FAQs

Macraes Phase Four (MP4) encompasses several proposed activities that will keep OceanaGold’s Macraes Mine operating until the late 2030s. 

The MP4 Project is not a new mine. It builds on what is already at Macraes, expanding some areas of the current operation, revisiting areas previously mined over the past 36 years and processing previously uneconomic low grade ore that has been stockpiled on site. 

MP4 sustains more than 760 direct jobs and thousands of indirect jobs across Otago and Waitaki, for at least another decade. OceanaGold owns the land where the mine is located, except for roads which it manages in conjunction with the councils.

Macraes has been part of Otago for over three decades. MP4 is about continuing that contribution, not starting something new. 

Approval of MP4 is being sought under the Fast Track Approvals Act. This process is led by an independent expert panel working under a framework that retains environmental, social and cultural safeguards and a focus on operational best practise. 

Macraes is the largest gold mine in New Zealand. It has produced more than 6 million ounces since 1990. MP4 sustains this operation, and a major regional employer, for almost a decade longer. It delivers significant regional and national economic benefits. 

• Investment. MP4 brings around $3.1 billion NZD of additional spending in New Zealand over the life of the project, well above the $100 million NZD the Overseas Investment régime treats as a significant investment. 
• Exports. The project adds between $4.5 billion NZD (at our base case gold price) and $7.3 billion (upside) of gold exports, an average of $320 to $520 million NZD a year. This sustains Macraes’ export contribution to the end of the 2030s rather than ending it around 2030. An average of $320 to $520 million a year is equivalent to between 10 – 15% of the Government’s Minerals Strategy goal of $3 billion NZD in annual mineral exports. 
• Employment. The mine directly employs over 760 people, and supports around 2,600 jobs in total across New Zealand once suppliers, contractors and the spending of those workers are counted. The jobs are well paid, over $100,000 NZD a year on average compared to around $80,000 NZD in Otago and nationally, and the workforce lives mostly in Dunedin and Waitaki, so about half of the jobs are in Otago. Without MP4 this employment winds down from around 2030. MP4 sustains it almost a decade longer. 
• Economic activity. MP4 is associated with around $3.1 billion NZD of expenditure in New Zealand over the project, on wages, suppliers and capital. About $1.0 billion NZD of this, a third, is spent in the Otago region. Including the flow-on effects through suppliers and household spending, the project supports around $6.1 billion NZD of economic activity, equivalent to 5 to 6% of the Waitaki District economy each year. 
• Crown revenue. The project returns between $0.5 billion NZD (base case) and $1.4 billion NZD (upside) to the Crown over its life, in royalties, company income tax and PAYE. 
• The project takes changing gold price into account MP4 breaks even at a gold price of about US$2,050 an ounce. That is less than half the current market price of US$4,191, and below both our base case (US$2,450) and the upside (US$4,000). The project pays for itself, including the cost of new development, at prices well below where gold trades today. 

Open pit extensions 

• Innes Mills Pit: Extended to the north, east, and west, increasing the pit footprint by approximately 49 ha. This requires relocating all SP11 and SP10 tailings and removing up to 30 m off the top of the MTI tailings, realigning Macraes Road over the Frasers TSF embankment, and relocating the Open Pit Workshop. 
• Coronation and Coronation North Pits: Currently used as water storage reservoirs, these will be dewatered and mined. Coronation extends approximately 560 m to the southeast, increasing the footprint by around 40 ha (47%). Coronation North extends approximately 205 m to the southeast, increasing the footprint by around 17 ha (43%), and includes development of the Trimbells waste rock stack. 
• Golden Bar Pit: A previously mined and partially rehabilitated pit, last worked 2004 – 2006. Proposed extension of approximately 15.2 ha to the east and northeast — more than doubling the existing 14 ha footprint. The pit lake will be pumped out before mining recommences. 

Underground mine extension 

• Golden Point Underground (GPUG): An existing underground mine accessed via two portals on the eastern wall of Golden Point Pit, about 700 m from the processing plant. MP4 proposes a further eastward extension using the same drill-and-blast method currently in use, with workings reaching depths of up to 130 m below sea level in the outer envelope. 

Tailings storage 

• Construction of Frasers TSF Stage 3, raising the embankment from 480 m to 520 m above sea level to accommodate all MP4 tailings, plus the relocation of tailings from MTI, SP10, and SP11. 

Supporting activities at all sites 

• Wildlife monitoring, salvage, and translocation before any clearance 
• Waste rock haulage to existing stacks 
• Ore haulage to the processing plant 
• Road realignment and infrastructure upgrades 
• Rehabilitation and closure progressively throughout mining 

The mitigation measures included in the MP4 project scope focus on offsetting and managing environmental impacts through several initiatives: 

• Murphys Ecological Enhancement Area (MEEA): Establishing an ecological reserve near Murphys Creek to compensate for residual effects on terrestrial and aquatic ecology. This includes building an all-weather access track, predator-proof fencing, maintenance tracks, and facilities like a site office and equipment sheds. 
• Other Ecological Enhancements: Additional projects outside the MEEA may be undertaken to meet offset targets or compensatory requirements, requiring mapping and management plans for consent. 

Overall, these measures aim to avoid, remedy, and mitigate adverse effects while ensuring ecological improvements and water quality management. 

We monitor water quality at 16 sites across the three catchments, including upstream control sites not affected by mining (which allow us to separate natural variation from mining effects), and downstream compliance sites where results are formally assessed. 

Shag/​Waihemo Catchment

Deepdell Creek, Battery Creek, Highlay Creek, and the Shag River at Loop Road and McCormicks are monitored. The Shag River sites are used as drinking water sources and receive additional protections under the New Zealand Drinking Water Standards 2022. 

Arsenic concentrations in Deepdell Creek and Battery Creek are naturally elevated due to mineralised geology that pre-dates any mining. Pre-mining data confirm this is a background condition, not a result of operations. 

MP4 includes improved source control, capture and treatment appropriate to ensure water quality in this catchment.

Waikouaiti River Catchment

Murphys Creek, Golden Bar Creek, and the North Branch Waikouaiti River are monitored. Sulphate concentrations at Murphys Creek have historically been elevated. MP4 includes improved source control, capture and treatment approaches to improve this trend.

Taieri River Catchment 

Mare Burn, monitored at an upstream control site and two downstream impact sites, is where elevated zinc and nitrate have been observed in recent years, alongside a decline in some stream invertebrate communities. MP4 includes improved source control, capture and treatment approaches to improve this trend.

Water quality is measured monthly at all compliance sites. Results are compared against scientifically derived trigger values adjusted for the local water chemistry at each site. If a result exceeds a trigger value, it signals a need for further investigation. If exceedances occur too frequently, the site is declared non-compliant and management action is required. 

Crucially, where the same elevated conditions are observed at upstream control sites at the same time, these are not counted as mine-related exceedances. This ensures natural events such as rainfall are distinguished from mining effects. 

Drinking water sites

At NB03, Shag at Loop Road, and Shag at McCormicks, drinking water standards apply. A single exceedance of a drinking water value constitutes non-compliance — the most precautionary standard in the entire framework, with no allowance for upstream comparison. 

Continuous early warning

We intend to progressively install continuous electrical conductivity monitors at key discharge points. This enables us to detect changes in water quality at the source before they reach a river, allowing faster operational response. 

Water quality is one of the most closely monitored parts of the Macraes operation. 

We carry out comprehensive monitoring across the catchment, overseen by the Otago Regional Council (ORC), and all of our monitoring data is available through the ORC. 

Water affected by mining activities will be captured, managed and treated before it’s released. Clean water is diverted around operational areas wherever practical. 

We committed to investing in water treatment technology, including ongoing pilot testing to improve outcomes over time. 

When ore is processed to extract gold, the remaining finely ground rock — known as tailings — must be stored safely. OceanaGold currently operates four tailings storage facilities (TSFs) at the Macraes Operation. Two older facilities (Mixed Tailings Impoundment (MTI) and Southern Pit 11 (SP11A) are now resting impoundments. The Frasers Tailings Storage Facility (FTSF) and Top Tiperary Tailings Storage Facility (TTTSF) are the only current active facilities. 

The FTSF makes use of the mined-out void of the old Frasers Open Pit. Tailings are pumped in as a slurry and settle over time, with water returned to the gold mining process. Containment is provided by the Frasers Backfill (FRBF) — a wide engineered embankment built from mine waste rock positioned between Frasers Pit and the adjacent Innes Mills Pit. 

Safety for members of the public and our staff is always our number one priority. Macraes’ TSFs are carefully engineered rock structures that are designed in accordance with national and international standards to safely withstand significant seismic and weather events. 

The construction and monitoring of all our TSFs is sound. We use a multi-layered and alarmed system that tracks ground movement. This system includes two ground-based radar units, automated and manual survey monitoring and GNSS positional sensors. InSAR satellite monitoring allows us to track the extents and rate of very slow movements. We also physically walk and check our TSFs on a regular basis.

Stages 1 and 2 of the Frasers Tailings Storage Facility (FTSF) have already been consented and are under construction. Stage 3 is proposed as part of the MP4 application to provide additional storage capacity for the extended mine life. The key elements are described below. 

Raising the Frasers Backfill Embankment 

Stage 3 involves raising the FRBF embankment from its current Stage 2 level of approximately 480 mRL (metres relative to sea level) up to approximately 520 mRL. As Innes Mills mining extends northward, the embankment’s downstream shoulder will be further buttressed by waste rock, providing exceptional structural stability. 

Storing Tailings from MP4 and Older Facilities 

Stage 3 is designed to store all tailings generated by MP4 mining and processing through to the late 2030s, as well as tailings hydraulically relocated from the older SP11A and MTI facilities as those are decommissioned. The total tailings storage requirement for FTSF is approximately 153 million tonnes. 

Our TSFs at Macraes are carefully engineered to control seepage and are constructed to national and international standards to ensure long-term safety and stability. Their design meets New Zealand’s highest dam safety standards. 

Tailings are pumped into the facility in controlled layers, where solids settle, and the water is returned to our processing plant for reuse. This reduces the amount of water retained within the TSF and further limits the potential for seepage. 

There is also very limited geological connection between our TSFs and underground mine workings due to the thick zones of low‑permeability, intact schist rock that surrounds the facilities. This rock mass greatly slows the movement of water, and groundwater modelling shows contaminants remain contained. 

To ensure ongoing environmental protection, our environmental team monitors water quality at more than 130 sites every month, including sites around all TSFs. We also comply with consented water quality limits and maintain regular reporting to council and independent experts. 

FTSF Stage 3 has been assessed as High Potential Impact Classification (High PIC) — New Zealand’s most stringent dam safety category. In practice, this means: 

• The facility must withstand a Probable Maximum Flood — the largest flood event theoretically possible at the site — without overtopping 
• The design must account for the worst credible earthquake scenario without any uncontrolled release of tailings or water 
• An independent peer reviewer with High PIC dam experience must review all designs before a Building Consent is granted 
• The dam safety classification must be formally reassessed every five years during operation 

There is limited connection between FTSF and the Frasers Underground Mine. 

Frasers underground was mined at a depth of around 700 to 800m beneath Top Tipperary TSF (TTTSF). There is a thick zone of low permeability intact rock between these two facilities. The tight and dense nature of the in-situ schist rock mass surrounding the pit and underground mine means that seepage travels extremely slowly through the rock, particularly at depth. More importantly, groundwater modelling as part of our assessment of environmental effects shows that contaminants will be contained within the pit. 

As part of our consents, we continue to monitor water quality in surrounding surface water and comply with specified limits. 

Closure planning is built into the design from the outset. The base-case closure concept is a dry closure — the tailings surface will be capped and graded so that rainwater drains off rather than ponding, and the area eventually revegetates. 

If mining were to stop earlier than planned, two alternative scenarios are possible: an ephemeral (seasonal) lake at intermediate tailings levels, or a permanent pit lake if tailings levels are lower. Both have been assessed, and management measures including interim dust control and drainage channels have been identified for each. 

To facilitate the proposed extension of Innes Mills Pit, Golden Bar Road and Macraes Road will need to be realigned. The Macraes Road will be realigned in two stages. The first stage will be required to make way for the IM12 expansion, this diversion will involve relocating Macraes Road to the east of the bridge by approximately 160 m to the north. The second stage will be required to make way for the IM13 expansion and will include a total diversion of the road to the south over the FTSF embankment. 

Macraes Road is realigned in two stages as MP4 progress. The first re-alignment is a small northern one and would occur about 2028. The final re-alignment (about 2031) is over the Frasers embankment once completed. This alignment has the road moved south a few hundred metres from its current alignment. 

Yes. We continuously explore within our existing landholdings and the wider Macraes region to better understand the geology and identify opportunities that may support the long‑term future of the operation. Exploration is a routine part of responsible mining and helps ensure we can plan effectively, make informed decisions, and provide ongoing economic benefits to the region. 

Any potential future projects identified through exploration would be subject to detailed assessment, community engagement, and the appropriate regulatory approval processes before proceeding. 

OceanaGold is legally required to leave the site in a safe, stable, and self-sustaining condition and that includes meeting water quality limits at all times before and after closure. Closure isn’t just about stopping work — it involves years of active rehabilitation, water management, and ecological care that will continue long after the last gold is poured. 

Reshaping the land 

Waste rock piles will be contoured, capped, and revegetated with tussock grassland and pasture. The aim is to create stable landforms that shed water rather than absorb it, reducing contaminated seepage over time. Exposed slopes will be grassed and planted as work progresses — rehabilitation happens progressively throughout mining, not just at the end. 

Open pits will not all be filled in. Most will gradually fill with rainfall and groundwater to form pit lakes. These lakes will become permanent features of the post-mining landscape — similar in some ways to the existing ponds and water bodies already visible from Macraes Road today. 

Macraes Road 

Macraes Road currently runs through the active mine area. As part of closure, a new alignment of the road will be established across the top of the Frasers Tailings Storage Facility embankment, routing it roughly back to where it sat before mining. This is one of the more visible physical legacies of the project for the community. 

Waterways 

One of the more significant closure outcomes is the restoration of the North Branch of the Waikouaiti River headwaters, which are currently disconnected from the lower catchment due to mining. Before closure, the stream will be re-established across the Frasers embankment with native riparian planting along its banks, reconnecting the headwaters with the lower river for the first time in decades. 

Riparian planting along Murphys Creek will also be carried out as part of closure. 

Water quality after closure 

Water management is one of the most complex and long-running closure obligations. Old mine pits fill slowly with water and eventually overflow — that process takes decades (up to 70 years). Before any pit lake overflows into a stream, the water will be chemically treated to reduce arsenic and metal concentrations. 

Seepage from waste rock piles will be captured and treated for as long as necessary. The water treatment plant will keep operating after mining stops — it doesn’t just get switched off at closure. Modelling shows that seepage levels and contaminant loads are expected to reduce significantly over time as waste rock is capped and rehabilitated. 

Financial security 

OceanaGold has operated a rehabilitation bond since mining began in 1990. This security is held by the regional and district councils — not OceanaGold — and can be drawn on immediately if OceanaGold were ever to walk away without completing its closure obligations. The bond is reviewed and updated every year to reflect the current state of the site and works still to be done. 

In addition to the rehabilitation bond, a separate capitalisation bond will be established to fund the long-term management of the site after closure. This is money set aside specifically for ongoing monitoring, water treatment, maintenance, and ecological management — the things that need to carry on for years or decades after active mining has stopped. 

The post-closure trust 

Before the mine closes, OceanaGold must establish a dedicated charitable trust to take on long-term responsibility for the site. Key features: 

• Kā Rūnaka appoint a majority of trustees — giving local Ngāi Tahu rūnaka direct governance over what happens to the land after closure 
• The relevant councils appoint a minority of trustees 
• The trust takes ownership of the post-closure land through a land-holding company 
• It is funded through the capitalisation bond to carry out monitoring, maintenance, and water management in perpetuity 
• It is designed to outlast OceanaGold if necessary — the trust structure doesn’t depend on the company continuing to exist 

The water treatment plant must be in working order when it is transferred to the trust. 

The visual outcome 

Landscape assessors predict that at closure, with landforms contoured, pit lakes formed, and tussock and riparian plantings established, the site will read as low to low-moderate adverse compared with the pre-mining landscape — not invisible, but integrated. Some areas, particularly where headwater streams are re-established and native planting takes hold, are expected to show a net improvement in natural character compared to current conditions. 

OceanaGold has operated at Macraes for over 36 years, and we take our responsibility to keep the air safe seriously — for people who live and work near the mine, and for the wider environment. We monitor air quality continuously, we act on complaints, and we apply controls every day to minimise dust. As part of our Macraes Phase Four application, we commissioned an independent air quality assessment to confirm that extending mining will not change that picture. 

Robust monitoring will continue throughout MP4 and will be updated to reflect best practice. The key elements of the proposed monitoring programme are: 

OceanaGold operates 16 dust deposition monitoring sites and continuous total suspended particulate (TSP) monitoring in Macraes village. 

Dust monitoring has generally met consent limits at all sites beyond the mine boundary since 2015 and dust levels have trended downward over the past decade, with no confirmed dust events from mining recorded by the Macraes village dust monitor. 

While the scale of activity means dust emissions from haul roads and material handling are large at the source, three factors combine to make off-site impacts negligible: 

• Distance: All sensitive receptors are more than 600 m from any mining activity, and most are over 1 km away. Independent research shows that PM₁₀ concentrations from mining activities typically reduce to negligible levels beyond 250 – 350 m from the source. 
• Wind direction: Strong, dry winds toward community receptor locations occur less than 1 – 2.5% of the time, depending on location. Macraes township sits to the southwest — the opposite direction to the prevailing wind pattern. 
• Dust controls: OceanaGold’s dust management measures — particularly water suppression on haul roads — are effective and will continue throughout MP4.