APPENDIX 4-7 TSF Design Report

APPENDIX 4-7

TSF Design Report

https://hastingstechmetals.com/

The contents of this document are proprietary and produced for the exclusive benefit of Hastings Technology Metals Limited. No part of this document may be reproduced, stored in a retrieval system, or transmitted, in any form or by any

means, without the prior written approval of Hastings Technology Metals Limited. All copies viewed outside Hastings EDMS are uncontrolled.

YANGIBANA RARE EARTHS PROJECT

TSF DESIGN DEVELOPMENT – PRE-CONSTRUCTION

REPORT

DOCUMENT NO.: YGB-31-100-ENG-CIV-REP-0001

REVISION DATE ISSUED FOR PREPARED BY REVIEWED BY APPROVED BY

A 15/03/19 Draft Issued for Review B. Haslow GHD Pty Ltd

B. Haslow GHD Pty Ltd

00 01/04/19 Issued for Use B. Haslow GHD Pty Ltd


01 05/06/19 Re-Issued for Use B. Haslow GHD Pty Ltd


02 02/09/20 Re-Issued for Use B. Haslow GHD Pty Ltd


Hastings Technology Metals Limited Yangibana TSF Design Development

Pre-Construction Report YGB-31-100-ENG-CIV-REP-0001 August 2020 Revision 2

GHD | Report for Hastings Technology Metals Limited - Yangibana TSF Design Development, 3219134 | i

Table of contents 1. Introduction .................................................................................................................................... 1

1.1 Overview .............................................................................................................................. 1

1.2 Purpose of the report ........................................................................................................... 1

1.3 Limitations ............................................................................................................................ 1

2. Background .................................................................................................................................... 3

2.1 General ................................................................................................................................ 3

2.2 Site location ......................................................................................................................... 3

2.3 Site condition and topography ............................................................................................. 3

2.4 Climate ................................................................................................................................. 4

2.5 Geology ................................................................................................................................ 5

2.6 Geotechnical investigations ................................................................................................. 5

2.7 Hydrogeology and groundwater ........................................................................................... 6

2.8 Hydrology ............................................................................................................................. 8

2.9 Seismicity ............................................................................................................................. 8

2.10 Mining .................................................................................................................................. 8

2.11 Processing and tailings waste streams ................................................................................ 8

3. Design refinement opportunities .................................................................................................. 10

4. Basis of Design ............................................................................................................................ 14

4.1 Design reference documentation ....................................................................................... 14

4.2 Basis of design parameters ............................................................................................... 16

5. Tailings characterisation .............................................................................................................. 18

5.1 Tailings testing ................................................................................................................... 18

5.2 Physical properties ............................................................................................................. 19

5.3 Geochemical characterisation ........................................................................................... 21

6. Design development concept ....................................................................................................... 35

6.1 General arrangement ......................................................................................................... 35

6.2 Concept details .................................................................................................................. 36

6.3 Water management ........................................................................................................... 37

6.4 Environmental risk and mitigation measures ..................................................................... 38

6.5 Closure and rehabilitation concept .................................................................................... 41

7. Consequence based design requirements .................................................................................. 44

7.1 General .............................................................................................................................. 44

7.2 DMIRS TSF characterisation ............................................................................................. 44

7.3 ANCOLD consequence category ....................................................................................... 45

7.4 Category based design criteria .......................................................................................... 46

8. Pre-construction design details ................................................................................................... 48

8.1 Construction materials and site clearing ............................................................................ 48

GHD | Report for Hastings Technology Metals Limited - Yangibana TSF Design Development, 3219134 | ii

8.2 Beneficiation TSF ............................................................................................................... 48

8.3 Hydromet TSF .................................................................................................................... 51

9. Specific design studies ................................................................................................................. 56

9.1 Stormwater storage assessment ....................................................................................... 56

9.2 Flood hydrology ................................................................................................................. 57

9.3 Water balance .................................................................................................................... 60

9.4 Seepage analysis ............................................................................................................... 63

9.5 Stability analysis ................................................................................................................ 65

9.6 Seismic assessment .......................................................................................................... 68

9.7 Hydromet TSF ammonia gas air emissions study ............................................................. 69

10. Operations, maintenance and surveillance .................................................................................. 71

10.1 Observational approach ..................................................................................................... 71

10.2 Monitoring and surveillance ............................................................................................... 71

10.3 Operation, maintenance and surveillance manual ............................................................ 73

10.4 Dam safety emergency plan .............................................................................................. 74

10.5 Annual audits ..................................................................................................................... 74

10.6 TSF operator training ......................................................................................................... 74

10.7 Temporary mining and plant shutdown provisions ............................................................ 75

11. References ................................................................................................................................... 76

Table index Table 2-1 Falling head in situ permeability test results (ATCW, 2019) ................................................ 6

Table 2-2 Water test results (ATCW, 2019) ......................................................................................... 6

Table 2-3 Storage volume requirement estimates ............................................................................... 9

Table 2-4 Potential water release ........................................................................................................ 9

Table 4-1 Standard documentation .................................................................................................... 14

Table 4-2 Hastings provided documentation ..................................................................................... 15

Table 4-3 Basis of design parameters ............................................................................................... 16

Table 4-4 TSF design characteristics ................................................................................................ 17

Table 5-1 Previous testing summary ................................................................................................. 18

Table 5-2 Testing physical characterisation test results .................................................................... 19

Table 5-3 Beneficiation tailings assumed physical properties ........................................................... 20

Table 5-4 Hydromet tailings assumed physical properties ................................................................ 20

Table 5-5 TSF 1 and 2 geochemical analysis summary .................................................................... 22

Table 5-6 Summary of geochemical test work ................................................................................... 22

Table 5-7 Summary of total metal (ICPMS) concentration and GAI values* ..................................... 24

GHD | Report for Hastings Technology Metals Limited - Yangibana TSF Design Development, 3219134 | iii

Table 5-8 LEAF leach and pore water compared to ANZECC and ARMCANZ livestock guidelines (2000) ............................................................................................................... 28

Table 5-9 LEAF leach and pore water compared to NEPM drinking water and fresh water

guidelines (2013) ............................................................................................................... 29

Table 5-10 Summary of Beneficiation TSF characterisation* .............................................................. 31

Table 5-11 Evaporation pond and TSF 3 geochemical analysis summary* ........................................ 32

Table 5-12 Mass balance of Hydromet TSF* ....................................................................................... 33

Table 5-13 Summary of Hydromet TSF 3 characterisation ................................................................. 34

Table 5-14 Summary of key analytes for the TSFs* ............................................................................ 34

Table 6-1 Beneficiation decant recovery ............................................................................................ 37

Table 6-2 Tailings liquor concentrations exceeding reference values ............................................... 40

Table 6-3 TSF closure specification ................................................................................................... 41

Table 7-1 DMIRS TSF characterisation ............................................................................................. 44

Table 7-2 Design criteria from consequence category ...................................................................... 47

Table 8-1 Beneficiation TSF starter embankment geometry ............................................................ 48

Table 8-2 Hydromet TSF starter embankment geometry .................................................................. 51

Table 9-1 Freeboard and stormwater storage requirements ............................................................. 57

Table 9-2 Cut-off drain design parameters ........................................................................................ 59

Table 9-3 Hydromet TSF data ............................................................................................................ 60

Table 9-4 Tailings material and bleed water data .............................................................................. 60

Table 9-5 Climate input data .............................................................................................................. 60

Table 9-6 Simulation settings ............................................................................................................. 61

Table 9-7 Model hydraulic conductivity values .................................................................................. 63

Table 9-8 Stability analysis FOS acceptance criteria ........................................................................ 66

Table 9-9 Parameters used for stability analyses .............................................................................. 66

Table 9-10 Results of stability analysis ................................................................................................ 67

Table 10-1 TSF inspection types and frequency ................................................................................. 71

Table 10-2 TSF monitoring types and frequency ................................................................................. 72

Figure index

Figure 2-1 Yangibana project location (ATCW, 2019) .......................................................................... 3

Figure 2-2 TSF site setting .................................................................................................................... 4

Figure 2-3 Conceptual hydrogeological model for TSF site (ATCW, 2019) .......................................... 8

Figure 3-1 General arrangement of FS concept plan (ATCW 2019) .................................................. 10

Figure 3-2 Proposed pre-construction design concept general arrangement .................................... 12

GHD | Report for Hastings Technology Metals Limited - Yangibana TSF Design Development, 3219134 | iv

Figure 3-3 FS concept (red) versus refined pre-construction concept (green) .................................. 13

Figure 5-1 Metal concentration at varying LEAF pH conditions .......................................................... 27

Figure 6-1 General arrangement of TSFs (after 3 years) ................................................................... 35

Figure 6-2 Watercourses and catchment area division around TSF site ............................................ 38

Figure 6-3 TSF closure concept general arrangement ....................................................................... 43

Figure 6-4 TSF concept capping design ............................................................................................ 43

Figure 8-1 Beneficiation TSF storage curve ....................................................................................... 49

Figure 8-2 Beneficiation TSF embankment typical section ................................................................. 49

Figure 8-3 Hydromet TSF embankment typical section ...................................................................... 52

Figure 8-4 Megaflo panel drain examples (courtesy Geofabrics Australia) ........................................ 53

Figure 9-1 ANCOLD freeboard definition ............................................................................................ 56

Figure 9-2 Design rainfall IFD curves .................................................................................................. 58

Figure 9-3 Hydromet TSF hydrograph (critical duration) .................................................................... 58

Figure 9-4 Beneficiation TSF hydrograph (critical duration) ............................................................... 59

Figure 9-5 Overall hydromet TSF inventory ........................................................................................ 62

Figure 9-6 HW/MW vertical seepage rates ......................................................................................... 64

Figure 9-7 Stability model section ....................................................................................................... 65

Figure 9-8 Relative crest settlement versus peak ground acceleration (ATCW, 2019) ...................... 68

Figure 9-9 Ammonia/ammonium concentration vs pH (Richard, 1996) .............................................. 70

Appendices Appendix A – Design Drawings

Appendix B – Tailings Test Results – Geotechnical

Appendix C – Combined Beneficiation Tailings Test Results - Geochemical

Appendix D – Seepage Analysis

Appendix E – Stability Analysis

Appendix F – Consequence Category Assessment

Appendix G – Environmental Benefits Summary Table

Appendix H – Example Geosynthetic Liner Specification

Appendix I – Ammonia Gas Modelling Reports

GHD | Report for Hastings Technology Metals Limited - Yangibana TSF Design Development, 3219134 | 1

1. Introduction1.1 Overview

Hastings Technology Metals Limited (Hastings) is progressing the design and approvals associated with the Yangibana Rare Earths Project (Yangibana Project) in the Gascoyne region

of WA.

A Feasibility Study (FS) has been completed for the project (ATCW, 2019), including concept design of Tailings Storage Facilities (TSFs) and an evaporation pond.

The proposed ore processing concept resulted in three distinct tailings streams as follows:

Tailings from beneficiation plant Rougher and Cleaner 1 flotation cells

Tailings from beneficiation plant Cleaner 2 to Cleaner 4 flotation cells

Tailings (combined residue) from hydrometallurgical (Hydromet.) plant

In addition, the need for an evaporation pond was identified to dispose of spent liquor from the

Hydromet plant together with brine from the RO water treatment plant.

The resulting concept design featured three separate TSFs and an evaporation pond. Following

a review of the Feasibility Study concept design, a number of opportunities for design

development were identified by GHD. This report further explores these opportunities and

develops a Pre-Construction Design to progress project approvals.

1.2 Purpose of the report

The purpose for this report is to describe the opportunities for refinement of the Feasibility

Study concept design, and to present an updated pre-construction design for disposal of

flotation tails from the Beneficiation Plant and residue and spent liquor from the Hydromet plant.

Design studies have been completed to a pre-construction level, for inclusion in EPA Approvals

documentation, Mining Proposal, and Works Approval documentation.

1.3 Limitations

This report has been prepared by GHD for Hastings Technology Metals Limited and may only be used and

relied on by Hastings Technology Metals Limited for the purpose agreed between GHD and the Hastings

Technology Metals Limited as set out in section 1 of this report.

GHD otherwise disclaims responsibility to any person other than Hastings Technology Metals Limited

arising in connection with this report. GHD also excludes implied warranties and conditions, to the extent

legally permissible.

The services undertaken by GHD in connection with preparing this report were limited to those specifically

detailed in the report and are subject to the scope limitations set out in the report.

The opinions, conclusions and any recommendations in this report are based on conditions encountered

and information reviewed at the date of preparation of the report. GHD has no responsibility or obligation to

update this report to account for events or changes occurring subsequent to the date that the report was

prepared.

The opinions, conclusions and any recommendations in this report are based on assumptions made by

GHD described in this report. GHD disclaims liability arising from any of the assumptions being incorrect.

GHD has prepared this report on the basis of information provided by Hastings Technology Metals Limited

and others who provided information to GHD (including Government authorities), which GHD has not


independently verified or checked beyond the agreed scope of work. GHD does not accept liability in

connection with such unverified information, including errors and omissions in the report which were

caused by errors or omissions in that information.

GHD has prepared the preliminary cost estimates using information reasonably available to the GHD

employee) who prepared this report; and based on assumptions and judgments made by GHD

The Cost Estimate has been prepared for the purpose of comparison of options and must not be used for

any other purpose.

The Cost Estimate is a preliminary estimate only. Actual prices, costs and other variables may be different

to those used to prepare the Cost Estimate and may change. Unless as otherwise specified in this report,

no detailed quotation has been obtained for actions identified in this report. GHD does not represent,

warrant or guarantee that the [works/project] can or will be undertaken at a cost which is the same or less

than the Cost Estimate.

Where estimates of potential costs are provided with an indicated level of confidence, notwithstanding the

conservatism of the level of confidence selected as the planning level, there remains a chance that the

cost will be greater than the planning estimate, and any funding would not be adequate. The confidence

level considered to be most appropriate for planning purposes will vary depending on the conservatism of

the user and the nature of the project. The user should therefore select appropriate confidence levels to

suit their particular risk profile.


2. Background2.1 General

Background information has been presented in detail in the TSF Concept Design Report

(ATCW, 2019). A summary of background data is presented in the following sections to assist with the reader’s understanding.

2.2 Site location

The Yangibana Project is located in the Gascoyne region of Western Australia, approximately 270 km northeast of Carnarvon. Figure 2-1 below shows the site location.

Figure 2-1 Yangibana project location (ATCW, 2019)

2.3 Site condition and topography

The proposed TSF is located in an area of undulating topography where a number of small gullies are formed between subtle rises at ground level. These gullies are initially utilised to form

the TSF embankments. The TSF site is located between two existing tributaries of Fraser Creek. To the east and south of the TSF the natural ground continues to rise to a ridge line that exists at around RL350 (approximately 20 m higher elevation than the TSF crest). The small

catchment between this ridge and the TSF is managed by the construction of a diversion channel. A locality plan is shown in Figure 2-2.


Figure 2-2 TSF site setting

2.4 Climate

The Köppen-Geiger climate classification denotes the TSF area as being within the BWh

climate zone (Peel et al. 2007) which is considered to be an arid and semi-arid climate with an

average annual temperature above 18°C. The area is typically impacted by the west coast

trough, northwest cloudbanks, tropical cyclones, frontal systems and a subtropical ridge (Bureau

of Meteorology [BoM] 2010).

The west coast trough is a semi-permanent climatic feature with a dominating effect on weather

conditions during the warmer months in the southwest of Western Australia. The trough is a low

pressure zone that develops at the boundary between the warm continental easterly winds and

cooler maritime winds from the Indian Ocean. While the trough development depends on

prevailing conditions, however it is generally noted that areas to the east of the trough

experience hot days in excess of 40°C, thunderstorms and heavy rainfall, with areas to the west

experiencing milder conditions (Bureau of Meteorology [BoM] 2010).

Similarly to the west coast trough, the northwest cloudbanks are also active during the warmer

months forming when moist tropical air from the Indian Ocean moves south-eastward, and is

forced to rise over the colder mid latitude air. Widespread heavy rain can be expected with the

northwest cloudbanks (Bureau of Meteorology [BoM] 2010).

The cyclone season is officially from November to April although there tends to be fewer

cyclones early in the season. Destructive winds and high rainfall can be associated with tropical

cyclones (Bureau of Meteorology [BoM] 2010).

Frontal systems are known to impact the TSF area with cold fronts bringing rainfall for extended

periods of up to a week. The subtropical ridge discussed previously suppresses frontal activity


during the warmer months while in winter the ridge moves over central Australia, permitting cold fronts to extend further northwards (Bureau of Meteorology [BoM] 2010).

Given the number of climate influence that may be active and affecting the study area, it is unsurprising that the rainfall is erratic and bimodal (i.e. occurring in both winter and summer) (Desmond et al. 2001; Kendrick 2002).

The mean daily temperature recorded by the closest full suite weather station, Mount Phillips Station (station number 007058), ranges from 9°C in July to 40°C in January. The closest rainfall recording station, Wanna Station (station number 007028), indicates an average rainfall

of 244.9 mm with a maximum annual rainfall of 550 mm in 1999.

2.5 Geology

The geology within the area is dominated by Pimbyana Granite and Yangibana Granite. Meta-

sedimentary rocks including sandstones, calcareous-silicates and schists also occur across the site (ATCW, 2019). The granite in the area is well exposed forming the gently undulating topography across the tenement.

The near surface expression of the fenitised ferrocarbonatite sills/dykes is represented by sinuous veins of ironstones primarily of magnetite composition.

Geological investigations have found localised deposits of unconsolidated silt, sand and gravel

in the creeks crossing the site and calcrete deposits locally present adjacent to the alluvial channels.

2.6 Geotechnical investigations

ATCW completed a geotechnical investigation at the previously proposed TSF and evaporation pond sites in late 2016, in conjunction with further investigations for the additional site infrastructure locations. The geotechnical investigation report undertaken by ATCW can be

found in Appendix C of ATCW FS Concept Design Report. The locations of the exploratory test pits and boreholes are illustrated in Figure 14 of the ATCW Preliminary Design Report.

2.6.1 General soil profile

ATCW found the ground conditions observed across the site generally comprised a thin cover of

clayey sand with minor gravel overlying residual clayey and sandy gravels. Granite was exposed at ground surface in elevated areas across the site.

2.6.2 Residual soils / extremely weathered

The investigation found that below the clayey sand layer a dense clayey gravel was

encountered. In many places, the clay content decreased with depth, grading to sandy gravel.

The clayey gravel was considered fine to coarse, with occasional sub angular and angular cobbles, whereas the sandy gravel was typically fine to coarse, pale brown, with minor clay and

trace angular cobbles. ATCW found the moisture content of the residual soil was below 10%.

2.6.3 Granite

Refusal of the test pits undertaken by ATCW was found to be between 0.1 m and 2.4 m. Near surface rock was generally high to moderately weathered, the strength of the rock was

assessed as low to medium strength.

Boreholes around the Beneficiation TSF found that significant weathering in the granite was limited to 10 m. The granite was found to be pale grey and porphyritic with minor black crystals


of mafic minerals. The rock jointing was considered tight and rough with pale brown staining primarily in the upper weathered zones.

2.6.4 In situ permeability testing

During the borehole drilling at the Beneficiation TSF site, falling head permeability testing was undertaken with results tabulated below in Table 2-1.

Table 2-1 Falling head in situ permeability test results (ATCW, 2019)

Test Pit ID Depth Permeability K (m/s) Material

CTBH-01 0.00 – 6.60 m 1.14 x 10-07 HW Granite

CTBH-01 0.00 – 1.50 m 2.95 x 10-08 Clay / EW Granite

CTBH-02 0.00 – 1.60 m 1.57 x 10-07 EW / MW Granite

CTBH-02 0.00 – 5.60 m 1.40 x 10-08 EW / MW Granite

CTBH-03 0.00 – 6.55 m 7.44 x 10-09 Clay / Clayey Sand

CTBH-03 0.00 – 0.90 m 2.06 x 10-07 Clayey Sand / EW / MW Granite

CTBH-04 0.00 – 10.70 m 1.12 x 10-06 HW / SW Granite

CTBH-05 0.00 – 11.85 m 1.65 x 10-06 HW / SW Granite

Packer testing was also undertaken on boreholes CTBH-01 & CTBH-03, the results of which are

summarised in Table 2-2. The permeability values as interpreted by ATCW from the Lugeon test results are included.

Table 2-2 Water test results (ATCW, 2019)

Borehole ID

Test Type Test Interval (m)

Permeability k (m/s)

Lugeon Value

Material

CTBH-01 Falling Head 9.8 – 22.2 1.0 x 10-07 - SW Granite

CTBH-01 Falling Head 23.3 – 37.2 2.3 x 10-07 - FR Granite

CTBH-01 Constant Head 22.6 – 36.5 9.2 x 10-06 - FR Granite

CTBH-03 Constant Head 9.5 – 21.5 3.5 x 10-06 - SW Granite

CTBH-03 Lugeon 9.5 – 55.5 3.9 x 10-08 0.3 MW/FR Granite

CTBH-03 Lugeon 26.6 – 39.2 6.4 x 10-09 0.049 MW/SW Granite

2.7 Hydrogeology and groundwater

2.7.1 Regional hydrogeology

The regional hydrogeology of the area has been described by Groundwater Resource Management (GRM 2017). The model was derived from publically available datasets and a desktop assessment (ATCW, 2019).

The hydrogeology of the area is characterised by a south westerly draining system, coincident with the Lyons river surface water catchment. Alluvial cover is typically thought to be thin across most of the catchment but thickens towards the creeks and major drainage lines.

The hydrogeological conceptual model identified three hydrogeological units:

HU1 – Comprised of alluvium and calcrete thought to be discontinuous across the broader

project area. The alluvium is typically absent or less than a few metres thick and occupies

low lying areas in creeks and drainage channels. Calcrete is known to occur adjacent to

major drainage features (Lyons and Edmonds Rivers) and can be up to 30 m thick.


HU2 – This comprises discrete ironstone units within the surrounding fresh bedrock. Theironstone units are narrow, regionally extensive and pinch and swell along strike and with

depth. Groundwater yields are generally low to moderate, however storage within the unit islikely to be low given the discrete nature of the units.

HU3 – Comprised of granites, granodiorite, and monzonites which from the hangingwall

and footwall of HU2 when they are in contact. The permeability of the units is very low withlow storage characteristics. Drill hole data from around Frasers and the TSF site suggestthat the weathering profile is relatively shallow, generally less than 10 m.

Recharge to the aquifer system is likely to occur predominately by stream flow from the

dominant creeks and tributaries and through direct rainfall.

A search of registered bores within a 20 km radius of Bald Hill was conducted using the Water

Information reporting database, which indicated that there were 15 bores within this radius. The

closest registered bore to Frasers Pit was approximately 5 km to the west and whilst it is listed

as being of unknown type, it is assumed, based on surrounding land use type, to be used for

livestock watering.

2.7.2 TSF site hydrogeological conditions

Geotechnical investigations were carried out within the immediate vicinity of the proposed TSF

site by ATCW in 2016, as reported in ATCW 2017. This included excavation of numerous test

pits and a drilling investigation using both diamond coring and reverse circulation methods with

associated packer and falling head testing. The ground conditions identified across the site

were reported as generally comprising a thin superficial cover of clayey sand with minor gravel

overlying residual clayey and sandy gravels derived from weathering of the underlying granite

rock mass. Granite was exposed at ground surface in most of the elevated site areas. The

depth of weathering in the rock mass was variable but typically the material became slightly

weathered at depths of less than 10 m.

These investigations were used to develop a conceptual site hydrogeological model (ATCW

2019). A typical conceptual hydrogeological model for the site is shown below in Figure 2-3.

This model has been utilised for the development of the pre-construction design.

Groundwater samples recovered from the vicinity of the Bald Hill and Frasers pits were fresh to

slightly brackish with TDS between 920 mg/l and 1,200 mg/l.

Groundwater sampled by ATCW from eight pastoral bores in the vicinity of the mine in 2015 had

TDS of 600 mg/l and 920 mg/l in two shallow alluvial bores (i.e. Contessi Bore and Minga Well),

and ranged from 1,400 mg/l to 2,800 mg/l in the remaining bores, believed to be installed into

fractured rock.

Drawdown modelling completed by GRM for dewatering of the Bald Hill and Frasers pits,

indicates the proposed TSF site is likely to be outside of the drawdown influence from the Frasers pit.


Figure 2-3 Conceptual hydrogeological model for TSF site (ATCW, 2019)

2.8 Hydrology

A hydrological assessment undertaken by JDA consultant hydrologists found that the catchment

drains towards Lyon River, with the dominant drainage feature near the TSF area being Frasers

Creek passing to the western side of the TSF area (ATCW, 2019).

Assessment to-date has identified that the TSF area would not be adversely affected by flooding

of local drainage lines following rainfall associated with storm events up to 1:100 year ARI

(ATCW, 2019). Further findings of the hydrological assessment regarding additional

infrastructure are defined in the JDA report.

2.9 Seismicity

Based on the Geoscience Australia seismic hazard map, the site is in an area of moderate

seismicity (ATCW, 2019).

2.10 Mining

Hastings plan to undertake mining in multiple stages in open pits using drill and blast methods,

with Bald Hill, Frasers and Yangibana North/West ore deposits being the priority pits for initial

mining development (ATCW, 2019).

The TSF design will cater for a mine life of 10 years with a mining rate of 1 MtPa. For the

purposes of TSF design, a mine life of 10 years has been considered.

Waste rock landforms consisting primarily of slightly weathered to fresh granite will be located

on the northern footwall side of the pits. The saprolitic material at Bald Hill will be stockpiled

separately and may be used as low permeability material for TSF construction (ATCW, 2019

and Hastings verbal confirmation).

2.11 Processing and tailings waste streams

Three tailings streams are expected from the proposed processing route (ATCW, 2019) as

follows:

Tailings from beneficiation plant Rougher and Cleaner 1 flotation cells. This represents 95%

of the total beneficiation plant tailings stream (or 88% of total tailings).

Tailings from beneficiation plant Cleaner 2 to Cleaner 4 flotation cells. This represents less

than 5% of the total beneficiation plant tailings stream (or 4.5% of total tailings).

Downstream Tributary of Fraser Creek

Ridgeline TSF Location


Tailings (combined residue and solution) from hydrometallurgical (Hydromet.) plant. This

represents approximately 7% of the total tailings produced.

Wastewater from the hydrometallurgical process and reverse osmosis effluent from the water treatment plant will not be of suitable quality for re-use in the processing circuits and will need to be evaporated as barren liquor. The estimated production rates of the various waste materials

were estimated by ATCW as summarised in Table 2-3 and Table 2-4. Note that these estimates are net values and do not include any contingency.

Table 2-3 Storage volume requirement estimates

Tailings Type Inflow

Solids

Content

Annual

Productio

n Solids

(t)

Mass

Water in

Slurry (t)

Assumed

In Situ Dry

Density

(t/m3)

Expected

Annual In

situ

Volume

(m3)

Total

Storage

Required

for LOM

(m3)

Bene Plant

Rougher and

Cleaner 1

49% 927,600 965,500 1.60 579,700 5,797,600

Bene Plant Cleaner 2,

3, 4

8% 47,500 116,000 0.75 63,200 632,000

Hydromet Plant

Residue

45% 62,500 93,500 0.50 124,800 1,248,000

Hydromet Plant

Scrubbing

Effluent

35% 11,000 20,500 0.50 22,000 221,000

Barren Liquor 0% 434,500 1.00 434,500 NA

Combined

Hydromet Waste

11% 72,000 550,000 0.50 144,000 1,440,000

Combined Bene

Plant Waste

52%

(Note 1) 975,000 900,000 1.50 650,000 6,500,000

Note 1 – Tailings solids content as advised by Hastings 28th March 2019 based on thickening test work.

Table 2-4 Potential water release

Tailings Type SG Solids Volume Solids (m3/a)

Volume Retained Water (m3/a)

Volume Water Released (m3/a)

Bene Plant Rougher and Cleaner 1

3.3 281,000 298,500 668,800

Bene Plant Rougher and Cleaner 2 - 4

3.22 14,700 48,500 67,500,

Hydromet Plant Residue

3.16 19,700 105,000 -11,455

Hydromet Plant Scrubbing Effluent

3.16 3,500 18,600 1,900

Combined Hydromet Waste

3.16 22,700 121,000 428,900

Combined Bene Plant Waste

3.3 295,500 354,500 545,500


3. Design refinement opportunitiesGHD Technical Memorandum dated 6th February 2019, “Options Assessment Memorandum” presented a proposed refined concept design for tailings management for the Yangibana

project.

The ATCW FS concept design tailings strategy to date was to construct 5 storage dams as follows:

TSF 1 to receive beneficiation plant Rougher and Cleaner 1 flotation cells tailings. TSF 1

was proposed as a central thickened discharge facility.

TSF 2 to receive beneficiation plant Cleaner 2 to Cleaner 4 flotation cell tailings. TSF 2 was

proposed as a paddock type facility with spigotted perimeter discharge.

TSF 3 to receive combined residue and solution from the hydromet plant. TSF 3 is

proposed as a paddock type facility with spigotted perimeter discharge. A BGM liner and

underdrainage system was proposed.

Return Water Pond (RWP) for storage of run-off and decant waters removed from TSF 1

and TSF 2. The WRP has an upstream clay zone and cut-off trench, sand filter and

downstream general rockfill zone.

Evaporation Pond for evaporation of barren water from the hydrometallurgical process and

reverse osmosis plant. The Evaporation Pond is proposed to be fully HDPE lined and

separated into 3 evaporation cells to maximise evaporation potential.

Figure 3-1 shows the general arrangement associated with this FS concept.

Figure 3-1 General arrangement of FS concept plan (ATCW 2019)

GHD identified a number of refinements and opportunities within the existing FS Concept design

arrangement and limitations agreed with Hastings. In particular, the potential to simplify operations and construction including using topography to advantage for more conventional tailings disposal was identified. Low height starter embankments built across existing gullies are

able to cater for the initial years of operation followed by conventional downstream raising of the facilities to expand the facility until end of mine life.


The FS concept design originally proposed Central Thickened Discharge (CTD) for TSF1. This

method of tailings disposal can be very sensitive to thickener performance. A more conventional

tailings dam approach is now proposed that uses perimeter tailings discharge via spigots but

with some CTD components for elevating the tailings beach in a safe manner. While this gives

slightly higher embankment and pipe costs, it eliminates the risks of flatter than expected beach

slopes resulting in insufficient storage capacity during operations.

The concept taken through to Pre-Construction Design as described in this report includes:

1. Combination of TSF 1 and TSF 2 and conversion to a perimeter discharge facility

This change is on the basis of combining the Cleaner 2, 3 and 4 beneficiation tailings with the

Rougher and Cleaner 1 beneficiation tailings. The very fine grained Cleaner 2, 3 and 4 tailings

are expected to be very low density and known to settle poorly unless blended with Rougher

and Cleaner 1 tailings. This means poor beaching, low density and significant water losses in a

separate fines TSF (i.e. TSF 2). Testing is currently underway to confirm the settling

characteristics of the combined beneficiation steam. Recent column settling test work has

returned favourable results indicating suitable decant clarity associated with the combined

tailings (see Section 5.2 for results). This confirms the expected behaviour where the fine

particles are trapped within the overall tailings matrix.

The other consideration at the time of separating the streams was to maintain the higher Total

Activity Concentration (TAC) of radionuclides in Cleaner 2, 3 and 4 tailings within TSF 2. Test

data used by ATCW (ATCW, 2019) showed for separate facilities the Rougher/Cleaner 1

component would have Bq/g of 0.7 and the Cleaner 2, 3 and 4 component Bq/g of 4.0. With

respect to the IAEA guidance on waste classification, both streams may be considered as low-

level NORM waste, suitable for above ground disposal in a tailings facility subject to

satisfactorily meeting appropriate safety requirements (ATCW, 2019). The Cleaner/Rougher 1

tailings which form the majority of the process tailings material have an expected activity

concentration < 1 Bq/g and may effectively be considered as being exempt from classification

as radioactive waste (ATCW, 2019). However, the Cleaner 2, 3 and 4 component is estimated

as comprising only 4% by weight. The combined tailings stream TAC is expected to be

approximately 0.8 Bq/g, still effectively below 1. This 0.8 Bq/g is averaged over the operational

mine life noting that during commissioning, Hastings advise that the TAC is expected to be

about 1.4Bq/g due to the lower initial recovery, resulting in a slightly increased radioactivity level

at start-up.

In addition, the combined beneficiation tailings stream is expected to result in better control of

dust on the combined TSF due to the improved grading, higher moisture level and potential for

crusting. While the tailings are considered benign, dust in general is still considered an

environmental hazard and should be reduced to as low as reasonably practicable. Dust

management is further discussed in Section 6.4.2.

Other benefits of the proposed conventional perimeter discharge in the standalone

Beneficiation TSF include:

Allows the formation of wide beaches upstream of the perimeter embankment that reducesthe risk of seepage and embankment piping. There is less reliance on diversion of surface

water to remove ponding water away from the embankments into the separate ReturnWater Pond as proposed in the original design.

Allows for the development of a decant pond that can be maintained well upstream of the

perimeter embankments, which provides significant stormwater storage capacity with lowrisk of water ponding against the embankments.

Eliminates the need for the Return Water Pond as proposed in the original concept. This

reduces capital cost and environmental risk posed by building a standalone water dam


alongside the drainage line (i.e. reduced dam failure and seepage risks to the environment).

2. Combining the Hydromet wastes

Combining the Hydromet wastes results in reduced dust risk from the original TSF 3, relying on

transfer of barren liquor from the evaporation pond, and reduces the risk of low density waste

requiring underdrainage. The combined facility allows well proven liner technology using a

combined compacted clay and HDPE liner system (i.e. geocomposite lining system).

Preliminary assessment of the combined waste streams indicates the potential for a small

amount of ammonia gas release at the TSF. Further modelling and assessments provided by

Hastings have confirmed that associated health and safety risks are low and can be managed,

even under worst case scenario conditions (refer Section 9.7).

Figure 3-2 shows the refined concept general arrangement for the basis of the Pre-Construction Design. The following TSF naming convention is used for the Pre-Construction Design presented herein:

Beneficiation TSF: The combined TSF 1 and TSF 2 that receives all Beneficiation tailings

Hydromet TSF: The TSF receiving the combined Hydromet residue, spent liquor and brine

Figure 3-3 shows the respective concept designs overlain for comparative purposes, showing a

reduced overall disturbance footprint for the Pre-Construction Design (FS Concept in red and

Refined Pre-Construction Design in green).

Appendix H includes a summary table highlighting the operational and environmental benefits of

the proposed refined concept design relative to the originally planned FS concept.

Figure 3-2 Proposed pre-construction design concept general arrangement


Optimisation of the Beneficiation tailings thickening process is still ongoing with the aim of maximising water recovery for plant reuse. At this stage there is no foreseeable basis for the

Beneficiation tailings streams to be separated. In the unlikely event that future plant optimisation demonstrates a significant advantage associated with separating the Cleaner 2 - 4 tailings from the Rougher and Cleaner 1 tailings, this could be achieved by constructing a low height dividing

embankment to create a small separate cell for the Cleaner 2, 3 and 4 tailings (see location Figure 3-2). This would be similar to that proposed in ATCW 2019 but would be contained upstream of broader Beneficiation TSF to avoid creating a separate stand-alone facility (i.e.

reduced risk relative to ATCW 2019).

Figure 3-3 FS concept (red) versus refined pre-construction concept (green)


4. Basis of DesignThis section defines the Basis of Design (BoD) for the Pre-Construction Design phase of

the two TSFs resulting from development of the FS concept design.

4.1 Design reference documentation

4.1.1 General

A detailed listing of the documents, standards, codes and guidelines to be followed in

the preparation of the Pre-Construction Design are outlined below.

4.1.2 Standards and regulations

Table 4-1 below outlines the standard regulation guidelines that have been used in the

development of the pre-construction design of the alternative arrangement.

Table 4-1 Standard documentation

Organisation Year Title

ANCOLD 1998 Guidelines for Design of Dams for Earthquake

ANCOLD 2000 Guidelines on Selection of Acceptable Flood Capacity for Dams

ANCOLD 2003 Guidelines on Dam Safety Management

ANCOLD 2012 Guidelines on the Consequence Categories for Dams

ANCOLD 2012 Guidelines on Tailings Dams Planning, Design, Construction, Operation and Closure

ANCOLD 2018 Draft Guidelines for Design of Dams and Appurtenant Structures for Earthquake

DME 1998 Guidelines on the Development of Operating Manual for Tailings Storage Facilities

DMP 2010 Managing Naturally occurring Radioactive Material (NORM) in mining and mineral processing, guideline NORM 4.2

DMP 2013 Tailings Storage Facilities in Western Australia – Code of Practice

DMP 2015 Guideline to the Preparation of a Design Report for Tailings Storage Facilities (TSFs)

DMP 2016 Draft Guidance – Materials Characterisation Baseline Data Requirements for Mining Proposals

DMP & EPA 2015 Guidelines for Preparing Mine Closure Plans

DoW 2013 Water Quality Protection Note 27; Liners for Containing Pollutants using Engineered Soils

IAEA 2009 Classification of Radioactive Waste, General Safety Guide

NEPM 1999/2013 Schedule B1; Investigation Levels for Soil and Groundwater


4.1.3 Hastings documentation

Table 4-2 below outlines the information provided to GHD by Hastings that has been used in

the development of the Pre-Construction Design of the alternative arrangement.

Table 4-2 Hastings provided documentation

Organisation Year Title

Graeme Campbell & Associates Pty Ltd

2017 DFS Study - Stage 1 Hydrogeological Assessment, Yangibana Rare Earths Project, Ref J160014R01.

Radiation Professionals

2016 Baseline Radiation Report, unpublished report for Hastings Technology Metals Limited, November 2016.

Radiation Professionals

2016 Radiation Waste Characterisation Report, unpublished report for Hastings Technology Metals Limited, November 2016.

ANSTO Minerals 2017 Secular Equilibrium and Leach Testing – TSF Solids, Technical Memorandum AM/TM/2017_08_04.

ANSTO Minerals 2017 Pilot Plant Waste Neutralisation and Characterisation, Progress Note 3.

Hastings 2018 Environmental Risk Assessment EnvRisk Ass_MP20170129.

Outotec 2017 Yangibana Flotation Tailings, Rougher, Rougher & Cleaner, Cleaner, Flotation Concentrate, Thickening Test Reports S2786TE.

Trajectory 2017 Landform Evolution Study (R1)

Trajectory 2019 Landform Evolution Assessment

Graeme Campbell & Associates Pty Ltd

2018 Yangibana Rare Earths Project, Tailings Leach Study Report Revision 0.

Landloch 2016 Yangibana Project Soil Assessment, Ref 2274.16A.

ATC Williams 2017 4254-30-RPT-XD-00046 – Geotechnical Investigation.

ATC Williams 2016 4254-30-RPT-XD-00029 Pre-Feasibility Study of Tailings Storage Facility.

ATC Williams 2016 4254-30-RPT-XD-00030 Tailings Storage Facility Options Study.

Hastings 2018 YGB_Tebure_20180626_GDA94z50.

Hastings 2018 Environmental Review Document – Assessment Number 2115 EPBC 2016/7845 Rev 4.

JRHC 2019 Review of ANSTO Results for Samples from Leach Testing of TSF 1 and 2 Samples and Comparison with Groundwater Sampling Results.

Hastings & Groundwater Resource Management

2017 DFS Study – Stage 1 Hydrogeological Assessment.

Hastings & Groundwater Resource Management

2018 Stage 1 Fractured Rock Hydrogeological Assessment.

Resources Health and Safety Services

2016 Radiation Management Plan

Hastings 2019 TSF 2 Seepage Model – Results.

Hastings 2019 P058 Yangibana Plot Plan.

ERM 2019 Screening level air quality assessment of Ammonia emissions from the Hydromet TSF Ref:0504573


4.2 Basis of design parameters

The Basis of Design (BoD) is presented below in Table 4-3, including sources and assumptions.

The pre-construction design has been completed based on information provided to GHD by

Hastings, including feasibility level process design, waste classification, water balance and

limited geotechnical knowledge available at the time of this report issue. During investigations,

construction and operation, it is essential to monitor these conditions, verify assumptions made

in the design and then refine designs as actual data is available over time. This will allow

designs to be optimised over time, as further information becomes available and the design and

construction methodologies evolve.

Instrumentation data reviews are essential to identify trends in the data that may require design

changes. It is necessary to take proactive steps well before the integrity of the structures and /

or the operations are impacted. Addressing issues at a later stage may be operationally difficult,

expensive and could be impractical.

Table 4-3 Basis of design parameters

Design Aspect Design Basis Design Source

Storage

Life of Mine 10 Years Feasibility Design Report

Total LOM Tailings Volume ~ 7.5 Mm3 GHD Assessed

Climate

Average Monthly Rainfall 18.9 mm Feasibility Design Report Average Monthly Evaporation 264.9 mm

Annual Tailings Production

Beneficiation Plant Rougher + Cleaner 1 Tailings

927,000 t Hastings

Beneficiation Plant Cleaners 2, 3, 4 Tailing

47,500 t

Hydromet Plant Tailings 72,000 t

Estimated LoM Tailings Production Solids

Beneficiation Plant Rougher + Cleaner 1 Tailings

9.27 Mt Hastings

Beneficiation Plant Cleaners 2, 3, 4 Tailing

0.475 Mt

Hydromet Plant Tailings 0.72 Mt

Barren Water Effluent Production

Hourly Production 58 t/m3

Annual Production 457,000 m3

Project Restrictions

Waterway exclusion zone 50 m (Minimum) Kick Off Meeting Minutes Location Within FS concept general

arrangement footprint

Radiation Risk based management

Groundwater Minimise impact

Dust Risk based management


Water Re-Use Beneficiation tailings water suitable for reuse Hydromet water and RO brine not suitable for re-use

Table 4-4 TSF design characteristics

Design Aspect Design Basis Design Source

Beneficiation TSF

Waste Types Stored All Beneficiation Plant Tailings Hastings

Decant Water Reuse Suitable for Plant Reuse

Embankment Crest Width 7 m GHD Assessed

Embankment Trafficable Width 4 m (minimum)

Embankment Upstream Slope 2H : 1V

Embankment Downstream Slope 2.5H : 1V

Tailings Beach Slope (based on 49% solids)

1% Assumed

Tailings Deposition Method Perimeter discharge with spigots at nominal 50 m spacing

GHD Assessed

Starter Dam Capacity 3 Years

Decant Arrangement Central Pond and Decant Tower

Construction Material Mine waste and available onsite materials

Hydromet TSF

Waste Types Stored Hydromet Tailings and Barren Water (combined)

Hastings

Decant Water Reuse Not Suitable for Plant Reuse

Crest Width 7 m GHD Assessed

Trafficable Width 4 m (minimum)

Upstream Slope 3H : 1V

Downstream Slope 2.5H : 1V

Tailings Beach Slope 0 - 0.25% Assumed GHD Assessed Tailings Deposition Method Single Point Discharge

Starter Dam Capacity 3 Years

Lining Requirement Geocomposite liner 300 mm CCL plus Geosynthetic Liner (1.5 – 2.0 mm HDPE)

Decant Arrangement No water return to plant

Construction Material Mine waste and available onsite materials


5. Tailings characterisation5.1 Tailings testing

5.1.1 Previous testing

A summary of the previous analysis performed on the pilot tailings is presented in Table 5-1.

Table 5-1 Previous testing summary

Date Source Material Analysis

2016 Radpro Baseline monitoring and beneficiation plant tailings (solid & liquid) and hydromet plant residue (solid)

Radiation - activity concentration and exposure classification

2016- 2017

ATCW Beneficiation plant tailings and hydromet plant residue

Physical and geochemical properties

2016- 2017

JRHC Beneficiation plant tailings and hydromet plant tailings (solids & liquids)

Radiation characterisation

2017 Outotec Beneficiation plant tailings and hydromet plant tailings

Plant thickener evaluation test work

2017 ANSTO Minerals

Beneficiation plant tailings and hydromet pilot plant tailings (solids & liquids)

Elemental assays (XRF), radionuclide analysis & ASLP (leachate testing at acidic (pH 5) and alkaline (pH 9.2) conditions)

2017 Trajectory GCA

Beneficiation plant tailing and hydromet plant tailings (solids & liquids)

Geochemical characterisation

2018 Trajectory GCA

Beneficiation plant tailing and hydromet plant tailings (solids & leachate)

Column leach tests with groundwater and high-purity deionised-water

5.1.2 2019 Supplementary testing of combined beneficiation tailings

As discussed in Section 3, design development resulted in a decision to combine all Beneficiation tailings into a single TSF (the “Beneficiation TSF”).

The testing as described above included testing of the Beneficiation rougher and Cleaner 1

tailings as well as Beneficiation Cleaner 2 – 4 tailings. Testing on samples of combined Beneficiation tailings had not been carried out. While the combined tailings properties can be inferred from the results of the testing on the individual tailings streams, it was considered

prudent that further testing be carried out to provide additional data relating to the physical and geochemical properties of the combined Beneficiation tailings.

In March 2019, a suite of physical and geochemical tests commenced at GHD and ALS

Laboratories respectively with the results to be used to further inform detailed design. Results are discussed in the sections that follow.


5.2 Physical properties

5.2.1 General

The results of the testing for the tailings physical characterisation test program are summarised

in Table 5-2, taken from Table 2 of ATC Williams FS Concept Design Report and including available results from the 2019 supplementary testing. The supplementary testing results are included as Appendix B.

Table 5-2 Testing physical characterisation test results

Test Item Unit Beneficiation Rougher + C1

Pilot Plant

Beneficiation (C2 – C4)

Pilot Plant

Combined Beneficiation Tailings (Pilot

Plant)

Hydromet Pilot Plant

Design Stream Beneficiation TSF Hydromet TSF

Source ATCW 2019 ATCW 2019 GHD 2019 ATCW 2019

D100 µm 150 75 300 66

D80 µm 80 10 90 27

<0.075 mm % 77.3 99.7 72 100

SG g/cm3 3.30 3.22 3.12 3.16

Liquid Limit % 21 39 24 113

Plastic Limit % 18 23 21 68

Plasticity Index % 3 16 3 45

Decant pH pH 9.8 10 - 6.5

Permeability (50 kPa)

m/sec 5.0 x 10-09 3.8 x 10-08 2.0 x 10-09 6.0 x 10-08

Solids Content Cw

% 49 20 40 51.7

51.7 Slurry EC µs/cm - - - 10,380

Decant EC µs/cm 2,130 - - -

Decant TSS mg/L 88

Segregation Threshold

% 39 13 - -

Initial Settled Density (D)

t/m3 1.13 0.51 - 0.48-0.52

Initial Settled Density (UD)

t/m3 1.42 - 0.83 -

Bleed Water m3/t 0.5 1.5 - 0.283

% 44 39 - 14.4

Shrinkage Limit Density

t/m3 1.71 0.92

Yield Stress Pa 3 - - 34

Plastic Viscosity mPa.s 19 - - 84

5.2.2 Beneficiation plant tailings

The testing undertaken by ATCW indicates that the beneficiation plant (Rougher + Cleaner 1)

tailings, are low plasticity sandy silt with maximum grain size of 0.15 mm. The second half of the beneficiation process known as the Cleaner 2 to Cleaner 4 tailings comprise medium plasticity


clay with approximately 40% clay content (< 2 μm). These finer tailings are reported to have

poor settling properties unless blended. Details on the thickener test work, expected solids

concentration, decant clarity and further assessment of the behaviour for these separated

streams can be found in ATCW 2019.

The Beneficiation TSF is now designed to accommodate the combined Rougher + Cleaner 1

and Cleaner 2 to Cleaner 4 tailings via a single thickener and tailings delivery pipeline.

The testing undertaken by GHD concurs with results expected from previous testing, indicating

that the combined beneficiation plant tailings settle out effectively providing a decant quality

suitable for plant reuse. Further geotechnical testing is ongoing to inform detailed design

including additional column testing at the higher solids content expected from thickening to

confirm the assumed settled and dried densities.

Table 5-3 presents the physical characteristics adopted for the purpose of the pre-construction

design.

Table 5-3 Beneficiation tailings assumed physical properties

Design Aspect Design Basis

Pumped Solids Content 52% (see Note 1)

Initial Settled Density 1.1 t/m3

In situ Beach Density 1.5 t/m3

Specific Gravity 3.30 g/cm3

Decant Total Suspended Solids <100 mg/l

Note 1 – Tailings solids content to be between 50% - 55% as advised by Hastings 28th March 2019 based on

thickening test work.

5.2.3 Hydromet tailings

The tailings produced from the Hydromet plant will be in the form of a precipitated residue

comprising approximately 6% of the total process tailings. Additional effluent produced by gas

scrubbing will consist of gypsum residue which forms about 1.2% of the total process tailings.

The combined residue sample assessed by ATCW was considered to comprise a soft, black silt,

with approximately 15% clay fraction. Atterberg limits undertaken by ATCW indicated the

material to have very high plasticity. The material was in the form of a cake at an as received

solids content of approximately 52%. Dilution of the sample to 33% solids content with

neutralisation residue re-leach liquor was undertaken to produce a thickened self-levelling

slurry.

Table 5-4 below presents the hydromet tailings physical characteristics adopted for the purpose

of pre-construction design.

Table 5-4 Hydromet tailings assumed physical properties

Design Aspect Design Basis

Pumped Solids Content 11%

In situ Tailings Density 0.5 t/m3

Specific Gravity 3.16 g/cm3

The Hydromet TSF is designed to accommodate the combined tailings, barren water and brine

effluent. At this stage it is intended that the tailings and effluent would be combined and


deposited via a single common pipeline. Despite the low solids content at the time of deposition, the assumed final settled tailings density of 0.5 t/m3 is still considered to be suitably

conservative for the purpose of preliminary sizing of the facility. In practice it is likely that evaporation will lead to additional densification of the hydromet tailings with a potential to result in higher than assumed final densities.

5.3 Geochemical characterisation

5.3.1 Beneficiation plant tailings

Previous analysis

Tailings solids (TSF 1 and TSF 2)

Previous analysis (ATCW and Graeme Campbell and Associates (GCA)) found tailings to be benign geochemically and non-acid forming (NAF) (ATCW, 2019). However, ANSTO analysis

found that there are enriched concentrations of most metals, in particular Al, Fe and Mn, which reflect that of the ironstone orebody from which they were derived (ATCW, 2019). Tailings solids in Cleaner 2 – Cleaner 4 streams (previously reporting to TSF 2) were enriched in rare earth

elements (REE) and lead associated with the ore body but exist as fixed forms only (ATCW 2019).

Tailings pore water (TSF 1 and TSF 2)

Results for preliminary analysis of the pore water from all tailings streams was alkaline

(pH 10 - 11) compared to a near neutral groundwater pH of 8; and was brackish with a salinity ranging from 1450 mg/l to 2080 mg/l, which is within the same salinity range as the local groundwater (ATCW, 2019). TDS and most metal concentrations in the pore water and

groundwater were comparable. However, the pore water had lower concentrations of Ca and Mg and higher concentrations of As, F, Mo and Si compared to the groundwater. Trajectory and GCA (2017) found that F and Mo were elevated above ANZECC Livestock Drinking Water

Guidelines. ATCW (2019) suggests “the presence of soluble F forms may reflect the small

amounts of fluorites, fluorine bearing micas and/or fluoro-phosphates in the Yangibana ore. The soluble Mo forms may be present as molybdate associated with the phosphates.”.

Samples of tailings solids were subjected to ASLP testing by ANSTO (2017), using both acidic (pH = 5) and alkaline (pH = 9.2) leaching fluids. A detailed analysis of these results is documented in the ATCW FS Preliminary Concept Design Report (ATCW, 2019). The results

showed that, for most elements, there was no significant leaching of any element (< 100 mg/L) or radionuclide from any of the three TSF solids using the acidic or alkaline leach testing fluids. Uranium-238 (0.02 mg/L; 0.25 Bq/L) was found in both the acetate and borate leachates for the

rougher 1 (TSF 1) and cleaner tails (TSF 2) leachates. The acetate and borate leachates extracted 1.9 and 1.3 %, respectively of U-238. The highest concentration of any radionuclide was 0.81 Bq/L for Ra-228 in the acetate leachate for the cleaner tails. ANSTO (2017) concludes

“the concentrations of all measured radionuclides, however, are not considered to be significant”.

Additional leaching and weathering testwork were conducted by Trajectory and GCA (2018) to

assess the solubility behaviour of TSF 1 and 2 solids samples using groundwater obtained from fractured rock and palaeochannel aquifers at the Yangibana Rare Earths Project site and high purity deionised water, as well as humidity cell testing. For TSF 1, approximately 6-7 pore

volumes were passed through the test columns over a period of 15 weeks. The results of the leach study for TSF 1 tailings solids showed that, upon leaching with either High Pressure Deionised Water (HPDW) or locally acquired groundwater under saturated conditions, soluble-F

and soluble-Mo concentrations rapidly decreased and thus confirmed that the recorded soluble-


F and soluble-Mo elevations were mainly associated with tailings process water, and thus would diminish with flushing. For TSF 2, approximately 2-3 pore volumes were passed through test

columns over a period of 15 weeks. The leachate-F and leachate-Mo concentrations trended downwards with similar outcomes to the TSF 1 leach tests but much more slowly due to the nature of the tailings. In summary, this concludes that elevated F and Mo concentrations are not

a long term feature of the tailings leachate (Trajectory and GCA, 2018).

Summary

Table 5-5 summarises the geochemical analysis of TSF 1 and 2 tailings.

Table 5-5 TSF 1 and 2 geochemical analysis summary

Characterisation TSF 1 TSF 2

Solids Liquids Solids Liquids

AMD testing (ATCW, 2019; Trajectory and GCA. 2017)

NAF Circum Neutral/Saline

NAF Circum Neutral/Saline

Suite of multi- elements (ANSTO, 2017; Trajectory and GCA, 2017)

No significant elevations but enriched in Al, Fe and Mn

Elevated F and Mo

No significant elevations but enriched in REE and Pb

Elevated F and Mo

Physical characteristics (ATCW, 2019; Trajectory and GCA, 2017)

Sodic N/A Sodic N/A

Fibrous materials testing (Trajectory and GCA 2017)

None detected N/A None detected N/A

Radionuclide concentrations (ANSTO, 2017)

0.7 Bq/g Not significant; below detection limits

4 Bq/g Not significant; below detection limits

pH 10-11 10-11 10-11 10-11

GHD 2019 supplementary testing

As mentioned in Section 5.1.2, further testing on the combined geochemical characteristics of the Beneficiation TSF has been conducted. Table 5-6 summarises the analysis performed.

Table 5-6 Summary of geochemical test work

Parameter Tailings Solid Pore Water LEAF leach testwork

Net Acid Production Potential (NAPP) X

Net Acid Generation (NAG) X

Kinetic Net Acid Generation (KNAG) X

Acid Buffering Characteristic Curve (ABCC)

X

Total Metals by inductively coupled plasma mass spectrometry (ICPMS) Full Suite

X (mg/kg) X (mg/L) X (mg/L)

Total Mercury X (mg/kg) X (mg/L) X (mg/L)

pH and EC (1:5) (µs/cm and pH Unit)

X X

General Water Suite (mg/L) X


Parameter Tailings Solid Pore Water LEAF leach testwork

Suspended solids (mg/L) X

Combined tailings solids (Beneficiation TSF)

Geochemical Abundance Index

To gain an early understanding of the risk a particular metal may pose to the environment, a comparison between the total metal concentrations (by ICPMS) and their average crustal abundance can be presented as a Geochemical Abundance Index (GAI). This is only a simple,

preliminary method of assessment, as it does not take into account the solubility and mobility of the metals nor their relative toxicity to the receiving environment. A GAI of less than 0 indicates that the content of the element is less than the average crustal abundance. A GAI of 3

corresponds to a 12-fold enrichment above the average-crustal-abundance; and so forth, up to a GAI of 6 which corresponds to a 96-fold, or greater, enrichment above average-crustal abundances. A GAI of 3 or greater is considered significantly elevated (DFAT, 2016).

GAIs were calculated for 28 metals (Ag, Al, As, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, S, Sb, Se, Sn, Sr, Th, Tl, U, V, Zn, Table 5-7), of these 3 (Pb, Se and Th) returned GAIs greater than 3, indicating relatively enriched concentrations. Lead and thorium reported

GAIs slightly above 3 at 3.7 and 3.3 respectively while selenium reported at 7.6.

These outcomes are consistent with previous findings although further analysis will confirm whether or not the REE and Al, Mn and Fe are also elevated.

The high selenium concentrations may be an artefact of spectral interferences during inductively coupled plasma mass spectrometry (ICPMS), because the argon gas used during analysis can provide significant overlaps on all selenium isotopes (Paul, 2016). ALS uses Se78 for ICPMS

analysis, which is known to have interference from krypton (a contaminant of the argon used in ICPMS; Paul, 2016). In addition, Se is below detection limit in the leached samples at a range of pH conditions (see Table 5-8 and Table 5-9) indicating that it is immobile. As a result of low

leached concentrations and known interference of this element during ICPMS it is concluded that high concentrations of selenium reported are an artefact of the analytical process.


Table 5-7 Summary of total metal (ICPMS) concentration and GAI values*

Metals Concentration (mg/kg) GAI Value

Ag 0.7 2.7

Al 3920 -5.1

As 7.8 1.5

B <50 0.7

Ba 1020 0.6

Be 3.4 -0.5

Bi 0.3 0.2

Cd 0.2 -0.7

Co 12.8 -1.6

Cr 58.5 -1.4

Cu 25 -1.8

Fe 43600 -2.9

Hg <0.1 -1.3

Li 17.7 -0.8

Mn 3210 1.1

Mo 4.7 1

Ni 33.4 -1.8

Pb 255 3.6

S <0.01 (%) -3.5

Sb <0.1 -2.7

Se 16 7.6

Sn 3.4 -1.5

Sr 58.1 -3.4

Th 153 3.3

Tl 0.8 0.2

U 8.4 1

V 20 -3.4

Zn 86.6 -0.4

*sourced from lab report ES1907149 Appendix C.

Acid Base Accounting

To provide additional assessment, the sample underwent AMD tests, comprising net acid

generation (NAG), net acid production potential (NAPP - comprising total sulfur and acid

neutralising capacity), kinetic net acid generation (KNAG) and acid buffering characteristic curve

(ABCC) tests (AMIRA 2002). The results are consistent with previous findings.

Total sulfur and Maximum Potential Acidity (MPA)

The total sulfur reported at below detection limit (<0.01 %). The sample returned an MPA value

of 0.15 kg H2SO4/t, determined using half the detection limit of sulfide. An MPA greater than

10 kg H2SO4/t is typically considered to represent a significant AMD risk if there is no

neutralising capacity (Table 5, DITR, 2016).

Acid Neutralising Capacity (ANC)

The sample reported a titrated ANC value of 7.3 kg H2SO4/t. This indicates that the material has

some limited neutralising capacity.


Net Acid Producing Potential (NAPP)

The NAPP, determined using half the detection limit of sulfide, was -7.1 kg H2SO4/t.

Consequently, the sample may be classified as non-acid-forming (NAF) using NAPP results

only.

Neutralising Potential Ratio (NPR)

The NPR, determined using half the detection limit of sulfide, reported at 47.7, which is

significantly larger than the AMIRA (2002) guide of a minimum NPR of 2.0 as a factor of safety

for self-neutralising material.

Net Acid Generation (NAG)

Net Acid Generation (NAG) results were in agreement with the NAPP results and showed a very

low risk of acid generation. The oxidation values was 8.9, above 4.5, the value considered as

acidic (AMIRA, 2002). The initial pH value was also highly alkaline with a pH of 10.1.

Kinetic Net Acid Generation (KNAG)

The kinetic NAG (KNAG) test returned a final pH value (9.08) that was reflective of the NAG test

(8.9). At no point during the test did the pH decrease and thus did not reach a pH of 4.5, the

value considered as acidic (AMIRA, 2002).

The sample reported a pH increase throughout the test, though it is most noticeable at

approximately 150 minutes, this is paired with the peak temperature for the test, reaching

74.6°C. This indicates the presence of slow reacting neutralising potential.

Acid Buffering Characteristic Curves (ABCC)

The acid buffering characteristic curves (ABCC) test involves the slow titration of a sample with

acid while continuously monitoring pH. These data provide an indication of the portion of ANC

within a sample that is readily available for acid neutralisation. The titrated ABCC value at pH

4.5 (3.9 kg H2SO4/t), is lower than the initial static ANC values (7.3 kg H2SO4/t). The ABCC

derived acid neutralising capacity shows that the static ANC values have, overestimated the

acid neutralising capacity of the samples, however even with the reduced ANC the sample still

classifies as NAF.

LEAF Test method 1313

Additional leach testing of the combined beneficiation tailings was undertaken to further

understand the differences in the leach behaviour. The Leaching Environmental Assessment

Framework (LEAF Procedure) test method 1313 was performed, which determines how

liquid- solid partitioning varies with the pH of the leaching solution using a parallel batch

extraction procedure (DER, 2015). Results of nine pH conditions were produced (13, 12,

10.5, 9, 8, 7, 5.5, 4 and 2). The available pH conditions cover both the extreme range for

LEAF leaching 2 -13 and provide details on pH levels closer to site conditions (12 and 10.5).

LEAF testing is recommended by EPA Western Australia (DER, 2015) and has been

requested by DWER.

The following is a brief summary of the LEAF method 1313 from US-EPA (2017):

“This method consists of nine parallel extractions of a particle-size-reduced solid material

in dilute acid or base and reagent water. A schedule of acid and base additions is

formulated from a pre-test titration curve or prior knowledge indicating the required

equivalents/g acid or base to be added to the series of extraction vessels so as to yield a

series of eluates having specified pH values in the range of 2-13. In addition to the nine

test extractions, three method blanks without solid samples are carried through the

procedure in order to verify that analyte interferences are not introduced as a

consequence of reagent impurities or equipment contamination. The 12 bottles (i.e., nine


test positions and three method blanks) are tumbled in an end-over-end fashion for a specified contact time, which depends on the particle size of the sample. At the end of the specified contact interval, the liquid and solid phases are roughly separated via

settling or centrifugation. Extract pH and specific conductivity measurements are then made on an aliquot of the liquid phase and the remaining bulk of the eluate is clarified by either pressure or vacuum filtration. Analytical samples of the filtered eluate are collected and preserved as appropriate for the desired chemical analyses. The eluate concentrations of constituents of potential concern (COPCs) are determined and reported. In addition, COPC concentrations may be plotted as a function of eluate pH

and compared to QC and assessment limits for the interpretation of method results.”

Given the leaching procedure’s relatively aggressive nature (similar to the ASLP test with a prolonged period of agitation which encourages reactivity) and the potential for dilution in the environment, a dilution factor of 10 can be applied to the LEAF results when considering their environmental significance (WADEC, 2009).

Western Australia has developed unlined landfill acceptance criteria (WADEC, 2009) for Class I and Class II materials, which includes inert materials and clean fill. These guidelines are based on the 2011 Australian drinking water guidelines (ADWG) multiplied by a factor of

10. As inert landfill materials and clean fills use a factor of 10 when compared to guidelines

it is appropriate for the conservative LEAF leach results to use a dilution factor of 10.

Results can otherwise be interpreted as exaggerated and should therefore be understood with the nature of the testing in mind, i.e. to flag the risk of metalliferous drainage being

generated from the samples.

The LEAF tests results were assessed against the ANZECC and ARMCANZ (2000) stock watering guidelines and the NEPM (2013) groundwater investigation levels

(GILS).

ANZECC and ARMCANZ Livestock guidelines

The plant filtrate has a pH of 11.8, which is most similar to the LEAF test T02 (pH 12). The results from T02 reported no exceedances of the guidelines at the leach pH of 12 indicating that

conditions in the combined beneficiation pore water will be below the ANZECC and ARMCANZ (2000) livestock guidelines (Table 5-8).

Results for T01 (pH 13) and T03 (pH 10.5) represent the next closest alkaline and acidic

conditions to the current conditions of pH 11.8. These leaches do have exceedances for Al, and Mo for T01 (15.7 mg/L and 0.064 mg/L) and Mn for T03 (2.35 mg/L). The exceedances are still less than 10 times the livestock guidelines, which considering the aggressive nature of the

leaching further demonstrates the benign nature of these tailings under this pH range.

The LEAF test T09 (pH 2) showed the greatest exceedances (Al, Mn, Se and U), however these extremely acidic conditions are highly unlikely to occur within the beneficiation tailings or in

surrounding groundwater (average pH 8.02; ATCW, 2019).

Figure 5-1 shows the concentration changes of analytes at different pH levels. The majority of metals have higher concentrations under acidic conditions, hyper alkaline pHs of 12 and 14

show the lowest concentrations for Cd, Co, Cu, Mn, Ni, Se and Zn. Aluminium, As, U and Cr are amphoteric with the lowest concentration at neutral pH. Molybdenum, reports an increasing concentration with increasing pH. Mercury is at detection limit across the range of pH

conditions. This suggests that an alkaline pH results in lower concentrations for most metals.

Calcium and Mg report at detection limit (<1 mg/L) for the majority of leaches and blanks. Ca and Mg report values at leaches T06 and T09 (pH 7 and 2, respectively) though these are low

and don’t exceed the livestock guidelines for Ca or Mg.


NEPM Groundwater Investigation Levels

The T02 leach (pH of 12) analysis shows exceedances of the NEPM freshwater guideline

values for three analytes (Cr, Cu and Ag) but has no exceedances for the NEPM drinking water guidelines (Table 5-9). Of those three exceedances, Ag is reporting at detection limit (<0.001 mg/L), which is higher than the guideline value (0.00005 mg/L). Given Ag reports at detection

limit in all leaches this should be treated as a quality issue and is of low risk. Copper reports at 0.002 mg/L, which is lower than the blank leach B03 (pH 13) at 0.005 mg/L indicating the exceedance is likely caused by the reagents or equipment. Chromium is reporting at the

guideline value 0.001 mg/L, which is also the detection limit value. Thus the metal concentrations at T02 leach conditions are considered low risk. In summary, when taking quality control, reagent and equipment contamination issues into account, the T02 leach results show it

is benign in nature and unlikely to pose any risk to the environment.

Results for T01 and T03 (pH 13 and 10.5) show exceedance but all are less than ten times the guidelines with some exceedances being caused by reagent and equipment contamination (i.e.

Cu, Pb and Zn).

Figure 5-1 Metal concentration at varying LEAF pH conditions


Table 5-8 LEAF leach and pore water compared to ANZECC and ARMCANZ livestock guidelines (2000)


Table 5-9 LEAF leach and pore water compared to NEPM drinking water and fresh water guidelines (2013)


QA/QC method blanks and effects of the reagents

Three method blanks without the beneficiation solids (B01 pH 7, B02 pH 2 and B03 pH 13) were

also ran with the LEAF leach tests to determine if reagent or equipment contamination has caused any of the resulting analyte concentrations. Analytes Al, Cu, Mn, Mo, and Zn had concentrations above the detection limit in the blank samples indicating a low level of

contamination. Some of these also exceeded the NEPM guidelines (B03 Al at 0.17 mg/L and Cu at 0.005 mg/L).

There are higher levels of Na and K reported at the higher pH leaches (13 and 12) caused by

the use of potassium hydroxide (KOH) or sodium hydroxide (NaOH), i.e. due to it being the base used to achieve higher pH leaches.

Combined pore water (Beneficiation TSF)

Plant filtrate results

The plant filtrate results were assessed against the ANZECC and ARMCANZ (2000) stock watering guidelines and the NEPM (2013) groundwater investigation levels (GILS), where applicable (Table 5-8 and Table 5-9).

The plant filtrate results reflect the current conditions expected in the combined beneficiation liquid. The filtrate reported a pH of 11.8 and an EC of 5220 µs/cm. The livestock and NEPM guidelines do not have values for EC but values at that level are still considered suitable for long

term irrigation (100 years) of specific crops (barley, wheat, cotton safflower, sorghum; ANZECC and ARMCANZ, 2000).

Chloride reports at 285 mg/L, which also has no livestock or NEPM guidelines. It is, however,

within the range for long term irrigation of moderately tolerant to tolerant crops (ANZECC and ARMCANZ, 2000). Sulfate concentration is reported for the plant filtrate at 182 mg/L which does not exceed the livestock or NEPM guidelines (1000 and 500 mg/L).

Fluorine concentrations (2.6 mg/L) exceeded the livestock guidelines (2 mg/L) and the NEPM drinking water guideline (1.5 mg/L), though once environmental dilution factors are considered this is not significant. Previous testing found that fluorine concentrations diminished with flushing

and were not a long term effect (Trajectory and GCA, 2018)

Total dissolved solids reported at 3390 mg/L, which is below the upper range for livestock (5000 mg/L). Alkalinity tests by PC titrator found the majority came from hydroxide at 703 mg/L

followed by Carbonate at 213 mg/L with bicarbonate concentrations at detection limit.

Recycled process water

The plant filtrate tests characterise the initial conditions onsite, it does not identify whether repeated recycling of process water would increase concentrations of key elements Mo and F. A

review of the recycled process water quality has been undertaken by Hastings to determine if the predicted decrease in Mo and F concentrations due to flushing would be impacted by recycling. The full report and results from this review can be found in Appendix C.

Locked cycle test work ran for a total of 15 cycles with Mo and F recorded in the final 3 cycles. The concentrations for F were greater than in the plant filtrate tests with a final value of 4 mg/L compared to 2.6 mg/L. Fluorine concentrations exceed the livestock guidelines (2 mg/L) and the

NEPM drinking water guideline (1.5 mg/L). The final three cycles show similar concentrations in F suggesting stabilisation in F concentrations.

The final Mo concentration reported at 2.5 mg/L, which exceeds both the livestock and NEPM

drinking water guideline (0.05 mg/L). Molybdenum also appears to stabilise with the final three cycles showing no significant increasing trends.


The test was designed under locked cycle conditions, however the current water modelling for the site indicates that in steady state the process will operate on a mix of 80:20 recycled water

to fresh raw water. This is expected to produce lower concentrations of Mo and F due to the addition of the fresh raw water.

There were other minor exceedances for Cd, Cr, Cu, Al, Ag, Pb, Zn and Ni, though most of

these were caused by detection limits exceeding the guideline limit (Cd, Cr, Pb, Ni and Ag). Previous testing performed by ATCW and GCA (2018) did not highlight these metals as significant in the decant water.

Summary

In conclusion, an additional complement of geochemical testing has been conducted on a combined beneficiation tailings sample, representative of the tailings stream reporting to the Beneficiation TSF. The additional tests confirm previous findings and verify the characterisation

of the combined beneficiation tailings streams:

The beneficiation TSF solids report below a GAI of 3 for the majority of metals, except for

Pb and Th, though these are shown to have low concentrations (not exceeding the

guidelines or at detection limit) in the T02 leach liquid indicating that the metals are not

mobile at current pH conditions.

The solids can be classified as NAF with alkaline pH and saline EC concentrations.

Leaf leach T02 (closest pH conditions to pore water 11.8 pH) had no significant

concentrations of analytes compared to the ANZECC and ARMCANZ livestock guidelines

(2000) and the NEPM fresh water and drinking water guidelines (2013).

Plant filtrate initially and recycled had no significant concentrations of analytes compared to

ANZECC and ARMCANZ livestock guidelines (2000) and the NEPM fresh water and

drinking water guidelines (2013) except for fluorine and molybdenum. Minor exceedances

in Al, Cu and Zn were observed. Potential management solutions are recommended in

Section 6.4.3.

Table 5-10 summarises the geochemical characteristics of the solids and liquids reporting to the

Beneficiation TSF. This aligns with the previous TSF 1 and 2 geochemical characterisation as expected.

Table 5-10 Summary of Beneficiation TSF characterisation*

Characterisation Beneficiation TSF

Characterisation Solids Liquids

AMD testing NAF Alkaline/Saline

Suite of multi-elements No significant elevations Elevated F and Mo

Physical characteristics Sodic N/A

Radionuclide concentrations 0.8 Bq/g Not significant; below detection limits

pH 10.1 11.8

*Summary based on geochemical lab results Appendix C.

5.3.2 Hydromet plant tailings

Previous analysis

TSF 3 solids (Plant Residue and Scrubbing Effluent)

Testing by ANSTO confirmed that hydromet tailings were also NAF (ATCW, 2019). Elemental assays on the TSF 3 tailings, comprised of hydrometallurgy plant tailings and scrubbing effluent,


indicated relative enrichment (compared to the beneficiation plant tailings) in Ba, Cr, Ni, Pb, Th, U, Ca, P and S and relative depletion was evident in Al, Cu, Mn, V, Zn, Fe, K, Si and Ti. The

material is circum neutral (pH 6.6) and radionuclide concentrations are 32.4 Bq/g (ANSTO, 2017). No solids reported to the evaporation pond.

TSF 3 and evaporation pond liquor

The tailings pore water from the hydrometallurgy process, reporting to TSF 3, is circum neutral

(pH 6.6). The pore water contains levels of Mg, and SO4 which are several times in excess of the ANZECC Livestock Water Quality Guideline (Trajectory and GCA 2017). TDS is higher than background groundwater at 12,000 mg/L compared to between 1400 mg/L and 2800 mg/L. The

residue is lower in Na, Si, Cl-, F-, NO3-, higher in Ca and Mn and of similar concentrations in Al and B compared to groundwater.

The barren liquor reporting to the evaporation pond is neutral (pH 7) and is expected to be

largely magnesium sulfate and ammonium sulfate solution with elevated concentrations of NH4, Mg, S and SO4 compared to groundwater (R Zhang, 2019, personal communication; ATCW, 2019). Ammonium bicarbonate is used to precipitate REEs from solution, after precipitation

nearly all NH4 reports to the evaporation pond liquor at concentrations estimated at 18g/L (R Zhang, 2019, personal communication).

The liquor is lower in Na, higher in Ca, Mn and F and of similar concentrations in Si compared to

groundwater. Due to the neutralisation of the residue, the pH will be 7 compared to a background groundwater pH of 8.

ASLP testing was also undertaken on TSF 3 solids as per that described in Section 5.3.1 for the

tailings pore water (TSF 1 and 2; ANSTO, 2017) and resulted in the same outcomes: Low concentrations of radionuclides (not considered significant by ANSTO, 2017) and no significant leaching of any element (ANSTO 2017).

Summary

Table 5-11 summarises the geochemical analysis outcomes of solids and liquids reporting to the evaporation pond and TSF 3.

Table 5-11 Evaporation pond and TSF 3 geochemical analysis summary*

Characterisation Evaporation pond TSF 3


pH and TDS N/A Circum Neutral/Saline NAF Circum Neutral/Saline

Suite of multi- elements/Salts

N/A Elevated Mg, Mo, S, F, NH4 and Co

No significant elevations

Elevated Mg, SO4, S and Mo

Physical Characteristic N/A Will evaporate to a salt Sodic N/A

Fibrous materials testing N/A N/A None detected N/A

Radionuclides N/A None Detected 32.4 Bq/g None detected

pH N/A 7 6.6 6.6

*Summary based on geochemical lab results, Appendix C, ATC Williams (2019) and ANSTO

(2017).GHD 2019 analysis

GHD 2019 analysis

Solids (Hydromet TSF)

The solids component does not vary from that of the previous TSF 3 solids. As a result, no

further assessment of the Hydromet TSF solids has been undertaken and will be consistent with that previously determined (as described in Section 5.3.2 TSF 3 solids above).


Combined liquor (Hydromet TSF)

Previous analysis of the TSF 3 and evaporation pond liquors were used to determine the

combined Hydromet TSF liquor mass balance, which was used to predict concentrations of key analytes (i.e. F, Mo, Mg, NH4, SO4, U and Th) known to be elevated in this facility. The mass balance is based on the assumption that little to no reactivity will occur and is only an indication

of possible characterisation.

However, it should be noted that ammonia gas may be produced in small quantities due to the reaction between caustic soda from the gas scrubber waste and ammonium sulfate from the

evaporation pond liquor. Hastings commissioned an air emissions study (ERM, 2019, Appendix

I) that involved dispersion modelling based on estimates of ammonia gas evolution under “worst

case conditions”. This confirmed low risk of both onsite and offsite exceedances as discussed in

Section 9.7.

The mass balance (Table 5-12) shows that the concentrations of key analytes in the evaporation pond liquor have been diluted slightly by combining the two facilities (TSF 3 and

evaporation pond) into the Hydromet TSF.

Verification of the geochemistry of the TSF 3 pore water will be completed upon operations of the TSF. Regardless, the use of liners and underdrainage to encapsulate these tailings provides

contingency if there is variation in our current understanding of the geochemistry.

Table 5-12 summarises the original mass and concentrations of the separate liquors and the potential concentrations when combined.

Table 5-12 Mass balance of Hydromet TSF*

Source Mass (t) F (mg/L) Mo (mg/L)

Mg (mg/L)

SO4

(mg/L)

U

(mg/L)

Th (mg/L)

TSF 3 liquor 114,155 0.5 0.5 3,050 15,900 0.5 0.5

Evaporation pond liquor

434,500 5 0.5 6,721 30,000** 0.5 0.5

Combined Hydromet TSF liquor

548,655 4.1 0.5 5,957.2 27,066.3 0.5 0.5

*TSF 3 liquor and evaporation pond liquor values sourced from reports ATC Williams (2019) attached in

Appendix C.

**Estimated upper limit, detection limits reported as half for the calculation.

Summary

In summary, no further geochemical analysis has been conducted on a combined Hydromet TSF sample, however both TSF 3 and Evaporation pond liquids have similar characteristics:

pH is circum neutral in both

Both have elevated Mg, S and Mo content and similar concentrations of Na and Ca

Given the above similarities, it is unlikely that combining the two streams will cause any reactivity of chemicals aside from the ammonium hydroxide, at a high pH.


Table 5-13 Summary of Hydromet TSF 3 characterisation

Characterisation Hydromet TSF

Solids Liquids

AMD testing Suite of multi-elements/Salts

NAF No significant elevations expected

Circum Neutral/Saline

Elevations in Mg, NH4, S, SO4 Mo and F.

Physical Characteristic Sodic N/A

Fibrous materials testing None expected N/A

Radionuclides 32.4 Bq/g Insignificant levels expected

pH Expected to be between 6.6 and 7

Expected to be between 6.6 and 7

5.3.3 Conclusion

In conclusion, the Hydromet TSF contains elevated MgSO4 and thus the liner system provides

controls for the containment and encapsulation of these salts. The Beneficiation TSF tailings

solids are benign, i.e. unlikely to leach any significant concentrations of elements and are non-

radioactive. Table 5- summarises key elements in each TSF.

Table 5-14 Summary of key analytes for the TSFs*

Key element Beneficiation TSF Expected Hydromet TSF


Fluoride - 2.6 mg/L - 4.1 mg/L

Molybdenum 4.7 0.037 mg/L 161 mg/kg <1 mg/L

Radionuclides 0.8 Bq/g - 33 Bq/g -

U Th

U = 8.4 mg/kg Th = 153 mg/kg

U = 0.002 mg/l Th = <0.001 mg/L

U = 104 mg/kg Th = 7,623 mg/kg

U = <1 mg/L Th = <1 mg/L

Mg - <1 mg/L 5,406 mg/kg 5,957 mg/L

SO4 (S = <0.01 %) 182 mg/L (S = 9.3 %) 27,066.3 mg/L

*Summary based on geochemical lab results, Appendix C, ATC Williams (2019) and ANSTO (2017).


6. Design development concept6.1 General arrangement

The proposed general arrangement for the tailings facilities takes advantage of the natural

topography where a number of small gullies are formed between subtle rises at ground level.

These gullies are utilised to form the respective Beneficiation and Hydromet TSF embankments.

Initial starter dams are constructed to meet capacity requirements for the initial few years of

operation. Embankment raising can be completed by downstream construction methods.

Both the Beneficiation and Hydromet TSFs are kept within a single compact footprint by utilising

a common shared dividing wall between the two facilities. This minimises the overall area of

disturbance associated with tailings management at the site and minimises construction cost

and borrow pit requirements. There is also potential for the economical construction of a low

height dividing embankment within the Beneficiation TSF to create a small separate cell for the

Cleaner 2, 3 and 4 tailings (see location Figure 3-2).

The proposed TSF site impounds two adjacent gullies where there are respective watercourses

feeding into the downstream Fraser Creek tributary. During operations, any stormwater that falls

within the tailings dams will be contained and managed onsite and the upstream catchment will

be diverted around the TSF by constructing a new diversion channel.

At closure the TSF will be shaped and capped according to the final landform design with

excess stormwater able to be safely discharged back to the surrounding creeks via a series of

drains formed within the final TSF landform.

Figure 6-1 presents the Pre-Construction Design general arrangement for the TSF.

Figure 6-1 General arrangement of TSFs (after 3 years)

Beneficiation TSF

Hydromet TSF


6.2 Concept details

6.2.1 Beneficiation TSF

The Beneficiation TSF requires the construction of an initial starter embankment, 6.5 m high at

maximum section to accommodate the first three years of production. Extension of the TSF after three years involves raising the perimeter embankments by approximately 4.5 m over the mine life. Adjustments also need to be made to the decant tower and access causeway including

relocation to its final southern location at the end of the mine life.

The proposed arrangement allows for spigotted perimeter discharge from the Beneficiation TSF embankment crest as well as elevated areas to the east and south. This will reduce the risk of

density variability or bleed water runoff affecting the beach slope and assist in beach development to create a central decant pond location.

For the proposed arrangement, a steep beach slope is not critical so there could be an option

for reduced thickening. However, due to the importance of water recovery, the TSF design assumes thickening of tailings. As such, there may be a need to control beach slope by spigot extension during operations and adopting elements of CTD in order to effectively fill the storage

and achieve a safe profile at closure.

To maximise water recovery and minimise spill risk, beaching of tailings will be directed at developing a pond located at the centre of the TSF and decanted using a central tower. The aim

is to remove water as quickly as possible with the intent to operate the TSF pond to the minimum size that is necessary to ensure water clarity for plant reuse.

Dusting from the tailings beach will be minimised by implementation of a rotational discharge

plan to apply tailings regularly in thin layers. The dust control plan will also incorporate a plan for contingency irrigation of dry beach areas as well as the application of dust suppressant chemicals as required.

6.2.2 Hydromet TSF

The Hydromet TSF requires the construction of an initial starter embankment, which will be 6 m maximum height to accommodate the first three years of production. Additional capacity after the initial three years is achieved by raising the perimeter embankment by approximately 3 m to

its ultimate height, which will provide sufficient capacity for the remaining mine life.

Due to the unsuitable water quality for plant reuse, there will be no water recovery from the Hydromet TSF. Rather, the Hydromet TSF will operate as an evaporation facility with adequate

freeboard to contain stormwater inflows without spill for a 1:100 AEP, 72 hr rainfall event.

Based on the expected low percentage solids of the combined Hydromet stream, a single point tailings discharge is envisaged.

Combining the Hydromet waste streams results in reduced dust risk from the original TSF 3 concept which relied on transfer of barren liquor from the evaporation pond and reduces the risk of low density waste, hence allowing a more simplified underdrainage system.

Due to the high sulphate nature of the Hydromet water the facility will require a lining system. The combined facility allows well proven liner technology using a combined compacted clay and HDPE liner system (i.e. geocomposite lining system).


6.3 Water management

The Beneficiation TSF decant area will capture tailings bleed water and incidental run-off from

the catchment area associated with the TSF. This water will be returned to the process water

circuit via a water treatment/filtration plant for re-use.

The pumps required for the decant tower have been sized to allow for the expected runoff from

the initial settlement of the material allowing for expected evaporation and seepage into the

deposited tailings profile as per Table 6-1 below.

Table 6-1 Beneficiation decant recovery

Parameter Beneficiation TSF Unit

Production Solids 975,000 t/annum

Assumed Slurry Solids Content (Refer Note 1) 52 %

Assumed Initial Settled Density 1.1 t/m3

Assumed In Situ Dry Density (Desiccated) 1.5 t/m3

Annual Water in Slurry 900,000 m3/annum

Annual Volume Water Retained Following Initial Settlement

590,000 m3/annum

Annual Volume Water Released Following Initial Settlement (excludes evaporation loss)

310,000 m3/annum

Assumed Pond Depth 1 m

Pond Surface Area 31,000 m2

Pond Evaporation 49,000 m3/annum

Pond Seepage 35,000 m3/annum

Estimated Annual Decant Return (Refer Note 2) 120,000 m3/annum

Estimated Required Pump Capacity Range 25 - 50 m3/hour

Estimated Annual Loss to Tailings Deposit (Refer Note 2)

780,000 m3/annum

Note 1 – Tailings solids content as advised by Hastings 28th March 2019 based on thickening test work.

Note 2 – Settlement testing of combined beneficiation tailings is still ongoing. Estimated annual decant return assumes

50% loss due to evaporation from active beaches. This is to be confirmed in detailed design and final water balance

modelling.

Bleed water from the Hydromet TSF tailings will not be of sufficient quality to re-use as process

water and will remain in the impoundment during operation, to assist in dust prevention. Water

balance calculations indicate that due to the low discharge rate and high evaporation, a

significant decant pond will not form in the TSF.

Emergency spillways are proposed for both TSF impoundments at locations where they can be

cut into natural ground to ensure durability of the structure. The Hydromet TSF spillway will be

cut into the natural rock in an orientation allowing it to spill into the Beneficiation TSF,

minimising the environmental spill risk. The storage capacity of each TSF is conservatively

sized to ensure any spillway operation is a remote possibility.

The proposed TSF site impounds two adjacent gullies where there are respective watercourses

feeding into the downstream Fraser Creek tributary. During operations, any stormwater that falls

within the tailings dams will be contained and managed on-site, and the upstream catchment

will be diverted around the TSF by constructing a new diversion channel as indicated below in

Figure 6-2. At closure the TSF will be a capped according to the final landform design with any

excess stormwater able to be safely discharged back to the surrounding creeks via a series of

engineered drains formed within the final TSF landform.


Figure 6-2 Watercourses and catchment area division around TSF site

6.4 Environmental risk and mitigation measures

Some aspects of the physical, geochemical and radiological properties of tailings and waste

water produced during processing plant operations are different to those of in situ soils and

groundwater. The potential for environmental degradation as a result of release of solids or

wastewater from their designated storage areas must be considered, and appropriate measures

put in place to minimise the likelihood and consequence of such release.

The principal mechanisms by which environmentally harmful materials could be released are:

Containment failure and spill risk

Dust generation (including radionuclide deportment)

Mobilisation of dissolved contaminants and high salinity liquor via seepage to groundwater

or surface water

Mitigating measures to prevent such releases to the extent that they could have an adverse

effect on the surrounding environment, are incorporated in the design and proposed operation

of the facilities. These measures are detailed below.


6.4.1 Containment failure and spill risk

The tailings containment embankments have been designed specifically to prevent the

uncontrolled release of tailings and water from the TSF area and the facility location selected to

maximise natural topographic containment. Contingency measures to cater for extreme floods

and earthquakes have also been incorporated in the design.

The likelihood of containment failure is therefore very low since the consequences of such

failure have been considered and ameliorated in the consequence-based design process.

6.4.2 Dust management

Generation of dust from drying tailings beaches presents a potential environmental and health

risk, particularly for the case of the Hydromet TSF, where elevated radionuclides are present in

the tailings. The design and operational arrangement of both TSFs reduces the risk of dust

generation by:

The presence of continuous containment embankments elevated above the tailings

surface, will tend to break up wind flow and trap particles within the storage.

The presence of strong inter-particle forces due to the extremely fine grain size and

cohesive nature of the tailings.

Maintaining damp moisture conditions at the surface of tailings by frequent discharge of

layers in the beneficiation TSF and by combining spent liquor with tailings in the hydromet

TSF.

If dry surface conditions develop between tailings layer applications, Beneficiation TSF decant

water will be used to irrigate dry areas. Water will be applied using a low-ground pressure (LGP)

water cart developed to traffic on dry areas of the TSF.

A contingency plan for dust suppression in the event of prolonged dry conditions, such as plant

breakdown or temporary shutdown will include the application of dust suppressant chemicals

using the LGP water cart.

6.4.3 Groundwater seepage mitigation

The key identified risks associated with seepage from the TSFs include:

Impacts associated with contamination of downstream surface water receptors including

Fraser Creek

Impacts associated with the contamination of the groundwater aquifer below the TSF

potentially restricting the use of this water resource into the future

For the previous FS concept design, the likelihood of seepage from the TSFs or evaporation

pond coming into contact with groundwater or surface water external to the facilities was

considered to be very low (ATCW 2019). Conceptual seepage modelling completed by GHD for

the refined TSF arrangement supports this assessment (refer Seepage Analysis, Section 9.4).

Importantly, potentially environmentally harmful species contained in the tailings solids

(including radionuclides) have been assessed to be fixed or immobile, therefore the risk of

adverse environmental effects associated with seepage is primarily governed by the seepage of

transport water.

Dissolved materials in the tailings process liquor identified at concentrations above the NEPM or

ANZECC guideline values and /or local groundwater concentrations are detailed in Table 6-2.


Table 6-2 Tailings liquor concentrations exceeding reference values

Facility Exceeding Analyte

Beneficiation TSF Fluoride (F) Molybdenum (Mo) pH

Hydromet TSF Fluoride (F) Magnesium Sulphate (MgSO4)

Fluoride levels are above the livestock watering guideline concentration of 2 mg/l, as are

concentrations measured in the regional groundwater bores, generally being between 2 mg/l

and 3 mg/l.

The livestock watering guideline concentration for Molybdenum is 0.15 mg/l. Molybdenum

concentrations in the regional groundwater bores are below the guideline concentrations,

generally below 0.03 mg/l. Concentrations measured in the beneficiation tailings exceed

guideline limits.

Magnesium Sulphate as a compound is generally not considered a hazardous substance.

Notwithstanding this, the associated TDS and sulphate concentrations in the Hydromet TSF

combined liquor are elevated above the respective livestock watering guideline concentrations

of 5000 mg/l and 1000 mg/l, respectively.

Mitigating conditions and measures to prevent environmental impact associated with seepage

include:

Maintaining unsaturated beaches and a small central decant pond within the Beneficiation

TSF to minimise seepage and increase the offset between the pond and potential

downstream receptors.

Selecting TSF locations where the inferred foundations comprise in excess of 45 m of

unsaturated, low-permeability materials will provide an effective aquitard between ground

surface and the confined aquifer (ATCW 2019). Any small rates of seepage would be

subject to dilution by groundwater flow within the aquifer.

Analysis shows that the development of a wetting front below the decant pond is localised

and is not anticipated to significantly extend laterally beyond the footprint of the TSF.

Leaching of metals from the tailings solids is not anticipated based on testing.

A high standard geocomposite liner system is included in the design of the Hydromet TSF.

Groundwater monitoring provisions are incorporated in the design and operating plan for

the facilities.

The TSF will be closed as a capped facility. The very low rainfall and high evaporation

climate should ensure negligible rates of infiltration and long term seepage from the facility.

In addition, the Hydromet TSF cover system incorporates a geosynthetic liner to further

minimise infiltration and seepage risk.

Detailed design for proposed TSF will include additional geotechnical investigations and

verification of the conceptual hydrogeological model and seepage modelling undertaken for the

concept design. Additional mitigation measures that could be considered (if required) in detailed

design include:

The treatment of any identified preferential seepage paths between the TSF and

downstream receptors using a barrier system such as cement grouting or the construction

of a cut-off wall.

Contingency interception systems such as trenches or recovery bores.


Additional lining below the proposed pond location within the Beneficiation TSF.

Geosynthetic lining of collection drains within the final TSF landform to further reduce long

term seepage rates.

6.5 Closure and rehabilitation concept

6.5.1 General requirements

The closure plan for the Yangibana TSFs will be similar to that already described in the ATCW

FS Concept Report (ATCW 2019). Closure will conform with DMIRS guidelines to develop a final landform that is:

Physically safe to humans and animals

Geotechnically stable

Geochemically non-polluting/ non-contaminating

Capable of sustaining an agreed post-mining land use

Decommissioned and rehabilitated in an ecologically sustainable manner

6.5.2 Closure design

Based on the geometry and expected condition of the TSFs at completion of operations and taking into account the geochemical and radiological characteristics of the tailings materials, the

conceptual closure methodology is summarised below. This is consistent with that presented in ATCW 2019 which GHD considers to be appropriate.

Figure 6-3 and Figure 6-4 show the general arrangement envisaged following closure as well as

the conceptual capping sequence proposed for the respective TSFs. The closure concepts illustrated in this report have been developed in line with the Landform Evolution Study undertaken by Trajectory as documented in Table 6-3.

Table 6-3 TSF closure specification

Specification Consideration in TSF Design

Maximum 40 m lift height (provides conservatism against model).

The maximum height of either TSF is approximately 9m and 11m respectively.

Average slope angle 17.5 degrees. During operation and leading into closure the downstream batters will be re-profiled to 15 degrees in the lower 50% and 20 degrees in the upper 50% ensuring an average slope angle of 17.5 degrees.

20 degrees in upper 50% of Slope and 15 degrees in lower 50% of slope

During operation and leading into closure the downstream batters will be re-profiled to 15 degrees in the lower 50% and 20 degrees in the upper 50% ensuring an average slope angle of 17.5 degrees.

Hydrology measures to PMP required to limit run-on from top surface or berms to batters below. Nominal 1 m crest bund.

Cover according to landform design objectives. Operational TSF pond will be removed via construction of a spillway/channel into bedrock. Drains in final TSF landform can safely discharge any excess stormwater, engineering to withstand/avoid scour in long term.

Cell bunding of 0.7 m and perimeter bunding of 1 m. Infiltration + Evapotranspiration > 100% of incident rainfall on flat surfaces.

To be detailed in Mine Closure Plan as required.


Specification Consideration in TSF Design

Berms for 20 m high batters (Bald Hill) are 20 m wide after reprofiling.


0.5 m high bunds at 10 m offset from final toe position. Cross bunds installed where natural ground at gradient greater than 2 degrees.


Rip lines on contour and minimum 0.5 m deep and 1 m wide at base of windrow.


40% of exposed surface comprised of durable fraction equal to or greater than gravel.


Armouring subsoils spread at 150 – 200 mm over reprofiled waste rock. 20% of final exposed surface after 3-year stabilisation period will be gravels/cobbles from the soil.


Minimum 2 m of in situ or imported durable armouring granite waste rock over embankments after final reprofiling.

The embankment will be constructed using mine waste rock with a minimum 2 m cover used in the reprofiling of the TSFs to meet the slope specifications noted above. Planning to be detailed in Mine Closure Plan.

Provenance seed mix of grasses, shrubs and woody plants.

To be detailed in Mine Closure Plan.

Include introduction of biological matter and soil inoculants in revegetation process.


Provenance seed mix of grasses, shrubs and woody plants.


Beneficiation TSF

The final geometry of the Beneficiation TSF will allow for safe drainage of any excess stormwater to a spillway channel cut through natural ground to the south. The tailings surface will be shaped to suit, with drain gradients making allowance for settlement. Capping of the TSF

will include placement of a nominal 500 mm thick layer of benign mine waste rock, topped with a nominal 200 mm thick layer of topsoil.

The final slope profile for the downstream face of the TSF allows for a grade of 20˚ on the upper

portion and 15˚ in the lower portion by placement of benign waste rock on the downstream face.

Hydromet TSF

The closure concept for the Hydromet TSF allows for the placement of a minimum 1 m of beneficiation tailings over the Hydromet tails, followed by placement of a HDPE liner welded to

the basal liner to fully encapsulate the Hydromet tailings. A 300 mm thick “cushion layer” of beneficiation tailings will be placed over the HDPE followed by 500 mm of benign waste rock and 200 mm topsoil. The various layers will be shaped to result in a surface draining to a stable

spillway channel in natural ground located to suit the final level achieved. If the Hydromet TSF is higher than the Beneficiation TSF then drainage will be matched to the Beneficiation TSF closure surface and use the same spillway channel.


Figure 6-3 TSF closure concept general arrangement

Figure 6-4 TSF concept capping design


7. Consequence based designrequirements7.1 General

Specific design requirements for tailings dams are given by DMIRS (formerly DMP) and

ANCOLD depending on the TSF type and classification.

Consequence based classification of a TSF is primarily based on an assessment of the potential extent or severity of impacts due to embankment failure or uncontrolled release of tailings

and/or water, should such events occur. This assessment is supplemented by consideration of embankment height (DMIRS) or the number of people likely to be impacted (ANCOLD). The following are initial screening level assessments subject to review at detailed design.

7.2 DMIRS TSF characterisation

In accordance with the requirements of the DMP Code of Practice for Tailings Storage Facilities in Western Australia (Code of Practice), a hazard rating for the TSFs has been prepared to

determine the appropriate TSF category. Hazard Rating assessments are noted in Table 7-1.

Table 7-1 DMIRS TSF characterisation

Type Extent/Severity of Impact Beneficiation TSF Hazard

Rating

Hydromet TSF Hazard

Rating

Release of Tailings Water or Seepage

Loss of human life or personal injury

Possible though not expected. Low Low

Adverse human health

Possible though not expected. Low Medium

Loss of assets Not expected due to the location and lack of infrastructure downstream.

Low Low

Environmental or heritage damage

Given the geochemistry of the material heritage and environmental damage is not expected for Beneficiation TSF with a potential for the Hydromet TSF.

Low Medium

Embankment Failure

Loss of Human Life Potential for loss of human life dependent on itinerants on haul road downstream.

Medium Medium

Adverse human health

Not expected for the beneficiation TSF however potential for the Hydromet TSF.

Low Medium

Loss of assets Expected due to loss of TSF. Medium Medium

Environmental or heritage damage

Transportation of sediments into the local waterways expected to impact surface water quality.

Medium Medium



With a maximum height in the range of 5 to 15 m the Beneficiation TSF is classified as Category

2 for Release of Water and for Dam Failure.

7.2.2 Hydromet TSF

With a maximum height in the range of 5 to 15 m the Hydromet TSF is classified as Category 2

for Release of Water and for Dam Failure. This is a reduced hazard rating relative to the original

FS concept design due to the assessed lesser impact associated with failure of the Hydromet

TSF relative to TSF3 (i.e. significant tailings stack height reduction).

Notwithstanding this, the revised pre-construction design still adopts more conservative

category based design criteria for both the Beneficiation and Hydromet TSF relative to the FS

concept as described in Section 7.4.

7.3 ANCOLD consequence category

Preliminary assessments of the Consequence Category for the Beneficiation TSF and Hydromet

TSF have been undertaken, as per ANCOLD guidelines (ANCOLD, 2012b). The Consequence

Category assessment guides the pre-construction design, operation and maintenance

requirements for the storages.


Dam failure consequence category

The following assumptions have been used to develop the Consequence Category assessment

for the Beneficiation TSF:

The costs for the infrastructure and dam replacement and clean-up costs would be likely to

exceed 10 million dollars but be less than 100 million dollars giving a medium level ofdamage (assessed under ANCOLD).

The impact of a sunny day failure on the dam owners business is ‘Major’ as the operation of

the tailings dam is critical to the ongoing extraction and processing of the rare earthminerals and would lead to major economic impacts.

The impact of a dam failure on health and social impacts is minor due to the regional

location of the dam.

The environmental impacts of a sunny day failure of the embankment is minor due to thebenign nature of the material and low expected radiological impacts.

The environmental impacts of a flood loading failure scenario are considered to bemoderate due to the benign nature of the material and the lack of expected long-termeffects of the material within the surrounding environment.

Population at Risk (PAR) in flow path in case of failure would be limited to itinerants givenno current permanent residences or mine facilities downstream. However, flooding couldaffect the site haul road. Arguably the PAR could be <1 but conservatively between 1 and

10.

Utilising these assumptions, the TSF embankment has been assigned a Consequence

Category of Significant (consistent with ATCW 2019) or High C dependant on the

adopted PAR. For the purpose of Pre-Construction Design, High C is adopted to ensure

the use of conservative category based design parameters.


Environmental spill consequence category

The Environmental Spill Consequence Category for the Beneficiation TSF has been assessed

as Low, due to the benign nature of tailings, and relatively low environmental risk posed by the pond water following a short term spill event.

7.3.2 Hydromet TSF

Dam failure consequence category

The following assumptions have been used to develop the Consequence Category assessment

for the TSF:

The costs for infrastructure and dam replacement and repair costs are estimated to bebelow 10 million dollars giving a low level of impact (assessed under ANCOLD).

The impact of a sunny day failure on the dam owners business is ‘Major’ as the operation ofthe tailings dam is critical to the ongoing ore extraction and mineral processing.

The impact of a dam failure for sunny day loading on health and social impacts is minor due

to the regional location of the dam.

The environmental impacts of a sunny day failure of the embankment is major.

The environmental impacts of a flood loading failure scenario are considered to be major

due to the nature of the material and the lack of expected long-term effects of the materialwithin the surrounding environment.

Population At Risk (PAR) in flow path in case of failure would be limited to itinerants given

no current permanent residences or mine facilities downstream. However, flooding couldaffect the site haul road. Arguably the PAR could be <1 but conservatively between 1 and10.

Utilising these assumptions, the TSF embankment has been assigned a Consequence

Category of Significant or High C dependant on the adopted PAR. For the purpose of Pre-Construction Design, High C is adopted to ensure the use of conservative category based

design parameters.

Environmental spill consequence category

The Environmental Spill Consequence Category for the Hydromet TSF has been assessed as

Significant due to the increased environmental risk resulting from a spill due to the increased

concentration of Magnesium Sulphate and the concentration of radionuclides within the

material.

7.4 Category based design criteria

7.4.1 Design criteria

Based on the assessed dam failure and spill consequence category, the fall-back design criteria

suggested by ANCOLD 2012 prevail and give more conservative freeboard and stormwater

storage capacity requirements relative to the DMIRS minimum requirements.

The specific design requirements resulting from the consequence-based categorisation of the

TSFs are as follows in Table 7-2.


Table 7-2 Design criteria from consequence category

Design Criteria Beneficiation TSF Hydromet TSF

Stormwater Storage Capacity 1:5 wet season plus 1:100 AEP, 72 hr flood

1:10 wet season plus 1:100 AEP, 72 hr flood

Additional Freeboard nil 1:10 AEP wind runup plus 0.3 m

Spillway 1:100,000 AEP, critical flood plus 1:10 AEP wave run-up or PMF

1:100,000 AEP, critical flood plus 1:10 AEP wave run-up or PMF

Seismic Loading

Operation Based Earthquake (OBE)

1:1000 1:1000

Maximum Design Earthquake (MDE)

1:10,000 1:10,000

Closure MCE approximated to 1:10,000 AEP

MCE approximated to 1:10,000 AEP


8. Pre-construction design details8.1 Construction materials and site clearing

Prior to bulk earthworks and embankment construction, the impoundment and embankment

footprint areas will be cleared, grubbed and stripped of topsoil to a nominal thickness of 200 mm and stockpiled for later use in the rehabilitation of the site.

The materials required to construct the low permeability zones within the embankments will

largely be sought from external borrow pit areas but where possible from within the storages. Borrow pit areas are currently under investigation by Hastings. The select earthfill and gravel materials (structural fill) will be sought from the pit overburden material stockpiled on site. An

onsite rock borrow pit (with mobile crushing plant) will be established to produce pavement materials for site access roads and the embankment crest roads.

The near surface clayey sand deposits within the Beneficiation TSF footprint will be retained to

assist with seepage control.

The Hydromet TSF will incorporate a HDPE geomembrane placed across the impoundment floor and on the upstream face of containment embankments. The in situ clayey sands will be

retained and reworked to form a compacted clay liner below the geomembrane. In areas lacking a suitable thickness of in situ clay, soils from an external borrow pit will be imported to form the base clay liner for the floor of the Hydromet TSF.

8.2 Beneficiation TSF

8.2.1 Storage characteristics and embankment design

The starter dam design for the Beneficiation TSF features an embankment crest width to enable light vehicle access only. The upstream face will have a 2:1(H:V) batter slope to maximise

tailings storage and minimise construction material. The downstream face will have a 2.5:1 (H:V) batter slope which is considered suitably conservative to achieve geotechnical stability requirements. Sufficient space will be maintained between the dam toe and the lease boundary

to allow for further design raises and the closure batter flattening works. The starter dam for the Beneficiation TSF features the geometry as listed below in Table 8-1.

Table 8-1 Beneficiation TSF starter embankment geometry

Description Design

Starter Dam Height ~ 6.5 m

Minimum crest width 7 m

Embankment Length 1,600 m

Upstream batter slope 1:2.0 (V:H) – Starter Dam

Downstream batter slope 1:2.5 (V:H) – Starter Dam (flattened for closure, see Section 6.5)

Zoning Upstream clay and downstream general selected earthfill

The estimated total storage requirement for the Beneficiation TSF is approximately 6.5 Mm3.

The estimated storage capacity of the Stage 1 starter dam is approximately 2.5 Mm3, sufficient

for the first 3 years only. At a filling rate of 0.65 Mm3pa, the TSF would operate with conventional spigot discharge from the northern and eastern embankments for the initial 2 years, with additional capacity developed by extending spigots and discharge from higher

elevations to the east and south. To achieve the necessary storage capacity for the mine life volume, the perimeter embankments will need to be raised by approximately 4.5 m. The design conservatively assumes raising using downstream construction methods.


The Pre-Construction Design Drawings presented in Appendix A provide staging drawings for

the TSF over the mine life.

A storage curve for the Beneficiation TSF is presented in Figure 8-1. Note that this applies to a

flat tailings surface whereas the actual volume estimates to determine the required embankment

heights have considered the beach development around the TSF giving the benefit of

increasing storage due to beaching around the south and east of the facility.

Figure 8-1 Beneficiation TSF storage curve

The design embankment for the Beneficiation TSF embankment incorporates three zones:

Zone 1: Upstream sloping low permeability zone (clayey materials).

Zone 3A: Downstream general select earthfill (general structural fill).

Zone 2: Select sandy gravel if necessary for desiccation prevention on the surface of theupstream clay zone (subject to construction and tailings filling schedule).

A typical section of the embankment is shown in Figure 8-2 below.

Figure 8-2 Beneficiation TSF embankment typical section

To reduce potential seepage beneath the embankment, the design allows for excavation of a cut-off trench at the upstream toe that is excavated to moderately weathered bedrock. The

excavated trench will be backfilled with compacted Zone 1 material.

0

1000000

2000000

3000000

4000000

5000000

6000000

326 328 330 332 334 336 338 340

Storage (m3)

RL(m)

Beneficiation TSF Storage Curve (Flat)


It is envisaged that Zone 1 construction material will primarily be sourced from nearby borrow pit

areas where clayey sand is available at a suitable thickness. The clayey soils from borrow pit

areas in the vicinity of the TSF may be supplemented by clayey (saprolitic) material recovered

during stripping at the Bald Hill pit.

The in situ moisture content of the clayey borrow pit materials is generally expected to be lower

than optimum moisture content at the time of construction; consequently, moisture conditioning

by adding water during construction is anticipated to optimise compaction. Based on laboratory

test data, in situ moisture content at the time of the investigation was generally 2% - 5% below

OMC, except at the location of test pit CTTP-03 where moisture content was 4% wet of

optimum.

External borrow pit sources of clayey sand typically ranged from between 1.5 m and 2.0 m in

depth. ATCW geotechnical investigations found that the clayey materials in the vicinity of the TSF

have moderate to low dispersion potential, inhibited to some extent by the presence of calcium

carbonate (Emerson class 4). Dispersion and erosion on the upstream slopes of the

embankments will be minimised by the accumulation of tailings against the low permeability zone.

Zone 3A material will be sourced from pre-stripping operations at Bald Hill and will be used to

form the bulk of the embankment volume, possibly combined with residual materials excavated

from borrow pit areas in the vicinity of the TSF.

8.2.2 Tailings deposition and decant pond

Tailings deposition within the Beneficiation TSF will involve perimeter discharge in frequent and

uniform cycles around the facility via a 280PN20 HDPE pipeline with spigots nominally spaced

at 50 m intervals. A new perimeter access road will need to be constructed with sufficient width

to accommodate the tailings discharge pipeline so that tailings beaches can be gradually

formed around all sides of the facility. The spigots would extend down the face of the

embankment and reservoir slopes and depending on the beach slope achieved during

operations, be extended out onto the tailings beach to develop an optimal beach shape.

Towards the end of mine life, elements of Central Thickened Discharge (CTD) would be

adopted to effectively fill the storage and achieve a safe closure surface.

At the commencement of operations, tailings deposition will focus on quickly pushing the pond

away from the main embankment to the proposed initial decant tower location. This will be aided

by a new channel excavated into the floor of the TSF to connect the decant tower with the valley

low point. This will allow decant water to be returned to the plant at the earliest opportunity.

Later in the operational life of the TSF, a new decant tower will be constructed towards the

southern end of the facility so that the pond can be relocated to its ultimate location, where a

discharge channel will be excavated through rock at closure (refer Closure and Rehabilitation

Concept, Section 6.5).

The decant towers will be accessed by a new causeway construction from readily available fill materials. The decant causeway will be raised and/or relocated as part of the construction works associated with raising of the TSF, most likely at 3 years and 6 years into operation.

The proposed decant tower will be a slotted concrete ring type of decant arrangement whereby

ponded water decants through slots in the side of a concrete ring tower which is raised

incrementally to remain elevated above the rising tailings. A variable speed submersible pump

will be installed at the base of the tower for water return to the plant.

Staged general arrangement plans are presented in the Pre-Construction Design Drawings in

Appendix A.


8.2.3 Emergency spillway design

The Beneficiation TSF includes the initial construction of an emergency spillway excavated through natural ground on the southern side of the facility. Conceptually, the spillway is

nominally set 1 m below the TSF embankment crest level with the tailings beach lowered to suit in this location.

A nominal spillway width of 50 m has been adopted which provides ample capacity to pass the

PMF event. Below the spillway level there is sufficient capacity to accommodate the combined wet season storage and extreme storm storage capacity (refer Stormwater Storage Assessment, Section 9.1). The final spillway location at end of mine life will be through a granite

ridgeline on the southern side of the facility to ensure long term stability.

8.3 Hydromet TSF

8.3.1 Storage characteristics and embankment design

The Hydromet TSF tailings will be of neutral pH, are not acid forming and test work has

demonstrated that solution and mobilisation of dissolved metals (including radionuclides) from the tailings deposit is not expected as a result of infiltration. Nevertheless, the incorporation of a liner system for the Hydromet TSF has been adopted due to the elevated salinity of the

magnesium sulphate solution, which is used to slurry the Hydromet plant residue and the Barron Liquor.

To minimise seepage the Hydromet TSF features a geocomposite lining system that comprises

a minimum 300 mm thick compacted clay liner (CCL) below a HDPE liner. This is a well proven lining system that is commonly used in industry for containment of hazardous mining and landfill wastes.

The Hydromet TSF storage cell abuts the Beneficiation TSF on its western side and forms a closed storage area. Embankment construction consists of a Zone 3A select earthfill sourced from the pit overburden and a sloping impermeable Zone 1 on the upstream face and an

impermeable HDPE liner. As a result, an upstream erosion protection layer is not required.

The starter dam design for the Hydromet TSF features an embankment crest width to enable light vehicle access only. The upstream face will have a 3:1(H:V) batter slope that is suitable for

application of the lining system. The downstream face will have a 2.5:1 (H:V) batter slope which should be suitably conservative to achieve geotechnical stability requirements. The starter dam for the Hydromet TSF features the geometry as listed below in Table 8-2.

Table 8-2 Hydromet TSF starter embankment geometry

Description Design

Starter Dam Height ~ 6 m

Minimum crest width 7 m

Embankment Length ~ 2,000 m

Upstream batter slope 1:3.0 (V:H) – Starter Dam

Downstream batter slope 1:2.5 (V:H) – Starter Dam (flattened for closure, see Section 6.5)

Zoning Upstream clay and downstream general selected earthfill

The estimated total storage requirement for the Hydromet TSF is approximately 1.9 Mm3.

The estimated storage capacity of the Stage 1 starter dam is 0.45 Mm3, sufficient for the first 3 years. After the initial 3 years of operation, the Hydromet TSF would be raised by approximately 3.0 m to its proposed ultimate height. Raising would be completed by downstream construction

with an allowance to join and extend the lining system on the upstream face up to the ultimate height.


The design for the Hydromet TSF embankment incorporates two primary zones:

Zone 1: Upstream sloping, low permeability zone (clayey materials) that forms part of the

geocomposite lining system for the TSF.

Zone 3A: Downstream select mine waste rock or impoundment excavation materials.

A typical section of the embankment is shown in Figure 8-3 below. This is a robust design

utilising downstream construction methods to ensure a very low probability of dam failure.

Figure 8-3 Hydromet TSF embankment typical section

8.3.2 Tailings management

The Hydromet TSF will receive the combined Hydromet waste stream in a single pipeline

extending around the embankment crest access road. The TSF will be commissioned with single point discharge to fill the valley section of the TSF where the tailings deposit will be deepest and less consolidated due to the initial higher rate of rise. Within this valley section, a

network of underdrains can be installed above the liner to assist with consolidation of the low density tailings. The requirement for these valley underdrains will be confirmed in detailed design.

Due to the low solids tailings, a flat beach is expected to develop within the TSF and the base is substantially covered within the first year of operation. At this point in time an evaporation balance is achieved and tailings density will be further increased by drying. At the end of mine

life, the average depth of Hydromet tailings is expected to be approximately 4.5 m. This is a conservative estimate based on an assumed average 0.5 t/m3 final density.

The concept design for the underdrains installed under the tailings within the valley section of

the TSF comprises the use of multiple panel (e.g. Megaflo) collection drains to maximise drain surface area and promote water recovery. A collection sump would be constructed and fitted with a submersible pump for recovery and return of water to the surface of the TSF, the intent

being to promote consolidation and to increase tailings density in the deeper valley section of the facility.


Figure 8-4 Megaflo panel drain examples (courtesy Geofabrics Australia)

8.3.3 Emergency spillway design

The Hydromet TSF includes the construction of an emergency spillway sized to safely pass a

PMF event without overtopping of the embankment. The spillway will initially be excavated

through rock on the northeast corner of the TSF, allowing spills to be directed to the

Beneficiation TSF decant pond, which has a larger capacity to store extreme flood events.

Nominal dimensions of 20 m wide and 600 mm deep have been adopted.

Below the spillway level there is sufficient capacity to accommodate the combined wet season

storage and extreme storm storage capacity (refer Stormwater Storage Assessment, Section

9.1).

8.3.4 Geomembrane selection and installation considerations

The Hydromet TSF design features a geocomposite liner system which comprises a

geomembrane overlying a compacted clay liner. The compacted clay liner plays an important

role in forming a smooth and unyielding subgrade and also restricts leakage rates due to any

defects within the overlying geomembrane.

For the purpose of pre-construction design, High Density Polyethylene (HDPE) geomembrane

has been selected as the preferred geosynthetic liner. HDPE geomembranes are

manufactured by combining a polymer resin (>95%), with additives such as antioxidants,

stabilizers, plasticizers, fillers, carbon-black, and lubricants (as a processing aid). These

additives enhance the long- term performance of geomembranes by protecting the

polyethylene from degradation (Ewais and Rowe 2014).

HDPE is commonly used for waste containment as it exhibits high strength and chemical

resistance to a wide range of chemicals. Significant experience and data also exists relating to

the long term performance and service life for HDPE liners. HDPE geomembranes are

extremely durable products, designed with service lives of up to several hundreds of years

under a broad range of environmental conditions.

The service life of HDPE geomembranes has historically been determined by its half-life, which

is the point at which the 50% depletion level of antioxidant additives occurs. This is not

considered appropriate for estimating the service life of a HDPE geomembrane for containment

purposes (Rowe 2012), as although the design property, e.g., depletion of antioxidant additives,

may be reduced by 50%, the mechanical properties of the geomembrane enable it to function

as a hydraulic barrier for considerably longer.

In practice, a number of variables will determine the actual lifespan of any geomembrane.

Factors that influence the lifespan of a geomembrane are the material properties of the

geomembrane – physical, mechanical, durability and performance properties, the compatibility


of the geomembrane with site-specific conditions including tailings leachate chemistry, clay

liner, subgrades, foundations and applied stresses, the operating conditions of the facility

including temperature, UV light from exposure, ionising radiation, installation, backfilling and

construction factors.

The Hydromet TSF includes numerous factors to minimise potential degradation of the lining

system as detailed below:

Selection of a white HDPE geomembrane. The lifespan of HDPE geomembranes

reduces drastically at elevated temperatures because higher temperatures act as catalysts

that speed geomembranes’ degradation reactions such as antioxidant depletion, chemical

degradation and UV degradation. Even at moderate temperatures, a black geomembrane

can become very hot, making it prone to wrinkling or folding, and in the process losing

contact with its foundation.

Under the recorded month average air temperature range at the proposed TSF site (21-

41°C), selection of a white reflective liner should result in a liner temperature on average

21–23°C cooler than its carbon black counterpart, with correspondingly less risk of

wrinkling and installation defects that may lead to developing stress cracks (Rentz et al.

2017).

Critically, a 20°C reduction in temperature avoids thermal regimes where recrystallisation

of polymers can occur which can lead to rapid onset of failure of the liner.

For exposed portions of the HDPE liner, exposure to UV can decrease the expected or

predicted lifespan by a factor of seven (GeoSynthetics Institute). Selection of a white liner

(achieved by the addition of titanium dioxide and associated HALS and UV stabilisers) will

reflect most of the UV light reaching the surface of the liner, ultimately prolonging its

lifespan.

Selection of appropriate additives. To combat geomembrane degradation at higher

temperatures, selection of an appropriate additive antioxidant composition able to resist

significant loss of mechanical and performance properties at elevated temperatures is

proposed. It is anticipated that during detailed design, design of additive composition will

include careful consideration of the tailings leachate chemistry, thermal regime and

exposure to ionising radiation.

The presence of low level ionising radiation (approximately 35Bq/g) is anticipated to have

an impact on the rate of antioxidant consumption. Recent studies by Tian et al. (2017)

indicate that low level radioactive leachates can promote radiative oxidation that consumes

antioxidant consumption on the order of approximately 10% faster than non-radioactive

leachate alone. Much of the impact of α and β radiation would be mitigated by placement of

a thin layer of benign tailings on the liner prior to deposition of radioactive tailings due to

the fact that radionuclides are non-mobile in the tailings.

Selection of an appropriate liner thickness. All other factors considered, the thickness of

the HDPE liner has a direct relationship to its service life due to increased availability of

stabilisers and antioxidants and increased stress crack resistance of the liner. It is

anticipated that a liner of between 1.5 and 2.0 mm in thickness will be required to achieve

the desired service life.

Construction Methodology. The smoothness, uniformity, and density of the subgrade and

the quality of the installation – lack of wrinkles, intimate contact with subgrade, seams,

penetrations, minimum extrusion welding, minimum shear stress on slopes are perhaps the

most critical factor affecting liner life after material composition.


An example of a detailed construction and testing methodology is attached, which outlines the typical controls and hold point put in place to ensure development of an appropriate

construction methodology and QA/QC process to ensure that it is correctly implemented.

QA/QC. The QA/QC process for the HDPE liner installation will also be a critical aspect of

construction involving seam testing as well as destructive testing of liner samples. Post

installation of the HDPE liner, electrical leak detection testing shall be carried out involving

both arc and dipole test methods as follows:

– Standard Practice for Electrical Leak Location on Exposed Geomembranes Using the

Arc Testing and/or Water Puddle Testing Method (ASTM D 7002 and/or ASTM 7953).

– Standard Practice for Electrical Method of Locating Leaks in Geomembrane Cover with

Water or Earth Materials ASTM D 7007 on the pond base.

The attached draft geosynthetic lining specification details the typical QA/QC testing and construction supervision requirements typically implemented to supervise the construction of a composite geomembrane lining system.

TSF Operation. In addition to designing specialised geomembrane polymer compositions

for resisting degradation, their degradation may also be reduced by a protective thick layer

tailings to take advantage of relatively lower geothermal ground temperatures

(approximately 17°C). For exposed portions of the liner, leachate trickle systems may be

considered to increase evaporative loss of decant water whilst simultaneously cooling the

exposed portion of the liner.

Further details on the above measures to ensure the required service life of the HDPE geomembrane are detailed in the attached generic geomembrane specification (Appendix H).

It is considered that, given the anticipated physical, climatic, chemical and other constitutive

factors anticipated for the proposed TSF, an appropriately selected HDPE geomembrane together with proper construction techniques (including adequate construction quality assurance), and by laying the geomembrane over a well-graded smooth foundation, service life

in the hundreds of years is readily achievable.


9. Specific design studies 9.1 Stormwater storage assessment

9.1.1 General

Stormwater storage capacity and freeboard allowances during mine operation have been

determined for the TSFs in accordance with ANCOLD requirements.

For the purpose of determining the required stormwater storage capacity, the TSF catchment

system comprises both embankments and their catchments.

9.1.2 Storage requirements and freeboard

Freeboard and stormwater storage allowance as defined in ANCOLD 2012 is illustrated below in

Figure 9-1.

Figure 9-1 ANCOLD freeboard definition

For the Beneficiation TSF, the 86 ha catchment comprises of the upstream impoundment area

accounting for construction of the upstream diversion drain. This catchment area is applicable

from commissioning until closure.

For the Hydromet TSF, the catchment incudes the full impoundment area defined by the

downstream crest of the final embankments. The catchment area for the storage is 36 ha for the

TSF.

For stormwater storage and freeboard assessment it is conservatively assumed that there is

zero infiltration loss during rainfall and wet season events.

To mitigate the risk of environmental spill, the freeboard for each of the TSFs in the initial three

years has been assessed assuming no decant recovery during a 1:100 year, 72 hr storm event.

The calculated stormwater storage and freeboard requirements for the respective TSFs are

given in Table 9-1. This shows that the Normal Maximum Operating Level (NMOL) for the

Beneficiation TSF and Hydromet TSF decant pond is 2.0 m and 1.15 m respectively below the

spillway level in each facility.


Table 9-1 Freeboard and stormwater storage requirements

TSF Freeboard Component Freeboard Volume (m3)

Freeboard Depth (m)

Beneficiation TSF Spill Consequence Category = Low

Wet Season Storage Allowance (1:5 AEP)

260,000 1.4

Extreme Storm Storage (1:100 AEP, 72 hr)

215,000 0.6

Contingency Storage (Contingency including waves)

0 0

Total (depth/capacity between spillway and Normal

Minimum Operating Level (NMOL))

475,000 2.0

Hydromet TSF Spill Consequence Category = Significant

Wet Season Storage Allowance (1:5 AEP)

105,000 0.3

Extreme Storm Storage (1:100 AEP, 72 hr)

90,000 0.25

Contingency Storage (Contingency including waves)

210,000 0.6

Total (depth/capacity between spillway and NMOL)

405,000 1.15

9.2 Flood hydrology

9.2.1 Hydrological modelling

Hydrological modelling was undertaken to assess the capacity requirements of the water management structures associated with the TSF including spillways and diversion drain.

This section summarises the process used in determining the capacity requirements. Modelling of the rainfall routing through the storages was undertaken utilising RORB software to determine the critical duration, expected flows and height of water in the storages.

Design rainfall events

In order to determine design rainfall events, the Generalised Short Duration Method (GSDM) and the Revised Generalised Tropical Storm Method (GTSMR) were used, as outlined in ‘Australian Rainfall and Runoff: A Guide to Flood Estimation’ (Ball et al., 2016), in conjunction

with Intensity Frequency Duration (IFD) data obtained from the Bureau of Meteorology.

Figure 9-2 presents design rainfall events for various AEPs and storm durations.


Figure 9-2 Design rainfall IFD curves

Hydromet TSF

Due to the arrangement of the facility, the catchment of the Hydromet TSF is limited to the internal area and external crest footprint, equating to 36.2 ha.

A graphical representation of the modelling results is presented in Figure 9-3.

The operational level of the TSF was modelled as 250 mm above the tailings level to allow for the 1:100 AEP 72 hour rainfall event at the commencement of the design flood event. This is in

excess of the Normal Maximum Operating Level which ensures a conservative estimate of spillway discharge.

Figure 9-3 Hydromet TSF hydrograph (critical duration)

As per the Consequence Category assessment (see Section 7.3), the TSF is required to pass a PMF flood event. The modelling completed found the critical event to be 12 hours, with a peak


inflow of 15.4 m3/s and a peak outflow of 8.5 m3/s. The proposed spillway arrangement ensures adequate capacity to pass a PMF rainfall event without overtopping of the TSF embankment.

Beneficiation TSF

Due to the arrangement of the facility, the catchment of the TSF is limited to the internal area of the facility and the external catchment upstream of the footprint, equating to 106 ha.

A graphical representation of the modelling results is presented in Figure 9-4.

The operational level of the TSF decant pond was conservatively modelled as 1.0 m below the spillway crest at the commencement of the design flood event. This is in excess of the Normal Maximum Operating Level which ensures a conservative estimate of spillway discharge.

Figure 9-4 Beneficiation TSF hydrograph (critical duration)

As per the Consequence Category assessment (see Section 7.3), the TSF is required to pass a PMF flood event. The modelling completed found the critical event to be 4 hours, with a peak inflow of 95.16 m3/s and a peak outflow of 49.08 m3/s. The proposed spillway depth of 1000 mm

ensures the PMF is passed without overtopping of the TSF embankment.

Upstream cut-off drain

The catchment area upstream of the Beneficiation and Hydromet TSF is limited by the topography of the local area and equates to a total of 41 ha, this was then split equally between

the two TSFs. The sizing of the drain has been developed to meet the requirements of 1:100 AEP rainfall event using mannings equations for open channels. The parameters used in the development of the drain size can be found below.

Table 9-2 Cut-off drain design parameters

Parameter Value

Area 3 m

Perimeter 4.8 m

Slope 1:500 m

Mannings n 0.025

The drain design allows for flow from each sub-catchment to flow in separate directions

minimising the size of the required drain. Further details on the design of the external

diversion drain can be found in the Pre-Construction Design Drawings in Appendix A.


9.3 Water balance

A basic spreadsheet water balance model (WBM) was developed by GHD to assess the storage

behaviour and test the capacity of the Hydromet TSF for rainfall and tailings storage. The model will be used as a preliminary check and may be used as a basis for a more detailed version in GoldSIM in the future.

9.3.1 Input data

Hydromet TSF

The physical parameters relating to the Hydromet TSF were based on the current design and are outlined in Table 9-3.

Table 9-3 Hydromet TSF data

Input Values

Maximum Operating Level 339.35 m

Spillway Level 340.5 m

Full Supply Volume ~ 1900 ML

Data relating to the volumes and flow rates of tailings material and bleed water entering the Hydromet TSF appear in Table 9-4.

Table 9-4 Tailings material and bleed water data

Input Values

Annual Production Solids 72,000 tonnes

Flow of Tailings Solids 62,500 m3/day

Flow of Tailings Water Retained Water 0.3 ML/day Free water 1.2 ML/day

Catchment area

There is no external catchment reporting to the Hydromet TSF due to the upstream diversion

drain, as such, the catchment area for the Hydromet TSF is 36.2 hectares.

Climate data

Climate data, including rainfall and evaporation were used for the development of the WBM. The details and sources of the data are outlined in Table 9-5.

Table 9-5 Climate input data

Climate Data Source of Data

Historical Rainfall Data SILO Data drill (Lat -23.95, Long: 116.30) – QLD Government

Historical Evaporation Data SILO Data drill (Lat -23.95, Long: 116.30) – QLD Government

9.3.2 Assumptions

The following assumptions were made in the development of the WBM:

No external catchments report to the Hydromet TSF

All spill from the Hydromet TSF reports to the Beneficiation TSF

The available water shall be evaporated from the Hydromet TSF including free bleed water

from the deposited tailings and rainfall


The Hydromet TSF was assumed to be empty at the start of the WBM (elevation 331.5 m)

No seepage losses occurred from the Hydromet TSF due to lining

9.3.3 Methodology

Scenario modelling

The scenario tested in the WBM simulates the current plant operational settings to assess the

viability and likely performance of the Hydromet TSF over a 10 year operational mine life. The

scenario was run for three rainfall scenarios, namely, 20 percentile rainfall, 50 percentile rainfall

and 80 percentile rainfall.

Model settings

The settings and corresponding parameters used in the water balance model for the Hydromet

TSF are detailed in Table 9-6.

Table 9-6 Simulation settings

Settings Parameter

Time Step Monthly

Data Range 20 percentile rainfall: 01/07/1889 to 30/06/1906

50 percentile rainfall: 01/07/1938 to 30/06/1948

80 percentile rainfall: 01/07/2009 – 31/12/2018/, to 01/01/1889 – 30/06/1889

Number of Simulation Years 10 Years

Hydromet TSF Initial Water Level 331.5 m

Methodology

The following steps were undertaken in order to model the water balance across the Hydromet

TSF:

20, 50, 80 percentile rainfall scenarios were determined across a 10 year period with

monthly time steps.

– The 20th percentile 10-year rainfall is the volume corresponding at which only 20% of

the record is lower.

– To find a 20th percentile rainfall volume, the entire rainfall record was grouped in

windows of 10 years starting at 1 Jul 1889 to 30 Jun 1898, continuing with 1 Jul 1890

to 30 Jun

– 1899, “wrapping around” at 1 July 2018 to 30 Jun 1897, etc.

– The 10-year window sums are ranked and solved for 20% higher than the lowest

rainfall sum.

– The same procedure is done for the other percentiles.

Monthly average evaporation was determined based on SILO data from 1889 to 2019.

The Hydromet TSF volume was calculated for each time step using the following equation:

– Volume (ML) = P – E+ QT

Whereby:

– P = Precipitation


– E = Evaporation

– QT = Flow of tailings solids, free water and retained water

9.3.4 Model Results

The overall inventory of the Hydromet TSF appears in Figure 9-5.

Figure 9-5 Overall hydromet TSF inventory

From the water balance analysis it was found that the storage volume for the Hydromet TSF could support the total volume of tailing solids, free water and retained water for a 20, 50 and 80 percentile rainfall over a 10 year period, starting empty.

A detailed whole site GoldSim water balance will be undertaken during detailed design to confirm the site requirements and confirm the findings of the preliminary water balance.


9.4 Seepage analysis

9.4.1 Methodology

A concept level 2-D seepage analysis using the finite element software, Rocscience Slide, was

carried out to assess the potential for seepage development from the refined TSF arrangement. Only the Beneficiation TSF was considered in the analysis. The Hydromet TSF design features a geocomposite liner system that ensures very small rates of seepage, hence negating the need

for seepage modelling at this stage.

The seepage modelling completed by GHD was carried out to supplement previous seepage modelling presented in ATCW 2019. For the originally proposed arrangement (refer Section 3),

ATCW found that “the presence of confined water pressure in the aquifer below approximately

50 m depth and the presence of a very low permeability, unsaturated granite rock mass above this depth, the likelihood of significant downward seepage of water contained in saturated, very low permeability tailings stored at the ground surface is considered very low”. Seepage modelling by ATCW was limited to considering the Return Water Pond (RWP) and TSF2 since these were considered to have higher seepage potential relative to the other TSFs.

Key changes between the previous concept design presented in ATCW 2019 and the refined TSF arrangement is that both TSF2 and the RWP have been eliminated from the design which significantly reduces the risk of seepage related impacts.

Seepage analysis completed by GHD for the Beneficiation TSF involved developing an idealised cross-section through the TSF with a hydrogeological setting similar to that presented by ATCW 2019 (see Section 2.6) but with sensitivity analysis on layer thickness and hydraulic

permeability to assess the effects of varying conditions.

A transient model was established to estimate the rates of seepage into the foundation due to development of a pond on the Beneficiation TSF and also assessing the benefit of developing a

layer of low permeability tailings below the pond. The fate of seepage with time (0 – 1000 years) within the foundation was then assessed for the various model runs.

The seepage analysis considered a range of permeability values listed in Table 9-7 based on

ATCW inferred values and site investigation works.

Table 9-7 Model hydraulic conductivity values

Material Average ksat (m/s) Sensitivity model ksat (m/s)

Beneficiation Tailings 1 x 10-8

Zone 1 Clay Core 1 x 10-9

Zone 3A Fill Material 1 x 10-8

Sandy Clay Foundation 1 x 10-7

HW / MW Granite 1 x 10-7 1 x 10-6

SW / FR Granite 1 x 10-8 5 x 10-8

Fractured SW / FR Granite Aquifer 1 x 10-6

9.4.2 Results

The results of the seepage analysis shown in Appendix D, illustrates that the seepage expected over the life of the facility is expected to remain within the TSF footprint with the majority of the ponding expected in the highly weathered to moderately weathered granite.


The vertical seepage through the highly weathered to moderately weathered granite is illustrated below in Figure 9-6 using the flux generated in the seepage modelling. Importantly,

the conceptual modelling indicates that seepage flux exiting the TSF footprint is negligible.

Figure 9-6 HW/MW vertical seepage rates


9.5 Stability analysis

This Section presents the results of preliminary stability analysis to support the proposed design

of the TSF embankments.

In general the proposed embankment geometry and zoning provides geotechnically stable embankments in accordance with ANCOLD requirements. The design conservatively assumes

staged embankment raising using downstream construction methods.

Geotechnical investigations indicate foundation conditions across the TSF area comprise dense superficial soils and weathered rock at shallow depth. Any low strength or potentially liquefiable

soils will be stripped from the foundation prior to embankment construction.

9.5.1 Approach and methodology

A preliminary geotechnical stability analysis has been completed for the maximum (highest) section of the Beneficiation TSF embankment at its ultimate height as shown in Figure 9-7. This

is considered the critical section for all proposed TSF embankments.

The embankment was modelled with the Slope/W software package to perform Limit Equilibrium slope stability analysis. Bishop’s Simplified Method was adopted in calculating the factor of

safety values against sliding.

Figure 9-7 Stability model section

9.5.2 Load cases and factors of safety

Load cases considered for stability analysis are listed in Table 9-8. The ANCOLD “Guidelines on Tailings Dam Design, Construction, Operation and Closure” (ANCOLD 2012) state that there are no “rules” for acceptable factors of safety. However, they suggest the recommended Factors

of Safety (FoS) as shown in Table 9-8 which have been adopted for this preliminary analysis.


Table 9-8 Stability analysis FOS acceptance criteria

Condition Minimum Recommended

FoS

Target Minimum FoS

Long term drained conditions 1.5 1.5

For short term undrained conditions (potential loss of containment)

1.5 1.5

For short term undrained conditions (no potential loss of containment)

1.3 1.3

Given the absence of any potentially liquefiable soils within the embankment and foundation as

well as the proposed use of downstream construction methods for raising of the TSF, a post- seismic slope stability case is not considered critical and has been excluded from the preliminary analysis. Seismic assessment based on simplified deformation analysis is

subsequently presented in Section 9.6.

9.5.3 Soil and rock strength parameters

The parameters adopted for the constructed embankments and deposited tailings are based on laboratory testing and are presented in Table 9-9.

Table 9-9 Parameters used for stability analyses

Material Unit Weight

Undrained Effective

(Drained)

kN/m3 c (kPa) () Su c (kPa) ()

Zone 1 Clay 19 100 0 10 20

Zone 3A Selected general fill

21 0 35 0 35

Tailings 0.3 See Note 1 See Note 1

Clayey sand (foundation)

19 80 0 0 20

EW/HW Granite (foundation)

22 13000 35 500 38

SW Granite (foundation)

22 20000 43 500 43

Fresh Granite (foundation)

22 23000 46 500 46

Note 1: Undrained tailings properties were adopted for the drained analysis conservatively assuming that the tailings are contractive and likely to generate significant pore pressures on shearing. The use of drained parameters in stability analyses for contractive tailings is not appropriate as the pore pressure state along the failure surface is unknown.

9.5.4 Model pore pressure

For all analyses, it was assumed that decant water is able to pond against the perimeter embankment resulting in a phreatic surface developing through the embankment. In practice,

this is not allowed to occur and is therefore a very conservative assumption used to allow a simplified but conservative preliminary analysis. The modelled phreatic surface is presented in the model outputs within Appendix E.


9.5.5 Analyses results

A summary of the minimum Factor of Safety (FoS) achieved for each load condition is provided in Table 9-10. For the proposed embankment design, it can be seen that the minimum target

Factor of Safety is achieved in all cases. Figures showing the critical analysis outputs are given in Appendix E.

Table 9-10 Results of stability analysis

Loading Conditions Calculated FOS Target Minimum FOS

Short term undrained (no loss of containment), Downstream

1.9 1.3

Short term undrained (no loss of containment), Upstream

2.2 1.3

Long term, Undrained 1.9 1.5

Long term, Drained 1.9 1.5


9.6 Seismic assessment

9.6.1 Seismic risk

The risk posed to the TSF embankments from rare or extreme seismic events is considered to

be Low due to:

The relatively low seismicity of the site

The batter slopes achieve factors of safety above 1.5 for static stability

The embankment and foundations soils are not prone to seismic liquefaction

Based on the above factors, a seismic assessment was limited to simplified deformation

analysis. Two empirical analysis methods have been used including the Swaisgood Method and

Pells and Fell Method as described below. These are simplified screening methods that are

suitable for pre-construction design to confirm that excessive deformation and damage to the

embankment will not occur following an extreme earthquake.

9.6.2 Deformation analysis

ATCW 2019 presented the results of a simplified empirical method using Swaisgood (2003) to

assess the likely magnitude of crest settlement under seismic loading. This previous

assessment is still valid for the current proposed design (i.e. similar embankment and

foundation characteristics). ATCW predicted a maximum crest settlement of 90 mm for the

1:10,000 MCE. This magnitude of embankment settlement is considered acceptable and well

within the freeboard allowance for the TSF. Additionally, when assessed according to the Pells

and Fell (2003) method a “Minor” damage class is expected with associated cracking and

settlement unlikely to result in risk of breach and loss of containment.

Figure 9-8 Relative crest settlement versus peak ground acceleration (ATCW, 2019)


9.7 Hydromet TSF ammonia gas air emissions study

To inform the pre-construction design of the Hydromet TSF based on combining of the

Hydromet waste streams, Hastings advised GHD of the need to consider the potential health

and safety risks associated with potential for ammonia gas evolving at the TSF.

In April 2019, Hastings provided GHD with a worst case scenario, whereby the Hydromet TSF

receives a tailings stream at 76 t/h containing approximately 0.04 g/L of ammonium bicarbonate

and 6.28 g/L of ammonium hydroxide solution. Based on this “worst case scenario” condition,

GHD completed modelling to assess the potential evolution of ammonia gas (NH3) from the

proposed TSF. The results of this modelling were presented in a GHD Technical Memorandum,

15th April 2019 (refer Appendix I), that included predictions of daily ammonia gas generation

under a range of pH conditions including a worst case condition with an elevated pH of 11.3.

The estimated daily ammonia gas generation for this “worst case scenario” was estimated at

5,300 kg/day NH3.

Hastings subsequently engaged consultants ERM to undertake an air quality modelling

assessment of ammonia emissions from the Hydromet TSF. The ERM report is attached as

Appendix I. The model assessed the emission rate for ammonia under the “worst-case

scenario” described above. Ground level concentrations were evaluated at numerous onsite

and offsite receptor locations. These concentrations were then compared against Ambient and

OHS assessment criteria for NH3. ERM provided the following summary of observations from

their modelling:

No exceedances of air quality criteria were predicted at the identified offsite sensitivereceptors.

One exceedance (25.75 mg/m3) of the 15-min OHS criteria was predicted at an onsite

receptor (TSF receptor 1) located within 250 m from the centre of the source (Figure 4-1).This exceedance occurred under worst-case conditions. The next worst case scenariopredicted a concentration of 12.89 mg/m3 at this same receptor. This concentration is well

within the criteria (50% of the criteria).

In summary, the modelling results indicate that the maximum concentration is of lowlikelihood to occur and dependent on concurrence of worst case emission rate and worst

case dispersion conditions (i.e., prevalence of calm conditions, transition from stable tounstable meteorological conditions, and winds blowing towards this receptor).

Subsequent to completion of the above respective GHD and ERM studies, Hastings advised of

further refinements to the plant design which suggested a revised set of chemistry in offgas absorbing and dual alkali caustic regeneration. Mass Balance assumptions were updated accordingly with a key change being a significant lowering of pH under the worst case scenario

from pH 11.3 (basis of above studies) to below pH 9. This change to the “worst case scenario” is significant, since the amount of ammonia gas generation is proportional to the pH. The reduced pH to below 9 will significantly reduce the generation of NH3 under the worst case

scenario, as is demonstrated in Figure 9-9 below (extract from GHD Technical Memorandum).

Based on the above updates, there is assurance that the modelling completed by GHD and ERM is very conservative and hence the risks associated with ammonia gas evolution from the

Hydromet TSF are suitably low and manageable.


Figure 9-9 Ammonia/ammonium concentration vs pH (Richard, 1996)


10. Operations, maintenance and surveillance 10.1 Observational approach

In accordance with ANCOLD 2012, the design and management of the TSF shall utilise the

observational approach. The observational approach allows the TSF to be optimised over time

as monitoring information becomes available and the design and construction methodologies

evolve. The observational approach allows any changes that might occur during the life of the

TSF to be accommodated whilst meeting the design criteria and objectives over the entire life of

the TSF.

The key risks that could result in design and operation modifications during commissioning and

operation of the project are:

Life of mine and tailings production rate

Physical properties of the tailing including solids content and rheology

Geochemical properties of the materials

Variation in geological or hydrogeological conditions across the site

Variations in geotechnical properties of embankment materials following borrow pit area

investigations

Further studies and investigations being carried out as part of Detailed Design will assist in

mitigating the risks through greater understanding of the TSF areas.

Critical Operating Parameters (COPs) should be developed for the TSF against which the

performance of the TSF can be evaluated. The indicators address key functional, dam safety

and environmental requirements. The TSF Operating, Maintenance and Surveillance (OMS)

manual is regularly updated to reflect the COP’s and incorporate Trigger Action Response Plans

(TARPs) to ensure that intervention occurs well in advance of nearing any unsafe trigger event.

10.2 Monitoring and surveillance

ANCOLD (2003) provides guidance on the surveillance requirements and frequency for dams

based on their Consequence Category. Regular inspections and monitoring of instrumentation,

by suitably trained operators, is critical in ensuring structural integrity is maintained, and any

indications of failure are identified early and acted on appropriately. Instrumentation is also

important in monitoring the management of tailings against design assumptions, to determine if

any design changes are required during operations, or for closure.

The recommended inspection and monitoring types and frequencies are presented in Table

10-1 and Table 10-2.

Table 10-1 TSF inspection types and frequency

Inspection Type Recommended Frequency (ANCOLD, 2003)

High C

Routine Visual Daily to Tri-Weekly

Intermediate Annual

Comprehensive On Commissioning then 5 Yearly

Special As Required


Table 10-2 TSF monitoring types and frequency

Monitoring Type Recommended Frequency (ANCOLD, 2003)

High C

Rainfall Daily to Tri-Weekly

Storage Level Daily to Tri-Weekly

Seepage Daily to Tri-Weekly

Chemical Analysis of Seepage

ANCOLD recommend this be considered. The environmental monitoring plan for the site incorporates this requirement.

Pore Pressure Monthly to 6-Monthly

Surface movement 2 Yearly

The following instrumentation / monitoring is recommended at the site:

Rainfall gauge

V-notch weirs for environmental flow monitoring and seepage (if observed)

Vibrating wire piezometers (VWPs) for pore pressure monitoring

Settlement markers on embankments for movement monitoring

Regular tailings beach surveys for density reconciliation and comparing actual beach

development against design assumptions

Level gauge boards and / or automated level sensors for monitoring water levels

Monitor slurry density at the plant to compare against design assumptions

Monitoring of beach saturation via either routine sampling/testing or instrumentation

10.2.1 Instrumentation

This section outlines likely instrumentation that would be required, for monitoring safety and

performance of the storages.

Groundwater monitoring

A series of groundwater monitoring bores are proposed around the TSFs, to monitor

groundwater level and quality. These bores will be monitored up to 12 months prior to

commencement of deposition of tailings to provide baseline data for the project and then

quarterly throughout the life of the project.

To intercept groundwater in the confined aquifer, the bores will need to be approximately 70 m

deep with a nested bore approximately 20 m deep to confirm upward seepage from the

confined aquifer is not taking place.

The deeper bores should be constructed in accordance with the Minimum Construction

Requirements for Water Bores in Australia and screened across the first water strike

encountered. Gravel pack should be installed to at least one metre above the top of the screen

followed by a bentonite seal not less than two metres thick. The remainder of the well annulus

should be cement grouted to the surface.

A number of Vibrating Wire Piezometers (VWP) are also proposed to be installed under the

embankments to identify seepage development within the underlying foundation.

The proposed monitoring bore and VWP layout is presented in Drawing DWG-C010.


Movement monitoring

Surface movement monuments are recommended on the crest of the storages, to monitor

potential movement / settlement over the life of the facility, particularly following significant

rainfall events, spill events, and earthquake events.

Additional monuments may be installed on areas where ground conditions would lead to

increased risk of differential settlement.

Permanent survey pillars will need to be located on natural ground at strategic locations outside

the embankment to allow routine movement monitoring of the embankments.

10.3 Operation, maintenance and surveillance manual

An Operations Maintenance and Surveillance (OMS) Manual (operating manual) should be

prepared as part of the TSF Detailed Design. The principal objective of this manual is to provide

a documented operation procedure to assist in the safe and efficient storage of tailings and

water management in the TSF cells.

The OMS manual shall be prepared to meet the minimum regulatory requirements (ANCOLD,

2003 and DME, 1998) and include:

Roles and responsibilities

Design intent

Regular operations and inspections

Water and tailings management procedures

Operational requirements for mechanical equipment and instrumentation

Maintenance schedules and procedures

Surveillance requirements

Examples of potential damages and associated repair works

Definition of Critical Operating Parameters and associated Trigger Action Response Plans

The OMS manual should outline key monitoring activities which will include:

Routine reconciliation of tailings discharge tonnage and solids concentration

Tailings beach scans (nominally quarterly) to provide up to date pond storage

characteristics

Routine monitoring of tailings beach levels

Routine monitoring of pond water levels and process plant return water rates

Routine monitoring of groundwater level fluctuations

Routine assessment of groundwater and decant pond water quality

Underdrainage system return rates and volume

Annual field evaluation of tailings beach density


10.4 Dam safety emergency plan

ANCOLD (2003) states a Dam Safety Emergency Plan (DSEP) be prepared where any

persons, infrastructure or environmental values could be at risk if the dam were to fail. A DSEP

is therefore recommended for both TSFs.

The DSEP should include (but not be limited to) the following:

Critical contact details

Trigger Action Response Plans (TARPs)

Procedures in specific failure events

Emergency muster points

Dam break inundation maps

Training of site personnel, whom will be responsible for dam inspections, operation and

management, is recommended; this would include familiarisation with the OMS and DSEP.

10.5 Annual audits

Fundamental to the design of the TSF is the proposed Observational Approach and ongoing

Dam Safety Program as described throughout this document, by which there is a means of

monitoring and measuring the safe and environmentally responsible management of the TSF

throughout the full TSF life cycle. Annual Operational Reviews/Audits aim to:

Evaluate the implementation and effectiveness of the tailings management system

Reduce risk, and to drive continuous improvement

Provide assurance to company and regulatory stakeholders that the TSF is being

effectively managed in conformance with design, operational and management

commitments

Once indicators and targets are set they must be routinely monitored and reviewed to identify

any changes and areas for improvement. It is proposed that routine annual reviews are

conducted to identify trends in the data that might cause concern as early as possible. It is

essential to react to these concerns well before they impact on the integrity and performance of

the structure or the receiving environment and become increasing difficult to resolve. As

modification effort could span several years to reduce its impact on the overall operation,

addressing a major problem at a later stage might be operationally difficult, expensive, and

could even be impractical. The observational method provides the ability to address concerns

through a proactive rather than reactive approach.

Indicators and targets should be reviewed and if necessary updated during the reviews to

ensure they remain a valid and useful way of evaluating TSF performance.

10.6 TSF operator training

Effective operations and maintenance of the TSF is dependent on the staff achieving an

acceptable level of competency. To enable staff to perform their duties to this standard, staff

need to undergo training specifically addressing the operation and maintenance of tailings

facilities, which should include:

Occupational health and safety responsibilities

Operations and maintenance of the dams and outlet works components

Familiarity with the COPs and TARPs


Dam surveillance

Emergency procedures

10.7 Temporary mining and plant shutdown provisions

In the event of a temporary mining and plant shut down, there may be an extended period

without tailings deposition into the Beneficiation and Hydromet TSFs. As discussed in Section

5.3, all tailings are Non-Acid Forming and hence there is a very low risk associated with AMD

development on the tailings beaches. Normal TSF operations, surveillance and maintenance

activities would need to continue for these shutdown periods however the lack of tailings

discharge will require special provisions to control the generation of dust. The necessary

mitigation measures would depend on the period of shut-down however may include measures

such as:

Irrigation of tailings beaches with mine make-up water;

Application of dust suppression chemicals using a LGP water cart or by aerial spraying;

Temporary capping of tailings beaches with locally won earthfill.


11. References ADWG 2011. National Water Quality Management Strategy. Australian Drinking Water

Guidelines 6. Version 3.4.

AMIRA 2002. Project P387A Prediction & Kinetic Control of Acid Mine Drainage - ARD Test

Handbook. AMIRA International Limited, Melbourne.

ANCOLD 1998. Guidelines for Design of Dams for Earthquake, Australian National Committee

on Large Dams, August 1998.

ANCOLD 2000. Guidelines on Selection of Acceptable Flood Capacity for Dams, Australian

National Committee on Large Dams, March 2000.

ANCOLD 2003a. Guidelines on Dam Safety Management, Australian National Committee on

Large Dams, August 2003.

ANCOLD 2012. Guidelines on Tailings Dams Planning, Construction, Operation and Closure,

Australian National Committee on Large Dams, May 2012.

ANCOLD 2012. Guidelines on the Consequence Categories for Dams, Australian National

Committee on Large Dams, October 2012.

ANSTO. 2017. Technical Memorandum: AM/TM2017_08_04.

ANZECC & ARMCANZ. 2000. Australian and New Zealand Guidelines for Fresh and Marine

Water Quality. Australian and New Zealand Environment and Conservation Council (ANZECC)

and Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ).

ATC Williams (ATCW). 2019, Yangibana Rare Earths Project, Tailings Storage Facilities Design

Report, Document No.: Ygb-30-000-Eng-Pro-Rep-0001, 30/01/2019.

BOM 2010. Australian climate influences, Bureau of Meteorology. Available from:

http://www.bom.gov.au/climate/about/

Commonwealth Department of Industry. 2016. Preventing Acid and Metalliferous Drainage.

Manual in the Leading Practice Sustainable Development Program for the Mining Industry

series. Department of Industry, Tourism and Resources (DITR), Canberra. September 2016.

DER, Background paper on the use of leaching tests for assessing the disposal and re-use of

waste-derived materials, Government of Western Australia, Department of Environmental

Regulation, July 2015.

Desmond, A., Kendrick, P., & Chant, A. 2001. "Gascoyne 3 (GAS3 - Augustus subregion)," in A

Biodiversity Audit of Western Australia's 53 Biogeographical Subregions in 2002, N. McKenzie,

J. May, & S. McKenna eds., Department of Conservation and Land Management, pp. 240-251.

DFAT 2016. Preventing Acid and Metalliferous Drainage. Manual in the Leading Practice

Sustainable Development Program for the Mining Industry series. Canberra Department of

Foreign Affairs and Trade, (DFAT).

DME 1998. Guidelines on the Development of and Operating Manual for Tailings Storage,

Department of Minerals and Energy Western Australia, October 1998.

DMP & EPA 2015. Guidelines for Preparing Mine Closure Plans, Department of Mines and

Petroleum and Environmental Protection Agency Western Australia, May 2015.

DMP 2015. Guide to the Preparation of a Design Report for Tailings Storage Facilities (TSFs),

Department of Mines and Petroleum Western Australia, August 2015.


DMP 2010. Managing Naturally Occuring Radioactive Material (NORM) in Mining and Mineral

Processing – Guideline. NORM – 4.2. Management of Daioactive Waste: Resource Safety,

Department of Mines and Petroleum Western Australia, 21 pp, February 2010.

DMP 2013. Tailings Storage Facilities in Western Australia – Code of Practice, Resources

Safety and Environmental Divisions, Department of Mines and Petroleum Western Australia, 13

pp, 2013.

DOW 2013. Water Quality Protection Note 27 – Liners for Containing Pollutants, Using

Engineered Soils, Department of Water Western Australia, August 2013.

ERM 2019. TSF Ammonia Emissions. Environmental Resources Management Australia Pty Ltd,

May 2019.

Ewais, A.M.R., and R.K. Rowe. 2014. “Degradation of 2.4 mm-HDPE geomembrane with high

residual HP-OIT,” in 10th International Conference on Geosynthetics (10th ICG), Sept. 21-25,

2014. Berlin, Germany: International Geosynthetics Society, 2014.

GHD 2019. Technical Memorandum – Yangibanna TSF Ammonia Evolution Modelling, April

2019.

GRM 2017. DFS Study – Stage 1 Hydrogeological Assessment, Yangibana Rare Earths

Project. Report Ref J160014R01, Groundwater Resource Management, 2017.

K. Tian, C. Benson, J. Tinjum. 2017. “Chemical characteristics of leachate in low-level

radioactive waste disposal facilities.” Journal of Hazardous, Toxic, and Radioactive Waste 2017.

Kendrick, P. 2002. "Gascoyne 1 (GAS1 - Ashburton subregion)," in A Biodiversity Audit of

Western Australia's 53 Biogeographic Subregions in 2002, Department of Conservation and

Land Management, Perth, pp. 224-232.

National Environment Protection (Assessment of Site Contamination) Measure 1999 as

amended 2013. Schedule B1; Investigation Levels For Soil and Groundwater.

Paul, M. 2016. Analysis of Selenium in Difficult Samples. Thermo Fisher Scientific GmbH, Im

Steingrund 4-6, Dreiech, Germany, pp.1-3.

Peel, M.C., Finlayson, B.L., & McMahon, T.A. 2007. Updated world map of the Köppen-Geiger

climate classification. Hydrology and Earth System Sciences, vol. 11, pp. 1633-1644

Rentz, A.K., R.W.I. Brachman, W.A. Take and R.K. Rowe. 2017. “Comparison of Wrinkles in

White and Black HDPE Geomembranes.” Journal of Geotechnical and Geoenvironmental

Engineering. 143(8)

Rowe, R. K., Chappel, M. J., Brachman, R. W. I., and Take, W. A. 2012. “Field monitoring of

geomembrane wrinkles at a composite liner test site.” Canadian Geotechnical Journal, 49,

1196– 1211

Trajectory 2017. Landform Evolution Study. Hastings Technology Metals Limited Yangibana

Rare Earths Project. Trajectory.

Trajectory and GCA 2017. Tailings Characterisation Report. Hastings Technology Metals

Limited Yangibana Rare Earths Project. Trajectory and Graeme Campbell & Associates PTY

LTD.

Trajectory and GCA 2018. Tailings Leach Study Report. Hastings Technology Metals Limited

Yangibana Rare Earths Project. Trajectory and Graeme Campbell & Associates PTY LTD.

US-EPA. 2017, “Validated Test Method 1313: Liquid-Solid Partitioning as a Function of Extract

pH Using a Parallel Batch Extraction Procedure” United States Environmental Protection

Agency, pp. 3.


WADEC. 2009. Landfill Waste Classification and Waste Definitions 1996 (As amended

December 2009). Perth: Western Australia Department of Environment and Conservation.

Refer also to the Basis of Design documentation listed in Table 4-1 and Table 4-2 of this report.

GHD | Report for Hastings Technology Metals Limited - Yangibana TSF Design Development, 3219134

Appendices

GHD | Report for Hastings Technology Metals Limited - Yangibana TSF Design Development, 3219134 |

Appendix ADesign Drawings

GHD | Report for Hastings Technology Metals Limited- Yangibana TSF Design Development, 3219134

Appendix BTailings Test Results, Geotechnical

Column Sedimentation Test - Results SYD1900567.3

Client: Hastings Technology Metals Ltd Job No: 3219134Project: Yangibana GHD Sample No: SYD19-0110-01

Location: Option Study Client ID: Pilot Plant Combined Beneficiation Tailings

Settlement data

Time (hrs)Slurry Height

(mm)Volume (%)

0.01 306 100 Test Data0.03 306 1000.06 306 100 Total mass of tailings+cylinder (g): 19390 Date Commenced: 20/03/20190.13 306 100 Mass cylinder (g): 7551 Date Completed:0.25 306 100 Mass tailings (g): 11839 Tested by: ZK0.50 305 100 Initial Volume tailings (cm³): 8675.98 Checked By:1.00 304 99 Volume of tailings at NC (cm3): 5812.342.00 301 98 Final Volume of tailings (cm3): 4947.583.00 299 984.00 295 96 ESTIMATED NORMALLY ESTIMATED FINAL UNDRAINED

5.00 293 96 INITIAL TEST CONDITIONS CONSOLIDATED TEST CONDITIONS TEST CONDITIONS

6.00 290 95 Solids: 40 Solids: 75 Solids: 867.00 288 94 Saturation: 100% Saturation: 100% Saturation: 100%8.00 285.5 93 eo: 4.643 ef: 2.780 ef: 2.21823.50 261 85 sat: 1.365 sat: 2.037 sat: 2.39330.33 253 83 dry: 0.546 dry: 0.815 dry: 0.95748.00 236 77 w: 150% w: 33% w: 16%56.00 230 75

120.00 208 68143.00 205 67 end primary167.25 203.5 67216.00 202 66288.25 201 66

290 200 65292.00 199 65290.43 198 65292.50 195 64294.50 193 63311.50 184 60337.00 179.5 59 TEST CONDITIONS362.75 178 58 Cylinder Diameter (mm): 190485.00 174.5 57 Initial Ht of Test (mm): 306.0

Final height of Sediment (mm): 201.0Water Type: As received

Apparent Particle Density: 3.08Initial Mass of Tailings (g): 11839

Initial Moisture content calculated from densities (%): 150NC Moisture content calculated from densities (%): 33

Final Moisture content calculated from densities (%): 16

25

50

75

100

125

0.0 0.1 1.0 10.0 100.0 1000.0

Slu

rry

volu

me

%

Time (hrs)

Undrained settlement

Drained settlement

GHD GeotechnicsUnit 5, 43 Herbert St Artarmon NSWp: (02) 9462 4860f: (02) 9462 4710

Column Sedimentation Test Permeability Stage Report No: SYD1702548

Client: Hastings Technology Metals Ltd Job No : Sample No: SYD19-0110-01

Client ID:

Project: Yangibana Report No : SYD1900567.3

Area m2 0.0284Date & time Time Elapsed

Time (hrs)

1 Soil height (mm)

1 Water Height (mm)

Hydraulic Gradient

Flow rate mls / hr

2 k (m/s) from Water Height

Change

Collected Seepage

(mls)

Seepage Flow Rate

(m 3 /s)

2 k (m/s) from Collected Seepage

Comment

1/04/2019 1:57:00 AM 0 201 306 1.52 01/04/2019 4:30:00 PM 4.55 193 292 1.51 59.8 5.6E-07 272 1.7E-08 3.9E-07 Draining2/04/2019 9:30:00 AM 21.55 184 281 1.53 18.2 1.2E-07 309.8 5.1E-09 1.2E-07 Draining3/04/2019 11:00am 47.05 179.5 269 1.50 12.5 8.6E-08 318.8 3.5E-09 8.1E-08 Draining4/04/2019 12:45:00 PM 72.8 178 259 1.46 11.5 7.3E-08 295.7 3.2E-09 7.6E-08 Draining5/04/2019 3:00:00 PM 99.05 177 249 1.41 10.9 7.4E-08 284.9 3.0E-09 7.4E-08 refill to 291

99.05 177 291 1.41 10.9 7.4E-08 3.0E-09 7.4E-088/04/2019 12:40:00 PM 168.72 175 263.5 1.51 11.9 7.5E-08 826.2 3.3E-09 8.0E-089/04/2019 3:00:00 PM 195.05 174.5 253 1.45 11.3 7.5E-08 296.9 3.1E-09 7.5E-08

3 k= 7.5E-08

Notes Shearvane tests at end of test NotesVane size: 50mm (readable to 0.07 kPa) 1. From base of sample

Upper Test Lower Test 2. Between consecutive recordsPeak (kPa): 3. From change in water height

Residual (kPa):

3219134.00

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

0 50 100 150 200 250

mls per hour

Time hrs

Flow rate mls / hr

1.0E‐09

1.1E‐08

2.1E‐08

3.1E‐08

4.1E‐08

5.1E‐08

6.1E‐08

7.1E‐08

8.1E‐08

9.1E‐08

0 50 100 150 200 250

m/s

time hrs

Permeability m/s

Seepage Flow Rate (m3/s)

2k (m/s) from Collected Seepage

GHD GeotechnicsUnit 5 / 43 Herbert St Artarmon NSWp: (02) 9462 4700f: (02) 9462 4710

Column Sedimentation Test - Report Report No: SYD1900567.2

Client: Hastings Technology Metals Ltd Job No: 3219134Project: Yangibana GHD Sample No: SYD19-0110-02

Location: Option Study Client ID: Pilot Plant

Settlement data

Time (hrs)Slurry Height

(mm)Volume (%) SAMPLE AERATED WHEN MIXED, AIR REMOVED INSITU & SAMPLE PLUNGED TO REMIX

20/03/2019 0.01 295 100 Test Data0.03 295 1000.06 295 100 Total mass of tailings+cylinder (g): 23842 Date Commenced: 20/03/20190.13 295 100 Mass cylinder (g): 12717 Date Completed: 10/05/20190.25 295 100 Mass tailings (g): 11125 Tested by: ZK0.50 295 100 Initial Volume tailings (cm³): 8364.10 Checked By: DB1.00 294 100 Volume of tailings at NC (cm3): 6010.812.00 292 99 Final Volume of tailings (cm3): 5089.343.00 291 994.00 290 98 ESTIMATED NORMALLY ESTIMATED FINAL UNDRAINED

5.00 289 98 INITIAL TEST CONDITIONS CONSOLIDATED TEST CONDITIONS TEST CONDITIONS

6.00 286 97 Solids: 37 Solids: 68 Solids: 807.00 284 96 Saturation: 100% Saturation: 100% Saturation: 100%

8.00 283 96 eo: 5.310 ef: 3.534 ef: 2.839

23.50 265 90 sat: 1.330 sat: 1.851 sat: 2.18630.33 259 88 dry: 0.488 dry: 0.679 dry: 0.80248.00 246 83 w: 172% w: 47% w: 24%56.00 241 82120.00 218 74 Shearvane after draining: 1.0 kPa143.00 214.5 73 50mm vane167.25 212 72 end primary216.00 210 71 Moisture content after draining: 56.2%288.25 208.5 71

Drained 290 206.5 70292.00 206 70290.43 204 69292.50 201 68294.50 200 68311.50 190 64337.00 185 63 TEST CONDITIONS362.75 183 62 Cylinder Diameter (mm): 190485.00 179.5 61 Initial Ht of Test (mm): 295.0

Final height of Sediment (mm): 179.5Water Type: As received

Apparent Particle Density: 3.08Initial Mass of Tailings (g): 11125

Initial Moisture content calculated from densities (%): 172NC Moisture content calculated from densities (%): 47

Final Moisture content calculated from densities (%): 24

50

55

60

65

70

75

80

85

90

95

100

105

0.0 0.1 1.0 10.0 100.0 1000.0

Sa

mp

le V

olu

me

(%

)

Time (hrs)

Drained settlement

Undrained settlement

GHD GeotechnicsUnit 5, 43 Herbert St Artarmon NSWp: (02) 9462 4860f: (02) 9462 4710

Column Sedimentation Test Permeability Stage Report No: SYD1702548

Client: Hastings Technology Metals Ltd Job No : Sample No: SYD19-0110-02

Client ID:

Project: Yangibana Report No : SYD1900567.2

Area m2 0.0284Date Time Elapsed Time

(hrs)

1 Soil height (mm)

1 Water Height (mm)

Hydraulic Gradient

Flow rate mls

/ hr

2 k (m/s) from Water Height

Change

Collected Seepage

(mls)

Seepage Flow Rate

(m 3 /s)

2 k (m/s) from Collected Seepage

Comment

1/04/2019 11:57:00 PM 0 208.5 295 1.41 0 Draining1/04/2019 4.55 200 284.5 1.42 67.1 4.5E-07 305.3 1.9E-08 4.6E-07 Draining2/04/2019 21.55 190 273 1.44 15.9 1.3E-07 269.9 4.4E-09 1.1E-07 Draining3/04/2019 47.05 185 262 1.42 11.5 8.4E-08 293.8 3.2E-09 7.9E-08 Draining4/04/2019 72.8 183 253 1.38 10.3 6.9E-08 266.2 2.9E-09 7.2E-08 Draining5/04/2019 99.05 182 244 1.34 9.7 7.0E-08 255.3 2.7E-09 7.0E-08 refill to 286

99.05 182 286 1.34 9.7 2.7E-09 7.0E-088/04/2019 168.72 180 259 1.44 10.5 7.7E-08 729.7 2.9E-09 7.4E-089/04/2019 195.05 179.5 248 1.38 10.1 8.2E-08 265.8 2.8E-09 7.0E-08

3 k= 8.2E-08

Notes Shearvane tests at end of test NotesVane size: 50mm (readable to 0.07 kPa) 1. From base of sample

Upper Test Lower Test 2. Between consecutive recordsPeak (kPa): 1 - 3. From change in water height

Residual (kPa): - -

3219134.00

1.0E‐09

1.1E‐08

2.1E‐08

3.1E‐08

4.1E‐08

5.1E‐08

6.1E‐08

7.1E‐08

8.1E‐08

9.1E‐08

0 50 100 150 200 250

m/s

Time hrs

Permeability m/s

Seepage Flow Rate (m3/s)

2k (m/s) from CollectedSeepage

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

0 50 100 150 200 250

mls per hour

Time hrs

Flowrate mls/hr

GHD GeotechnicsUnit 5 / 43 Herbert St Artarmon NSWp: (02) 9462 4700f: (02) 9462 4710

0 0.00 True

Environmental

CERTIFICATE OF ANALYSISWork Order : Page : 1 of 2ES1909306

:: LaboratoryClient GHD PTY LTD Environmental Division Sydney

: :ContactContact Sarah Gilmour Customer Services ES

:: AddressAddress LEVEL 15, 133 CASTLEREAGH STREET

SYDNEY NSW, AUSTRALIA 2000

277-289 Woodpark Road Smithfield NSW Australia 2164

:Telephone ---- :Telephone +61-2-8784 8555

:Project 3219134 Yangibana TSF Option Study Date Samples Received : 27-Mar-2019 12:50

:Order number Date Analysis Commenced : 28-Mar-2019

:C-O-C number ---- Issue Date : 29-Mar-2019 09:40

Sampler : ----

Site :

Quote number : EN/005/18

1:No. of samples received

1:No. of samples analysed

This report supersedes any previous report(s) with this reference. Results apply to the sample(s) as submitted. This document shall not be reproduced, except in full.

This Certificate of Analysis contains the following information:

l General Comments

l Analytical Results

Additional information pertinent to this report will be found in the following separate attachments: Quality Control Report, QA/QC Compliance Assessment to assist with

Quality Review and Sample Receipt Notification.

SignatoriesThis document has been electronically signed by the authorized signatories below. Electronic signing is carried out in compliance with procedures specified in 21 CFR Part 11.

Signatories Accreditation CategoryPosition

Dian Dao Sydney Inorganics, Smithfield, NSW

R I G H T S O L U T I O N S | R I G H T P A R T N E R

Combined Benefication Tailings Column Test Bleed Water TSS

2 of 2:Page

Work Order :

:Client

ES1909306

3219134 Yangibana TSF Option Study:Project

GHD PTY LTD

General Comments

The analytical procedures used by the Environmental Division have been developed from established internationally recognized procedures such as those published by the USEPA, APHA, AS and NEPM. In house

developed procedures are employed in the absence of documented standards or by client request.

Where moisture determination has been performed, results are reported on a dry weight basis.

Where a reported less than (<) result is higher than the LOR, this may be due to primary sample extract/digestate dilution and/or insufficient sample for analysis.

Where the LOR of a reported result differs from standard LOR, this may be due to high moisture content, insufficient sample (reduced weight employed) or matrix interference.

When sampling time information is not provided by the client, sampling dates are shown without a time component. In these instances, the time component has been assumed by the laboratory for processing

purposes.

Where a result is required to meet compliance limits the associated uncertainty must be considered. Refer to the ALS Contact for details.

CAS Number = CAS registry number from database maintained by Chemical Abstracts Services. The Chemical Abstracts Service is a division of the American Chemical Society.

LOR = Limit of reporting

^ = This result is computed from individual analyte detections at or above the level of reporting

ø = ALS is not NATA accredited for these tests.

~ = Indicates an estimated value.

Key :

Analytical Results

----------------Yangibana DecantClient sample IDSub-Matrix: WATER

(Matrix: WATER)

----------------22-Mar-2019 00:00Client sampling date / time

--------------------------------ES1909306-001UnitLORCAS NumberCompound

Result ---- ---- ---- ----

EA025: Total Suspended Solids dried at 104 ± 2°C

88 ---- ---- ---- ----mg/L1----Suspended Solids (SS)

Yangibana TSF Option StudyLocationSILT: brown (Tailings)Soil Description

Sample DetailsSYD19-0110-01GHD Sample NoSampled By ClientSampled By01/03/2019Date Sampled

Test Results

Standard0.00.0

1.0862.867.7

Syd tap water30

2 E-0912/03/2019

150Result

Moisture Content (%) AS 1289.2.1.1MethodDescription Limits

Date TestedCoef of Permeability (m/sec) AS 1289.6.7.3Mean Stress Level (kPa)Permeant UsedLength (mm)Diameter (mm)Length/Diameter RatioLaboratory Moisture Ratio (%)Laboratory Density Ratio (%)CompactiveEffort

RemouldedMethod of Compaction0.0Surcharge Applied (Kg)10Pressure Applied (Kpa)

6.3Oversize Sieve (mm)0.0Percentage Oversize (%)

25.9Moisture Content (%)22/03/2019Date Tested

Sydney Laboratory Unit 5/43 Herbert StArtarmon NSW 2064email: [email protected]: www.ghd.com.au/ghdgeotechnicsTel: (02) 9462 4860Fax:(02) 9462 4710

Aggregate/Soil Test Report Report No: SYD1900567Issue No: 2

This report replaces all previous issues of report no 'SYD1900567'.Accredited for compliance with ISO / IEC 17025 -Testing

10/05/2019NATA Accredited

Laboratory Number:679 Date of Issue:

THIS DOCUMENT SHALL NOT BE REPRODUCED EXCEPT IN FULL

Client:

Project: 3219134

Hastings Technology Metals LimitedPerth WA 6000167 St George Terrace

Approved Signatory: D.P Brooke (Sydney Laboratory Manager)

Page 1 of 1© 2000-2016 QESTLab by SpectraQEST.comForm No: 18909, Report No: SYD1900567

Moisture and Density Ratio's not applicable.Sample intial dry density = 1.825 t/m³ and MC = 21.9 %Sample final dry density = 1.821 t/m³ and MC = 25.9 %

Comments

Trial Hole: -Depth (m): -Sample No: SYD19-0110-01

Client: Hastings Technology Metals Limited Client Sample No.: -

Project: Yangibana TSF Sample History:Location: Options Study

TEST METHODSParticle size AS1289.3.6.3

OTHER TESTS AS1289.3.1.1 AS1289.3.2.1 AS1289.3.3.1 AS1289.3.4.1 AS1289.3.5.1

GRADINGCu = D60 / D10 = 22.02Cc = D30² / (D10 x D60) = 0.71

PARTICLE DENSITY 3.08 (measured) INDEX PROPERTIES (%)Liquid Limit = 24 Plastic Limit = 21

PRE-TREATMENT HYDROMETER No Plasticity Index = 3 Linear Shrinkage % =4.0

TEST CONDITION Washed sieve with dispersing agent Atterberg Limits (History/Preparation) Oven Dried

GROUP SYMBOL: Liquid Limit (type of test) 4 Point

Linear Shrinkage (mould size) 125 mmSOIL NAME: SILT: brown

REMARKS:

Tested by: AM GHD Pty Ltd Date tested: 27.03.19 Unit 5, 43 Herbert St, Artarmon NSW, 2064 Checked by: GV Tel: (02) 9462 4700 Fax: (02) 9462 4710 Date checked: 10/05/2019 Approved Signatory:

JOB No. 3219134

REPORT No. SYD1900567.1D. Brooke 10/05/2019 Ref: Document F9.1.16 issue 1.2

This laboratory Certificate may not be reproduced except in full unless permission for the publication of anapproved extract has been obtained in writing from GHD Pty Ltd

Laboratory Accreditation Number - 679

Accredited for compliance with ISO/IEC 17025 -Testing

10010010010099

72

52

46

42

3633

26

21

1614

106

AS SIEVE SIZE (mm) 0.07

5

0.15

0.21

2

0.3

0.42

5

0.6

1.18

2.36

4.75

6.7

9.5

13.2

19 26.5

37.5

53 75 200

0

10

20

30

40

50

60

70

80

90

1000

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10 100 1000

PE

RC

EN

TA

GE

RE

TA

INE

D

PE

RC

EN

TA

GE

PA

SS

ING

Medium Coarse Fine

SILT FRACTION SAND FRACTION GRAVEL FRACTION

CL

AY

COBBLES BOULDERS

0.002 0.006 0.02 0.075 0.2 0.6 6 20 63 200

CoarseMediumFine CoarseMediumFine

2.36

PARTICLE SIZE (mm)

SOIL CLASSIFICATION REPORT

Sampled By GHD

0

50

0 50 100

CL

MLOL

CH

MHOH

IP

Liquid limit (WL)

GHD | Report for Hastings Technology Metals Ltd - Yangibana TSF Design Development, 3219134

Appendix CCombined Beneficiation Tailings Test Results, Geochemical

0 0.00 True

Environmental


:Amendment 1:: LaboratoryClient GHD PTY LTD Environmental Division Sydney

: :ContactContact Sarah Gilmour Shirley LeCornu

:: AddressAddress 2 SALAMANCA SQUARE

HOBART TAS, AUSTRALIA 7000


:Telephone ---- :Telephone +6138549 9630

:Project 3219134 Date Samples Received : 08-Mar-2019 08:15

:Order number 3219134 Date Analysis Commenced : 11-Mar-2019

:C-O-C number ---- Issue Date : 23-Apr-2019 10:50

Sampler : Narelle Marriott (Hastings)

Site : Hasting's Yangibana Project

Quote number : ME/158/19





l General Comments






Ankit Joshi Inorganic Chemist Sydney Inorganics, Smithfield, NSW

Ivan Taylor Analyst Sydney Inorganics, Smithfield, NSW

Satishkumar Trivedi Senior Acid Sulfate Soil Chemist Brisbane Acid Sulphate Soils, Stafford, QLD

Wisam Marassa Inorganics Coordinator Sydney Inorganics, Smithfield, NSW


2 of 16:Page

Work Order :

:Client

ES1907149 Amendment 1

3219134:Project

GHD PTY LTD

General Comments







purposes.







Key :

ED041G: LOR raised for Sulfate on samples 10 and 12 due to sample matrix.l

EN055: Ionic Balance out of acceptable limits for various samples due to analytes not quantified in this report.l

ASS: EA013 (ANC) Fizz Rating: 0- None; 1- Slight; 2- Moderate; 3- Strong; 4- Very Strong; 5- Lime.l

(ADD METHOD): NATA accreditation does not cover performance of this service.l

EA016: Calculated TDS is determined from Electrical conductivity using a conversion factor of 0.65.l

EA046 ABCC: NATA Acreditation does not cover the performance of this service.l

Sodium Adsorption Ratio (where reported): Where results for Na, Ca or Mg are <LOR, a concentration at half the reported LOR is incorporated into the SAR calculation. This represents a conservative approach

for Na relative to the assumption that <LOR = zero concentration and a conservative approach for Ca & Mg relative to the assumption that <LOR is equivalent to the LOR concentration.

l

3 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

2018 bene combined

tailings

T05 - pH 8.0

2018 bene combined

tailings

T04 - pH 9.0

2018 bene combined

tailings

T03 - pH 10.5

2018 bene combined

tailings

T02 - pH 12.0

2018 bene combined

tailings

T01 - pH 13.0

Client sample IDSub-Matrix: LEACHATE

(Matrix: WATER)

26-Nov-2018 00:0026-Nov-2018 00:0026-Nov-2018 00:0026-Nov-2018 00:0026-Nov-2018 00:00Client sampling date / time

ES1907149-006ES1907149-005ES1907149-004ES1907149-003ES1907149-002UnitLORCAS NumberCompound

Result Result Result Result Result

EA005P: pH by PC Titrator

12.8 11.9 10.0 9.09 8.10pH Unit0.01----pH Value

EA010P: Conductivity by PC Titrator

32800 1070 213 259 341µS/cm1----Electrical Conductivity @ 25°C

EA016: Calculated TDS (from Electrical Conductivity)

21300 696 138 168 222mg/L1----Total Dissolved Solids (Calc.)

EA065: Total Hardness as CaCO3

<1 <1 <1 284 36mg/L1----Total Hardness as CaCO3

ED037P: Alkalinity by PC Titrator

6140Hydroxide Alkalinity as CaCO3 103 <1 <1 <1mg/L1DMO-210-001

761Carbonate Alkalinity as CaCO3 340 20 7 <1mg/L13812-32-6

<1Bicarbonate Alkalinity as CaCO3 <1 64 38 42mg/L171-52-3

6900 443 84 45 42mg/L1----Total Alkalinity as CaCO3

ED041G: Sulfate (Turbidimetric) as SO4 2- by DA

4Sulfate as SO4 - Turbidimetric 5 6 <1 <1mg/L114808-79-8

ED045G: Chloride by Discrete Analyser

23Chloride 11 11 <1 <1mg/L116887-00-6

ED093F: Dissolved Major Cations

<1Calcium <1 <1 3 11mg/L17440-70-2

<1Magnesium <1 <1 <1 2mg/L17439-95-4

3710Sodium 223 54 58 66mg/L17440-23-5

9Potassium 2 2 2 3mg/L17440-09-7

EG020T: Total Metals by ICP-MS

15.7Aluminium 2.37 4.33 0.02 0.02mg/L0.017429-90-5

<0.001Dysprosium <0.001 0.007 <0.001 <0.001mg/L0.0017429-91-6

<0.001Silver <0.001 <0.001 <0.001 <0.001mg/L0.0017440-22-4

0.021Arsenic 0.007 0.006 <0.001 <0.001mg/L0.0017440-38-2

<0.001Bismuth <0.001 <0.001 <0.001 <0.001mg/L0.0017440-69-9

<0.001Erbium <0.001 0.002 <0.001 <0.001mg/L0.0017440-52-0

0.08Boron 0.06 0.28 <0.05 <0.05mg/L0.057440-42-8

<0.001Europium <0.001 0.007 <0.001 <0.001mg/L0.0017440-53-1

0.006Strontium 0.002 0.044 0.019 0.076mg/L0.0017440-24-6

0.182Barium 0.144 1.51 0.158 0.483mg/L0.0017440-39-3

4 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

2018 bene combined

tailings

T05 - pH 8.0

2018 bene combined

tailings

T04 - pH 9.0

2018 bene combined

tailings

T03 - pH 10.5

2018 bene combined

tailings

T02 - pH 12.0

2018 bene combined

tailings

T01 - pH 13.0


(Matrix: WATER)




EG020T: Total Metals by ICP-MS - Continued

<0.001Gadolinium <0.001 0.019 <0.001 <0.001mg/L0.0017440-54-2

<0.01Titanium <0.01 0.14 <0.01 <0.01mg/L0.017440-32-6

<0.001Beryllium <0.001 0.003 <0.001 <0.001mg/L0.0017440-41-7

0.005Gallium 0.003 0.013 <0.001 <0.001mg/L0.0017440-55-3

<0.0001Cadmium <0.0001 0.0003 0.0001 <0.0001mg/L0.00017440-43-9

<0.01Hafnium <0.01 <0.01 <0.01 <0.01mg/L0.017440-58-6

<0.005Tellurium <0.005 <0.005 <0.005 <0.005mg/L0.00522541-49-7

<0.001Cobalt <0.001 0.008 <0.001 <0.001mg/L0.0017440-48-4

<0.001Holmium <0.001 <0.001 <0.001 <0.001mg/L0.0017440-60-0

0.064Uranium 0.002 0.006 0.002 0.002mg/L0.0017440-61-1

<0.001Caesium <0.001 0.005 <0.001 <0.001mg/L0.0017440-46-2

0.004Chromium 0.001 0.013 <0.001 <0.001mg/L0.0017440-47-3

<0.001Indium <0.001 <0.001 <0.001 <0.001mg/L0.0017440-74-6

0.004Copper 0.002 0.017 0.004 0.004mg/L0.0017440-50-8

<0.001Lanthanum 0.002 0.084 <0.001 <0.001mg/L0.0017439-91-0

0.016Rubidium 0.003 0.059 0.003 0.005mg/L0.0017440-17-7

<0.001Lithium <0.001 0.022 0.004 0.009mg/L0.0017439-93-2

<0.001Lutetium <0.001 <0.001 <0.001 <0.001mg/L0.0017439-94-3

<0.001Thorium <0.001 0.044 <0.001 <0.001mg/L0.0017440-29-1

0.002Cerium 0.009 0.349 0.002 0.001mg/L0.0017440-45-1

0.005Manganese 0.061 2.35 0.054 0.034mg/L0.0017439-96-5

0.001Neodymium 0.008 0.273 0.001 <0.001mg/L0.0017440-00-8

0.064Molybdenum 0.037 0.010 0.024 0.020mg/L0.0017439-98-7

<0.001Praseodymium 0.002 0.060 <0.001 <0.001mg/L0.0017440-10-0

<0.001Nickel <0.001 0.012 <0.001 <0.001mg/L0.0017440-02-0

<0.001Samarium <0.001 0.031 <0.001 <0.001mg/L0.0017440-19-9

0.005Lead 0.003 0.127 0.001 <0.001mg/L0.0017439-92-1

<0.001Terbium <0.001 0.002 <0.001 <0.001mg/L0.0017440-27-9

<0.001Antimony <0.001 <0.001 <0.001 <0.001mg/L0.0017440-36-0

<0.001Thulium <0.001 <0.001 <0.001 <0.001mg/L0.0017440-30-4

<0.01Selenium <0.01 <0.01 <0.01 <0.01mg/L0.017782-49-2

<0.001Ytterbium <0.001 <0.001 <0.001 <0.001mg/L0.0017440-64-4

0.054Tin 0.002 <0.001 <0.001 <0.001mg/L0.0017440-31-5

5 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

2018 bene combined

tailings

T05 - pH 8.0

2018 bene combined

tailings

T04 - pH 9.0

2018 bene combined

tailings

T03 - pH 10.5

2018 bene combined

tailings

T02 - pH 12.0

2018 bene combined

tailings

T01 - pH 13.0


(Matrix: WATER)





<0.001Yttrium <0.001 0.018 <0.001 <0.001mg/L0.0017440-65-5

<0.001Thallium <0.001 <0.001 <0.001 <0.001mg/L0.0017440-28-0

<0.005Zirconium <0.005 <0.005 <0.005 <0.005mg/L0.0057440-67-7

0.21Vanadium 0.10 0.05 <0.01 <0.01mg/L0.017440-62-2

0.075Zinc 0.196 0.291 0.019 0.167mg/L0.0057440-66-6

0.07Iron 0.50 16.1 0.07 <0.05mg/L0.057439-89-6

EG035T: Total Recoverable Mercury by FIMS

<0.0001Mercury <0.0001 <0.0001 <0.0001 <0.0001mg/L0.00017439-97-6

EK040P: Fluoride by PC Titrator

4.8Fluoride 0.5 0.6 0.6 0.6mg/L0.116984-48-8

6 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

2018 bene combined

tailings

B01

2018 bene combined

tailings

T09 - pH 2.0

2018 bene combined

tailings

T08 - pH 4.0

2018 bene combined

tailings

T07 - pH 5.5

2018 bene combined

tailings

T06 - pH Neutral


(Matrix: WATER)





6.44 5.63 3.52 1.96 6.64pH Unit0.01----pH Value


658 702 1020 8260 <1µS/cm1----Electrical Conductivity @ 25°C


428 456 663 5370 <1mg/L1----Total Dissolved Solids (Calc.)


122 138 225 253 <1mg/L1----Total Hardness as CaCO3


<1Hydroxide Alkalinity as CaCO3 <1 <1 <1 <1mg/L1DMO-210-001

<1Carbonate Alkalinity as CaCO3 <1 <1 <1 <1mg/L13812-32-6

15Bicarbonate Alkalinity as CaCO3 8 <1 <1 <1mg/L171-52-3

15 8 <1 <1 <1mg/L1----Total Alkalinity as CaCO3


6Sulfate as SO4 - Turbidimetric <1 <1 <10 <1mg/L114808-79-8


12Chloride <1 <1 11 <1mg/L116887-00-6


34Calcium 39 62 65 <1mg/L17440-70-2

9Magnesium 10 17 22 <1mg/L17439-95-4

70Sodium 73 76 73 <1mg/L17440-23-5

5Potassium 6 10 17 <1mg/L17440-09-7


0.03Aluminium 0.01 4.39 19.5 0.01mg/L0.017429-90-5

<0.001Dysprosium <0.001 0.010 0.057 <0.001mg/L0.0017429-91-6

<0.001Silver <0.001 <0.001 <0.001 <0.001mg/L0.0017440-22-4

<0.001Arsenic <0.001 0.004 0.034 <0.001mg/L0.0017440-38-2

<0.001Bismuth <0.001 <0.001 <0.001 <0.001mg/L0.0017440-69-9

<0.001Erbium <0.001 0.003 0.015 <0.001mg/L0.0017440-52-0

0.18Boron 0.07 0.34 0.53 <0.05mg/L0.057440-42-8

<0.001Europium <0.001 0.008 0.051 <0.001mg/L0.0017440-53-1

0.295Strontium 0.378 0.737 0.886 0.005mg/L0.0017440-24-6

1.38Barium 1.04 5.18 13.8 0.088mg/L0.0017440-39-3

7 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

2018 bene combined

tailings

B01

2018 bene combined

tailings

T09 - pH 2.0

2018 bene combined

tailings

T08 - pH 4.0

2018 bene combined

tailings

T07 - pH 5.5

2018 bene combined

tailings

T06 - pH Neutral


(Matrix: WATER)





<0.001Gadolinium <0.001 0.024 0.143 <0.001mg/L0.0017440-54-2

<0.01Titanium <0.01 <0.01 0.01 <0.01mg/L0.017440-32-6

<0.001Beryllium <0.001 0.054 0.076 <0.001mg/L0.0017440-41-7

<0.001Gallium <0.001 0.013 0.094 <0.001mg/L0.0017440-55-3

0.0004Cadmium 0.0004 0.0033 0.0042 <0.0001mg/L0.00017440-43-9

<0.01Hafnium <0.01 <0.01 <0.01 <0.01mg/L0.017440-58-6

<0.005Tellurium <0.005 <0.005 <0.005 <0.005mg/L0.00522541-49-7

<0.001Cobalt 0.004 0.059 0.141 <0.001mg/L0.0017440-48-4

<0.001Holmium <0.001 0.001 0.007 <0.001mg/L0.0017440-60-0

<0.001Uranium <0.001 0.023 0.265 <0.001mg/L0.0017440-61-1

<0.001Caesium <0.001 <0.001 0.001 <0.001mg/L0.0017440-46-2

<0.001Chromium <0.001 0.006 0.080 <0.001mg/L0.0017440-47-3

<0.001Indium <0.001 <0.001 <0.001 <0.001mg/L0.0017440-74-6

0.004Copper 0.004 0.030 0.198 <0.001mg/L0.0017440-50-8

<0.001Lanthanum 0.003 0.103 0.860 <0.001mg/L0.0017439-91-0

0.011Rubidium 0.016 0.043 0.148 <0.001mg/L0.0017440-17-7

0.022Lithium 0.024 0.044 0.103 <0.001mg/L0.0017439-93-2

<0.001Lutetium <0.001 <0.001 0.001 <0.001mg/L0.0017439-94-3

0.002Thorium <0.001 <0.001 0.053 <0.001mg/L0.0017440-29-1

0.001Cerium 0.006 0.329 2.36 <0.001mg/L0.0017440-45-1

1.03Manganese 2.40 13.3 35.0 0.014mg/L0.0017439-96-5

<0.001Neodymium 0.004 0.290 2.15 <0.001mg/L0.0017440-00-8

<0.001Molybdenum <0.001 <0.001 <0.001 <0.001mg/L0.0017439-98-7

<0.001Praseodymium <0.001 0.064 0.555 <0.001mg/L0.0017440-10-0

0.005Nickel 0.012 0.045 0.080 <0.001mg/L0.0017440-02-0

<0.001Samarium <0.001 0.035 0.238 <0.001mg/L0.0017440-19-9

<0.001Lead <0.001 0.014 1.04 <0.001mg/L0.0017439-92-1

<0.001Terbium <0.001 0.003 0.015 <0.001mg/L0.0017440-27-9

<0.001Antimony <0.001 <0.001 <0.001 <0.001mg/L0.0017440-36-0

<0.001Thulium <0.001 <0.001 0.001 <0.001mg/L0.0017440-30-4

<0.01Selenium <0.01 <0.01 0.04 <0.01mg/L0.017782-49-2

<0.001Ytterbium <0.001 0.002 0.008 <0.001mg/L0.0017440-64-4

<0.001Tin <0.001 <0.001 <0.001 <0.001mg/L0.0017440-31-5

8 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

2018 bene combined

tailings

B01

2018 bene combined

tailings

T09 - pH 2.0

2018 bene combined

tailings

T08 - pH 4.0

2018 bene combined

tailings

T07 - pH 5.5

2018 bene combined

tailings

T06 - pH Neutral


(Matrix: WATER)





<0.001Yttrium <0.001 0.033 0.162 <0.001mg/L0.0017440-65-5

<0.001Thallium <0.001 <0.001 0.004 <0.001mg/L0.0017440-28-0

<0.005Zirconium <0.005 <0.005 <0.005 <0.005mg/L0.0057440-67-7

<0.01Vanadium <0.01 <0.01 <0.01 <0.01mg/L0.017440-62-2

0.585Zinc 0.689 1.21 1.58 0.014mg/L0.0057440-66-6

<0.05Iron <0.05 <0.05 26.7 <0.05mg/L0.057439-89-6


<0.0001Mercury <0.0001 <0.0001 <0.0001 <0.0001mg/L0.00017439-97-6


0.3Fluoride 0.2 1.2 1.0 <0.1mg/L0.116984-48-8

9 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

------------2018 bene combined

tailings

B03

2018 bene combined

tailings

B02


(Matrix: WATER)

------------26-Nov-2018 00:0026-Nov-2018 00:00Client sampling date / time

------------------------ES1907149-013ES1907149-012UnitLORCAS NumberCompound

Result Result ---- ---- ----


1.74 12.9 ---- ---- ----pH Unit0.01----pH Value


13300 35600 ---- ---- ----µS/cm1----Electrical Conductivity @ 25°C


8640 23100 ---- ---- ----mg/L1----Total Dissolved Solids (Calc.)


<1 <1 ---- ---- ----mg/L1----Total Hardness as CaCO3


<1Hydroxide Alkalinity as CaCO3 6120 ---- ---- ----mg/L1DMO-210-001

<1Carbonate Alkalinity as CaCO3 1050 ---- ---- ----mg/L13812-32-6

<1Bicarbonate Alkalinity as CaCO3 <1 ---- ---- ----mg/L171-52-3

<1 7180 ---- ---- ----mg/L1----Total Alkalinity as CaCO3


<10Sulfate as SO4 - Turbidimetric <1 ---- ---- ----mg/L114808-79-8


<1Chloride 11 ---- ---- ----mg/L116887-00-6


<1Calcium <1 ---- ---- ----mg/L17440-70-2

<1Magnesium <1 ---- ---- ----mg/L17439-95-4

<1Sodium 3800 ---- ---- ----mg/L17440-23-5

<1Potassium 1 ---- ---- ----mg/L17440-09-7


0.02Aluminium 0.17 ---- ---- ----mg/L0.017429-90-5

<0.001Dysprosium <0.001 ---- ---- ----mg/L0.0017429-91-6

<0.001Silver <0.001 ---- ---- ----mg/L0.0017440-22-4

<0.001Arsenic <0.001 ---- ---- ----mg/L0.0017440-38-2

<0.001Bismuth <0.001 ---- ---- ----mg/L0.0017440-69-9

<0.001Erbium <0.001 ---- ---- ----mg/L0.0017440-52-0

<0.05Boron <0.05 ---- ---- ----mg/L0.057440-42-8

<0.001Europium <0.001 ---- ---- ----mg/L0.0017440-53-1

<0.001Strontium 0.011 ---- ---- ----mg/L0.0017440-24-6

0.020Barium 0.453 ---- ---- ----mg/L0.0017440-39-3

10 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results


tailings

B03

2018 bene combined

tailings

B02


(Matrix: WATER)





<0.001Gadolinium <0.001 ---- ---- ----mg/L0.0017440-54-2

<0.01Titanium <0.01 ---- ---- ----mg/L0.017440-32-6

<0.001Beryllium <0.001 ---- ---- ----mg/L0.0017440-41-7

<0.001Gallium <0.001 ---- ---- ----mg/L0.0017440-55-3

<0.0001Cadmium <0.0001 ---- ---- ----mg/L0.00017440-43-9

<0.01Hafnium <0.01 ---- ---- ----mg/L0.017440-58-6

<0.005Tellurium <0.005 ---- ---- ----mg/L0.00522541-49-7

<0.001Cobalt <0.001 ---- ---- ----mg/L0.0017440-48-4

<0.001Holmium <0.001 ---- ---- ----mg/L0.0017440-60-0

<0.001Uranium <0.001 ---- ---- ----mg/L0.0017440-61-1

<0.001Caesium <0.001 ---- ---- ----mg/L0.0017440-46-2

<0.001Chromium <0.001 ---- ---- ----mg/L0.0017440-47-3

<0.001Indium <0.001 ---- ---- ----mg/L0.0017440-74-6

<0.001Copper 0.005 ---- ---- ----mg/L0.0017440-50-8

<0.001Lanthanum <0.001 ---- ---- ----mg/L0.0017439-91-0

<0.001Rubidium <0.001 ---- ---- ----mg/L0.0017440-17-7

<0.001Lithium <0.001 ---- ---- ----mg/L0.0017439-93-2

<0.001Lutetium <0.001 ---- ---- ----mg/L0.0017439-94-3

<0.001Thorium <0.001 ---- ---- ----mg/L0.0017440-29-1

<0.001Cerium <0.001 ---- ---- ----mg/L0.0017440-45-1

0.009Manganese 0.003 ---- ---- ----mg/L0.0017439-96-5

<0.001Neodymium <0.001 ---- ---- ----mg/L0.0017440-00-8

<0.001Molybdenum 0.002 ---- ---- ----mg/L0.0017439-98-7

<0.001Praseodymium <0.001 ---- ---- ----mg/L0.0017440-10-0

<0.001Nickel <0.001 ---- ---- ----mg/L0.0017440-02-0

<0.001Samarium <0.001 ---- ---- ----mg/L0.0017440-19-9

0.002Lead 0.002 ---- ---- ----mg/L0.0017439-92-1

<0.001Terbium <0.001 ---- ---- ----mg/L0.0017440-27-9

<0.001Antimony <0.001 ---- ---- ----mg/L0.0017440-36-0

<0.001Thulium <0.001 ---- ---- ----mg/L0.0017440-30-4

<0.01Selenium <0.01 ---- ---- ----mg/L0.017782-49-2

<0.001Ytterbium <0.001 ---- ---- ----mg/L0.0017440-64-4

<0.001Tin 0.039 ---- ---- ----mg/L0.0017440-31-5

11 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results


tailings

B03

2018 bene combined

tailings

B02


(Matrix: WATER)





<0.001Yttrium <0.001 ---- ---- ----mg/L0.0017440-65-5

<0.001Thallium <0.001 ---- ---- ----mg/L0.0017440-28-0

<0.005Zirconium <0.005 ---- ---- ----mg/L0.0057440-67-7

<0.01Vanadium <0.01 ---- ---- ----mg/L0.017440-62-2

0.010Zinc 0.072 ---- ---- ----mg/L0.0057440-66-6

1.10Iron <0.05 ---- ---- ----mg/L0.057439-89-6


<0.0001Mercury <0.0001 ---- ---- ----mg/L0.00017439-97-6


<0.1Fluoride 3.8 ---- ---- ----mg/L0.116984-48-8

12 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

2018 bene combined

tailings

T04 - pH 9.0

2018 bene combined

tailings

T03 - pH 10.5

2018 bene combined

tailings

T02 - pH 12.0

2018 bene combined

tailings

T01 - pH 13.0

2018 bene combined

tailings

Client sample IDSub-Matrix: SOIL

(Matrix: SOIL)




EA002: pH 1:5 (Soils)

10.1 ---- ---- ---- ----pH Unit0.1----pH Value

EA009: Nett Acid Production Potential

-7.3 ---- ---- ---- ----kg H2SO4/t0.5----Net Acid Production Potential

EA010: Conductivity (1:5)

276 ---- ---- ---- ----µS/cm1----Electrical Conductivity @ 25°C

EA011: Net Acid Generation

8.9 ---- ---- ---- ----pH Unit0.1----pH (OX)

<0.1 ---- ---- ---- ----kg H2SO4/t0.1----NAG (pH 4.5)

<0.1 ---- ---- ---- ----kg H2SO4/t0.1----NAG (pH 7.0)

EA013: Acid Neutralising Capacity

7.3 ---- ---- ---- ----kg H2SO4

equiv./t

0.5----ANC as H2SO4

0.7 ---- ---- ---- ----% CaCO30.1----ANC as CaCO3

0 ---- ---- ---- ----Fizz Unit0----Fizz Rating

EA055: Moisture Content (Dried @ 105-110°C)

<1.0 ---- ---- ---- ----%1.0----Moisture Content

ED042T: Total Sulfur by LECO

<0.01 ---- ---- ---- ----%0.01----Sulfur - Total as S (LECO)

EG005(ED093)T: Total Metals by ICP-AES

3920Aluminium ---- ---- ---- ----mg/kg507429-90-5

<50Boron ---- ---- ---- ----mg/kg507440-42-8

43600Iron ---- ---- ---- ----mg/kg507439-89-6


7.8Arsenic ---- ---- ---- ----mg/kg0.17440-38-2

16Selenium ---- ---- ---- ----mg/kg17782-49-2

0.7Silver ---- ---- ---- ----mg/kg0.17440-22-4

1020Barium ---- ---- ---- ----mg/kg0.17440-39-3

0.8Thallium ---- ---- ---- ----mg/kg0.17440-28-0

3.4Beryllium ---- ---- ---- ----mg/kg0.17440-41-7

0.2Cadmium ---- ---- ---- ----mg/kg0.17440-43-9

0.3Bismuth ---- ---- ---- ----mg/kg0.17440-69-9

12.8Cobalt ---- ---- ---- ----mg/kg0.17440-48-4

13 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

2018 bene combined

tailings

T04 - pH 9.0

2018 bene combined

tailings

T03 - pH 10.5

2018 bene combined

tailings

T02 - pH 12.0

2018 bene combined

tailings

T01 - pH 13.0

2018 bene combined

tailings


(Matrix: SOIL)





58.5Chromium ---- ---- ---- ----mg/kg0.17440-47-3

25.0Copper ---- ---- ---- ----mg/kg0.17440-50-8

153Thorium ---- ---- ---- ----mg/kg0.17440-29-1

3210Manganese ---- ---- ---- ----mg/kg0.17439-96-5

58.1Strontium ---- ---- ---- ----mg/kg0.17440-24-6

4.7Molybdenum ---- ---- ---- ----mg/kg0.17439-98-7

33.4Nickel ---- ---- ---- ----mg/kg0.17440-02-0

255Lead ---- ---- ---- ----mg/kg0.17439-92-1

<0.1Antimony ---- ---- ---- ----mg/kg0.17440-36-0

8.4Uranium ---- ---- ---- ----mg/kg0.17440-61-1

86.6Zinc ---- ---- ---- ----mg/kg0.57440-66-6

17.7Lithium ---- ---- ---- ----mg/kg0.17439-93-2

20Vanadium ---- ---- ---- ----mg/kg17440-62-2

3.4Tin ---- ---- ---- ----mg/kg0.17440-31-5


<0.1Mercury ---- ---- ---- ----mg/kg0.17439-97-6

EN58-2: Leaching Environmental Assessment Framework (LEAF) Method 1313

---- 2.0 2.0 2.0 2.0mm0.1----Particle Size (>85 wt% passing through)

---- 4N HNO3 4N HNO3 4N HNO3 4N HNO3------Acid

---- <0.1 <0.1 <0.1 0.1mL0.1----Volume of acid

---- 1N NaOH 1N NaOH 1N NaOH 1N NaOH------Base

---- 70.0 4.0 <0.1 <0.1mL0.1----Volume of base

---- 330 396 400 400mL1----Volume of water

---- 48.0 48.0 48.0 48.0hours0.5----Extraction Contact Time

---- 22.4 22.4 22.4 22.4°C0.5----Ambient Temperature

---- 40.0 40.0 40.0 40.0g0.1----Mass of "as tested" solid

---- 13.0 12.0 10.5 9.0pH Unit0.1----Target pH

---- 22.4 22.4 21.9 23.1°C0.1----Ambient Temperature during extraction

14 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

2018 bene combined

tailings

T09 - pH 2.0

2018 bene combined

tailings

T08 - pH 4.0

2018 bene combined

tailings

T07 - pH 5.5

2018 bene combined

tailings

T06 - pH Neutral

2018 bene combined

tailings

T05 - pH 8.0


(Matrix: SOIL)





2.0 2.0 2.0 2.0 2.0mm0.1----Particle Size (>85 wt% passing through)

4N HNO3 4N HNO3 4N HNO3 4N HNO3 4N HNO3------Acid

0.2 0.5 0.6 0.9 3.0mL0.1----Volume of acid

1N NaOH 1N NaOH 1N NaOH 1N NaOH 1N NaOH------Base

<0.1 <0.1 <0.1 <0.1 <0.1mL0.1----Volume of base

400 400 399 399 397mL1----Volume of water

48.0 48.0 48.0 48.0 48.0hours0.5----Extraction Contact Time

22.4 22.4 22.4 22.4 22.4°C0.5----Ambient Temperature

40.0 40.0 40.0 40.0 40.0g0.1----Mass of "as tested" solid

8.0 7.0 5.5 4.0 2.0pH Unit0.1----Target pH

22.3 22.4 23.1 22.3 22.4°C0.1----Ambient Temperature during extraction

15 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

--------2018 bene combined

tailings

B03

2018 bene combined

tailings

B02

2018 bene combined

tailings

B01


(Matrix: SOIL)

--------26-Nov-2018 00:0026-Nov-2018 00:0026-Nov-2018 00:00Client sampling date / time

----------------ES1907149-013ES1907149-012ES1907149-011UnitLORCAS NumberCompound

Result Result Result ---- ----


2.0 2.0 2.0 ---- ----mm0.1----Particle Size (>85 wt% passing through)

4N HNO3 4N HNO3 4N HNO3 ---- ----------Acid

<0.1 3.0 <0.1 ---- ----mL0.1----Volume of acid

1N NaOH 1N NaOH 1N NaOH ---- ----------Base

<0.1 <0.1 70.0 ---- ----mL0.1----Volume of base

400 397 330 ---- ----mL1----Volume of water

48.0 48.0 48.0 ---- ----hours0.5----Extraction Contact Time

22.4 22.4 22.4 ---- ----°C0.5----Ambient Temperature

<0.1 <0.1 <0.1 ---- ----g0.1----Mass of "as tested" solid

Natural 2.0 13.0 ---- ----pH Unit0.1----Target pH

22.4 22.4 22.4 ---- ----°C0.1----Ambient Temperature during extraction

16 of 16:Page

Work Order :

:Client


3219134:Project

GHD PTY LTD

Analytical Results

----------------Hastings pilot plant

filtrate

Client sample IDSub-Matrix: WATER

(Matrix: WATER)

----------------26-Nov-2018 00:00Client sampling date / time


Result ---- ---- ---- ----


11.8 ---- ---- ---- ----pH Unit0.01----pH Value


5220 ---- ---- ---- ----µS/cm1----Electrical Conductivity @ 25°C


3390 ---- ---- ---- ----mg/L1----Total Dissolved Solids (Calc.)

EA025: Total Suspended Solids dried at 104 ± 2°C

16 ---- ---- ---- ----mg/L5----Suspended Solids (SS)


703Hydroxide Alkalinity as CaCO3 ---- ---- ---- ----mg/L1DMO-210-001

213Carbonate Alkalinity as CaCO3 ---- ---- ---- ----mg/L13812-32-6

<1Bicarbonate Alkalinity as CaCO3 ---- ---- ---- ----mg/L171-52-3

914 ---- ---- ---- ----mg/L1----Total Alkalinity as CaCO3


182Sulfate as SO4 - Turbidimetric ---- ---- ---- ----mg/L114808-79-8


285Chloride ---- ---- ---- ----mg/L116887-00-6


2.6Fluoride ---- ---- ---- ----mg/L0.116984-48-8

ANALYSIS REPORT: Created by Leigh Wills - ALS Sydney 2000

DATE COMPLETED:

SAMPLE TYPE:

No. of SAMPLES:

ISSUING LABORATORY: ALS BRISBANE

Address: 32 Shand Street 07 3243 7222

CONTACT: Sarah Gilmour

COMMENTS

EA046 : NATA accreditation does not cover performance of this service.

Signatory

07 3243 [email protected] E-mail:

Australian Laboratory Services Pty Ltd (ABN 84 009 936 029)

STAFFORD QLD 4053 Facsimile:

Acid Buffering Characteristic Curve (ABCC) REPORT

Batch: ES1907149

DATE RECEIVED:

26/01/2018Brisbane

8/03/2019ADDRESS:

LABORATORY:

DATE SAMPLED:CLIENT: GHD PTY LTD2 SALAMANCA SQUAREHOBART TAS, AUSTRALIA 7000

Telephone:

22/03/2019

1Soil

mailto:[email protected]

Work Order : ES1907149 Client ID:

Sub Matrix SoilClient Sample Identification 1Client Sample Identification 2Sample Date 26/01/2018

Method Analyte Units LOR1

ES1907149

EA046 - A Titration information

HCl Molarity: M 0.1Increments: mL 0.1

Weight (g) 2

ANC kgH2SO4/t 7.3

EA046 -B - Curve information

Addition

mLs added (total)

kg H2SO4/t pH Addition

mLs added (total)

kg H2SO4/t pH

0 0 0 8.44 36 3.6 8.82 3.081 0.1 0.245 7.86 37 3.7 9.065 3.052 0.2 0.49 7.46 38 3.8 9.31 3.033 0.3 0.735 7.23 39 3.9 9.555 3.004 0.4 0.98 7.08 40 4 9.8 2.975 0.5 1.225 6.94 41 4.1 10.045 2.956 0.6 1.47 6.78 42 4.2 10.29 2.937 0.7 1.715 6.58 43 4.3 10.535 2.918 0.8 1.96 6.36 44 4.4 10.78 2.899 0.9 2.205 6.15 45 4.5 11.025 2.8710 1 2.45 5.95 46 4.6 11.27 2.8511 1.1 2.695 5.66 47 4.7 11.515 2.8312 1.2 2.94 5.32 48 4.8 11.76 2.8113 1.3 3.185 5.00 49 4.9 12.005 2.8014 1.4 3.43 4.80 50 5 12.25 2.7915 1.5 3.675 4.64 51 5.1 12.495 2.7716 1.6 3.92 4.50 52 5.2 12.74 2.7617 1.7 4.165 4.33 53 5.3 12.985 2.7418 1.8 4.41 4.20 54 5.4 13.23 2.7319 1.9 4.655 4.08 55 5.5 13.475 2.7120 2 4.9 3.98 56 5.6 13.72 2.7021 2.1 5.145 3.89 57 5.7 13.965 2.6922 2.2 5.39 3.79 58 5.8 14.21 2.6723 2.3 5.635 3.70 59 5.9 14.455 2.6624 2.4 5.88 3.67 60 6 14.7 2.6525 2.5 6.125 3.59 61 6.1 14.945 2.6326 2.6 6.37 3.52 62 6.2 15.19 2.6227 2.7 6.615 3.46 63 6.3 15.435 2.6128 2.8 6.86 3.40 64 6.4 15.68 2.5929 2.9 7.105 3.35 65 6.5 15.925 2.5930 3 7.35 3.30 66 6.6 16.17 2.5731 3.1 7.595 3.26 67 6.7 16.415 2.5632 3.2 7.84 3.22 68 6.8 16.66 2.5533 3.3 8.085 3.18 69 6.9 16.905 2.5434 3.4 8.33 3.15 70 7 17.15 2.5335 3.5 8.575 3.11 71 7.1 17.395 2.52

GHD PTY LTD

2018 bene combined tailings



Method Analyte Units LOR1

ES1907149


HCl Molarity: M 0.1Increments: mL 0.1Weight (g) 2ANC kgH2SO4/t 7.3


Addition

mLs added (total)


mLs added (total)

kg H2SO4/t pH

72 7.2 17.64 2.5173 7.3 17.885 2.50

GHD PTY LTD




Method Analyte Units LOR1 Check

ES1907149




Addition

mLs added (total)


mLs added (total)

kg H2SO4/t pH

0 0 0 8.78 36 3.6 8.82 3.111 0.1 0.245 7.91 37 3.7 9.065 3.092 0.2 0.49 7.54 38 3.8 9.31 3.073 0.3 0.735 7.35 39 3.9 9.555 3.044 0.4 0.98 7.17 40 4 9.8 3.025 0.5 1.225 6.97 41 4.1 10.045 3.016 0.6 1.47 6.72 42 4.2 10.29 2.997 0.7 1.715 6.40 43 4.3 10.535 2.978 0.8 1.96 6.04 44 4.4 10.78 2.969 0.9 2.205 5.70 45 4.5 11.025 2.9410 1 2.45 5.40 46 4.6 11.27 2.9311 1.1 2.695 5.14 47 4.7 11.515 2.9112 1.2 2.94 4.88 48 4.8 11.76 2.9013 1.3 3.185 4.68 49 4.9 12.005 2.8914 1.4 3.43 4.50 50 5 12.25 2.8715 1.5 3.675 4.36 51 5.1 12.495 2.8616 1.6 3.92 4.23 52 5.2 12.74 2.8517 1.7 4.165 4.10 53 5.3 12.985 2.8418 1.8 4.41 3.99 54 5.4 13.23 2.8319 1.9 4.655 3.90 55 5.5 13.475 2.8220 2 4.9 3.82 56 5.6 13.72 2.8121 2.1 5.145 3.74 57 5.7 13.965 2.8022 2.2 5.39 3.67 58 5.8 14.21 2.7923 2.3 5.635 3.60 59 5.9 14.455 2.7824 2.4 5.88 3.54 60 6 14.7 2.7725 2.5 6.125 3.49 61 6.1 14.945 2.7526 2.6 6.37 3.45 62 6.2 15.19 2.7427 2.7 6.615 3.40 63 6.3 15.435 2.7428 2.8 6.86 3.36 64 6.4 15.68 2.7329 2.9 7.105 3.32 65 6.5 15.925 2.7230 3 7.35 3.28 66 6.6 16.17 2.7231 3.1 7.595 3.25 67 6.7 16.415 2.7132 3.2 7.84 3.22 68 6.8 16.66 2.7033 3.3 8.085 3.19 69 6.9 16.905 2.6934 3.4 8.33 3.16 70 7 17.15 2.6835 3.5 8.575 3.14 71 7.1 17.395 2.68

GHD PTY LTD




Method Analyte Units LOR1 Check

ES1907149




Addition

mLs added (total)


mLs added (total)

kg H2SO4/t pH

72 7.2 17.64 2.67 108 10.8 26.46 2.5073 7.3 17.885 2.66 109 10.9 26.705 2.5074 7.4 18.13 2.6675 7.5 18.375 2.6576 7.6 18.62 2.6477 7.7 18.865 2.6478 7.8 19.11 2.6379 7.9 19.355 2.6280 8 19.6 2.6281 8.1 19.845 2.6182 8.2 20.09 2.6183 8.3 20.335 2.6084 8.4 20.58 2.6085 8.5 20.825 2.5986 8.6 21.07 2.5987 8.7 21.315 2.5888 8.8 21.56 2.5789 8.9 21.805 2.5790 9 22.05 2.5791 9.1 22.295 2.5692 9.2 22.54 2.5693 9.3 22.785 2.5594 9.4 23.03 2.5595 9.5 23.275 2.5596 9.6 23.52 2.5497 9.7 23.765 2.5498 9.8 24.01 2.5399 9.9 24.255 2.53100 10 24.5 2.53101 10.1 24.745 2.52102 10.2 24.99 2.52103 10.3 25.235 2.51104 10.4 25.48 2.51105 10.5 25.725 2.51106 10.6 25.97 2.51107 10.7 26.215 2.50

GHD PTY LTD


0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.5

10.010.511.011.512.012.513.013.514.0

0 5 10 15 20 25 30

pH

kg H2SO4/t

ES1907149 - 1 and Check 1 (2018 bene combined tailings)Acid Buffering Characteristic Curve

pH/H2SO4/t

pH/H2SO4/t Duplicate

ANC value (H2SO4/t)

Titrating with 0.1M HCl, in increments of 0.1 mLs every 1000 seconds

ANALYSIS REPORT: Created by Leigh Wills - ALS Sydney 2000

DATE COMPLETED:

SAMPLE TYPE:

No. of SAMPLES:

Sarah Gilmour

COMMENTS

ADDRESS:

Signatory

07 3243 [email protected] E-mail:

Australian Laboratory Services Pty Ltd (ABN 84 009 936 029)

STAFFORD QLD 4053 Facsimile:

Kinetic Net Acid Generation (NAG) Report

Batch: ES1907149

DATE RECEIVED:

26/11/2018Brisbane

8/03/2019

LABORATORY:

DATE SAMPLED:CLIENT: GHD PTY LTD2 SALAMANCA SQUARE

CONTACT:

Telephone:

EA011K: This method is not NATA accredited

ISSUING LABORATORY: ALS BRISBANE

Address: 2 Byth Street 07 3243 7222

HOBART TAS, AUSTRALIA 7000 20/03/2019

1Soil

mailto:[email protected]


Sub Matrix Soil SoilClient Sample Identification 1 2018 bene combined tailings2018 bene combined tailings

Client Sample Identification 226/11/2018 26/11/2018

EA011-K: (A) Titration information

Time (mins) pH Temp pH Temp pH Temp

0 6.21 21.0 6.16 24.610 6.31 23.0 6.22 26.820 6.54 25.0 6.25 28.830 6.58 27.5 6.27 30.640 6.60 29.7 6.28 32.350 6.62 32.0 6.31 33.860 6.64 34.0 6.34 35.570 6.67 35.9 6.36 36.980 6.69 38.1 6.39 38.390 6.72 40.2 6.44 39.9100 6.76 42.5 6.51 41.4110 6.81 45.4 6.55 43.1120 6.87 49.2 6.59 45.3130 6.96 54.6 6.67 48.5140 7.12 63.1 6.76 52.8150 7.59 74.6 6.91 57.8160 8.42 69.8 7.24 72.2170 8.65 60.5 7.73 63.0180 8.70 54.0 8.50 57.5190 8.73 49.0 8.64 51.1200 8.75 45.0 8.70 46.4210 8.76 41.8 8.76 42.7220 8.78 39.3 8.80 39.6230 8.78 37.2 8.83 37.1240 8.79 35.3 8.85 35.3250 8.78 33.8 8.88 33.6260 8.75 32.6 8.92 32.1270 8.76 31.4 8.94 30.9280 8.75 30.3 8.96 30.0290 8.73 29.5 8.98 29.1300 8.73 28.9 9.00 28.4310 8.71 28.1 9.02 27.9320 8.71 27.6 9.04 27.3330 8.68 27.3 9.05 26.8340 8.67 26.8 9.07 26.5350 8.66 26.4 9.08 26.2360 8.65 26.2 9.08 26.2

Sample Date

GHD PTY LTD

ES19071491

ES19071491 Check

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.5

10.010.511.011.512.012.513.013.514.0

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360

Tem

per

atu

re (

Cel

siu

s)

pH

Time (minutes)

ES1907149 - 1 (2018 bene combined tailings)Kinetic NAG

pH

Temperature

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.5

10.010.511.011.512.012.513.013.514.0

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360

Tem

per

atu

re (

Cel

siu

s)

pH

Time (minutes)

ES1907149 - 1 Check (2018 bene combined tailings)Kinetic NAG

pH

Temperature

0 0.00 True

Environmental


:: LaboratoryClient GHD PTY LTD Environmental Division Sydney

: :ContactContact Sarah Gilmour Andrew Epps

:: AddressAddress LEVEL 15, 133 CASTLEREAGH STREET

SYDNEY NSW, AUSTRALIA 2000


:Telephone ---- :Telephone +61 7 3552 8639

:Project 3219134 Date Samples Received : 27-Mar-2019 14:00

:Order number Date Analysis Commenced : 28-Mar-2019

:C-O-C number ---- Issue Date : 18-Apr-2019 18:26

Sampler : ----

Site :

Quote number : EN/005/18





l General Comments






Ivan Taylor Analyst Sydney Inorganics, Smithfield, NSW

Raymond Commodore Instrument Chemist Sydney Inorganics, Smithfield, NSW

Titus Vimalasiri Metals Teamleader Radionuclides, Fyshwick, ACT


2 of 6:Page

Work Order :

:Client

ES1909328

3219134:Project

GHD PTY LTD

General Comments







purposes.







Key :

Gross Alpha and Beta Activity analyses are performed by ALS Fyshwick (NATA Accreditation number 992).l

LOR for gross alpha and beta in sample 4 raised due to the high amount of solid present.l

LOR for gross alpha and beta in sample raised due to the high amount of solid present.l

3 of 6:Page

Work Order :

:Client

ES1909328

3219134:Project

GHD PTY LTD

Analytical Results


tailings

ASLP PH 9

2018 bene combined

tailings

ASLP PH 5

Client sample IDSub-Matrix: ASLP LEACHATE

(Matrix: WATER)

------------26-Mar-2019 00:0026-Mar-2019 00:00Client sampling date / time



EA250: Gross Alpha and Beta Activity

0.96 <0.05 ---- ---- ----Bq/L0.05----Gross alpha

0.65 <0.10 ---- ---- ----Bq/L0.10----Gross beta activity - 40K

4 of 6:Page

Work Order :

:Client

ES1909328

3219134:Project

GHD PTY LTD

Analytical Results

----------------2018 bene combined

tailings

ALSP DI

Client sample IDSub-Matrix: DI WATER

(Matrix: WATER)



Result ---- ---- ---- ----


<0.05 ---- ---- ---- ----Bq/L0.05----Gross alpha

<0.10 ---- ---- ---- ----Bq/L0.10----Gross beta activity - 40K

5 of 6:Page

Work Order :

:Client

ES1909328

3219134:Project

GHD PTY LTD

Analytical Results

--------2018 bene combined

tailings

ASLP PH 9

2018 bene combined

tailings

ALSP DI

2018 bene combined

tailings

ASLP PH 5


(Matrix: SOIL)

--------26-Mar-2019 00:0026-Mar-2019 00:0026-Mar-2019 00:00Client sampling date / time

----------------ES1909328-004ES1909328-003ES1909328-001UnitLORCAS NumberCompound

Result Result Result ---- ----

EN60: ASLP Leaching Procedure

4.9 ---- 9.2 ---- ----pH Unit0.1----Extraction Fluid pH

5.0 ---- 9.5 ---- ----pH Unit0.1----Final pH

EN60: Bottle Leaching Procedure

---- 9.8 ---- ---- ----pH Unit0.1----Final pH

6 of 6:Page

Work Order :

:Client

ES1909328

3219134:Project

GHD PTY LTD

Analytical Results

----------------Hastings pilot plant

filtrate

Client sample IDSub-Matrix: WATER

(Matrix: WATER)



Result ---- ---- ---- ----


<0.05 ---- ---- ---- ----Bq/L0.05----Gross alpha

<0.10 ---- ---- ---- ----Bq/L0.10----Gross beta activity - 40K

Technical File Note

HASTINGS TECHNOLOGY METALS LIMITED DOCUMENT NO: YGB-20-000-ENG-PRO-TCN-0001_Rev01

Page 1 of 4

SUBJECT: Mo and F levels in Recycled Process Water testwork

DATE: 17/5/2019

DOCUMENT NO. & REV: YGB-20-000-ENG-PRO-TCN-0001 Rev 01

AUTHOR: N Marriott – Principal Engineer – Beneficiation

SUMMARY

A review of the recycled process water quality was undertaken after queries from DWER on the tailings

leach testwork. Specifically Molybdenum (Mo) and Fluorine (F) levels in the tailings leach test were initially

high and then declined rapidly with flushing. The question was asked whether repeated contact with fresh

ore would result in Mo and F concentrations significantly above those seen in the tailings leach testwork.

Locked cycle testwork has been carried out to assess the water quality and impact on metallurgical

performance of recycled process water chemistry. Mo and F were not measured initially, however some

results were able to be measured in the last 3 cycles of the locked cycle testwork (out of a total of 15

cycles). TDS levels were around 2600 to 3100 mg/L, with associated Mo and F assays at 2-2.5 mg/L and

4-5mg/L respectively.

BACKGROUND

This technical filenote discussed water quality from testwork intended to simulate process water recycle

within this Yangibana Beneficiation flowsheet.

This is an interim report associated with the testwork, specifically discussing the deportment of elements

Mo and F queried by DWER during the works approval process.

TEST DETAILSThe Yangibana beneficiation flowsheet is in open circuit, with the tailings from each of the flotation stages

reporting to final tailings. The locked cycle testwork was designed to look at the recycle of water within the

process. The initial plan was to complete 8 rougher only cycles to produce the process water that would

then be tested on the full rougher and 4-stage cleaner circuit. However additional cycles were added in

order to optimise the reagent dose rates with the new water chemistry. The ore sample used for this

testwork was the 2016 blended pilot plant feed (sourced from the Bald Hill and Fraser’s mineralisation).

A total of 15 cycles have been completed in the locked cycle testwork. Regardless of cycle performance

the water from each test was recovered by adding the coagulation reagent proposed in the full scale

operation – lime. The supernatant was then decanted. Additional water was recovered by collecting the

filtrate from pressure filtration, in order to maximise the amount of recycled water available for subsequent

tests.

Technical File Note


Page 2 of 4

Samples from each cycle were analysed for a limited suite of elements. F and Mo were added late in the

program to address the query from DWER.

RESULTS The results of water analysis from each cycle of testing are shown in Figure 1 below. This graph shows

the levels of Ca, Cl, Mg, Na, SiO2 and total dissolved solids (TDS) for the initial raw site water, as well as

water analysis at the end of each flotation test. TDS of the water rose rapidly from 1150mg/L in the raw

site water, up to a maximum of 3615 mg/L in the testwork. With Sodium (Na) being a major driver of TDS

levels. Sodium levels are being increased by the addition of sodium silicate and caustic soda (NaOH)

reagents in the process. Increased levels in the process water can be of assistance in the processing

circuit, acting as recycled reagents, reducing the amount of fresh caustic soda required by the process.

A more detailed analysis was complete on the final testwork sample from Test P, the results are shown in

Appendix A.

Figure 1 - Graph of recycled process water TDS and key dissolved element concentrations

Additional analyses of the water were undertaken after the levels of F and Mo in the tailings leach testwork

were questioned.

From the Tailings Characterisation Report (GCA Nov 2017) the observation was made that analysis of

TSF 1 and 2 slurry water indicates they are alkaline, brackish and likely to be enriched in fluorine (F) and

molybdenum (Mo) against the ANZECC Stock Quality Guideline (ANZECC, 2000). Pb was less than

Technical File Note


Page 3 of 4

detection-limit in the slurry water despite elevated levels of Pb in TSF 1 and 2 solids. Radionuclides

concentrations in the TSF 1 and 2 Slurry Waters were below 1Bq/g and not considered radioactive.

Further Leach testing detailed in in “180621 - Yangibana Tailings Leach Study Report - R0” June 2018,

has suggested that the enrichments of Mo and F are temporary artefacts of the process water. These

enrichments rapidly decline with flushing. This indicates that the Mo and F elevations were largely due to

'operational time-scales' and are not a long term feature of the tailings leachate.

The question was raised regarding what level of Mo and F would be seen on multiple contacts between

fresh ore and recycled process water during the operation. Figure 2 below shows the results from 3 cycles

of testing, at the end of the testwork program. TDS levels were around 2600 to 3100 mg/L, with associated

Mo and F assays at 2-2.5 mg/L and 4-5mg/L respectively.

Figure 2 – Molybdenum and Fluorine analysis of recycled process water from last 3 cycles of testing

Note that no fresh water was added to the locked cycle testwork, however the current water modeling for

site indicates that in steady state the process will operate on a mix of 80:20 recycled water to fresh raw

water, with some water lost to the hydromet circuit, evaporation, water losses in the concentrate dryer and

to the settled solids in the TSF.

The leach testwork leachate Mo levels were 1.072 to 1.154 mg/L for TSF 1 liquor and 1.953 mg/L for TSF

2 liquor.

The leach testwork leachate F levels were 7-11mg/L for the tailings leach testing.

Technical File Note


Page 4 of 4

APPENDIX A – DETAILLED WATER ANALYSIS (TEST P)


Appendix D – Seepage Analysis

Figure D-12-1 Seepage model arrangement

Figure D-12-2 Seepage model – Year 1




GHD | Report for Hastings Technology Metals Ltd - Yangibana TSF Design Development, 3219134 |




Appendix EStability Analysis

SLOPE STABILITY ANALYSIS

1) END OF CONSTRUCTION - UNDRAINED CONDITIONS - DOWNSTREAM

2) END OF CONSTRUCTION - DRAINED CONDITIONS - DOWNSTREAM

3) END OF CONSTRUCTION - DRAINED CONDITIONS WITH Ru = 0.5 - DOWNSTREAM

4) END OF CONSTRUCTION- UNDRAINED CONDITIONS - UPSTREAM

5) END OF CONSTRUCTION- DRAINED CONDITIONS - UPSTREAM

6) END OF CONSTRUCTION - DRAINED CONDITIONS WITH Ru -UPSTREAM

7) TAILING – UNDRAINED CONDITIONS

8) TAILING - DRAINED CONDITIONS


Appendix FConsequence Category Assessment

Client NameDam NameDam ID. No. (If existing dam) X X X XStream NameDam Height (Metres) Crest RLEstimated Capacity at FSL (Megalitres) 5,500Location

Yangibana Beneficiation TSF

N/A11m

Yangibana

Min

or

Med

ium

Maj

or

Cat

astr

ophi

c

TOTAL INFRASTRUCTURE COSTS (costs are indicative only)Residential <10M YES . . .Commercial <10M YES . . .Community Infrastructure <10M YES . . .Dam replacement or repair cost <10M YES . . .

IMPACT ON DAM OWNER'S BUSINESSImportance to the business Essential to maintain supply . . YES .Effect on services provided by the owner Severe restictions would be applied for at least 1 yr . . YES .Effect on continuing credibility Severe widespread reaction . YES . .Community reaction and political implications Severe widespread reaction . YES . .Impact on financial viability Significant with considerable impact in the long term . YES . .Value of water in storage (assessed by the owner in relation to the business)

Can be absored in one financial year YES . . .

HEALTH and SOCIAL IMPACTSPublic health <100 people affected YES . . .Loss of service to the community <100 people affected YES . . .Cost of emergency management <1,000 person days YES . . .Dislocation of people <100 person months YES . . .Dislocation of businesses <20 business months YES . . .Employment affected <100 jobs lost YES . . .Loss of heritage Local facility YES . . .Loss of recreational facility Local facility YES . . .

NATURAL ENVIRONMENTArea of Impact <5km2 . YES . .Duration of Impact <1 (wet) year YES . . .Stock and Fauna Discharge from dambreak would not contaminate water

supplies used by stock and fauna.YES . . .

Ecosystems Discharge from dambreak would have short term impacts on ecosystems with natural recovery expected after 1 wet season. Remediation possible.

. YES . .

Rare and endangered fauna and flora Species exist but minimal damage expected. Recovery within one year.

YES . . .

NATURAL ENVIRONMENT damage and loss severity level

HIGHEST DAMAGE AND LOSS SEVERITY LEVEL

Population at Risk (PAR) ≥1-10PAR includes all those persons who would be directly exposed to flood waters within the dam break affected zone if they took no action to evacuate.

CONSEQUENCE CATEGORY =

Completed and Reviewed ByDate

MAJOR

MINOR

339.0 m

HEALTH and SOCIAL IMPACTS damage and loss severity level

MINOR

CONSEQUENCE CATEGORY ASSESSMENTSunny Day Failure Scenario

26/03/2019

MEDIUM

MAJOR

Tom Ridgway / Ben Hanslow

Damage and Loss Estimate

Severity Level

Note 1: With a PAR in excess of 100, it is unlikely Damage will be minor. Similarly with a PAR in excess of 1,000 it is unlikely Damage will be classified as Medium.

Note 2: Change to 'High C' where there is the potential of one or more lives being lost. The potential for loss of life is determined by the charateristics of the flood area, particularly the depth and velocity of flow.

Reasons for recommending the consequence category (refer ANCOLD "Guidelines on the Consequence Categories for Dams", 2012) which MUST include comments on PAR, buildings, roads, other infrastructure and natural environment downstream of the dam and the potential impacts arising from a dambreak (NOTE: Provide photographs to support reasons):— The costs for the infrastructure and dam replacement and clean-up costs would be likely to exceed 10 million dollars but be less than 100 million dollars giving a medium level of damage to ANCOLD.— The impact of a sunny day failure failure on the dam owners business is ‘Major’ as the operation of the tailings dam is critical to the ongoing extraction and processing of the rare earth minerals and would lead to major economic impacts.— The impact of a dam failure on health and social impacts is minor due to the regional location of the dam.— The environmental impacts of a sunny day failure of the embankment is minor due to the benign nature of the material and low expected radiological impacts.— The environmental impacts of a flood loading failure scenario are considered to be moderate due to the benign nature of the material and the lack of expected long-term effects of the material within the surrounding environment.— Population at Risk (PAR) in flow path in case of failure would be limited to itinerants given no current permanent residences or mine facilities downstream. However, flooding could affect the site haul road. Arguably the PAR could be <1 but conservatively between 1 and 10.

HIGH C

TOTAL INFRASTRUCTURE COSTS severity level

IMPACT ON DAM OWNER'S BUSINESS damage and loss severity level

Client NameDam NameDam ID. No. (If existing dam) X X X XStream NameDam Height (Metres) Crest RLEstimated Capacity at FSL (Megalitres) 5,500Location

Yangibana Beneficiation TSF

N/A11 m

Yangibana

Min

or

Med

ium

Maj

or

Cat

astr

ophi

c


IMPACT ON DAM OWNER'S BUSINESSImportance to the business Restrictions needed during dry periods YES . . .Effect on services provided by the owner Minor difficulties in replacing services YES . . .Effect on continuing credibility Some reaction but short lived YES . . .Community reaction and political implications Some reaction but short lived YES . . .Impact on financial viability Able to absorb in 1 financial year YES . . .Value of water in storage (assessed by the owner in relation to the business)



NATURAL ENVIRONMENTArea of Impact <5km2 . YES . .Duration of Impact <1 (wet) year YES . . .Stock and Fauna Discharge from dambreak would not contaminate water

supplies used by stock and fauna.YES . . .

Ecosystems Discharge from dambreak is not expected to impact on ecosystems. Remediation possible.

YES . . .


YES . . .



Population at Risk (PAR) <1PAR includes all those persons who would be directly exposed to flood waters within the dam break affected zone if they took no action to evacuate.



CONSEQUENCE CATEGORY ASSESSMENTEnvironmental Spill Scenario

339.0 m


Severity Level

TOTAL INFRASTRUCTURE COSTS severity level MINOR

IMPACT ON DAM OWNER'S BUSINESS damage and loss severity level MINOR

HEALTH and SOCIAL IMPACTS damage and loss severity level MINOR

MEDIUM

MEDIUM

LOW



Reasons for recommending the consequence category (refer ANCOLD "Guidelines on the Consequence Categories for Dams", 2012) which MUST include comments on PAR, buildings, roads, other infrastructure and natural environment downstream of the dam and the potential impacts arising from a dambreak (NOTE: Provide photographs to support reasons):The Environmental Spill Consequence Category for the Beneficiation TSF has been assessed as Low, due to the benign nature of tailings, and low environmental risk due to lack of radionuclides and low metals concentration in the leachate.

Tom Ridgway / Ben Hanslow26/03/2019

Client Name YangibanaDam Name Hydromet TSFDam ID. No. (If existing dam) X X X XStream Name N/ADam Height (Metres) 9m Crest RLEstimated Capacity at FSL (Megalitres) 1,200Location Yangibana

Min

or

Med

ium

Maj

or

Cat

astr

ophi

c

TOTAL INFRASTRUCTURE COSTS (costs are indicative only)Residential $10M - $100M . YES . .Commercial <10M YES . . .Community Infrastructure <10M YES . . .Dam replacement or repair cost <10M YES . . .

IMPACT ON DAM OWNER'S BUSINESSImportance to the business Essential to maintain supply . . YES .Effect on services provided by the owner Severe restictions would be applied for at least 1 yr . . YES .Effect on continuing credibility Severe widespread reaction . YES . .Community reaction and political implications Severe widespread reaction . YES . .Impact on financial viability Able to absorb in 1 financial year YES . . .Value of water in storage (assessed by the owner in relation to the business)



NATURAL ENVIRONMENTArea of Impact <1km2 YES . . .Duration of Impact <1 (wet) year YES . . .Stock and Fauna

Discharge from dambreak would contaminate water supplies used by stock and fauna. Health impacts not expected.

. YES . .


. YES . .

Rare and endangered fauna and flora Species exist with losses expected to be recovered over a number of years.

. YES . .



Population at Risk (PAR) ≥1-10PAR includes all those persons who would be directly exposed to flood waters within the dam break affected zone if they took no action to evacuate.



MAJOR

MINOR

341.0 m

HEALTH and SOCIAL IMPACTS damage and loss severity level

MEDIUM

CONSEQUENCE CATEGORY ASSESSMENTSunny Day Failure Scenario

26/03/2019

MEDIUM

MAJOR

Tom Ridgway / Ben Hanslow


Severity Level



Reasons for recommending the consequence category (refer ANCOLD "Guidelines on the Consequence Categories for Dams", 2012) which MUST include comments on PAR, buildings, roads, other infrastructure and natural environment downstream of the dam and the potential impacts arising from a dambreak (NOTE: Provide photographs to support reasons):— The costs for infrastructure and dam replacement and repair costs are estimated to be below 10 million dollars giving a low level of impact to ANCOLD.— The impact of a sunny day failure on the dam owners business is ‘Major’ as the operation of the tailings dam is critical to the ongoing extraction and processing of the lithium.— The impact of a dam failure for sunny day loading on health and social impacts is minor due to the regional location of the dam.— The environmental impacts of a sunny day failure of the embankment is major.— The environmental impacts of a flood loading failure scenario are considered to be major due to the nature of the material and the lack of expected long-term effects of the material within the surrounding environment.— Population At Risk (PAR) in flow path in case of failure would be limited to itinerants given no current permanent residences or mine facilities downstream. However, flooding could affect the site haul road. Arguably the PAR could be <1 but conservatively between 1 and 10.

HIGH C

TOTAL INFRASTRUCTURE COSTS severity level

IMPACT ON DAM OWNER'S BUSINESS damage and loss severity level

Client Name YangibanaDam Name Hydromet TSFDam ID. No. (If existing dam) X X X XStream Name N/ADam Height (Metres) 9 m Crest RLEstimated Capacity at FSL (Megalitres) 1,200Location Yangibana

Min

or

Med

ium

Maj

or

Cat

astr

ophi

c


IMPACT ON DAM OWNER'S BUSINESSImportance to the business Restrictions needed during peak days and peak hour . YES . .Effect on services provided by the owner Minor difficulties in replacing services YES . . .Effect on continuing credibility Some reaction but short lived YES . . .Community reaction and political implications Some reaction but short lived YES . . .Impact on financial viability Able to absorb in 1 financial year YES . . .Value of water in storage (assessed by the owner in relation to the business)



NATURAL ENVIRONMENTArea of Impact <1km2 YES . . .Duration of Impact <1 (wet) year YES . . .Stock and Fauna

Discharge from dambreak would contaminate water supplies used by stock and fauna with contaminant uptake.

. YES .


. YES . .


YES . . .



Population at Risk (PAR) <1PAR includes all those persons who would be directly exposed to flood waters within the dam break affected zone if they took no action to evacuate.



CONSEQUENCE CATEGORY ASSESSMENTEnvironmental Spill Scenario

341.0 m


Severity Level

TOTAL INFRASTRUCTURE COSTS severity level MINOR

IMPACT ON DAM OWNER'S BUSINESS damage and loss severity level MEDIUM

HEALTH and SOCIAL IMPACTS damage and loss severity level MINOR

MAJOR

MAJOR

SIGNIFICANT



Reasons for recommending the consequence category (refer ANCOLD "Guidelines on the Consequence Categories for Dams", 2012) which MUST include comments on PAR, buildings, roads, other infrastructure and natural environment downstream of the dam and the potential impacts arising from a dambreak (NOTE: Provide photographs to support reasons):The Environmental Spill Consequence Category for the Hydromet TSF has been assessed as Significant due to the increased environmental risk resulting from a spill due to the increased concentration of Magnesium Sulphate and the concentration of radionuclides within the material.

Tom Ridgway / Ben Hanslow26/03/2019


Appendix G Environmental Benefits Summary Table

Environmental Risk Comparative Comments (FS Design vs Refined Design)

Site Location and Land Clearing

The disturbed footprint location remains unchanged for the refined concept design.

Slightly reduced clearing requirement associated with proposed refined design (See Figure 1). Any external borrow would likely be smaller for the refined design due to lesser clay/earthworks volumes associated with building the refined design.

Refined design embankments have the same or better setback to existing watercourses. (See Figure 2)

Dam Height and Failure Consequence Category (ANCOLD 2012)

RWP

RWP is eliminated from refined concept design (was Significant Consequence Category in FS design)

TSF1 (now combined with TSF2 as the Beneficiation TSF)

For the refined concept design, TSF1 perimeter embankment height is kept consistent with the FS design and ANCOLD Consequence Category is unchanged (Significant). Combining TSF1/2 does not increase the failure consequences.

TSF2

TSF2 is likely eliminated from preferred concept design (was Significant Consequence Category in FS design)

TSF3

The refined design for the Hydromet TSF that incorporates both TSF3 and Evaporation Pond has a reduced embankment height and similar or lesser consequences of failure/spill due to reduced height of tailings and ability to spill into Beneficiation TSF.

Evaporation Pond

For the refined concept design, the Evaporation Pond is eliminated (was Significant Consequence Category in FS Design)

Dam Spill Risk RWP/TSF1

In the FS design, the RWP was designed to contain run-off from TSF1 catchment and designed to hold a 1:100 AEP 72hr flood event prior to spill. For the refined concept, the RWP is not required and the decant pond within TSF1 has significant additional stormwater storage capacity (relative to FS RWP design) and hence overall significantly reduced risk of spill to the environment.

TSF2

In the FS design, TSF2 was designed to store a 1:100 AEP 72hr flood plus freeboard, but no emergency spillway provided (hence small risk of overtopping/failure if poorly managed or extreme flood occurs).

The refined concept combines Bene plant tailings into single stream and hence eliminates TSF2 from the design by combining with TSF1.

TSF3

In the FS design, TSF3 was designed to store a 1:100 AEP 72hr flood plus freeboard, but no emergency spillway provided. The refined concept allows the same flood storage on TSF3 but also includes an emergency spillway for containment of any spill within the capacity of Beneficiation TSF pond (i.e. no environmental release). The emergency spillway also eliminates the risk of overfilling and overtopping.

Evaporation Pond


The Evaporation Pond is eliminated from proposed refined concept (now combined with TSF3 and has emergency spillway into TSF1 decant pond)

Geotechnical Stability and Dam Failure Risk

RWP

The RWP dam failure risk is eliminated in refined concept.

TSF1

The refined concept design proposes conventional perimeter discharge. An Operations Manual will be developed requiring a central decant pond to be maintained with resulting low phreatic surface at perimeter embankment. This improves geotechnical stability and reduces piping risk (relative to CDF proposed in the FS design which relies on water ponding/drainage alongside the perimeter embankment).

TSF2

The feasibility study concept design proposes a 10 m high embankment with upstream clay zone and no filters. Ponding water against embankments means that piping is a plausible risk of dam failure/loss of containment.

The refined concept design eliminates TSF2 risk.

TSF3

The FS concept design proposes a 10 m high turkey’s nest embankment with a geocomposite lining system. The refined design proposes a similar high standard lining system, but better uses the natural topography resulting in significantly reduced tailings height and therefore overall lower risk of dam failure/loss of containment.

Seepage and Groundwater Risk

The overall TSF domain footprint is unchanged and situated on similar foundation conditions (i.e. similar for FS and refined concept). The geology comprises in-situ sandy clays overlying granite at shallow depth.

The refined design eliminates the need for the Return Water Pond which reduces risk posed by seepage impacting the watercourse at the toe of the dam (i.e. reduces risk of F and Mo concentrations in watercourse exceeding guidelines for stock drinking water).

Conventional perimeter discharge of thickened tailings allows small decant pond in Beneficiation TSF to be positioned centrally which minimises the risk of downstream seepage expression (relative to FS design). The development of wide desiccated beaches upstream of the Beneficiation TSF embankment mean that seepage risk is reduced in the proposed refined design.

TSF2 is eliminated in the proposed refined concept. Given the geochemistry similarities of TSF1 and TSF2 tailings, combining of the tailings is non-consequential and should reduce seepage due to eliminating a “wet” TSF for the proposed arrangement.

A high standard lining system is proposed for TSF3 in both the FS and refined concept design Hydromet TSF (i.e. same level of seepage mitigation is proposed).

Design maintains monitoring systems to allow early intervention prior to impact being caused.

Beach Slopes and Tailings Capacity/Beach Freeboard

The refined concept eliminates operational risk associated with Central Thickened Discharge (CTD) in TSF1. CTD can be very sensitive to thickener performance. Rather than rely on CTD, the proposed alternative arrangement for the Beneficiation TSF allows for perimeter tailings discharge via spigots. This removes the risks of flatter than expected beach slopes resulting in insufficient storage capacity during operations and potential overfilling of the TSF. Also, flattened beach slopes with CTD could result in significantly higher than expected


embankment heights and therefore greater geotechnical risk (relative to proposed refined design where embankment heights are more predictable due to less reliance on steep beach slope).

The refined concept uses perimeter beaching to control where the pond develops and ensures no pond on wall i.e. achieves central pond further set-back from watercourses and low Ksat tailings minimise seepage into foundation.

At closure a wide channel is excavated to ensure pond does not remain post closure. In the lead up closure, tailings discharge would adopt elements of CTD to maximise tails capacity and achieve suitable shedding surface with suitable network of drains. i.e. no change in philosophy.

Dust (including dust with elevated radiation levels)

Refined design combines TSF 3/Evaporation Pond into the Hydromet TSF. This reduces dusting risk in TSF3 that doesn’t rely on top-up water being pumped from a separate Evaporation Pond.

Flatter tailings beach slopes can be accommodated in the Beneficiation TSF using perimeter discharge method. This allows the combining of all Bene plant tailings streams for discharge into a combined TSF. Doing so further reduces the risk of dusting in the combined TSF1/2.

Surface Water Management

Refined design has less reliance on diversion of surface water run-off from TSF1. Overall the refined design has simplified water management which reduces risk of loss of containment.

See Figure 3 and 4

FS Design

The CTD option requires significant drainage to be excavated and managed around the full perimeter of the TSF. The actual location of the required diversion channel/s will depend on the beach slope achieved and the channel will need to be relocated and managed as the TSF beach expands. This will need to be carefully managed to ensure that the channel remains free draining. The unlined channel would also be an additional seepage source. It is also noted that water ponds on the upstream face of the perimeter embankment associated with the drainage path to the decant pond. The embankment design includes a relatively narrow clay zone and no filters – while piping risk is low, it still remains a plausible failure mode for the FS design.

Refined Design

The refined concept uses perimeter beaching to control where the pond develops and ensures no pond on wall (hence extremely low piping risk). 3 separate decant ponds are reduced to 1 single pond, hence eliminating risks of transferring water between ponds (pipe burst, channel blockage, erosion etc). Developing a well formed beach around the perimeter will require carefully management – but is well proven where mines manage responsibly. At closure a wide channel is excavated to ensure pond does not remain post closure. In the lead up to closure, tailings discharge would adopt elements of CTD to maximise tails capacity and achieve suitable shedding surface with suitable network of drains.

Closure Closure concepts, slopes and materials have not been altered.

Elimination of the standalone Evaporation Pond from the design arrangement reduces the rehabilitation liability associated with removing salt accumulation at closure which may be difficult to achieve in practice.

Pipe leakage / spills Risks are similar and manageable.

Figure 1 Comparative Disturbed Footprint

Figure 2 Comparative Embankments

Figure 3 Original Feasibility Study Design – Water Management Requirements

Figure 4 Refined Concept Design, Combined TSF with conventional perimeter discharge to form beaches and control pond location – no diversion channels required to contain TSF run-off


Appendix HExample Geosynthetic Liner Specification

The Client TSF xxx

Geosynthetic and Lining Specification

GHD | Report for The Client, TSF xxx, Geosynthetic and Lining Specification i

Table of contents 1. Introduction .................................................................................................................................... 1

1.1 General ................................................................................................................................ 1

1.2 Definitions ............................................................................................................................ 1

1.3 Lines of communication ....................................................................................................... 2

1.4 Materials .............................................................................................................................. 2

1.5 Sequencing and scheduling ................................................................................................. 2

1.6 Submittals ............................................................................................................................ 2

1.7 Construction quality control testing ...................................................................................... 4

1.8 Construction quality assurance ............................................................................................ 4

1.9 Work method statements ..................................................................................................... 5

1.10 Survey requirements ............................................................................................................ 6

1.11 Witness and hold points ....................................................................................................... 6

1.12 Works as Executed Drawings .............................................................................................. 7

2. PE geomembrane .......................................................................................................................... 8

2.1 General ................................................................................................................................ 8

2.2 Standards ............................................................................................................................. 8

2.3 Submittals ............................................................................................................................ 9

2.4 Manufacturer’s quality control ............................................................................................ 11

2.5 Manufacturer’s quality assurance ...................................................................................... 12

2.6 Material .............................................................................................................................. 12

2.7 Roll and sample identification ............................................................................................ 14

2.8 Delivery, storage and handling .......................................................................................... 14

2.9 Preparation of receiving surface ........................................................................................ 15

2.10 Installation .......................................................................................................................... 16

2.11 Weld trial ............................................................................................................................ 20

2.12 Trial seams ........................................................................................................................ 21

2.13 Field seam sampling and testing ....................................................................................... 21

2.14 Electrical leak location survey ............................................................................................ 24

2.15 Defects and repairs ............................................................................................................ 24

2.16 Acceptance ........................................................................................................................ 25

Pre-selection submittal form – geosynthetics .............................................................................. 28

Delivery submittal form – geosynthetics ...................................................................................... 30

Installation submittal form – geosynthetics .................................................................................. 32

Figure index Figure 1-1 Lines of communication ....................................................................................................... 2

GHD | Report for The Client, TSF xxx, Geosynthetic and Lining Specification ii

Table index Table 1-1 Independent sample size and frequency schedule ............................................................. 5

Table 1-2 Survey requirements ............................................................................................................ 6

Table 1-3 Witness and hold points ....................................................................................................... 7

Table 2-1 Acceptance criteria – PE geomembrane ........................................................................... 13

Table 2-2 Destructive seam testing requirements ............................................................................. 22

Table 2-3 Non-destructive seam testing requirements ...................................................................... 22

Table 2-4 Air pressure test schedule ................................................................................................. 23

Appendices Appendix A – Schedule of work method statements

Appendix B – Example submittal forms

GHD | Report for The Client, TSF xxx, Geosynthetic and Lining Specification 1

1. Introduction 1.1 General

This Specification contains the requirements for materials and procedures to be implemented

for the construction of TSF xxx Lining Works (the Works) at xxx (the site) and must be read in

conjunction with the other Contract Documents.

Where the Specification and any other Contract Documents do not agree, the Contractor shall

seek clarification from the Manager.

1.2 Definitions

The Definitions described in the Contract Documents apply to this document. The following

additional terms used in this Specification shall have the meanings ascribed to them below

unless the context otherwise requires:

‘Contract Drawings’ – The construction drawings which form part of the Contract Documents

‘Contract Documents’ – The documents which form the Contract

‘Contractor’ – A company or person with a formal contract to do a specific job – supplying labour

and/or materials and providing and overseeing staff as required

‘Contractor’s Independent Testing Firm’ – Independent testing firm(s) engaged by the

Contractor to conduct construction quality control (CQC) testing

‘Construction Quality Assurance (CQA) Engineer’ – Suitably qualified professional responsible

for administering the CQA requirements for the Works

‘Construction Quality Assurance (CQA) Engineer’s Independent Testing Firm’ – Independent

testing firm(s) engaged by the CQA Engineer to conduct construction quality assurance testing

‘Construction Quality Assurance (CQA) Plan’ – Plan forming part of the Contract Documents,

describing the construction quality assurance requirements for the Works

‘Field Crew Foreman’ – Foreman for the Geosynthetic Installer’s field crew, as defined by the

Contractor

‘Geosynthetic’ – Synthetic material (man-made plastic and fabric) used in geotechnical and

construction applications

‘Geosynthetic Installer’ – Firm subcontracted by the Contractor to complete the installation of

geosynthetic for the Works

‘Manager’ – The person who is managing the Contract on behalf of the Owner and who supplies

directions to the Contractor and to whom the Contractor refers in all matters.

‘MARV’ – Minimum average roll value – calculated as per GRI White Paper #10, The Dual

Roles for Using MARV (http://www.geosynthetic-institute.org/papers/paper10.pdf)

‘MaxARV’ – Maximum average roll value – calculated as per GRI White Paper #10, The Dual

Roles for Using MARV (http://www.geosynthetic-institute.org/papers/paper10.pdf)

‘Owner’ – xxx

‘PE’ – Polyethylene

‘Regulatory Authority’ – Authority responsible for licencing the Works


‘Seaming Crew’ – Crew responsible for the seaming activities performed by the Geosynthetic

Installer, as defined by the Contractor

‘Seaming Foreman’ – Foreman for the seaming activities performed by the Geosynthetic

Installer, as defined by the Contractor

‘Specification’ – This document

‘Work under the Contract' – The work which the Contractor is or may be required to execute

under the Contract and includes variations, remedial work, constructional plant and temporary

works

‘Works’ – The whole of the work to be executed in accordance with the Contract, including

variations provided for by the Contract, which by the Contract is to be handed over to the Owner

‘Works Area’ – As shown on the Contract Drawings.

1.3 Lines of communication

The lines of communication for the Works are illustrated in Figure 1-1. The Manager shall be the

main point of liaison between the Contractor and the CQA Engineer, as well as the Contractor

and the Owner.

Figure 1-1 Lines of communication

1.4 Materials

The Contractor shall be responsible for the sourcing, delivery, storage, preparation, handling

and installation of all materials, except as modified in individual sections of this Specification.

Material and installation specifications are included in the individual sections of this Specification

for each material type.

1.5 Sequencing and scheduling

The Contractor shall be responsible for sequencing the installation of all materials, including

surveys, testing and field trials.

In general, installation sequencing shall proceed from higher elevations to lower elevations to

prevent precipitation runoff from flowing into and/or below installed products.

Individual components shall not be covered with the subsequent component until the underlying

component has been accepted by the Manager.

1.6 Submittals

Submittals for each material are included in the individual chapters of this Specification.


The following pre-qualification submittals are required to be submitted by the Contractor at least

10 working days prior to construction for approval by the Manager.

1.6.1 Pre-qualification of the Geosynthetic Installer

Prior to construction, the Contractor shall provide a list documenting completed facilities for

which the Geosynthetic Installer has completed the installation of a geosynthetic lining system

similar to this Specification. For each facility, the following information shall be provided:

The name and purpose of the facility, its location, and the date of installation

The name of the owner, project manager, designer, manufacturer, and fabricator (if any)

If requested, the name and telephone number of a reference contact at the facility who can

discuss the project

The name and qualifications of the supervisor(s) of the installer’s crew(s)

The type(s) of seaming, patching, and tacking equipment

Any available information on the performance of the geosynthetic lining system at the

facility.

The Contractor shall also provide:

Certification indicating an approval or licence from the proposed geosynthetic

manufacturers for the Contractor to install the manufacturer’s materials

Certification that the Geosynthetic Installer’s Field Crew Foreman has a minimum of 200

hectares of actual geosynthetic installation experience and a minimum of 100 hectares of

supervisory experience for geosynthetic installation on a minimum of 10 different projects

Certification that the Geosynthetic Installer’s Seaming Foreman is an International

Association of Geosynthetic Installer’s Certified Welding Technician and has a minimum of

100 hectares of actual geosynthetic seaming experience and a minimum of 50 hectares of

supervisory experience during the seaming of geosynthetic materials

Certification that each individual on the Geosynthetic Installer’s Seaming Crew has a

minimum of 10 hectares of geosynthetic seaming experience and a minimum of 5 hectares

of seaming experience with geosynthetics similar to this Specification.

1.6.2 Pre-qualification of the Contractor’s Independent Testing Firm

Prior to construction, the Contractor shall provide a listing of qualifications for the proposed

Contractor’s Independent Testing Firms(s) and its key personnel who shall perform the work

described in this Specification. The Contractor’s Independent Testing Firms(s) shall be National

Association Testing Authorities (NATA) accredited and proof of accreditation shall be

maintained throughout the duration of the Works.

A listing of testing apparatus and testing standards typically performed by the testing firm shall

be provided along with a letter stating that the testing firm is independent and has no financial

interest in the Contractor, the Geosynthetic Installer or any of the manufacturers/suppliers that

are providing materials for the Works.

1.6.3 Works program

The Contractor shall prepare a program for the Works. The program shall encompass all

phases of the Works. The Contractor shall submit a draft of the program to the Manager for

review and approval at least 10 working days prior to construction. The Contractor shall not

undertake any works on the site until approval for such is given by the Manager. The program

shall include regular progress meetings with the Manager.


1.6.4 Procurement plan

Prior to construction, the Contractor shall provide a procurement plan which considers each

material to be supplied for the Works. For each material, the plan shall consider:

Material sources and relevant quantities from each source

Estimated timeframe for pre-qualification testing, provision of results and subsequent

approval to deliver to site

Estimated timeframe for delivery of material on-site

Estimated timeframe for independent conformance testing, provision of results and

subsequent approval for use (where required, refer Section 1.8.1).

The procurement plan shall align with the Works program, including installation timeframes.

1.6.5 Construction quality control plan

The Contractor shall prepare and implement a CQC Plan for the Works, and the plan shall

address all quality considerations identified or outlined in this Specification. The CQC plan shall

incorporate, as necessary, field testing, field verification, manufacturer’s certifications and

quality control testing at the manufacturing plant, to demonstrate that all Works comply with this

Specification. The CQC plan shall also demonstrate how construction will occur and the

methods by which the materials will be supplied, placed and tested to ensure compliance with

this Specification.

Works shall not commence until the CQC plan has been approved by the Manager.

The Owner may, at its discretion, audit the Contractor’s implementation of the CQC plan. The

Contractor shall co-operate with all such auditing.

1.7 Construction quality control testing

All construction quality control (CQC) testing shall be arranged by the Contractor and shall be

carried out by the Contractor’s Independent Testing Firm. The cost of CQC testing shall be

borne by the Contractor. Unless noted otherwise, copies of all test results shall be sent to the

Manager as soon as available but in any event within two days of becoming available. The

minimum testing frequencies shall be as nominated within this Specification.

At any stage throughout the Works, the Manager may arrange for independent testing and/or

surveying to be carried out. If that testing reveals that any works are found to be not compliant

with the requirements of this Specification and the Contract Drawings, the Contractor shall

undertake rectification of the non-compliant items and conduct re-testing in accordance with this

Specification. All costs of undertaking such rectification work and re-testing shall be borne by

the Contractor.

1.8 Construction quality assurance

A Construction Quality Assurance (CQA) Plan has been developed in conjunction with this

Specification and shall be implemented by the Owner to verify that the Works are undertaken in

a manner that meets the requirements of the Contract Documents.

The Owner shall engage an independent organisation (the CQA Engineer), under contract to

the Owner, who shall facilitate the requirements of the CQA Plan. This shall include

independent CQA monitoring, observation, testing and documentation on behalf of the Owner.

The Contractor shall cooperate fully with the Manager and all representatives of the CQA

Engineer during any independent CQA sampling, testing, and certification and shall ensure, at

all times, safe access to the Works for the purpose of monitoring, observation, and CQA


implementation. This shall include sampling of geosynthetic materials by the Geosynthetic

Installer under the supervision of the CQA Engineer.

1.8.1 Independent conformance testing

The CQA Engineer shall arrange for independent conformance testing of the materials used in

the Works, in accordance with the CQA Plan, to assure conformance with this Specification.

Samples shall be collected at locations designated by the CQA Engineer and all independent

conformance sampling shall be witnessed by the CQA Engineer. Where sampling of

geosynthetics is necessary, the sampling shall be undertaken by the Geosynthetic Installer from

the relevant materials for the independent conformance testing of the material. The Contractor

shall make a suitable allowance for this testing within their construction program.

The sample frequency shall be in accordance with Table 1-1. The table also identifies the

indicative sample size. The sample sizes shall be confirmed by the CQA Engineer prior to

construction. Sampling shall include the first and last roll. The specified frequency assumes all

rolls are from a single manufacturing run. If rolls are from different manufacturing runs then the

frequency shall be applied to each manufacturing run. The test frequency for all rolls where, in

the opinion of the CQA Engineer, the manufacturing run cannot be identified shall be every roll

for all test types. Samples shall not be taken from the outer wrap of the roll.

Table 1-1 Independent sample size and frequency schedule

Material Indicative size Frequency PE geomembrane 1 metre by roll width 1 per 5,000 m2

As a minimum, a period of 6 weeks shall be allowed for from the completion of on-site sampling

of all geosynthetic materials on-site to the receipt of independent conformance testing results

and subsequent approval/rejection of the materials for use. This shall be confirmed by the CQA

Engineer prior to construction.

If a sample records a non-conforming test result, it may be re-tested. If it passes this retest, both

results shall be provided in the laboratory report from the relevant independent testing firm. If

the retest produces a non-conforming test result, the Contractor shall remove and replace all

rolls between the sampled roll and the nearest conforming rolls either side (based on the

production order of the rolls). The Contractor may, by testing and verification of these

intermediate rolls, reduce the range of rolls to be removed in this way. Such additional testing

shall be for the full range of specified tests, not just the test or property which yielded a failure.

In the event of discrepancies between the CQA Engineer’s test results and the Contractor’s test

results, the Contractor shall be responsible for arranging a third independent testing firm to

verify the test results.

Any replacement material shall receive the independent conformance testing in accordance with

the CQA Plan.

1.9 Work method statements

Prior to the commencement of each type of work, the Contractor shall submit to the Manager

work method statements that detail how the work is to be carried out and the plant and

equipment proposed.

The Contractor shall submit such work method statements to the Manager at least 5 working

days prior to undertaking any work addressed by the work method statement.

The Manager may reject the submitted work method statement if, in the opinion of the Manager,

the statement does not comply with the Specification or any other Contract Documents provided

to the Contractor prior to or during construction.


Where a work method statement is rejected the Contractor shall revise and resubmit the

statement. No work addressed by the work method statement shall be undertaken by the

Contractor until the work method statement is approved by the Manager.

Acceptance by the Manager of a proposed work method statement in no way reduces the

Contractor’s liability to achieve the requirements described in this Specification.

Appendix A contains a schedule of activities for which the Contractor shall produce work

method statements.

1.10 Survey requirements

Prior to commencing construction, the Contractor shall establish a survey grid over the Works

footprint. The survey grid shall be a maximum 10 m spacing over the Works footprint, as well as

any locations at which there is a change or break in grade and set out points identified on the

Contract Drawings. The elevation of excavated surfaces and placed materials shall be recorded

at these grid locations.

Survey data shall be provided to the Manager in graphical and tabular formats. All survey shall

be to Mine Grid and levels shall be based on Australian Height Datum (AHD).

Table 1-2 contains a schedule of survey requirements for the Works.

Table 1-2 Survey requirements

Component Survey requirements

Prepared subgrade Upon completion of the prepared subgrade, survey the elevation at all grid locations and breaks in grade.

PE geomembrane Ongoing survey during installation of the PE geomembrane, survey the location of all panels, seams, patches, destructive tests, defects and repairs.

Seepage collection drain Following installation of the seepage collection drain, survey the levels and alignments of all pipework at maximum 10 m spacing and at any changes in grade.

Anchor trenches Upon backfilling of anchor trenches, survey the alignment and level of all anchor trenches.

1.11 Witness and hold points

The following information applies to witness and hold points for the Works:

A hold point is a defined position in the Works beyond which work shall not proceed without

mandatory verification and acceptance by the Manager

A witness point is a nominated position in the Works where the option of attendance may

be exercised by the Manager, after notification of the requirement

It shall be the Contractor’s responsibility to ensure that all obligations are fulfilled in regards

to the witness and hold points within the Contract

The Contractor shall give the Manager a minimum 2 days’ notice prior to the required

inspection

Where the witness or hold point relates to the condition of a surface or installed material,

the Contractor shall verify that the completed surface has achieved full conformance with

the Contract Documents

Witness or hold points may be released for part of the Works Area only, as defined by the

Manager, so that the Works can be completed in a sequenced manner. The Manager’s


approval of the completed items is required prior to the release of each witness or hold

point.

Table 1-3 contains a list of activities to which witness and hold points apply.

Table 1-3 Witness and hold points

Item Description Witness Hold 1 General 1.1 Provision of required pre-construction submittals, including

general work method statements, management plans and details of proposed testing firm(s)

1.2 Provision of work method statements and any associated design documentation (incl. panel layout drawings)

2 Subgrade preparation 2.1 Completion of subgrade preparation works (side slopes,

seepage collection trench and anchor trench)

2.2 Survey after completion of subgrade preparation works

3 Lining System

3.1 Completion of trial seams, approval of work method statement and detail for connection to existing geomembrane liner

3.2 Completion of installation of secondary geomembrane layer

3.3 Survey of completed primary geomembrane layer

3.4 Installation of pipework in seepage collection trench 3.5 Survey of pipework in seepage collection trench

3.6 Completion of installation of drainage 3.7 Backfilling of seepage collection trench 3.8 Survey after backfilling seepage collection trench 3.9 Completion of the installation of primary geomembrane layer 3.10 Survey of completed primary geomembrane layer

1.12 Works as Executed Drawings

The Contractor shall provide one (1) set of Works as Executed Drawings, which shall include all

corrections and as-constructed information done in a professional draftsman-like manner. All

Works as Executed Drawings shall be certified by a Registered Surveyor.

The following Works as Executed Drawings shall be prepared as a minimum:

Finished installed contours of the subgrade (determined prior to placement of the PE

geomembrane).

Finished installed alignments, levels and grades of the prepared seepage collection trench

and pipework.

Finished installed contours of the completed lining system including the anchor trench.

All Works as Executed Drawings shall include test locations, showing as a minimum the

approximate location, identification number, date sampled and type of testing completed.


2. PE geomembrane 2.1 General

This section contains the requirements for (PE) polyethylene geomembrane.

The Manager may reject any PE geomembrane that does not meet or exceed the requirements

of this section.

Any PE geomembrane rejected by the Manager shall be removed from the site and replaced at

the expense of the Contractor.

2.2 Standards

2.2.1 American Society for Testing and Materials Standards

Relevant American Society for Testing and Material (ASTM) standards are as follows:

D792 Standard Test Methods for Density and Specific Gravity (Relative Density) of Plastics

by Displacement

D1004 Standard Test Method for Initial Tear Resistance of Plastic Film and Sheeting

D1204 Standard Test Method for Linear Dimensional Changes of Non-rigid Thermoplastic

Sheeting or Film at Elevated Temperature

D1238 Standard Test Method for Flow Rates of Thermoplastics by Extrusion Plastometer

D1505 Standard Test Method for Density of Plastics by the Density Gradient Technique

D1603 Standard Test Method for Carbon Black in Olefin Plastics

D3895 Standard Test Method for Oxidative-Induction Time of Polyolefins by Differential

Scanning Colorimetry

D4218 Standard Test Method for Determination of Carbon Black Content in Polyethylene

Compounds by the Muffle-Furnace Technique

D4354 Standard Practice for Sampling of Geosynthetics and Rolled Erosion Control

Products(RECPs) for Testing

D4437 Standard Practice for Determining the Integrity of Field Seams Used in Joining

Flexible Polymeric Sheet Geomembranes

D4439 Standard Terminology for Geosynthetics

D4833 Standard Test Method for Index Puncture Resistance of Geotextiles,

Geomembranes, and Related Products

D4873 Standard Guide for Identification, Storage, and Handling of Geosynthetic Rolls and

Samples

D5199 Standard Test Method for Measuring the Nominal Thickness of Geosynthetics

D5397 Standard Test Method for Evaluation of Stress Crack Resistance of Polyolefin

Geomembranes Using Notched Constant Tensile Load Test

D5596 Standard Test Method for Microscopic Evaluation of the Dispersion of Carbon Black

in Polyolefin Geosynthetics

D5641 Standard Practice for Geomembrane Seam Evaluation by Vacuum Chamber

D5721 Standard Practice for Air-Oven Aging of Polyolefin Geomembranes


D5820 Standard Practice for Pressurized Air Channel Evaluation of Dual Seamed

Geomembranes

D5885 Standard Test Method for Oxidative Induction Time of Polyolefin Geosynthetics by

High Pressure Differential Scanning Colorimetry

D5994 Standard Test Method for Measuring the Core Thickness of Textured

Geomembranes

D6370 Standard Test Method for Rubber-Compositional Analysis by Thermogravimetry

(TGA)

D6392 Standard Test Method for Determining the Integrity of Non-Reinforced

Geomembrane Seams Produced Using Thermo-Fusion Methods

D6395 Standard Practice for Non-destructive testing of Geomembrane Seams using Spark

Test

D6693 Standard Test Method for Determining Tensile Properties of Non-Reinforced

Polyethylene and Non-Reinforced Flexible Polypropylene Geomembranes

D7238 Test Method for Effect of Exposure of Unreinforced Polyolefin Geomembrane Using

Fluorescent UV Condensation Apparatus

D7240 Leak Location using Geomembranes with an Insulating Layer in Intimate Contact

with a Conductive Layer via Electrical Capacitance Technique (Conductive Geomembrane

Spark Test)

D7466 Standard Test Method for Measuring Asperity Height of Textured Geomembranes

2.2.2 Geosynthetic Research Institute Standards

Relevant Geosynthetic Research Institute (GRI) standards are as follows:

GM9 Standard Practice for Cold Weather Seaming of Geomembranes

GM10 Specification for the Stress Crack Resistance of Geomembrane Sheet

GM13 Standard Specification for Test Methods, Test Properties, and Testing Frequency for

High Density Polyethylene (HDPE) Smooth and Textured Geomembranes

GM14 Standard Guide for Selecting Variable Intervals for Taking Geomembrane

Destructive Seam Samples Using the Method of Attributes

GM17 Standard Specification for Test Methods, Test Properties, and Testing Frequency for

Linear Low Density Polyethylene (LLDPE) Smooth and Textured Geomembranes

GM19 Standard Specification for Seam Strength and Related Properties of Thermally

Bonded Polyolefin Geomembranes

GM20 Standard Guide for Selecting Variable Intervals for Taking Geomembrane

Destructive Seam Samples Using Control Charts

GM29 Standard Practice for Field Integrity Evaluation of Geomembrane Seams (and

Sheet) Using Destructive and/or Non-destructive Testing

2.3 Submittals

2.3.1 Prior to selection of the polyethylene geomembrane manufacturer

The Contractor shall submit the following to the Manager for review and approval prior to

selection of a PE geomembrane manufacturer (per manufacturer and product):


Product manufacturer

Product name

Material data sheet showing the material properties of the proposed PE geomembrane

A list documenting no less than 40 completed facilities totalling a minimum of 200 hectares

for which the manufacturer has manufactured PE geomembrane similar to this

Specification. For each facility the following information shall be provided:

– Name and purpose of the facility

– The location and date of installation

– The name of the owner, the project manager, designer, fabricator (if any), and the

installer

– If requested, the name and telephone number of the contact at the facility who can

discuss the project

– The PE geomembrane type, thickness, and total square metres of the installation surface.

Documentation indicating that the polymer supplier has previously produced a minimum of

1,000 tonne of polymer of the same composition as that proposed for use in the

manufacture of the PE geomembrane for the Works

Manufacturer’s quality control and assurance procedures.

2.3.2 Prior to delivery of polyethylene geomembrane to site

The Contractor shall submit the following to the Manager for review and approval prior to

delivery of PE geomembrane to site (per PE geomembrane product):

Manufacturer’s certificate of compliance outlining conformance with the requirements of this

Specification

Manufacturer’s quality control and assurance test results

Certification that the PE geomembrane supplied for this work was manufactured as

consecutive rolls from a single lot or from consecutive lots. If the PE geomembrane is not

manufactured from consecutive lots, the resin manufacturer shall provide certification of

quality and consistency of the resin characteristics

Statement on the origin of the resin, its identification (type and lot number), resin supplier’s

name and production plant, resin brand name and type, and the maximum amount of

recycling polymer material added to the raw resin

Copies of quality control certificates issued by the resin supplier which shall include testing

conducted to verify conformance with Table 2-1

Certifications that the PE geomembrane and extrudate produced for the Works have the

same properties and are of the same resin

Complete description of the manufacturer’s shipping, handling and storage procedures

Manufacturer’s installation procedures and requirements

Work method statement for PE geomembrane delivery, storage, handling and installation.

This shall include seaming and jointing, welding, procedures for testing and repairing,

proposed handling equipment and restraining methods, and other information that shall

promote proper use


2.3.3 Prior to installation of polyethylene geomembrane

The Contractor shall submit the following to the Manager for review and approval prior to installation of the PE geomembrane:

Delivery, storage and handling log for all PE geomembrane rolls to be used in the Works,

including delivery dockets, roll number and identification, delivery inspection checklist,

details of storage and handling

Proposed panel placement drawing, showing the location and reference number of all

panels and expected seams, connections and penetrations, panel dimensions and layout,

and the order of panel installation

Survey of the underlying surface in accordance with Section 1.10

Results of independent material conformance testing as provided by the CQA Engineer.

2.3.4 Following installation of polyethylene geomembrane

The Contractor shall submit the following to the Manager for review and approval following

installation of the PE geomembrane:

Panel placement log, providing details on panel number and associated roll number, date

and time placed, condition of receiving surface, weather conditions and precipitation

events, QA checks performed, and all other relevant information

Trial weld log, recording all trial welds and testing undertaken

Field welding log providing details of all field welding undertaken, including:

– Weld type

– Weld ID number

– ID numbers of panels to be joined

– Name of welder

– Details of equipment used

– Ambient air temperature

– Geomembrane surface temperature

– Weld temperature

– Any problems or issues arising during welding.

Field sampling and testing results, including non-destructive and destructive tests

Results of electrical leak location survey as provided by the CQA Engineer (refer Section2.14)

Finalised panel placement drawing showing the as-built location of all panels, seams,

connections and penetrations

Defects and repairs log, showing details of all defects identified and repairs completed.

2.4 Manufacturer’s quality control

The manufacturer shall follow a quality control program, approved by the Manager, throughout the manufacturing of all PE geomembrane for the Works.

Manufacturer’s quality control submissions shall include:

Date of manufacture

Lot number, roll number, length and width


Manufacturer quality control documentation for the particular lot of resin used in the

production of the rolls delivered

Cross-referencing list delineating the corresponding resin used in the production of the rolls

delivered

Quality control program laboratory-certified reports

The manufacturer’s approved quality assurance stamp and the technician’s signature.

The frequency of sampling and testing shall be in accordance with Table 2-1.

The Manager may reject any PE geomembrane rolls that have not been sampled and/or tested

in accordance with this section.

All PE geomembrane rolls rejected by the Manager shall be removed from the site and replaced at the expense of the Contractor.

2.5 Manufacturer’s quality assurance

The manufacturer shall follow a quality assurance program, approved by the Manager, throughout the manufacturing of all PE geomembrane for the Works.

The frequency of sampling and testing shall be in accordance with ASTM D4354.

The Manager may reject any PE geomembrane rolls that have not been sampled and/or tested in accordance with this section.

All PE geomembrane rolls rejected by the Manager shall be removed from the site and replaced at the expense of the Contractor.

2.6 Material

The PE geomembrane shall:

Be manufactured of new, first-quality resin and shall be compounded and continuously

manufactured specifically for the Works. The resin manufacturer shall certify each batch for

the acceptance criteria listed in Table 2-1

Comply with the acceptance criteria specified in Table 2-1

Not contain more than 1 percent non-volatile pigment or fillers other than carbon black

Not be factory seamed.

The Contractor shall supply manufacturer’s quality control and assurance testing results in accordance with the testing frequencies identified in Table 2-1 showing that the proposed

material meets the requirements of this table. Samples taken shall be representative of the whole material source and shall be evenly distributed across the roll lots.

If required by the Manager, a sample of the PE geomembrane shall be provided (per product)

and the Manager and/or CQA Engineer may undertake an inspection of the manufacturer’s facility. The Contractor shall cooperate fully with the Manager and CQA Engineer to allow this inspection to occur.

PE Geomembrane shall be smooth surfaced. The primary geomembrane as shown on the Contract Drawings shall be 1.5 mm thick, ‘conductive’ geomembrane. The geomembrane shall have a coextruded, electrically conductive bottom layer such that a leak location survey may be

undertaken in accordance with the procedures outlined in ASTM D 7240.

The secondary geoemembrane as shown on the Contract Drawings shall be 1.5 mm thick ‘non-conductive’ geomembrane.


Table 2-1 Acceptance criteria – PE geomembrane

Property Test method Acceptance criteria Minimum testing frequency

Resin (1)

Density (min) ASTM D1505 or D792 (method

B) 0.932 g/cm3

per resin lot

Melt index (maximum) (2) ASTM D1238 1.0 g/10 min per resin lot

Sheet

Thickness (min. average) ASTM D5199 1.5 mm every roll

Thickness (min.) - Lowest individual of 10 readings

ASTM D5199

1.35 mm every roll

Density (min.) ASTM D1505 or D792 (method

B) 0.94 g/cm3 90,000 kg

Tensile properties (min. average) (3) - yield strength - break strength - yield elongation - break elongation

ASTM D6693

22 N/mm 40 N/mm

12% 700%

9,000 kg

2% modulus (max.) ASTM D5323 - per each formulation

Tear resistance (min. average) ASTM D1004 187 N 20,000 kg

Puncture resistance (min. average) ASTM D4833 480 N 20,000 kg

Stress crack resistance (4) ASTM D5397 600 hours per each formulation

Dimensional stability ASTM D1204 +2% 90,000 kg

Carbon black content (range) ASTM D4218 (5) 2 to 3%

9,000 kg (HDPE) or 20,000 kg (LLDPE)

Carbon black dispersion (category) (6) ASTM D5596 Cat 1 or 2 only 20,000 kg Oxidative induction time (OIT) (min. average) (7) - standard OIT AND - high pressure OIT

ASTM D3895

ASTM D5885

100 min

400 min

90,000 kg

1 Base resin density without carbon black or additives added

2 Conducted at 190°C with 2.16 kg mass applied

3 Machine direction (MD) and cross machine direction (XMD) average values should be on the basis of five test specimens each direction:

- HDPE yield elongation is calculated using a gage length of 33 mm

- HDPE break elongation is calculated using a gage length of 50 mm

- LLDPE break elongation is calculated using a gage length of 50 mm at 50 mm/min

4 The SP-NCTL test is not appropriate for testing geomembranes with textured or irregular rough surfaces. Test should be conducted on smooth edges of textured rolls or on smooth sheets made from the same formulation as being used for the textured sheet materials. The yield stress used to calculate the applied load for the SP-NCTL test should be the manufacturer’s mean value via MQC testing

5 Other methods such as ASTM D1603 (tube furnace) or ASTM D6370 (TGA) are acceptable if an appropriate correlation to ASTM D4218 (muffle furnace) can be established

6 Carbon black dispersion (only near spherical agglomerates) for 10 different views:

- 10 in categories 1 or 2 only, none in category 3

7 Samples to be evaluated at 30 and 60 days to compare with the 90 day response


Property Test method Acceptance criteria Minimum testing frequency

Oven aging at 85°C (min. average) - standard OIT AND - high pressure OIT

ASTM D5721

ASTM D3895

ASTM D5885

55% retained at 90 days

80% retained at 90

days

per each formulation

UV resistance (min. average) (8) - high pressure OIT (9)

ASTM D7238

ASTM D5885

50% retained after 1600 hours

per each formulation

2.7 Roll and sample identification

All PE geomembrane rolls and samples shall be identified in accordance with ASTM D4873.

Each roll or panel shall carry a label which identifies, as a minimum:

Product name, grade and name of manufacturer

Date of manufacture, batch number

Material thickness

Roll number

Roll length

Roll weight

Roll width

Handling guidelines

Reference numbers to raw material batch and laboratory certified reports

The manufacturer’s approved quality assurance stamp and the technician’s signature.

The Manager may reject any PE geomembrane rolls or samples that have not been identified in

accordance with this section.

All PE geomembrane rolls rejected by the Manager shall be removed from the site and replaced

at the expense of the Contractor.

2.8 Delivery, storage and handling

The Contractor shall prepare a work method statement for delivery, storage, handling and

installation of PE geomembrane, including repair methods (refer Appendix A). The work method

statement shall be submitted to the Manager for review and comment prior to delivery of the PE

geomembrane to site.

The delivery, storage and handling components of the work method statement shall be

developed in accordance with the guidance provided below:

Delivery, storage and handling of all PE geomembrane rolls and samples shall be

undertaken in accordance with the manufacturer’s instructions and ASTM D4873 as a

minimum

8 The condition of the test should be 20 hour UV cycle at 75oC followed by 4 hour condensation at 60oC

9 UV resistance is based on percent retained value regardless of the original high pressure OIT value


Rolls shall be delivered to site, handled and stored in such a manner that no damage

occurs to the rolls

Roll cores shall be sufficiently strong to ensure that they do not deflect by more than half

their diameter during delivery, storage and handling

Rolls shall be stored in a location away from construction traffic but sufficiently close to the

installation area to minimise handling. The storage area shall be level, dry, well-drained and

stable, and shall protect the product from precipitation, chemicals, excessive heat, UV

radiation, standing water, vandalism and animals

PE geomembrane roll stacks shall be limited to the height at which installation personnel

can safely manoeuvre the handling equipment. The recommended maximum stack height

is three rolls

Rolls shall be handled using a spreader stinger bar. The bar shall be capable of supporting

the full weight of the rolls without significant bending. Under no circumstances shall the rolls

be dragged, lifted from one end, lifted in the middle of the roll, lifted with the forks of a

forklift or pushed to the ground from the delivery vehicle. The Contractor may nominate

alternate handling equipment and plant for approval by the Manager as part of their work

method statement

The Contractor shall inspect all PE geomembrane rolls for defects and damage upon

delivery.

The Manager may reject any PE geomembrane rolls that have not been delivered, stored or

handled in accordance with this section.



2.9 Preparation of receiving surface

Prior to placement of PE geomembrane, the receiving surface shall exhibit the following

characteristics:

The surface shall be smooth, flat, firm and unyielding to the satisfaction of the Manager

The surface shall not exhibit visible deformation, rutting, yielding and/or show signs of

distress or instability during final proof rolling (if required)

The surface shall be free of debris, roots, angular material (such as sharp rocks),

desiccation cracks, abrupt breaks, indentations, sudden changes in grade, defects and/or

imperfections that may result in damage to the overlying materials

No loose, coarse-grained material shall remain on the surface. If required, the surface shall

be raked or graded to remove any material penetrating out of the surface greater than 10

mm

The surface shall promote drainage and excessive water shall not be allowed to pond on

the surface

The surface shall not be pebbly, tracked, rutted or otherwise disturbed by the equipment

deploying overlying materials or other traffic. Pockets, holes, or discontinuities shall be

repaired

All construction stakes, hubs, or other items used for grade control shall be removed and

any voids filled. Any unsuitable material shall be over-excavated to a depth of 100 mm and

replaced with approved material


The surface shall be maintained at sufficient moisture content to prevent desiccation during

the Works.

The receiving surface shall be surveyed as per the requirements of Section 1.10.

Placement of PE geomembrane shall not proceed until the receiving surface has been

inspected and approved by the Manager.

2.10 Installation

2.10.1 General


installation of PE geomembrane (refer Appendix A). The work method statement shall be

submitted to the Manager for review and comment prior to delivery of the PE geomembrane to

site.

The installation component of the work method statement shall be developed in accordance

with the guidance provided below.

The Manager may reject any PE geomembrane rolls that have not been installed in accordance

with this section.



2.10.2 Weather conditions

The Contractor shall consider the weather conditions on a daily basis to confirm they are

suitable for placement of PE geomembrane.

PE geomembrane shall not be placed or seamed:

If moisture prevents proper subgrade preparation, panel placement and/or panel seaming

During precipitation, during hail, during periods of excessive fog, during periods of

excessive dust, in standing water, on excessively wet surfaces, in the presence of excess

moisture (such as dew and/or ponded water)

During periods of excessive winds (>30 kph) or when gusting wind conditions interfere with

handling operations

When sheet temperatures are lower than 0° or higher than 65° as measured by a calibrated

infrared thermometer or surface thermocouple.

2.10.3 Traffic

Equipment used shall not damage the PE geomembrane by handling, trafficking, leakage of

hydrocarbons, or by other means.

No vehicle shall be allowed to travel directly on the PE geomembrane unless approved by the

Manager. Prior to approval, the Contractor shall provide the Manager the following information:

Guidance from the manufacturer on suitable plant for trafficking for the proposed PE

geomembrane and confirmation that the Contractor shall only use this plant

Guidance from the manufacturer on suitable trafficking method for the proposed PE

geomembrane and confirmation that the Contractor shall only use this trafficking method

Certification from the manufacturer that the above trafficking method and plant shall not

void the warranty for the proposed PE geomembrane.


2.10.4 Placement

PE geomembrane shall be placed in accordance with the following:

The PE geomembrane shall be placed and seamed in accordance with this Specification,

the Contract Drawings, the approved work method statement and the manufacturer's

instructions. Any contradictions shall be clarified with the Manager

Prior to placement, each roll shall be inspected by the Contractor for damage and/or

defects, including tears, abrasion, indentation, cracks, thin spots or any other faults or

defects. If damage or defects are identified, the roll shall be inspected by the Manager and

approved or rejected

PE geomembrane shall be protected from damage due to exposure to sunlight, dirt, dust

and other hazards

PE geomembrane shall be placed such that the panels are anchored at the crest of the

slope and form a continuous layer down the side walls and slopes and across the base

The arrangement of the PE geomembrane panels shall be in accordance with the approved

panel placement drawing and any changes approved by the Manager

Installation shall progress from the highest elevations to the lowest

PE geomembrane rolls shall be placed in an orderly fashion which shall minimise or

prevent surface water from flowing below previously installed PE geomembrane

PE geomembrane shall not be allowed to ‘bridge over’ voids or low areas. The PE

geomembrane shall be placed to allow intimate contact with the subgrade or underlying

geosynthetic

PE geomembrane shall be installed without undergoing excessive buckling, wrinkling or

tensioning

PE geomembrane shall not be dragged across an unprepared surface. If the PE

geomembrane is dragged across an unprepared surface, it shall be inspected for defects

and repaired or rejected if necessary

Where there is a geosynthetic layer below, the installation of the PE geomembrane shall be

undertaken in a manner so as not to damage the underlying layer

Sandbags or equivalent ballast shall be used as necessary to temporarily hold the PE

geomembrane in position and prevent uplift by wind. In case of high winds, continuous

loading shall be placed along edges of panels to minimise wind flow under the panels.

Sandbag material shall be sufficiently close-knit to prevent soil fines from working through

the bags and discharging on the PE geomembrane

Only those PE geomembrane rolls which can be seamed or permanently anchored on at

least two sides on the same day shall be placed on a daily basis. All other sides shall be

temporarily anchored

PE geomembrane installed on slopes shall be fixed in anchor trenches as shown on the

Contract Drawings and Section 2.10.5. PE geomembrane panels shall be anchored as

soon as possible. The Geosynthetic Installer shall program anchor trenches backfilling

when the temperature is coolest to minimise effects of material expansion


Personnel working on the PE geomembrane shall not smoke, wear damaging shoes,

excessively traffic or engage in other activities which may damage the PE geomembrane.

PE geomembrane in heavy traffic areas shall be protected by a geosynthetic overlay

PE geomembrane shall be cut from each roll with an approved hook blade knife with flat

zones on each end

PE geomembrane rolls shall be freely suspended during placement

The method used to unroll the PE geomembrane shall not cause bridging, excessive

wrinkles, scores, scratches and/or crimps

Folds and wrinkles caused by PE geomembrane panel placement or thermal expansion

shall be minimised

After placement, the PE geomembrane shall be free of excessive buckles, wrinkles, ripples,

creases, folds and irregular stressing before the overlying cover material or geosynthetic is

placed.

2.10.5 Anchoring of geosynthetics

Anchor trench excavation, backfill, and compaction shall be completed to the line and grades

shown on the Contract Drawings. A work method statement shall be prepared for the excavation

and backfill of anchor trenches during the Works with consideration to the guidance below.

Anchor trenches shall be prepared with slightly rounded corners where the geosynthetics enter

the trench so as to avoid sharp bends in the geosynthetic material. The base of the anchor

trench must be a smooth uniform surface that is free of defects and loose material.

The geosynthetic layers shall be placed in the trench as per the Contract Drawings to ensure

effective anchorage. Fill material shall be placed in maximum 100 mm loose lifts if compacted

with hand-operated compaction equipment, or maximum 200 mm loose lifts if compacted with a

self-propelled compactor.

The Contractor shall repair or replace any geosynthetics damaged as a result of placement or

compaction of backfill.

2.10.6 Seaming

PE geomembrane shall be seamed in accordance with the following guidance.

General

The PE geomembrane shall be field seamed into a continuous sheet across the Works by

using either dual hot wedge fusion welding or extrusion welding seams

Dual hot wedge fusion welding shall be the preferred method of welding and shall be used

for primary welds between adjacent PE geomembrane panels. Extrusion welding shall only

be used for detailed work, repair work, or in areas inaccessible for dual hot wedge fusion

welding (where approved by the Manager)

PE geomembrane placement shall be limited to that which can be seamed in one day

Trial seams shall be completed each day as per Section 2.11

All seams shall be ‘shingled’ down-slope to promote runoff (roof tile fashion)

All field seaming operations shall be supervised by the Seaming Foreman and no field

seams shall be made without the Seaming Foreman present

Prior to welding, the prepared weld surfaces shall be free of dust, dirt, debris, markings,

foreign material and any other potential contaminants that would inhibit welding. Where


contamination does occur, the prepared surfaces shall be thoroughly cleaned and the weld

completed

There shall be no free moisture in the weld area during welding. If free moisture is located

in the weld area, mitigation measures during seaming shall be employed as approved by

the Manager

The Geosynthetic Installer shall have an independently calibrated handheld temperature

measuring device to confirm the temperatures of each and every welding machine prior to

the commencement of any test or field welds. All information regarding the results gained

from the temperature device shall be recorded for each welding machine

Any electric generators used in welding shall be placed on a smooth base such that no

damage occurs to the underlying PE geomembrane

Adjacent to anchor trenches, seaming shall extend up the panels a minimum of 300 mm

past the crest of the anchor trench.

Weld locations

PE geomembrane panel placement shall take into consideration the site geometry including:

Field seams shall be orientated parallel to the line of maximum slope

For batters with a 10% grade or steeper, transverse (cross-slope) seams shall not be

permitted

No cross seams shall be allowed within 1,500 mm of the toe of any slope

In corners and odd shaped geometric locations, the number and total length of field seams

shall be minimised

Seams shall not be located at low points

All cross seams shall be offset at least 600 mm from the cross seam of the adjacent panel

and be extrusion or wedge welded where they intersect

All primary welds used to connect panel ends to sheets shall form T-joins (tees). These T-

connections shall have a distance of at least 500 mm. The welding seams of the PE

geomembrane cannot cross (no cruciform connections).

Dual hot wedge fusion welding

The dual hot wedge fusion welding shall be conducted using the split head wedge fusion

weld method, fusing the upper and lower overlapped PE geomembrane panels

The welding equipment shall be capable of continuously monitoring and controlling the

temperature in the zone of contact where the machine is actually fusing the PE

geomembrane so as to ensure that changes to environmental conditions shall not

adversely affect the integrity of the weld

Seams shall have a finished overlap of a minimum of 150 mm for dual hot wedge fusion

welding but in any event, sufficient overlap shall be provided to allow peel tests to be

performed on the seam

The dual hot wedge fusion welding shall form two contact fusion areas of a minimum width

of 15 mm and a 5 mm minimum wide void between each of the separate parallel weld

zones.


Extrusion welding

The extruder may be a combination sheet pre-heat and extruder type or a combination

dynamic mixing assembly and extruder type

The extrudate shall be manufactured from the same resin type used in the manufacture of

the relevant PE geomembrane being welded. All physical properties shall be identical to

those possessed by the raw PE geomembrane material. The Geosynthetic Installer shall

provide certification from the manufacturer that the relevant PE geomembrane and

extrudate produced for the Works have the same properties and are of the same resin for

each batch

During welding, the Geosynthetic Installer shall be responsible for regularly checking,

calibrating and recording of:

o Preheat air flow and temperature at the nozzle

o Extrudate flow and temperature at the barrel outlet

Seams shall have a finished overlap of a minimum of 75 mm for extrusion welding but in

any event, sufficient overlap shall be provided to allow peel tests to be performed on the

seam

The minimum width of the surface extruded bead shall be 30 mm

Prior to welding, oxidation by-products shall be removed from the weld area by grinding or

buffing. Grind marks shall not be deeper than 10% of the PE geomembrane thickness.

Seam grinding shall be been completed less than one hour before seam welding. The end

of welds more than five minutes old shall be ground to expose new material before

restarting a weld

Prior to welding, the extruder shall be purged until all the heat-degraded extrudate is

removed

Welding shall be undertaken in one direction only

A smooth insulating plate or fabric shall be placed beneath the hot welding apparatus after

use.

Pipe boots

Pipe boots may be constructed in the factory or in the field in accordance with the detail

shown on the Contract Drawings from relevant PE geomembrane conforming to this

Specification.

2.11 Weld trial

The Contractor shall trial the proposed connection detail of the existing PE Geomembrane to

the new PE Geomembrane as shown on the Contract Drawings. The weld trial shall be

undertaken at a minimum of two locations (one in each pond cell) as nominated by the

Manager.

The weld trial shall be verified in accordance with the general requirements outlined in Section

2.12 and Section 2.13 of this Specification. A minimum of three test locations shall be sampled

at each trial location.

Approval of the weld trial shall be on the basis of demonstrated conformance testing as required

by this Specification. If the requirements of this Specification and associated conformance

testing are not met, the Contractor shall repeat the weld trials in locations nominated by the

Manger, using an alternative methodology and/or weld detail if required. The weld trial shall be


re-tested and repeated until the requirements of this Specification are met. The weld trial shall

constitute a Hold Point.

2.12 Trial seams

The trial seams should be performed on the existing PE geomembrane prior to undertaking the

trial seams connecting the new and existing PE geomembrane. The effectiveness of the trial

seams shall be compared to the results of trials on the existing PE geomembrane to assess the

effectiveness of the weld trial.

Trial seams shall be performed on fragment pieces of PE geomembrane to verify that seaming

conditions are satisfactory and to supply test specimens for the CQA program.

Trial seams shall be conducted at the beginning of each seaming period and at least once each

four hours for each seaming apparatus used that day. Trial seams shall be repeated if any

welding stoppage exceeds one hour and if weather conditions change. Trial seams shall be

made under the identical conditions as the actual seams.

Each seamer shall make at least one trial seam each day for each seam method for each

seaming equipment apparatus to be used that day.

Trial seams shall be a minimum of 1,350 mm by 300 mm with seam centred.

The trial seam sample shall be cut into three subsamples (450 mm by 300 mm with seam

centred).

The two subsamples from each end shall immediately be tested onsite for peel and shear

strength in accordance with GM19.

If either specimen does not meet the acceptance criteria, the seamer and seaming apparatus

and/or methods shall not be accepted and shall not be used for seaming until the deficiencies

are corrected and two consecutive trial seams are successful.

The central portion of the trial seam sample shall be labelled and provided to the CQA Engineer

for destructive testing at the CQA Engineer’s Independent Testing Firm. A minimum one trial

seam sample per day shall be subjected to destructive testing. The Manager may reduce the

frequency of trial seam destructive testing at the CQA Engineer’s Independent Testing Firm, in

consultation with the CQA Engineer, if the field tensiometer appears adequate for assuring trial

seam quality.

If a trial seam sample records a non-conforming result for a test conducted at the CQA

Engineer’s Independent Testing Firm, a destructive test seam sample shall be taken by the

Contractor from the seams completed by the seamer during the shift related to the considered

trial seam. These samples shall be forwarded to the CQA Engineer’s Independent Testing Firm

by the Contractor and if they recording non-conforming test results, the length of seam

represented by the test sample shall be rejected.

The conditions of this section are considered as met for a given seam if a destructive seam test

sample has already been taken from the considered seam(s).

2.13 Field seam sampling and testing

2.13.1 General

Testing parameters, requirements and anticipated schedules shall be continuously reviewed by

the Contractor to ensure that adequate personnel and proper equipment shall be available.

Field seam sampling and testing shall be performed after seaming to verify that the mechanical

characteristics of the seams do not compromise the PE geomembrane integrity.


Test results shall be provided to the Manager in accordance with Section 1.7.

2.13.2 Destructive seam testing

Destructive seam samples shall be taken and tested in accordance with Table 2-2.

Repair patches shall be extrusion welded over the areas where destructive seam samples have

been taken and shall be subjected to non-destructive testing.

The location of each destructive seam sample shall be up to the discretion of the Manager and

CQA Engineer and designated on a copy of the panel placement drawing, along with the date

and time of sampling and the sample number.

Destructive test samples shall be a minimum of 1350 mm by 300 mm with seam centred.

The destructive seam sample shall be cut into 3 subsamples (450 mm by 300 mm with seam

centred).

The two subsamples from each end shall be taken and tested on-site for peel and shear

strength.

If both on-site subsamples meet the acceptance criteria of Table 2-2, the central portion of the

test sample shall be labelled and provided to the CQA Engineer for destructive testing at the

CQA Engineer’s Independent Testing Firm.

If either on-site or off-site test results do not meet the acceptance criteria listed in Table 2-2, the

length of seam represented by the test sample shall be rejected.

Table 2-2 Destructive seam testing requirements

Test description Test method Minimum test frequency (10)

Acceptance criteria (11)

Peel strength (12) ASTM D6392 1 test per 150 m (13) (or part thereof)

As per GM19

Shear strength ASTM D6392 1 test per 150 m (14) (or part thereof)

As per GM19

2.13.3 Non-destructive seam testing

All seams shall be non-destructively tested over the entire length of seam by at least one of the

methods in Table 2-3. The tests shall be undertaken no earlier than one hour after welding. In

addition to the above tests, the welds shall be visually inspected to assess the quality of the

workmanship and the appearance of the welded seam.

Table 2-3 Non-destructive seam testing requirements

Test description Test method Minimum test frequency

Acceptance criteria

Vacuum box ASTM D5641 No imperfections

10 A minimum of one series of destructive tests shall be performed each day that seaming is performed

11 All destructive test results shall be based on Film-Tear Bond (FTB) criteria. All samples which produce seam failures shall be considered unacceptable

12 Peel strength testing shall be performed on both Weld A and Weld B

13 When ambient air temperatures during seaming operations are less than 10oC, testing frequency shall be increased to one test per 75 linear meters

14 When ambient air temperatures during seaming operations are less than 10oC, testing frequency shall be increased to one test per 75 linear meters


Test description Test method Minimum test frequency

Acceptance criteria

Air pressure (15) ASTM D5820 All seams shall be tested by at least one of these three test methods as appropriate

Refer Table 2-4

Spark test ASTM D6365 No spark

Table 2-4 Air pressure test schedule

Geomembrane thickness

Minimum pressure Maximum pressure Maximum pressure differential (16)

1.5 mm 190 kPa 250 kPa 20 kPa

2.13.4 Pipe boot seam testing

All pipe boot seams shall be spark tested with acceptable pipe boots showing no spark.

Alternative testing methods may be allowed at the discretion of the Manager.

2.13.5 Non-conforming test results

If any test specimen does not meet the acceptance criteria listed, the test series shall be

considered unacceptable and all material or length of seam represented by the test series shall

be rejected. The Geosynthetic Installer may, at no additional compensation, take additional

samples for quality control testing in an attempt to minimise the amount of material represented

by the non-conforming test result.

In the event of discrepancies between the CQA Engineer’s test results and the Contractor’s test

results, the Contractor shall be responsible for arranging a third independent testing firm to

verify test results.

An acceptable length of seam shall be defined as a length of seam which lies between

conforming destructive test locations and has passed non-destructive seam testing.

2.13.6 Field testing summary

The Geosynthetic Installer shall prepare a field testing summary for all installed PE

geomembrane. For each PE geomembrane layer, a separate copy of the panel placement

drawing shall be utilised for this summary and shall indicate the PE geomembrane layer

represented. On each sheet, the following information shall be recorded:

The location, date, sample number and test result (conforming/non-conforming) of each

destructive test series

The location, identification number and date of each non-destructive air pressure seam test

including the length of the tested seam and the result of the test (conforming/non-

conforming)

The location, date and lengths of non-destructive vacuum box testing performed on a daily

basis and the result of the tests (conforming/non-conforming)

The location, identification number and date of each non-destructive spark test including

the length of the tested seam and the result of the test (conforming/non-conforming).

15 All hypodermic needle punctures shall be repaired as per the requirements of this Specification

16 Observe and record the pressure 5 min after the initial reading. If the loss of pressure exceeds that shown, or if the pressure does not stabilize, the faulty area should be located and repaired


2.14 Electrical leak location survey

2.14.1 General

Following the installation of each PE geomembrane layer, the Leak Location Contractor

engaged by the Manager shall conduct an electrical leak location survey to detect leaks in the

PE geomembrane.

2.14.2 Preparation and support

The Contractor shall responsible for preparing the survey area for the leak location survey.

The Contractor shall be responsible for completing installation work around the edge of each PE

geomembrane layer that provides electrical isolation of the PE geomembrane for the electrical

leak location surveys. The Manager may provide further details on this procedure if requested.

The Contractor shall ensure the PE geomembrane surface is clean and dry prior to the survey.

2.14.3 Repairs

The Geosynthetic Installer shall be responsible for repairing any leaks found. Repairs shall be

undertaken in accordance with Section 2.15.

After the leak is repaired, the Leak Location Contractor shall retest the area to ensure the leak

was repaired and that there are no other leaks in the vicinity of the repair.

2.15 Defects and repairs

The Contractor and shall be responsible for inspecting the placed PE geomembrane to identify

any damage or faults in the material. The Manager and/or CQA Engineer may also undertake

inspections of the placed PE geomembrane to identify any damage or faults in the material. Any

areas of PE geomembrane damaged during installation shall be repaired by the Contractor. All

repairs shall be verified by the Manager.


installation of PE geomembrane (refer Appendix A). The work method statement shall be

submitted to the Manager for review and comment prior to delivery of the geomembrane to site.

The installation component of the work method statement shall include work methods for

defects and repairs, developed in accordance with the guidance provided below:

All repairs shall be undertaken in accordance shall be undertaken in accordance with this

Specification, the approved work method statement and the manufacturer's instructions.

Any contradictions shall be clarified with the Client’s Representative. All repairs shall be

verified by the Client’s Representative

Patches and cap strips shall have rounded edges (minimum radius of 75 mm), shall be

made of the same geomembrane and shall extend a minimum of 150 mm beyond the edge

of defects. All patches shall be of the same compound and thickness as the PE

geomembrane being patched over. Patches shall be seamed using extrusion (fusion)

welding

Punctures, pin holes, blisters, small tears and localised imperfections shall be repaired

using a patch

Large tears and lengths of seam shall be repaired using a cap strip. No reseaming over

existing seams shall be permitted

Tears which lie on slopes greater than 5% or which lie in areas of stress and have sharp

ends shall have all sharp ends rounded prior to repair


The PE geomembrane below large patches and cap strips shall be cut as necessary to

prevent moisture or gas collection between sheets

Excessive wrinkles which exist at the end of seaming operations and which may become

creased during backfilling shall be cut and reseamed. Excessive wrinkles shall be defined

as a wrinkle which at the time of covering and in the opinion of the Manager, meets any of

the following criteria:

– Is nominally >200 mm in height

– May fold during backfilling

– May adversely impede the flow along the surface of the geomembrane

‘Fishmouths’ or wrinkles at the seam overlaps shall be cut along the ridge of the wrinkle in

order to achieve a flat overlap. The cut ‘fishmouths’ or wrinkles shall be seamed and any

portion where the overlap is inadequate shall then be patched with an oval or round patch

of the same geomembrane extending a minimum of 150 mm beyond the cut in all

directions. All corners of the patch shall be rounded with a 25 mm minimum radius

All repair seams shall be made in accordance with the requirements of Section 2.10.6

Each repair shall be required to pass non-destructive tests (refer Section 2.13.3). Large cap

strips may require destructive testing (refer Section 2.13.2), as directed by the Manager.

The Contractor shall submit to the Manager for review a log containing details of any defects

identified and repairs carried out.

2.16 Acceptance

The Contractor shall retain all ownership and responsibility for all PE geomembrane until final

acceptance of all work under this Contract by the Owner.

PE geomembrane shall be accepted by the Owner when all of the following conditions are met:

Required submittals are provided by the Contractor to the Manager and approved

Adequacy of all field seams, penetrations and repairs is verified by the Manager

The electrical leak location survey has been completed and all required repairs have been

completed by the Contractor

Details of all defects identified and repairs performed have been provided by the Contractor

to the Manager and approved

The CQA Engineer has provided the Manager with a recommendation that the conditions of

final acceptance have been met

The Manager has inspected and approved the finished surface/s.

GHD | Report for The Client Geosynthetic and Lining Specification[Title] 26

Appendices


Appendix A – Schedule of work method statements

Work Method Statements (non-exhaustive list)

Connection to existing liner

Construction of seepage collection trench

Excavation and backfill of anchor trenches

Geotextile installation and testing

Polyethylene geomembrane installation and testing


Appendix B – Example submittal forms

Pre-selection submittal form – geosynthetics

Submission data

Project name and location:

Submittal number:

Material designation (as per the Specification):

Reference section of Specification:

Product manufacturer:

Product name:

Proposed placement location:

Estimated quantity:

Material sample provided: □ Yes

□ No (provide reason below)

□ N/A (provide reason below)

Additional comments (including other information provided as required):


Attachments

Material data sheet:

□ Yes



Manufacturer’s quality control and assurance

procedures:

□ Yes




Submitted by:

(include title and signature)

Date:


Delivery submittal form – geosynthetics

Submission data


Submittal number:




Product name:


Estimated quantity:






Attachments

Manufacturer’s certificate of compliance:

□ Yes



Manufacturer’s quality control and assurance

test results/reports:

□ Yes



Manufacturer’s shipping, handling and

storage procedures:

□ Yes



Manufacturer’s installation procedures and

requirements:

□ Yes



Work method statement for material delivery,

storage, handling and installation:

□ Yes




Submitted by:


Date:


Installation submittal form – geosynthetics

Submission data


Submittal number:




Product name:


Estimated quantity:




Material inspected by CQA Engineer: □ Yes





Attachments

Delivery, storage and handling log (including

roll numbers):

□ Yes



Proposed panel placement drawing: □ Yes



Survey of underlying surface: □ Yes



Independent conformance test results/reports

(provided by CQA Engineer)

□ Yes




Submitted by:


Date:


Appendix I – Ammonia Gas Modelling Reports

15 April 2019

To Darren Tull (Hastings Rare Earth Minerals)

Copy to Ben Hanslow

From Matthew Brannock Tel +61 7 3316 3907

Subject Yangibana TSF Ammonia Evolution Modelling Job no. 321913401

1 Appreciation of Issue

It is understood that “Hastings Technology Metals Ltd”, henceforth named “Hastings”, is enquiring about the magnitude of ammonia gas evolving from a Yangibana Tailings Storage Facility (TSF). The Hydromet TSF, under a worst case scenario, receives a stream at 76 t/h containing approximately 0.04 g/L of ammonium bicarbonate and 6.28 g/L of ammonium hydroxide solution. The quantity of ammonia evolution from the Hydromet TSF will be compared to that released from the plant into the TSF. This information will help to inform Hastings of potential health and safety risks to workers resulting from ammonia evolution, as well as the potential environmental implications as a result of the release of ammonia.

2 Methodology

To model the ammonia off-gas evolution from the Hydromet TSF, the software packages OLI Stream Analyzer and AqMB Designer were utilised. Both employ speciation chemistry modelling for the equilibrium analysis of complex aqueous systems, such as a multi-component TSF. AqMB Designer is more process design oriented (e.g. sizing of gas stripping equipment and other industrial water treatment units) whilst OLI Stream Analyzer is more chemistry oriented (i.e. it has a very sophisticated equation of state model however it cannot design or size process equipment). The preliminary AqMB results (i.e. modelling / sizing of a gas stripper – not reported here) corroborated with OLI Stream Analyzer results (i.e. a simplified representation of a TSF). The results presented cover the OLI Stream Analyzer modelling of the TSF system.

The composition data supplied by Hastings (representing a worst case scenario) is as follows.

Component Concentration (g/L)

H2O (l) 975.03

CaSO4 (aq) 1.98

K2SO4 (aq) 0.22

MgCl2 (aq) 0.23

MnSO4 (aq) 1.06

Na2SiO3 (aq) 0.03

Na2SO4 (aq) 8.39

NaCl (aq) 0.41

NH4HCO3 (aq) 0.04

C17H35CO2Na (o) 1.38

Mg 0.06

NH4OH (aq) 6.28

As the OLI Studio database did not include the surfactant, “C17H35CO2Na (o)”, the inter-species interaction of the component was modelled via NaC2H5O2 and C17H36. The former simulated the carboxy-sodium functional group, and the latter simulated the surfactant carbon chain.

In addition, elemental Mg was combined with MgCl2 to simulate a more likely oxidation state in the pond. The resulting addenda to the above information is as follows.

Component Concentration (g/L)

NaC2H5O2 0.37

C17H36 1.08

MgCl2 0.47

In order to model an approximate range of evolution conditions for ammonia off-gas, the temperature of the TSF was assumed to range from a low of 25°C to a high of 35°C (a typical range for TSFs at similar locations around Australia). The impacts of ‘fresh’ tailings entering the pond at ~52°C was ignored, as the system was assumed to be at equilibrium with the ambient air. Evaporation and rainfall has also been ignored (although it is expected that net evaporation will be positive).

Accordingly, the composition of air at both 25°C and 35°C was determined at 100% relative humidity and 1 atm of pressure. Within OLI Studio, the TSF and the surrounding air are modelled as separate streams that are then “mixed”. In order to model the impact of different ammonia partial pressures in the atmosphere surrounding the Hydromet TSF, the air “stream” was set to 10 and 20 times the volume of the incoming tailings respectively. This

also captures some of the variability in ammonia evolution resulting from different atmospheric conditions, such as increased mixing with air due to wind.

The table below summarises all investigated scenarios under varying conditions.

Air:Liquid Ratio

Solids Formation?

pH Mix Temp (°C)

10 Yes 7.0 25

10 Yes 7.0 35

10 Yes 13.0 25

10 No 10.3 25

10 Yes 10.3 25

10 Yes 9.99 35

20 Yes 7.0 25

20 Yes 7.0 35

20 Yes 13.0 25

20 No 10.3 25

20 Yes 10.3 25

20 Yes 9.99 35

These scenarios cover the impacts of:

Rough variation of partial pressure of ammonia in the atmosphere above the TSF (following ammonia off-gassing) via modification of the air to liquid ratio;

Solids precipitation and interspecies interactions within solution; pH of the TSF on ammonia off-gas evolution; Variation in ambient air temperature.

With regards to solids formation, it was assumed that the precipitation of minerals such as dolomite, quartz, and chrysotile will not occur due to the timescales required for formation. As OLI Stream Analyzer assumes an equilibrium state and is not a dynamic model, minerals such as these were excluded from the model if they were predicted.

Note that reaction kinetics were ignored as this will not affect the magnitude of the ammonia off-gassing rate while the Hydromet TSF consistently receives inflow.

3 Results

The results of the scenarios discussed above are as follows based on a ~76 t/h pond inflow worst case composition:

Pre-TSF Storage Scenarios Resulting Mass of TSF Feed N(-3)* Lost to Atmosphere

Air:Liquid Ratio

Solids Formation? pH Mix Temp (°C) (% Mass of TSF Feed)

(kg/day as NH3)

10 Yes 7.0 25 0.6 % 33

10 Yes 7.0 35 1.0 % 56

10 Yes 13.0 25 88 % 5,000

10 No 10.3 25 68 % 3,855

10 Yes 10.3 25 70 % 4,018

10 Yes 9.99 35 74 % 4,203

20 Yes 7.0 25 0.7 % 39

20 Yes 7.0 35 1.2 % 67

20 Yes 13.0 25 93 % 5,297

20 No 10.3 25 73 % 4,167

20 Yes 10.3 25 77 % 4,424

20 Yes 9.99 35 79 % 4,503

*Note that this value is the total of ammonia and ammonium, N2 from air is not included.

It is evident that at elevated pHs the predominant form of ammonia/ammonium (i.e. N(-3) oxidation state of nitrogen) is dissolved ammonia gas (rather than the ammonium ion) which has a propensity to off-gas due to low concentrations of ammonia in the atmosphere. Generally, over 98 % by mass of ammonia evolves as off-gas with the small remainder dissolved in the tailings pond. Therefore to reduce ammonia evolution, conditions within the TSF must favour ammonium formation.

It is also evident that higher temperatures result in greater off-gas production. As the ‘fresh’ tailings are at ~52 °C there is the potential for greater additional ammonia evolution than these results suggest.

When the tailings are neutralised, ~1% of the combined ammonia/ammonium sent to the Hydromet TSF by mass, escapes as ammonia off-gas. However, this would require approximately 16.4 t/d of sulphuric acid based on an influent pH of ~10, an inflow of ~78 m3/h (at 76 t/h), and an influent composition as described previously. There would also need to be a consideration of the increased potential for algal blooms as a result of the neutral pH in the pond, if a carbon and phosphorous source inadvertently enters the TSF via run-off or leaf litter.

At a pH of ~10 and 13, the combined ammonia/ammonium that escapes as ammonia off-gas rises to greater than 67 and 87 %, by mass, respectively. It is evident that a higher pH results in greater ammonia evolution. For the Hydromet TSF, a pH of 13 would result in

approximately 3,900-5,300 kg/day of ammonia being released as off-gas, based off a ~76 t/h of inflow to the pond.

The impact of this ammonia gas release on the environment and health and safety of nearby workers is unknown; would require further modelling of air quality and risk.

4 Literature Review

The evolution of ammonia off-gas from TSFs at an elevated pH is supported by literature. For wastewater containing high levels of ammonia, the adjustment of the stream to a high pH (greater than 10.5) is recommended as a means for ammonia removal. A gas stripping tower is often used for removal, as are ponds (more infrequently) where wind/waves aid removal by increasing contact at the gas-liquid interface (Boyd & Tucker, 1998; Jermakka, et al., 2015).

This can be explained by the equilibrium reaction of ammonia and water, as follows:

H2O + NH3 ⇌ OH− + NH4+

It is evident that a higher concentration of hydroxide ions will shift the equilibrium towards ammonia formation, rather than ammonium. As ammonia gas readily evolves from water if unable to disassociate, a higher pH will result in greater quantities of off-gas than otherwise.

Figure 1 provides an illustration of this relationship under ideal conditions (i.e. for a simple ammonia/ammonium mixture).

Figure 1: Ammonia/Ammonium Concentration vs pH (Richard, 1996).

5 Conclusion

Speciation chemistry modelling demonstrated that ammonia off-gas evolution increases with an increase in pH. As the Hydromet TSF is likely to have a pH of 10 or greater, it can be expected that greater than two thirds of the ammonia/ammonium incoming to the pond will escape to the atmosphere as ammonia off-gas in the range of 3,900-5,300 kg/day (based on the worst case scenario).

The implications of this from an environmental, health and safety standpoint require further air quality modelling to quantify potential risks.

Kind Regards,

Matthew Brannock Technical Director – Water and Brine

References Boyd, C. E., & Tucker, C. S. (1998). Pond Aquaculture Water Quality Management. New York: Springer

Science + Business Media. Jermakka, J., Wendling, L., Sohlberg, E., Heinonen, H., Merta, E., Laine-Ylijoki, J., . . . Mroueh, U.-M.

(2015). Nitrogen compounds at mines and quarries: Sources, behaviour and removal from mine and quarry waters-Literature study. Tekniikantie: VTT Technical Research Centre of Finland Ltd.

Richard, T. (1996). Ammonia Odors. Ithaca: Cornell University: Waste Management Institute. Retrieved from http://compost.css.cornell.edu/odors/ammonia.html

ERM Level 18 140 St Georges Tce Perth WA 6000 PO Box 7338 Cloisters Square WA 6850

Telephone: +61 8 6467 1600 Fax: +61 8 9321 5262

www.erm.com

Page 1 of 19

Registered office Environmental Resources Management Australia Pty Ltd Level 15, 309 Kent Street Sydney NSW 2000 Australia

ABN: 12 002 773 248 ACN: 002 773 248

Offices worldwide

A member of the ERM Group

Lara Jefferson Environmental Manager Hastings Technology Metals Limited Level 8 Westralia Plaza 17 St Georges Terrace Perth WA 6000

6 May 2019

Reference: 0504573

Dear Lara Jefferson

Subject: Screening level Air Quality assessment of Ammonia emissions from the Hydromet TSF.

Hastings Technology Metals Ltd engaged ERM to undertake a screening level air quality modelling assessment of ammonia emissions from its Tailings Storage Facility (TSF) at the Yangibana Rare Earths Project operations. The modelling exercise is built on the previous work undertaken by ERM (Pacific Environment, 2017 and ERM, 2018).

The model assesses the emission rate for ammonia under a worst-case scenario, presenting a level of conservatism in the modelled results. Ground level concentrations were evaluated at a number of onsite receptor locations (42 onsite receptors considering plant locations, the creek and internal roads around the Hydromet TSF) and three offsite sensitive receptors considering the accommodation camp and two homesteads. Concentrations were predicted for 1-hour, 8-hour, 24-hour, 3-minute and 15-minute averages and compared against relevant ambient and occupational health and safety (OHS) air quality criteria. The following observations were made:

No exceedances of air quality criteria were predicted at the identified offsite sensitivereceptors.

One exceedance (25.75 mg/m3) of the 15-min OHS criteria was predicted at an onsitereceptor (TSF receptor 1) located within 250 m from the centre of the source (Figure 4-1)This exceedance occurred under worst-case conditions. The next worst case scenariopredicted a concentration of 12.89 mg/m3 at this same receptor. This concentration is wellwithin the criteria (50% of the criteria).

In summary, the modelling results indicate that the maximum concentration is of low likelihood to occur and dependent on concurrence of worst case emission rate and worst case dispersion conditions (i.e., prevalence of calm conditions, transition from stable to unstable meteorological conditions, and winds blowing towards this receptor).

Yours sincerely, pp.

Lavanya Gowrisanker Senior Consultant

ERM TSF Ammonia emissions Reference: 0504573 Page 2 of 19

1. BACKGROUND

Hastings Technology Metals Limited (‘Hastings’) is currently developing the Yangibana Rare

Earths Project (’Project’), which is located 270 km (line of sight) east-northeast of Carnarvon on Gifford Creek Station in the Gascoyne region of Western Australia.

This air quality assessment took into consideration the 2017 (Pacific Environment, 2017) assessment, which was submitted as part of the Environmental Approvals process. Additional modelling was undertaken (ERM, 2018) to determine the stack heights of point sources within the processing plant operations.

Hastings has now engaged ERM to undertake as screening level assessment to further understand the impact of ammonia emissions from the Hydromet TSF. The screening level assessment focuses on both ambient and occupational health and safety (OHS) levels of ammonia in the surrounding environment.

2. ASSESSMENT CRITERIA

Modelled concentrations are compared to the assessment criteria to provide an objective evaluation of the impact. In the absence of criteria specific to WA, criteria adopted by other States and Territories have been referenced. For assessment criteria specific to OHS, reference is made to Safe Work Australia’s Exposure Standards. A summary of the assessment criteria adopted for this study is presented below

Table 2-1: Ambient and OHS assessment criteria for NH3

Averaging

Period

Value Unit Value

Qualifier

Source

Am

bie

nt a

ir

24-houra 104 µg/m3 Maximum Ontario Ministry of Environment (Ontario

Ministry of the Environment, 2012)

1-houra 0.33

330

mg/m3

µg/m3

99.9th

percentile

NSW EPA (NSW EPA, 2017)

3-minutea 0.6

600

mg/m3

µg/m3

99.9th

percentile

Victoria Government Gazette (Government

of Victoria, 2001)

OH

S

8-hourb 25

17a

ppm

mg/m3

Maximum Australian Occupational Exposure

Standards (Safe Work Australia, 2018)

15-minutec 35

24a

ppm

mg/m3

Maximum Australian Occupational Exposure

Standards (Safe Work Australia, 2018)

Note:

a. Values at 273K and 101.3kPa

b. Time Weighted Average (TWA)

c. Short Term Exposure Limit (STEL)


2.1 Sub-hourly Concentration Results

Dispersion model predictions results are typically presented for hourly averages. For assessment criteria shorter than one hour, the hourly concentration must be scaled to estimate the sub-hourly peak concentration. The peak concentration was calculated using a peak-to-mean ratio. The power law relation equation shown below was used to calculate the sub-hourly concentrations (CSIRO, 2008).

𝐶𝑝 = 𝐶𝑚 × (𝑡𝑝𝑡𝑚)−𝑝

where:

𝐶𝑝 = Peak concentration µg/m3 𝐶𝑚 = One hour average concentration µg/m3 𝑡𝑝 = Peak time period minutes 𝑡𝑚 = One hour time period minutes 𝑝 = Source type power law exponent -

For this assessment, the value of p was set to 0.2 for ground level sources as presented in the Katestone report Peak-to-Mean ratios for Odour Assessments (1998). For this assessment, sub-hourly concentrations of 3 and 15 minutes were required for the pollutant modelled. The peak to mean ratios used in the assessment are summarised in Table 2.2 below.

Table 2.2: Peak-to-mean ratios

Averaging Period Peak-to-mean Ratio

3 minute 1.82

15 minute 1.32

3. AMMONIA EMISSIONS

Aqueous solution of waste streams from the processing plant are sent to the Hydromet TSF at a maximum rate of 76 tonnes /hour (tph) (78 m3/hour). This stream consists of approximately 0.04 g/L of ammonium bicarbonate and 6.28 g/L of ammonium hydroxide solution and releases ammonia once it comes into contact with ambient air (GHD, 2019). The formation and release of ammonia into the atmosphere is variable and highly dependent on the pH of the incoming waste stream and the frequency of the occurrence. The conditions favouring ammonia formation follow the equilibrium equation below.

𝐻2𝑂 + 𝑁𝐻3 ⇌ 𝑂𝐻− +𝑁𝐻4−

This equation shows that a higher concentration of hydroxide ions (higher pH – more alkaline solution) will shift the equilibrium towards the formation of ammonia. The rate at which ammonia is formed, is also proportional to the temperature of the waste stream.

For the current study, a worst-case scenario of 5,300 kg/day of ammonia was considered (GHD, 2019). This presents a level of conservatism in the model. The dispersion model was then set to run with a continuous unit emission rate of 61.3 g/s.


4. MODEL SET UP

For this assessment, dispersion modelling was undertaken using the USEPA approved model AERMOD (and AERMET, for the associated meteorological component). The model set up including selection of representative meteorological year; meteorological modelling, dispersion model setup remain unchanged from the 2017 modelling study (Pacific Environment, 2017). Given the remoteness of the Project location, background ammonia concentrations were assumed negligible.

Sensitivity analysis on the source configuration suggested that a smaller surface area expression of the volume source at the TSF stream entry point would result in higher concentrations at receptors in the vicinity. For the purposes of this assessment, source was configured whereby the surface area component of the volume source has a length of 450 m. This is selected because the formation of ammonia is an equilibrium driven process (occurring over a wider area) and not confined to the mouth of the TSF. An initial vertical dimension of 0.5 m was used as the depth at which ammonia was being formed.

4.1 Receptors The model was set to predict ground level concentrations across the model domain and at nominated sensitive receptor locations. A total of 45 discrete receptors were defined (Table 4-1): these include 42 onsite receptors (i.e. receptors within the plant boundary defined for OHS purposes) and three offsite receptors (one accommodation camp and two homesteads).

Table 4-1: Discrete receptor locations (onsite and offsite)

Receptor

Id

Description Type Easting

(m, MGA50)

Northing

(m, MGA50)

1 Plant 1 Plant Thoroughfare 427,534 7,353,963











12 Sample Preparation

Laboratory

Plant Building 427,550 7,353,849

13 Administration Plant Building 427,626 7,353,711

14 Crib and Locker Room Plant Building 427,609 7,353,689

15 Mining Office Plant Building 427,593 7,353,709


Receptor

Id

Description Type Easting

(m, MGA50)

Northing

(m, MGA50)

16 Mining Crib and Locker Room Plant Building 428,138 7,354,329

17 Heavy Vehicle Workshop Plant Building 428,108 7,354,409

18 Accommodation Village Workers

Accommodation

421,700 7,346,593

19 Gifford Creek Station Homestead 420,600 7,340,300

20 Edmund Station Homestead 410,370 7,371,700

21 Creek 1 Existing creek 426,703 7,352,862












33 Mine Road 1 Internal mine road 429,128 7,353,090

34 Mine Road 2 Internal mine road 428,905 7,353,302

35 TSF Receptor 1 Vicinity of TSF 428,536 7,352,950











These receptors are plotted in Figure 4-1 and Figure 4-2.

ERM TSF Ammonia emissionsReference: 0504573

Page 8 of 19

5. MODEL RESULTS

Ground level concentrations (maximum or 99.9th percentile) have been predicted across the model domain and interpreted at the nominated sensitive receptor locations. Modelled concentrations at:

offsite receptors have been compared to ambient air quality criteria.

onsite receptors have been compared to the relevant OHS guideline

5.1 Modelled results at offsite receptors Modelled 1-hour, 24-hour and 3-minute average concentrations at offsite sensitive receptors are compared against ambient criteria in Table 5-1. The results indicate that concentrations predicted across three offsite receptors are well within the ambient air quality criteria.

Table 5-1: Modelled concentration at offsite receptors

Receptor

Id

Description Type 1_houra

(µg/m3)

24_hourb

(µg/m3)

3_minutea

(µg/m3)

18 Accommodation Village Workers

Accommodation 28 7 51

19 Gifford Creek Station Homestead 19 5 34

20 Edmund Station Homestead 4 4 7

Ambient Air Quality Criteria 330 104 600

Note:

a. 99.9th percentile value

b. maximum value

Contour plots of 1-hour 99.9th percentile; maximum 24-hour and 3-minute 99.9th percentile concentrations are presented in Figure 5-1, Figure 5-2 and Figure 5-3 respectively.

ERM TSF Ammonia emissionsReference: 0504573

Page 12 of 19

5.2 Modelled results at onsite receptors Modelled 8-hour and 15-minute average concentrations have been compared against relevant OHS guideline and presented in Table 5-2. Contour plots for 8-hour and 15-minute averages are presented in Figure 5-4 and Figure 5-5 respectively.

The results indicate that the 8-hour criteria was met at all 42 onsite receptors; 15-minute criteria was met at all 42 onsite receptors, except one (TSF Receptor 1, 25.8 mg/m3). It should be noted that the second highest value (15-minute) predicted at this receptor was 12.2 mg/m3 at about 50% of the criteria (24 mg/m3). This is an indication that the likelihood of this predicted excursion is low.

Table 5-2: Modelled concentrations at onsite receptors

Receptor

Id

Description Type 8_hour

(mg/m3)

15_minute

(mg/m3)

1 Plant 1 Plant Thoroughfare 0.53 1.81











12 Sample Preparation

Laboratory

Plant Building 0.62 1.98

13 Administration Plant Building 0.87 2.12

14 Crib and Locker Room Plant Building 0.98 2.20

15 Mining Office Plant Building 0.95 2.16

16 Mining Crib and Locker

Room

Plant Building 0.63 4.49

17 Heavy Vehicle Workshop Plant Building 0.59 4.36

21 Creek 1 Existing creek 0.32 1.51








Receptor

Id

Description Type 8_hour

(mg/m3)

15_minute

(mg/m3)






33 Mine Road 1 Internal mine road 0.89 3.22

34 Mine Road 2 Internal mine road 1.21 3.89

35 TSF Receptor 1 Vicinity of TSF 6.45 25.75











Maximum across onsite receptors 6.45 25.75

OHS criteria 17 24

ERM TSF Ammonia emissions Reference: 0504573

Page 16 of 19

Further analysis was undertaken to identify the meteorological/dispersion conditions that give rise to the exceedance at TSF Receptor 1. The findings are presented in Table 5-3. Meteorological parameters investigated include atmospheric stability, wind speed and wind direction.

The results infer that the exceedance is predicted to occur during calm conditions just before sunrise and was associated with low inversion layers and wind direction blowing from the source, towards the receptor.

Table 5-3: Meteorological conditions that led to 15-minute excursion at TSF Receptor 1

Timestamp 15-min concentration (mg/m3) Stability Wind speed (m/s) Wind direction

06/06/2011 01:00 3.93 Very Stable 0.8 232

06/06/2011 02:00 4.86 Very Stable 0.7 225

06/06/2011 03:00 7.87 Very Stable 0.5 217

06/06/2011 04:00 8.34 Very Stable 0.5 198

06/06/2011 05:00 6.29 Very Stable 0.9 182

06/06/2011 06:00 5.33 Very Stable 1.1 174

06/06/2011 07:00 5.68 Very Stable 1 171

06/06/2011 08:00 25.75 Very Stable 1.2 165

06/06/2011 09:00 1.00 Unstable 1.8 160

06/06/2011 10:00 0.83 Unstable 1.9 157

06/06/2011 11:00 0.77 Unstable 1.9 158

06/06/2011 12:00 0.87 Unstable 2 163

5.3 Occurrence of worst case meteorology Additional investigation was undertaken to understand the hourly concentrations trends to aid in monitoring of NH3 for OHS purposes should this be determined necessary. Analysis included concentration trends based on period (month), time of day, wind speed and atmospheric stability. The following can be observed:

Higher concentrations are generally associated with lower wind speeds and very stable atmosphere.

Concentrations start to increase from 4 pm in the evening reaching maxima around 10 pm and starts to drops after 6 am in the morning.

Generally higher concentrations are predicted between July to October.


Figure 5-1: Predicted hourly concentration trends - month

Figure 5-2: Predicted hourly concentration trends – time of day


Figure 5-3: Predicted hourly concentration trends – wind speed

Figure 5-4: Predicted hourly concentration trends – atmospheric stability


6. REFERENCES

CSIRO. (2008). Calculate Peak to Mean Ratio. Retrieved from CSIRO Marine and

Atmospheric Research: https://www.cmar.csiro.au/airquality/peaktomean.html

ERM. (2018). Yangibana RAre Earths Project Plume Study.

GHD. (2019). Yangibana Hydromet Tailings Storage Facility (TSF) Ammonia Gas Modelling

Results.

Government of Victoria. (2001). State Environment Protection Policy (Air Quality

Management), No. S 240,. Victoria Government Gazette.

Katestone. (1998). Peak-to-mean Ratios for Odour Assessment. Report from Katestone

Scientific to Environment Protection Authority of New South Wales. Katestone

Scientific.

NSW EPA. (2017). Approved Methods for the Modelling and Assessment of Air Pollutants in

New South Wales. New South Wales EPA.

Ontario Ministry of the Environment. (2012). Ambient Air Quality Criteria (AAQCs). Standards

Development Branch Ontario Ministry of the Environment.

Pacific Environment. (2017). Final Report - Yanibana Rare Earths Project - Air Quality

Assessment - Doc No AQU-WA-005-21519. Pacific Environment Limited.

Safe Work Australia. (2018). Workplace Exposure Standards for Airbourne Contaminants.

Safe Work Australia.

GHD

2 Salamanca Square T: 61 3 6210 0600 F: 61 3 6210 0601 E: [email protected]

© GHD 2019

This document is and shall remain the property of GHD. The document may only be used for the purpose for which it was commissioned and in accordance with the Terms of Engagement for the commission. Unauthorised use of this document in any form whatsoever is prohibited.

Revision Author Reviewer Approved for Issue Name Signature Name Signature Date

A T.Ridgway B.Hanslow/D. Brett

On File B. Hanslow On File 14.3.19

0 T.Ridgway B. Hanslow On File B. Hanslow On File 30.3.19

1 T.Ridgway B. Hanslow On File B. Hanslow On File 04.06.19

www.ghd.com

APPENDIX 4-7 TSF Design Report

Documents

Transcript of APPENDIX 4-7 TSF Design Report