THE WHAREKIRAUPONGA UNDERGROUND MINE
The proposed Wharekirauponga Underground Mine is located north of Waihi, beneath Forest Park administered by the Department of Conservation (DOC).
This mine would be accessed via an underground tunnel from company land on Willows Road, outside the Forest Park, allowing us to minimise our surface impacts.
A connecting transport tunnel back to our existing Processing Plant allows us to transport materials in and out of the Wharekirauponga area without vehicles on public surface roads.
This mine would be accessed via an underground tunnel from company land on Willows Road, outside the Forest Park, allowing us to minimise our surface impacts.
A connecting transport tunnel back to our existing Processing Plant allows us to transport materials in and out of the Wharekirauponga area without vehicles on public surface roads.
We recognise the significance and sensitivity of the Wharekirauponga area and its ecology, which is an important recreational area, and home to several native and endemic species. That’s why any potential mining operation we may undertake within the Forest Park would only be underground – not at the surface level.
The Wharekirauponga Underground Mine consists of four sub-components:
The Wharekirauponga Underground Mine consists of four sub-components:
- Access Tunnels to the orebody – We are proposing an approximately 7 km access tunnel that extends from a portal on Company land at the end of Willows Road, Waihi, to the base of the Wharekirauponga resource.
- Ventilation Raises – These are required for air circulation and as an emergency exit from the orebody tunnel. The current tunnel proposal would require a total of four ventilation raises close to the mining area. Suitable locations are currently being investigated.
- Willows Road Surface Infrastructure – To facilitate the construction and operation of the Wharekirauponga mine, some surface infrastructure will need to be constructed at the Willows Road location.
- A 4.8 km Tunnel to the Waihi Processing Plant – To allow for access between the orebody and our existing processing facilities in Waihi.
ACCESS TUNNELS
These tunnels would be developed using a similar drilling and blasting method, similar to how we develop drives in our current underground mining operations at Waihi.
Rock extracted through the tunnelling process would be loaded into trucks and then hauled to a temporary surface stockpile at Willows Road. As mining progresses, this rock would be returned into the Wharekirauponga Underground Mine for backfilling purposes.
OREBODY ACCESS TUNNEL
We are proposing an approximately 7 km access tunnel that extends from a portal on company land at the end of Willows Road, Waihi, to the base of the Wharekirauponga resource.
The majority of this tunnel would be constructed as a ‘dual decline’. A dual decline tunnel consists of two tunnels running in parallel, with short connections between the two created every few hundred metres. Bulkheads are also installed on these connections, providing the ability to seal one tunnel from another as needed for air flow management purposes, or in the unlikely event of an emergency situation. This design provides a high level of airflow throughout the mine and minimises the number of surface ventilation raises.
Tunnelling would begin at the Willows Road land and continue until the orebody at Wharekirauponga
is reached. Upon reaching the orebody, development drives would be undertaken to allow mining to commence.
These development drives would be similar to the drives that have been successfully constructed for the existing underground operations in Waihi.
INTERCONNECTING TRANSPORT TUNNEL
A single 4.8 km long tunnel would be constructed from the Willows Road land to the Waihi Processing Plant, linking to the dual decline tunnel system underground.
This will be used to transport ore from the underground mine to the Waihi Processing Plant once mining begins. The tunnel could also provide general operational access between the Wharekirauponga Underground Mine and the Waihi Processing Plant.
Rock extracted through the tunnelling process would be loaded into trucks and then hauled to a temporary surface stockpile at Willows Road. As mining progresses, this rock would be returned into the Wharekirauponga Underground Mine for backfilling purposes.
OREBODY ACCESS TUNNEL
We are proposing an approximately 7 km access tunnel that extends from a portal on company land at the end of Willows Road, Waihi, to the base of the Wharekirauponga resource.
The majority of this tunnel would be constructed as a ‘dual decline’. A dual decline tunnel consists of two tunnels running in parallel, with short connections between the two created every few hundred metres. Bulkheads are also installed on these connections, providing the ability to seal one tunnel from another as needed for air flow management purposes, or in the unlikely event of an emergency situation. This design provides a high level of airflow throughout the mine and minimises the number of surface ventilation raises.
Tunnelling would begin at the Willows Road land and continue until the orebody at Wharekirauponga
is reached. Upon reaching the orebody, development drives would be undertaken to allow mining to commence.
These development drives would be similar to the drives that have been successfully constructed for the existing underground operations in Waihi.
INTERCONNECTING TRANSPORT TUNNEL
A single 4.8 km long tunnel would be constructed from the Willows Road land to the Waihi Processing Plant, linking to the dual decline tunnel system underground.
This will be used to transport ore from the underground mine to the Waihi Processing Plant once mining begins. The tunnel could also provide general operational access between the Wharekirauponga Underground Mine and the Waihi Processing Plant.
HOURS OF OPERATION
OceanaGold Waihi is proposing that the Wharekirauponga Underground Mine would operate 24 hours a day, seven days a week.
OceanaGold Waihi is proposing that the Wharekirauponga Underground Mine would operate 24 hours a day, seven days a week.
EFFECTS
NOISE
If the Waihi North Project is approved, we will be required to manage our activities so that we comply with strict noise limits set through the regulatory approvals process.
There are a range of noise management measures that may be implemented to meet these requirements, including:
BLASTING AND VIBRATION
A key consideration for OceanaGold Waihi in developing the proposed Waihi North Project is any potential amenity effects our operations may have on residents.
WILLOWS ROAD PORTAL
Due to the location and direction of the dual decline tunnel system to the orebody, residents close to the Willows Road portal are unlikely to experience any reduction in amenity due to vibration from its development.
INTERCONNECTING TRANSPORT TUNNEL
Any associated amenity effects on property in relation to the tunnel would be temporary and localised during the development stage. Once the tunnel is completed there would be no appreciable ongoing effects to amenity.
AIR QUALITY
If the Waihi North Project is approved, we will be required to comply with consent conditions for air quality set through the regulatory approvals process. This will require OceanaGold Waihi to produce an Air Quality Management Plan.
There are a range of air quality management measures that may be implemented to meet the requirements of consent conditions, including:
GROUND SETTLEMENT
By utilising proven mining techniques, we will protect from the negative impacts of surface settlement both at the mine and along the tunnel route. Mining of the orebody will occur entirely from the underground tunnel utilising the same proven methods we currently employ for our Correnso and Martha underground projects. Voids that may cause instability will be backfilled with rock as we progress.
DEWATERING
OceanaGold Waihi expects to encounter water inflows during the operation of the mine. Water inflows, together with any water used in the mining process would be pumped to the existing OceanaGold Waihi Water Treatment Plant for treatment if not suitable for onsite discharge. Boreholes would be drilled ahead of workings to detect water bearing structures and appropriate mitigation applied to avoid any surface impacts.
If the Waihi North Project is approved, we will be required to manage our activities so that we comply with strict noise limits set through the regulatory approvals process.
There are a range of noise management measures that may be implemented to meet these requirements, including:
- Equipment selection and maintenance.
- Limiting some activities to certain times of the day.
- Noise bunding.
- Acoustic cladding around potentially noisy machinery.
BLASTING AND VIBRATION
A key consideration for OceanaGold Waihi in developing the proposed Waihi North Project is any potential amenity effects our operations may have on residents.
WILLOWS ROAD PORTAL
Due to the location and direction of the dual decline tunnel system to the orebody, residents close to the Willows Road portal are unlikely to experience any reduction in amenity due to vibration from its development.
INTERCONNECTING TRANSPORT TUNNEL
Any associated amenity effects on property in relation to the tunnel would be temporary and localised during the development stage. Once the tunnel is completed there would be no appreciable ongoing effects to amenity.
AIR QUALITY
If the Waihi North Project is approved, we will be required to comply with consent conditions for air quality set through the regulatory approvals process. This will require OceanaGold Waihi to produce an Air Quality Management Plan.
There are a range of air quality management measures that may be implemented to meet the requirements of consent conditions, including:
- Applying dust suppression methods.
- Keeping stockpiles low so wind is less likely to spread dust.
- Planting pasture, shrubs, and trees as soon as rehabilitation areas are available.
- Washing vehicles before leaving site to travel on public roads.
GROUND SETTLEMENT
By utilising proven mining techniques, we will protect from the negative impacts of surface settlement both at the mine and along the tunnel route. Mining of the orebody will occur entirely from the underground tunnel utilising the same proven methods we currently employ for our Correnso and Martha underground projects. Voids that may cause instability will be backfilled with rock as we progress.
DEWATERING
OceanaGold Waihi expects to encounter water inflows during the operation of the mine. Water inflows, together with any water used in the mining process would be pumped to the existing OceanaGold Waihi Water Treatment Plant for treatment if not suitable for onsite discharge. Boreholes would be drilled ahead of workings to detect water bearing structures and appropriate mitigation applied to avoid any surface impacts.
VENTILATION RAISES
Ventilation raises, providing fresh air supply to the Wharekirauponga Underground Mine, would be required to supply sufficient air for a safe working environment and as emergency exits.
Based on the current design, we are proposing to construct up to five ventilation raises. Four of these would be within the Forest Park area, either on Forest Park administered by the Department of Conservation, or on unformed Hauraki District Council road reserve. The fifth would be located on company land near the tunnel portal.
OceanaGold Waihi is proposing that stringent ecological conditions be applied to ensure that sites are appropriately selected to minimise adverse effects on ecological and landscape values.
We will ensure minimal disruption and carry out detailed technical studies before we embark on any shaft construction. Studies are ongoing to ensure that the vent locations have minimal effect on the environment and are placed to avoid areas of high value habitat.
A drilling platform would be established on the preferred site and exploration, geotechnical, and hydrogeological drilling and analysis would be undertaken.
These raises would be temporary structures in place for the life of the mine and would be fully rehabilitated upon completion of mining. The construction of the ventilation raises would occur from the surface via helicopter support. The initial construction footprint would be up to 900 square metres.
A vent stack would be established at the top of each ventilation raise. These would be installed by helicopter and remain in place for the duration of the project.
Once constructed, and following progressive rehab, the operational surface footprint of each vent stack would reduce to no greater than 12 m x 12 m. The surrounding disturbed area would begin rehabilitation as soon as construction was completed.
Based on the current design, we are proposing to construct up to five ventilation raises. Four of these would be within the Forest Park area, either on Forest Park administered by the Department of Conservation, or on unformed Hauraki District Council road reserve. The fifth would be located on company land near the tunnel portal.
OceanaGold Waihi is proposing that stringent ecological conditions be applied to ensure that sites are appropriately selected to minimise adverse effects on ecological and landscape values.
We will ensure minimal disruption and carry out detailed technical studies before we embark on any shaft construction. Studies are ongoing to ensure that the vent locations have minimal effect on the environment and are placed to avoid areas of high value habitat.
A drilling platform would be established on the preferred site and exploration, geotechnical, and hydrogeological drilling and analysis would be undertaken.
These raises would be temporary structures in place for the life of the mine and would be fully rehabilitated upon completion of mining. The construction of the ventilation raises would occur from the surface via helicopter support. The initial construction footprint would be up to 900 square metres.
A vent stack would be established at the top of each ventilation raise. These would be installed by helicopter and remain in place for the duration of the project.
Once constructed, and following progressive rehab, the operational surface footprint of each vent stack would reduce to no greater than 12 m x 12 m. The surrounding disturbed area would begin rehabilitation as soon as construction was completed.
WILLOWS ROAD SURFACE INFRASTRUCTURE
To facilitate the construction of the tunnels and operation of the Wharekirauponga underground mine, some surface infrastructure would need to be constructed at the Willows Road property.
SITE ACCESS ROADS
A sealed private road from the northern end of Willows Road onto the site would need to be constructed. A haul road would be established from the portal to the rock stockpile, with a connection to a workshop and a wash pad.
SITE SERVICES
Site services, such as power, fibre optic cable, and potable water would be brought to the site from the existing OceanaGold Waihi Processing Plant via a buried trench. Where required, this trench would also be used to transport water back to the existing OceanaGold Waihi Water Treatment Plant.
An office and changing rooms would be established. These would be comprised of modular, temporary style buildings.
Power and water connections would also need to be arranged, and a sewage system installed.
OFFICE AND CHANGE HOUSE
At the site of the portal, an office and changing rooms would be established. These would be comprised of modular, temporary style buildings with an approximate footprint of 250 square metres. Power and water connections would
also need to be arranged, and a sewage system installed.
SERVICE WORKSHOP AND REFUELLING
The workshop would include a sealed undercover area. Re-fuelling would be undertaken via a dedicated fuelling station until the tunnel had progressed, at which point an appropriately certified tank would be installed underground.
ROCK STORAGE
Rock extracted through the tunnelling process would be stockpiled in the tunnel, loaded into trucks, and then hauled to a surface stockpile. A single stockpile of approximately 7 ha would be required to temporarily store the rock. Stockpile contact water would be collected in a pond and pumped back to the existing Waihi Water Treatment Plant for treatment if not suitable for discharge on site.
All rock from the tunnelling stockpile will be progressively returned underground to backfill mined voids approximately thirteen years after commencement of first site works. Once the Willows Road rock stockpile is exhausted, the site will be rehabilitated and further rock for backfilling voids will be obtained from the NRS, and transported using the interconnecting tunnel from the existing Processing Plant.
EXPLOSIVES MAGAZINES
Explosives magazines that conform to New Zealand hazardous substances regulations would be located on site, south of the rock stack on company land. The explosives magazines would be locked and securely fenced, with access strictly controlled.
PORTAL
A portal on company land north of the end of Willows Road in Waihi would form the entrance to the access tunnel. A second portal would also need to be established at the existing Waihi Processing Plant to provide access to the connecting Transport Tunnel. Earthworks would be undertaken to form these portals. Appropriate earthmoving equipment would be utilised and, if necessary, blasting would be used.
Other service infrastructure would then be installed at each portal including temporary ventilation fans, water storage tanks, transformers, lighting, and safety tag boards.
LIGHTING
To allow us to operate outside of daylight hours, lighting will need to be established at various locations.
The lighting will be designed and located so that light spill is minimised to protect the amenity of nearby residents.
NOISE
If the Waihi North Project is approved, we will be required to manage our activities so that we comply with strict noise limits set through the regulatory approvals process.
There is a range of noise management measures that may be implemented to meet these requirements, including:
AIR QUALITY
If the Waihi North Project is approved, we will be required to comply with consent conditions for air quality set through the regulatory approvals process. This will require OceanaGold Waihi to produce an Air Quality Management Plan.
There are a range of air quality management measures that may be implemented to meet these requirements, including:
PROPERTY DAMAGE
Consent conditions for vibration from the development of the transport tunnel will be set well below the level where property damage could occur. We know from the community that there can be concern around what we would do if mine-related activity caused property damage.
In recognition of this, we have a procedure in place to assist owners if they believe their property may have been damaged. If it is determined that property damage is attributable to our activities, we will remedy the damage at our cost. Our experience in Waihi with our Correnso and Martha Underground mines shows that this approach provides assurance to property owners on land above any underground infrastructure.
SITE ACCESS ROADS
A sealed private road from the northern end of Willows Road onto the site would need to be constructed. A haul road would be established from the portal to the rock stockpile, with a connection to a workshop and a wash pad.
SITE SERVICES
Site services, such as power, fibre optic cable, and potable water would be brought to the site from the existing OceanaGold Waihi Processing Plant via a buried trench. Where required, this trench would also be used to transport water back to the existing OceanaGold Waihi Water Treatment Plant.
An office and changing rooms would be established. These would be comprised of modular, temporary style buildings.
Power and water connections would also need to be arranged, and a sewage system installed.
OFFICE AND CHANGE HOUSE
At the site of the portal, an office and changing rooms would be established. These would be comprised of modular, temporary style buildings with an approximate footprint of 250 square metres. Power and water connections would
also need to be arranged, and a sewage system installed.
SERVICE WORKSHOP AND REFUELLING
The workshop would include a sealed undercover area. Re-fuelling would be undertaken via a dedicated fuelling station until the tunnel had progressed, at which point an appropriately certified tank would be installed underground.
ROCK STORAGE
Rock extracted through the tunnelling process would be stockpiled in the tunnel, loaded into trucks, and then hauled to a surface stockpile. A single stockpile of approximately 7 ha would be required to temporarily store the rock. Stockpile contact water would be collected in a pond and pumped back to the existing Waihi Water Treatment Plant for treatment if not suitable for discharge on site.
All rock from the tunnelling stockpile will be progressively returned underground to backfill mined voids approximately thirteen years after commencement of first site works. Once the Willows Road rock stockpile is exhausted, the site will be rehabilitated and further rock for backfilling voids will be obtained from the NRS, and transported using the interconnecting tunnel from the existing Processing Plant.
EXPLOSIVES MAGAZINES
Explosives magazines that conform to New Zealand hazardous substances regulations would be located on site, south of the rock stack on company land. The explosives magazines would be locked and securely fenced, with access strictly controlled.
PORTAL
A portal on company land north of the end of Willows Road in Waihi would form the entrance to the access tunnel. A second portal would also need to be established at the existing Waihi Processing Plant to provide access to the connecting Transport Tunnel. Earthworks would be undertaken to form these portals. Appropriate earthmoving equipment would be utilised and, if necessary, blasting would be used.
Other service infrastructure would then be installed at each portal including temporary ventilation fans, water storage tanks, transformers, lighting, and safety tag boards.
LIGHTING
To allow us to operate outside of daylight hours, lighting will need to be established at various locations.
The lighting will be designed and located so that light spill is minimised to protect the amenity of nearby residents.
NOISE
If the Waihi North Project is approved, we will be required to manage our activities so that we comply with strict noise limits set through the regulatory approvals process.
There is a range of noise management measures that may be implemented to meet these requirements, including:
- Equipment selection and maintenance.
- Construction and vegetation of noise bunds.
- Limiting the height of stockpiles.
- Acoustic cladding around potentially noisy machinery.
- Closed-board fencing.
- Acoustic noise wall on some sections of perimeter noise bund.
AIR QUALITY
If the Waihi North Project is approved, we will be required to comply with consent conditions for air quality set through the regulatory approvals process. This will require OceanaGold Waihi to produce an Air Quality Management Plan.
There are a range of air quality management measures that may be implemented to meet these requirements, including:
- Watering haul roads and using sprinkler systems and water sprays where required.
- Dust collectors and filters on machinery.
- Keeping stockpiles low, so the wind is less likely to spread dust.
- Planting grass to cover long-term stockpiles.
- Planting pasture, shrubs, and trees as soon as rehabilitation areas are available.
- Washing vehicles before leaving the site to travel on public roads.
PROPERTY DAMAGE
Consent conditions for vibration from the development of the transport tunnel will be set well below the level where property damage could occur. We know from the community that there can be concern around what we would do if mine-related activity caused property damage.
In recognition of this, we have a procedure in place to assist owners if they believe their property may have been damaged. If it is determined that property damage is attributable to our activities, we will remedy the damage at our cost. Our experience in Waihi with our Correnso and Martha Underground mines shows that this approach provides assurance to property owners on land above any underground infrastructure.
ENVIRONMENTAL NET GAIN AND BIODIVERSITY
A key project commitment is to initiate and sustain an environmental net gain throughout the life of the project such that the immediate area and environment is left in an improved state from an ecological perspective than had the project not taken place. At the Willows Road infrastructure area, we plan to:
- Protect natural environmental and ecological assets identified on the land as part of the independent ecological surveys and assessments undertaken.
- Develop alternate and enhanced water courses where diversions are necessary to establish site infrastructure. This will include riparian zone establishment and stock exclusion measures.
- Undertake early screen planting to enhance visual aspects of the development for neighbours and the community.
- Fence unaffected tributaries, streams, identified natural wetland, and remnant bush areas to exclude stock and establish a programme of riparian zone improvement in these areas. This would include removal of perched culverts and similar structures which currently form a barrier to appropriate native fish migration in the tributaries.
- Re-establish and enhance water courses once stockpiles are removed.
CLOSURE AND REHABILITATION
At closure of the Wharekirauponga Underground Mine, all ventilation stacks would be removed, and the ventilation shafts would be sealed. The shaft collars would be covered over and prepared to encourage natural revegetation.
The effectiveness of this rehabilitation would be monitored and managed for a period of no less than five years following closure to ensure the success of the remediation. The tunnel portals will be securely sealed, and the entrances backfilled with rock prior to the placement of topsoil.
All surface infrastructure at Willows Road will be removed, and footprint areas fully rehabilitated.
The effectiveness of this rehabilitation would be monitored and managed for a period of no less than five years following closure to ensure the success of the remediation. The tunnel portals will be securely sealed, and the entrances backfilled with rock prior to the placement of topsoil.
All surface infrastructure at Willows Road will be removed, and footprint areas fully rehabilitated.
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