive

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remediation works conducted over a large area in the lower section of the diversion (See Indo-

Pacific Environmental 2015). Not only did these works include the placement of large volumes

of woody debris but large earth moving equipment entered the channel allowing woody

debris to be placed throughout the channel (as opposed to placing large piles on the edge of the

channel from the banks) at varying densities. Furthermore, this allowed logs to be particularly

buried in the river bed and along the banks which resulted in undulation and varied flow which

was rare in the diversion. In terms of functional morphology this area was subsequently

considered closer to that of the naturally occurring sections of the McArthur River upstream and

downstream of the diversion.

In light of the scale and method woody debris was emplaced data on fauna abundances

collected during that survey were subjected to finer scale analyses. In particular sites surveyed

were categorised as either downstream bare bank, downstream complex, diversion bare bank,

diversion complex (i.e. the lower section of the diversion recently remediated) and upstream

complex habitats. Figure 7 provides a comparison of the fish densities found in the various

habitats analysed in the early dry season 2015. As can be seen the suite of species present in

the complex diversion habitat is generally comparable to that occurring in naturally vegetated

sections up and downstream. The highest abundance of fish captured whilst electrofishing

during that study was at complex habitat (naturally vegetated) sites downstream of the

diversion with 3.13 fish per metre recorded whilst 2.59 fish per metre were captured from

upstream complex sites. The density of fish captured in the complex habitat created by MRM in

the diversion was found to be only marginally lower at 2.37 fish per metre. This provided a clear

indication that the method used and extent of area LWD was introduced provided effective fish

habitat. As reported by Indo-Pacific Environmental (2015a) this result was further compounded

by the fact that the ‘complexity and extent of the structure resulted in very high numbers of fish

being present and which on occasion were too high to accurately quantify’ and as a result, ‘fish

abundances were considered to be far higher than those recorded’

Barney and Surprise Creeks 3.4.2.1

Increased survey effort in Surprise and Barney Creeks (which flow through the mine lease) has

occurred since 2014 following requests to understand possible anthropogenic effects on

aquatic fauna diversity and densities. Since that time these two systems have been routinely

investigated from the convergence with the McArthur River upstream to SW 28 in the case of

Barney Creek and SW 23 in the case of Surprise Creek. Furthermore naturally vegetated sites

which have not been realigned within Barney Creek and sites within the Barney Creek

diversion channel have been compared in order to assess the performance of the Barney

Creek diversion. The most recent data indicates that sites within Surprise Creek have the

highest diversity with 16 species recorded followed by Barney Creek diversion sites (14 species

recorded) then natural Barney Creek sites (eight species recorded). In 2016 M. splendida was


found to be the dominant species accounting for 43.94% of fish captured followed by L.

unicolor and O. selheimi which accounted for 13.54% and 11.16% of total captures,

respectively. In general, surveys of Barney and Surprise Creeks indicated a comparable suite

of dominant species to that occurring in the McArthur River although the proportion of M.

splendida was found to be substantially higher in these Creeks.

Figure 7. Mean number of fish and crustaceans captured per metre whilst electrofishing at sites

downstream the diversion, bare bank sites within the diversion, complex habitat sites within the

diversion and complex habitat sites upstream of the diversion during April 2015.

Emu Creek Fauna 3.4.3

A full account of the April 2015 survey of Emu Creek can be found in Appendix 1. During that

survey a total of 13 finfish species were recorded with 12 of these being routinely recorded

throughout the main channel of the McArthur River. The exception was Mogurnda mogurnda

which has been found to occur almost exclusively in tributaries of the McArthur River including

Surprise and Barney Creeks. Comparable to the main channel of the McArthur River the most

numerous species was found to be M. splendida, comprising 32.8% of the total fish captured,

and which was present at five of the eight sites at which fish were found. Length frequency data

for M. splendida, N. erebi and L. unicolor collected during the study indicated the predominance

of juvenile and sub adult individuals. Only one adult Neosilurus hyrtlii (445mm TL) and two near

adult Strongylura krefftii (460mm and 370mm TL) were captured. In addition to the limited

water present at the time of the survey, this size data also suggests that Emu Creek contains

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Diversion Bare Bank (320M)

Diversion Complex (256M)

Upstream Complex (230M)


little permanent water and thus was highly seasonal in nature. Recruitment would subsequently

occur annually with fish coming from the McArthur River when flow is present.

Results of metal, metalloid and PbIR tissue analysis did not indicate Emu Creek fauna was

being influenced by MRM’s mining operations to any measurable extent. Results of metal,

metalloid and PbIR tissue analysis did not suggest mine derived lead was present in aquatic

fauna.

Metal Concentrations in Fauna 3.4.4

As noted in Section 3.3 the primary aim of this program is to detect if metals, as a result of

processes conducted by MRM, are entering the aquatic food chain. Monitoring to date has

found that no muscle, trunk or liver sample taken from fish in the McArthur River main channel

has contained lead in excess of the 0.5 mg/kg MPC for fish (FSANZ 2009) as a result of mining

operations. In fish which are commonly consumed the highest recorded concentrations of lead

in muscle throughout the survey area (including Barney and Surprise Creeks) have been found

to be vastly lower than the 0.5 mg/kg MPC. For example, in 2016 the highest lead in muscle of

H. fuliginosus was found to be 0.009 mg/kg which is 55 times lower than the MPC.

Furthermore, the lead concentration in muscle of L. calcarifer in 2016 were found to be equal or

less than the detection limit of analysis (i.e. 0.002 mg/kg) including several individuals captured

at SW19.

The current monitoring program includes a number of survey sites on the McArthur River Mine

lease including within Barney and Surprise Creeks. As discussed in Section 3.3.6 data

collected in 2012 gave the first indication that lead and to a lesser extent zinc was entering the

food chain at SW19, which is a surface water monitoring point located directly below the haul

road bridge on the Barney Creek diversion. Monitoring in 2013 also reflected the presence of

mine derived lead with nine of the ten M. splendida collected from SW19 seen to exceed the

MPC of 0.5 mg/kg and as high as to 4.7 mg/kg (Figure 8). Concentrations of all fauna from this

location were also seen to be significantly higher than mean lead concentrations in fauna

collected from other survey sites.

Lead in fish tissue was found to be closely correlated to sediment lead at SW19. The source of

the lead at SW19 was subsequently attributed to dust generated from the haul trucks and road

runoff from the haul road. In light of the above findings a number of management actions were

implemented in late 2013 and 2014 to stop the ingress of lead laden sediments into Barney

Creek at SW19. This included the installation of silt traps, a small bund to slow the flow into the

McArthur River main channel and mechanical excavation and removal of sediment from SW19

(Figure 9). The implementation of these recommendations was subsequently seen to reduce

the lead concentrations of fauna collected at SW19 in 2014 and further works, including the

removal of sediment high in lead concentrations from the creek bed, saw further improvements


in 2015 (Figures 8 and 10). Sampling in 2016 has shown further improvement with lead

concentrations in fauna at SW19 eight to ten times lower than 2013 results (Indo-Pacific

Environmental 2016).

Figure 8. Comparison of mean lead concentrations (mg/kg wet weight) in M. splendida

collected throughout the McArthur River catchment between 2012 and 2015.

Figure 9. Sediment trap to catch flow off haul road (top), low bund at the downstream end of

SW19 (bottom left) and result of excavation of SW19 in the late dry season 2016 after flow has

completely ceased showing complete removal of sediment derived from dust and runoff

(bottom right).

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Figure 10. Lead concentration (mg/kg) in the <63 µm sediment fraction recorded from surface

water monitoring sample sites in the vicinity of McArthur River mine between 2011 and 2016.

In relation to commonly consumed species the early dry season 2016 results indicated that of

36 H. fuliginosus collected ~70% had muscle lead tissue concentrations which were less than

or equal to the detection limit of analysis (i.e. ≤0.002 mg/kg). While the highest mean lead

tissue concentrations in H. fuliginosus were found to be from sites within Barney (SW19) and

Surprise Creeks (SW2), being 0.009 mg/kg 0.008 mg/kg, respectively, these values are 55

times lower than the MPC of 0.5 mg/kg. The highest lead concentration in muscle in any

individual found in that year was 0.021 mg/kg. At a concentration of 0.021 mg/kg, it was

determined that an average adult could eat 3.8 kg of muscle tissue (fillet), which equated to

~19 individual fish, per day before approaching a lead intake that is considered by the world

health organisation to cause harm (see FSANZ 2011). In relation to mean lead concentration in

H. fuliginosus livers, individuals from SW19 were shown to have the highest mean

concentration at 0.195 mg/kg. While this is higher than that recorded in muscle tissue it

remained well below the MPC. This was also far lower than the highest mean concentration

recorded in livers of this species collected in 2015 being 0.783 mg/kg.

All L. calcarifer muscle tissue tested in the early dry season of 2016 returned lead

concentrations which were equal to or less than the reporting limit for analysis of 0.002mg/kg

i.e. at least 250 times below the MPC of 0.5 mg/kg. This included individuals captured from

SW19. The mean concentration of lead in liver of L. calcarifer from SW19 was found to be

higher than that recorded at other survey sites being 0.098 mg/kg. Based on the FSANZ (2011)

methodology an adult male would need to consume approximately 800 grams of L. calcarifer

liver tissue (or approximately 16 individuals of the size captured from this location) per day

0

500

1000

1500

2000

2500

Aug 2011 June 2012 Aug 2013 Aug 2014 May 2015 April 2016

Co

nce

ntr

atio

n (m

g/k

g)

SW21

SW7

SW16

SW23

SW2

SW3

SW18

SW19

SW11


before approaching lead intake that is considered by the world health organisation to cause

harm. Obviously this prospect would be considered to be unrealistic.

The analysis of tissue from fish species which occupy lower parts of the aquatic food chain has

proven to be an effective method for identifying the early introduction of metals in the aquatic

food chain. As was the case at SW19 the early identification of an introduction and immediate

and effective management has far reduced the uptake of metals in aquatic fauna.

Tagging of Teleost Species 3.4.5

Since 2011, tagging of teleost species has primary focussed on L. calcarifer as many of the

other species proved to have limited migratory habits and thus did not add to the body of

knowledge of fish passage through the diversion. Of interest, several of those individuals

tagged in the pre-2011 program continue to be regularly recaptured. For example, several

Neoarius paucus (Shovelnose Catfish) tagged in 2007-2009 have now been recaptured up to

four times in the following years with recaptures as recent as April 2016. In relation to L.

calcarifer, over 390 individuals have been tagged as part of the MRM program. There have

been 15 recaptures of these animals, with time at liberty ranging from 12 to 59 months. Three

L. calcarifer tagged upstream of MRM have been re-captured in later years near the mouth of

the McArthur River, indicating movement downstream through the diversion. Interestingly some

specimens of similar size and tagged at the same locations as these three fish have been

recaptured in the original tagging area indicating not all individuals have emigrational

tendencies. As noted in Section 3.5.5 L. calcarifer was added to the suite of species sampled

for tissue metal analysis in 2014. Since that time the numbers of animals being added to the

tagging program has fallen from approximately 40 individuals per year to less than five. This

has prompted the inclusion of a limited number of L. calcarifer in the upcoming acoustic tagging

trial which was initiated in late 2016.

Fish of Conservation Significance 3.4.6

A total of 45 records (including 33 captures and three recaptures) of P. pristis have been

collected between March 2006 and October 2016 (Table 3, Figure 11 and Appendix 2). Since

2007 32 individuals have been tagged as part of the MRM monitoring program. There have

been three recorded recaptures of these animals with the longest time at liberty being 24

months in which time the individual grew from 1040 mm to 2040 mm. The majority of animals

captured in the vicinity of and upstream of MRM have been one to two year old animals which

use this habitat for foraging and growth away from the majority of large predators. The capture

of young animals upstream of the diversion indicates the species is able to successfully

negotiate this passage given sufficient water level. In recent surveys there have been notable

larger animals between 2.5 and 2.8 m captured in the vicinity of the Burketown Crossing which


may suggest these animals are in the process of migrating downstream to continue their adult

life.

Capture rates suggest that the recruitment of juveniles appears correlated to the magnitude

and duration of the wet season, i.e. greater numbers are encountered after large wet seasons.

Sustained waters of a long wet season facilitate upstream recruitment by a) providing

increased depth and thus reduced obstruction by barriers including rock bars, sand bars and

barrages, and b) the extended time available for upstream migration. The rainfall associated

with the 2006/2007 and 2007/2008 seasons was below average and captures of P. pristis in

those years were low. In contrast, the 2008/2009, 2009/2010, 2010/2011 wet seasons were

large. The fact that sampling during 2009, 2010 and 2011 resulted in the collection of ten,

seven and five records for the species lends credence to this hypothesis. Average to poor wet

seasons since 2011 have seen one to three specimens consistently captured per survey.

While the reported recapture rate (i.e. 11%) represents a very good return rate for this type of

tagging program, it does highlight the limitations of this technique for tracking movements of a

species when the overall population available for tagging is very low. As such, acoustic tagging

was considered to be an effective way to attain movement data without the need to recapture

the animal. In 2016 MRM initiated an acoustic tagging program which saw ten acoustic listening

stations deployed throughout the McArthur catchment. Pristis pristis captured in the future will

subsequently be fitted with acoustic transmitters as well as the traditional cattle-style tag used to

date. This program will be run with the assistance of the Li-Anthawirriyarra rangers and

incorporate community engagement to increase the success of the program.


Table 3. Records of Pristis pristis in the McArthur River since 2006. Records include tag

number, date recorded, location, sex, total length (TL mm), rostrum length (RL mm) and tooth

count of the right and left sides.

Tag Location Date TL RL R (tooth) L (tooth) Sex

- Eight Mile Waterhole 8-May-06 998 248 21 22 M

1801 Upstream Burketown Crossing 4-May-07 920 222 21 21 F

1802 Glyde River 22-Oct-07 1040 250 16 18 F

1803 Djirrinmini Waterhole 19-Sep-09 1150 275 19 19 F

1804 Eight Mile Waterhole 20-Sep-09 1100 270 21 22 M

1805 Upstream Burketown Crossing 21-Sep-09 1125 280 20 21 M

1806 Upstream Burketown Crossing 21-Sep-09 1160 285 19 21 F

1807 Eight Mile Waterhole 29-Apr-10 1710 380 22 21 M

1808 Downstream Burketown Crossing 30-Apr-10 970 240 19 19 F

1809 Djirrinmini Waterhole 7-May-10 970 235 21 22 M

1814 Djirrinmini Waterhole 4-May-12 880 230 20 21 F

1819 Djirrinmini Waterhole 1-Dec-06 980 250 19 20 F

1824 Djirrinmini Waterhole 19-Apr-09 924 225 21 21 M

1825 Djirrinmini Waterhole 19-Apr-09 940 235 20 19 F

6401 Eight Mile Waterhole 8-Sep-10 1280 320 - - M

6406 Downstream Burketown Crossing 9-Sep-10 1210 290 21 21 M

6407 Eight Mile Waterhole 3-May-11 1060 250 20 20 F

6408 Eight Mile Waterhole 3-May-11 1030 250 22 23 M

6410 Downstream Burketown Crossing 6-May-11 1040 250 22 22 M

6411 Upstream Burketown Crossing 7-May-11 2070 450 23 21 M

6414 Upstream Burketown Crossing 20-Oct-11 1040 - 21 23 M



6430 Upstream Burketown Crossing 9-Sep-12 1470 365 19 19 F


6459 Diversion 30-May-14 945 225 20 21 M


6462 Djirrinmini Waterhole 16-Nov-14 1380 - 22 22 M

6482 Downstream Burketown Crossing 1-Dec-15 2550 560 20 19 M

6483 Downstream Burketown Crossing 2-Dec-15 2540 570 21 21 M

6484 Diversion 16-Apr-16 900 240 20 20 F

6485 Diversion 16-Apr-16 920 250 23 22 M

6487 Downstream Burketown Crossing 9-Oct-16 2750 620 22 21 F

Recaptures


Tag Location Date TL RL R (tooth) L (tooth) Sex

1805 Upstream Burketown Crossing 19-Sep-10 1666

6414 Upstream Burketown Crossing 28-Oct-13 2040

6459 Diversion 16-Nov-14 980 240 20 21 M

Other observations

Found on bank At Burketown Crossing May-07 ~950 - - - -

Found on bank At Burketown Crossing 26-Apr-09 930 - - - -

Found on bank Diversion Dec-09 ~820* - 21 19 M

Free swimming Eight Mile Waterhole 8-May-06 998 248 21 22 M

Free swimming Downstream Burketown Crossing Jun-07 ~1000 - - - -

Free swimming Diversion 25-Apr-09 ~950 - - - -

Free swimming Diversion Nov-09 - - - - -

Free swimming Glyde River May-10 - - - - -

Free swimming Downstream Burketown Crossing 9-Sep-10 ~1200 - - - -


Macroinvertebrates 3.4.7

Combined results of family-level taxa recorded during the macroinvertebrate sampling program

between 2012 and 2016 are presented in Appendix 3. Key results from the analysis of the

macroinvertebrate data undertaken for the project to date (EMS 2016) are described below.

Surprise Creek/Barney Creek Diversion 3.4.7.1

There is evidence of a gradient of elevated metals (e.g. Cu, Pb, Zn), sulphate and other

parameters (particularly variables related to soluble salts and salinity) associated with surface

waters and sediments in the Surprise/Barney Creek system (EMS 2016). Results for the 2016

sampling period indicate that some of these parameters were particularly high at sites adjacent

to the mine processing areas, on the Barney Creek diversion and in the vicinity of and

downstream of the Barney Creek Bridge. Impairment and impacts on biota

(macroinvertebrates) were evident at these sites.

The results of macroinvertebrate monitoring since the construction of the Barney Creek

diversion indicate that diversion macroinvertebrate communities are significantly different to

those present at off-stream reference sites of the same stream order. Impacts on

macroinvertebrate communities are illustrated by significant negative correlations between the

number of macroinvertebrate taxa in response to increasing levels of key variables (e.g. Cu,

Pb, sulphate). These relationships are less pronounced during years when improved seasonal

flow conditions act to dilute pollutants.

Levels of impairment in the macroinvertebrate communities at Surprise/Barney Creek sites are

potentially related to abnormal structural habitat characteristics in the constructed diversion,

combined with the presence of elevated levels of sediment, metals and salts (indicated by

elevated major cations and anions, EC, sulphate).

McArthur River Diversion 3.4.7.2

Analysis of data compiled between 2008 and 2016 has indicated that riffle sites within the

McArthur River diversion resembled reference conditions in terms of macroinvertebrate

assemblages and riffle structure within two years of operation. However, the data indicates that

habitats and associated (macroinvertebrate) biota within the diversion have reduced resilience

to impacts from extreme flood events and dry periods (EMS 2016). These events have been

found to have an elevated/extended impact on macroinvertebrate assemblages within the

diversion when compared to reference sites.

Reduced resilience may be linked to the diversion channel constraining flow during extreme

flood events. Restricted rates of recolonisation following natural disturbance or dry periods

may also be influencing the rate of macroinvertebrate assemblage recovery, with recovery

rates decreasing at greater distance from intact upstream habitats.


Macroinvertebrates at edge habitats within the McArthur River diversion have not recovered in

the same manner as those at riffle habitats. In some cases macroinvertebrate diversity has

increased to near reference edge levels, but analysis of the composition of the assemblage has

indicated that a proportion of the typical edge/lentic taxa are missing. These species have been

replaced by an atypical group of lotic species that are generally associated with flowing water

and habitats with rocky substrates. This change is related to a number habitat factors within the

diversion, including rocky nature of the artificial edges and the reduced area of slack-water

along the channel margin.

The recovery of macroinvertebrate assemblages following construction of an artificial channel

can require extended time periods, particularly where development of riparian vegetation has a

role in establishing instream habitat characteristics on the channel margins (Becker & Robson

2009; Louhi et al. 2011). As a result, the convergence of the edge habitat macroinvertebrate

assemblage within the diversion with reference (natural) edge habitats is likely to occur over an

extended period.

A prerequisite for the re-establishment of typical edge macroinvertebrate assemblages at

diversion sites is the development of habitat conditions that occur in the presence of

established riparian vegetation, including cover of stabilising root mats, overhanging banks,

woody debris/litter and shading canopy cover.

There appear to have been small improvements in edge macroinvertebrate communities within

the McArthur River diversion in 2016, particularly at sites on the upper diversion where planting

of bankside riparian species has progressed, and at sites on the lower diversion where woody

debris was placed within the channel. The woody debris placement appears to have been

successful in creating variation in flow and micro-habitat within the channel which is beneficial

for invertebrate (and vertebrate) fauna.

Aquatic Reptiles 3.4.8

Both Crocodylus porosus (Estuarine Crocodile) and Crocodylus johnstoni (Freshwater

Crocodile) (Figure 12) have been frequently encountered whilst sampling throughout the

McArthur River catchment (Figure 13). Crocodylus johnstoni was generally observed in non-

tidal freshwaters with a number of records collected from waters on or adjacent the MRM lease

including within the diversion and Surprise Creek. Whilst less frequently observed in non-tidal

freshwaters C. porosus has also been recorded in close proximity to MRM and upstream

including at Djirrinmini Waterhole and Eight Mile Waterhole. Several unconfirmed reports of

sightings of C. porosus within the deeper sections of the diversion have also been collected.

Acrochordus arafurae (Arafura File Snake) has been frequently captured in fyke nets and

observed whilst electrofishing in waters on and adjacent the MRM lease (Figures 12 and 14).

Measured individuals have been up to 1.5 metres total length.


Emydura subglobosa worrelli (Worrell’s Short-necked Turtle) has been frequently recorded

entering fyke nets set over night. Numerous records have been collected throughout the

McArthur River catchment (Figures 12 and 15) including waters of the diversion. At times the

species has been captured in very high abundance. For example thirty individuals were

captured in one night in fyke nets set upstream of MRM at Cattleyard Waterhole in April 2016.

In contrast, only three records of Chelodina rugosa (Northern Snake-necked Turtle) have been

recorded since 2012 (Figures 12 and 15). Two of these records are on the mine lease with one

being from a surface water (SW) monitoring site on Barney Creek (SW3).

As discussed Elseya lavarackorum (Gulf Snapping Turtle) is afforded protection under the EPBC

Act. This species appears to be confined to the larger river systems of the Gulf of Carpentaria and

has been recorded in the Nicholson River, Gregory River, Calvert River and Robinson River (to the

east of the McArthur River), as well as in the Roper River and Limmen Bight River (to the west of

the McArthur River) (Department of the Environment and Energy 2017). Furthermore, E.

lavarackorum has been noted to inhabit deep permanent freshwater pools within the middle

reaches of river systems, favouring steep rocky gorges and banks with intact vegetation. In

consideration of these habitat preferences, waters of the McArthur River adjacent to MRM would

not be considered to be favourable to this species. This is due to the fact this section of river lacks

gorges and dries to a series of small, shallow isolated pools by the late dry season. Indeed,

intensive surveying of the McArthur River and its tributaries over the last decade (including over

300 days of effort capturing and documenting aquatic vertebrate fauna) has not recorded this

species.


Figure 12. Clockwise from top left Emydura subglobosa worrelli, Chelodina rugosa, Crocodylus

johnstoni and Acrochordus arafurae.


ECOLOGICAL IMPACT ASSESSMENT 4.0

Assessment Process and Risk Identification 4.1

Effective risk management requires the potential impacts of an action to be clearly identified

and that existing knowledge of the receiving environment and fauna present is sufficient to

make informed decisions. Potential impacts of the Project were based on the description

outlined in Chapter 3 of the Project EIS ‘Project Description and Justification’. Consistent with

the Project description assessment of potential impacts on aquatic fauna were considered in

relation to broad ‘domains’ which included:

Open Cut;

North Overburden Emplacement Facility (NOEF); and

Tailings Storage Facility (TSF);

The risk assessment requirements for the Project were identified in the Terms of Reference

(TOR) for the McArthur River Mine – Overburden Management Project drafted by the Northern

Territory Environment Protection Authority (NTEPA) in September 2014. The TOR states that

the ‘risk assessment should be based on international best practice. Processes for risk

management are formalised in Standards Australia / Standards New Zealand (e.g. AS/NZS

ISO 31000:2009; HB 436:2004; HB 158:2010; HB 203:2012).’

ISO 31000 for risk management describes a staged process for risk management, which

includes the following elements:

Establishing the Context

Risk Identification

Risk Analysis

Risk Evaluation

Risk Treatment

Risk Monitoring

Based on this, the approach taken to assess potential impacts on aquatic fauna was therefore

to quantify the risk using a combination of likelihood and consequences to determine the

inherent risks of an action (i.e. before the application of any risk mitigation measures) and

residual risks after the application of any risk mitigation measures. Tables 4 and 5 outline the

likelihood and consequence definitions used during the current study. Likelihood definitions are

consistent with those of the Glencore’s Corporate Risk Framework. Whilst this Framework was

also referred to for consequence definitions these definitions were augmented with those


outlined by the ‘Leading Practice Sustainable Development Program for the Mining Industry’

(Department of Resources Energy and Tourism 2008). This was due to the fact the

environmental consequence definitions in the Glencore Corporate Risk Framework are very

broad and contained few criteria. As such these were not considered appropriate to assess the

risk of impact to a sufficient level when considering potential effects on a complex aquatic

ecosystem. Table 6 indicates the risk rating matrix which is based on the Glencore’s Corporate

Risk Framework.

Table 4. Likelihood Definitions

Basis of Rating E - Rare D - Unlikely C - Possible B - Likely A - Almost

certain

Lifetime Unlikely to

occur during

lifetime

Could occur about once during a lifetime

Could occur more than once during a lifetime

May occur about once per year

May occur several times per year

or or or or or or

Project or trial

or fixed time

period

Very unlikely to

occur

More likely NOT to occur than to occur

As likely to occur as not to occur

More likely to occur than not occur

Expected to occur

or or or or or or

New process /

plant / R&D

No known

occurrences in

broader

worldwide

industry

Has occurred at least once in broader worldwide industry

Has occurred at least once in the mining / commodities trading industries

Has occurred at least once within Glencore

Has occurred several times within Glencore

Table 5. Environment Consequence Definitions.

Consequence Description

5 - Catastrophic Serious long-term impairment of ecosystem function

Off lease

Local extinctions are imminent/immediate or population no longer viable

Long term and possibly irreversible damage to one or more ecosystem

functions

4 - Major Extensive deleterious effect on valued ecosystem component with medium-

term impairment of ecosystem function.

Off mine lease, d/s catchment

Measurable changes to the ecosystem components with a major change in

function

Detectable change to population size and/or behaviour, with no detectable


impact on population viability, or dynamics

Recovery 5-20 years

3 - Moderate Deleterious effect on valued ecosystem component

Within mine lease

Measurable changes to the ecosystem components without major change

in function


impact on population viability

Recovery 1-5 years

2 - Minor Minor localised or short-term effects

Within domain

Measurable changes to the ecosystem components without major change

in function


impact on population viability

Recovery 6-12 months

1 - Negligible No observable effect

No detectable change outside natural variation/occurrence

Table 6. Risk Rating Matrix. Risk classifications include L: Low, M: Moderate and H: High.

E - Rare D - Unlikely C - Possible B - Likely A – Almost Certain

5 Catastrophic 15 (M) 19 (H) 22 (H) 24 (H) 25 (H)

4 Major 10 (M) 14 (M) 18 (H) 21 (H) 23 (H)

3 Moderate 6 (L) 9 (M) 13 (M) 17 (H) 20 (H)

2 Minor 3 (L) 5 (L) 8 (M) 12 (M) 16 (M)

1 Negligible 1 (L) 2 (L) 4 (L) 7 (M) 11 (M)

The TOR outlined a series of ‘Environmental Objectives’ (NTEPA 2014). When conducting this

risk assessment these objectives were referenced with those for water, biodiversity, and

rehabilitation and mine closure considered particularly relevant when assessing the potential

impacts to aquatic fauna and habitat. The Environmental Objectives included:

Water

Ensure that ground and surface water resources and quality are protected both

now and in the future, such that ecological health and land uses, and the

health, welfare and amenity of people are maintained.

Biodiversity


To maintain the conservation status, diversity, geographic distribution and

productivity of flora and fauna at species and ecosystem levels through the

avoidance or management of adverse impacts; and

To minimise the risk of significant impacts to EPBC Act listed threatened

species and communities during construction, operation and closure of the

altered Project

Rehabilitation and Mine Closure

As far as practicable, rehabilitation achieves a stable and functioning landform

which is compatible with the surrounding landscape and other environmental

values; and

The risks associated with closure and rehabilitation of the Project, including the

ongoing generation of AMD and contamination of the downstream

environment, can be mitigated

In determining management controls, the following hierarchy of control principles was also

adopted:

Elimination of the Hazard;

Substitution with a lower risk activity or product;

Engineering solutions to reduce the impact of the Hazard;

Implementation of administrative procedures to control the Hazard; and

Clean up or remediation measures to mitigate impacts after an event.

Risk Assessment 4.2

Table 7 presents the ecological risk assessment undertaken in relation to aquatic fauna. A total

of 26 project aspects were identified based on the project description provided by METServe

(2016). In addition to mitigation measures outlined in the project description this risk

assessment considers additional measures defined in this report. Expanded discussion of

these measures is outlined in Section 5.0.

Rankings and the justifications applied to these risks were also based on the project description

and relied heavily on model predictions provided being accurate. Deviation from the modelled

predictions will ultimately affect these outputs. From this perspective it is considered critical that

ongoing monitoring be conducted to determine the accuracy of the model predictions and for

subsequent risk assessments to be undertaken in the event model predications are found to be

inaccurate.


Table 7. Environmental Risk Assessment indicating rankings (R) for inherent risk (based on existing mitigation and management actions) and residual risk (based on existing and additional mitigation and management actions). Risk rankings

were quantified by comparing the likelihood (L) and consequence (C) definitions outline in Section 4.1. Proposed new project aspects (which has no existing mitigation or management) are indicated by N/A. Justifications are based on

information provided by MRM. These justifications rely heavily on model predictions. As such, deviation from the modelled predictions may ultimately affect these outputs.

Existing Inherent Additional Residual

# Activity/Aspect and Potential Hazard Potential Impact Mitigation and Management L C R Mitigation and Management L C R Justification

Open Cut: Operation

1 Discharge of contaminated site waters into Barney Creek and McArthur River.

- Reduction in water quality at discharge point and downstream including the McArthur River.

- Localised effect on habitat quality and fauna from, for example, elevated metal concentrations, sulphates or changes in pH.

- Exceedance of Site Specific Trigger Values (SSTVs) at SW11.

- Adherence to Waste Discharge Licence (WDL) conditions and discharge of waters with the appropriate dilution ratio. The WDL outlines specific discharge locations, various waters which can be discharged and environmental objectives. Conditions include: - Prior to discharge water quality assessment

determines discharge frequency and rate; - Periodic monitoring is conducted during

discharge; - Discharge conducted only when receiving

waters are at sufficient flow to facilitate mixing and contaminant dilution; and

- Monitoring of McArthur River water quality downstream at SW11 and adherence to SSTV’s.

C 1 4 (L) - Treatment and/or storage of ‘high risk’ waters (i.e. Class 4-6 as per WRM 2016).

- Adherence to annual Water Management Plan (WMP).

- New water treatment (WTP) plant will operate from mid-2017 to treat poorer quality mine affected water. Process will include coarse filtration, oxidation and precipitate filtration, reverse osmosis and pH correction (WRM 2016).

- Strategy to pump excess poor quality waters to the pit void if the water management system cannot cope and an environmental impact could be expected if waters were released.

C 1 4 (L) - Demonstrated adherence to WDL conditions and compliance at SW11 including SSTV’s.

- Low risk of large volumes of high contaminant concentrations being released. In the event ‘high risk’ waters are unintentionally released, discharge volumes would be small and likely loads highly diluted under flood conditions.

- Incident reporting and investigation (including any remedial works recommendations) in the event SSTV’s are exceeded.

2 Mining below groundwater level leads to drawdown in adjacent McArthur River and creeks.

- Reduced river height and groundwater supplementation.

- Reduced water level in refuge pools in the late dry season including Djirrinmini Waterhole.

- Reduction in habitat availability and loss of ecological function.

A 3 20 (H) - Assessment of drawdown effects during mining phase including change in river height and fauna response. This should include a comparison to historical dry season water heights at permanent waterholes (e.g. Djirrinmini Waterhole).

- Supplementary flow provided to permanent refuge pools such as Djirrinmini Waterhole should water levels be found to be atypical of seasonal variation.

C 3 13 (M) - Drawdown predicted to occur during mining and pit filling phases (up to 2047).

- Modelling predicts groundwater drawdown at Djirrinmini to be a maximum of 0.7 m and that recovery will occur within ten years after termination of mining (KCB 2016a). As a majority of Djirrinmini has less than two metres water depth in the late dry season, a decrease of 0.7 m will reduce available habitat. Supplementary flow may be used to maintain water levels during the period of peak drawdown to maintain habitat present.

- Modelling predicts pit drawdown decreases rapidly once pit filling has commenced (KCB 2016b).

3 Increased rate of production and higher frequency of heavy vehicles movements on haul road increase dust and runoff into Barney and Surprise Creeks.

- Increase in total suspended solids (TSS) and metals in surface water and sediments.

- Subsequent increase in metal concentrations in creek sediment and uptake by aquatic fauna which exceed reference concentrations on an ongoing basis.

- Transport of metal laden sediment into McArthur River proper and measureable increase in metal concentration in fauna at SW11.

- Reportable environmental incident.

- Adherence to Dust Management Plan including ongoing dust monitoring and contingency for increased management.

- Dust suppression through use of watercarts. - SW19 specific management including sediment traps adjacent to the haul road and creek batters to catch runoff. Periodic removal of sediment from sediment traps and ongoing maintenance.

- Erection of bund on downstream end of SW19 to capture water and sediment and thus carriage into McArthur River during operation.

- Mechanical excavation and removal of sediment from SW19.


- Annual monitoring of fauna tissues at SW19, reference and downstream locations to

B 2 12 (M) - Installation of Barney Creek Sump 2 (BCS2) will capture water prior to reaching the McArthur River in low to moderate flow events.

- Monthly monitoring of water quality and fluvial sediment to determine metal loads and setting criteria for additional management.

B 2 12 (M) - Historical evidence shows existing mitigation measures employed to supress dust and capture run-off has effectively reduced metal concentrations in fluvial sediments and subsequently fauna (Indo-Pacific Environmental 2016a).




ascertain effect on aquatic biota and determine whether metals are entering food chain.

Open Cut: Closure

4 Presence of exposed non-benign or acidic rock in pit and interaction with final void waterbody water.

- Continual influence on final void waterbody water quality with pH, electrical conductivity (EC) and/or metal concentrations of water beyond fauna tolerances.

- Effects on water quality within receiving waters downstream upon release.

- Adverse effect on aquatic habitat and fauna within and downstream of final void waterbody.

- Exceedance of SSTV’s at SW11 post mixing.

N/A - Rapid filling of final void waterbody via pumping to reduce interaction of oxygen and potentially reactive rock.

- Demonstration of acceptable water quality prior to removal of the downstream levee and connection to the McArthur River.

- Demonstration of acceptable water quality within the final void waterbody prior to removal of the upstream levee and creation of an inlet.

- Regular inflow of river water will dilute final void waterbody and counteract effects of evapoconcentration (KCB 2016).

- Adaptive management allows for potential water treatment methods (for example, reverse osmosis) to improve final void waterbody water quality.

- Routine ongoing monitoring to determine accuracy of predictive modelling.

- Routine ongoing monitoring to determine output water quality. Monitoring should continue until water quality is determined to be stable and acceptable for discharge.

- Contingency to isolate final void waterbody from McArthur River should water quality of the final void waterbody be determined to be causing detrimental and ongoing impact to the McArthur River.

C 2 8 (M) - Pit wall rock considered to have a lower reactivity due to absence of oxygen due to significant water coverage (KCB 2016).

- Modelling predicts limited mixing will occur with outflows largely reflecting river water contributions (inflow) for 20 years post-flooding (Caballero and Boland 2016).

- Modelling predicts that a moderate salinity, neutral pH and low metal (Zn, As and Pb) final void waterbody can be maintained (KCB 2016).

- Post-closure surface water modelling predicts elevated sulphate (up to 1087 mg/L) and zinc (up 0.159 mg/L) in water flowing from the final void waterbody to the McArthur River when connected via downstream levee opening (2060-2069). Output from the final void waterbody is predicted to occur for up to 47 days per year and during peak flow events associated with the wet season only. These waters will be subject to high dilution once mixed waters from the McArthur River. Annual average concentrations of sulphate and zinc are predicted to decrease over time with ongoing annual flows from the McArthur River (WRM 2016).

- Post-closure surface water modelling predicts SO4, Zn, Pb and As to remain below Site Specific Trigger Values at downstream compliance point (SW11) (WRM 2016).

- Connection to the McArthur River will not occur until water quality is determined to be stable and acceptable for discharge.

5 Placement of non-benign or acidic tailings into pit.

- Continual influence on final void waterbody water quality with pH, EC and/or metal concentrations of flood water beyond fauna tolerances.

- Final void waterbody water quality effects on receiving waters downstream upon release.


- Exceedance of SSTV’s post mixing.

N/A - Pumping of more concentrated water out of pit during tailings deposition to remove contaminant mass.

- Rapid filling of final void waterbody via pumping and demonstration of acceptable water quality prior to removal of the downstream levee and connection to the McArthur River.

- Demonstration of acceptable water quality within the final void waterbody prior to removal of the upstream levee and creation of an inlet.

- Limited connectivity to the McArthur River through up and downstream levee openings designed to facilitate inflow of river water for dilution.


- Adaptive management allows for water treatment methods to improve final void waterbody water quality.

- Routine ongoing monitoring to determine output

D 2 5 (L) - Significant water coverage will reduce reactivity of tailings due to absence of oxygen.

- Regular addition of river water will dilute final void waterbody and counteract effects of evapoconcentration (KCB 2016).

- Modelling predicts very limited mixing will occur with outflows largely reflecting river water contributions (inflow) for 20 years post-flooding (Caballero and Boland 2016).

- Modelling predicts that a moderate salinity, neutral pH and low metal (Zn, As and Pb) final void waterbody can be maintained (KCB 2016).

- Post-closure surface water modelling predicts elevated sulphate (up to 1087 mg/L) and zinc (up 0.159 mg/L) in water flowing from the final void waterbody to the McArthur River when connected via downstream levee opening (2060-2069). Output from the final void waterbody is predicted to occur for up to 47 days per year and during peak flow events associated with the wet season only. These waters will be subject to high




water quality. Monitoring should continue until water quality is determined to be stable and acceptable for discharge.

- Contingency to isolate final void waterbody from McArthur River should water quality of the final void waterbody be determined to be causing detrimental and ongoing impact to the McArthur River.

dilution once mixed with waters from the McArthur River. Annual average concentrations of sulphate and zinc are predicted to decrease over time with ongoing annual flows from the McArthur River (WRM 2016).


- Connection to the McArthur River will not occur until water quality is determined to be stable and acceptable for discharge.

6 Infilling of pit and fine sediments. - Small particulates lead to high TSS in final void waterbody.


N/A - Rapid filling of final void waterbody via pumping and extended period of settling prior to removal of the downstream levee and connection to the McArthur River.

- Connection via upstream levee will see annual inflow of sediment creating a benign layer above tailings.

D 2 5 (L) - Modelling predicts very limited vertical mixing will occur (Caballero and Boland 2016) leading to limited potential for re-suspension of fine particulates.

7 Flooding of final void waterbody and inflow.

- Reduced flow in the McArthur River. - Reduced period of river connectivity and species migration/recruitment to upstream pools.

- Reduce water level in the McArthur River to the extent flow ceases and/or is atypical of wet season magnitude.

- Reduction of downstream floodplain inundation which affects fish spawning and recruitment at a measureable level.

N/A - Initial rapid flooding by pumping from McArthur River during wet season and only when flows exceed 10 m3/s ensuring sufficient flow remains in McArthur River. Final void waterbody filled to approximately 14 m AHD.

- Initial connection to the McArthur River via downstream levee opening (2060-2069) when river stage height is greater than five metres above the channel invert to ensure sufficient flow remains in the McArthur River and average period of connectivity is not affected. Low flows will not enter the final void waterbody and will flow down the McArthur River.

- Ongoing connection via inlet designed to flood when river stage height is greater than five metres above the McArthur River channel invert to ensure sufficient flow remains in the McArthur River and average period of connectivity is not affected. Low flows will not enter the final void waterbody and flow down the McArthur River.

- Inlet height will result in pit flooding for a limited number of days per year.

D 2 5 (L) - Modelling predicts that final void waterbody flooding (2060-2069) through the downstream levee opening will only occur during wet seasons when flow rates exceed 10m3/s and for a limited duration, estimated to be 12 days per year. During this period annual net water loss to the final void waterbody from the McArthur River is predicted to be low, being an average of 2300 ML annually or 0.3% of the total flow measured upstream of the final void waterbody (SW21) (WRM 2016).

- Modelling predicts that final void waterbody flooding beyond 2070 and after connection through the upstream levee opening will occur during wet season flows for up to an average of 10 days per year. During the period beyond 2070 net water loss to the final void waterbody from the McArthur River is predicted to be low, being an average of 1700 ML annually or 0.2% of total the flow measured upstream of the final void waterbody (SW21) (WRM 2016).

8 Transport of sediment, particulates and detritus into final void waterbody.

- Influence on river morphology as a result of reduced sediment load.

- Reduced energy from allochthonous input resulting in food chain effects.

N/A - Engineering of inlet and outlet means connection to the McArthur River is limited and only occurs when stage height is greater than five metres above the channel invert.

D 2 5 (L) - Modelling predicts ~12% of the TSS from the McArthur River will flow into the final void waterbody (WRM 2016).

- An additional ~32% of the downstream TSS load (and assumedly the detrital load) is introduced into the McArthur River from creeks and rivers located below the final void waterbody and SW11.

- Net loss of TSS in waters downstream of the mine is ~8%.

9 Fauna entering pit during initial flooding and connection of downstream levee opening (2060-2069)

- Aquatic fauna mortality due to vertical fall whilst final void waterbody fills including listed threatened species.

N/A - Initial rapid flooding by pumping from McArthur River during wet season to 14 m AHD.

- Period of connectivity between McArthur River and final void waterbody is limited to when river stage height is greater than five metres above

C 1 5 (L) - Inlet design and limited duration of connectivity will restrict opportunity for larger fauna to enter final void waterbody.

- Barrages have been seen to be effective at impeding upstream movement of Pristis pristis




the channel invert. - Engineered solution to be used to restrict the entry of large fauna (e.g. Pristis pristis) moving upstream into final void waterbody during initial flooding e.g. vertical batters or gabions.

- Engineered solution to create ramped design (~1:30 slope) of inlet inside final void waterbody to slow flow and reduced vertical drop.

- Assessment of fauna entering final void waterbody to be undertaken to understand abundances and species. Adaptive management to allow for additional fauna exclusion measures to be considered if numbers of fish entering final void waterbody are shown to be high and detrimentally affecting McArthur River diversity or density.

(Thorburn et al. 2003, 2004, 2007). The construction of a steep vertical barrage will restrict larger species entering the final void waterbody.

- Sloped design of the final void waterbody side of the downstream levee inlet will reduce vertical relief (fall). Ramped design of ~1:30 slope has been demonstrated to be sufficient for the up and downstream movement of Pristis pristis (Kirby et al. 2009).

10 Fauna entering pit during annual flooding when connected to the McArthur River via the upstream and downstream levee openings (beyond 2070)

- Stranding of fauna in the final void waterbody leading to mortality including listed threatened species.

- Lack of suitable physical habitat to sustain aquatic fauna leading to mortality.

- Lack of functioning habitat to sustain aquatic food web including prey leading to mortality.

- Population level effect due to isolation from breeding population and mortality.

N/A - Period of connectivity between McArthur River and final void waterbody is limited by inlet and outlet design which reduces opportunity for fauna to enter.

- Engineered solution to restrict the entry of large fauna (e.g., P. pristis) at both upstream and downstream levee opening such as vertical barriers on ramps.

- Benching of final void waterbody edges to provide aquatic fauna habitat at various water levels.

- Rehabilitation and establishment of riparian vegetation to provide allochthonous input and physical habitat in the form of root mats. Riparian vegetation should be maintained until self-generating.

- Emplacement and stabilisation of extensive large woody debris and in-water structure on benches to provide habitat, allochthonous input, varied depth and flows.

- Assessment of fauna entering final void waterbody to be undertaken to understand abundances and species including effectiveness of fish ways.

B 2 12 (M) - Modelling predicts that final void waterbody flooding beyond 2070 and after connection through the upstream levee opening will occur during wet season flows for up to an average of 10 days per year. As such opportunity for fauna to enter the final void waterbody is low.

- Barrages have been seen to be effective at impeding upstream movement of Pristis pristis (Thorburn et al. 2003, 2004, 2007). The construction of a steep vertical barrage will restrict larger species entering the final void waterbody.

- Juvenile Pristis pristis have been shown to prefer shallow waters less than ten metres depth (Thorburn et al. 2003, Kyne et al. 2013). Furthermore, a vast majority of the species present in the McArthur River are considered to be non-pelagic and small bodied which have demonstrated preference for shallow water habitats (Horppila et al. 2000, Pusey and Arthington 2003, Storey and Creagh 2014). The vast majority of the final void waterbody is considered to be unsuitable for sustaining the majority of aquatic fauna species present due to the fact a large proportion of the final void waterbody will be open deep waters. If aquatic fauna enter the final void waterbody edge habitat is the likely area of occupancy.

- Studies conducted by Indo-Pacific Environmental on the McArthur River diversion since 2008 indicate the effectiveness in woody debris at providing fish habitat. Prior to the addition of woody debris in the McArthur River diversion the aquatic fauna was highly depauperate. Installation of complex woody debris habitat in recent years has resulted in a diversion fauna consistent with that of naturally vegetated sections of the McArthur River (see Indo-Pacific Environmental 2016b)

- Bony fish species present in the McArthur River, which may enter the final void waterbody, are regionally common (and generally in high




abundance). As such final void waterbody mortality is unlikely to have a population level effect.

- Crocodylus are known to undergo long-range overland travel in response to periodic drying such as that experienced in monsoonal Australia (Lang 1987). As such, Crocodylus spp. individuals would likely to retreat to the McArthur River if conditions are unfavourable.

11 Introduction of site waters to final void waterbody including captured surface water from Barney Creek sumps

- Adverse effect on final void waterbody water quality including elevation in metal content, pH and EC.



- Exceedance of SSTV’s at SW11 post mixing

N/A - Inlet design allows river water to enter the final void waterbody annually facilitating dilution (KCB 2016).

- Ongoing monitoring of site waters introduced to the final void waterbody with contingency for treatment to improve water quality prior to release. Dewatering to final void waterbody will cease if introduced waters are seen to have a measurable effect on final void waterbody water quality.

- Adaptive management allows for water treatment methods (for example reverse osmosis) to improve final void waterbody water quality. Also allows for the treatment of Barney Creek sump waters prior to discharge into the final void waterbody.

- Routine ongoing monitoring to determine accuracy of predictive modelling.

- Routine ongoing monitoring to determine output water quality with contingency to isolate final void waterbody from McArthur River.


D 2 5 (L) - Volume of final void waterbody vastly greater than likely volumes introduced from site sources. Large buffering and dilution capacity of final void waterbody.

- Post-closure surface water modelling predicts elevated sulphate (up to 1087 mg/L) and zinc (up 0.159 mg/L) in water flowing from the final void waterbody to the McArthur River when connected via downstream levee opening (2060-2069). Output from the final void waterbody is predicted to occur for up to 47 days per year and during peak flow events associated with the wet season only. These waters will be subject to high dilution once mixed waters from the McArthur River. Annual average concentrations of sulphate and zinc are predicted to decrease over time with ongoing annual flows from the McArthur River (WRM 2016).


12 Vertical mixing results in inundated tailings mixing with surface waters.

- Adverse effect on final void waterbody water quality.

- Effects on water quality in receiving waters downstream upon release.

- Adverse effect on aquatic habitat and fauna within and downstream of final void waterbody

N/A - Connection via upstream levee will see annual inflow of sediment creating a benign layer above tailings.

- Contaminated materials will not be placed in final void waterbody after flooding.

D 2 5 (L) - Modelling predicts very limited vertical mixing will occur below 50m depth (Caballero and Boland 2016).

13 Management of final void waterbody water quality beyond 2070.

- Insufficient monitoring, management and treatment leads to reduction in water quality.


- Adverse ongoing effect on aquatic habitat and fauna within and downstream of final void waterbody through effects of elevated metals.


N/A - Ongoing frequent monitoring of final void waterbody water quality and fauna to 3018. Frequency of monitoring should be determined from stability of water quality and performance against SSTV’s.


- Adaptive management will allow for capability to run water treatment plant as and when required to manage discharge water quality.

- Design of levee openings ensures outflow during high flow events on with subsequent high dilution rates.

- Contingency to isolate final void waterbody from McArthur River should water quality of the final void waterbody be determined to be causing

D 3 9 (M) - Post-closure surface water modelling predicts elevated sulphate (up to 1087 mg/L) and zinc (up 0.159 mg/L) in water flowing from the final void waterbody to the McArthur River when connected via downstream levee opening (2060-2069). Several common fish species including Hephaestus fuliginosus, Leiopotherapon unicolor, Melanotaenia splendida, Nematalosa erebi and Lates calcarifer have been recorded in waters of the McArthur River up to ~2240 mg/L.

- Annual average concentrations of sulphate and zinc are predicted to decrease over time with ongoing annual flows from the McArthur River.

- Active caretaking and adaptive management will give high confidence that final void waterbody water quality is maintained and SSTV’s at SW11 are adhered to.




detrimental and ongoing impact to the McArthur River.

14 Uncontrolled discharge of water from the final void waterbody during large flood years

- Extended period of unrestricted/uncontrolled water form final void waterbody outlet.

- Adverse effect on downstream water quality, habitat and fauna from elevated metal concentrations.

N/A - Levee built to 1:500 year flood protection level. - Frequent ongoing monitoring of final void waterbody water quality.

- Adaptive management will allow for capability to run water treatment plant as and when required to manage discharge water quality.


C 1 4 (L) - Modelling predicts limited mixing will occur with outflows largely reflecting river water contributions (inflow) (Caballero and Boland 2016).

- Modelling predicts that connectivity between the final void waterbody and McArthur River occurs for a low number of days per year.

- Low likelihood of overtopping due to construction of bund height and likely frequency of very large flood events.

15 Erosion and Failure of final void waterbody levee, inlet and outlet.

- Uncontrolled discharge of final void waterbody water.

- Potential effect on water quality adjacent McArthur River and downstream.

- Reduction in river water quality and adverse effects on fauna and habitat.

N/A - Final void waterbody levees constructed in accordance with relevant Australian National Committee on Large Dams (ANCOLD, 2003).

- Levee seismic design criteria include building to 1:1000 AEP Max Design Earthquake (MDE) and 1:500 AEP Operating Basis Earthquake (OBE) criteria.

- Ramp designed to flood to 1:100000 Annual Exceedance Probability (AEP) (Critical Storm Duration).

- Frequent and ongoing bund integrity and stability checks.

- Active and ongoing caretaking of site includes maintenance and repair schedule.

- Contingency planning and budget allowances to rebuild damaged sections in the event of levee or bund failure, as required in the later dry seasons.

D 2 5 (L) - Due to the construction standards, ongoing maintenance and repair contingency, levee failure would not be expected to be significant.

- Failure of the final void waterbody levee is most likely to occur during very large wet seasons. Significant dilution would likely occur between escaped final void waterbody waters and the McArthur River which would be in high flow.

16 Permeability of final void waterbody banks, walls and levees

- Head pressure from flooded final void waterbody causes water outflow (uncontrolled release).

- Adverse effect on surface water and groundwater.

- Reduction in river water quality and adverse effects on fauna and habitat.

N/A - Permeability testing undertaken to determine likelihood of final void waterbody water outflow as required.

- Frequent and ongoing monitoring of bund integrity.

- Installation of groundwater monitoring bores installed between final void waterbody and McArthur River.

- Development of conceptual plans for mitigation measures that can be detailed further if monitoring indicates remediation is necessary.

C 2 8 (M) - Post closure modelling predicted final void waterbody outflows to be variable and not significant in comparison to the outflows through the engineered levee system (KCB 2016).

- Post closure modelling predicts annual groundwater inflow in the final void waterbody to be far greater than outflow from the years 2047 to 3018 (i.e. 533 cf. 28 ML/year, respectively) (WRM 2016).

- Post closure modelling indicates reduction in sulphate and zinc concentrations over time (WRM 2016). Modelling was based on fully mixed water column.

North Overburden Emplacement Facility (NOEF)

17 Expansion of NOEF footprint - Encroachment on Emu Creek catchment and reduction in available habitat and flow.

- Effect on seasonally available habitat. - Effects on reproduction and dispersal of highly mobile aquatic fauna.

- Reduction in available habitat for listed threatened species.

- NOEF runoff entering Emu Creek resulting in decline in water quality.


N/A - Current NOEF footprint has been minimised avoiding extensive expansion to the north and encroachment on Emu Creek.

- Drain installed on the northern side of the NOEF where encroachment occurs.

- Monitoring of Emu Creek and McArthur River water quality.

- Adherence to SW11 SSTV’s.

E 2 3 (L) - The northern side of the NOEF encroaches on a small unnamed tributary of Emu Creek. The installation of a runoff drain will reduce the potential flow of water coming off (or from) the NOEF and flowing into Emu Creek thus reducing potential downstream effects.

- The area of encroachment is small. A survey of Emu Creek fauna was conducted in 2015 (Appendix 1 of this document) which showed the creek was highly ephemeral and rapidly dried after the cessation of rain. As such this was not considered to represent critical habitat for any




species of aquatic fauna. - Appendix 1 indicates the species recorded during the survey. These species are all widely distributed in the McArthur River catchment. As such Emu Creek was not considered to be critical habitat and loss of a small portion of the catchment will not lead to a population level effect.

- Pristis pristis was not been captured in the survey of Emu Creek fauna (Appendix 1). Emu Creek is not considered to represent suitable habitat for the species due to its temporary nature and lack of favourable habitat for the species (Thorburn et al. 2003). As such the likelihood of occurrence is considered to be very low.

18 Inappropriate storage and disposal of waste rock leads to contamination of surface water and groundwater systems

- Contamination of surface water and groundwater systems through exposure to metalliferous or high acidity contaminants or outflow of contaminated waters.

- Extensive and long-term effects on downstream water quality (adjacent Creeks and McArthur River) and exceedance of SSTV’s.

- Influence on water pH and thus metal bioavailability and toxicity.

- Extensive adverse lethal and sub-lethal effects on aquatic fauna including listed threatened species.

- Extensive adverse effects on aquatic habitat quality.

- NOEF design includes encapsulation of high risk materials to limit oxidation and seepage of oxidation products into groundwater and surface water systems.

- NOEF performance objectives include physical stability of structure.

C 4 18 (H) - NOEF performance objectives include chemical stability through material placement and compaction techniques, cover system designs, seepage collection and treatment structures.

- In-pit grade control of all overburden at the blast block level is undertaken to validate classification prior to load and haul operations.

- The geochemistry of benign rock used as covers on OEFs is monitored monthly to ensure correct waste placement.

- Ongoing periodic monitoring of NOEF stability and maintenance.

- Ongoing frequent monitoring of groundwater and surface water in proximity to the NOEF and downstream. This should include fate and transport studies to determine pathways and rates of transport of contaminants of concern.

- Adaptive management allows for contingency planning and remediation if unacceptable impacts on the receiving environment are predicted or measured.

D 4 14 (M) - The internal architecture of the NOEF places the materials with the highest risk of creating environmental harm furthest away from the receiving environment, with progressively lower risk materials placed toward the final outer surface.

- A Statement of Reasons drafted by the NTEPA (2014) outlines the justification for the Project progressing to an EIS. That document states that the DME suggested some material in the base layer was considered to be non-benign. Despite the proposed encapsulation some interaction of non-benign material and groundwater may still occur.

- MRM waste classification system sees various classifications of waste handled and stored under conditions specific to the classification.

- Seepage collection and treatment structures aim to reduce volumes of water entering groundwater or surface water systems.

- Design will limit the seepage of water through NOEF to reduce destabilising effects and cartage of contaminants

19 Surface water runoff - Erosion and subsequent carriage of sediment due to inadequate armouring.

- Instability of NOEF structure. - Potential flow of contaminants into adjacent creeks resulting in elevated pollutant loads and TSS.

- Potential flow of sediment into adjacent Creeks resulting in elevated TSS and subsequent reduction in light attenuation and aquatic habitat quality.

- Potential effect on downstream water quality and exceedance of SSTV’s.

- Direct effects on aquatic fauna in adjacent Creeks including metal toxicity. Elevated TSS may result in reduced hunting efficiency due to reduced visual acuity and mortality due to clogging of gills with fine


- NOEF performance objectives include physical stability of structure.

- Design of the NOEF (including armouring, slopes compaction and permeability) focus on controlling erosion and sediment loss due to surface runoff. This includes stilling basins to dissipate energy from high flows generated as runoff is directed down steep embankments (see O’Kane 2016a).

- Installation of numerous drainage channels, sumps and lined (clay or geopolymer) dams (referred to as PRODS) to capture runoff. Runoff dams capacities set to have a less than

D 3 9 (M) - TSS in runoff is expected to be elevated for some time following placement of the cover system (O’Kane 2016a). Surface water at this time will subsequently be directed into sediment dams to remove sediment by gravity separation.

- Ongoing monitoring of surface water runoff. Monitoring and maintenance of surface water management systems as required.

- Ongoing monitoring of runoff water quality and surface waters in adjacent Creeks and McArthur River.

- Installation of sumps in Barney Creek (mainly BCS2) will ultimately capture surface water runoff which has entered Barney Creek.

- Compliance with SSTV’s at SW11 and surface water quality standards.

D 2 5 (L) - During construction some water will interact with reactive material. This water will be diverted into PRODS. Once the NOEF is completed and covered with an outer layer of benign materials surface runoff is likely to contain low concentrations of contaminants.

- Based on a NOEF design which effectively captures and manages surface water runoff modelling predicts a negligible contribution of the NOEF to contaminant levels in Surprise and Barney Creeks.

- Barney Creek sumps will capture runoff during low flow periods and limit its entry into the McArthur River.

- Large runoff events are associated with wet season rains. Runoff will coincide with high flow events in adjacent Creeks and the McArthur




particulates. 5% probability of exceedance (spill) over the operating life of the dam.

- During NOEF construction exposed areas of reactive rock will generate contaminated surface runoff. This runoff will be diverted into water management dams (PRODS).

- NOEF design includes outer layers with low risk materials. As such post-construction runoff is expected to be below SSTV’s.

River which will significantly dilute any pollutant or particulate concentration reducing the risk to aquatic fauna.

- Post closure NOEF design is based on a moisture store-and-release’ and ‘barrier’ concept which will capture rainwater then progressively dry through evaporation (O’Kane 2016b).

- Extensive surveys of the aquatic fauna of the McArthur River, including during high flow events, indicated that the aquatic fauna present has tolerance of turbid waters. Considering that the duration of a large runoff event is likely to be short it is likely aquatic fauna will persist during limited duration high TSS events.

20 Seepage from NOEF including PAF material giving rise to acid and metalliferous drainage

- NOEF creates groundwater mound affecting flow regime in adjacent Creeks.

- Seepage results in contaminant transfer in groundwater with adverse effects on groundwater and surface water quality.

- Seepage of metals, sulphates and/or acids can result in direct toxicity to aquatic fauna including listed threatened species.

- Adverse impacts on aquatic habitat in adjacent Creeks and downstream including the McArthur River.

- Loss of Barney Creek and McArthur River habitat.

- Non-compliance with SW11 SSTV’s.


- NOEF design aims to manage key risks including generation of acid by encapsulating high risk materials and reducing exposure to oxygen.

C 4 18 (H) - The NOEF is designed to limit seepage through basal foundation preparation, construction methodologies (including alluvial barriers) and the final cover system (see O’Kane 2016b).

- Seepage mitigation systems as required to meet MRM’s objective. These may include interceptor drains and recovery bores.

- Ongoing monitoring of groundwater bores surrounding the NOEF.

- Ongoing monitoring of surface water in Barney Creek and downstream.

- Installation of sumps in Barney Creek (mainly BCS2) will ultimately capture seepage which had entered Barney Creek.

D 3 9 (M) - There is significant buffering capacity in the waste rock. As such it is not expected to produce large amounts of acidic mine drainage.

- Modelling predicts neutral pH waters will occur in Barney Creek (KCB 2016).

- Post closure outer layer NOEF design is based on a moisture store-and-release’ and ‘barrier’ concept which will capture rainwater then progressively dry through evaporation. A dense low permeability clay layer will reduce percolation through the NOEF (O’Kane 2016b).

- After rehabilitation of the TSF, seepage from and as a result of the NOEF results in high sulphate (and zinc) concentrations being present in Barney Creek (WRM 2016). This is the main water quality related issues post TSF rehabilitation. Barney Creek sumps will effectively capture runoff during low flow periods and prevent its entry into the McArthur River.

- Modelling predicts that post closure (and after TSF rehabilitation) monthly median sulphate concentrations within Barney Creek will exceed the SW11 SSTV’s between January and August 2101-2500 (WRM unpublished). Maximum concentrations are recorded when creek discharge is at its lowest.

- Modelling predicts that monthly median sulphate concentrations will only exceed the SSTV’s in Barney Creek during months of lowest discharge in years 2501-3018 (i.e. May to July) (WRM unpublished).

- Pristis pristis has not been captured in Barney Creek during targeted surveying conduced since 2006. Furthermore, Barney Creek does not represent favourable habitat for the species which prefers main channel riverine waters (Thorburn et al. 2003). As such the likelihood of occurrence is considered to be very low.

- Barney Creek is ephemeral and typically dries out annually. Barney Creek is not considered to be critical habitat for any species in the McArthur River catchment. In the event Barney Creek habitat become unsuitable for sustaining aquatic fauna this is unlikely to have a population level




effect on any species. - Capture of seepage in the Barney Creek will prevent waters entering the main channel McArthur River. During peak flow periods water entering the McArthur River from Barney Creek will be highly diluted.

21 Surface runoff dams overflow and seepage

- Failure of levee resulting in uncontrolled spill

- Overflow of dams during high runoff periods and uncontrolled release into adjacent Barney Creek.

- Seepage through levee. - Contamination of surface water and groundwater systems with dam waters containing high metal or sulphate content or of low pH.

- Adverse effects on Barney Creek habitat and aquatic fauna and downstream.

- Long term effect from groundwater impact including the McArthur River

- Runoff dams system set to have a less than 5% probability of exceedance (spill) over the operating life of the dam.

C 2 8 (M) - New runoff dams constructed in accordance with relevant Australian National Committee on Large Dams (ANCOLD) Guidelines including ANCOLD’s Guidelines on Tailings Dam Planning, Design, Construction, Operation and Closure (ANCOLD, 2012). Designed earthquake loading of 1:1,000AEP Max Design Earthquake (MDE) and 1:500 AEP Operating Basis Earthquake (OBE). Crest of spillway above 100 year McArthur River flood level. Spillway design to safely pass a 1:2000 AEP flood event with a 1:10 AEP wind event wave allowance.

- Runoff dams lined with low permeability materials to limit seepage.

- Ongoing biannual monitoring of stability, structure, operation and management during their operational phases.

- Ongoing monitoring of dam liner integrity.

D 2 5 (L) - Based on the design capacities, spill will occur on very large runoff events with a majority of the spill likely to be rainwater. These will coincide with high flow events in adjacent Barney Creek and the McArthur River. As such any spill entering creeks will be highly diluted.

- Post-closure runoff dams aim to collect NOEF runoff and due to the low toxicity nature of the outer layer runoff is expected to be benign.

- Design criteria, build standards and routine monitoring for the life of the dam means the likelihood of failure of a levee would be low.

- Appropriate dam lining and seepage monitoring. - Conceptual seepage recovery systems could be installed as a mitigation measure as required to limit seepage into Barney Creek.

- Seepage entering Barney Creek will be captured by BCS2 preventing introduction to the McArthur River.

Tailings Storage Facility (TSF)

22 Increased holding capacity creates groundwater mound.

- Increased mass of tailings raises groundwater level/expression leading to altered flow regime of adjacent ephemeral creeks.

- Increased release of earth laden and mine derived sulphates leading to increase in water electrical conductivity in adjacent ephemeral creeks.

- Adverse effect on Surprise Creek aquatic habitat quality through increase in EC.

- Alteration of natural flow and drying regimes via alteration of groundwater level.

- Adverse effect on fauna distribution and dispersal through exceedance of fauna tolerance.

- Tailings management includes limiting ponding of water on the TSF, improving barrier systems to seepage and groundwater recovery (GHD 2016).

A 2 16 (M) - Ongoing groundwater and surface water monitoring over operational phases which is continued well after rehabilitation of TSF.

- End of mine reprocessing of tailings will see complete removal of tailings reducing long term impact and limit risk period.

- Rehabilitation and decommissioning of the TSF will see mining landscape left safe and secure for humans and animals in long term (i.e. 100-1000 years) (GHD 2016). Extensive closure objectives are outlined in Section 2.4 of GHD (2016) with environmental values and ecosystems maintained.

- Post-closure monitoring undertaken in accordance with GHD (2016).

B 2 12 (M) - Groundwater monitoring has indicated that ponding of water on TSF has resulted in a water table mound which has interrupted natural groundwater flow and caused prolonged discharge in Surprise Creek. Recent (2015) improvements in TSF surface water management including removal of large water volumes has led to improvements. Sections of Surprise Creek which atypically held water in the late dry season were observed to have dried by October 2016 which was historically the case.

- Despite improved management of the TSF to reduce mass, the expansion will lead to significantly larger volumes being stored. As such mounding is still likely to occur.

23 Failure of TSF embankment. - Uncontrolled release of tailings. - Contamination of Surprise Creek and downstream ecosystems.

- Adverse effect on aquatic fauna and habitat.

N/A - TSF constructed in accordance with relevant Australian National Committee on Large Dams (ANCOLD) Guidelines including ANCOLD’s Guidelines on Tailings Dam Planning, Design, Construction, Operation and Closure (ANCOLD, 2012).

- TSF seismic design criteria include building to 1:1000 AEP Max Design Earthquake (MDE) and 1:500 AEP Operating Basis Earthquake (OBE) criteria.

- TSF spillway design flood to 1:100000 AEP (Critical Storm Duration).

- Adherence to Critical Operating Parameters (COP’s) (GHD 2016).

D 2 5 (L) - Based on the standard of construction, ongoing inspection and failure controls it is expected that any failure in the TSF embankment would be over a limited area and rapidly repaired.




- Tailings characterisation undertaken to understand mass.

- Ongoing bi-annual monitoring of stability, structure, operation and management (GHD 2016).

- Adherence to Dam Safety Emergency Plan (DSEP).

24 Seepage from TSF influences on-lease groundwater and surface waters

- Contamination of groundwater and surface water including increased metal and sulphate concentrations above SSTV’s in water of Barney and Surprise Creeks.

- Adverse effects on aquatic habitat and fauna through exceedance of fauna tolerances.

- Loss of Surprise and Barney Creek habitats.

- Tailings management includes limiting ponding of water on the TSF, improving barrier systems to seepage and groundwater recovery (GHD 2016). Furthermore, tailings densities will be maximised to reduce permeability of the tailings and thus seepage.

A 2 16 (M) - Ongoing bi-annual monitoring of stability, structure, operation and management (GHD 2016).

- Installation of sumps on Barney Creek to capture surface water reducing risk of tailings.

- End of mine reprocessing of tailings and site rehabilitation will reduce long term impact and limit risk period to 2100.

- Ongoing monitoring of groundwater and surface water to determine seepage rates and quality.

A 2 16 (M) - Seepage has historically been a significant issue due to the past extent of water storage on the TSF and the visible expression of seepage to the surface (GHD 2016). Recent (2015) improvements in TSF surface water management including removal of large water volumes has led to improvements. Sections of Surprise Creek which atypically held water in the late dry season were observed to have dried by October 2016 which was historically the case.

- During the operational period modelling predicts that Barney Creek Sump 1 (BCS1), located at the confluence of Barney and Surprise Creeks, will collect up to ~40 ML/yr with a majority being identified as seepage from the TSF (WRM 2016).

- Modelling predicts median sulphate concentrations will exceed the SW11 SSTV for sulphate downstream of the TSF (SW24) during the operational period (2018-2047) (peaking in months of lowest flow). After cessation of mining, reprocessing of tailings and rehabilitation of the TSF sulphate concentrations are predicted to decrease in Surprise Creek. However, median sulphate concentrations are predicted to: exceed the SSTV for the post closure period 2048-2060 when water is flowing (i.e. December to August); exceed the SSTV for the post closure period 2061-2100 between February and August as flows subside; and exceed the SSTV for the post closure period beyond 2100 during the months of lowest flow.

- Pristis pristis has not been captured in Surprise or Barney Creeks during targeted surveying conduced since 2006. Furthermore, Surprise and Barney Creeks do not represent favourable habitat for the species which has been recorded as preferring main channel riverine waters (Thorburn et al. 2003). As such the likelihood of occurrence is considered to be very low.

- The bony fish Hephaestus fuliginosus, Leiopotherapon unicolor, Melanotaenia splendida and Nematalosa erebi have been consistently recorded in sulphate affected reaches of Barney Creek up to 2240 mg/L. Furthermore, Lates calcarifer has been recorded from inland waters with sulphate concentrations up 2180 mg/L. Based on these known tolerances it is likely that some species will persist in Surprise and Barney Creeks when sulphate concentrations are high.




- Surprise and Barney Creeks are ephemeral creeks which traditionally dry out annually. These creeks are not considered to be critical habitat for any species in the McArthur River catchment. In the event Surprise and Barney Creek habitats become unsuitable for sustaining aquatic fauna this is unlikely to have a population level effect on any species.

- The installation and operation of BCS1 and BCS2 will capture sulphate affected water. This will restrict flow of sulphate affected waters into the main channel McArthur River waters. During high flow periods any flow from Barney Creek into the McArthur River will be highly diluted.

25 Seepage from TSF influences off-lease surface waters

- Seepage leads to surface flow in adjacent creeks with subsequent inflow into McArthur River

- Increased metal and sulphate concentrations above SSTV’s at SW11.

- Adverse effects on McArthur River aquatic habitat and fauna through exceedance of fauna tolerances including listed threatened species.

- Tailings management includes limiting ponding of water on the TSF, improving barrier systems to seepage and groundwater recovery (GHD 2016). Furthermore, tailings densities will be maximised to reduce permeability of the tailings and thus seepage.

- Adherence to SW11 SSTV’s.

D 1 2 (L) - Ongoing bi-annual monitoring of stability, structure, operation and management (GHD 2016).

- Installation of sumps on Barney Creek to capture surface water reducing risk of tailings reaching McArthur River.

- End of mine reprocessing of tailings and site rehabilitation will reduce long term impact and limit risk period to 2100.

- Ongoing monitoring of surface water at SW11.

E 1 1 (L) - Surprise and Barney Creeks are ephemeral creeks which traditionally dry out annually.

- The installation and operation of BCS1 and BCS2 will capture sulphate affected water. This will restrict flow of sulphate affected waters into the main channel McArthur River waters. During high flow periods any flow from Barney Creek into the McArthur River will be highly diluted.

26 Water overtopping embankments during large rain events.

- Uncontrolled discharge of tailings. - Entry of tailings into Little Barney Creek. - Adverse on effects on downstream water quality and aquatic habitat.

N/A - TSF constructed in accordance with relevant Australian National Committee on Large Dams (ANCOLD) Guidelines including ANCOLD’s Guidelines on Tailings Dam Planning, Design, Construction, Operation and Closure (ANCOLD, 2012).

- Adherence to ANCOLD (2012) Extreme Storm Storage and Wet Season Storage Allowance criteria.

- Design includes a Process Water Dam (PWD). In the event rainfall leads to a spill, water from the TSF will spill into the PWD.

D 2 5 (L) - The frequency of rainfall or storm events large enough to result in a spill from the TSF (and subsequently the PWD) is considered to be low.

- If the event is large enough to cause a spill from the PWD water will enter Little Barney Creek. Any release would, however, coincide with local flooding of the Creek meaning dilution of tailings would be high (GHD 2016).


KEY RISKS, MANAGEMENT AND MONITORING 5.0

Primary Environmental Targets 5.1

Table 7 identified specific mitigation and management actions to reduce the potential impact of

the Project. While most relate to the management of water quality overarching environmental

targets should be set in relation to the aquatic fauna present. This is due to the fact MRM has

had, and will continue to have, influence on the McArthur River through its physical presence

(through its proximity to the McArthur River and tributaries) and mining processes.

Furthermore, considering the projected life of the mine and the proposed closure scenario,

which includes infrastructure that will become permanent fixtures of the landscape (including

the NOEF and final void waterbody), long term and ongoing targets need to be set to ensure

environmental values of the area are maintained.

The aquatic fauna of the McArthur River has been extensively studied and monitored in the

past decade to identify what effects MRM has had on the aquatic environment and to

determine ways to mitigate or rehabilitate impacted aspects. Consistent with current objectives

relating to aquatic fauna, all future MRM operations should be conducted to meet the following

objectives:

MRM activity will result in no reduction in species diversity in the McArthur River;

MRM activity will result in no measurable change in species abundance outside of

natural variation within the McArthur River;

MRM activity will not decrease river connectivity or migration pathways (including that

of P. pristis) in the vicinity of the mine or downstream through the creation of physical,

thermal or chemical barriers;

MRM activity will not reduce the overall health or function of aquatic fauna or habitat

and will ensure natural tissue metal concentrations in fauna and trophic flows are

maintained; and

MRM will not affect the amenity value of the aquatic fauna resource.

Documentation prepared for the MRM Phase 2 and Phase 3 expansions outlined a number of

environmental monitoring activities aimed at assessing these aforementioned objectives. While

a number of the aquatic fauna monitoring programs have greatly expanded in years since

these previous works, the aquatic fauna monitoring programs currently in place at MRM should

continue in order to collect information necessary in identifying whether the objectives are

being met into the future. This should continue throughout the operational mining phase and

post closure until such a point that aquatic habitat and fauna are determined to remain


unchanged and that MRM and activities pose no threat of detrimental or ongoing impact to the

McArthur River. Mitigation and management strategies outlined below subsequently build on to

the existing programs.

Risk identification and Mitigation 5.2

Major project risks were identified in Section 4.0 and in particular Table 7. The following section

summarises these risks into broad categories and provides an expanded description and

explanation of the mitigation, management and monitoring applied to reduce these risks. In

addition Appendix 2 provides discussion of potential implications for P. pristis in association

with the final void waterbody closure scenario.

Domain 1 - Open Cut: Operation 5.3

Reduction in Water Quality 5.3.1

Runoff and direct discharge of waters into Barney Creek, Surprise Creek and the McArthur

River has the potential to decrease water quality in the immediate vicinity of the discharge or

spill and influence downstream conditions. Discharged and spill waters derived from the Open

Cut operation can include accumulated rainwater occurring within the pit and levee walls,

process waters from mining operations and runoff from infrastructure (including roads and

embankments). In relation to the operation at MRM, these waters have been known to carry

various metalliferous contaminants (in particular lead, zinc, cadmium and arsenic), sulphate

and particulates which affect the total suspended solid (TSS) loads of receiving waters. An

example of the effects of runoff can be seen from the haul road bridge (SW19) where the input

of sediment contaminated with lead led to increases in bed sediment metals which were

subsequently absorbed by fauna (see Section 3.4.4 for expanded discussion).

Throughout the life of the project the effects of runoff and discharge waters should be mitigated

and managed in the following ways:

Implementation and frequent review of site specific management plans which outline

water testing and discharge protocols;

Adherence to Waste Discharge Licences which outline specific water quality targets for

both the discharge and at the downstream compliance point at SW11. These

conditions should be frequently reviewed and site specific trigger values (SSTV’s)

adjusted throughout the operational and post-operational periods;

Determination that waters are of ‘low risk’ and are not considered to be ‘complex

solutions’ prior to discharge;


Discharge of waters during high flow periods only to ensure sufficient dilution of

potential contaminants;

A new water treatment plant will operate from mid-2017 to treat poorer quality mine

affected water. Process will include coarse filtration, oxidation and precipitate filtration,

reverse osmosis and pH correction (WRM 2016);

Adherence to dust management plans including suppression through the use of water

carts on the haul roads to reduce metal contaminated dust entering creeks in close

proximity to hauls roads or major work areas;

Frequent review of roadways and drainage lines to identify potential flow pathways;

Installation and frequent maintenance of sediment traps such as haul road low points

including at SW19;

Installation of sumps along Barney Creek to capture water during moderate and low

flow events and prevent flow into the McArthur River; and

Annual remediation of SW19 bunding and mechanical excavation of sediments from

SW19.

Throughout the life of the Project the effectiveness of these mitigation and management actions

should be determined through monitoring including:

Monthly surface water monitoring and reporting of Barney and Surprise Creeks and the

McArthur River. Analysis will include a suite of metals (Al, As, Cd, Cu, Fe, Pb, Mn, Hg,

Ni and Zn), electrical conductivity (EC) and sulphate as a minimum during the

operational phase. Analysis of pH should also be undertaken to determine whether

changes are occurring as pH can greatly affect bioavailability of metals. Significant

changes and exceedances at compliance point should result in immediate cessation of

all discharge and investigation of point source and spill waters. Post closure the

frequency of surface water monitoring may be reviewed and reduced if concentrations

of contaminants associated with the mining process are shown to be stable or

declining;

Annual collection and analysis of fluvial sediments from lower sections of Barney Creek

and SW11 to determine metal concentrations and inputs from Barney Creek during

operation. This sampling should continue post closure until such point that sediment

concentrations are seen to stabilise or decrease and are equivalent to reference

concentrations; and

Monitoring of fauna tissues (including SW19 and SW11) to ascertain effects on aquatic

biota should be conducted. Monitoring frequency should be based on an adaptive

program with sample collection conducted when surface water and fluvial sediment

concentrations of analytes of concern are considered to be high.


Drawdown 5.3.2

Inflow of groundwater into the MRM pit is predicted to lead to drawdown of Barney and

Surprise Creeks and the McArthur River. While the ephemeral nature of Barney and Surprise

Creeks means that drawdown effects on fauna would be low, several late dry season refuge

pools exist in the McArthur River adjacent the mine and immediately upstream, for example,

Djirrinmini Waterhole. These dry season refugia have been observed to sustain numerous

species throughout the dry season including P. pristis which is afforded protection under the

EPBC Act. Modelling predicts drawdown to be approximately 0.7 m in Djirrinmini Waterhole

(KCB 2016a). Considering a majority of Djirrinmini Waterhole would have water depths of less

than two metres in the late dry season, water drawdown of 0.7 m has the potential to have a

large effect on available habitat for listed threatened species.

Throughout the life of the project the effects of drawdown will be mitigated and managed in the

following ways:

In the long-term (post closure) drawdown is predicted to be negligible following flooding

of the final void waterbody. Recovery of water levels in Djirrinmini Waterhole are

predicted to recover within ten years post-mining;

Supplementary flow may be required to permanent refuge pools adjacent to the Project

in the event that drying of the river channel adjacent the pit is atypical of seasonal

variation; and

If large listed aquatic fauna are found to be trapped in dry season refugia affected by

drawdown consideration should be given to their translocation to larger pools in the

McArthur River.

Throughout the life of the project the effectiveness of these mitigation and management actions


Water levels should be monitored to assess whether modelled drawdown is accurate

throughout the operational phase and until the final void waterbody is flooded. Review

of mitigation and management strategies should be undertaken if drawdown is found to

be greater than predicted;

A physical assessment of available refugia should be undertaken in nearby sections of

the McArthur River (including Djirrinmini Waterhole) to assess available habitat

(refugia) in the late dry season prior to deepening of the pit to provide a basis for

comparison and to identify key refugia; and

Aquatic fauna monitoring should occur to assess whether the potential loss of fauna in

refuge pools as a result of drawdown deviates from predictions made in this


assessment. Review of mitigation and management strategies should be undertaken if

influence of drawdown is found to be greater than predicted.

Domain 1 - Open Cut: Closure 5.4

Fauna Stranding in the Final Void Waterbody 5.4.1

According to the current closure scenario, the final void waterbody will become a permanent

major feature of the McArthur River catchment. The proposed design will see annual

connection to the McArthur River and as such opportunity exists for fauna to enter the final void

waterbody. While some opportunity also exists for fauna to exit the final void waterbody, poor

water quality and lack of aquatic fauna habitat are major threats to the persistence of any

stranded fauna.

Water quality will be influenced by a number of factors including: the presence of non-benign or

acidic rock being present on the walls of the pit; placement of non-benign or acidic tailings in

the pit during decommissioning of the TSF; discharge of TSF waters into the final void

waterbody during decommissioning of the TSF; release of site waters including that from the

Barney Creek sumps which includes seepage from the NOEF; and groundwater intrusion. In

addition, considering the depth and surface area of the final void waterbody dissolved oxygen

levels are expected to be low and limited by depth.

A vast majority of the aquatic fauna species present in the McArthur River are widely

distributed throughout the greater Gulf of Carpentaria region. As such, mortality of individuals

stranded in the final void waterbody is unlikely to have a population level effect for most

species. However, potential entrapment (or death) of even low numbers of P. pristis which

occurs in naturally low abundance could have a population level effect. This is due to the fact

that the species occurs in naturally low abundance (Department of Environment 2015) (see

Section 3.4.6 for an indication of capture rates), has a low reproduction rate (Peverell 2009),

has demonstrated female philopatry (i.e. females return to their natal river systems to give

birth) (Phillips 2011, 2012) and that a low population rate of increase means P. pristis is

‘particularly vulnerable to excessive mortalities and rapid population declines, after which

recovery may take decades’ (Musick 2000, Simpfendorfer 2000).

Throughout the life of the project the effects of water quality and habitat availability in the final

void waterbody will be mitigated and managed in the following ways:

Prior to flooding, benching of the final void waterbody edges should be undertaken.

Benching should occur to a depth that takes into account annual water level variations

so that extensive vertical pit walls are not exposed and shallow edge waters are always

available. These benched areas should be constructed to create varied bathymetry


and in sections be embedded with large woody debris and protruding rock to provide

aquatic fauna habitat and create areas of varied flow;

Extensive planting of riparian vegetation should be undertaken prior to connection to

the McArthur River to ensure an established flora exists. Riparian vegetation is

necessary to provide allochthonous input and physical aquatic habitat in the form of

root mats. Riparian vegetation should be maintained until self-generating;

The period of connectivity between McArthur River and final void waterbody is limited

to when river stage height is greater than five metres above the channel invert at both

the up and downstream levees. As such the window of opportunity for fauna to enter

the final void waterbody is limited. Furthermore, output from the final void waterbody to

the McArthur River is longer (up to ~47 days per year) than input from the McArthur

River to the final void waterbody (up to ~12 days) meaning a greater opportunity exists

for fauna to exit.

An engineered solution should be used to restrict the entry of large fauna (e.g. Pristis

pristis) moving upstream into final void waterbody during initial flooding. This could

include a ramp design incorporating vertical batters or gabions. Inlets should, however,

also incorporate sluices or fishways based on a 1:30 slope to allow fauna to exit the

final void waterbody as water levels recede;

During initial pit dumping and tailings deposition, water with high concentrations of

contaminants will be pumped out of pit to remove contaminant mass and treated;

Rapid filling of the final void waterbody will occur first by pumping and then flooding via

the downstream levee opening. Rapid flooding will reduce the interaction of oxygen

with potentially reactive rock;

The period of connectivity between McArthur River and final void waterbody is limited

to high flow events. At such a time that both the up and downstream levee openings

are completed inflow from the McArthur River will result in significant dilution and

flushing of final void waterbody waters;

Quality of site derived waters (including those from Barney Creek pumps) should be

determined prior to them being pumped into the final void waterbody. Treatment of site

waters should occur prior to dewatering. Dewatering to the final void waterbody should

cease if introduced waters are seen to have a measurable effect on final void

waterbody water quality;

Adaptive management allows for water treatment methods (for example reverse

osmosis) to improve final void waterbody water quality; and


Ultimate contingency to isolate final void waterbody from McArthur River should water

quality of the final void waterbody be determined to be at risk of causing detrimental

and ongoing impact to the McArthur River.



Frequent (at least quarterly) ongoing monitoring to determine quality of final void

waterbody waters and output water. Analysis will include a suite of metals (Al, As, Cd,

Cu, Fe, Pb, Mn, Hg, Ni and Zn), electrical conductivity (EC) and sulphate as a

minimum during the operational phase. Analysis of pH should also be undertaken to

determine whether changes are occurring as pH can greatly affect bioavailable of

metals. The regime should include sampling events prior to the wet season to

determine whether there is risk of causing detrimental and ongoing impact to the

McArthur River. In such a case isolation of the final void waterbody should be

considered. Frequent monitoring is also required to determine the accuracy of

predictive modelling used during this project. This will inform whether new modelling

should be undertaken and new mitigation measures considered. Surface water

monitoring data collected over time will also be used to review the sampling regime,

including the frequency of sampling events. For example, if contaminant

concentrations are shown to be consistent over time and at levels which are

considered to be at a low risk of causing detrimental and ongoing impact to the

McArthur River the frequency should be reduced;

Site water discharge should be analysed prior to discharge into the final void

waterbody. This will identify whether there is a risk to final void waterbody waters;

Depth profiling of final void waterbody waters should be undertaken after the final void

waterbody has stabilised to determine water quality at depth and whether a

thermocline or chemocline exists. Results from this monitoring should be used to

indicate whether risk exists in the event vertical mixing is greater than predicted. If risk

is greater than predicted additional mitigation and management actions should be

considered to ensure release from the final void waterbody does not adversely affect

water quality in the McArthur River ; and

Monitoring of final void waterbody fauna (species and abundance) should be

undertaken (at least in the first five years after connection to the McArthur River) to

assess which aquatic fauna species are entering the final void waterbody and whether

species are able to persist. This should also include an assessment of which species

are capable of exiting the final void waterbody and the effectiveness of the sluices or

fishways at providing a pathway for escape. This monitoring will inform whether


alterations to the vertical barriers on the inlet ramps may be required to further restrict

fauna entering or to sluices (fishways) to increase the opportunity for fauna to exit.

Discharge of Surface and Groundwater from the Final Void Waterbody to the 5.4.2

McArthur River

Modelling predicted that water quality in the final void waterbody will improve over time (WRM

2016). However, these models also predict that concentrations of sulphate and zinc will remain

very high (well above SW11 SSTV’s) in the final void waterbody until 2100. The current closure

scenario will see the uncontrolled release of water from the final void waterbody once the levee

walls are opened. Currently waters upstream of MRM are of low electrical conductivity (EC)

and metal concentration. In the case of sulphate for example, which is the main local

contributor to EC, the elevated level in the final void waterbody has the potential to affect the

quality of the receiving McArthur River through surface flow out of the levee openings. Whilst

current modelling predicts median values at SW11 up to the year 2100 will remain well below

the SSTV this outcome is based on the modelled prediction of water quality in the final pit void

waterbody.

Once flooded the final void waterbody will contain a large mass of water with significant head

pressure. As such seepage from the final void waterbody is likely to occur and which may

influence surrounding groundwater and surface waters of the McArthur River which is in close

proximity.

Throughout the life of the project the effects of detrimental water quality discharging from the

final void waterbody will be mitigated and managed in the following ways:

Mitigation measures discussed in Section 5.3.1 aim to maintain final void waterbody

water quality;

Acceptable final void waterbody water quality will be demonstrated prior to removal of

the downstream and upstream levees and connection with the McArthur River;

Adherence to SSTV’s and WDL conditions at downstream compliance point SW11;

Engineering of inlet and outlet will limit the period of connectivity between the McArthur

River and final void waterbody to high flow events. This results in significant dilution of

output water from the final void waterbody. Also, prior to overflowing into the McArthur

River, water within the final void will have been diluted due to the inflows experienced

during high flow events;

Installation of groundwater recovery bores between the final void waterbody and the

McArthur River to reclaim seepage should a large measureable effect be observed;

and


Ultimate contingency to isolate final void waterbody from McArthur River should water

quality of the final void waterbody be determined to be at risk of causing detrimental

and ongoing impact to the McArthur River.



Frequent (at least quarterly) monitoring to determine quality of water within the final

void. Analysis will include a suite of metals (Al, As, Cd, Cu, Fe, Pb, Mn, Hg, Ni and Zn),

electrical conductivity (EC) and sulphate as a minimum during the operational phase.

Analysis of pH should also be undertaken to determine whether changes are occurring

as pH can greatly affect bioavailable of metals. The regime should include sampling

events prior to the wet season to determine whether there is risk of causing detrimental

and ongoing impact to the McArthur River. In such a case isolation of the final void

waterbody should be considered. Frequent monitoring is also required to determine the

accuracy of predictive modelling used during this project. This will inform whether new

modelling should be undertaken and new mitigation measures considered;

Ongoing monthly monitoring of McArthur River water quality downstream of SW11 and

adherence to SSTV’s. Should water quality of the final void waterbody be shown to be

adversely affecting downstream waters of the McArthur River additional water

treatment of final void waterbody should be considered as well as additional measures

to slow or cease outflow from the final void waterbody;

Ongoing annual monitoring of fluvial sediments of the McArthur River at SW11 to

determine whether changes in contaminant load are occurring. Should sediment

contaminant loads at SW11 be shown to be increasing as a result of the release of

water from the final void waterbody additional water treatment of final void waterbody

should be considered as well as additional measures to slow or cease outflow from the

final void waterbody; and

Groundwater monitoring from bores surrounding the final void waterbody to determine

whether seepage is occurring and the rate of seepage.

Reduction in Water, Sediment and Organic Matter in the McArthur River 5.4.3

Upon connection to the McArthur River via the upstream and downstream levee openings,

water and sediment will be transported into the final void waterbody. Reduced flow in the

McArthur River has the potential to reduce available habitat downstream and reduce the

window of opportunity for aquatic fauna to migrate and disperse. Sedimentation also has a

major influence on river morphology including bank and bed creation. The wet season

mobilisation of sediments plays an important role in nutrient cycling in monsoonal rivers. Wet


season flow results in the resuspension, redistribution and breakdown of organic matter

(detritus), which forms the foundation of all aquatic food webs. Flooding of the final void

waterbody, and reduced annual flow of the McArthur River associated with this, has the

potential to remove some of these resources from the McArthur River.

Throughout the life of the project the water, sediment and organic matter loss from the

McArthur River will be mitigated and managed in the following ways:

Initial rapid flooding of the final void waterbody will be undertaken by pumping from the

McArthur River during wet season when flow exceeds 10 m3/s. This will ensure

sufficient flow remains in McArthur River. During this time there will be negligible loss

of sediment and organic matter from the McArthur River; and

Engineering of inlet and outlet will limit the period of connectivity between the McArthur

River and final void waterbody to high flow events when water levels are above five

metres from the river invert. This will subsequently limit the period in which water,

sediment and organic matter will enter the final void waterbody.



Modelling predicts a low net loss (~8%) of total suspended solids (TSS) will occur in

the McArthur River. Monitoring of sediment deposition and accumulation should be

undertaken in the years after the final void waterbody is connected to the McArthur

River by both the upstream and downstream levee openings. This will confirm the

modelled sedimentation rates. If sedimentation rates are found to be vastly higher than

predicted, additional engineered solutions aimed at capturing sediment on the inlet

should be considered.

Stability of Final Void Waterbody Walls, Inlet and Outlet 5.4.4

High surface water velocities experienced during flood events have the ability to scour and

undermine banks and levees which may lead to wall, inlet and outlet failure in the final void

waterbody. In consideration of the fact the final void waterbody will become a permanent

feature in the McArthur River catchment, and that the earth levees of the final void waterbody

will be subject to natural erosive forces over time (e.g. rainfall runoff and settling), maintaining

the integrity of final void waterbody levees, inlet and outlet is vital. This is compounded by the

fact that the design of the inlet and outlet ramps plays a major function in controlling water

interaction of the final void waterbody and McArthur and thus water quality.

Throughout the life of the project the instability of the final void waterbody levees, inlet and

outlet will be mitigated and managed in the following ways:


Final void waterbody levees constructed in accordance with relevant Australian

National Committee on Large Dams (ANCOLD, 2012);

Levee seismic design criteria include building to 1:1000 AEP Max Design Earthquake

(MDE) and 1:500 AEP Operating Basis Earthquake (OBE) criteria;

Ramps designed to withstand flood to 1:100000 AEP (Critical Storm Duration);

An ongoing inspection program and maintenance schedule should be implemented

and considered a key component of the caretaking role. In the event erosion is

observed immediate repairs should be undertaken;

Earth, clay and rock required to maintain and repair final void waterbody levees, inlet

and outlet should be stockpiled to ensure a rapid repair can be undertaken;

Baffling or angling of the inlet ramp should be considered in the design to reduce water

velocities on entry to final void waterbody; and

Ultimate contingency to isolate final void waterbody from McArthur River should the

inlet or outlet ramp fail.



Monitoring should include frequent inspection through observation. In addition periodic

permeability and stability testing of levees and investigations of inlet and outlet stability

should be undertaken. These works will also confirm that the inlet and outlet remain at

five metres above the river invert to ensure the role of the engineered design is

maintained.

Domain 2 - NOEF 5.5

Expansion of NOEF Footprint 5.5.1

The expansion of the NOEF will encroach on the Emu Creek catchment to the north. Despite

being a highly ephemeral creek it provides seasonal habitat during the wet season (see

Appendix 1). In addition to the direct loss of some Emu Creek habitat, a potential pathway for

the introduction of contaminants also exists which may ultimately enter the McArthur River.

A site specific survey of Emu Creek fauna was undertaken to determine the species present

and whether the catchment represented critical habitat for any species or potential habitat for

listed threatened species. It was determined that a limited loss of the Emu Creek catchment

would not affect population viability of any species (Appendix 1)


Throughout the life of the project the loss of Emu Creek habitat and potential water quality

effects will be mitigated and managed in the following ways:

The current NOEF footprint has been minimised by raising the height to avoid

extensive expansion to the north and encroachment on Emu Creek. The current design

encroaches on a small unnamed tributary of Emu Creek which is highly seasonal and a

minor proportion of the catchment; and

A runoff drain will be installed on the northern side of the NOEF to capture surface and

groundwater and restrict flow of these waters into Emu Creek. This water will be

diverted back to a water management dam.



Ongoing monthly monitoring of surface water quality and water level along Emu Creek

including at the confluence with the McArthur River. Surface water monitoring in the

McArthur River downstream of the confluence should also be undertaken at SW11 to

determine adherence to SSTV’s.

Effects on Surface and Groundwater 5.5.2

A number of potential pathways exist for waters which have interacted with the NOEF to enter

groundwater and surface water. In addition, potential exists for water to seep through the

NOEF, including PAF and reactive waste rock, which may ultimately lead to a reduction in

groundwater and surface water quality. Indeed, this interaction has the potential to create long-

lasting detrimental effects.

The NOEF represents a large catchment area and mass. Consequently, large volumes of

surface runoff will occur during rain events. Considering the proximity of Surprise, Barney and

Emu Creeks to the NOEF, runoff has the potential to reduce water quality in particular by

increasing TSS. The mass of the NOEF also has the potential to cause a groundwater mound

which results in rising of the surrounding groundwater level. The subsequent cartage of salts to

the surface can influence water electrical conductivities which may exceed fauna tolerances. In

addition mounding of groundwater can lead to an alteration of inflow to the creeks in close

proximity.

Considering the current design of the NOEF, seepage is most likely to represent the greatest

risk to groundwater and subsequently surface water quality. Current modelling predicts that

surface waters in Barney Creek will be high in sulphates and zinc (WRM 2016) which may

exceed the tolerance of some fauna. During the operational period this has mainly been

attributed to seepage from the TSF. However, post closure and rehabilitation of the TSF

elevated sulphate levels have been directly attributed to seepage from the NOEF. As well as


benign material, the NOEF also contains highly reactive and potentially acid forming rock. In

consideration of this (and predicted sulphate concentrations) it has been considered vital that

interaction of water with these latter waste types is minimised and that any water that has

interacted with the NOEF be captured and managed.

It should be recognised that predicted sulphate concentrations (WRM 2016) in Barney Creek,

which are affected by the NOEF and TSF, may result in aquatic habitat in the lower part of

Barney Creek becoming unfavourable to aquatic fauna at least for some time each year. This is

particularly the case during post-wet periods when flow rates subside resulting in lower dilution

and mixing rates and evapoconcentration. While modelling predicts concentrations of sulphate

will decline after the closure of the TSF and over time, median sulphate concentrations are

predicted to remain above 1000 mg/L for several months a year until 2500 (WRM 2016). These

are, however, generally low flow months when river connectivity is low.

Sampling in Barney Creek has indicated a number of fish species can persist in waters of high

electrical conductivity (EC). Hephaestus fuliginosus, Leiopotherapon unicolor, Melanotaenia

splendida and Nematalosa erebi have been consistently recorded in sulphate affected reaches

of Barney Creek up to 2240 mg/L. This implies that not only can these fish species tolerate

these concentrations but food for these species (for example, invertebrates, algae or plants)

also persists in these environments. In addition Lates calcarifer has been recorded from inland

waters with sulphate concentrations up 2180 mg/L. Based on this some resilience exists for

aquatic fauna to persist in Barney Creek or parts of the Creek. In addition, fish species

recorded from Barney and Surprise Creek are found throughout the McArthur River catchment

and greater Gulf of Carpentaria. Based on this, and the fact Barney Creek does not represent

critical habitat for any species, it is unlikely the loss of any aquatic habitat will result in a

population level effect. However, capture of affected water from Barney Creek remains an

important process to avoid adverse effects on water and habitat quality in the McArthur River.

Throughout the life of the project influence on surface and water quality will be mitigated and

managed in the following ways:

The design of the NOEF (including armouring, angling compaction and permeability)

focuses on achieving physical stability, controlling erosion and sediment loss due to

surface runoff. In addition numerous drainage channels, stilling basins, sediment

dams, sumps and lined (clay or geopolymer) dams (PRODS) will be constructed to

capture runoff and sediment (see O’Kane 2016a). Runoff dam capacities have been

set to have a less than 5% probability of exceedance (spill) over the operating life of

the dam. As such runoff from the NOEF and entry into adjacent creeks will be limited;

During NOEF construction exposed areas of reactive rock will generate contaminated

surface runoff. This runoff will be captured and diverted into water management dams

(PRODS);


The outer layers of the NOEF will comprise benign materials. As such any runoff

should be benign. In the event runoff from the NOEF reaches adjacent creeks it should

be predominantly rainwater which is considered of low risk to aquatic fauna;

The NOEF is designed to minimise seepage through basal foundation preparation,

construction methodologies (including alluvial barriers) and the final cover system. The

final cover design is based on a moisture store-and-release’ and ‘barrier’ concept

which will capture rainwater then progressively dry through evaporation. A dense low

permeability clay layer will also reduce percolation through the NOEF (O’Kane 2016b).

In addition a seepage recovery system will include interceptor drains (URS 2006, KCB

2016a) and recovery bores;

The NOEF design includes encapsulation of high risk materials in the centre to limit

oxidation and seepage of oxidation products into groundwater and surface water

systems. In consideration of this and the fact encapsulating materials in the NOEF will

have limited permeability, percolation of water through the NOEF should be limited;

Two sumps will be installed in Barney Creek which will ultimately capture surface water

runoff. This water will be pumped to a water management dam (or ultimately the final

void waterbody) to avoid outflow into the McArthur River;

An ongoing inspection schedule and maintenance program should be designed which

will include observation and testing to be conducted on the NOEF to ensure integrity

and stability of the outer layers as part of the caretaking role. Erosion and outer layer

breakdown of the NOEF will be immediately repaired;

Compliance with SSTV’s at SW11 and surface water quality standards will be adhered

to; and

Recovery bores, trenches and other recovery methods will be installed and maintained

around the NOEF to capture NOEF seepage where required.



Ongoing periodic monitoring of NOEF stability and maintenance;

Ongoing frequent monitoring of groundwater and surface water in proximity to the

NOEF and downstream including the McArthur River. The frequency of this monitoring

should be monthly during the operational phase to ensure modelling predictions are

accurate as the NOEF expands. Monthly monitoring of surface and groundwater

should be conducted for an extended period post closure to ensure modelled sulphate

concentrations are as predicted and reduce over time. Should sulphate concentrations

be higher than predicted additional mitigation and monitoring actions should be


considered aimed at reducing sulphate concentration of Barney Creek surface waters.

Analysis should include a suite of metals (Al, As, Cd, Cu, Fe, Pb, Mn, Hg, Ni and Zn),

electrical conductivity (EC) and sulphate as a minimum during the operational phase.

Analysis of pH should also be undertaken to determine whether changes are occurring

as pH can greatly affect bioavailable of metals;

Surface waters should be monitored in the McArthur River below the confluence with

Barney Creek to ensure compliance with SSTV’s at SW11 and surface water quality

standards;

Frequent monitoring of the composition of sump water should be undertaken to

ascertain the maximum concentrations of contaminants. These waters should be

analysed for a wide range of analytes to characterise the outflow including metals (Al,

As, Cd, Cu, Fe, Pb, Mn, Hg, Ni and Zn), electrical conductivity (EC), sulphate and pH.

Should unexpected contamination be detected over time an additional risk assessment

should be undertaken to understand potential threats to aquatic fauna and downstream

habitat and water quality. New mitigation measures should subsequently be proposed

to deal with unacceptable new risks;

Monitoring of surface water collected in runoff dams should be undertaken as the

NOEF progresses to determine whether the runoff is indeed benign; and

Ongoing monitoring and maintenance of surface water runoff collection systems and

infrastructure. This includes dam liners, levees and spillways. Repair of damaged

liners, levees and spillways should be undertaken immediately.

Uncontrolled Release of Water from Runoff Management Dams 5.5.3

The required longevity of the NOEF runoff dams means that periodic and ongoing maintenance

will be required. Due to the fact these dams are lined earthed dams, natural erosional and

destabilising processes will occur and affect integrity over time. As such, potential exists for

stored water to be released. This includes spill during large storm events or as a result of levee

failure. Furthermore, linings are likely to breakdown over time which may lead to seepage

through the levee walls.

Throughout the life of the project uncontrolled releases from water runoff dams will be mitigated

and managed in the following ways:

Runoff dams will be constructed in accordance with relevant Australian National

Committee on Large Dams (ANCOLD) Guidelines including ANCOLD’s Guidelines on

Tailings Dam Planning, Design, Construction, Operation and Closure (ANCOLD,

2012). Designed to an earthquake loading of 1:1,000AEP Max Design Earthquake

(MDE) and 1:500 AEP Operating Basis Earthquake (OBE). Crest of spillway above 100


year McArthur River flood level. Spillway design to safely pass a 1:2000 AEP flood

event with a 1:10 AEP wind event wave allowance;

Runoff dams’ capacities have been set to have a less than 5% probability of

exceedance (spill) over the operating life of the dam;

Runoff dams will be lined with low permeability liner to limit seepage; and

An ongoing inspection and maintenance schedule will be initiated which will be a key

component of the caretaking role.



Ongoing biannual monitoring of stability, structure, operation and management of

runoff dams. The frequency of monitoring would reduce once the design is shown to be

stable;

Ongoing monitoring of dam liner integrity; and

Monitoring of surface water collected in runoff dams should be undertaken as the

NOEF progresses to determine whether the runoff is indeed benign.

Domain 3 - TSF 5.6

Groundwater mound 5.6.1

The existing TSF has had the effect of creating a water table mound. As explained by GHD

(2016) the mound has interrupted the natural north-west to south-east groundwater flow in the

area and caused prolonged discharge into Surprise Creek. Rising groundwater has also

resulted in the lifting of sulphate based metalliferous salts which have also affected electrical

conductivities in Surprise Creek. With the subsequent expansion of the TSF, the effect on

groundwater is likely to increase until its eventual decommissioning and subsequent

rehabilitation of the site.

Throughout the life of the project the influence of groundwater through mounding will be

mitigated and managed in the following ways:

Tailings management includes minimising ponding of water on the TSF (GHD 2016).

This will reduce the ultimate mass of the TSF; and

End of mine reprocessing of tailings will reduce long term impacts and limit the risk

period. Rehabilitation and decommissioning of the TSF will see a mining landscape left

safe and secure for humans and animals in the long term (i.e. 100-1000 years) (GHD


2016). Extensive closure objectives are outlined in Section 2.4 of GHD (2016) with

environmental values and ecosystems maintained.



Surface water volumes of the TSF should be monitored and managed on an ongoing

basis; and

Post-closure monitoring should be undertaken in accordance with GHD (2016). The

detailed post-monitoring program will be used to validate the closure design

assumptions and demonstrate successful closure of the TSF.

Uncontrolled Release of Tailings through Spill and Seepage 5.6.2

While management will ensure ponding of water on the surface of the TSF is minimised a

number of potential pathways exist through which water and tailings may escape. This includes

spill as a result of levee failure or overtopping during large rain events. In addition seepage

from the TSF, which has been historically reported, has the potential to affect groundwater and

surface water quality and height. Considering the size of the proposed expansion of the TSF,

seepage represents the greatest risk in relation to an uncontrolled release.

As discussed in section 5.2.4, modelling predicts that surface waters in Barney Creek will

contain high concentrations of sulphates (and zinc) throughout the operational phase and post

closure (WRM 2016). These models also predict that a majority of the sulphate will be derived

from TSF seepage until its eventual decommissioning. As discussed in Section 5.2.4, highest

annual sulphate concentrations (and resulting EC) will be experienced during low flow periods.

While Section 5.2.4 also describes fauna that have resilience to these conditions, the

recognition that seepage will occur and the nature of the expressed surface water, has resulted

in the current Project design incorporating two sumps in Barney Creek. This includes one sump

slightly downstream of the confluence with Surprise Creek and the other in the lower part of

Barney Creek. While the quality of aquatic habitat will inevitably be degraded in Surprise and

Barney Creeks due to the TSF seepage, a primary aim remains to be the protection of the

McArthur River proper. Indeed, if seepage is able to reach the McArthur River this may have

long-lasting effects on habitat, water quality and the aquatic fauna present.

Throughout the life of the project the uncontrolled release of tailings will be mitigated and

managed in the following ways:

The TSF will be constructed in accordance with relevant Australian National Committee

on Large Dams (ANCOLD) Guidelines including ANCOLD’s Guidelines on Tailings

Dam Planning, Design, Construction, Operation and Closure (ANCOLD, 2012). TSF

seismic design criteria will see it built to loading 1:1000 AEP Max Design Earthquake


(MDE) and 1:500 AEP Operating Basis Earthquake (OBE). Furthermore, the TSF

spillway is designed to flood to 1:100000 AEP (Critical Storm Duration). As such the

likelihood of levee failure is considered to be low;

A Dam Safety Emergency Plan (DSEP) will be drafted and adhered to. In the event of

a levee failure repairs will be immediately undertaken;

Installation of recovery bores may be undertaken to reduce the volume of seepage

reaching groundwater and adjacent Creeks;

Ongoing bi-annual monitoring of stability, structure, operation and management (GHD

2016);

Adherence to ANCOLD (2012) Extreme Storm Storage and Wet Season Storage

Allowance criteria. The current TSF design includes a Process Water Dam (PWD). In

the event rainfall leads to a spill, water from the TSF will spill into the PWD. If the event

is large enough to cause a spill from the PWD, water will enter Little Barney Creek. Any

release would, however, coincide with local flooding of the Creek meaning dilution of

tailings would be high;

Tailings management includes minimising ponding of water on the TSF, improving

barrier systems to seepage and groundwater recovery (GHD 2016). Furthermore,

tailings densities will be maximised to reduce permeability of the tailings and thus

seepage;

Installation of sumps on Barney Creek will capture surface water derived from TSF

seepage, reducing risk of tailings reaching McArthur River;

Compliance with SSTV’s at SW11 and surface water quality standards will be adhered

to; and

End of mine reprocessing of tailings and site rehabilitation will reduce long term impact

and limit risk period to 2100.


will be determined through monitoring including:

Ongoing bi-annual monitoring of TSF stability, structure, operation and management

(as per GHD 2016);

Ongoing monthly monitoring of groundwater and surface water to determine seepage

rates and quality until decommissioning. This will include surface waters monitoring

sites in Surprise Creek above and below the TSF and along Barney Creek. Analysis

will include a suite of metals (Al, As, Cd, Cu, Fe, Pb, Mn, Hg, Ni and Zn), electrical

conductivity (EC) and sulphate as a minimum during the operational phase. Analysis of


pH should also be undertaken to determine whether changes are occurring as pH can

greatly affect bioavailable of metals.

Confirmation of Modelling 5.7

The design of the Project and this risk assessment relied heavily on the accuracy of predictive

modelling outputs. Risk rankings, mitigation and monitoring measures in Sections 4 and 5 are

based on the modelling outputs being accurate, with deviation from the modelled predictions

ultimately affecting these outputs. As such, results from the routine monitoring outlined above

should be constantly compared with model predictions. Indeed, if model predictions are not

realised, additional modelling should be undertaken and appropriate mitigation measures

reconsidered.


REFERENCES 6.0

ANCOLD (2012). Guidelines on Tailings Dam Planning, Design, Construction, Operation and

Closure. Report by the Australian National Committee on Large Dams Incorporated.

Anderson, M.J., Gorley, R.N. and Clarke, R.K. (2008) Permanova+ for Primer: Guide to

Software and Statistical Methods. Primer-E Ltd, Plymouth.

Becker, A. and Robson, B.J. (2009). Riverine macroinvertebrate assemblages up to 8 years

after riparian restoration in a semi-rural catchment in Victoria, Australia. Marine and

Freshwater Research 60: 1309 – 1316

Caballero, I. and Boland, K. (2016). McArthur River Open Pit: 3D Hydrodynamic Modelling Run

04 – 20 Year Assessment. Tropical Water Solutions, Woolner.

Clarke, K.R. and Gorley, R.N. (2006). PRIMER v6: User Manual/Tutorial (Plymouth Routines in

Multivariate Ecological Research). Primer-E Ltd, Plymouth.

Department of the Environment (2015). Sawfish and River Sharks Multispecies Issue Paper.

Commonwealth of Australia, Canberra.

Department of Environment and Energy (2017). Species profile and threats database. [online]

Available at: http://www.environment.gov.au/ [Accessed 11 Jan. 2017].

Ecological Management Services (2016). McArthur River Freshwater Aquatic

Macroinvertebrate Assessment 2016. Report to McArthur River Mining, October 2016.

FSANZ (2009). Food Standards Australia New Zealand. Standard 1.4.1. Contaminants and

natural toxicants, issue 103. Food Standards Australia New Zealand, Canberra.

FSANZ (2008). 22nd Australian Total Diet Study. Food Standards Australia New Zealand,

Canberra.

FSANZ (2011). The 23rd Australian Total Diet Study. Food Standards Australia New Zealand,

Canberra.

GHD (2016). Tailings Storage Facility Design Development – Life of Mine Plan. Report to

McArthur River Mining Pty Ltd.

Gustafsson, S., Österlig, M., Skurdal, J., Schneider, L.D. and Calles, O. (2013).

Macroinvertebrate colonization of a nature-like fishway: The effects of adding habitat

heterogeneity. Ecological Engineering 61: 345 – 353.

Halse, S.A., Scanlon, M.D., Cocking, J.S., Smith, M.J. and Kay, W.R. (2007). Factors affecting

river health and its assessment over broad geographic ranges: the Western Australian

experience. Environmental Monitoring and Assessment 134: 161 – 175.


Hanley, R. (1993). Survey of Freshwater Macroinvertebrates and Fish of Ephemeral Creeks

near the McArthur River Mine Site, Borroloola District. Northern Territory Museum

Marine Ecology Technical Report 93/4, Darwin.

Hollingsworth, Dames and Moore (1992). McArthur River Project. Terrestrial and Aquatic

Fauna Surveys. Appendix 22.1. McArthur River Project Draft Environmental Impact

Statement. Prepared for Mount Isa Mines.

Horppila, J., Ruuhijarvi, J., Rask, M., Karppinen, C. Nyberg, K. and Olin, M. (2000). Seasonal

changes in the diets and relative abundances of perch and roach in the littoral and pelagic

zones of a large lake. Journal of Fish Biology 56: 51-72.

Indo-Pacific Environmental (2010). Sampling Procedure for Metal and Lead Isotope Analysis in

Fishes and Macro-invertebrates of the McArthur River. Report to McArthur River Mine.

Indo-Pacific Environmental, Perth.

Indo-Pacific Environmental (2011). Interim Report on the Fish Fauna of the McArthur River,

Northern Territory, September 2010. Report to McArthur River Mine. Indo-Pacific

Environmental, Perth.

Indo-Pacific Environmental (2012). Monitoring of Metals and Lead Isotope Ratios in Fish,

Crustaceans and Molluscs of the McArthur River, 2012. Report to McArthur River Mine.








Indo-Pacific Environmental (2015). Interim Report on the Aquatic Fauna of the McArthur River,

Northern Territory, Early Dry Season 2015. Report to McArthur River Mine. Indo-Pacific


Indo-Pacific Environmental (2016a). Interim Report on the monitoring of metals and Lead

Isotope Ratios in Fish, Crustaceans and Molluscs of the McArthur River, 2016. Report to

McArthur River Mine. Indo-Pacific Environmental, Perth.

Indo-Pacific Environmental (2016b). Report on the aquatic fauna of the McArthur River,

Northern Territory, Early Dry Season 2016. Report to McArthur River Mine. Indo-Pacific



Jones, N.E., Scrimgeour, G.J. and Tonn, W.M. (2008). Assessing the effectiveness of a

constructed arctic stream using multiple biological attributes. Environmental Management

42: 1064 – 1076.

Kirby, G., Morgan, D.L. and Thorburn, D.C. (2009). Fitzroy River Barrage Fishway. Report to

Environs Kimberley.

Klohn Crippen Berger (2016a). McArthur River Mining OMP EIS Groundwater Impact

Assessment. Final Draft. Report to McArthur River Mine.

Klohn Crippen Berger (2016b). Appendix IV: Final Void Water Quality. Report to McArthur

River Mine.

Kyne, P.M., Carlson, J. and Smith, K. 2013. Pristis pristis. The IUCN Red List of Threatened

Species 2013: e.T18584848A18620395. http://dx.doi.org/10.2305/IUCN.UK.2013-

1.RLTS.T18584848A18620395.en

Lang, J.W. (1987). Crocodilian behaviour: implications for management. In: Webb, G.J.W,

Manolis, C. and Whitehead, J. (eds.) Wildlife Management: Crocodiles and Alligators.

Surrey Beatty, Sydney.

Lamche, G. (2007). The Darwin-Daly regional AUSRIVAS models – Northern Territory: User

Guide. Department of Natural Resources, Environment and the Arts, Darwin.

Lloyd, J. and Cook, S. (2002). Australia-Wide Assessment of River Health: Northern Territory

AusRivAS Sampling and Processing Manual. Environment Australia, Canberra.

Louhi, P., Mykrä, H., Paavola, R., Huusko, A., Vehanen, H., Mäki-Petäys, A. and Muotka, T.

(2011). Twenty years of stream restoration in Finland: little response by benthic

macroinvertebrate communities. Ecological Applications 21: 1950 -1961.

METServe (2016). Overburden Management Project: Draft Project Description and

Justificaiton. Report to McArthur River Mining.

Midgley, S.H. (1975). McArthur River Fish Survey. Report prepared for Gunn Rural

Management for Mount Isa Mines.

Midgley, S.H. (1982). A Biological Resource Study of Freshwaters of the Lake Eyre Drainage,

the Inland Drainage and the Gulf of Carpentaria Drainage. Report for NT Fishing Industry

Research and Development Trust Fund.

Midgley, S.H. (1994). A Biological Resource Study of Freshwaters of some River Systems

North Queensland and the Northern Territory. Midgely and Midgley Consultants.

Musick, J.A., Harbin, M.M., Berkeley, S.A., Burgess, G.H., Eklund, A.M., Findley, L., Gilmore,

R.G., Golden, J.T., Ha, D.S., Huntsman, G.R., McGovern, J.C., Parker, S.J., Poss, S.G.,

Sala, E., Schmidt, T.W., Sedberry, G.R., Weeks, H., and Wright, S.G. (2000). Marine,

http://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T18584848A18620395.en

http://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T18584848A18620395.en


estuarine, and diadromous fish stocks at risk of extinction in North America. Fisheries 25:

6-30.

O’Kane Consultants (2016a). NOEF Surface Water Management Sediment Dams and Stilling

Basins. Report to Glencore-McArthur River Mining Pty Ltd.

O’Kane Consultants (2016b). NOEF Cover System and Landform Design in Support of the EIS

Submission. Report to Glencore-McArthur River Mining Pty Ltd.

Peverell, S. C. (2009). Sawfish (Pristidae) of the Gulf of Carpentaria, Queensland, Australia.

MSc Thesis. James Cook University.

Phillips, N. (2012). Conservation genetics of Pristis sawfishes in Australian waters. PhD Thesis.

Murdoch University.

Phillips, N. M., Chaplin, J. A., Morgan, D. L. and Peverell, S. C. (2011). Population genetic

structure and genetic diversity of three critically endangered Pristis sawfishes in Australian

waters. Marine Biology 158: 903–915.

Pusey, B.J. and Arthington, A. H. (2003). Importance of the riparian zone to the conservation

and management of freshwater fish: a review. Marine and Freshwater Research 54: 1-16.

RPS Bowman Bishaw Gorham (2006). Preliminary Survey of Freshwater Sawfish and Other

Fish of The McArthur River, Northern Territory. Appendix L; McArthur River Mine Open Cut

Project. Public Environmental Report.

Simpfendorfer, C.A. (2000). Predicting recovery rates for endangered western Atlantic

sawfishes using demographic analysis. Environmental Biology of Fishes 58:371-377

Storey, A.W. and Creagh, S. (2014). The functional habitat concept does apply to fish

assemblages of the regulated Lower Ord River, Western Australia. Journal of the Royal

Society of Western Australia 97:389-407.

Thorburn, D.C., Peverell, S., Stevens, J. D., Last, P. R. and Rowland, A. J. (2003). Status of

Freshwater and Estuarine Elasmobranchs in Northern Australia. Report to Natural Heritage

Trust.

Thorburn. D., Morgan, D., Gill, H., Johnson, M., Wallace-Smith, H., Vigilante, T., Gorring, A.,

Croft, I. and Fenton, J. (2004). Biology and Cultural Significance of the Freshwater Sawfish

(Pristis microdon) in the Fitzroy River Kimberley, Western Australia. Report to Threatened

Species Network.

Thorburn, D. C., Morgan, D. L., Rowland, A. J. and Gill, H. S. (2007). Freshwater Sawfish

Pristis microdon Latham, 1794 (Chondrichthyes: Pristidae) in the Kimberley Region of

Western Australia. Zootaxa 1471:27-41.

URS (2005). McArthur River Mine Open Cut Project Draft Environmental Impact Statement.


WRM (2016). Surface Water Impact Assessment for the McArthur River Mine Overburden

Management Project Environmental Impact Statement. Report to McArthur River Mining.


APPENDIX 1 – SURVEY OF FISH AND CRUSTACEANS OF EMU CREEK AND

TISSUE METAL CONTENT 2016.

SURVEY OF FISH AND CRUSTACEANS OF EMU CREEK AND TISSUE METAL CONTENT

2015

Prepared for:

McArthur River Mine

PO Box 36821

Winnellie NT 0821

Prepared by:


PO BOX 191


Phone: (08) 9444 1422

Fax: (08) 9444 1466

ACN 120 114 365

Project ID: 15006.2

15006.2 Emu Creek Survey, Rev 0, October 2015 i

Document Control


A Internal Draft S Longbottom 30-06-2015 D. Thorburn 23-07-2015

B Client Draft D. Thorburn 24-07-2015 G. Taylor (MRM)

C. Dobson (MRM)

D. Moss (METSERVE)

24-09-2015

C Client Draft D. Thorburn 06-10-2015 D. Moss (METSERVE) 07-10-2015

0 Issued to Client D. Thorburn 30-10-2015

Disclaimer

This report has been prepared on behalf of and for the exclusive use of McArthur River Mine. Reproduction or use of any part of this report (including data) is not permitted without the written permission of McArthur River Mine. Indo-Pacific Environmental Pty Ltd however, does not warrant in any way whatsoever that the material contained in this report is fit for use for any other purpose or by any other party than those aforementioned.

15006.2 Emu Creek Survey, Rev 0, October 2015 ii

EXECUTIVE SUMMARY

The McArthur River Mine (MRM) Overburden Management Project Environmental Impact

Statement (EIS) outlines a proposal to expand the Northern Overburden Emplacement Facility

(NOEF) with much of the planned expansion occurring on the northern side of the current

NOEF site. Emu Creek which is located to the immediate north of the NOEF was identified as

being potentially impacted by the expanded footprint. A baseline survey of the aquatic fauna of

Emu Creek was subsequently undertaken in order to provide data against which a predictive

impact assessment and post-construction monitoring could be compared. Tissue samples for

metal, metalloid and lead isotope ratio (PbIR) analyses were also collected.

Water was found to be present at 10 sites along Emu Creek between the junction of the

McArthur River and the Carpentaria Highway with eight of these found to contain fish and

crustaceans. A total of 405 fish from thirteen species and 12 crustaceans from two species

were recorded. With the exception of Mogurnda mogurnda (which has been found to occur

exclusively in tributaries) the fish species recorded have been captured throughout the main

channel McArthur River. Melanotaenia splendida was the most prevalent species comprising

32.8% of the total fish captured and was found throughout the Creek. Ambassis macleayi was

the next most numerous, however, all individuals were captured from a single water hole. The

crustacean Macrobrachium spp. was recorded at 3 sites but only in very low abundance. The

freshwater crab Austrothelphusa transversa was recorded from five sample sites and was in

comparatively high abundance. Size data indicated the predominance of juvenile and sub adult

individuals. Recruitment was therefore considered to occur annually from the McArthur River

as opposed to permanent water holes which appeared rare in Emu Creek.

A total of 80 tissue samples were collected and analysed during the current survey. Tissue

metal and metalloid concentrations were seen to be generally low in all species analysed. The

highest lead concentration recorded during the current study was 0.17 mg/kg from a M.

splendida from SW 26. This was, however, far lower than the Maximum Permitted

Concentration (MPC) for lead (i.e. 0.5 mg/kg) outlined by FSANZ (2009). In general similar

metal and metalloid concentrations were recorded from M. splendida, Nematalos erebi,

Leiopotherapon unicolor and Macrobrachium spp tissue between sample sites.

Lead isotope ratio (PbIR) values for samples collected throughout Emu Creek were generally

comparable between sites and to historical data collected in the McArthur River. Results of

metal, metalloid and PbIR tissue analysis did not suggest mine derived lead was present in

aquatic fauna.

15006.2 Emu Creek Survey, Rev 0, October 2015 iii

TABLE OF CONTENTS

1.0 INTRODUCTION 1

1.1 Background 1

1.2 Study Objectives 1

2. METHODS 2

2.1 Survey Area and Site Selection 2

2.2 Field Procedures 2

2.2.1 Site Data 2

2.2.2 Sampling for Composition, Population Structure and Distribution 7

2.2.3 Collection of Samples for Metal Analysis 7

2.3 Analysis of Metal Samples 8

3.0 RESULTS AND DISCUSSION 10

3.1 Sites Surveyed and Water Quality 10

3.2 Composition, Distribution and Population Structure 10

3.3 Metal Results 18

3.3.1 Metal and Arsenic Concentrations and Comparison to MPC’s 18

3.3.2 Mean concentrations and comparison to relevant locations 23

3.3.3 Lead Isotope Ratios 23

4.0 CONCLUSIONS AND RECOMMENDATIONS 32

5.0 REFERENCES 33

15006.2 Emu Creek Survey, Rev 0, October 2015 iv

LIST OF TABLES

Table 1. Locations at which water was found in the Emu Creek Survey area during 2015.

Table 2. Temperature, conductivity, salinity, pH, dissolved oxygen, average length, average

width, average depth, total volume and habitat description of sites containing water in the Emu

Creek survey area 2015.

Table 3. Fish and crustacean abundance and diversity recorded from sites sampled in Emu

Creek during 2015

Table 4. Total number of individuals within species captured at sites sampled during the 2015

Emu Creek survey.

Table 5. Estimated density (m3) of fish, based on volume of water sampled for sites during the

2015 Emu Creek survey.

Table 6. Composition of fishes captured at all sites in the Emu Creek survey area during 2015.

Table 7. Estimated volume of water sampled (based upon average width x depth x transect

length for electrofishing sites and total seine area x depth for seine net sites), total number of

individuals captured and density (m3) of fish at sites sampled in Emu Creek during 2015 survey.

Table 8. Metals analysed (and arsenic) and maximum permitted concentrations (wet weight) in

fish and crustaceans provided by Food Standards Code 1987, Food Standards Australia and

New Zealand 2000 and 2009.

Table 9. Mean (±SE) metal and metalloid concentrations (mg/kg) found in various tissues of

aquatic fauna at sites surveyed in Emu Creek during April 2015. .

LIST OF FIGURES

Figure 1. Indicative area of Emu Creek Survey 2015. Red line shows the extent of creek bed

investigated.

Figure 2. Locations at which water was found in the Emu Creek Survey during 2015.

15006.2 Emu Creek Survey, Rev 0, October 2015 v

Figure 3. Typical creek bed features in the Emu Creek survey area 2015, a) stony creek bed

upstream of Emu 6, b) sandy sections around SW26 and c) muddy substrate closer to the

McArthur River junction.

Figure 4. Comparison of monthly rainfall (mm) recorded at McArthur River Mine during the

2014-2015 wet season (November to April) with the mean monthly rainfall collected between

1969-2015 (Bureau of Meteorology 2015).

Figure 5. Percentage length frequency histogram for M. splendida collected throughout the

Emu Creek survey area in 2015.

Figure 6. Percentage length frequency histogram for N. erebi collected throughout the Emu

Creek survey area in 2015.

Figure 7. Percentage length frequency histogram for L. unicolor collected throughout the Emu


Figure 8. Species collected for metal and lead isotope analysis in the Emu Creek survey area

2015, including a) M. splendida b) N. erebi, c) L. unicolor and d) Macrobrachium spp.

Figure 9. Comparison of mean Lead and Zinc concentrations (mg/kg wet weight) in trunked M.

splendida collected in Emu Creek during April 2015.

Figure 10. Comparison of mean Lead and Zinc concentrations (mg/kg wet weight) in N. erebi

muscle collected in Emu Creek during April 2015. Corresponding data from sampling sites Top

Crossing, SW 23 and SW 11 obtained during the 2014 McArthur river catchment survey have

been include to provide context.

Figure 11. Comparison of mean Lead and Zinc concentrations (mg/kg wet weight) in

L.unicolor muscle collected in Emu Creek during April 2015.

Figure 12. Lead isotope ratios (207Pb/206Pb and 208Pb/206Pb) attained from fish tissues

collected in Emu Creek during 2015.

Figure 13. Mean lead isotope ratios (207Pb/206Pb and 208Pb/206Pb) attained from fish

tissues collected in Emu Creek during 2015.

15006.2 Emu Creek Survey, Rev 0, October 2015 vi

APPENDICES

Appendix 1. Metal and arsenic concentrations (mg/kg wet weight) and lead isotope ratios in

tissues collected from Emu Creek fauna.

15006.2 Emu Creek Survey, Rev 0, October 2015 1

1.0 INTRODUCTION

1.1 Background

The McArthur River Mine (MRM) Overburden Management Project Environmental Impact

Statement (EIS) outlines a proposal to expand the Northern Overburden Emplacement Facility

(NOEF) with much of the planned expansion occurring on the northern side of the current

NOEF site. Emu Creek, which is located to the immediate north of the NOEF, was

subsequently identified as being potentially impacted by the expanded footprint. Furthermore,

the proximity of Emu Creek to the expanded NOEF represented a potential pathway for the

direct introduction of contaminants into the main channel of the McArthur River. With this in

mind, and the fact that no information had been collected on the fish and crustacean fauna

occurring in Emu Creek, MRM engaged Indo-Pacific Environmental to conduct a biological

survey from its junction with the McArthur River upstream to the crossing of the Carpentaria

Highway.

The aim of this survey was to collect baseline data on the fish and crustacean fauna present

prior to the potential expansion of the NOEF. In addition the current survey aimed to collect

tissue samples from aquatic fauna for metal, metalloid and lead isotope ration (PbIR) analysis.

This baseline data would facilitate a predictive impact assessment and the comparison of data

collected during any post-construction monitoring and aid in identifying whether Emu Creek

aquatic fauna was impacted and to what extent.

1.2 Study Objectives

Two clear objectives were identified to achieve the study aim. These being:

Identify the current composition, population structure and distribution of fish and

crustacean species present in Emu Creek; and

Collect samples from representative species such that baseline metal levels for fish in

Emu Creek could be established.


2. METHODS

2.1 Survey Area and Site Selection

The survey of Emu Creek took place over the period 31st of March to 1st of April 2015 and

encompassed the section of Emu Creek between the McArthur River junction and the

Carpentaria Highway (Figures 1 and 2). Sampling was conducted under Special Permit no.

2011-2012/S17/3300. A majority of Emu Creek was dry at the time of the survey indicating the

ephemeral nature of the Creek. Limited permanent water appeared to exist with a majority of

the small water holes encountered likely be completely dry in most years. Emu Creek was

typified by a stony creek bed upstream of MRM surface water monitoring sampling site SW26

(Figure 3(a)). Downstream from SW26 the creek bed was initially sandy turning to muddy

substrates as it approached the McArthur River (Figure 3(c)). Access to the survey area was

gained via the Carpentaria Highway and tracks maintained by MRM.

Rainfall in the catchment during the 2014-2015 wet season was below the annual average (i.e.

673 mm cf. 758 mm) recorded between 1969 and 2015 (BOM 2015). Furthermore, almost half

of the rainfall recorded during the 2014-2015 wet season atypically occurred in December 2014

and with over double the rain generally experienced in that month recorded (i.e. 306 mm in

December 2014 cf. 125 in December 1969-2015) (Figure 4). In addition, rainfall in February

and March 2015 was half the annual means for those months. As such water levels were very

low in Emu Creek at the time of survey with water limited to a small number of shallow remnant

pools. In light of the limited water and vehicle access a majority of the survey line shown in

Figure 1 was accessed by foot. Once a location containing water was found the location was

recorded using handheld GPS and sampling equipment was carried to the site from the closest

vehicle access point. A total of ten locations containing water were subsequently located and

surveyed.

2.2 Field Procedures

2.2.1 Site Data

Water temperature (oC), conductivity (mS), salinity (ppt), pH, and dissolved oxygen (mg/L) were

recorded for each sample site as well as the pool length, width and water depth (m). Notes on

the immediate habitat were also recorded (e.g. substrate type, aquatic flora and riparian

vegetation cover etc.) and a photo taken.


Figure 3. Typical creek bed features in the Emu Creek survey area 2015, a) stony creek bed

upstream of Emu 6, b) sandy sections around SW26 and c) muddy substrate closer to the

McArthur River junction.


Figure 4. Comparison of monthly rainfall (mm) recorded at McArthur River Mine during the

2014-2015 wet season (November to April) with the mean monthly rainfall collected between

1969-2015 (Bureau of Meteorology 2015).

0

50

100

150

200

250

300

350

Nov Dec Jan Feb Mar Apr

Rai

nfa

ll (m

m)

Mean 1969-2015

2014-2015


2.2.2 Sampling for Composition, Population Structure and Distribution

Seine nets were used for capturing fish to satisfy the first objective of this survey. Captured

fish and crustaceans were identified to species level and the total number of each species

recorded. The total length of each individual fish was recorded (mm) while occipital carapace

length (OCL), i.e. the length between the eyes and end of the carapace (mm), was used for the

crustacean Macrobrachium spp. For the purpose of abundance calculations an estimate of the

seine net area was made if the sample area was less than the pool surface area.

Indo-Pacific Environmental Pty Ltd aims to minimise mortality and alterations to the natural

ecosystem in all circumstances. As such all animals not required for metal analysis were

returned alive to the corresponding sampled pool as quickly as possible. During the current

study a single ‘Glossogobius spp’ was also used to collectively refer to Glossogobius giurus

and Glossogobius aureus. This is due to the fact that these two species are difficult to

distinguish without the use of a microscope which is particularly problematic with smaller

individuals. Both species have been recorded throughout the McArthur River catchment and

as such both were considered likely to be present in Emu Creek. As these species also occupy

a comparable ecological niche it was considered appropriate to record these species as one

and ensure the successful live release of captured individuals.

2.2.3 Collection of Samples for Metal Analysis

Samples of the fish Melanotaenia splendida (Eastern Rainbowfish), Nematalosa erebi (Bony

Bream) and Leiopotherapon unicolor (Spangled Perch) and the crustacean Macrobrachium spp

were retained for metal analysis in accordance with the ‘Sampling Procedure for Metal Analysis

in Fish of the McArthur River’ (Indo-Pacific Environmental 2010). These species of fish have

previously been collected for metal analysis from other parts of the McArthur River catchment

and therefore provided the opportunity for comparison with the results attained from Emu Creek

samples. In some instances, and where water clarity permitted, an LR-24 Smith-Roots

backpack electrofisher was also utilised to selectively target these specific species to reduce

disturbance of non-target species. Fish retained for analysis were placed in a labelled zip lock

bags, immediately placed on ice and frozen as soon as possible.

On a number of occasions only small individuals of M. splendida, N. erebi and L. unicolor were

encountered. As such tissue from several individuals of a comparable size was combined to

provide a single sample which was sufficient for analysis (see Appendix 1). When very small

quantities of tissue were provided for analysis the metal reporting limit of the analysis were

often raised for that specific sample. This is due to that fact that digestion and measurement of


smaller amounts of tissue (i.e. <1 g) makes the analytical method less sensitive as only a very

low quantity of the target analyte is present. As discussed in Section 2.3, for the purpose of

mean and median calculations the reporting limit is substituted as the concentration value of an

analyte when the concentration was found to be below the reporting limit. Combining tissue

from multiple small individuals was subsequently considered an appropriate method to avoid

the raising of reporting limits. This would therefore provide mean and median values closer to

actual values. Furthermore, the inclusion of a higher number of individuals in a sample

provided a greater indication of the overall metal concentrations occurring within a species at a

particular sampling location.

2.3 Analysis of Metal Samples

Tissue samples for analysis were prepared in accordance with the ‘Sampling Procedure for

Metal Analysis in Fish of the McArthur River’ (Indo-Pacific Environmental 2010). Muscle tissue

samples were attained from N. erebi and L. unicolor. Liver samples were also attained from L.

unicolor when collected individuals were of sufficient size. Melanotaenia splendida were

analysed whole with the head, tail, fin and gut removed (referred to as a trunk). Muscle tissue

was collected from the tails of Macrobrachium spp. Dissected tissue was rinsed in distilled

water, placed in press seal polyethylene food grade plastic bags, frozen and forwarded on to

the NATA accredited Marine and Freshwater Research Laboratories (MAFRL) at Murdoch

University, Western Australia. Tissue samples were subsequently digested using ultra-pure

nitric acid, hydrogen peroxide and hydrochloric acid as per USEPA method 200.3 and analysed

by inductively coupled plasma mass spectrometry (ICP-MS) for 16 metals and arsenic (mg/kg

wet weight) and the lead isotope (PbIR) ratios 207Pb/206Pb and 208Pb/206Pb (Appendix 1).

Metal and arsenic concentrations were compared between sites and also to the Maximum

Permitted Concentrations (MPC) of metal contaminants outlined in Standard 1.4.1

(Contaminants and natural toxicants) of Food Standards Australia New Zealand (2009) to

provide some context to the concentrations encountered. This Standard provides MPC’s for

lead in fish and molluscs; arsenic in fish, molluscs and crustaceans; and cadmium in molluscs

(see Table 8). While no MPC for copper or zinc is listed in the 2009 Standard, MPCs for

copper, zinc and cadmium are listed in the Food Standards Code (1987), and Food Standards

Australia New Zealand in 2000 (Standard A12: Metals and contaminants in food). These limits

were therefore included to increase the level of scrutiny applied to samples collected.

Mean (±SE) metal concentrations were calculated from all respective species and tissues

analysed. In order to facilitate these calculations, tissue metal concentrations of analytes which

were found to be below the reporting limit were considered to be equal to the reporting limit for

the purpose of these calculations. As such some of the mean values presented in this report


are higher than the actual values.

Of particular relevance to MRM operations were the concentrations of lead and zinc, the

primary products of McArthur River Mine. Therefore mean lead and zinc concentrations for M.

splendida, N. erebi and L. unicolor recorded during this survey were compared graphically to

2014 data collected at Top Crossing, SW23 (Surprise Creek) and SW11 to provide some

regional context (Indo-Pacific Environmental 2015).

Analysis of PbIR potentially allows lead derived from the MRM ore body to be identified and

tracked throughout the catchment. PbIR values (207Pb/206Pb and 208Pb/206Pb) were

subsequently plotted by site, as was the mean recorded from each sample site. Isotope ratios

of Top Crossing, SW23 (Surprise Creek) and SW11 were added to these plots to provide

context, as was average background ratio values (207Pb/206Pb = 0.83 and 208Pb/206Pb =

2.06) derived from the Present Day Average Crustal (PDAC) lead (Stacey and Kramer 1975),

and an average of MRM ore ratios (taken from the ranges 207Pb/206Pb = 0.94 to 0.95, and

208Pb/206Pb = 2.15 to 2.24) (Munksgaard et al. 1998).


3.0 RESULTS AND DISCUSSION

3.1 Sites Surveyed and Water Quality

Figure 1 denotes the area of Emu Creek investigated during the current survey. This section of

Emu Creek included two surface water (SW) monitoring sites used by MRM (SW26 and

SW30). While SW30 was not found to contain water at the time of the survey, a small water

hole was found ~150 m downstream (referred to as Emu 9). The ten locations at which water

was found and subsequently sampled are shown in Table 1 and Figure 2. Physico-chemical

properties of those water holes can be seen in Table 2.

Crustaceans and/or fish were found to be present at eight of the ten sites sampled (Tables 1

and 3). The two sites that did not contain fish, Emu 2 and Emu 5, were shown to have very

high water temperature, reduced pH and low dissolved oxygen (Table 2). Aquatic fauna

showed remarkable tolerances to elevated temperatures and low dissolved oxygen which was

recorded at a number of sites sampled. Salinity was very low at all sites surveyed suggesting

that flow in Emu Creek is mainly rainfall driven (Table 2).

3.2 Composition, Distribution and Population Structure

Thirteen species of bony fish and two species of crustaceans (Macrobrachium spp. and the

freshwater crab Austrothelphusa transversa) were recorded from Emu Creek (Tables 3, 4, 5, 6

and 7). With the exception of Mogurnda mogurnda (which has been found to occur exclusively

in tributaries) the fish species recorded have been captured throughout the main channel

McArthur River. The two sites with the highest species diversity were Emu 6 and Emu 9

containing 12 and 11 fish species, respectively. Water lilies were observed at both these sites

which are often an indication that water is permanent.

Of the 405 individual fish recorded M. splendida was the most prevalent species, comprising

32.8% of the total fish captured and present at five of the eight sites at which fish were found

(Table 4 and 6). Although Ambassis maclaeyi had the second highest number of individuals

captured (n=104) all the captured individuals for this species came from one sample site (Emu

6). The species was also observed at Emu 9.

Nematalosa erebi and L. unicolor were found to be widespread in Emu Creek and represented

8.4% and 6.9% of total fish captured, respectively (Tables 3, 4 and 6). These two species also

displayed reasonably consistent capture densities at sites of capture (Table 5). Although

Oxyeleotris selheimi had a similar total number captured and were similarly distributed most


Table 1. Locations at which water was found in the Emu Creek Survey area during 2015. Sites

in black contained no aquatic fauna, sites in blue were found to contain aquatic fauna and sites

in red were found to contain aquatic fauna including target species for metals and metalloid

analysis.

Site Name Latitude Longitude

Emu 1 16 25.066 S 136 08.036 E

Emu 2 16 24.160 S 136 07.183 E

Emu 3 16 24.144 S 136 07.171 E

SW 26 16 24.096 S 136 07.159 E

Emu 4 16 23.724 S 136 06.928 E

Emu 5 16 23.054 S 136 06.529 E

Emu 6 16 22.989 S 136 06.435 E

Emu 7 16 22.359 S 136 06.222 E

Emu 8 16 22.343 S 136 06.208 E

Emu 9 16 22.146 S 136 06.118 E


Table 2. Temperature, conductivity, salinity, pH, dissolved oxygen, average length, average width, average depth, total volume and habitat description of sites

containing water in the Emu Creek survey area 2015.

Site Temp.

(oC)

Conductivity

(mS)

Salinity

(ppt)

pH DO

(mg/L)

Length

(m)

Avg width

(m)

Avg Depth

(m)

Volume

(m3) Habitat Description

Emu 1 27.3 0.438 0.2 7.03 2.0 6 0.8 0.3 1.4 Puddle in depression 100m from McArthur, 100% silt bottom, deep mud and steep mud banks

Emu 2 33.8 0.069 0.0 6.03 2.2 5 3.0 0.2 3.0 Pool, silty mud, tree on upstream side, rock wall on downstream SW side

Emu 3 29.7 0.069 0.0 4.94 1.6 20 3.0 0.2 12.0 Pool at base of tree at bend in creek, 90% mud, 10% pebble

SW 26 27.7 0.445 0.2 7.75 1.5 2 0.5 0.15 0.2 Small muddy puddle in depression 95% mud silt, 5% pebble

Emu 4 30.1 0.056 0.0 6.66 3.3 17 1.5 0.6 15.3 Mud bank / bottom tributary 12m X 1.2 with rocky pool section 5X5m in main creek bed

Emu 5 37.1 0.037 0.0 4.90 3.2 20 2.5 0.4 20.0 Rocky pool, with steep rocky wall on west side, grassy bank on east

Emu 6 34.3 0.524 0.2 7.80 2.8 80 10.0 0.3 240.0 Pool with lilies, width of creek bed, 60% rock / rubble, 10% sand, 10% detritus, 20% silt

Emu 7 30.8 0.723 0.3 7.58 5.0 4 2.0 0.2 1.6 Rocky pool at base of tree, creek bed very rocky here

Emu 8 30.9 1.078 0.5 7.91 4.2 7 4.0 0.6 16.8 Rocky steep sided pool, undercutting tree on each bank side

Emu 9 35.8 0.437 0.2 7.72 4.8 15 15.0 0.5 112.5 Pool with lilies, large boulders on upstream with course sand on downstream


Table 3. Fish and crustacean abundance and diversity recorded from sites sampled in Emu Creek during 2015.

Site Name Emu1 Emu2 Emu3 SW26 Emu4 Emu5 Emu6 Emu7 Emu8 Emu9

Ambassis maclaeyi

X

X

Amniataba percoides

X X X X

Glossamia aprion

X

X

X

Glossogobius sp

X

X X X X

Hephaestus fuliginosus

X

X X X X

Leiopotherapon unicolor

X X

X X X X

Melanotaenia splendida

X

X X X X

Mogurnda mogurnda

X Nematalosa erebi

X

X X X X

Neosilurus hyrtlii

X X X X

Oxyeleotris selheimi X

X X

X

X Strongylura krefftii

X

X

Toxotes chatareus

X

X

Number of Fish Species 1 0 3 5 1 0 12 7 9 11

Macrobrachium spp.

X

X

X Austrothelphusa transversa

X

X

X X X

Number of Crustacean species 0 0 1 1 1 0 1 1 2 1


Table 4. Total number of individuals within species captured at sites sampled during the 2015 Emu Creek survey.

Emu 1 Emu 2 Emu 3 SW26 Emu 4 Emu 5 Emu 6 Emu 7 Emu 8 Emu 9 Total

Ambassis maclaeyi 104

104

Amniataba percoides 3 2 2 14 21

Glossamia aprion 3 1

1 5

Glossogobius spp 5 1 3 4 1 14

Hephaestus fuliginosus 2 2 5

3 12

Leiopotherapon unicolor 2 3 3 10 6 4 28

Melanotaenia splendida 4

17 48 42 22 133

Mogurnda mogurnda

1

1

Nematalosa erebi 1 7 13 12 1 34

Neosilurus hyrtlii 1 4 3 9 17

Oxyeleotris selheimi 24 2 3 1 1

31

Strongylura krefftii 1 2 3

Toxotes chatareus

2 2

Total 24 0 8 16 1 0 141 85 71 59 405


Table 5. Estimated density (m3) of fish, based on volume of water sampled for sites during the 2015 Emu Creek survey.

Emu 1 Emu 2 Emu 3 SW26 Emu 4 Emu 5 Emu 6 Emu 7 Emu 8 Emu 9 Total

Area sampled (m3) 1.4 3 12 0.2 15.3 20 67.5 1.6 16.8 72 209.8

Ambassis maclaeyi

1.54

0.50

Amniataba percoides

0.04 1.25 0.12 0.19 0.10

Glossamia aprion

15.00

0.01

0.01 0.02

Glossogobius spp

25.00

0.01 1.88 0.24 0.01 0.07

Hephaestus fuliginosus

15.00

0.03 3.13

0.04 0.06

Leiopotherapon unicolor

0.17

0.04 6.25 0.36 0.06 0.13

Melanotaenia splendida

0.33

0.25 30.00 2.50 0.31 0.63

Mogurnda mogurnda

0.00 0.06

0.00

Nematalosa erebi

0.07

0.10 8.13 0.71 0.01 0.16

Neosilurus hyrtlii

0.01 2.50 0.18 0.13 0.08

Oxyeleotris selheimi 17.14

0.17 15.00

0.01

0.06

0.15

Strongylura krefftii

0.01

0.03 0.01

Toxotes chatareus

0.03 0.01


Table 6. Composition of fishes captured at all sites in the Emu Creek survey area during 2015.

Species name n % Composition

Melanotaenia splendida 133 32.84

Ambassis maclaeyi 104 25.68

Nematalosa erebi 34 8.40

Oxyeleotris selheimi 31 7.65

Leiopotherapon unicolor 28 6.91

Amniataba percoides 21 5.19

Neosilurus hyrtlii 17 4.20

Glossogobius spp 14 3.46

Hephaestus fuliginosus 12 2.96

Glossamia aprion 5 1.23

Strongylura krefftii 3 0.74

Toxotes chatareus 2 0.49

Mogurnda mogurnda 1 0.25

Total captured 405


Table 7. Estimated volume of water sampled (based upon average width x depth x transect

length for electrofishing sites and total seine area x depth for seine net sites), total number of

individuals captured and density (m3) of fish at sites sampled in Emu Creek during 2015 survey.

Fish

Site Name Volume sampled (m3) Total N Density

Emu 1 1.4 24 17.14

Emu 2 3 0 0.00

Emu 3 12 8 0.67

SW26 0.2 16 80.00

Emu 4 15.3 1 0.07

Emu 5 20 0 0.00

Emu 6 67.5 141 2.09

Emu 7 1.6 85 53.13

Emu 8 16.8 71 4.23

Emu 9 72 59 0.82

Total 209.8 405 1.93


sites contained very few individuals (less than 3 individuals) with the exception of Emu 1 where

24 juveniles were captured.

Macrobrachium spp. was recorded at 3 sites (i.e. SW26, Emu 6 and Emu 8) in low abundance

(Table 3). Macrobrachium spp was found as far upstream as Emu 8 indicating the species’

ability to migrate upstream from the McArthur River when water is present. Austrothelphusa

transversa was recorded from five sample sites and was in comparatively high abundance.

Length frequency histograms for captured M. splendida, N. erebi and L. unicolor captured

indicated the predominance of juvenile and sub adult individuals (Figures 5, 6 and 7). Only one

adult N. hyrtlii (445mm TL) and two near adult Strongylura krefftii (460mm and 370mm TL)

were captured. In addition to the limited water present at the time of the survey, this size data

also suggests Emu Creek contains little permanent water. Recruitment would subsequently

occur annually with fish coming from the McArthur River when flow is present (as opposed to

permanent water holes should they be present).

3.3 Metal Results

A total of 80 tissue samples were collected and analysed during the current survey (Figure 8,

Appendix 1). For interpretation of data four reporting areas between SW 26 and the highway

crossing sites were identified. Of these, several sites in close geographical proximity were

combined to provide sufficient data including Emu 3, SW 26 and Emu 4 which was referred to

as Emu Lower. Emu 7 and Emu 8 were also combined.

3.3.1 Metal and Arsenic Concentrations and Comparison to MPC’s

Tissue metal and metalloid concentrations were seen to be generally low when compared to

the MPC’s outlined in Table 8 with only three exceedances in copper being recorded (Appendix

1). Two liver samples of L. unicolor (from sites SW 26 and Emu 6) had concentrations

exceeding the MPC of 10 mg/kg although the muscle samples from these animals were found

to be far lower than the MPC and comparable to other L. unicolor muscle concentrations.

Copper has been shown to be high in liver tissue collected from various fish species throughout

the McArthur River in previous years and as such this result is not considered to be unusual

(Indo-Pacific Environmental 2014, 2015). As aforementioned the population structure within

Emu Creek is predominately a juvenile and sub adult population and as such only one L.

unicolor captured per site was large enough to attain a liver sample.

All three Macrobrachium analysed were seen to have higher concentrations of copper than fish


Figure 5. Percentage length frequency histogram for M. splendida collected throughout the

Emu Creek survey area in 2015.

Figure 6. Percentage length frequency histogram for N. erebi collected throughout the Emu


0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

0-9

10-1

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20-2

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30-3

9

40-4

9

50-5

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60-6

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9

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cen

tag

e

Total Length (mm)

2015 (n=133)

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5.00

10.00

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170-

179

180-

189

190-

199

200-

209

210-

219

Per

cen

tag

e

Total Length (mm)

2015 (n=34)


Figure 7. Percentage length frequency histogram for L. unicolor collected throughout the Emu


0

5

10

15

20

25

30

35

0-9

10-1

9

20-2

9

30-3

9

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170-

179

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190-

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200-

209

210-

219

Per

cen

tag

e

Total Length (mm)

2015 (n=28)


Figure 8. Species collected for metal and lead isotope analysis in the Emu Creek survey area

2015, including a) M. splendida b) N. erebi, c) L. unicolor and d) Macrobrachium spp.


Table 8. Metals analysed (and arsenic) and maximum permitted concentrations (wet weight) in

fish and crustaceans provided by Food Standards Code 1987, Food Standards Australia and

New Zealand 2000 and 2009.

FSC 1987/FSANZ 2000 FSANZ 2009

Symbol Metal Fish Crustaceans Molluscs Fish Crustaceans Molluscs

Mg Magnesium

Al Aluminium

Ca Calcium

V Vanadium

Cr Chromium

Fe Iron

Mn Manganese

Co Cobalt

Ni Nickel

Cu Copper 10 mg/kg 10 mg/kg 70 mg/kg

Zn Zinc 150 mg/kg 150 mg/kg 150 mg/kg

Ga Gallium

Mo Molybdenum

Cd Cadmium 0.2 mg/kg 0.2 mg/kg 2 mg/kg

Pb Lead 1.5 mg/kg 0.5 mg/kg 2 mg/kg

U Uranium

As Arsenic 2 mg/kg* 2 mg/kg* 1 mg/kg*

* MPC is for inorganic As only. Arsenic determined contained both organic and inorganic fractions.


with one individual exceeding the MPC. However, crustaceans contain oxygen binding copper

based proteins in the blood (haemocyanin) resulting in naturally elevated copper

concentrations (Patak et al. 1989). Concentrations of lead and zinc in Macrobrachium spp

were extremely low.

The highest lead concentration recorded during the current study was 0.17 mg/kg from a M.

splendida from SW 26. This was, however, far lower than the MPC for lead (i.e. 0.5 mg/kg). In

addition, PbIR values were far from that of the MRM ore values (see Figure 12).

3.3.2 Mean concentrations and comparison to relevant locations

The comparison of mean metal and metalloid concentrations in various tissues of M. splendida,

N. erebi, L. unicolor and Macrobrachium spp, collected from Emu Creek can be found in Table

9. In general, similar concentrations were recorded between sample sites for all species.

A comparison of the mean lead and zinc concentrations in fauna from Emu Creek to fauna from

several other sites in the McArthur River catchment are shown in Figures 9, 10 and 11. The

mean lead concentration of M. splendida from Emu Lower appeared slightly higher than that of

other sites sampled. Zinc in M. splendida appeared comparable between sites. Zinc and lead

in N. erebi also appeared consistent between all sites sampled. Leiopotherapon unicolor from

Emu Creek were shown to have lead and zinc concentrations comparable to or lower than

those reported from sites in the McArthur River.

3.3.3 Lead Isotope Ratios

PbIR values (207Pb/206Pb and 208Pb/206Pb) of tissue samples by collection site are shown

in Figure 12. For comparative purposes Figure 12 also includes PbIR values for samples

collected in 2014 from Top Crossing, SW 23 (Surprise Creek) and SW 11 (Indo-Pacific

Environmental 2015). PbIR values for samples collected throughout Emu Creek were

generally comparable between sites and to those samples collected from the McArthur River.

Figure 13 shows mean PbIR values for each site with that of Emu 8/9 samples (i.e. the most

upstream site) being closest in value to the PbIR of the ore. Of interest, mean PbIR values of

Emu Creek sites appeared to increase with increased distance upstream from the mine.

Considering the size structure of the fish captured in Emu Creek and the limited amount of

water present in Emu Creek it is unlikely that fish within the upper reaches would have spent

more of their lifecycle closer to MRM mining operations (thus would be potentially influenced)

than those fish captured from sites closer to the mine.


Table 9. Mean (±SE) metal and metalloid concentrations (mg/kg) found in various tissues of aquatic fauna at sites surveyed in Emu Creek during April 2015.

Shading indicates a value over the maximum permitted concentration.

Location Emu 9 Emu 7/8 Emu 6 Emu Lower

Mean SE Mean SE Mean SE Mean SE

L. unicolor: muscle n= 5 7 3 3

Mg 224 9.27 199 17.10 233 8.82 233 35.28

Al <1

<1

<1

1.3 0.33

Ca 772 302.6 981.4 268.3 653 265.9 1083.3 495.3

V <0.03

<0.03

<0.03

<0.03 Cr <0.03

<0.03

<0.03

<0.03

Mn 1.458 0.688 1.67 0.480 1.82 0.842 1.92 1.100

Fe 2.78 0.156 3.91 0.520 3.43 0.353 4.40 0.404

Co 0.008 0.001 0.014 0.002 0.010 0.003 0.027 0.012

Ni <0.03

0.04

<0.03

0.03 Cu 0.21 0.01 0.26 0.02 0.21 0.03 0.31 0.07

Zn 5.92 0.76 5.71 0.45 6.03 0.84 6.13 0.43

Ga <0.01

<0.01

<0.01

<0.01 As 0.024 0.004 0.028 0.004 0.012 0.004 0.018 0.006

Mo <0.05

<0.005

<0.005

<0.005 Cd 0.005 0.002 <0.001

0.016

0.002

Pb 0.005 0.002 0.005 0.000 0.005 0.000 0.008 0.001

U <0.002

<0.002

<0.002

<0.002

M. splendida: Trunk n= 8 10 10

Mg 423 13.19 415 31.14 481 7.67 Al <1

<1

<1

Ca 11875 125 11810 1168 13200 416




V <0.03

<0.03

<0.03

Cr <0.03

<0.03

<0.03

Mn 27.25 2.25 46.9 10.94 14.2 0.53 Fe 4.14 0.35 4.71 0.23 4.48 0.08 Co 0.011 0.000 0.044 0.009 0.014 0.001 Ni <0.03

<0.03

<0.03

Cu 0.376 0.011 0.541 0.018 0.379 0.019 Zn 28.5 1.3 26.6 0.7 22.3 0.6 Ga <0.01

<0.01

<0.01

As 0.026 0.002 0.065 0.007 0.014 0.001 Mo 0.007 0.001 0.006 0.000 0.005 0.000 Cd <0.001

0.001 0 <0.001

Pb 0.039 0.003 0.057 0.003 0.026 0.003 U <0.002

<0.002

<0.002

N. erebi: Muscle n= 4 10 8

Mg 318 17.50 223 7.61 310 4.23 Al <1

<1

<1

Ca 1070 89 1170 104 1178.75 53 V <0.03

<0.03

<0.04

Cr <0.03

<0.05

<0.03 Mn 2.23 0.79 6.08 1.13 3.13 0.50

Fe 2.1 0.39 6.31 0.60 3.60 0.48 Co 0.010 0.002 0.040 0.004 0.022 0.003 Ni <0.03

0.04 0.00 <0.03

Cu 0.285 0.017 0.500 0.029 0.321 0.019 Zn 6.75 0.92 7.90 0.59 7.55 0.58




Ga <0.01

<0.01

<0.01 As 0.037 0.011 0.110 0.011 0.036 0.003

Mo 0.006

0.006 0.000 <0.005 Cd 0.001

<0.001

<0.001

Pb 0.024 0.011 0.030 0.005 0.045 0.012 U <0.002

<0.002

<0.002


Figure 9. Comparison of mean Lead and Zinc concentrations (mg/kg wet weight) in trunked M.

splendida collected in Emu Creek during April 2015. Corresponding data from sampling sites

Top Crossing, SW 23 and SW 11 obtained during the 2014 McArthur river catchment survey

have been include to provide context.

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

Emu 9 Emu 7/8 Emu 6 Emu Lower Top Crossing SW 23 SW 11

mg

/ kg

wet

wei

ght

Sample Location

M. splendida Muscle: Lead

0

5

10

15

20

25

30


mg

/ kg

wet

wei

ght

Sample Location

M. splendida Muscle: Zinc


Figure 10. Comparison of mean Lead and Zinc concentrations (mg/kg wet weight) in N. erebi




0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18


mg

/ kg

wet

wei

ght

Sample Location

N. erebi Muscle: Lead

0

5

10

15

20

25

30


mg

/ kg

wet

wei

ght

Sample Location

N. erebi Muscle: Zinc


Figure 11. Comparison of mean Lead and Zinc concentrations (mg/kg wet weight) in L.unicolor




0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180


mg

/ kg

wet

wei

gh

t

Sample Location

L. unicolor Muscle: Lead

0

5

10

15

20

25

30


mg

/ kg

wet

wei

gh

t

Sample Location

L. unicolor Muscle: Zinc


Figure 12. Lead isotope ratios (207Pb/206Pb and 208Pb/206Pb) attained from fish tissues collected in Emu Creek during 2015. For comparison 2014 isotope

ratios from sample sites Top Crossing, SW 23, SW 11 have been included. Background isotope ratio (PDAC) and MRM ore ratio included for reference.

2.0200

2.0400

2.0600

2.0800

2.1000

2.1200

2.1400

2.1600

2.1800

2.2000

2.2200

0.8200 0.8400 0.8600 0.8800 0.9000 0.9200 0.9400 0.9600

208P

b/2

06P

b

207Pb/206Pb

Emu 9

Emu 7/8

Emu 6

Emu Lower

SW 11

Top Crossing

SW 23

Back ground

Ore


Figure 13. Mean lead isotope ratios (207Pb/206Pb and 208Pb/206Pb) attained from fish tissues collected in Emu Creek during 2015. For comparison 2014

isotope ratios from sample sites Top Crossing, SW 23, SW 11 have been included. Background isotope ratio (PDAC) and MRM ore ratio included for reference.

2.0400

2.0600

2.0800

2.1000

2.1200

2.1400

2.1600

2.1800

2.2000

2.2200

0.8200 0.8400 0.8600 0.8800 0.9000 0.9200 0.9400 0.9600

208P

b/20

6Pb

207Pb/206Pb

Emu 9

Emu 7/8

Emu 6

Emu Lower

Top Crossing

SW 11

SW 23

Back ground

Ore


4.0 CONCLUSIONS AND RECOMMENDATIONS

The April 2015 survey of Emu creek found the seasonal water course to comprise of a low

number of disconnected remnant pools following less than average rainfall during the 2014/15

wet season. A similar species composition and complexity to naturally vegetated sites within

nearby areas of the McArthur River and Surprise Creek was present. Results of metal,

metalloid and PbIR tissue analysis did not indicate Emu Creek fauna was being influenced by

MRM’s mining operations to any measurable extent. Results of metal, metalloid and PbIR

tissue analysis did not suggest mine derived lead was present in aquatic fauna.

It is recommended that periodic monitoring of Emu Creek be undertaken should MRM mining

practices change such that Emu Creek becomes subject to direct or indirect influence from

MRM operations. Periodic monitoring should also be implemented if changes in ground water

levels or quality are recorded between mine operations and Emu Creek.


5.0 REFERENCES

Bureau of Meteorology (2015). Climate statistics. [ONLINE] Available at:

http://www.bom.gov.au/. [Accessed 01 September 15].

Indo-Pacific Environmental (2010). Sampling procedure for metal and lead isotope analysis in

fish of the McArthur River. Prepared for McArthur River Mine. Indo-Pacific



Crustaceans and Molluscs of the McArthur River, 2013. Indo-Pacific Environmental,

Perth.


Crustaceans and Molluscs of the McArthur River, 2014. Indo-Pacific Environmental,

Perth.

FSANZ (2000). Food Standards Australia New Zealand. Standard A12. Metals and

contaminants in food, issue 45.

FSANZ ( 2009). Food Standards Australia New Zealand. Standard 1.4.1. Contaminants and

natural toxicants, issue 103.

Munksgaard, N.C., Batterham, G.J. and Parry, D. (1998). Lead isotope ratios determined by

ICP-MS: Investigation of anthropogenic lead in seawater and sediment from the Gulf of

Carpentaria, Australia. Marine Pollution Bulletin 36: 527-534.

Patak A., Baldwin J., Lake P.S. (1989). Immunochemical comparisons of haemocyanins of

Australian freshwater crayfish: Phylogenetic implications. Biochemical Systematics and

Ecology 17: 249–252.

http://www.bom.gov.au/

15006.2 Emu Creek Survey, Rev 0, September 2015 34

APPENDICES


Appendix 1. Metal and arsenic concentrations (mg/kg wet weight) and lead isotope ratios in tissues collected from Emu Creek fauna. Shading indicates

concentrations above maximum permitted values outlined by FSANZ 2000 and 2009 (see Table 8).

Mg Al Ca V Cr Mn Fe Co Ni Cu Zn Ga As Mo Cd Pb U 207Pb/206Pb 208Pb/206Pb

Sample ID Location Species Tissue Size <2 <1 <20 <0.03 <0.03 <0.04 <0.2 <0.003 <0.03 <0.03 <0.2 <0.01 <0.005 <0.005 <0.001 <0.004 <0.002

001 Emu 9 L. unicolor Muscle 148 240 <1 240 <0.03 <0.03 0.17 2.6 0.004 <0.03 0.18 4.3 <0.01 0.018 <0.005 <0.001 <0.004 <0.002 0.8957 2.1216

002 Emu 9 L. unicolor Liver as above (148) 250 <5 200 <0.15 <0.15 1.3 130 0.23 <0.15 6.6 21 <0.05 0.17 0.25 0.017 0.03 <0.01 0.9108 2.1569


004 Emu 9 L. unicolor Trunk 48,46 420 <1 12000 0.04 <0.03 30 4.5 0.016 <0.03 0.32 18 <0.01 0.035 0.006 0.003 0.048 <0.002 0.9253 2.1744

005 Emu 9 L. unicolor Trunk 51,58 470 <1 13000 0.04 <0.03 30 5.1 0.016 <0.03 0.39 24 <0.01 0.040 0.007 0.004 0.069 <0.002 0.9279 2.1805


007 Emu 9 L. unicolor Muscle 72 200 <1 1100 <0.03 <0.03 1.9 2.7 0.008 <0.03 0.19 6.1 <0.01 0.015 <0.005 0.002 0.004 <0.002 0.9157 2.1503

008 Emu 9 L. unicolor Muscle 64,62 210 <1 1800 <0.03 <0.03 3.9 3.4 0.009 <0.03 0.22 6.8 <0.01 0.021 <0.005 0.007 0.010 <0.002 0.9122 2.1664

009 Emu 9 M. splendida Trunk 55,55 430 1 12000 <0.03 <0.03 31 6.0 0.012 <0.03 0.40 34 <0.01 0.026 0.007 <0.001 0.045 <0.002 0.9262 2.1747

010 Emu 9 M. splendida Trunk 52,52 380 <1 11000 <0.03 <0.03 15 3.1 0.008 <0.03 0.32 23 <0.01 0.023 0.005 <0.001 0.029 <0.002 0.9296 2.1734

011 Emu 9 M. splendida Trunk 52,50 420 <1 12000 <0.03 <0.03 25 3.2 0.010 <0.03 0.36 26 <0.01 0.023 <0.005 <0.001 0.030 <0.002 0.9340 2.1874






017 Emu 9 N. erebi Muscle 178 330 <1 1100 <0.03 <0.03 1.6 3.2 0.008 <0.03 0.33 9.3 <0.01 0.069 <0.005 <0.001 0.017 <0.002 0.9143 2.1604

018 Emu 9 N. erebi Muscle 210 300 <1 1000 <0.03 <0.03 1.4 1.7 0.010 0.03 0.28 6.4 <0.01 0.024 <0.005 0.001 0.009 <0.002 0.9014 2.1469

019 Emu 9 N. erebi Muscle 239 360 <1 1300 <0.03 <0.03 1.3 1.4 0.007 <0.03 0.28 6.4 <0.01 0.025 0.006 <0.001 0.012 <0.002 0.9050 2.1425

049 Emu 7/8 L. unicolor Muscle 170 270 <1 160 <0.03 <0.03 0.14 2.6 0.005 <0.03 0.18 4.6 <0.01 0.013 <0.005 <0.001 <0.004 <0.002 0.8918 2.1629

050 Emu 7/8 L. unicolor Liver as above (170) 230 <2 280 0.09 <0.06 0.84 85 0.13 <0.06 2.2 17 <0.02 0.06 0.17 0.018 0.024 <0.004 0.9214 2.1797

051 Emu 7/8 L. unicolor Muscle 55,52 160 <1 1600 <0.03 <0.03 3.7 3.5 0.020 <0.03 0.33 5.0 <0.01 0.046 <0.005 <0.001 0.007 <0.002 0.9146 2.1793

052 Emu 7/8 L. unicolor Muscle 47,47,48 140 <1 740 <0.03 <0.03 1.4 3.3 0.015 <0.03 0.29 5.3 <0.01 0.031 <0.005 <0.001 <0.004 <0.002 0.9211 2.1911

064 Emu 7/8 L. unicolor Trunk 45,45,39 470 <1 14000 0.04 <0.03 38 6.6 0.033 <0.03 0.35 19 <0.01 0.070 0.006 0.015 0.094 <0.002 0.9146 2.1632

065 Emu 7/8 L. unicolor Trunk 57,45 480 2 15000 0.04 <0.03 53 6.9 0.036 <0.03 0.31 21 <0.01 0.057 0.006 0.003 0.094 <0.002 0.9240 2.1720

066 Emu 7/8 L. unicolor Muscle 66 210 <1 2100 <0.03 <0.03 2.5 6.6 0.018 <0.03 0.30 7.9 <0.01 0.035 <0.005 <0.001 0.007 <0.002 0.9075 2.1551

067 Emu 7/8 L. unicolor Muscle 66 180 <1 990 <0.03 <0.03 1.8 4.7 0.015 0.04 0.29 6.7 <0.01 0.027 <0.005 <0.001 0.005 <0.002 0.9096 2.1753

068 Emu 7/8 L. unicolor Muscle 76 190 <1 1100 <0.03 <0.03 2.0 3.9 0.019 <0.03 0.23 5.7 <0.01 0.027 <0.005 <0.001 0.006 <0.002 0.9183 2.1724

069 Emu 7/8 L. unicolor Muscle 150 240 <1 180 <0.03 <0.03 0.15 2.8 0.007 <0.03 0.19 4.8 <0.01 0.018 <0.005 <0.001 <0.004 <0.002 0.8999 2.1408

054 Emu 7/8 M. splendida Trunk 86 640 <1 21000 <0.03 <0.03 15 3.8 0.020 <0.03 0.55 24 <0.01 0.043 0.006 0.001 0.045 <0.002 0.9297 2.1730

055 Emu 7/8 M. splendida Trunk 47,48,49 330 <1 9000 <0.03 <0.03 13 4.5 0.019 <0.03 0.60 26 <0.01 0.042 <0.005 <0.001 0.059 <0.002 0.9330 2.1952

056 Emu 7/8 M. splendida Trunk 46,46,46 380 <1 11000 <0.03 <0.03 18 4.7 0.020 <0.03 0.56 25 <0.01 0.055 0.005 <0.001 0.051 <0.002 0.9398 2.1924

057 Emu 7/8 M. splendida Trunk 57,45 310 <1 8100 <0.03 <0.03 21 4.6 0.023 <0.03 0.55 26 <0.01 0.051 0.005 <0.001 0.045 <0.002 0.9395 2.1954

058 Emu 7/8 M. splendida Trunk 66,49 530 <1 15000 <0.03 <0.03 28 4.5 0.022 <0.03 0.43 26 <0.01 0.036 0.006 0.001 0.064 <0.002 0.9355 2.1894






053 Emu 7/8 Macrobrachium Muscle 26 330 <1 1800 <0.03 <0.03 2.3 0.7 0.010 <0.03 10 13 <0.01 0.12 0.005 0.009 <0.004 <0.002 0.9147 2.1737

059 Emu 7/8 N. erebi Muscle 80 230 <1 1300 <0.03 <0.03 5.1 7.0 0.045 0.03 0.48 7.2 <0.01 0.17 0.007 <0.001 0.024 <0.002 0.9126 2.1659

060 Emu 7/8 N. erebi Muscle 77 200 1 940 <0.03 <0.03 5.0 6.4 0.043 <0.03 0.42 6.2 <0.01 0.17 0.006 <0.001 0.026 <0.002 0.9095 2.1598


061 Emu 7/8 N. erebi Muscle 90 220 <1 730 <0.03 <0.03 1.4 3.1 0.019 <0.03 0.35 5.2 <0.01 0.093 <0.005 <0.001 0.012 <0.002 0.9036 2.1475



075 Emu 7/8 N. erebi Muscle 74 200 <1 830 <0.03 0.05 5.6 5.4 0.037 0.04 0.41 8.3 <0.01 0.074 <0.005 <0.001 0.021 <0.002 0.9072 2.1467

076 Emu 7/8 N. erebi Muscle 70,60 250 <1 1600 <0.03 <0.03 7.6 7.6 0.046 <0.03 0.59 7.6 <0.01 0.089 0.006 <0.001 0.035 <0.002 0.9106 2.1631

077 Emu 7/8 N. erebi Muscle 70,60 210 <1 1200 <0.03 <0.03 8.1 6.6 0.043 <0.03 0.56 7.8 <0.01 0.086 0.005 0.001 0.028 <0.002 0.9139 2.1702

078 Emu 7/8 N. erebi Muscle 62,67,59 260 <1 1400 <0.03 <0.03 11 9.3 0.053 0.04 0.56 11 <0.01 0.099 0.006 <0.001 0.034 <0.002 0.9173 2.1631

079 Emu 7/8 N. erebi Muscle 55,56,57 250 <1 1700 <0.03 <0.03 12 8.3 0.060 0.03 0.65 11 <0.01 0.11 0.007 <0.001 0.074 <0.002 0.9028 2.1509

026 Emu 6 L. unicolor Muscle 85 220 <1 680 <0.03 <0.03 2.4 2.9 0.011 <0.03 0.21 6.2 <0.01 0.011 <0.005 <0.001 0.004 <0.002 0.9133 2.1534

027 Emu 6 L. unicolor Muscle 63,63 230 <1 1100 <0.03 <0.03 2.9 4.1 0.015 <0.03 0.25 7.4 <0.01 0.020 <0.005 0.016 0.005 <0.002 0.9120 2.1488


029 Emu 6 L. unicolor Liver as above (150) 280 1 610 0.25 <0.03 2.2 85 0.098 <0.03 15 18 <0.01 0.027 0.36 0.044 0.020 <0.002 0.9165 2.1688



033 Emu 6 M. splendida Trunk 52,52 490 1 14000 <0.03 <0.03 17 4.9 0.017 <0.03 0.39 24 <0.01 0.015 0.005 <0.001 0.028 <0.002 0.9287 2.1853








030 Emu 6 Macrobrachium Muscle 19 350 <1 1300 <0.03 <0.03 2.3 0.9 0.015 <0.03 12 14 <0.01 0.086 0.008 0.007 <0.004 <0.002 0.9069 2.1717




044 Emu 6 N. erebi Muscle 180 320 <1 1300 0.04 <0.03 3.9 2.8 0.022 <0.03 0.36 8.9 <0.01 0.048 <0.005 <0.001 0.042 0.002 0.9106 2.1504




048 Emu 6 N. erebi Muscle 205 320 1 960 <0.03 <0.03 2.1 3.6 0.017 <0.03 0.41 8.7 <0.01 0.045 <0.005 <0.001 0.029 <0.002 0.8874 2.1274


020 SW26 L. unicolor Muscle 154 300 1 300 <0.03 <0.03 0.26 3.6 0.005 <0.03 0.20 6.1 <0.01 0.006 <0.005 <0.001 <0.004 <0.002 0.9024 2.1421

021 SW26 L. unicolor Liver as above (154) 220 <2 300 <0.06 <0.06 2.2 110 0.10 <0.06 53 19 <0.02 0.01 0.22 0.030 0.025 <0.004 0.9176 2.1756

022 SW26 L. unicolor Muscle 54,54 180 1 2000 <0.03 <0.03 4.0 4.9 0.030 <0.03 0.29 5.4 <0.01 0.025 <0.005 <0.001 0.012 <0.002 0.8914 2.1309

023 SW26 L. unicolor Muscle 62,50 220 2 950 <0.03 <0.03 1.5 4.7 0.046 0.03 0.43 6.9 <0.01 0.022 <0.005 0.002 0.009 <0.002 0.9084 2.1465

025 SW26 M. splendida Trunk 22,37,28,31 360 14 8900 0.12 <0.06 23 20 0.071 0.06 1.1 21 <0.02 0.02 <0.01 0.004 0.17 0.005 0.9211 2.1737

024 SW26 Macrobrachium Muscle 12 260 2 890 <0.03 <0.03 1.7 1.9 0.031 <0.03 7.5 12 <0.01 0.085 0.006 0.030 0.005 <0.002 0.9158 2.1788


APPENDIX 2 – HABITAT PREFERENCES OF THE LARGETOOTH SAWFISH (PRISTIS

PRISTIS) AND IMPLICATIONS FOR PROPOSED PIT CLOSURE.

HABITAT PREFERENCES OF THE LARGETOOTH SAWFISH (PRISTIS PRISTIS) AND

IMPLICATIONS FOR PROPOSED PIT CLOSURE

Prepared for:

McArthur River Mine

PO Box 36821

Winnellie NT 0821

Prepared by:


PO BOX 191


Phone: (08) 9444 1422

Fax: (08) 9444 1466

ACN 120 114 365

Project ID: 15006.1

Project ID 15006.1, Rev 0, August 2016 i

Document Control


A Internal Draft J. Keleher 11-05-2016 D. Thorburn 11-05-2016

B Client Draft D. Thorburn 12-05-2016 G. Taylor (MRM)

D. Moss (Metserve)

30-05-2016

0 Final to Client J. Keleher

D. Thorburn

04-08-2016

Disclaimer

This report has been prepared on behalf of and for the exclusive use of McArthur River Mine. Reproduction or use

of any part of this report (including data) is not permitted without the written permission of McArthur River Mine.

Indo-Pacific Environmental Pty Ltd however, does not warrant in any way whatsoever that the material contained

in this report is fit for use for any other purpose or by any other party than those aforementioned.

Project ID 15006.1, Rev 0, August 2016 ii

TABLE OF CONTENTS

INTRODUCTION ........................................................................................................ 1 1

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

CURRENT KNOWLEDGE .......................................................................................... 2 2

2.1 Life Cycle of Pristis pristis ........................................................................................... 2

2.2 Water Quality .............................................................................................................. 2

2.3 Habitat Preference ...................................................................................................... 3

2.4 Diet ............................................................................................................................. 4

PIT LAKE SCENARIO ................................................................................................ 5 3

3.1 Considerations for River Flow and Functionality ......................................................... 5

3.2 Considerations for Pristis pristis within the Pit Lake .................................................... 7

SUMMARY ............................................................................................................... 11 4

REFERENCES ......................................................................................................... 12 5

TABLES .................................................................................................................... 16 6

FIGURES .................................................................................................................. 18 7

Project ID 15006.1, Rev 0, August 2016 iii

TABLES

Table 1. Minimum, maximum and average values of water temperature (Temp.), pH, dissolved

oxygen (DO), conductivity (Cond.) and salinity (Sal.) at sites of capture within the McArthur

River catchment between 2007 and 2016.

FIGURES

Figure 1. Total wet season (November to March) discharge recorded at McArthur River -

M.I.M. Pump monitoring station (G9070132) and the estimated portion that be diverted into the

pit during flooding in each year.

Project ID 15006.1, Rev 0, August 2016 1

INTRODUCTION 1

1.1 Background

McArthur River Mine (MRM) is currently designing an operational closure plan. One of the

potential options includes the flooding of the pit and eventual opening of the upstream and

downstream levee walls to allow the McArthur River to flow through the pit during flow events

associated with the wet season.

Pristis pristis (Largetooth Sawfish) is known to occur in the McArthur River and has been

recorded throughout the catchment during monitoring programs run by MRM since 2006. This

includes waters adjacent MRM and in waterholes located upstream. Pristis pristis is listed as

‘Vulnerable’ under the Environment Protection and Biodiversity Act 1999 (the EPBC Act). As

such the species is afforded additional management practice to ensure the longevity of the

species in Australian water and suitable habitat.

In consideration of the scenario whereby the closure of the mine sees the pit flooded and

subsequently connected to the McArthur River, MRM requested Indo-Pacific Environmental

provide a summary of habitat preferences for P. pristis. This summary aimed to provide an

indication of design attributes that would need to be considered in the final pit design to ensure

the survival of individuals which may opportunistically swim into the pit once connected to the

McArthur River proper and potentially become isolated from the main channel when water

levels drop in the dry season.


CURRENT KNOWLEDGE 2

2.1 Life Cycle of Pristis pristis

Pristis pristis is a euryhaline elasmobranch capable of moving freely across salinity gradients to

inhabit coastal waters, estuaries and river mouths, as well as the central and upper reaches of

freshwater rivers (Thorburn et al. 2007, Whitty et al. 2008, Whitty et al. 2009). The species has

been recorded in riverine waters up to 400 km inland and up to 100 km offshore (Giles et al.

2007). Like many elasmobranchs the life history of P. pristis is characterised by slow growth,

late maturity and low fecundity (Kyne et al. 2013). As in other Pristids the reproductive cycle of

P. pristis is thought to be annual in northern Australia. The reproductive method is viviparity

(i.e. the species bears live young) with size at birth ranging from 72–90 cm TL (Peverell 2008,

Department of the Environment 2014). Young are born at the mouths of rivers and in estuaries

and then migrate up river, presumably to avoid large predators, where they spend ~4–5 years

in the freshwater reaches of rivers and floodplains before migrating to estuarine and marine

waters just before maturation at approximately 2.4 m total length (TL) for males and 2.8 m TL

for females (Thorburn et al. 2007, Peverell 2008, Whitty et al. 2008). As a result of this

ontogenetic shift in habitat utilisation juveniles and sub-adults predominantly occur in the

shallow waters of rivers and estuaries, while large mature animals tend to occur in coastal and

offshore waters (Giles et al. 2006, Kyne et al. 2013, Stevens et al. 2005, Thorburn et al. 2007,

Whitty et al. 2009)

2.2 Water Quality

Given that P. pristis is a euryhaline elasmobranch it has been recorded within a wide range of

salinities ranging from <1 ppt to 40 ppt (Thorburn 2007), however, has mainly been collected

from fresh (<1 ppt) and to a lesser extent low salinity water (<10 ppt) (Thorburn et al. 2003). In

relation to temperature Thorburn (2006) captured this species at temperatures ranging from

21.7 to 32.5 °C while the more recent work of Whitty et al. (2009) recorded this species at

temperatures ranging from 18.6 to 31.6 °C. Generally, Thorburn et al. (2003) found this species

to occur at sites that had relatively high dissolved oxygen although one individual was recorded

at a site that contained low levels of 4.3 mg/L. Thorburn et al. (2003) also found P. Pristis in

both upper freshwater and macrotidal marine environments where water clarity ranged from

250 to 5 cm, respectively, using a secchi disc.

Water quality data at sites P. Pristis has been captured within the McArthur River catchment

between 2007 and 2016 are summarised in Table 1. Results within Table 1 reflect those found

in previous studies of the species conducted elsewhere including temperature, dissolved


oxygen and salinity ranges (Thorburn et al. 2003, Thorburn 2006 and Whitty et al. 2009).

However, given the long-term nature of survey work within the McArthur River catchment the

temperature range and dissolved oxygen range for water in which P. pristis was recorded in the

McArthur River had increased.

2.3 Habitat Preference

Pristis pristis are generally restricted to shallow (<10 m) coastal, estuarine, and fresh waters

(Thorburn et al. 2003, Kyne et al. 2013). As mentioned the ontogenetic shift in habitat utilisation

results in large mature animals occupying coastal and offshore waters up to 25 m depth, while

juveniles and sub-adults predominantly occur in the shallow waters of rivers and estuaries

(Giles et al. 2006, Kyne et al. 2013, Stevens et al. 2005, Thorburn et al. 2007, Whitty et al.

2009). The species has, however, been found in deeper fresh waters including 26 m in Lake

Nicaragua (Thorson 1976, 1982).

An acoustic tracking studies conducted by Whitty et al. (2009) tracked the depths utilised by 0+

(new recruit) and 1+ (one year old) individuals in pools that ranged from 2.2 to 2.9 m in

maximum depth in estuarine waters of the Fitzroy River, Western Australia. The tag depth

sensor data demonstrated that the 0+ individuals usually remained at a water depth of 0.49 m

while the larger 1+ individuals predominantly utilised a water depth of 0.83 m. Although

individuals spent majority of their time at these depths they did occasionally navigate into

deeper waters, however, rarely exceeded a depth of two meters despite deeper habitat being

available, indicating the importance of shallow habitat. The preference of smaller individuals for

shallower habitat is likely a consequence of foraging behaviour combined with predator

avoidance strategies (Sims 2003, Wetherbee et al. 2007).

Previous work throughout northern Australia in both tidal and non-tidal river reaches has

captured this species at depths ranging from 0.7 to 6.0 m (Thorburn 2006). Depth data from

sites of capture within the McArthur River catchment between 2007 and 2016 produced similar

results with this species found to occur in pools with a maximum depth ranging from 0.6 to 6.0

m. These findings suggest that depths beyond six meters in a riverine system may not be

suitable for or utilised by P. pristis. Indeed, deep water in excess of 10 m is rare in inland

freshwaters of the McArthur River.

Previous studies have found that P. pristis is most commonly encountered over finer

substrates, ranging from silty mud to coarse sand (Peverell 2005, Thorburn et al. 2007, Whitty

et al. 2008, Whitty et al. 2009). Thorburn (2006) made further observations in terms of the

immediate habitat and found the sandy substrate from which individuals were captured had


little algae, macrophyte, or detritus present. Furthermore the bottom topography at sites of

capture was generally uniform with the deepest holes on the outer bends and sand bars on the

inner bends (Whitty et al. 2009). Captures at these sites were most often associated with the

deeper section of river adjacent a sandbar or shallow backwater (Thorburn et al. 2003).

The area required within in a riverine environment to sustain a single P. pristis is dependent on

numerous factors such as water quality, temperature, habitat availability and prey availability.

Wet season flow and duration are also key features which may affect P. pristis directly or

indirectly through, for example, altering prey availability or production and dispersal. Previous

studies on two separate isolated pools within the Fitzroy River have found P. pristis to occur at

a density of one individual per 32,899 (± 12,353) m2 and 69,328 (± 15,435) m2. These pools

had somewhat similar depth profiles with approximately 20% of the pool being <1 m, 55%

being 1-2 m, 20 % being 2-3 m, 5% > 3m and maximum depths of approximately five meters.

Within the McArthur River similar densities have been observed with one individual being

captured during a number of sampling events within Djirrinmini Waterhole which is

approximately 30,000 m2. This pool also has a similar maximum depth of six meters with

majority of the waterhole ranging in depth from 1-2 m.

2.4 Diet

Studies conducted by Peverell (2008), Thorburn (2006) and Thorburn et al. (2007)

demonstrated that P. pristis feeds on a variety of fish and crustaceans. Peverell (2008)

examined gut content and found evidence of Penaeus spp. (prawn), Plotosidae (eel tailed

catfish), Nibea squamosa (jewel fish), Rhinomugil nasutus (popeye mullet), Polydactylus

macrochir (threadfin salmon) and Macrobrachium rosenbergii (cherabin). Thorburn et al. (2007)

also examined gut content finding Neoarius graeffei (Lesser Salmon Catfish) and M.

rosenbergii to be the two dominant prey items constituting 60% and 9% of overall gut content

respectively. The other major components were fine detrital matter (13%) and insect parts

(6%) with filamentous algae, coarse detrital matter, unidentified fish, nematodes and molluscs

forming a minor component.

A stable isotope analysis conducted by Thorburn (2006) and Thorburn et al. (2014) also

indicated a broad diet in the Fitzroy River and another important food source that was

assimilated into the tissue of P. pristis was found to be Nematalosa erebi (bony bream). The

presence of relatively large amounts of silt and detrital matter, benthic invertebrates and catfish

in conjunction with dorso-ventral flattening and ventrally situated mouth strongly suggest that

this species is a benthic opportunist (Thorburn et al. 2007). Pristis pristis however has been

observed predating upon species such as Mugil cephalus (mullet) and Megalops cyprinoides


(oxeye herring) in shallow (< 30 cm) water (Department of the Environment 2014) indicating it

also actively seeks out its prey.

PIT LAKE SCENARIO 3

3.1 Considerations for River Flow and Functionality

Initial Flooding of the Pit

The current proposal would see backflow from the McArthur River used to initially fill the steep

walled void which is estimated to be at least 150 m deep. This initial filling event may present

some risk to aquatic fauna, including P. pristis, should individuals enter the pit at this early

filling stage through direct impact if carried over any significant vertical fall, from becoming

stranded on the ramp or channel connecting the pit to the main channel of the McArthur River,

or through rapid changes in water quality. In time when water levels rise it is likely that eddies

or areas of calm water will be created to the edges where flowing water enter the pit. Aquatic

fauna are known to aggregate in such areas as they seek respite from high flows whilst

migrating and foraging (Larinier 2002). Ultimately some species, including P. pristis, may be

attracted into the empty pit and become stranded in these slow water areas as water levels

recede. Measures may subsequently be required at this early stage to reduce the likelihood of

entry by fish. For example, the construction of a rock filled gabion within the remnant sections

of the McArthur River of areas between the main channel and pit may be an effective option to

prevent the entry of larger species such as P. pristis and Lates calcarifer (barramundi). These

structures have historically proven successful in preventing the dispersal of aquatic fauna

(Knight 2010).

Ongoing Implications for River Flow

Closure plans for the creation of a pit lake will also need to take into consideration what impact

the filling and recharging of the pit lake may have on the McArthur River proper. The initial

filling of the pit lake will require an estimated 260 GL of river water between the 2048/49 and

2052/53 wet seasons, a vast majority of which will come from downstream discharge.

Based on current modeling and current discharge recorded in the McArthur River (i.e. from

M.I.M. Pump monitoring station G9070132) between November and March in the 2009/2010 to

2015/2016 wet seasons the initial filling of the pit lake would have the potential to reduce

downstream discharge (i.e. below the mine site) by 0.81 – 22.22% in these years (Figure 1).

As expected higher volumes of river water would enter the pit during wet seasons with high

discharge (see for example the 2010/2011 and 2013/2014 wet seasons). Issues may arise,


however, if the river flow downstream drops to such a level that it restricts the movement of

aquatic fauna, in particular, those which rely on flood events and when high connectivity exists.

Figure 1 indicates that in years when a poor wet season was experienced a smaller portion of

water was diverted into the pit lake. However, the effects of this may be more severe. For

example, fish surveys conducted in 2015 saw a shift in species composition and a large drop in

density for a number of common species (Indo-Pacific Environmental 2015). This was largely

attributed to a short duration wet season where connectivity in the McArthur River was limited

and as such recruitment and dispersal of fish was poor. Fish sampling in the following year

(i.e. 2016), however, indicated a return to normal densities. Whilst rainfall during more recent

wet season was comparatively low the duration was longer and as a result so water river flow.

If the filling of the pit lake had occurred during the 2015/2016 wet season downstream

discharge would have been similar to that observed in 2014/2015 wet season. As such, a

similar result to that observed in 2015 may have occurred with poor recruitment of a number of

species. If recharging of the pit lake had of occurred during these wet seasons downstream

discharge would have been reduced by up to approximately 6% or as little as 0.12% based on

a recharge of 3 - 8 GL. In this situation the inverse occurs where by a high percentage of

discharge is lost to the lake during years a poor wet season is experienced. As with the initial

filling of the pit lake the effects of diverting flow, although they may be diminutive, will be more

prominent during a poor wet season.

This diversion of flow into the pit lake, particularly if a poorer wet season is experienced, will

reduce flood peaks and thus the physical habitat available as well as the connectivity between

waterholes throughout the lower reaches of the McArthur River (Ward and Stanford 1995). The

reduced flows during this time may be insufficient to adequately facilitate fish passage through

riffles and separating pools throughout the river. They may also influence the flow-related

stimuli that are important for triggering pre and post-spawning migrations and spawning itself in

a number of aquatic species that have evolved life history strategies primarily in direct

response to natural flow regimes (Bunn and Arthington 2002, Reinfelds et al. 2010).

In relation to P. pristis, this reduced flow may influence cues for the movement of the species

throughout the catchment and out of or into the McArthur River. A reduced availability of prey

items may also occur should a shift in species composition result such as that observed in

2015 (Indo-Pacific Environmental 2015). Studies of P. pristis in the Fitzroy River, Western

Australia, have found recruitment to be much higher during years of high discharge. Current

data from the McArthur River sawfish monitoring program indicates a similar relationship exists

with 0+ individuals (i.e. those recently born) not captured during years that experience lower

than average discharge. This suggests that the diverting of water from the McArthur River


when initially filling the pit lake may have substantial implications for the recruitment of P. pristis

in those years depending upon the magnitude of those wet seasons.

3.2 Considerations for Pristis pristis within the Pit Lake

Under the current option for pit closure the pit lake would be periodically connected to the

McArthur River proper during peak flows (i.e. wet season). The closure plan involves the

placement of operational waste and tailings in the final void, followed by flooding and

subsequently opening of the downstream and upstream levy’s allowing water to flow through

seasonally to prevent water stagnation. The final depth throughout majority of the pit lake is

predicted to be approximately 150 m deep. Such depths may be suited to pelagic species

which remain on the surface, however, they would not be suitable for riverine demersal species

such as P. pristis which resides and forage within the benthic zone (Whitty et al. 2009).

Although P. pristis has been found at depths of 26 m in marine waters (Thorson 1976, 1982) a

majority of the inland fish species have evolved in an environment that rarely exceeds 10

meters. As such P. pristis and its prey species are unlikely to utilise vast majority of the pit lake

waters for foraging (Haedrich 1996). Furthermore a complete lack of suitable instream structure

and thus conducive habitat suggests that aquatic fauna would largely be restricted to the top

few metres of water and which is located close to the banks. In order to support aquatic fauna

including P. pristis, sufficient habitat at suitable depths would need to be created for both P.

pristis and its prey. Outlined below are several of the major considerations for this closure

option.

Provision of Suitable Benthos

Without consideration of an engineered design the pit would create a deep vertical walled pit

lake lacking any suitable shallow bank habitat. Given the benthic nature of P. pristis a vertical

walled pit lake 150 meters deep would be inadequate for the species primarily from a lack of

shallow waters (i.e. <10m) and also from the lack of in-water habitat. Considering the riverine

habitat preferences of this species outline above, in particular depth, an area of appropriate

habitat preferably connecting the upstream and downstream entrances should be created on at

least one side of the pit lake to provide waters of suitable depth for passage. Adequate habitat

of an appropriate size should also be created for potential residence should individuals become

trapped in the pit lake after connectivity with the main channel McArthur River ceases.

In its simplest form gently sloping bank would need to be provided around the pit edges. Based

on river widths in the McArthur River and areas from which P. pristis is known it is envisaged

that this zone would need to be 30 to 50 meters wide as a minimum. This area should also


provide finer substrates ranging from silty mud to coarse sand with a majority of the area being

between 0.5 to 2.0 meters deep but up to 10 m on the inner edge. Additional topographic

features should be included to create undulation in these edge areas such as sandbars and

deep holes (<6 m) with depths gradually decreasing as they approach the shallow runs. The

creation of shallow bays in the bank would also provide sinuosity which may provide areas of

slower moving waters and within which scouring of fine sediments may be reduced. As

discussed P. pristis utilises a range of depths and foraging strategies and variability in benthic

topography would need to be provided akin to a riverine habitat.

Provision of Instream Habitat

A lack of instream habitat would need to be considered, in particular in the short term, and as

such woody debris and rock piles should be placed along the edge habitat. This would not only

provide instream habitat for P. pristis but is essential for prey species. Rehabilitation works in

the McArthur River diversion have included the placement of woody debris piles throughout the

channel. These woody debris piles have been shown to be immediately effective in providing

habitat which is favoured by aquatic fauna (see for example Indo-Pacific Environmental (2016).

This includes prey species of P. pristis such as M. rosenbergii and N. erebi which would need

to be present in sufficient numbers in the pit lake to sustain higher order species such as P.

pristis. Furthermore, the breakdown of vegetative matter in these waters is the primary energy

source for riverine food chains. While the physical placement of rock and woody debris piles

provide a temporary solution for providing aquatic fauna habitat a concurrent riparian

vegetation rehabilitation program should be considered with the view that in time woody debris

will be naturally introduced into the pit lake edges.

Prevention of Scouring and Washouts

Construction of this habitat would require engineered solutions to reduce the flow rates of water

onto the shallower bank edges. This may be in the form of rock baffles placed at the upstream

opening of the pit lake which could deflect water to prevent scouring of the finer sediments or

washouts occurring at peak flows (i.e. during the wet season).

Physicochemical Water Quality

The physiochemical ranges of water from which P. pristis has been captured during various

studies in northern Australia and from the McArthur River are outlined in Section 2.2. One of

the major considerations for connecting the pit lake to the main channel McArthur River would

be the maintenance of water quality conducive to sustaining aquatic life.


The pit lake is currently estimated to be 150 m deep which will mean a variety of temperatures

zones will exist in both the vertical aspect of the pit lake (i.e. vary with depth) and horizontally

(i.e. differences between centre and shallow edges). Given the mobility and the wide range of

temperature range P. pristis is known to tolerate individual fish will be able to seek out an area

within its preferred temperature range. However, assuming mixing of waters in the pit lack is

low at depth the temperature is likely to be far lower than the top layers and as such are likely

less favourable for the species. In the case of Lake Argyle, Western Australia, water

temperatures dropped by up to 10 degrees between the surface and 30 m depth. On this basis

a majority of the water in the pit lake in deeper sections would not represent preferable habitat

for P. pristis and it is likely individuals would utilise the top layers only.

Pristis pristis is known to tolerate a wide range of salinities as it is euryhaline. While this would

suggest the species should tolerate a wide range of conductivities (salinities) a number of its

prey are stenohaline (i.e. they cannot tolerate wide variations in salinity) and unable to tolerate

high salinities. Considering that groundwater in the area has been shown to have naturally high

conductivities and that inflow into the pit lake it is likely elevated conductivities may result.

Assuming no vertical mixing occurs water of elevated conductivity may occur in the bottom

layers of the pit lake with a freshwater lenses occurring in the upper stratum (i.e. creating a

halocline). In the event a halocline or series of haloclines exist depending upon the

conductivities present prey species and P. pristis would likely favour the top water layers and

those that are fresher.

Dissolved oxygen and pH are two water quality parameters that are prone to fluctuation and

influenced by numerous factors. Fluctuations through mixing can occur at a slow pace or be

rapid resulting in acute effects on aquatic fauna particularly when values decrease (Mathan et

al. 2010). This can also be the case for water temperature and conductivity. In the case of a

deep pit lake the factors that have the potential to influence these variables negatively are

discussed below in both the scenario that vertical mixing of water occurs and does not occur

(i.e. stratification exists).

The creation of a pit lake 150 m deep will result in large water mass that will likely stratify

during the dry season. As flows steadily decrease (and eventually cease) and ambient

temperatures increase water temperatures are likely to vary with depth potentially resulting in

the formation of an epilimnion, thermocline and hypolimnion layers (Boland and Lawton 1996,

Levy et al. 1997, Merz 2013). The epilimnion is the uppermost layer which is both well

oxygenated (due to conduction and exchange between the water surface and atmosphere) and

uniform in temperature. The thermocline is a mid-layer containing a drastic temperature

reduction and decreased oxygen content. The hypolimnion is the bottom layer characterized by


both the lowest oxygen content and the coldest water. Considering the oxygen poor nature of

the thermocline and hypolimnion layers these waters would not be considered conducive to

with the occurrence of P. pristis or prey species or maintenance of aquatic plants.

Water levels within the pit lake will subsequently need to be considered to account for potential

stratification and the habitat requirements of P. pristis. In particular, any edge habitat created

for P. pristis will need to remain within the epilimnion layer for the maintenance of oxygen in a

stratified scenario. Furthermore, any areas containing potentially acid forming minerals would

ideally remain below the epilimnion layer and preferably within the hypolimnion layer where

anoxic conditions may persist throughout the year (Fawcett and Sinclair 1996, Boland and

Padovan 2002).

In northern Australia thermal stratification was seen to occur in Lake Tinaroo (a large dam

formed from natural geomorphology) throughout most of the year with partitioning of the water

column into an oxygenated epilimnion and a deoxygenated hypolimnion layer occurring from

October to May. This stratification was disrupted when oxygenated, cool, denser inflows

occurred during the wet season and during the coolest part of the year when stratification broke

down and the entire water column mixed sufficiently to become well oxygenated throughout

(MacKinnon and Herbert 1996). In a pit lake this could potentially lead to geochemical – water

interactions between the wall rock and water-body where oxidation of sulphide minerals occurs,

consequently generating sulphuric acid. If generated in high enough quantities there may be a

shift in the pH of the water body and if sever enough could be lethal to aquatic fauna (Mathan

et al. 2010) or cause leaching of heavy metals into the environment.

The steep sides and great depth of pit lakes often results in a low surface area to depth ratio in

comparison to natural lakes where banks are generally sloping and depth is generally

shallower (Miller et al. 1996). A low surface area to depth ratio can result in an epilimnion layer

that volumetrically is a smaller fraction of the total volume (Boland and Padovan 2002). Under

such circumstances mid-year cooling can cause partial mixing of the water column resulting in

the upward migration of anoxic conditions that lower the total dissolved oxygen in the

epilimnion layer and which may be subsequently detrimental to aquatic fauna (Boland and

Padovan 2002).

Potential may also exist for the two events to occur simultaneously where mixing occurs

lowering the dissolved oxygen in the epilimnion layer while increasing oxygen in the

hypolimnion layer. In addition to reduced oxygen in surface waters the presence of oxygen at

depth may lead to oxidation of sulphide containing minerals resulting in a shift in pH and

subsequent leaching of heavy metals.


The complex interactions between the water body surface area and depth, inflows and

seasonal temperature fluctuations make it difficult to predict the degree and depth stratification

will occur and in turn which scenarios will occur. Previous studies on deep lakes in northern

Australia have found dissolved oxygen to occur at 0 % saturation at depths of 7.5 m

(MacKinnon and Herbert 1996) and 80 m (Boland and Padovan 2002) at different times of the

year, demonstrating the variability between systems. Prior to complete closure, extensive

monitoring including the profiling of water quality would need to be undertaken. Modelling

would subsequently be required to understand potential mixing scenarios to determine the

most appropriate design of the MRM pit lake.

SUMMARY 4

Considering the direct potential impacts that the initial flooding of the pit lake may have on

aquatic fauna, and in particular P. pristis, measures should be considered to exclude larger

fauna from entering the pit during this period. In addition, the effect of reducing downstream

discharge during the initial flooding of the pit void and its potential indirect effects on migration,

dispersal and recruitment, should also be considered. In particular, downstream discharge

should be maintained during this period. This will be critical if the coinciding wet seasons are

poor.

In terms of the size and depth of the potential pit lake that would result from this closure option

it is likely that low water temperatures and low oxygen levels would be present in most of the

water column beyond the epilimnion (which would represent a comparatively narrow layer).

Light penetration would also likely be restricted to the upper water layers restricting the vertical

distribution of aquatic plants which are essential in aquatic food chains. Irrespective of whether

water towards the centre of the pit lake surface was suitably oxygenated P. pristis has not

demonstrated any utilisation of open deep waters. Rather the species has demonstrated a

preference for shallow waters where is resides close to the benthos. In consideration of these

factors it is highly likely that P. pristis in this scenario would be restricted to shallower,

oxygenated and warmer waters which would occur along the edges of the pit lake, making the

vast majority of the pit unsuitable. The provision of suitable benthic conditions and in water

habitat would therefore require addressing.


REFERENCES 5

Boland, K.T. and Lawton, M.D. (1996) Seasonal water quality variations in the rum jungle

voids. In: Proceedings: Post- Mining Landform Stability and Design Workshop, 18–20

September 1996, Brisbane, Australia (eds L. C. Bell and R. W. McLean). Australian

Centre for Minesite Rehabilitation Research, Brisbane.

Boland, K.T. and Padovan, A.V. (2002). Seasonal stratification and mixing in a recently flooded

mining void in tropical Australia. Lakes and Reservoirs: Research and Management 7:

125-131.

Bunn, S. E., & Arthington, A. H. (2002). Basic principles and ecological consequences of

altered flow regimes for aquatic biodiversity. Environmental management, 30(4), 492-

507.

Department of the Environment (2014). Draft issues paper for sawfish and river sharks.

Australian Government. pp.1-57.

Fawcett, M.N.R. and Sinclair, G. (1996). Rehabilitation of final voids at Pine Creek goldfields.

In: Proceedings: Post-Mining Landform Stability and Design Workshop, 18–20

September 1996, Brisbane, Australia (Eds L. C. Bell and R. W. McLean). Australian

Centre for Mine site Rehabilitation Research, Brisbane.

Giles, J., Pillans, R., Miller, M. and Salini, J. (2007). Sawfish Catch Data in Northern Australia:

A Desktop Study. Report produced for FRDC Project 2002/064 Northern Australian

Sharks and Rays: the sustainability of target and bycatch fisheries, phase 2.

Giles, J., R.D. Pillans, M.J. Miller and J.P. and Salini (2006). Sawfish Catch Data in Northern

Australia: A Desktop Study. Internal CSIRO Report for FRDC. 2002/064:74.

Haedrich, R. L. (1996). Deep‐water fishes: evolution and adaptation in the earth's largest living

spaces. Journal of Fish Biology, 49(sA), 40-53.


Northern Territory, Early Dry Season 2015. Report to McArthur River Mine.


Northern Territory, Late Dry Season 2015 March 2016. Report to McArthur River Mine.


Knight, J. (2010) The feasibility of excluding alien redfin perch from Macquarie perch habitat in

the Hawkesbury-Nepean Catchment. Final report to the Hawkesbury-Nepean Catchment

Management Authority for Project No. HN 0507 B6D. Industry & Investment NSW –

Fisheries Final Report Series No. 121. Port Stephens, NSW, Australia. 53pp

Kyne, P.M., Carlson, J. and Smith, K. 2013. Pristis pristis. The IUCN Red List of Threatened

Species 2013: e.T18584848A18620395.

Larinier, M. (2002). Biological factors to be taken into account in the design of fishways, the

concept of obstructions to upstream migration. Bulletin Français de la Pêche et de la

Pisciculture, (364), 28-38.

Levy, D.B., Custis, K.H., Casey, W.H., and Rock, P.A. (1997). The aqueous geochemistry of

the abandoned Spenceville copper pit, Nevada County, California. Journal of

Environmental Quality 26: 233-243.

MacKinnon, M. R. and Herbert, B. W. (1996). Temperature, dissolved oxygen and stratification

in a tropical reservoir, Lake Tinaroo, northern Queensland, Australia. Marine and

Freshwater Research 47: 937-949.

Mathan, R., Kurunthachalam, S.K., and Priya, M. (2010). Alterations in plasma electrolyte

levels of a freshwater fish Cyprinus carpio exposed to acidic pH. Toxicological and

Environmental Chemistry 92: 149-157.

Merz, S.K. (2013). Characterising the Relationship Between Water Quality and Water Quantity.

Report to the Department of Sustainability, Environment, Water, Population and

Communities,

Miller, G.C., Bery Lyons. W. and Davis, A. (1996). Understanding the Water Quality of Pit

Lakes. Environmental Science and Technology 30: 118–23.

Peverell, S.C. (2005). Distribution of sawfishes (Pristidae) in the Queensland Gulf of

Carpentaria, Australia, with notes on sawfish ecology. Environmental Biology of Fishes

73: 391-402

Peverell, S.C. (2008). Sawfish (Pristidae) of the Gulf of Carpentaria, Queensland, Australia.

School of Marine Biology, James Cook University.


Reinfelds, I., Lincoln‐Smith, M., Haeusler, T., Ryan, D., & Growns, I. (2010). Hydraulic

assessment of environmental flow regimes to facilitate fish passage through natural

riffles: Shoalhaven river below Tallowa Dam, New South Wales, Australia. River

Research and Applications, 26(5), 589-604.

Sims, D.W. (2003). Tractable models for testing theories about natural strategies: foraging

behaviour and habitat selection of free-ranging sharks. Journal of Fish Biology 63: 53–

73.

Stevens, J.D., Pillans, R.D. and Salini, J. (2005). Conservation Assessment of Glyphis sp. A

(Speartooth Shark), Glyphis sp. C (Northern River Shark), Pristis microdon (Freshwater

Sawfish) and Pristis zijsron (Green Sawfish). CSIRO Marine Research. Hobart.

Thorburn, D.C. (2006). Biology, Ecology and Trophic Interactions of Elasmobranchs and other

Fishes in Riverine Waters of Northern Australia. PhD Thesis, Murdoch University, Perth,

Western Australia.

Thorburn, D.C., Morgan, D.L., Rowland, A.J., and Gill, H.S. (2007). Freshwater sawfish Pristis

microdon Latham, 1794 (Chondrichthyes : Pristidae) in the Kimberley region of Western

Australia. Zootaxa 1471: 27–41.

Thorburn, D.C, Gill, H.S. and Morgan, D.L. (2014). Predator and prey interactions of fishes of a

tropical Western Australia river revealed by dietary and stable isotope analyses. Journal

of the Royal Society of Western Australia 97:363-387.

Thorburn, DC, Peverell, S., Stevens, JD, Last, PR and Rowland, AJ (2003). Status of

Freshwater and Estuarine Elasmobranchs in Northern Australia. Report to the Natural

Heritage Trust. 79 pp.

Thorson, T.B. (1976). Observations on the reproduction of the sawfish, Pristis perotteti, in Lake

Nicaragua, with recommendations for its conservation. In: T.B. Thorson (ed.)

Investigations of the Ichthyofauna of Nicaraguan Lakes. pp. 641-650. University of

Nebraska-Lincoln.

Thorson, T.B. (1982). Life history implications of a tagging study of largetooth sawfish, Pristis

perotetti, in the Lake Nicaragua-Río San Juan System. Environmental Biology of Fishes

7: 207–228.


Ward, J. V., & Stanford, J. A. (1995). Ecological connectivity in alluvial river ecosystems and its

disruption by flow regulation. Regulated Rivers: Research & Management, 11(1), 105-

119.

Wetherbee, B.M., Gruber, S.H., and Rosa, R.S. (2007). Movement patterns of juvenile lemon

sharks Negaprion brevirostris within Atol das Rocas, Brazil: a nursery characterized by

tidal extremes. Marine Ecology Progress Series 343: 283–293.

Whitty, J.M., Morgan, D.L., Peverell, S.C., Thorburn, D.C., and Beatty, S.J. (2009). Ontogenetic

depth partitioning by juvenile freshwater sawfish (Pristis microdon: Pristidae) in a riverine

environment. Marine and Freshwater Research 60: 306-316.


TABLES 6


Table 1. Minimum, maximum and average values of water temperature (Temp.), pH, dissolved

oxygen (DO), conductivity (Cond.) and salinity (Sal.) at sites of capture within the McArthur

River catchment between 2007 and 2016.

Temp.

(°C)

pH DO

(mg/L)

Cond.

(mS)

Sal.

(ppt)

Min 18.6 7.12 3.86 0.25 0.1

Max 33.8 8.6 8.69 28.2 14.8

Average 28.1 7.94 7.09 1.5 0.78


FIGURES 7


2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016

GL

0

500

1000

1500

2000

2500

3000

River

Pit Lake

Figure 1. Total wet season (November to March) discharge recorded at McArthur River - M.I.M. Pump monitoring station (G9070132) and the estimated portion

that be diverted into the pit during flooding in each year.


APPENDIX 3 – COMBINED RESULTS OF MACROINVERTEBRATE SAMPLING PROGRAM


Appendix 3. Combined results of family-level taxa recorded during the macroinvertebrate sampling program between 2012 and 2016.

2012 2013 2014 2015 2016 Trophic Level

RIFFLE EDGE RIFFLE EDGE RIFFLE EDGE RIFFLE EDGE RIFFLE EDGE

Tubificidae 50 23 164 370 253 135 323 1082 253 379 Detritivore

Hydridae 5 6 4 81 2 64 23 26 10 19 Carnivore

Glossiphoniidae 0 0 0 0 1 0 0 0 0 0 Carnivore

Hydriidae 0 0 0 3 1 1 0 1 12 6 Multiple

Tateidae 0 0 0 0 1 0 0 2 0 6 Herbivore

Lymnaeidae 4 5 6 18 0 0 0 26 0 4 Detritivore

Thiaridae 0 0 2 2 0 2 1 0 0 0 Herbivore

Planorbidae 6 45 37 241 4 51 3 257 9 317 Herbivore

Corbiculidae 35 138 79 46 12 4 2 46 0 0 Detritivore

Ancylidae 40 8 0 0 0 9 1 6 0 3 Multiple

Ameronothridae 11 2 58 48 16 52 29 72 47 104 Carnivore

Arrenuridae 0 0 0 0 0 0 0 1 0 5 Carnivore

Eylaidae 0 6 0 1 0 0 1 1 0 0 Carnivore

Hydraphantidae 0 4 9 0 2 1 0 2 0 10 Carnivore

Hygrobatidae 242 11 228 19 123 28 357 21 372 28 Carnivore

Hydrodromidae 1 2 0 3 2 13 6 6 0 1 Carnivore

Limnesiidae 0 18 28 82 24 83 2 24 1 54 Carnivore

Oxidae 0 0 0 0 0 0 0 3 0 3 Carnivore

Unionicolidae 7 75 27 46 11 46 19 55 2 118 Carnivore

Acarina 30 13 9 1 47 21 22 3 62 19 Carnivore

Aranae 0 0 0 0 2 3 1 8 0 3 Multiple

Atyidae 1 18 0 11 0 5 3 74 1 4 Detritivore

Palaemonidae 6 3 3 6 5 5 2 8 2 0 Multiple

Parastacidae 0 0 0 0 0 0 1 1 0 0 Detritivore

Parathelphusidae 0 0 0 0 1 0 0 0 0 1 Detritivore

Isotomiae 0 0 0 0 0 2 0 2 0 4 Detritivore

Baetidae 491 1226 135 238 762 766 370 720 328 1639 Herbivore

Caenidae 732 758 522 392 1670 1452 695 593 1973 934 Multiple

Leptophlebiidae 29 8 34 7 356 10 265 12 78 7 Multiple


2012 2013 2014 2015 2016 Trophic Level


Zygoptera 2 25 2 14 0 11 0 7 0 2 Carnivore

Isostictidae 0 1 0 0 0 0 0 6 0 1 Carnivore

Coenagrionidae 0 0 0 33 4 108 0 128 0 388 Carnivore

Protoneuridae 0 22 0 26 0 14 1 26 0 8 Carnivore

Epiproctophora 31 141 0 12 20 237 16 326 41 252 Carnivore

Aeshnidae 0 1 0 0 0 0 0 4 0 1 Carnivore

Gomphiidae 10 7 3 9 12 12 10 12 11 14 Carnivore

Libellulidae 19 82 10 120 18 59 23 117 9 100 Carnivore

Lindeniidae 0 0 0 0 0 0 0 0 0 1 Carnivore

Macromiidae 0 0 0 0 0 0 0 1 0 0 Carnivore

Urothemistidae 0 0 0 0 0 0 0 0 0 2 Carnivore

Hemiptera 2 0 0 0 0 0 0 0 0 8 Unallocated

Corixidae 3 307 3 82 0 42 12 158 4 166 Carnivore

Gelastocoridae 0 0 0 0 0 0 0 1 0 0 Carnivore

Gerridae 0 15 3 6 1 8 0 5 2 8 Carnivore

Hydrometridae 0 0 0 0 0 1 0 0 0 0 Carnivore

Hebridae 0 0 2 2 0 0 0 0 0 0 Carnivore

Mesoveliidae 1 2 3 21 1 11 2 26 2 49 Carnivore

Nepidae 0 0 0 1 0 3 0 2 0 2 Carnivore

Naucoridae 0 0 1 1 0 3 0 2 0 4 Carnivore

Notonectidae 1 16 0 9 0 5 0 17 0 17 Carnivore

Ochteridae 0 0 0 0 0 1 0 1 0 0 Carnivore

Pleidae 0 9 0 19 0 42 1 20 0 25 Carnivore

Veliidae 3 14 2 19 5 27 4 97 1 51 Carnivore

Hydrophilidae 7 11 28 37 13 45 15 100 9 134 Multiple

Chrysomelidae 0 0 0 0 0 0 0 1 0 1 Herbivore

Dytiscidae 4 16 12 37 5 92 16 180 4 90 Multiple

Georissidae 0 0 0 0 0 1 0 0 0 2 Herbivore

Elmidae 152 36 371 63 327 80 465 45 344 37 Multiple

Gyrinidae 0 0 0 0 1 0 0 0 1 0 Carnivore

Hydraenidae 11 24 3 46 8 142 0 52 1 63 Herbivore

Haliplidae 0 0 0 0 0 2 0 1 0 0 Herbivore


2012 2013 2014 2015 2016 Trophic Level


Scirtidae 0 0 0 0 0 0 0 1 0 0 Detritivore

Unident. Coleop. 0 0 0 1 1 3 0 2 0 0 Multiple

Ceratopogonidae 56 137 79 222 65 190 143 1519 78 196 Multiple

Chironomidae 875 1198 1080 1050 1287 1421 1827 1936 1895 1699 Multiple

Culicidae 8 104 8 82 2 101 5 324 3 558 Detritivore

Empididae 10 2 0 1 5 2 4 0 0 0 Multiple

Dolichopodidae 0 3 2 0 14 0 4 0 1 0 Multiple

Psychodidae 0 0 0 0 1 0 0 1 0 0 Multiple

Muscidae 0 0 0 0 0 2 0 0 0 0 Carnivore

Simulliidae 101 19 90 3 302 27 218 20 334 21 Detritivore

Stratiomyidae 0 1 3 3 0 1 2 7 0 13 Detritivore

Tabanidae 13 5 20 6 50 7 25 8 61 16 Carnivore

Tipulidae 2 0 0 0 0 0 0 0 3 0 Detritivore

Trichoptera 14 39 8 38 53 137 22 33 66 46 Multiple

Hydroptilidae 35 76 33 64 113 212 33 43 51 69 Multiple

Ecnomidae 41 11 158 15 81 12 53 3 0 0 Carnivore

Hydropsychidae 656 124 1447 98 1958 286 1029 28 1638 177 Omnivore

Leptoceridae 10 169 22 151 7 126 9 182 21 205 Multiple

Philopotamidae 686 101 207 18 1002 75 131 4 118 7 Detritivore

Crambidae 15 4 37 5 32 2 38 1 17 3 Detritivore

Total 4458 5091 4982 3929 8683 6303 6234 8499 7865 8104

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