12/03/2021

RE:

Northern Star Resources (NSR) is seeking a Works Approval to allow an expansion of the Thunderbox mill. The expansion will increase nominal throughout of ‘Category 5- Processing and Beneficiation of Metallic or Non-Metallic Ore’ from 3 Million tonnes per annum to 7 Million tonnes per annum and ‘Category 52- Electrical Power Generation’ from 14.8MW in aggregate to 38MW. The Thunderbox Mill and Power Station are located on M36/542.

The proposed expansion will be completed via

- New primary jaw crushing circuit operating in parallel with the existing crushing circuit.

- New crushed ore stockpile, accepting crushed products from the existing and new crushing circuits.

- New 18 MW SAG mill.

- New pebble crushing circuit.

- New cyclone cluster.

- New gravity circuit.

- The existing 5.6 MW ball mill.

- Two new 4,100 m³ leach tanks.

- The existing carbon-in-leach (CIL) circuit.

- Conversion of the existing pressure Zadra elution circuit to split-AARL.

- New electrowinning cells to suit the new elution circuit.

- New (parallel) tailings thickener.

- Services upgrades as required.

- Addition of seven new 2.5MW generators.

The location of the mill and proposed layout are show in Figure 1 and Figure 2.

A detailed process description and Risk Assessment is included below.

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Figure 1: Location of the Thunderbox Mill in relation to existing and approved mining infrastructure

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Figure 2: Proposed Mill Layout

Process Description

The ore will be supplied from various mining locations all delivering to the run-of-mine (ROM) pad. Dump trucks or road trains deliver ore to the ROM stockpile area. ROM ore for the expansion will be crushed in two parallel crushing circuits:

• The existing primary crushing circuit, with a maximum throughput of ~3 Mtpa.

• New primary crushing circuit, with a maximum throughput of ~7 Mtpa.

Front end loaders will feed the two crusher ROM bins fitted with a static grizzly to prevent feeding oversize material to the crusher.

The new crushing circuit will consist of a ROM bin, apron feeder, vibrating grizzly and C160 jaw crusher. Crushed product with a nominal P80 of 150 mm will be combined with the crushed product from the existing crushing circuit (P50 = 25 mm) and conveyed to a new crushed ore stockpile.

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The new crushed ore stockpile will have a live capacity of 16-20 hours and include a stockpile cover to mitigate fugitive dust. Ore will be reclaimed from the stockpile by two apron feeders, supplemented with an emergency feeder outside the stockpile cover footprint. Each feeder will be sized to meet the SAG mill feed requirements.

The existing crusher ore stockpile, stockpile reclaim feeders and conveyors will be made redundant. The new primary crusher and crushed ore stockpile areas are shown in Figure 3.

Figure 3: New primary crusher and ore stockpile

A new 18 MW SAG will be fed from the new crushed ore stockpile. The SAG mill will operate in conjunction with the existing ball mill in the secondary grinding duty. SAG mill discharge will be screened, with the screen undersize pumped to a new cyclone cluster. Cyclone underflow will be split and report to the existing ball mill, new gravity circuit and new SAG mill. Ball mill discharge will be pumped back to the SAG mill discharge hopper. The SAG mill discharge screen oversize will be either recycled back to the mill feed to provide sufficient coarse media for grinding, or if required, crushed in a duty-only pebble crusher. Two magnets and a metal detector will be fitted to the pebble conveyors to remove tramp metal and protect the crusher. The existing SAG mill, associated pebble circuit and cyclone cluster will be made redundant. A new trash screens (duty) will be included in the grinding area, with the screen undersize pumped to the new leach circuit. Cyanide will be added to the leach feed hopper as is currently practised. Quicklime providing chemical stability to the cyanide added will be fed to the new SAG mill feed conveyor via a new 250t lime silo. The primary cyclone overflow line will be fitted with a sampler, with the sample directed to a particle size analyser. Analyser discharge will report to the leach feed hopper.

The existing gravity circuit consisting of 2 x 30” Knelson concentrators has insufficient capacity to treat a reasonable proportion circuit feed. As such, 2 x 48” Knelson concentrators will be installed with the Knelsons fed from the new primary cyclone underflow. The overall circuit will include 2 parallel scalping screens (one new, one relocated from the existing gravity circuit), with each screen feeding a single Knelson. The Knelson concentrates will be combined and treated in a new CS3000 Acacia, with the pregnant electrolyte pump to the goldroom area.

The new 18MW SAG Mill, hydrocyclone and gravity facilities are shown in Figure 4.

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Figure 4: New grinding, classification and gravity facilities

The existing CIL circuit will be supplemented with 2 x 4,100 m³ leach tanks to provide an overall circuit residence time of approximately 24 hours. The leach feed line will be fitted with an oxygen injector and the first tank will be fitted with an oxygen injection system that recirculates slurry from the bottom of the tank via an oxygen injector. The existing CIL tanks will each be retrofitted with a second intertank screen to accommodate the additional throughput. In total there will be two leach and seven adsorption tanks providing the required residence time for the purpose of leaching and adsorption.

The existing leach feed trash screen will be converted to a carbon safety screen, operating in parallel with the existing screen. The combined screen underflows will be split to maintain the required feed rate to the existing deslime circuit, with excess slurry gravitating to the existing tailings thickener. Deslime cyclone overflow will report to the new 18m diameter tailings thickener. The new thickener underflow (slimes) will be pumped to the paste plant via the existing pipeline, while the existing thickener underflow will be pumped via a new pipeline directly to the tailings storage facilities. The existing process water tank will be demolished to facilitate the installation of the new tailings thickener with a new process water tank constructed adjacent to the new thickener. Additional tailings storage dams are required for the expansion. Conceptual designs for a new TSF cell are under development and it is anticipated that approval will be sought under a subsequent version of this Mining Proposal once designs have been finalised.

The existing pressure Zadra elution circuit will be modified to a split-AARL configuration, including the installation of 2 new eluate tanks. To ensure sufficient electrowinning capacity, four of the existing 800 x 800 mm cells will be replaced with two 1200 x 1200 mm cells, operating in parallel. The existing Acacia electrowinning module will be replaced with a larger unit. The existing gravity electrowinning cell is suitably sized for the new duty and will remain in service.

Similar to current practises, tailings deposition will occur around the circumference of the TSFs with the supernatant solution being pumped off the centre of the tailings dam and recycled back to the process plant thickener.

A new cyanide and caustic offloading area will be located to the north of the existing facility. This is required as the selected grinding circuit location will impact on access to the existing offloading point.

Construction activities for the mill expansion is due to commence in July 2021, with the first ore milled and commissioning completed in August 2022.

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Groundwater Extraction

The water requirements for the increased plant throughput will initially be met through a nominal increase in the production rates of the existing licenced borefields and the reactivation of licenced but not used borefields (Sinclair). For the life of mine plan, a regional water study will be conducted with the view of identifying new borefield targets and additional capacity within the existing infrastructure areas.

The design of the process plant expansion will also incorporate a new tailings thickener to increase water recovery and provision in the design has also been made to incorporate a pre-leach thickener for future install if required. The new thickener will increase water efficiencies onsite by reducing the amount of water sent to tailings.

Table 1 below details total abstraction against allocation limits for the 2019-20 reporting period demonstrating there is ample room within existing Ground Water Licences to accommodate the increased mill demand.

Table 1: GWL Allocation and Abstraction

Emissions

Capacity of the Thunderbox Power Station will also to be increased to 38MW in aggregate with the addition of seven new 2.5MW gas powered generators. The footprint of the existing power station will be extended to the north house the new generators. Refer to Error! Reference source not found. 5 for the proposed extension area and Figure 6 for the proposed general arrangement.

Figure 5: Proposed Power Station Expansion Aerial View

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deposition rates, NSR will continue to discharge approximately 16% of total plant throughput as paste fill following the expansion.

NSR is in the process of completing a ten-year deposition strategy for the TSF, considering the installation of the Tailings Thickener and Paste Plant as well as with the expansion project. NSR will continue to raise the existing facility in sequential lifts as per standard practice in addition to constructing a third cell. The TSF is currently licenced for six more lifts on Cell A and seven more lifts on Cell B.

Tailings properties will not be significantly affected by the proposed throughput change, as the process will be essentially identical to current, albeit at an increased volume per hour.

The current TSF Cells were designed by NSRs Engineer of Record- Knight Piesold Consulting. The design of the TSF and the deposition strategy has been completed based on known characteristics of the tailings and with the knowledge of the Process Plant throughput increase to 7 million tonnes per annum. Seepage will be managed the same way regardless of the throughput increase, via pumping from the main decant and underdrainage columns at the TSF.

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Waste Emissions

Potential for waste emissions to air to breach licence limits.

C 2 M

(8)

Waste emissions, such as spoil from earthworks, packing material, scrap steel will be handled in accordance with existing waste management plans and will be disposed of, or recycled the same as all other current mine site wastes. All non-recyclable inert and putrescible wastes will be disposed of to the site landfill trenches as per the Operating Licence or sent off site to be disposed of at a licenced facility. All recyclable items (cardboard, paper, steel, poly pipe, etc.) will be sent off site for reuse or donated to local communities/stakeholders.

D 2 L (5) SGC-EN-PL-2901 Waste Management

Plan

Water Resources

Insufficient water management resulting in localised flooding or areas of water starvation.

B 3 H

(17)

A diversion drain has been designed to the west of the mill precinct to divert water to the south so it does not report to the mill area. The mill diversion drain will meet the larger western diversion drain which redirect water around the mining area.

Reinstating surface water flow is a closure objective.

D 2 L (5) SGC-EN-PL-2801 Water Management

Plan

Insufficient water management resulting in interaction of surface water with landforms and contributing to increased erosion/stability issues and poor surface water quality.

C 3 H (13) Water management structures constructed in accordance with their approved design specifications, and monitoring conducted to identify and correct any poor surface water quality.

A diversion drain has been designed to the west of the mill precinct to divert water to the south so it does not report to the mill area. The mill diversion drain will meet the larger western diversion drain which redirect water around the mining area.

Reinstating surface water flow is a closure objective.

D 3 M (9) SGC-EN-PL-2801 Water Management

Plan

Contamination of soil or groundwater due to hydrocarbon spills/leaks.

B 3 H

(17)

The design and construction of storage facilities is to Australian standards and maintenance is conducted as required.

Education and training is provided to personnel working on site regarding the correct storage and management of hydrocarbons and chemicals, as well as procedures for clean-up and remediation in the event of a spill.

All hydrocarbons are to be adequately bunded to ensure any spills or leaks are contained.

Spill kits are located in hydrocarbon storage areas.

In the event of a spill, contaminated soil is collected and removed to the bioremediation area for treatment. Education and training is provided to staff regarding the correct use of the bioremediation area.

All spills are reported to the environment department and recorded.

D 3 M (9) SGC-EN-PL-2701 Hydrocarbon and

Hazardous Substance Management Plan

SM-EN-WI-2708 Hydrocarbon and

Hazardous Substance Work Instruction

Biodiversity/ Flora/ Fauna/ Ecosystem

Vegetation clearing resulting in loss of vegetation biodiversity and fauna habitat.

B 3 H (17) Flora and fauna surveys are conducted to gain an understanding of the biodiversity within the project.

Vegetation clearing will be minimised to only those areas required to operate safely.

Areas of high environmental importance (such as waterways, breakaways, and other areas containing fauna habitat etc.) will be avoided where possible.

Cleared areas will be progressively rehabilitated when no longer in use to increase biodiversity in the area.

Malleefowl awareness has been an ongoing project for all Northern Star operations including the Thunderbox Project.

Fauna sighting records and fauna incident records are kept.

Northern Star has committed to engaging a qualified professional to conduct a targeted Malleefowl survey prior to clearing suitable habitat areas.

D 3 M(9) SGC-EN-PL-0001 Biodiversity

Management Plan

SM-EN-WI-2004 Clearing Management

Work Instruction

Clearing outside the approved disturbance envelope resulting in breach of tenement conditions.

C 2 M

(8)

Clearing approval will be gained from relevant government departments prior to commencement of clearing activities.

Clearing Activity Permits will be gained by personnel from the Environment Department outlining the area to be cleared, ensuring it is within approved envelope.

A copy of the permit with map of proposed clearing will be given to operators.

D 2 L

(5)

SGC-EN-PL-0001 Biodiversity

Management Plan

Potential for saline leaks, spills or spray to adversely impact the surrounding environment.

C 2 M (8) All pipelines saline pipelines are in bunded areas, v-drains or buried, which provide adequate containment in the event of a pipeline failure.

During pumping, saline pipelines are inspected twice daily and any leaks are reported and fixed.

Personnel are educated in spill clean-up procedures.

Dribble bars are installed on water trucks to avoid overspray impacting on roadside vegetation.

D 2 L (5) SGC-EN-PL-2801 Water Management

Plan

Tim Pavlos

Environmental Specialist

Northern Star Resources Limited

Encls

IR-F09 Application form Works Approval 7815/2001/11

Attachment 2a Premises Map

Attachment 2b TBO_Mine Infrastructure Map

Attachment 2c TBO_Mill Infrastructure Map

Attachment 2d TBO_ Expansion Infrastructure

Attachment 3a Commissioning Plan

Attachment 5 Consultation Register

Attachment 9 Fee Calculations