south walker creek and poitrel mines– salt assimilation ... · 1.3 study area context 1-5 1.4...

South Walker Creek and Poitrel Mines– Salt Assimilation Studies Environmental Values and Water Quality Objectives

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R.B18575.001.00.doc October 2011

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South Walker Creek and Poitrel Mines Salt

Assimilation Study – Environmental Values and Water Quality Objectives

Prepared For: BHP Mitsubishi Coal

Prepared By: BMT WBM Pty Ltd (Member of the BMT group of companies)

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BMT WBM Pty Ltd BMT WBM Pty Ltd Level 8, 200 Creek Street Brisbane 4000 Queensland Australia PO Box 203 Spring Hill 4004 Tel: +61 7 3831 6744 Fax: + 61 7 3832 3627 ABN 54 010 830 421 www.bmtwbm.com.au

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Title : South Walker Creek and Poitrel Mines Salt Assimilation Study - Preliminary Working

Environmental Values and Water Quality Objectives

Authors : Conor Jones, Brad Hiles

Synopsis : A report outlining the environmental values and water quality objectives identified for the receiving environments of South Walker Creek and Poitrel Mines for use in model the capacity of the receiving environments to assimilate salt loads under varying flow regimes, with numerical modelling and DERM methodologies.

REVISION/CHECKING HISTORY

REVISION NUMBER

DATE OF ISSUE CHECKED BY ISSUED BY

0 04/10/11 DLR

CMJ

DISTRIBUTION

DESTINATION REVISION

0 1 2 3

BHP Mitsubishi Coal

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BMT WBM Library

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CONTENTS I


CONTENTS

Contents i List of Figures ii List of Tables iii Executive Summary iv

1 INTRODUCTION 1-1

1.1 Background 1-1 1.2 Study Aims and Objectives 1-5 1.3 Study Area Context 1-5 1.4 Nomenclature and Terminology 1-6

2 DESCRIPTIONS OF RECEIVING WATERWAYS 2-1

2.1 Poitrel Mine 2-1 2.1.1 New Chum Creek 2-1

2.2 SWC Mine 2-3 2.2.1 Bee Creek 2-3 2.2.2 Carborough Creek 2-6 2.2.3 Sandy Creek 2-7 2.2.4 Walker Creek 2-9

2.3 Waterway Usage 2-11

3 SPECIES AND AREAS OF CONSERVATION SIGNIFICANCE 3-1

3.1 Riparian Vegetation 3-1 3.2 Aquatic Fauna 3-2

3.2.1 Threatened Species 3-2 3.2.2 Functional Values 3-3

3.3 Conservation Areas 3-4 3.4 Summary of Ecological Condition and Values 3-4

4 ENVIRONMENTAL VALUES AND WATER QUALITY OBJECTIVES 4-1

4.1 Background 4-1 4.2 Fitzroy Basin EVs and WQOs 4-2

LIST OF FIGURES II


4.3 Waterbody Types 4-3 4.4 Aquatic Ecosystem Condition 4-3 4.5 Draft Environmental Values and WQOs 4-5

5 REVIEW OF EXISTING SALINITIES 5-1

5.1 Data Sources 5-1 5.2 Data Analysis 5-1

5.2.1 Methods to Investigate the Effects of Recent Mine Releases 5-2 5.2.2 Methods for Calculating Upstream Salinities 5-3

5.3 Effects of Releases on Downstream ECs 5-3 5.4 Upstream Salinities 5-6

5.4.1 EC and Flow Relationships 5-6 5.4.2 Low Flow (Base Flow) Percentile Calculations 5-8

6 CONCLUSIONS 6-1

7 REFERENCES 7-1

LIST OF FIGURES

Figure 1-1 Locality plan showing study area 1-2 Figure 1-2 Poitrel Mine 1-3 Figure 1-3 South Walker Creek (SWC) Mine 1-4 Figure 2-3 Photos taken of New Chum Creek during REMP studies in July

2011 (A-E) and May 2010 (F-H). Cattle damage and erosion are evident in all photos. 2-2

Figure 2-1 Bee Creek Near the confluence of Walker Creek showing a healthy riparian zone and deep pools (A, B); straight, shallow reaches near the confluence of Sandy Creek (C) and at the highway crossing (D); scours around tree roots (E); riparian vegetation exceeding 30 m in height at the junction of Harry Brandt Creek (F); Bee Creek at Dipperu NP (G, H). 2-5

Figure 2-2 Carborough Creek near the confluence of Walker Creek showing densely grassed and forested banks; left bank (A) and right bank (B). 2-6

Figure 2-4 Grasses and Lomandra cover the left bank and large trees were abundant near the eastern sediment dam discharge onto Sandy Creek (A); looking upstream (B) and downstream (C, D). Dense grasses along the left bank downstream of the discharge point (E); looking upstream from the confluence of Sandy and Bee Creeks (F). 2-8

Figure 2-5 Walker Creek near the upstream gauging station (A, B); slumping left bank (C); scour pool at the road and rail crossing of Walker Creek (D); healthy riparian vegetation downstream of the rail crossing (E); the diverted reach of Walker Creek, looking upstream (F); active

LIST OF TABLES III


erosion at the Walker –Bee confluence (G) and the Walker- Carborough confluence (H). 2-10

Figure 2-6 Groundwater Usage 2-12 Figure 5-1 Time series for Walker Creek Showing releases from C-Dam,

natural flow events and changes in EC 5-4 Figure 5-2 Time series for Sandy Creek Showing releases from Eastern

Sediment Dam 3, natural flow events and changes in EC 5-5 Figure 5-3 Time series for New Chum Creek Showing releases from Sediment

Dam 3 and changes in EC 5-5 Figure 5-4 Time series for Bee Creek showing releases from Hail Creek (Grey

shading), rainfall, flow, and changes in EC. BCU= Bee Creek upstream, BCD= Bee Creek downstream. 5-6

Figure 5-5 Relationships between flow and EC for upstream waters at South Waker Creek Mine 5-7

Figure 5-6 Percentile calculations for EC under base-flow conditions. A red line indicates the Isaac River upper limit of 720 µS/cm, a dark blue line depicts the Connors River upper limit of 430 µS/cm and a light blue line shows the ANZEEC/ ARMCANZ (2000) limit of 250 µS/cm. 5-8

LIST OF TABLES

Table 3-1 Regional Ecosystems within the Study Area 3-1 Table 3-2 Fish species of conservation concern in the Fitzroy River catchment 3-3 Table 3-3 Summary of conservation value and conditions (good, fair and

poor) of each stream 3-5 Table 4-1 Draft WQOs for Fitzroy Basin Water bodies (DERM 2010) 4-2 Table 4-2 Draft subregional WQOs for the Protection of Aquatic Ecosystems 4-3 Table 4-3 Waterway definition and values for receiving environments within the

study area 4-5 Table 4-4 Human uses and environmental value of Poitrel and SWC Mine

receiving waters 4-6 Table 4-5 WQOs for the receiving waters Poitrel and SWC Mines2 4-7 Table 4-6 EA conditions (2010-2011) for release water and receiving water

bodies 4-8 Table 5-1 Water Quality Data Quality and Quantity 5-2

EXECUTIVE SUMMARY IV


EXECUTIVE SUMMARY

BHP Mitsubishi Coal (BMC) operates Poitrel and South Walker Creek (SWC) Mines, which are open cut mines located in the Bowen Basin area of Central Queensland. A key issue facing the mines is the management of water releases. Mine-affected waters may contain high concentrations of particulates and dissolved substances (particularly salts). Release criteria are based around the quality of the water to be released and natural flows that will dilute the release water. Waterways surrounding both mines can be classified as ephemeral streams, which flow for a short time following episodic rainfall events which are more common in the wet season.

BMT WBM was commissioned by BMC to investigate the capacity for receiving waters to assimilate salt from mine-affected water releases, in a three part study; defining environmental values and water quality objectives (WQOs) and calculating release volumes under DERM’s revised methodologies and through the use of numerical modelling. This report outlines recommended draft environmental values and WQOs for the study area.

The draft environmental values of the receiving waterways were defined on the basis of a review of existing reports, spatial data-sets, site visits, and analysis of existing monitoring data. Existing water quality data were analysed and compared to default sub-regional WQOs.

The study suggested that the conditions within Sandy and New Chum Creeks are suitable for dry discharges into these creeks (using downstream tributaries as flow triggers). Distance between the creek discharge points and the larger tributaries were small (1.5 km - 4.7 km AMTD), there were no permanent or semi-permanent pools within these reaches, other limiting human uses (such as drinking water) are not present, nor are they likely to support any fauna or flora of conservation significance. A semi-permanent pool on the Isaac River is located approximately 30 m downstream of the New Chum Creek confluence. While not located in New Chum Creek, its close proximity to the confluence means that this waterhole might be affected by releases. The details of the mixing zone will be described in the modelling report.

The distance between the C-dam discharge and the confluence of Bee Creek is approximately 8.1km AMTD. While it is unlikely that this reach contains semi-permanent or permanent pools based on aerial photography, this reach has not been ground truthed by BMT WBM.

Default WQOs (720 µS/cm) to protect aquatic ecosystems for the Isaac River should be applied to New Chum Creek and pre-mining WQOs for the Bee Creek should be used for SWC Mine tributaries (440 µS/cm). Using the prescribed DERM methodology of investigating EVs and selecting the most stringent WQO to protect these values, the EC WQO would be:

• 700 µS/cm (drinking water) at Poitrel Mine; and

• 440 µS/cm (aquatic ecosystems) at SWC Mine.

It should be noted that the DERM methodology to calculate release volumes for Zone 2 mines (SWC Mine) uses 700 µS/cm. This value would be much less restrictive to SWC Mine and would result in more opportunity to release, potentially less water storage times and less reliance on TEPs. Ultimately, liaison with DERM will be required to establish the design EC for each mine, but known environmental tolerances should be considered if the aquatic ecosystem protection WQO is deemed

EXECUTIVE SUMMARY V


too restrictive. The review by Hart et al. (1991) suggested that adverse affects to instream biota would occur if salinity were increased to ~1,500 µS/cm.

If a modified zone 3 approach is adopted, a higher design conductivity (700 µS/cm) may be able to be negotiated. Under such approach, a 0.5 scaling factor may not necessarily be required, if there are significant catchment inputs between Hail Creek Mine and SWC Mine. Such negotiations will require an understanding of catchment volumes between the two mines and will require further liaison with DERM.

INTRODUCTION 1-1


1 INTRODUCTION

1.1 Background

BHP Mitsubishi Coal (BMC) operates Poitrel and South Walker Creek (SWC) Mines, which are open cut mines located in the Bowen Basin area in central Queensland. SWC Mine is located approximately 30km west of Nebo, whilst Poitrel Mine is situated south-west of the township of Moranbah (Figure 1-1).

Like other mines in the region, a key issue is the management of water resources, both from a quality and quantity perspective. While mine-affected water is temporarily stored in various pits, dams and pipelines within the mines (Figure 1-2 and Figure 1-3), there is a need to release mine-affected waters from site to maintain appropriate storage capacities. Mine-affected waters typically contain higher concentrations of particulates and dissolved substances (particularly salts) than natural waterways that form the receiving environments of mine discharges.

All natural waterways within and adjacent to both mines are temporary or ephemeral streams, which are generally dry for most of the year and flow for a short time following rainfall. The aquatic communities that inhabit these streams have a range of adaptations to cope with seasonal variations in flow regimes as well as the associated changes in the physio-chemical properties of waters and structural habitat changes (Boulton and Lake 1992, Boulton and Suter 1986, Brooks and Boulton 1991, Jenkins and Boulton 2003, Williams 2001). Anthropogenic activities can greatly modify spatial and temporal patterns in the key processes controlling aquatic assemblages, which may result in a change to biological assemblages outside the bounds of natural variability.

BMT WBM was commissioned by BMC to investigate the capacity for receiving waters to assimilate salt from mine-affected water releases. The present study is the first of three components:

1. Defining environmental values and water quality objectives

2. Calculating release volumes under DERM’s revised “bucket” methodologies

3. Numerical modelling

These studies will provide the supporting science to accompany EA amendment application that seeks to propose site-specific water conditions for both Poitrel and SWC Mines.

This report provides an overview of the environmental values and recommended water quality objectives (WQOs) for the study area. Default sub-regional WQOs have recently been amended by DERM. The present study seeks to calculate specific WQOs where data are sufficient, and defaults to sub-regional WQOs in the absence of such data.

INTRODUCTION 1-5


1.2 Study Aims and Objectives

The overall aim of these studies is to assess Poitrel and SWC Mines’ ability to release mine-affected waters into the receiving environments under varying flow conditions, such that releases do not adversely affect the environmental values of the receiving environments. The specific objectives of the study are to:

• Identity environmental values of waterways within the receiving environments of Poitrel and SWC Mines and determine the water quality objectives to protect or enhance those environmental values;

• Define background and reference water quality conditions within and adjacent to the study area;

• Develop a receiving water quality model that will assess the likely integrated contribution of mine discharge (both Poitrel and SWC Mines) to the overall riverine flows and subsequent dispersion of the mine-affected release plumes as they drain through the receiving environments (subject to a separate report); and

• Determine potential criteria that allow Poitrel and SWC Mines to discharge mine-affected water under differing flow regimes, while meeting water quality objectives that seek to protect identified environmental values (subject to a separate report).

1.3 Study Area Context

From a geological perspective, the Bowen Basin area is mainly occupied by a series of Permian to Triassic rock formation with the majority of the sediments categorised into sandstones and shales. The coal seams, which were formed from peat swamps, occur between sandstone and shale strata (Roe et al. 1996).

Poitrel Mine is situated on the alluvial plains immediately east of the Isaac River. The study area has very gently undulating relief with slope less than 5%. The soils are predominantly deep texture-contrast (solodized solonetz and solodic) soils, with thick or thin sandy loamy surface soils (Gunn, 1967).Due to the inherent low nutrient status of soils, agricultural land use is restricted to grazing (Roe, 1996). The clayey sub-soils that characterise the study area are highly dispersive and susceptible to erosion where surface soils have been removed.

Vegetation communities within the catchment are predominantly open woodlands consisting of Acacia and/or Eucalyptus species, as typically seen in the Brigalow Belt Bioregion (Sattler and Williams 1999). Understorey vegetation is usually grassy, although a shrub layer may be present in some vegetation types. Several of these vegetation communities are of conservation significance under the Queensland Vegetation Management Act 1999 and also include the nationally Endangered Brigalow (Acacia harpophylla) community.

Vegetation clearance and disturbance have been extensive within the catchment, largely associated with agricultural activities (predominantly grazing) and mining. As a consequence, the landscape is typically composed of highly fragmented vegetation communities, and the disturbed landscape is highly susceptible to weed invasion, with the widespread occurrence of African Buffel Grass (Pennisetum ciliare) a notable issue.

INTRODUCTION 1-6


1.4 Nomenclature and Terminology

The term study area refers to waterways within the Poitrel and South Walker Creek lease boundary.

The study region encompasses the freshwater reaches of the Isaac River, Connors River, Funnel Creek and Bee Creek and tributary streams and wetlands within the study area.

The basin refers to the Fitzroy River Basin.

DESCRIPTIONS OF RECEIVING WATERWAYS 2-1


2 DESCRIPTIONS OF RECEIVING WATERWAYS

2.1 Poitrel Mine

2.1.1 New Chum Creek

The headwaters of New Chum Creek are located upstream of Millennium Mine. The creek has been diverted around Poitrel Mine. Poitrel and Millennium Mines both discharge mine-affected water into New Chum Creek. The release point for Poitrel Mine on New Chum Creek (sediment dam 3) is located approximately 4.7 km from the New Chum Creek-Isaac River confluence. Two kilometres of this reach have been surveyed previously by BMT WBM staff in 2010. During July 2011 the creek was not flowing and the largest pools identified during 2010 had been reduced to puddles.

The riparian zone of New Chum Creek was composed of open eucalypt woodland that was less dense than vegetation surrounding the main channels of the Bee Creek and the Isaac River. The riparian zone upper story of New Chum Creek was partially intact, and was comprised of trees with a maximum height of 10-15 m. Banks are very steep and approaching vertical, apart from places where the bank slumping has occurred. Cattle access tracks were frequently observed in New Chum Creek and cattle access is a major source of bank and bed disturbance. Large sections of the bank were actively eroding and lacked ground cover.

New Chum Creek would support highly simplified micro-habitats during flow periods. Aquatic micro-habitats would include sandy run habitat, the sand banks (with little to no undercutting or moderate trailing vegetation) and small pools formed by erosion under occasional tree roots. Coarse sands with a small silt fraction were the dominant substrate at New Chum Creek, apart from one of the road crossings, which has been filled with cobble and coarser material. Leaf litter and small woody debris cover was low.

During 2010 and 2011 REMP surveys a variety of fish and macrocrustacean species were collected, almost matching the richness of the main channel of the Isaac River. The following species have been collected during REMP studies: western carp gudgeon (Hypseleotris klunzingeri), spangled perch, bony bream (Nematalosa erebi), glassfish, eastern rainbowfish, purple spotted gudgeon (Morgunda adspersa), Macrobrachium, atyid shrimp and freshwater crabs.

New Chum Creek is considered to be highly disturbed condition on the basis of:

• highly modified nature of the catchment;

• the artificial nature of the habitat (due to the diversion of the creek);

• a high degree of bank erosion and channel accretion; and

• low levels of habitat diversity.



Figure 2-1 Photos taken of New Chum Creek during REMP studies in July 2011 (A-E) and May 2010 (F-H). Cattle damage and erosion are evident in all photos.



2.2 SWC Mine

2.2.1 Bee Creek

Bee Creek extends from its headwaters, located approximately 40 km north of SWC Mine, to Funnel Creek which eventually flows into the Connors River. Hail Creek and SWC Mines both discharge mine-affected into Bee Creek. Bee Creek forms the western border of Dipperu National Park (NP), approximately 18 km south-east of the SWC Mine.

Five sites on Bee Creek were inspected during July 2011, comprised of three sites downstream of SWC Mine, and two sites at Dipperu NP. The creek was flowing at the time of site inspection, and electrical conductivity (EC) values were approximately 1500 µS/cm. The most southern site at Dipperu NP had a perched pool sitting approximately 3 m higher than the water level at the time of survey. EC within this pool was approximately 400 µS/cm, which indicated that ECs during more significant flow events were much lower than the present salinity. No rainfall had been recorded1 in the wider region during the two week period leading up to the site inspection, suggesting that flows may have been driven by discharges from Hail Creek Mine (noting that SWC Mine was not discharging around the time of site inspections).

The downstream left bank of Bee Creek at Dipperu NP continued into the NP with continuous vegetation. Both banks were disturbed by cattle access tracks to a similar extent of the banks observed farther upstream, beyond the NP. .Rapid2 fish surveys were undertaken at the junction of Harry Brandt Creek near Dipperu National Park. The most abundant species were Agassizii’s glassfish (Ambassis agassizii), eastern rainbowfish (Melanotaenia splendida splendida) and spangled perch (Leiopotherapon unicolor). It is highly likely that greater survey effort would reveal more fish species.

Stream sediments were typically comprised of coarse sand, although boulders and cobble were present in places (e.g. southern site on Bee Creek at Dipperu NP), with occasional bedrock exposures. Several of the sites on Bee Creek had moderate levels of instream micro-habitat diversity, mostly in the form of log jams and scour holes around tree roots. There was little leaf litter and small woody debris, with most instream habitat consisting of tree roots and scours, large woody debris and sandy banks.

Some of the larger scour holes were up to 2 m deep in places, and may represent dry season refugia for fish and macroinvertebrates during non-flow periods. These more complex habitats typically occurred at river bends. The straighter sections of Bee Creek were relatively shallow and contained more simplified and homogenous instream run type habitats. These areas did not contain waterholes and are unlikely to support water during non-flow periods.

The riparian upper story vegetation of Bee Creek was mostly intact and composed of large eucalypts, Casuriana and occasional Callistemon. Dawson River gums and forest red gums sometimes exceeded 30 m in height. The creek banks were benched in places, and typically had a tow of unconsolidated sandy sediment. Cattle access tracks were present at several sites, and constituted

1 Bureau of Meteorology data for Moranbah Water Treatment Plant (Station 034038) 2 Sampling was comprised of seine netting (3 x 10 m shots)



the most notable form of bank disturbance. Some of the steeper banks were free of cattle access tracks and typically had a high cover of grass and shrubs.

Based on the instream and riparian habitat conditions, Bee Creek is considered to be in a slightly to moderately disturbed condition.



Figure 2-2 Bee Creek Near the confluence of Walker Creek showing a healthy riparian zone and deep pools (A, B); straight, shallow reaches near the confluence of Sandy Creek (C) and at the highway crossing (D); scours around tree roots (E); riparian vegetation exceeding 30 m

in height at the junction of Harry Brandt Creek (F); Bee Creek at Dipperu NP (G, H).



2.2.2 Carborough Creek

The upper part of the Carborough Creek catchment is located approximately 20 km west of SWC Mine. Carborough Creek flows more regularly than Walker Creek and Sandy Creek due to its larger catchment area (BMT WBM report 2). Carborough Creek joins Walker Creek at the downstream reach of the diverted reach of Walker Creek and does not receive mine-affected water from SWC Mine.

A site located at the Carborough and Walker Creek confluence was visited in July 2011, however no pools or other standing water was present. During periods of flow, the creek would support relatively simplified and homogenous aquatic habitat, similar to that found in the ‘straight’ sections of Bee Creek. Instream habitat would consist of sand banks (with limited undercutting), trailing vegetation and sandy bottom run habitat. Small amounts of leaf litter and small woody debris occurred at the stream margins, but essentially the creek was straight and had a homogenous bed.

The riparian upper story vegetation of Carborough Creek was mostly intact and composed of large eucalypts (some up to 30 m height), Casuarina and occasional Callistemon. The creek banks had a high cover of grasses and shrubs. The banks were slightly benched and the channel had a flat ‘U’ shape. Cattle access tracks occurred throughout the site, and pig tracks and wallows were also observed.

Based on the likely regularity of inundation, modification to its catchment, quality of aquatic habitat, and overall stream condition, Carborough Creek is considered to be in a moderately disturbed condition.

Figure 2-3 Carborough Creek near the confluence of Walker Creek showing densely grassed and forested banks; left bank (A) and right bank (B).



2.2.3 Sandy Creek

The headwaters of Sandy Creek begin approximately 6 km west upstream of SWC Mine. Due to the small catchment area, creek flows are relatively short-lived and small in magnitude compared to those in Carborough and Walker Creeks. SWC Mine discharges water from the eastern sediment dam into Sandy Creek via a small (first order) drainage. Sandy Creek receives mine-affected water 1.5 km upstream of its confluence with Bee Creek.

Two sites at Sandy Creek were examined in July 2011 by BMT WBM staff; at the release point and at the junction with Bee Creek. During July 2011 the creek was not flowing and the largest pools identified were up to 10 cm deep and 1.5 m in diameter. During periods of flow, the downstream reach of Sandy Creek would support a range of instream micro-habitats including small and large woody debris, tree scours and trailing vegetation. Leaf litter and small woody debris occurred around larger woody debris and tree roots. Coarse sands dominated the stream bed; however, gravel and pebble fractions were also more abundant in Sandy Creek than in Bee Creek.

The riparian upper story vegetation of Sandy Creek was mostly intact and composed of large eucalypts, Casuriana and occasional Callistemon. In the lower reaches of Sandy Creek near its confluence with Bee Creek, eucalypts occasionally exceeded 30 m in height. The upper banks were benched with a slight to moderate grade on the lower banks, becoming more vertical with proximity to Bee Creek. Cattle access tracks were less prominent in the surveyed reach of Sandy Creek than elsewhere in the study area. Banks were generally well-covered with grasses and shrubs, with and Lomandra in places.

During the July 2011 survey, pools were too small to support fish. Baseline and REMP surveys conducted by others have not investigated fish communities in Sandy Creek.

Based on the modification to its catchment, quality of aquatic habitats, and overall stream condition, Sandy Creek is considered to be in a slightly to moderately disturbed condition.



Figure 2-4 Grasses and Lomandra cover the left bank and large trees were abundant near the eastern sediment dam discharge onto Sandy Creek (A); looking upstream (B) and

downstream (C, D). Dense grasses along the left bank downstream of the discharge point (E); looking upstream from the confluence of Sandy and Bee Creeks (F).



2.2.4 Walker Creek

The headwaters of Walker Creek begin approximately 25 km north-west of SWC Mine. A reach of Walker Creek has previously been diverted to accommodate SWC Mine. The Carborough Creek joins Walker Creek downstream of this diversion. Walker Creek receives mine-affected discharge water through a small gully fed by C-dam on SWC Mine, and from F dam as well. The distance from the discharge on Walker Creek to its confluence with Bee Creek is 8.1 km.

Four sites on Walker Creek were visited in July 2011; upstream of the mine at the water quality telemetry station –at the Carborough/ SWC confluence– at the rail crossing of Walker Creek between the C-dam discharge and Bee Creek, and at the confluence between Bee Creek and Walker Creek. During July 2011 the creek was flowing at the upstream telemetry station, dry at the Carborough Creek Confluence, pooled at the rail crossing and dry at the Bee Creek confluence.

At the upstream telemetry station, aquatic habitat consisted primarily of overhanging vegetation and undercut banks. During periods of low flow, aquatic habitat at the sites downstream of the Carborough Creek confluence would consist of sand banks, large woody debris, tree roots and overhanging vegetation. Baseline and REMP surveys conducted by others have not investigated fish communities in Walker Creek. Coarse sands dominated the stream bed with occasional patches of mud where water had pooled. Trace amounts of leaf litter and small woody debris could be found at the stream margins, but the substrates were dominated by sand. Several large erosive scarps were observed at the upstream data station and at the confluence of the Carborough and the diverted section of Walker Creek.

The riparian upper story vegetation of Walker Creek is mostly intact in the non-diverted reaches of the creek and composed of large eucalypts, casurianas and occasional Callistemon, and eucalypts occasionally exceeded 30 m in height. The upper banks were benched with slight to vertical grade on the lower banks. Cattle access tracks were observed over the surveyed reach of Walker Creek. Banks had a high cover of grasses and occasional shrubs.

Based on the degree of modification to its catchment, quality of aquatic habitat, and overall stream condition, Walker Creek is considered to be in slightly to moderately disturbed condition.



Figure 2-5 Walker Creek near the upstream gauging station (A, B); slumping left bank (C); scour pool at the road and rail crossing of Walker Creek (D); healthy riparian vegetation

downstream of the rail crossing (E); the diverted reach of Walker Creek, looking upstream (F); active erosion at the Walker –Bee confluence (G) and the Walker-Carborough confluence (H).



2.3 Waterway Usage

Water uses of the study area waterways include:

• Groundwater extraction. The location of known groundwater bores are shown in Figure 2-6. While groundwater bores are present along Bee Creek downstream of SWC Mine, there are no bores mapped in the Carborough, New Chum, Sandy, or Walker Creeks. Water from these extraction sites is used for watering stock, irrigation and occasionally for human consumption.

• Stock watering. All waterways within the study area are used to water stock;

• There are anecdotal reports of non-regulated surface water extraction (illegal) for drinking throughout the region.

SPECIES AND AREAS OF CONSERVATION SIGNIFICANCE 3-1


3 SPECIES AND AREAS OF CONSERVATION SIGNIFICANCE

3.1 Riparian Vegetation

Queensland Herbarium Regional Ecosystem and Regrowth Vegetation Maps for the study area (DERM 2011b) were reviewed. Table 3-1 lists the Regional Ecosystems that occur within the study area and their status under the Vegetation Management Act 1999. Based on Table 3-1, sixteen regional ecosystems have been mapped in the study area, which includes:

• Five Endangered regional ecosystems.

• Five Of Concern regional ecosystems.

• Six Least Concern regional ecosystems.

The channels of the waterways of SWC Mine have riparian vegetation dominated by least concern RE 11.3.25 (Eucalyptus tereticornis or E. camaldulensis woodland fringing drainage lines). The floodplains outside of channel areas are composed of endangered vegetation type 11.3.1, (A. harpophylla and/or C. cristata open forest on alluvial plains) and remnant vegetation types 11.3.2 (E. populnea woodland on alluvial plains) 11.3.3, (E. coolabah woodland on alluvial plains) and 11.3.4 (E. tereticornis and/or Eucalyptus spp. tall woodland on alluvial plains).

The waterway surrounding Poitrel Mine are vegetated by a mixture of least concern vegetation type 11.5.3 (E. populnea and/or E. melanophloia and/or Corymbia clarksoniana on Cainozoic sand plains/remnant surfaces) and endangered vegetation type 11.4.9 (A. harpophylla shrubby open forest to woodland with Terminalia oblongata on Cainozoic clay plains).

Table 3-1 Regional Ecosystems within the Study Area

RE Code Short Description VMA Status

11.3.1 Acacia harpophylla and/or Casuarina cristata open forest on alluvial plains Endangered

11.3.2 Eucalyptus populnea woodland on alluvial plains Of concern

11.3.3 E. coolabah woodland on alluvial plains Of concern

11.3.4 E. tereticornis and/or Eucalyptus spp. tall woodland on alluvial plains Of concern

11.3.5 A. cambagei woodland on alluvial plains Least concern

11.3.11 Semi-evergreen vine thicket on alluvial plains Endangered

11.3.25 E. tereticornis or E. camaldulensis woodland fringing drainage lines Least concern

11.4.2 Eucalyptus spp. and/or Corymbia spp. grassy or shrubby woodland on Cainozoic clay plains

Of concern

11.4.8 E. cambageana woodland to open forest with A. harpophylla or A. Endangered



RE Code Short Description VMA Status argyrodendron on Cainozoic clay plains

11.4.9 A. harpophylla shrubby open forest to woodland with Terminalia oblongata on Cainozoic clay plains

Endangered

11.5.3 E. populnea and/or E. melanophloia and/or Corymbia clarksoniana on Cainozoic sand plains/remnant surfaces

Least concern

11.7.2 Acacia spp. woodland on lateritic duricrust. Scarp retreat zone Least concern

11.9.1 A. harpophylla-E. cambageana open forest to woodland on fine-grained sedimentary rocks

Endangered

11.9.2 E. melanophloia +/- E. orgadophila woodland on fine-grained sedimentary rocks

Least concern

11.9.9 E. crebra woodland on fine-grained sedimentary rocks Least concern

11.9.11 A. harpophylla shrubland on fine-grained sedimentary rocks Of concern

3.2 Aquatic Fauna

3.2.1 Threatened Species

There are no aquatic macroinvertebrate species listed under Commonwealth (EPBC Act 1999) or State (Nature Conservation (Wildlife) Regulation 1995, Fisheries Act 1992) legislation known or likely to occur within the study area or study area region. No IUCN listed Red List invertebrate species occur in the study area.

One listed threatened or near-threated fish species has been previously recorded in the Fitzroy River catchment: Mary River cod (Maccullochella peelii) (Table 3-3). This species is listed as Endangered under the EPBC Act, and is fully protected under the Fisheries Act 1994 (Qld). This species was translocated into the Fitzroy River catchment, although the translocation is thought to have failed (Pusey et al. 2004). The Wildlife Online (DERM 2011a) database and the EPBC Act Protected Matters Report (DSEWPAC 2011) did not identify any listed fish species within the study area.

One listed aquatic reptile has been recorded in the Fitzroy River Basin: Fitzroy River turtle (Rheodytes leukops). The species is listed as ‘Vulnerable’ under Commonwealth EBPC Act 1999, State (Queensland Nature Conservation (NCA) Act 1992) legislation, and under the IUCN Red List of Threatened Species. The distribution of this species is wholly confined to the Fitzroy River and its tributaries, occurring in permanent freshwater riverine reaches and large, isolated permanent waterholes (Cogger 2000). The study area and the Isaac River do not support the preferred habitat for this species.

Several fish species within the wider Fitzroy basin are also considered near or potentially-threatened, but are not specifically protected under legislation (Table 3-2). Two of these species occur in the



Isaac River (BMT WBM 2010; 2011) and although not recorded here to date, may occur occasionally occur in the study area.

Table 3-2 Fish species of conservation concern in the Fitzroy River catchment

Species of significance Conservation status Habitat requirements Potential locations in study area

Known/likely species

Purple-spotted Gudgeon (Mogurnda adspersa) Restricted (ASFB 2001)

Slow moving creeks among aquatic vegetation, requires hard substrate for spawning (Larson and Hoese 1996; Merrick and Schmida 1984)

Reportedly widespread but not abundant in the Fitzroy and Calliope Rivers (Pusey et al. 2004). Has been recorded in the Isaac River (BMT WBM 2011)

Leathery Grunter (Scortum hillii)

IUCN (Data Deficient) Uncertain (ASFB 2001)

Flowing, still, clear and turbid waters

Moderately abundant in the Isaac River (BMT WBM 2011).

Species not likely to occur in study area

Mary River/Murray Cod (Maccullochella peelii)

Protected – Fisheries Act Endangered – EBPC Act Critically endangered (ASFB 2001; IUCN Red List)

Slow flowing turbid waters of streams and rivers at low elevations, also fast-moving, clear, rocky upland streams

This species has been translocated into the Fitzroy River, but it is thought that translocations failed

Silver Perch (Bidyanus bidyanus)

Vulnerable (ASFB 2001; IUCN Red List)

Rivers, lakes and reservoirs, preferring areas of rapid flow

This species has been translocated into the Fitzroy River, but it is thought that translocations failed.

Southern Saratoga (Scleropages leichardti)

Lower risk – near-threatened (ASFB 2001; IUCN Red List)

Open turbid water, slow-moving rivers and pools, snags undercut banks and overhanging vegetation

Has not been recorded in the Isaac River catchment to date, due to the absence of suitable habitat for this species.

Jungle Perch (Kuhlia rupestris) Listed (QEPA 2002)

Depths to approximately 1 m, species has an extreme movement pattern

Has not been recorded in the Isaac River catchment to date, and unlikely given the absence of suitable habitat for this species.

Fitzroy River turtle (Rheodytes leukops) Vulnerable – EPBC Act

Large deep pools with areas of fast flowing water, sand, rock or gravel substrate

Permanent waterholes of the Connor’s River and Isaac River

3.2.2 Functional Values

The streams in the study area provide temporary habitat and aquatic fauna movement corridors during flow events. It is noted that streams within the study area have a relatively short length and are not known to represent a linkage with high value aquatic ecosystems in upstream areas, apart from Pink Lilly Lagoon at SWC Mine.

As flows recede, the only surface waters present in waterways are deepwater waterholes. Waterholes that persist through dry seasons may function as dry season refugia for aquatic flora and fauna. It is generally thought that the residence time of water within a pool may be an important factor in determining the species composition of the aquatic communities, with longer residence times of pools favouring the establishment of more diverse communities than more temporary pools. The deep scours at bends in Bee Creek, and the pool downstream of the New Chum Creek-Isaac River confluence are likely to approach permanency in wetter years, but probably dry out in periods of drought. Pink Lilly Lagoon is perhaps the only permanent waterhole within the study area. Thus, Sandy and Bee Creeks in periods of high flow provide linkages between Pink Lilly Lagoon and the permanent pools of the Connors River.



Increased diversity with pool persistence has been observed in waterhole along Isaac River adjacent to Poitrel Mine, which represents one of a few sites where Hyrtl’s tandan, purple-spotted gudgeon and leathery grunter have been recorded. In contrast, New Chum Creek generally has a less diverse fish community compared to the Isaac River. Because no detailed fish surveys have been conducted for the receiving waterways of SWC Mine, such comparisons cannot be drawn. However, it is likely that the deeper pools in Bee Creek support a similar fish assemblage to that observed in the Isaac River.

3.3 Conservation Areas

There are no significant conservation areas proximal to Poitrel Mine. The two key features of conservation significance within the vicinity of SWC Mine are:

• Dipperu NP is located 18 km south-east of SWC Mine. The NP has been classified as a slightly to moderately disturbed (SMD) ecosystem based on ANZECC/ARMCANZ (2000) criteria. However, its status as a National Park suggests it requires a higher level of protection than other waterways in and adjacent to the mine.

• Pink Lilly Lagoon is a wetland of regional significance (DERM 2010) and is located 270 m from the eastern sediment dam of SWC Mine. Pink Lily Lagoon is not within the downstream catchment of SWC Mine, and would only be affected by mine-affected water in the event of a catastrophic storage dam collapse.

No wetlands of national significance as listed by the Directory of Important Wetlands in Australia (DIWA) (Environment Australia 2001) occur within the waterways in or adjacent to Poitrel and SWC Mines, or the wider study region. The closest of DIWA wetlands include Fitzroy River Floodplain wetlands and Fitzroy River Delta wetlands, which are located in the lower Fitzroy River catchment near Rockhampton. Furthermore, no wetlands of international significance (also known as Ramsar sites) occur in the basin.

The Fitzroy River ultimately discharges into the Great Barrier Reef World Heritage Area (GBRWHA) and Marine Park (GBRMP). Both GBRWHA and GBRMP are protected matters of national environmental significance under the EPBC Act 1999. While saline discharges themselves are not a direct threat to the health of the GBR, saline discharges may affect downstream water quality via altering the survival of riparian vegetation and their ability to retain sediment and prevent erosion during flow periods. Discharges of turbid waters also directly affect sediment loads entering the GBR lagoon.

Other areas identified through the draft environmental values and water quality objectives for the Fitzroy Basin (DERM 2010) to have important ecological characteristics include Ungie Waterhole (60 km south-east of Poitrel Mine), Eungy (73 km south-east of Poitrel Mine, 77 km south-east of SWC Mine), Yatton waterholes (110 km south-east of Poitrel Mine, 116 km south-east of SWC Mine) and Lake Plattaway (83 km south-east of SWC and Poitrel Mines). These areas are remote from the activities of SWC and Poitrel Mines are not considered further.

3.4 Summary of Ecological Condition and Values

The conservation value and condition of each stream in the study area are colour coded in Table 3-3.



Table 3-3 Summary of conservation value and conditions (good, fair and poor) of each stream

Value Sandy Creek Carborough Creek

Walker Creek New Chum Creek Bee Ck (Walker Ck - NP reach)

Bee Creek (in Dipperu NP)

Isaac River

Conservation

areas Pink Lilly Lagoon None None None None Dipperu National

Park None

Threatened

species or

communities

Remnant RE

11.3.4

Least Concern RE

11.3.25

Remnant RE

11.3.4

Endangered RE 11.4.9,

Remnant RE

11.3.4

Remnant RE

11.3.4

Endangered RE 11.4.9,

Catchment

disturbance No physical

disturbance from

SWC and

Tootoolah Mines

No physical

disturbance from

mining, well

vegetated

Located partially

in mine, some

grazing and

mining

disturbance

Located almost

entirely in mines

Sparse

catchment

vegetation

Mines present

within catchment,

some clearing for

grazing

No physical

disturbance from

mining, well

vegetated, some

clearing for

grazing

Mines present

within catchment,

some clearing for

grazing

Hydrological

disturbance receives some

mine-affected

water

receives no mine-

affected water

Significantly

modified by

mining.

Altered flow

regimes due to

discharges

Significantly

modified by

mining.

Altered flow

regimes due to

discharges

receives some

mine-affected

water

receives several

sources of mine-

affected water

from upstream

mines

receives several

sources of mine-

affected water

Riparian zone

condition Well-vegetated

Mostly well-

vegetated

Artificial channel

(diverted) –

riparian vegetation

scarce

Artificial channel

(diverted) –

riparian vegetation

scarce

Well-vegetated Well-vegetated Mostly well-vegetated

Connectivity to

important

wetlands/streams

Provides linkage

to Pink Lilly

Lagoon

No important

upstream aquatic

habitats

No important

upstream aquatic

habitats

Located in

headwaters – no

important

upstream aquatic

habitats

Provides linkage to Pink Lilly Lagoon

Provides linkage to Pink Lilly Lagoon

Provides linkages

between semi-

permanent pools

in Isaac RIver



Bed and bank

condition

Little bank erosion

and bed accretion.

Some

Stock access

resulting in

erosion

Some bank

erosion and bed

accretion

Stock access

resulting in

erosion

Severe bank

erosion and bed

accretion

Stock access

resulting in

erosion

Severe bank

erosion and bed

accretion

Stock access

resulting in

pugging/erosion

Some bank

erosion and bed

accretion

Stock access

resulting in

erosion

Some bank

erosion and bed

accretion

Stock access

resulting in

erosion

Some bank

erosion and bed

accretion

Stock access

resulting in

erosion

Instream habitat

values

Some instream

habitat

Very short

duration flows

No refugia

Little instream

habitat

short duration

flows

No refugia

Highly simplified

habitats

short duration

flows

No refugia

Highly simplified

habitats

Very short

duration flows

No refugia

Moderate

instream habitat

medium duration

flows

partial refugia

Moderate

instream habitat

medium duration

flows

no refugia

Little instream

habitat

medium duration

flows

partial refugia

Water quality

conditions

Infrequently

affected by mine-

discharges

not affected by

mine discharges

Affected by mine

discharges

Affected by mine

discharges

Affected by mine

discharges

Affected by mine

discharges

Affected by mine

discharges

Other users Stock Access Stock Access Stock Access Stock Access Stock Access Stock Access Stock Access

ENVIRONMENTAL VALUES AND WATER QUALITY OBJECTIVES 4-1


4 ENVIRONMENTAL VALUES AND WATER QUALITY OBJECTIVES

4.1 Background

The National Water Quality Management Strategy is a management framework that seeks to improve Australia’s water quality while maintaining economic and social development. It is implemented in Queensland through the Environmental Protection (Water) Policy 2009 and the Environmental Protection Act 1994. The EPP (Water) allows the establishment of environmental values (EVs) and water quality objectives (WQOs) to support these EVs for specific waters. According to Department of Environment and Resource Management (DERM3), key steps in establishing EVs and WQOs include:

• Technical assessment of water quality and aquatic ecosystem condition, and adoption of levels of protection;

• Identification through community consultation of waterway environmental values, including levels of protection for aquatic ecosystems and human uses for waterways, along with management goals;

• Determination of water quality guidelines (adopted from local data or the Queensland Water Quality Guidelines 2009 or ANZECC/ARMCANZ 2000) and water quality objectives to enhance or protect the environmental values; and

• Consideration of the economic and social impacts of protecting environmental values (incorporating consultation with the community, including government, industry and commerce).

After determining the EVs of the waterbody, the most stringent WQO associated with the defined EVs is selected as the WQO. WQOs for many EVs such as drinking water, primary recreation, and stock watering are static values that do not change among geographic areas. However, determining the WQOs necessary for the protection of aquatic ecosystems relies on interrogating good quality reference data to determine the natural range of variability that a waterbody experiences. Protection of aquatic ecosystems is frequently the most stringent of the identified EVs, regardless of the ecosystem condition (high ecological value [HEV], slightly to moderately disturbed [SMD], or highly disturbed [HD]). HEV systems require ‘no change to natural values’, SMD systems require WQOs to fall within the 20th to 80th percentile range of reference data, and HD systems require WQOs to fall within the 10th to 90th percentile range of reference data.

With regard to Poitrel and SWC Mines, the basic procedures involved in selecting WQO’s for a water body begin with investigating whether such values already exist for the specified waterway in the QWQG. Failing this, default values for larger areas such as catchments or regions within the QWQG are used. If these are not present or deemed to be unachievable (ambient conditions exceed guidelines prior to, or upstream of the mine), site-specific reference data can be examined to determine WQOs.

The data used in to derive specific WQOs must be of sufficient quality and quantity. Sites that fit the definition of DERM “reference sites” are uncommon within the region due to intensive human modification. However, “background reference sites” are those upstream of putative impact, such as the upstream logger stations. The minimum requirements for WQO development from such data are

3 http://www.derm.qld.gov.au/register/p01551aa.pdf



18 measurements/ site over 12-14 months from 1-2 sites, or 12 measurements/ site from three or more sites over 12-24 months.

4.2 Fitzroy Basin EVs and WQOs

Draft EV’s and associated WQOs have been developed for the Fitzroy Basin through technical review and community consultation exercises (DERM 2010). The Fitzroy Basin Association (FBA) worked with DERM to draw together interested parties to identify the value and uses (including the environment) of water, at sub-catchment to whole of basin spatial scales. Through this process, draft EVs for each catchment of the Fitzroy Basin were identified, including the Isaac and Connors Rivers, which form the receiving waters of Poitrel and SWC mines.

Part of this process also involved developing sub-regional guidelines for the protection of aquatic ecosystems (see Appendix 5 of DERM 2010). This was done using 22 sites that met DERM reference site criteria (minimal disturbance to local environments and upstream catchment; no significant point source discharges nearby; sufficient data available). Trigger values from these data were based around 25th and/or 75th percentiles in place of 20th and/or 80th percentile values to account for some upstream disturbances. WQOs identified in this report are shown in, with the Connors and Isaac catchments shaded green.

Table 4-1 Draft WQOs for Fitzroy Basin Water bodies (DERM 2010)

TSS EC SO4 TN TP pH Catchment mg/L µS/cm mg/L µS/cm µS/cm Low High

QWQG 2009* 10 340/720/7601 - 500 50 6.5 8

Callide 25 1220 20 5002 502 6.5 8.5

Upper Dawson 25 360 5 350 70 6.5 8.5

Lower Dawson 10 2 3402 ID3 500 2 50 2 6.5 8.5

Comet 25 338 5 500 2 50 2 6.5 8.5

Upper Nogoa 155 275 15 1000 350 6.5 8.5 Lower Nogoa/Theresa Ck 102 340/720 2,4 ID 3 5002 50 2 6.5 8.5

Isaac 55 835 25 5002 50 2 6.5 8.5

Lower Isaac 20 400 5 450 70 6.5 8.5

Connors 15 465 10 500 75 6.5 8.5

Mackenzie 90 330 10 750 130 6.5 8.5

Fitzroy 60 445 15 500 2 502 6.5 8.5 1. All values shown are sub-regional guideline values unless otherwise stated, for low flow regimes. 2. There is insufficient data to derive a sub-regional guideline for these parameters. QWQG regional guidelines apply until sub-regional guidelines are developed. For parameters other than electrical conductivity (EC), these are QWQG Central Coast regional guidelines. For EC these are based on salinity guidelines in Appendix G of the QWQG.. 3. ID = Insufficient data to derive a sub-regional guideline. Currently, no regional guidelines apply. 4. There are two guidelines specified in this cell because the lower Nogoa/Theresa Creek catchment traverses the boundaries of two different salinity zones.

These sub-regional guidelines have been amended by DERM in July 2011 for salinity (EC), total suspended solids, sulphate, TN and TP, shown in Table 4-2.



Table 4-2 Draft subregional WQOs for the Protection of Aquatic Ecosystems

TSS EC SO4 TN TP Catchment mg/L µS/cm mg/L µS/cm µS/cm

Callide 30 1150 20 500 50

Upper Dawson 30 370 5 620 70

Lower Dawson 10 340 25 500 50

Comet 30 375 5 500 50

Upper Nogoa 165 350 15 1070 390

Lower Nogoa 10 340 25 500 50

Theresa Creek 10 720 25 500 50

Isaac 55 720 25 500 50

Lower Isaac 30 410 5 455 75

Connors 15 430 5 485 60

Mackenzie 110 310 10 775 160

Fitzroy 85 445 15 500 50

4.3 Waterbody Types

As per DERM (2010), waterways within the study area have been classified as lowland streams despite not meeting the altitude criteria of lowland streams. The stream type definitions contained in the Queensland Water Quality Guidelines (DERM 2009) and ANZECC/ARMCANZ guidelines (2000) describe upland and lowland streams:

• Upland streams: small (first, second and third order) moderate to fast flowing streams with steep gradients above 150 m. Substrate usually cobbles, gravel or sand, rarely mud; and

• Lowland streams: (third, fourth and fifth order) slow flowing and meandering streams and rivers below 150m. Gradient very slight, substrate sometimes cobble and gravel but often silt, sand and mud.

The receiving environments in the study area are represented by several ephemeral drainage systems with the largest being the Isaac River and Connor’s River. Although parts or all of these streams are found above altitudes of 150 m, stream gradients are generally very slight and substrates are dominated by coarse sands, silts and muds, with only occasional cobble or bedrock; hence, they are better described by the lowland classification.

4.4 Aquatic Ecosystem Condition

Generally the waterways within the study area and study region can be considered to represent slightly to moderately disturbed (SMD) aquatic ecosystems, based on ANZECC/ARMCANZ (2000) definitions. The SMD aquatic ecosystem condition has been selected for most of these waterways based on the overall characterisation of waters within the Central Coast Queensland Region under the QWQG (2009) guidelines (DERM 2009). Such waterways possess:



• Discontinuous shallow sandy pool habitats between flow events with various degrees of permanency. Permanent pools within the study area are limited and considered important refuge for aquatic fauna.

• Sandy run (and occasional riffle) habitats interspersed between pool habitats and cease shortly after a flow event.

• Limited riparian zones.

• Degraded banks and channel conditions resulting from limited riparian vegetation and the accumulation of coarse sand as a result of high land erosion.

Based on site assessments and the relative absence of species and areas of conservation significance (Sections 2 and 3), it is suggested that the Isaac River, Sandy, Walker, and most of Bee Creeks should be classified as SMD aquatic ecosystems as per the QWQG.

As discussed in Section 3.3, a section of Bee Creek forms the border of the Dipperu National Park. National Parks and other conservation areas are considered High Ecological Value (HEV) areas under the QWQG and require “no change to natural conditions” in terms of protection. There are limited reference data for Bee Creek at Dipperu NP that can be used to assess background water conditions at this location.

New Chum Creek has been classified as a Highly Disturbed (HD) aquatic ecosystem (see Appendix A). This designation is based on:

• Extensively modified catchment area - past land clearing has removed much of the catchment vegetation, and its catchment is now mostly located within Potirel and Millennium Mines;

• Highly altered flow regimes associated with operation of Potirel and Millennium Mines (i.e. through discharges and altered catchment flows);

• The creek has been extensively modified by river diversion works, and has poorly developed riparian vegetation;

• The stream banks and bed are in poor condition due to erosion and subsequent accretion;

• Low levels of stream health, as indicated by aquatic macroinvertebrate monitoring results.

The waterbody types and ecosystem condition descriptors and basis for determining guidelines for the study area are provided in

Table 4-3



Table 4-3 Waterway definition and values for receiving environments within the study area

Water Name Waterbody Type Aquatic Ecosystem Condition

Basis for Determining Guideline Values

SWC Mine receiving environments

Sandy Creek Lowland stream (>150 m altitude)

SMD Guidelines based on 20th and/ or 80th percentiles of reference data from good quality reference sites

Walker Creek Lowland stream (>150 m altitude)

SMD Guidelines based on 20th and/ or 80th percentiles of reference data from good quality reference sites

Bee Creek Lowland stream (>150 m altitude)

SMD Guidelines based on 20th and/ or 80th percentiles of reference data from good quality reference sites.

Bee Creek at Dipperu NP

Lowland stream (>150 m altitude)

HEV No change to natural values

Connor’s River Lowland stream SMD Guidelines based on 20th and/ or 80th percentiles of reference data from good quality reference sites

Poitrel Mine receiving environments

New Chum Creek Lowland stream (>150 m altitude)

HD Guideline locally derived and based on 10th and/ or 90th percentiles of reference data from good quality reference sites

Isaac River Lowland stream SMD Guidelines Based on 20th and/ or 80th percentiles of reference data from good quality reference sites

4.5 Draft Environmental Values and WQOs

DERM (2010) sets out Draft Environmental Values (EVs) for the Fitzroy River Basin. The DERM (2010) Draft EVs for waterways in the study area were reviewed in the present study, and refined based on more detailed site-specific information. The Refined Draft EVs established in the present study are summarised in Table 4-4.



Table 4-4 Human uses and environmental value of Poitrel and SWC Mine receiving waters

Environmental Value Bee Creek Sandy Creek Walker Creek New Chum Creek Isaac River Connor’s River

Protection of aquatic ecosystems

Suitability for crop irrigation

× × × ×

Suitability for farm supply/use

× ×

Suitability for stock water

(H)

Suitability for aquaculture

× × × × × ×

Suitability for human consumers of wild or stocked fish, shellfish or crustaceans

× × × ×

Suitability for primary contact recreation (i.e. swimming)

× × × ×

Suitability for secondary recreation (i.e. boating)

× × × ×

Suitability for visual recreation (i.e. no contact)

× × ×

Suitability for drinking water

× × ×

Suitability for industrial use (including manufacturing, plants, mining and power generation)

Protection of cultural & spiritual values, including traditional owner values of water



DERM (2010) sets out Water Quality Objectives (WQOs) for the Fitzroy River Basin, which are based on default sub-regional water quality guideline values. These default WQOs are provided for instances where there are insufficient data to determine WQOs for particular water bodies (see Section 5). The most relevant default sub-regional WQO’s for study area streams are:

• Isaac River - for New Chum Creek.

• Connors River - for the Bee, Sandy and Walker Creeks.

The most stringent WQO for each parameter are shaded in Table 4-5, based on the Draft Refined EVs shown in Table 4-4.

Table 4-5 WQOs for the receiving waters Poitrel and SWC Mines2

Draft EV TSS EC SO4 TN TP pH lower pH upper NO3 mg/L µS/cm mg/L µg/L µg/L - -

Isaac River and New Chum Creek Aquatic ecosystem 55 7201 25 500 50 6.5 8.5 Irrigation 600-4200 5000 50 6 8.5 Farm use 6 8.5 400 Stock use 0-7500 1000 4003Human consumption Primary recreation 6.5 8.5 Secondary recreation Visual appreciation Drinking water 7002 250 6.5 8.5 50 Industrial use Cultural & spiritual values

Connor’s River (Bee, Sandy and Walker Creeks) Aquatic ecosystem 15 430 5 485 60 6.5 8.5 Irrigation 600-4200 5000 50 6 8.5 Farm use 6 8.5 400 Stock use 0-7500 1000 4003Human consumption Primary recreation 6.5 8.5 Secondary recreation Visual appreciation Drinking water 7002 250 6.5 8.5 50 Industrial use Cultural & spiritual values

1 = Updated Draft Subregional WQO 2 = DERM Drinking water limit



It is noted that the salinity (EC) WQOs (Table 4-5) were lower (i.e. more stringent) than the release water conditions (1000 µS/cm) of the 2010-2011 Environmental Authority (EA) conditions for Poitrel and SWC Mines (Table 4-6). All other WQOs are equivalent to or less stringent than the EA conditions.

Table 4-6 EA conditions (2010-2011) for release water and receiving water bodies

Poitrel Mine SWC Mine Parameter EA release limit Receiving water

limits EA Receiving water

limits pH (upper) 9.0 8.0 9.0 8.0 pH (lower) 6.5 6.5 6.5 6.5 Electrical Conductivity (µS/cm)

1000 1000 1000 1000

Suspended solids(mg/L) TBD 200 TBD TBD Sulphate (mg/L) 1000 1000 1000 250

REVIEW OF EXISTING SALINITIES 5-1


5 REVIEW OF EXISTING SALINITIES

The Queensland Water Quality Guidelines (DERM 2009) allow for the development of site-specific WQOs based on local, good quality reference site data (see Section 4.1). Of particular importance in the context of the present study is the salinity or electrical conductivity of waters. Water quality data from areas outside the zone of influence of mining were investigated to assess ‘background’ EC values in the study area.

Water quality data from up- and downstream monitoring sites were also investigated during release periods to provide an initial assessment of the effects of recent releases on downstream salinity conditions.

5.1 Data Sources

‘Background’ water quality data were available from:

• SWC Mine Monitoring Data - ‘upstream’ monitoring stations located on Carborough, South Walker and Sandy Creeks. These stations are outside the zone of any mine-affected waters.

• Poitrel Mine Monitoring Data – one ’upstream’ station located on each New Chum Creek and the Isaac River. Both stations are in the zone of influence of mine-affected waters from other mines and do not constitute true background data.

• DERM Watershed Database (Bee Creek) - monitoring has been undertaken at one station on Bee Creek (Station 130411A - Smith’s Yard) between 12/05/1972 and 12/10/1985. This dataset included 18 samples under variable flow conditions (i.e. pooled water to 19.4 cumecs).

• Hail Creek Mine Monitoring Data - some post-processed EC data (a graph) was available for Bee Creek at stations located upstream and downstream of Hail Creek Mine.

• Flow data from the BoM Gauging station at the highway crossing of Bee Creek was overlain on the chart from the Hail Creek TEP..

Table 5-1 summarises data quality/quantity aspects of these data sets.

5.2 Data Analysis

All data supplied by BMC were ‘cleaned’ by removing zero flow periods and any negative recordings or prolonged periods (weeks) of identical readings. The quality and quantity of these data are described in Table 5-1. Flow data for creeks were calculated using stream heights and rating curves supplied by BMC. Rating curves were used to convert recorded heights to estimated flow in m3/ sec (cumecs). Heights were also used to calculate release volumes from sediment dam 3 at Poitrel Mine, while daily release volumes were used for C-dam and eastern sediment dam at SWC Mine.



Table 5-1 Water Quality Data Quality and Quantity

Mine Waterbody Data Type Dates Comments SWC Mine

Sandy Creek

(US)

20 min, height,

EC

16/12/2009 to

10/04/2011

Sandy Creek

(DS)

20 min, height, EC

16/12/2009 to

10/04/2011

EC data missing from 11/03/2011

Carborough

Creek (US)

20 min, height, EC

01/11/2010 to

09/04/2011

Eastern

Sediment Dam

Daily flow rate (cumec)

29/01/2011 to

10/04/2011

Release flow only

Walker Creek

(US)

20 min, height, EC

20/12/2009 to

10/04/2011

Data unreliable before November 2010

Walker Creek

(DS)

20 min, height, EC

16/12/09 to

10/04/2011

Data unreliable before November 2010. EC

data ceases after 10/03/11

C- Dam Daily flow rate (cumec)

01/12/2010 to

03/02/2011

Release data only

Bee Creek Graph from Hail

Creek TEP

29/01/2011 to

20/06/2011

Supplied graphic only, no raw data

Bee Creek Continuous flow

(heights)

29/01/2011 to

20/06/2011

Poitrel Mine

New Chum

Creek (US) 20 min, height,

EC

03/09/2010 to

31/03/2011

Flow data present between 23/11/2010

onwards. EC data considered unreliable

outside of 27/11/2010 to 01/01/2011

New Chum

Creek (DS) 20 min, height,

EC

09/10/2010 to

31/03/2011

EC data considered unreliable outside of

27/11/2010 to 01/01/2011. Flow data

several orders of magnitude too high.

Sediment Dam

3 20 min, height

19/11/2010 to

31/03/2011

Release flow only

Isaac River

(US)

20 min, height,

EC

09/09/2010 to

31/03/2011

Isaac River

(DS)

20 min, height,

EC

09/09/2010 to

31/03/2011

EC data of limited duration

5.2.1 Methods to Investigate the Effects of Recent Mine Releases

EC, flow, and discharge volumes were graphed over recent release periods for both Poitrel and SWC Mines, to investigate the effects of releases on downstream conductivities. Flow data derived from Bee Creek at the BoM gauging station (534027) was overlaid on the supplied time series chart from Hail Creek Mine.



5.2.2 Methods for Calculating Upstream Salinities

The QWQG require WQOs to be calculated based on low-flow conditions. DERM has advised that low-flow conditions often cease when flows where ECs drop below 250 µS/cm. This generally coincides with the 95th percentile flow rate for the creeks in the study area.

Therefore, upstream ECs were calculated for ‘low flow’ periods using fitted relationships between EC and flow. Once these relationships were established, low-flow data was sorted from the entire dataset using the flow rate that corresponded to 250 µS/cm. For Sandy Creek, 175 µS/cm was used, as this was the point at which the curve flattened, and corresponded well to the 95th percentile flow.

Note: as outlined in Section 4.5, in the absence of appropriate background data for New Chum Creek, default subregional WQOs for the Isaac River were adopted.

5.3 Effects of Releases on Downstream ECs

C-dam water releases have historically had little effect on the downstream EC of Walker Creek (Figure 5-1). Some spiking in EC was observed downstream after releases in January and February 2011, but other release periods did not result in any observed changes in EC. Releases which had little effect on EC tended to coincide with larger natural flow events, such that releases were effectively diluted.

The effects of eastern sediment dam releases on Sandy Creek EC were much more pronounced than what was observed for Walker Creek, but EC remained below 1000 µS/cm in the immediate receiving environment. For the period of time where upstream and downstream EC values were both present, natural flow events in Sandy Creek kept up- and downstream salinities very similar; however, downstream conductivities were substantially higher after upstream flow ceased.

The data from the New Chum Creek appears largely unreliable and the effects of water release on downstream conductivities are difficult to discern.

TEP data from Hail Creek Mine shows the patterns in EC in relation to rainfall and release periods (Figure 5-4). This figure shows that water upstream of Hail Creek comes in at a higher conductivity than waters downstream of the mine. That is, mine releases from Hail Creek Mine over this period, possibly in combination with input from other tributaries acted to reduce salinities downstream of the mine. It also shows that EC downstream on Hail Creek Mine (upstream of South Walker Mine) is often above 1000 µS/cm and frequently above 2000 µS/cm.



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Figure 5-1 Time series for Walker Creek Showing releases from C-Dam, natural flow events and changes in EC



Figure 5-2 Time series for Sandy Creek Showing releases from Eastern Sediment Dam 3, natural flow events and changes in EC

Figure 5-3 Time series for New Chum Creek Showing releases from Sediment Dam 3 and changes in EC



Figure 5-4 Time series for Bee Creek showing releases from Hail Creek (Grey shading), rainfall, flow, and changes in EC. BCU= Bee Creek upstream, BCD= Bee Creek downstream.

5.4 Upstream Salinities

5.4.1 EC and Flow Relationships

The relationships between flow and EC for upstream waters of SWC Mine are shown in Figure 5-5.



Sandy Creek Upstream

Walker Creek Upstream

Carborough Creek Upstream

Figure 5-5 Relationships between flow and EC for upstream waters at South Walker Creek Mine



5.4.2 Low Flow (Base Flow) Percentile Calculations

For Sandy Creek, the low-flow limit was estimated to occur at 1.07 cumecs and 175 µS/cm, less than the 250 µS/cm ‘guideline’. The EC limit was lower For Walker and Carborough Creeks upstream of SWC Mine; EC values of 250 µS/cm were estimated to occur at 21 and 23 cumecs, respectively. These were roughly equivalent to 95th percentile flows. Based on these event flow triggers, percentile calculations shown in Figure 5-6 were made (20th, 50th, and 75thpercentiles, min and max).

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Figure 5-6 Percentile calculations for EC under base-flow conditions. A red line indicates the Isaac River upper limit of 720 µS/cm, a dark blue line depicts the Connors River upper limit

of 430 µS/cm and a light blue line shows the ANZEEC/ ARMCANZ (2000) limit of 250 µS/cm.

Figure 5-6 shows that median and 75th percentile values the upstream waterways of Poitrel Mine frequently exceed the Isaac River upper salinity WQO. However, it should be noted that “upstream” stations for both the Isaac River and New Chum Creek receive mine-affected water from other sources and are not true reference sites.



For Bee Creek, the only reference data available is from a closed historic DERM station. The 75th percentile from this data set (440 µS/cm) is similar to the default value for the Connors River (430 µS/cm), therefore, the historic Bee Creek value seems appropriate for aquatic ecosystem protection using QWQG methods. However, Figure 5-4 shows that this WQO is often exceeded at Bee Creek both up- and downstream of Hail Creek Mine. Without access to raw upstream data, we are unable to make recommendations about appropriate WQOs for Bee Creek with modern data. Thus, the historic 440 µS/cm value has been adopted, but this may be inappropriate given upstream conductivities observed over the last two years.

With regard to Bee Creek at Dipperu NP, the closest “reference site” data available is the historic DERM data. In order to preserve HEV conditions WQO’s to meet “no environmental change” are required. Given the existing human disturbances to the NP, including vegetation modification and stock access, it seems unreasonable and unachievable to adopt “pristine” WQOs based on historic data. Initial advice from DERM regarding appropriate design conductivities for this reach of Bee Creek suggests that the default values will be required in the absence of suitable data.

The 75th percentile values for Carborough, Sandy, and Walker Creeks based on upstream data are 212, 797, and 516 µS/cm, respectively. These values represent WQOs to protect aquatic ecosystems, using QWQG methodologies. However, because each of these tributaries flow into Bee Creek, the more conservative Bee Creek value is probably more appropriate for use in numerical modelling, given the quality of the data and the complexities of flow through the site.

In the absence of appropriate reference data (see Section 4.1) for New Chum Creeks, updated sub-regional water guidelines outlined in QWQG (DERM 2010) should be adopted as the aquatic ecosystem protection WQOs, as per QWQG methods. New Chum Creek WQOs were adopted as per the Isaac River because its EVs were similar to or less restrictive than that of the Isaac River.

CONCLUSIONS 6-1


6 CONCLUSIONS

Informal discussions with DERM suggest that it may be permissible to discharge mine-affected water <3,500 µS/cm into small ephemeral creeks such as New Chum, Sandy or Walker Creeks if:

• medium flow triggers on the larger downstream tributary are adopted using the DERM’s revised methodology,

• the creeks do not contain significant dry season refugia (pools approaching permanency),

• the creeks do not support fauna, flora or habitats with significant conservation status,

• such discharges will not affect other human uses such as drinking water or agriculture,

• the distance between the discharge point and the confluence with the larger downstream tributary is short (<5km).

Our survey suggests that Sandy and New Chum Creeks meet these criteria. The distance between the Sandy Creek discharge point and Bee Creek is approximately 1.5 km AMTD, while the distance between sediment dam 3 and the Isaac River is 4.7 km AMTD. Given the short distance between the discharge points on Sandy and New Chum Creeks and the larger tributaries, their lack of semi- or permanent pools, absence of other limiting human uses (such as drinking water) and lack of fauna and flora of conservation significance, dry discharge into these creeks, using flow gauging in Bee Creek and the Isaac River may be possible.

With regard to New Chum Creek, there is one semi-permanent pool on the Isaac River, approximately 30 m downstream of the New Chum Creek confluence. While not located in New Chum Creek, its close proximity to the confluence means that this waterhole may be potentially affected by releases. The details of the mixing zone will be described in the modelling report. No such pools are present between the Sandy Creek release point and Bee Creek.

The distance between the C-dam discharge and the confluence of Bee Creek is approximately 8.1km AMTD. While it is unlikely that this reach contains semi-permanent or permanent pools based on aerial photography, this reach has not been ground truthed by BMT WBM.

Looking simply at the distributions of water quality data, default WQOs to protect aquatic ecosystems for the Isaac River should be applied to New Chum Creek (720 µS/cm) and pre-mining WQOs for the Bee Creek should be used for SWC Mine tributaries (440 µS/cm). Using the prescribed DERM methodology of investigating EVs and selecting the most stringent WQO to protect these values, the EC WQO would be:

• 700 µS/cm (drinking water) at Poitrel Mine, and

• 440 µS/cm (aquatic ecosystems) at SWC Mine

It should be noted that the DERM methodology to calculate release volumes for Zone 2 mines (SWC Mine) uses 700 µS/cm as the design EC to protect drinking water values. This value of 700 µS/cm would be much less restrictive to SWC Mine and would result in more opportunity to release, potentially less water storage times and less reliance on TEPs. Ultimately, liaison with DERM will be required to establish the design EC for each mine, but known environmental tolerances should be considered if the aquatic ecosystem protection WQO is deemed too restrictive. The review by Hart et

CONCLUSIONS 6-2


al. (1991) suggested that adverse affects to instream biota would occur in Australian rivers, streams and wetlands if salinity were increased to ~1,500 µS/cm.

If a modified zone 3 approach is adopted, a higher design conductivity (700 µS/cm) may be able to be negotiated. Under such approach, a 0.5 scaling factor may not necessarily be required, if there are significant catchment inputs between Hail Creek Mine and SWC Mine. Such negotiations will require an understanding of catchment volumes between the two mines and will require further liaison with DERM.

If flow triggers on Walker Creek are to be used, the upstream WQO of 516 µS/cm should not be used instead of the default Connors River value due to the limited duration over which this data was acquired.

REFERENCES 7-1


7 REFERENCES

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Boulton A.J. & Suter P.J. (1986) Ecology of temporary streams – an Australian perspective. In: Limnology in Australia (Eds P. De Deckker & W.D. Williams), pp. 313–327. CSIRO / Dr W. Junk, Melbourne / Dordrecht.

Boulton A.J. (2003) Parallels and contrasts in the effects of drought on stream macroinvertebrate assemblages. Freshwater Biology: 48 (1): 1173-1185

Boulton A.J. and Lake, P.S. (2003) The ecology of two intermittent streams in Victoria, Australia. Freshwater Biology: 27 (1): 99-121

Brooks, S.S. & Boulton, A.J. 1991. Recolonization dynamics of benthic macroinvertebrates after artificial and natural disturbances in an Australian temporary stream. Australian Journal of Marine and Freshwater Research. 42:295-308.

Cann, J. (1998). Australian Freshwater Turtles. Singapore: Beaumont Publishing Pty Ltd.

Cogger, H.G. (2000). Reptiles and Amphibians of Australia - 6th edition. Sydney, NSW: Reed New Holland.

DERM (2009) Queensland Water Quality Guidelines, Version 3. ISBN 978-0-9806986-0-2

DERM (2010) Establishing environmental values, water quality guidelines and water quality objectives for Fitzroy Basin waters. Prepared in association with the Fitzroy Basin Association, December 2010. Available online: http://www.derm.qld.gov.au/environmental_management/water/environmental_values_environmental_protection_water_policy/pdf/draft-values-objectives-fitzroy-a.pdf

DERM (2011a) Wildlife Online. The Department of Environment and Resource Management, Queensland, Data extracted 28 February 2011

DERM (2011b) Regional Ecosystem Maps. The Department of Environment and Resource Management, Queensland, Data extracted 28 August 2011. Available online: http://www.derm.qld.gov.au/wildlife-ecosystems/biodiversity/regional_ecosystems/introduction_and_status/regional_ecosystem_maps/index.php#coord

DSEWPAC (2011) Protected Matter Search Tool (on line database), ttp://www.environment.gov.au/epbc/pmst/index.html , Last accessed 21 February 2011.

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Dunlop, J. E., G. McGregor, N. Horrigan (2005). “ Potential impacts of salinity and turbidity in riverine ecosystems – Characterisation of impacts and a discussion of regional target setting for riverine ecosystems in Queensland” Report prepared for the National Action Plan for Salinity and Water Quality (NAPSWQ), Queensland, 64pp.

Dunlop, J. E., N. Horrigan, et al. (2008). "Effects of spatial variation on salinity tolerance of macroinvertebrates in Eastern Austaria and implications for ecosystem protection trigger values." Environmental Pollution 151: 621-630.

Environment Australia (2001) A Directory of Important Wetlands in Australia. Canberra, Australian Government Press.

Hart, B. T., Bailey, P., Edwards, R., Hortle, K., James, K., McMahon, A., Meredith, C., and Swadling, K. (1991). A review of the salt sensitivity of the Australian freshwater biota. Hydrobiologia 210, 105-144.

Gunn, R. H. (1967). Soils of the Isaac-Comet area. Lands of the Isaac-Comet Area, Queensland. Melbourne, CSIRO. Land Research Series 19: 89-128.

IUCN (2010). IUCN Red List of Threatened Species. Version 2010.4. <www.iucnredlist.org>. Downloaded on 12 April 2011.

Jenkins, K. M. and Boulton A.J. (2003) Connectivity in a dryland river: short-term aquatic macroinvertebrate recruitment following floodplain inundation. Ecology: 84: 2708-2723

Larson, H. K. and Hoese, D. F. (1996) ‘Gobies’. In Freshwater Fishes of South-Eastern Australia. (ed Robert McDowall). Reed Books: Chatswood (NSW). 220–228.

Merrick, J. R. and Schmida, G. R. (1984) Australian Freshwater Fishes - Biology and Management. Griffin, Netley (South Australia). 409 pp.

Pusey, B., M. Kennard, et al. (2004). Freshwater Fishes of North-Eastern Australia. Collingwood, CSIRO Publishing.

Roe, P. A., D. R. Mulligan, et al. (1996). Environmental management of coal mines in the Bowen Basin, Central Queensland. Environmental Management in the Australoian Minerals and Energy Industries. D. R. Mulligan. Sydney, University of New South Wales Press: 290-315.

Sattler, P. S. and R. D. Williams, Eds. (1999). The Conservation Status of Queensland's Bioregional Ecosystems. Brisbane, Environmental Protection Agency.

Williams, D. D. (2001). The Ecology of Temporary Waters. Caldwell, The Blackburn Press.

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