Supporting Technical Assessments

REPORT Hazardous Substances Technical Assessment Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Prepared for Oceana Gold (New Zealand) Limited Prepared by Tonkin & Taylor Ltd Date June 2022 Job Number 1015212.1000 vRev0 This document has been produced for New Zealand consenting purposes only. Information contained herein must not be relied on for investment purposes.

Document control Title: Hazardous Substances Technical Assessment Date Version Description Prepared by: Reviewed by: Authorised by: June 2022 Rev0 Hazardous substances technical assessment for resource consent application R Turnwald R Van de Munckhof J Simpson Distribution: Oceana Gold (New Zealand) Limited 1 electronic copy Tonkin & Taylor Ltd (FILE) 1 electronic copy

Executive summary OceanaGold (New Zealand) Limited (OGNZL) is seeking resource consent from the Hauraki District Council (HDC) and Waikato Regional Council (WRC) for the activities required to establish a new mining operation in the Wharekirauponga Valley. This new mine, referred to as the ‘Wharekirauponga Underground Mine’ (WUG), is part of the Waihi North Project (WNP) to extend the life of mining activities in Waihi. The WUG is located approximately 10 km north of the township of Waihi. The resource lies beneath the Coromandel Forest Park administered by the Department of Conservation (DOC) and within the Wharekirauponga Minerals Mining Permit (60541) area. This hazardous substances technical assessment has been prepared to evaluate the effect of hazardous substance storage and use associated with the establishment of the WUG and the mine access tunnel, which has a portal entrance on land owned by OGNZL on Willows Farm, Waihi. Hazardous substances will be both stored and used on the surface at Willows Road and underground within the tunnel and mine, which extends beneath the Coromandel Forest Park. The activity will include the storage and use of explosives, oxidising and toxic substances, workshop gases, fuels, maintenance oils and greases at the surface and within the underground mine. The storage and use of hazardous substances in New Zealand is governed primarily by the Health and Safety at Work (Hazardous Substance) Regulations 2017 which sets out control measures triggered by the volumes and types of hazardous substances proposed. Hazardous substance storage and use is further controlled by Resource Management Act 1991, exercised through Chapter 7.7. of the Hauraki District Plan (HDP). The proposed activity requires resource consent in accordance with the HDP Rule 7.7.10 as a non-complying activity for use of hazardous substances in the Conservation (Indigenous Forest) Zone at the WUG mine. This assessment has evaluated the hazards and risks in accordance with the Ministry for the Environment Guidance for Hazardous Facilities ME339 (2000), with supplementary guidance from the New South Wales Department of Planning’s Hazardous Industry Planning Advisory Paper series. The key risks identified for the Willows Road tunnel portal site and WUG mine include:  Risk to people or property from fire or detonation at the explosives magazines, oxidiser storage area or diesel tanks;  Risk to ecosystems from a spill of diesel during tank filling or equipment refuelling; and  Risk to ecosystems from a spill of packaged goods during unloading to site. The risks to people, property and the environment from an unintended detonation at the proposed explosives storage locations is assessed as low and will be managed through site and equipment design (e.g. separation distances to offsite locations and other explosives stores, provision of fire protection systems and certification of the explosives storage magazines) and management controls (personnel access restrictions, security monitoring, staff training and handler certification, and emergency response plans). The surrounding areas at the surface at Willows Road and in the Coromandel Forest Park above the WUG are considered sensitive to the effects of an unintended detonation. However, taking into account the proposed controls and distance to sensitive land uses, the effects on offsite people and property from the proposed hazardous substances storage has been assessed as less than minor. Similarly, the impact of a detonation of the Class 1 explosives in the WUG has potential to impact people in the Coromandel Forest Park in the vicinity of the mine ventilation stacks. A quantitative assessment of the effect using dispersion modelling was undertaken in an Air Quality Assessment,

which found that even with a number of conservative inputs, criteria for the protection of human health is met at all locations around the surface connections. The risks to people, property and the environment from a fire at the surface facilities area of the Willows Road portal entrance site is low and managed through site and equipment design (e.g. separation of incompatible substances, combustible material and ignition sources and provision of fire fighting facilities) staff training, and emergency response plans. The proposed hazardous substances storage locations are isolated from public access. The environment is considered sensitive to the effects of a spill of diesel or spill of packaged goods. The risk to the environment will be managed through the site design (e.g. proposed spill containment measures including double skinned tanks, sealed refuelling areas, bunded storage areas and provision of water treatment for runoff arising from areas where these substances are stored or used) and operational procedures (e.g. spill response plan, unloading and safe handling procedures). Taking into account these controls, the effects on the environment from the use and storage of hazardous substances have been assessed as less than minor and consistent with the HDP objectives and policies for hazardous substances.

Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Table of contents 1 Introduction 1 1.1 Project overview 1 1.2 Assessment approach and background documents 1 1.3 Definitions 2 2 Description of proposed activities and substances 2 2.1 Site location 2 2.2 Proposed activities involving hazardous substances 3 2.2.1 Willows Road portal site 3 2.2.2 WUG 4 2.3 Hazardous substances classification and quantities 5 3 Sensitivity of local environment 9 3.1 Willows Road portal entrance site 9 3.2 WUG 11 4 Control and management of hazardous substances 13 4.1 Introduction 13 4.2 Health and Safety at Work (Hazardous Substances) regulatory controls 14 4.2.1 Magazine certification 16 4.2.2 Magazine separation 16 4.2.3 Hazardous substance location for ANE 18 4.3 Hazardous substances management 19 4.4 Explosives hazard management 20 4.4.1 Explosives management plans and responsibilities 20 4.4.2 Security 20 4.4.3 Fire protection systems 20 4.4.4 Ventilation (underground) 21 4.5 Emergency management 21 4.6 Secondary containment 21 4.7 Separation requirements 24 4.8 Refuelling area 25 4.9 Water treatment 26 4.10 Signage 26 4.11 Transport of hazardous substances 26 4.12 Waste management 28 5 Overpressure offset distances assessment 29 5.1 Overview 29 5.2 Surface magazine offsets 29 5.3 Underground explosives storage facility offsets 32 6 Resource consent requirements 36 7 Risk Assessment for Hazardous Substances 37 7.1 Introduction 37 7.2 Assessment method 37 7.3 Risk assessment 38 7.3.1 Hazard analysis 38 7.3.2 Partial Quantitative analysis of Class 1 explosion 41 7.3.3 Risk analysis 44 8 Assessment of effects 46 8.1 Introduction 46

1 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 1 Introduction 1.1 Project overview OceanaGold (New Zealand) Ltd (OGNZL) is seeking resource consent from the Hauraki District Council (HDC) and Waikato Regional Council (WRC) to establish a new mining operation known as the ‘Wharekirauponga Underground Mine’ (WUG) as part of the Waihi North Project (WNP). The WUG is located approximately 10 km north of the township of Waihi. The resource lies beneath the Coromandel Forest Part administered by the Department of Conservation (DOC) and within the Wharekirauponga Minerals Mining Permit (60541) area. The proposal includes the storage and use of hazardous substances to service the establishment and operation of the mine with a portal entrance on land owned by OGNZL at Willows Road, Waihi. The portal entrance site will include surface storage of six high explosives (H.E) magazines, one initiating explosives (I.E) magazine, a store for oxidising substances and storage of fuels, workshop gases and oils for servicing equipment. Once access to the ore body has been established (within four years), it is expected that underground facilities will be established for the substances regularly used at the mining face. This will include establishment of six H.E and I.E. storage chambers, two compounds for storage of oxidising substances, one for gasser (a low toxicity substance for use with the oxidisers) and up to two small portable diesel tanks within the mine extending beneath the Coromandel Forest Park. The storage and use of hazardous substances is governed primarily by the Health and Safety at Work (Hazardous Substance) Regulations 2017 and further controlled by Resource Management Act 1991 via the Hauraki District Plan (HDP). The proposed use and storage of hazardous substances in the quantities proposed requires resource consent in accordance with the HDP. Any new storage and use of hazardous substances under Rule 7.7.12(5) requires the use of the Hazardous Facility Screening Procedure (HFSP) to calculate an effects ratio for the activity, which can be compared to the permitted and restricted discretionary effects ratio thresholds set for each zone. However, there are no effects ratios provided for activities in the Conservation (Indigenous Forest) Zone, and as such the storage of substances in the mine is a non-complying activity under Rule 7.7.10 of the HDP. Tonkin & Taylor Ltd (T+T) has been engaged by OGNZL to prepare this hazardous substances assessment to support resource consent applications being prepared by OGNZL. This report has been prepared in accordance with our engagement letter dated 27 August 2021. 1.2 Assessment approach and background documents The approach to hazardous substances risk assessment in this report has been informed by the following sources, which are referenced where relevant:  Assessment Guide for Hazardous Facilities (ME339), Ministry for the Environment, 2000  Assessment Guideline, Multi-level Risk Assessment. State of New South Wales through the Department of Planning, 2011  Land Use Planning Guide for Hazardous Facilities, Ministry for the Environment, 2002  Hazardous Industry Planning Advisory Paper No.4, Risk Criteria for Land Use Safety Planning. State of New South Wales through the Department of Planning, 2011  Decision making: A technical guide to identifying, assessing and evaluating risks, costs and benefits, Environmental Risk Management Authority, 2009

2 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 The assessment of the impact of explosives has been informed by two assessments prepared by Global Seismic Solutions (GSS): theWillows Road – Surface Magazine Location Assessment, Waihi North Project, 20 October 2021 attached as Appendix A and theWharekirauponga Underground Mine (WUG) Class 1 Storage Assessment, 10 December 2021 attached as Appendix B. The GSS reports identify the following supplementary guidance which informed the design of the facilities and quantification of impacts from Class 1 explosives storage:  AS 2187.1 Explosives—Storage, Transport and Use, Part 1: Storage  International Ammunition Technical Guideline (IATG 2.20), Quantity and Separation Distances (United Nations - Safer Guard) (2nd Edition 01.02.2015)  International Ammunition Technical Guideline (IATG 1.80), Formulae for Ammunition Management (United Nations - Safer Guard) (2nd Edition 01.02.2015). This assessment report has been prepared to supplement theWaihi North Project – Resource Consent Applications and Assessment of Environmental Effects prepared by Mitchell Daysh Limited, dated June 2022. 1.3 Definitions The following terms are used throughout the report and have distinct meanings as set out in the Ministry for the Environment’s Assessment Guide for Hazardous Facilities (2000) or the Resource Management Act 1991:  Hazard – describes physical situations, process and/or actions that have the potential to exert adverse effects on people, ecosystems and/or the built environment.  Risk – is the likelihood of specified consequences of a specific event (e.g., explosion) on people, ecosystems and/or the built environment. Therefore, the magnitude of risk is the product of probability and consequence (Risk = Probability x Consequences).  Effect – means any impact or change as a result of an activity and, as defined by Section 3 of the RMA, can be positive or negative, temporary or permanent, applicable to the past, present or future, or cumulative with other effects. 2 Description of proposed activities and substances 2.1 Site location Figure 2.1 shows an overview of some of the key elements of the WNP, from the tunnel portal to the WUG in the Coromandel Forest Park. The key supporting infrastructure is proposed to be located at the tunnel portal entrance site at Willows Road, Waihi and is referred to as the surface facilities area (SFA). At a later stage in the WUG development, some hazardous substances storage will be located underground within the WUG to facilitate the mining operations.

3 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Figure 2.1: Overview of portal entry at Willows Road, tunnel pathway and WUG mine area 2.2 Proposed activities involving hazardous substances 2.2.1 Willows Road portal site The following activities at the Willows Road tunnel portal site (seeFigure 2.2) will store and use hazardous substances:  Storage of explosives at six H.E magazines and one I.E magazine located southwest of the portal. These explosives substances will be transported via an internal access road to the tunnel portal where they will be charged at the development face and within the underground mine;  A store for ammonium nitrate emulsion and gasser will be established at the northern end of the SFA adjacent to the portal. These two substances will be transported via internal access road and used in tunnel development and underground mining;  A covered, sealed service workshop in the SFA that will store gas cylinders (oxygen, acetylene) for welding/cutting and oils and greases for servicing of mechanical equipment;  Diesel will be stored in above ground double skinned refuelling units at a services bay in the SFA; and  A smaller volume of diesel may also be stored in association with the fire protection system to power the water pumps and in a small tank to service the site emergency power generator. Table 2.1 details the proposed quantities and locations of hazardous substances at Willows Road.

4 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Figure 2.2: Layout of Willows Rd portal entrance site highlighting key areas Source: OGNZL Civil drawings showing details of the SFA layout are included inAppendix C. 2.2.2 WUG At a later stage of WUG development, underground hazardous substances stores are proposed as follows:  Storage of explosives in six separate H.E. chambers and one I.E. chamber;  Storage of ammonium nitrate emulsion (ANE) and gasser, which are mixed in-situ to produce an explosive substance when packed into the blast hole; and  Up to two small portable double skinned refuelling units containing diesel. Deliveries of these substances will be made at either the Willows Road or Waihi portal entrance sites and transported via tunnel to the underground storage locations indicated onFigure 2.3. The H.E. and I.E. chambers will be located at a depth of 380 m.

5 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Figure 2.3: Underground mine layout showing the key hazardous substance storage locations. Section looks west. Source: OGNZL 2.3 Hazardous substances classification and quantities The hazardous classifications for the substances are assigned under the Hazardous Substances and New Organisms Act 1996 (HSNO) and outlined inTable 2.1 below. As a new hazard classification system came into force in New Zealand on 30 April 2021, both the former classifications from the safety data sheet and the equivalent new classification are presented, as the former classification remain in use in the relevant regulations. Proposed location of explosives storage facility Varying surface connections where controlled zones apply. Proposed locations of ANE and gasser storage

6 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Table 2.1: Hazardous substance volumes and classifications Substance State of substance HSNO Class Pre-2021 Hazard classification Post 2021 Proposed maximum volume Storage Location ANFO (UN 0082) Solid 1.1D, 6.1D, 6.3B, 6.7B, 9.1D 1.1D - Substances and articles that have a mass explosion hazard Acute toxicity Category 4 (oral route) Eye irritation Category 2 Carcinogenicity Category 2 Hazardous to the aquatic environment chronic Category 4 7,350 kg NEQ 6,100 kg NEQ Surface explosive magazines (max 1,300 kg NEQ in any magazine) Underground chambers (max 1,000 kg NEQ in any chamber) Booster (UN 0042) Solid in card or plastic casing 1.1D, 6.1C, 6.9B, 9.1B 1.1D - Substances and articles that have a mass explosion hazard Acute toxicity Category 3 (oral, dermal and inhalation route) Specific target organ toxicity – single exposure Category 2 Hazardous to the aquatic environment chronic Category 2 Packaged explosive (UN 0241) Plastic encapsulated emulsion 1.1D, 6.1D, 6.3A, 6.4A, 6.8C, 6.9A, 9.1A, 9.3C 1.1D - Substances and articles that have a mass explosion hazard Acute toxicity Category 4 (oral route) Skin irritant Category 1 Eye irritation Category 2 Reproductive toxicant Category 3 Specific target organ toxicity – repeated exposure Category 1 Hazardous to the aquatic environment Category 1 Harmful to terrestrial vertebrates Detonators (UN 0030 / UN 0456 / UN 0360) Solid article 1.1B 1.1B - Substances and articles that have a mass explosion hazard 10 kg NEQ (10,000 articles) Surface explosive magazine (separate to others) 100 kg NEQ (100,000 articles) Underground chamber (separate to others) Diesel Liquid 3.1D, 6.1E, 6.3B, 6.7B, 9.1B Flammable liquids Category 4, Aspiration hazard Category 1, See Note 1 Carcinogenicity Category 2, Hazardous to the aquatic environment chronic Category 2 80,000 L Services bay at the SFA 6,000 L WUG portable tanks 550 L Generator tank at the SFA 150 L Fire pump at the SFA

7 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Substance State of substance HSNO Class Pre-2021 Hazard classification Post 2021 Proposed maximum volume Storage Location Ammonium nitrate emulsion (ANE) Solid 5.1.1B 6.1E 6.4A 9.1D Oxidising solids Category 2 Aspiration hazard Category 1, Eye irritation Category 2 Hazardous to the aquatic environment chronic Category 4 40,800 kg Oxidiser intermediate bulk containers (IBC) storage area – SFA 34,000 kg Oxidiser IBC storage area – underground Gasser Liquid 6.1D 6.4A 6.5B 6.6B 6.9B Acute oral toxicity Category 4 Eye irritation Category 2 Skin sensitisation Category 1 Germ cell mutagenicity Category 2 Specific target organ toxicity – repeated exposure Category 2 8,000 L Gasser IBC storage area – SFA 4,000 L Gasser IBC storage area – underground Calcium carbonate (Lime) Solid 6.4A Eye irritation Category 2 70,000 kg Lime silo in SFA Oxygen gas Compressed gas 5.1.2A Oxidising gas Category 1 60 m3 Up to ten cylinders in a segregated storage area in the workshop in the SFA Acetylene gas Compressed gas 2.1.1A Flammable gas Category 1A, Chemically unstable gas Category A 20 m3 Up to four cylinders in a segregated storage area at the workshop in the SFA Oils, greases* Liquid 6.1D 6.1E 6.3A 6.4A 6.5B 6.9B 9.1B 9.1C Acute dermal toxicity Category 4 Aspiration hazard Category 1 Skin irritation Category 2 Serious eye damage Category 1 Skin sensitisation Category 1 Specific target organ toxicity – single or repeated exposure Category 2 Specific target organ toxicity – single exposure Category 3 narcotic effects Hazardous to the aquatic environment chronic Category 2 or 3 8,000 L Bulk tanks, IBCs or drums in workshop stores in SFA * Majority of the maintenance oils and greases are non-hazardous. The above table shows the highest individual hazard classifications for the range of workshop substances.

8 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 The Class 1 explosive substances will be stored in six H.E magazines (for the ANFO, boosters and packaged explosives) and one I.E magazine (for the detonator devices) at the surface site on Willows Road. Once the underground mine is established, an additional storage facility for Class 1 explosives will be set-up underground near the resource, at a depth of 380 m below the surface. This will also comprise of six separate H.E. chambers and one I.E. magazine. The key hazard associated with these substances is the mass explosion hazard producing a blast overpressure impact around the surface magazine, and at the surface vents for the underground store. The oxidising substance, ANE, will be stored in a secure bunded compound at the SFA east of the portal entrance, and once the underground mine is established, at two underground stores near the WUG orebody. These stores will be separated from the underground explosives store location by approximately 130 m and 405 m respectively. The key hazard associated with ANE is the acceleration of fire, which requires management through separation from combustible materials. A suitably segregated gasser store will also be established at the SFA and later below ground. Gasser is a liquid with subsidiary low human health hazards by direct exposure. The ANFO, packaged explosive, boosters and ANE also present human health and environmental hazards. However, the inherent properties of the materials limit their mobility. The ANFO is provided as a granular solid. The boosters and packaged explosive are a granular solid packaged in cardboard tubes and a liquid emulsion in small plastic tubes respectively, and the ANE is a highly viscous emulsion that is considered a solid for the purpose of transport and storage1. In the event of a spill, these substances are easily contained and cleaned up with a low risk of contamination of waterways. Oxygen and acetylene gases will be stored and used at the workshops on the western side of the SFA for welding and cutting tasks. Acetylene is a highly flammable gas and oxygen will accelerate a fire; these gases are incompatible and will be stored separately in well ventilated, secure locations at the workshop. Diesel, gasser and some of the maintenance oils are liquids with chronic human health hazards. Diesel and some of the oils are also hazardous to aquatic ecosystems. These substances will be stored and used in bunded areas and in areas that drain to stormwater treatment. The distance between the proposed storage locations and OGNZL’s boundary limits the potential for off-site persons to come into contact with any released material in the case of a spill. Similarly, lime has a human health hazard when in direct contact with eye tissue. Lime is a solid powder that is able to be easily managed in the event of a spill. It is stored and used central to the site suitably separated from the site boundary, minimising the chance of contact with the public. 1 ANE safety data sheet, Orica New Zealand Limited, 27 November 2019

9 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 3 Sensitivity of local environment 3.1 Willows Road portal entrance site The portal entry and areas of hazardous substance storage (the SFA and at the surface explosives magazine compound) are located entirely within land owned by OGNZL. This land is zoned Rural under the Hauraki District Plan (HDP). The tunnel itself extends to the Wharekirauponga ore body beneath the Conservation (Indigenous Forest) zone which is also scheduled as a Significant Natural Area (seeFigure 3.1). Figure 3.1: Surrounding land zoning of areas around the Willows Rd site (OGNZL owned land outlined in red) (map derived from: Hauraki-dc-govt.nz) The nearest Residential Zone land is the township of Waihi approximately 2 km southwest of the portal entry. The closest dwellings are located in the Rural Zone to the south, approximately 580 m away from the explosive magazines, as shown inFigure 3.2 below. The Rural zoning of the land to the south provides a buffer of low-density land use between the Willows Rd site and the Waihi township residential areas. However, use of this land for rural residences and farming and the recreation opportunities provided by land to the north (Coromandel Forest Park) means the surrounding land uses are potentially sensitive to the effects associated with explosives storage at the proposed explosives magazines and the storage of oxidisers adjacent to the portal entry. The Mataura Stream flows along the northern border of the site with the Coromandel Forest Park. It bisects the site north of the SFA and connects with the Ohinemuri River southeast of the site. The stream is sensitive to effects associated with spills of ecotoxic materials.

\\ttgroup.local\files\AKLProjects\1015212\WorkingMaterial\GIS\HSA WKP Oceania Gold 1015212.aprx Layout: FIG3.2_DistancesToSensitiveReceptors 2022-May-06 9:32 am Drawn by ANDO COPYRIGHT ON THIS FIGURE IS RESERVED DO NOT SCALE FROM THIS FIGURE. DRAWN CHECKED APPROVED DATE PROJECT No. DESIGNED CLIENT PROJECT TITLE SCALE (A4) FIG No. REV NOTES: REVISIONS NO. BY Mataura Stream Surface Facilities Portal entrance Surface Magazines R1 (640 m) R2 (595 m) R3 (740 m) R4 (995 m) R5 (1085 m) R6 (730 m) R7 (775 m) R8 (815 m) R9 (1135 m) 1015212.1000 MAY.22 ANDO OCEANA GOLD NEW ZEALAND LIMITED WAIHI NORTH PROJECT - WILLOWS ROAD SITE DISTANCES TO SENSITIVE RECEPTORS FROM SURFACE EXPLOSIVE MAGAZINES 1:11,000 FIGURE 3.2 2 MAY.22 ANDO Basemap: Eagle Technology, Land Information New Zealand (CC-BY-4.0), OpenStreetMap Contributors ANDO 0 First version (12/11/2020) LOCATION PLAN LEGEND Site Boundary Parcel Boundary Surface Facilities Area Receptor distance from magazines (nearest 5m) Surface Magazines Portal Entrance A4 SCALE 1:11,000 0 130 260 390 Meters MAY.22 JORB ANDO 1 Minor changes (05/10/2021) ANDO 2 Minor changes (06/05/2022)

11 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 3.2 WUG The WUG ore body is located beneath the Conservation (Indigenous Forest) Zone as shown on Figure 3.3. Due to the depth at which the Class 1 explosives facility is proposed to be located, the receiving environment relevant to the impacts to off-site people, property or the environment is considered to be in the vicinity of the surface connections. An isometric view of the surface connection locations is also included as Figure 3.4 below, two of which (the portal and one vent shaft) are on the Willows Road portal site described in Section 2.2.1 above. Figure 3.3: Surrounding land zoning of areas around the WUG mine, blue dots showing indicative location of surface connections (source: OGNZL) In the event of an unintended detonation in the underground explosives storage facility, the overpressure would propagate through the mine space and be expelled at the surface connections, which include the access portal, fresh air intakes and return air rises. The surface connection configuration is illustrated inFigure 3.4 below. These locations are the key sites at which there is potential for effects on off-site people or property in the event of an unintended detonation at the storage facility.

12 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Figure 3.4: Underground storage facility location in relation to surface vents (source: GSS, 2021. Note: Site numbering has been adjusted for consistency with more recent reports) The surface connection locations, zoning under the HDP and public accessibility are detailed inTable 3.1 below. Table 3.1: Description of surface connections (GSS, 2021) Site ID1 Zone Description Proximity to WUG Site 1 – Waihi Portal Martha Mineral The portal for receipt of the ore for processing at the nearby processing plant. This is within OGNZL’s industrial site and is not accessible to the public. Approximately 10 km southeast of the WUG. Site 2 – Willows Portal Rural The main access portal to the mine consists of a large horizontal type decline that is used as the main entry/ exit route to the WUG. Approximately 7 km southeast of the WUG. Site 3 – Willows Rd Farm Fresh Air Intake Rural This fresh air intake connection is location within OGNZL owned land at the northern end of the Willows Road site. Approximately 6 km from the WUG. Site 4 – WUG Rise #1 Conservation (Indigenous Forest) The WUG Rise #1, #2 and #3 are each located within the HDC paper road boundary in a remote forested area. This road is not maintained as a public walkway. However, each proposed location will consist of a 10 m x 10 m area Approximately 0.9 km from the WUG Class 1 store. Site 5 – WUG Rise #2 Conservation (Indigenous Forest) Approximately 0.6 km from the WUG Class 1 store. Proposed Underground Storage Facility – 380 m below surface Surface Portals/ Ventilation shafts which require consideration for controlled zones in the event of unintended detonation. Site 4 - WUG Rise #1 Site 5 - WUG Rise #2 Site 6 - WUG Rise #3 Site 3 - Willows Rd Farm, Fresh Air Intake Site 2 - Willows Rd Farm, Portal

13 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Site ID1 Zone Description Proximity to WUG Site 6 – WUG Rise 3 Conservation (Indigenous Forest) with a perimeter fence restricting access to members of the public. Rise #1 and Rise #3 are fresh air intakes, only Rise #2 will exhaust air from the mine when the mine’s ventilation system is operational. Approximately 0.7 km from the WUG Class 1 store. 1. Site names updated for consistency with other reports. Two of the connections (2 & 3) are on OGNZL owned land at Willows Road, and three are located within the Coromandel Forest Park on the paper road. While there is an old walkway along the paper road (shown south of the WUG onFigure 3.3), this is not maintained as a public walkway and therefore not used by members of the general public. The surface connections in the Coromandel Forest Park are air vents or intakes, an example of which is included as Figure 3.5 below. The location of each surface connection will be securely fenced off to exclude members of the public from close proximity to the area. Figure 3.5: Typical return air rise vent Source: OGNZL 4 Control and management of hazardous substances 4.1 Introduction The key legislation in New Zealand for management of hazardous substances within the broader regulatory framework are:  Health and Safety at Work (Hazardous Substances) Regulations 2017 (HSW-HS), which is administered by WorkSafe and sets rules for the storage and use of hazardous substances in the workplace, including risks to workers;  Health and Safety at Work (Major Hazard Facilities) 2016 Regulations (HSW-MHF) which is also administered by WorkSafe and mandates specific duties relating to process safety that apply to facilities that exceed specified volumes of hazardous substances;

14 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0  Hazardous Substances and New Organisms (HSNO) Act and Regulations, which set minimum controls under the Environmental Protection Authority’s Hazardous Property Controls Notice 2017 (EPA Notice) to manage the hazards and risks related to all hazardous substances use within domestic environments and from ecotoxic substances in both workplaces and domestic settings; and  Resource Management Act (RMA), under which District Councils are responsible for the control of actual or potential effects of the use, development, or protection of land. The Resource Legislation Amendment Act 2017 (RLAA) removed the explicit function of regional and territorial authorities under section 30 and 31 to control the adverse effects of the storage, use, disposal and transportation of hazardous substances to ensure that RMA controls do not duplicate controls in the HSNO Act and Health and Safety at Work Act. The controls under the HSNO Act and HSW Act provide the minimum protection standards for both onsite and offsite people and environments from the potential adverse effects. However, we note that the controls do not take into account the site-specific context such as the proximity to sensitive waterways or density of nearby residential developments. 4.2 Health and Safety at Work (Hazardous Substances) regulatory controls Control measures that are triggered under the Health and Safety at Work (Hazardous Substances) regulations (HSW-HS) by the volumes and types of hazardous substances proposed to be stored at the Willows Road portal site and within the WUG are summarised in Table 4.1 below. The operation is required to comply with all the listed requirements. These HSW-HS controls are specific to the types of hazard presented by the substances and are implemented to protect people on site from harm. The measures to reduce the likelihood or consequence of an incident to on-site workers will also reduce the risks to off-site people. The controls specified for Class 9 ecotoxic substances duplicate those specified under the EPA Notice which are intended to protect ecosystems when using and storing ecotoxic substances. Table 4.1: Summary and purpose of HSW-HS requirements Control measure Facility and substances Purpose of control Signage SFA  Flammable, oxidising, corrosive, ecotoxic and explosive substances WUG  Flammable, oxidising, ecotoxic and explosive substances Ensures-off site persons and emergency response personnel are able to identify the hazards at the site and take appropriate precautions. Secondary containment SFA  Diesel, ANE, gasser, maintenance oils WUG  Diesel, ANE and gasser Prevents release of a hazardous liquid to the environment in the event of a failure of primary containment (tank or package) and enables recovery of the substance for safe disposal. Fire extinguishers SFA  Diesel, ANE, oxygen and Class 1 explosives WUG Enables swift emergency response to small fires in areas near hazardous substances to prevent ignition of flammable, explosive or oxidising substances.

15 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Control measure Facility and substances Purpose of control  Diesel, ANE and Class 1 explosives Segregation of incompatible substances SFA  Diesel, ANE, gasser, oxygen, acetylene and Class 1 explosives WUG  Diesel, ANE, gasser and Class 1 explosives Minimises additional adverse consequences from a spill or fire by preventing reactive substances from mixing in the storage area. Substance secured from unauthorised access SFA  ANE and Class 1 explosives WUG  ANE and Class 1 explosives Limits access to trained personnel and minimises the potential for operator error or tampering. Emergency response planning SFA  Diesel, ANE, gasser, lime and Class 1 explosives WUG  Diesel, ANE, gasser and Class 1 explosives Describes the emergency procedures for a site and takes into account any foreseeable emergency such as a fire, spill or injury. Emergency Response Plans must be regularly tested by the site. These plans help to minimise the consequence of an emergency event, such as through preventing a small spill reaching a drain, extinguishing a small fire or enabling safe evacuation of an effected area. Separation from public and protected spaces SFA  Diesel, ANE, acetylene and Class 1 explosives WUG  Diesel, ANE and Class 1 explosives Minimises any adverse event in the store impacting on public places or protected places, and correspondingly any off-site event from impacting the store. Certified handler SFA  Class 1 explosives WUG  Class 1 explosives A Certified Handler is a person who is trained and qualified (holds a Certified Handler Compliance Certificate) to handle acutely toxic or explosive substances. This control restricts activities involving these substances to people with demonstrated competency. Hazardous Substances Location Compliance certification required SFA  Diesel, ANE and Class 1 explosives WUG  Diesel, ANE and Class 1 explosives Independently certifies that the hazardous substance location where explosive, flammable, oxidising, toxic or corrosive substances are stored or used, has in place all applicable controls and notifications to manage the hazards (such as segregation of incompatibles, secondary containment, access restrictions). Stationary Container System Compliance certification required SFA  Diesel WUG  Diesel Independently certifies that the tank or process container and associated equipment is safe and complies with the standards for tank design, such as providing secondary containment, pressure relief and overfill protections. Separation from land use activities according to potential SFA  Diesel, ANE and Class 1 explosives WUG Minimum separation distances for blast overpressure levels are specified to ensure that people and structures are located at a suitable distance from the explosive hazard for protection from adverse effects.

16 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Control measure Facility and substances Purpose of control overpressure levels (controlled zones)  Diesel, ANE and Class 1 explosives Hazardous areas (ignition source restrictions) SFA  Diesel, acetylene WUG  Diesel Prohibits ignition sources from areas where flammable substances are stored to minimise the risk of a fire. Earthing and bonding of equipment SFA  Diesel and class 1 explosives WUG  Diesel and class 1 explosives Minimises risk of an ignition source from build-up of static charge starting a fire at a flammable or explosives store. 4.2.1 Magazine certification The HSW-HS regulations require any storage of Class 1.1D explosives in excess of 2.5 kg to be secured in a magazine designed and certified to meet requirements for the material of construction, the design of the locking arrangement and arrangements for prevention of removal. The magazine is also required to have an earthing system between the atmosphere above the hazardous substance location and earth to dissipate any build-up of electrostatic charge. The magazines must also have a lightning interceptor designed in accordance with section 4 in AS/NZS 1768: 2007—Lightning protection. These features are required to minimise the risk of an inadvertent ignition of the explosives. The magazines used by OGNZL at the surface will be designed to standard AS 2187.1 1998 for relocatable magazines and design compliance certificates will demonstrate that the requirements set in the HSW-HS regulations are met by the proposed magazines. While the underground chambers are not strictly magazines as would be used on the surface, equivalent standards for security, design and construction will be adhered to, and the facility will be certified by an independent compliance certifier. 4.2.2 Magazine separation 4.2.2.1 Surface magazine At the surface magazine, the H.E. will be stored in six separate magazines, three containing a maximum of 1,150 kg Net Explosive Quantity (NEQ) and three containing a maximum of 1,300 kg NEQ. Each magazine must be separated by a minimum distance of 27 m, with mounding undertaken in accordance with industry standard ‘AS 2187.1, Appendix B’, to ensure the distances can be maintained in order to mitigate risk of inter-magazine propagation. The 10 kg NEQ I.E. magazine may be located within 27 m of another magazine, however, in accordance with AS 2187.1, a minimum offset of 3.5 m (mounded) or 10 m (un-mounded) shall be maintained. The proposed layout of the surface magazine compound is indicated inFigure 4.1 .

17 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Figure 4.1: Proposed surface magazine layout indicating internal magazine offsets, positioning and NEQ Source: GSS 2021 4.2.2.2 Underground chambers The underground storage facility will comprise of six H.E. chambers each containing a maximum of 1,000 kg NEQ and one I.E. chamber containing a maximum of 100 kg NEQ, as illustrated inFigure 4.2. The location has been selected as a low traffic area of the WUG, with separation provided to other storage facilities. Figure 4.2: Magazine chamber layout including separation distances and proposed stored quantities’ Source: GSS 2021 Each of the seven underground chambers will be separated in order to mitigate risk of propagation between chambers. Two pathways of blast propagation underground are considered in Section 4 of the location assessment report attached as Appendix B. These scenarios and the minimum offset distance calculated are summarised inTable 4.2 below. Explosives storage facility exit I.E Chamber (up to 100,000 units or 100 kg NEQ) 6 x individual H.E Chambers (up to1,000 kg NEQ each) Explosives storage facility entry 10m

18 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Table 4.2: Offset distances Scenario Minimum offset required1 Provided separation Blast propagation by rock spall 5 m 10 m Blast Propagation by Flames and Hot Gases 10 m Major Damage Prevention to Interior of Facility 10 m 1 Calculated in accordance with Annex M of IATG 2.20 The separation distance between the chambers containing 1,000 kg of Class 1 explosive meet the calculated minimum at which blast propagation between chambers is unlikely. The minimum offsets have been calculated on the basis that the NEQ stored has a one-to-one equivalence to trinitrotoluene (TNT) in terms of energy released, when in reality many of the explosives at the facility have a lower TNT equivalence. This assumption results in higher separation requirements with a degree of conservatism. 4.2.3 Hazardous substance location for ANE 4.2.3.1 Surface storage area The ANE and gasser will be stored in 1,000 L IBCs within a dedicated compound for the oxidising substances at the SFA on the Willows Rd site. This compound will be secured from access by unauthorised personnel. ANE and gasser are incompatible and will be stored in designated sheds at a minimum distance of 8 m apart. There will be no combustible materials stored or used within 8 m of the ANE storage shed. The closest residence that is not owned by OGNZL is approximately 400 m from this storage area. Both substances will be stored in storage sheds that protect them from direct sunlight and ensure temperatures will remain under 50 degrees and below maximum temperatures associated with decomposition of the substances. Each shed will have secondary containment for at least 50% of the total storage capacity for ANE and 25% the total storage capacity for the gasser at minimum. Any damaged or leaking container will be captured in the provided secondary containment. The storage area is located in the SFA which drains to treatment as described in Section 4.9 to manage any residual contamination. The location will be certified to meet the relevant controls specified in the HSW-HS regulations as set out inTable 4.1. The compound will also be designed to provide designated areas for storage of the empty IBCs such that they are not stored together at any time, given the potential for residual material being present in both. 4.2.3.2 Underground storage area ANE and gasser will be stored underground in the WUG in three separate chambers – two for ANE and one for gasser (separated from the others by a minimum of 10 m). These chambers have been designed with consideration of legislative, safety and operational objectives, and are suitably separated as required for incompatible substances, as indicated inFigure 4.3.

19 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Figure 4.3: Direct slope distances between the different dedicated underground storage areas Source: OGNZL Each chamber will have an impervious concrete floor that drains to secondary containment. The location will be certified to meet the relevant controls specified in the HSW-HS regulations as set out in Table 4.1. Signage, a security fence with restricted access gate and safety equipment including fire extinguishers and spill kits will be provided at each store. Primary and exhaust ventilation will also be installed in each chamber. 4.3 Hazardous substances management The WNP will have strict hazardous substance management procedures in place, which are detailed in OGNZL’s indicative Hazardous Substances Principal Hazard Management Plan2 (attached as Appendix D) and include:  Development and maintenance of a hazardous substances register via the ChemAlert database. ChemAlert provides information on the substances’ identification, classification and substance specific emergency response guidance.  Substance Safety Data Sheets (SDS) are kept accessible in hardcopy to all employees on site, and training is provided in interpreting the information provided on the SDS.  Substance labelling requirements are defined to ensure appropriate identification of the substance hazards pursuant to the Hazardous Substances (Labelling) Notice 2017.  Development and maintenance of a risk register that identifies the person accountable for managing the risk and the appropriate controls.  Personal Protective Equipment will be provided to be used as a last line of defence in the hierarchy of controls.  Spill response kits are available in all work areas where hydrocarbons and other ecotoxic substances are stored or handled. Staff are trained in spill prevention and recovery.  Effective communication of hazards through daily shift safety meetings, monthly crew safety meetings, safety representative committee meetings, daily management meetings, and task observations for safety performance feedback. 2 OceanaGold, Principal Hazard Management Plan – Hazardous Substances WAI-250-PLN-003, (Waihi site, 2017) 435m 128m 405m 435m ANE store 1 ANE store 2 and gasser store Class 1 explosives storage

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