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What is MP4?
Macraes Phase 4 encompasses several proposed activities that will extend the economic life of mine to around 2030.
MP4 involves expanding some areas of the current operation, revisiting areas previously mined over the last 30 years and processing low grade ore that has been stockpiled on site. This includes expansions of the current Innes Mills, and Coronation Pits, and returning to mining at the Golden Bar Pit. This mining results in the use of some existing waste rock stacks at Coronation and Frasers and expansion of a previously rehabilitated waste rock stack at Golden Bar. Also central to the proposal it the development of Stage 2 of the Frasers Tailings Storage Facility.
A further key component of MP4 is the creation the Murphy’s Ecological Enhancement Area, a predator fenced area that will benefit the environment to offset and compensate for adverse effects on ecology that cannot be avoided, mitigated or remediated.
Except for some areas of paper road, OceanaGold owns all the land on which MP4 activities are proposed. Much of the existing and consented mining infrastructure operated by OceanaGold will be used to transport, process, store and dispose of material mined during the project.
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How will MP4 benefit your mine?
If granted, MP4 will extend the economic life of mine to around 2030.
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How will MP4 impact the region?
MP4 will allow OceanaGold to continue to remain a significant positive contributor to the Otago and New Zealand economies for many years to come.
The open pit mining, coupled with already consented underground mining through to 2032 will support our processing operations to remain viable therefore securing the jobs of over 600 OceanaGold employees and the continued employment of over 200 people employed by contractors that service the mine and many other smaller contracting companies across Otago. Wider indirect employment effects extend into hundreds more jobs again.
The mine is also an important part of the local community in which it operates, contributing significant population numbers and financial support to local schools and institutions within the Waihemo (Waitaki) and Waikouaiti Coast (Dunedin) wards.
Measures, including the creation of an ecological enhancement area, are proposed to avoid, mitigate, remediate, offset or compensate for adverse environmental effects. In addition, a proposed ecological enhancement area will support efforts to improve the Macraes natural environment and protect at risk species. The ecological enhancement area has potential to create another employment and tourism opportunity for the Waitaki District.
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What consents have already been granted for MP4?
No consents have been granted for the scope of activities included in the MP4 application that is currently being processed by the Otago Regional Council, Dunedin City Council and the Waitaki District Council. Consents were issued for consents were granted for earlier stages of MP4 such as the extension to the underground Golden Point mine and Stage one of Frasers Tailings Facility.
The Otago Regional Council is the leading agency for the application, which will be assessed using a combined process across the three councils, with input from the Department of Conservation and Heritage New Zealand. Our MP4 application was publicly notified on 22 March. People can make submissions in support, neutral or against from that date until 1 May 2025. A hearing for the application is scheduled in July.
If resource consent approval is granted, we will immediately get to work on complying with the pre-commencement conditions of consent and then implementing this phase of our open pit mining activity.
OceanaGold is now applying for resource consents for the following key activities:
- Extension of three open pits and their associated backfills and waste rock stacks
- Backfilling of the Coronation North Pit following completion of mining currently authorised
- A second stage of tailings disposal in the Frasers Tailings Storage Facility to support the open pit extensions and current consented mines
- A minor realignment of the Golden Bar Road
- Rehandling of waste rock from Northern Gully waste rock stack to Golden Point Pit
- Additional features such as topsoil stockpiles, low-grade ore stockpiles, silt ponds, areas for pit infrastructure and access roading
- Activities associated with the mitigation, remediation and offsetting of the effects of the above activities
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What are tailings?
Tailings are the fine sand and silt, mixed with water and traces of chemical reagents, produced as byproduct from our gold processing plant. Seepage from tailings tends to contain higher levels of sulphate which is a natural ingredient within in the schist rocks that we mine. Tailings are pumped from the processing plant into a Tailings Storage Facility (TSF), and the water decants to the surface as the sediment settles out over time. The decant pond is the water you can see sitting on the surface of the tailings facilities. The water is recirculated back to the processing plant for reuse (and over 90% of water used at Macraes is recycled). It takes many years for tailings to consolidate and stabilise as the moisture content reduces, and therefore our tailings dams are designed to ensure that tailings do not escape even if they liquefy during an extreme earthquake.
Managing the environmental effects and safety risks of tailings storage is extremely high priority for OceanaGold. Our TSFs are designed and operated in alignment with the NZ Building code, NZSOLD dam safety guidelines, and the Global Industry Standard on Tailings Management (GISTM).
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How will you manage environmental effects of tailings produced at your mine?
OceanaGold has consent to discharge and store tailings in the mined-out Frasers Pit.
Numerical modelling completed by specialist groundwater consultants as part of our assessment of environmental effects shows that groundwater (and any contaminants) flow inward towards Frasers Pit and underground mine. This is because the pit water level is lower than the pre-mining groundwater level and the mining void acts as a sink, drawing groundwater towards it. Therefore, contaminants from Frasers TSF are contained within the vicinity of the pit. The tight and dense nature of the in-situ schist rock mass surrounding the pit and underground mine mean that seepage travels extremely slowly through the rock, particularly at greater depth.
