THE GLADSTONE OPEN PIT
Recent exploration work has identified a new open pit mining opportunity on Company-owned land adjacent to our Processing Plant.
Regulatory approvals for the Gladstone Open Pit will be sought as part of the Waihi North Project. The proposed Gladstone Open Pit will be much smaller than the Martha Open Pit and will mine out parts of Gladstone Hill and Winner Hill. Once the Gladstone Pit is no longer being mined, it will be lined, backfilled with tailings, then capped.
OVERVIEW
The pit will have a depth of around 140 m below the top of Gladstone Hill, and about half that below the foot of Gladstone Hill. The length of the pit will be around 600 m. At its widest point, the pit will measure a little over 300 m wide.
To accommodate the new pit, the following preliminary works will need to be conducted:
Regulatory approvals for the Gladstone Open Pit will be sought as part of the Waihi North Project. The proposed Gladstone Open Pit will be much smaller than the Martha Open Pit and will mine out parts of Gladstone Hill and Winner Hill. Once the Gladstone Pit is no longer being mined, it will be lined, backfilled with tailings, then capped.
OVERVIEW
The pit will have a depth of around 140 m below the top of Gladstone Hill, and about half that below the foot of Gladstone Hill. The length of the pit will be around 600 m. At its widest point, the pit will measure a little over 300 m wide.
To accommodate the new pit, the following preliminary works will need to be conducted:
- An area planted in pine will need to be cleared.
- Topsoil will be removed and stockpiled for use in rehabilitation upon completion of the project.
- The construction of noise bunds, screens, and clean water diversion drains.
- The relocation of the existing underground mine portal and its infrastructure.
- Re-establishing the portal and portal infrastructure within the Gladstone Pit.
- A crusher will be established on the northern side of the existing conveyor. This will allow rock material to be crushed and conveyed across the Ohinemuri River to the TSFs and NRS.
- Re-align the gravel road from the end of Clark Street to access the motocross track.
- Relocation of a section of the mountain bike track.
EFFECTS
NOISE
If the Waihi North Project is approved, we will be required to manage our activities at the Gladstone Open Pit 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
Drilling and blasting in the pit will be required for the removal of ore and rock, although some of the upper areas may be excavated without blasting.
It is proposed that blasting will occur daily between Monday and Saturday; 7:00 am - 6:00 pm as required. OceanaGold Waihi will propose a compliance level of 5 mm/s for 95% of the monitored events. This is the same criteria that applies to our current operations. These levels are set to be protective of amenity and well below levels capable of causing property damage.
We recognise that some residents close to the Gladstone Pit may, from time to time, experience a perceived reduction in amenity due to mining activities. As a result, we will extend the Amenity Effect Programme to the Gladstone Pit area. Payments will be made to qualifying residents in accordance with the criteria of the existing programme.
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 we can take at the Gladstone Open Pit that may be implemented to meet these requirements, including:
LIGHTING
To provide for mining outside of daylight hours, lighting will need to be established in the Gladstone Pit, around the new explosives magazine and in the laydown areas.
All lighting within the pit will be relocated as required, and as mining activities progress. The lighting will be designed and located so that light spill is minimised to protect the amenity of nearby residents.
DEWATERING
Some dewatering will be required to lower localised groundwater and manage pit wall runoff from rainfall events.
Diesel or electric powered pumps will be located in the pit, and all pumped water will be directed to the Water Treatment Plant before discharging to the Ohinemuri River.
Small settling ponds, silt fences and diversion drains will also be built around the pit in order to contain the discharge of sediment to watercourses.
GROUND SETTLEMENT
The settlement effects associated with the Gladstone Pit are expected to be very small and pose little risk of damage to buildings or infrastructure. In the very unlikely event that property damage does occur due to settlement, OceanaGold Waihi will mitigate any adverse outcome by applying its ‘We Break, We Pay’ management measure.
HOURS OF OPERATION
OceanaGold Waihi is proposing that the Gladstone Pit operate 24-hours-a-day, seven days a week.
HERITAGE
There are some historic gold mining remains over much of the Gladstone Hill and Winner Hill area, that includes drives, shafts, terraces, and tailings. These remains have been assessed as having only modest heritage value. The area has been heavily modified by the planting of pine trees and prospecting from the 1970s to 1999. Whilst the effects have been identified as minimal, OceanaGold Waihi will undertake positive actions to address these effects as part of the broader Waihi North Project archaeological and heritage management measures.
PROPERTY DAMAGE
Consent conditions for vibration 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, OceanaGold Waihi will remedy the damage at our cost.
PROPERTY VALUES
The extension of the planned mine life to 2042, if approved, will continue the positive impact on property values that has been experienced in Waihi since modern mining commenced. Our property value assessment has identified the potential for the proposed Waihi North Project to have a minor impact on the values of a small number of properties near the Gladstone pit. This is not expected to be long lasting.
The properties identified in the assessment would be eligible for our Top Up management measure in accordance with the criteria of our property programme.
For full details go to www.waihigold.co.nz or contact OceanaGold Waihi directly.
REHABILITATION
Once the Gladstone Pit is no longer OceanaGold Waihi is currently proposing in-pit tailings storage using Gladstone open pit. In-pit tailings storage, as the name suggests, is the process of backfilling an open pit mine with tailings.
After mining of Gladstone is complete, the pit will be backfilled with tailings. The management of tailings is critical to environmental protection. In light of this, the pit would be lined before tailings are stored within it. This is to reduce the potential for seepage to enter the groundwater system. Although in-pit tailings storage is different to Waihi’s existing tailings storage facilities, the approach to tailings storage management remains the same:
If the Waihi North Project is approved, we will be required to manage our activities at the Gladstone Open Pit 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.
- Construction and vegetation of noise bunds.
- Limiting the height of stockpiles
- Acoustic cladding around potentially noisy machinery.
- Closed board fencing.
- Acoustic noise wall on sections of perimeter noise bunds.
- Limit when some activities occur.
BLASTING AND VIBRATION
Drilling and blasting in the pit will be required for the removal of ore and rock, although some of the upper areas may be excavated without blasting.
It is proposed that blasting will occur daily between Monday and Saturday; 7:00 am - 6:00 pm as required. OceanaGold Waihi will propose a compliance level of 5 mm/s for 95% of the monitored events. This is the same criteria that applies to our current operations. These levels are set to be protective of amenity and well below levels capable of causing property damage.
We recognise that some residents close to the Gladstone Pit may, from time to time, experience a perceived reduction in amenity due to mining activities. As a result, we will extend the Amenity Effect Programme to the Gladstone Pit area. Payments will be made to qualifying residents in accordance with the criteria of the existing programme.
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 we can take at the Gladstone Open Pit 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 drill rigs and crushers.
- Applying dust suppression product.
- 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.
LIGHTING
To provide for mining outside of daylight hours, lighting will need to be established in the Gladstone Pit, around the new explosives magazine and in the laydown areas.
All lighting within the pit will be relocated as required, and as mining activities progress. The lighting will be designed and located so that light spill is minimised to protect the amenity of nearby residents.
DEWATERING
Some dewatering will be required to lower localised groundwater and manage pit wall runoff from rainfall events.
Diesel or electric powered pumps will be located in the pit, and all pumped water will be directed to the Water Treatment Plant before discharging to the Ohinemuri River.
Small settling ponds, silt fences and diversion drains will also be built around the pit in order to contain the discharge of sediment to watercourses.
GROUND SETTLEMENT
The settlement effects associated with the Gladstone Pit are expected to be very small and pose little risk of damage to buildings or infrastructure. In the very unlikely event that property damage does occur due to settlement, OceanaGold Waihi will mitigate any adverse outcome by applying its ‘We Break, We Pay’ management measure.
HOURS OF OPERATION
OceanaGold Waihi is proposing that the Gladstone Pit operate 24-hours-a-day, seven days a week.
HERITAGE
There are some historic gold mining remains over much of the Gladstone Hill and Winner Hill area, that includes drives, shafts, terraces, and tailings. These remains have been assessed as having only modest heritage value. The area has been heavily modified by the planting of pine trees and prospecting from the 1970s to 1999. Whilst the effects have been identified as minimal, OceanaGold Waihi will undertake positive actions to address these effects as part of the broader Waihi North Project archaeological and heritage management measures.
PROPERTY DAMAGE
Consent conditions for vibration 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, OceanaGold Waihi will remedy the damage at our cost.
PROPERTY VALUES
The extension of the planned mine life to 2042, if approved, will continue the positive impact on property values that has been experienced in Waihi since modern mining commenced. Our property value assessment has identified the potential for the proposed Waihi North Project to have a minor impact on the values of a small number of properties near the Gladstone pit. This is not expected to be long lasting.
The properties identified in the assessment would be eligible for our Top Up management measure in accordance with the criteria of our property programme.
For full details go to www.waihigold.co.nz or contact OceanaGold Waihi directly.
REHABILITATION
Once the Gladstone Pit is no longer OceanaGold Waihi is currently proposing in-pit tailings storage using Gladstone open pit. In-pit tailings storage, as the name suggests, is the process of backfilling an open pit mine with tailings.
After mining of Gladstone is complete, the pit will be backfilled with tailings. The management of tailings is critical to environmental protection. In light of this, the pit would be lined before tailings are stored within it. This is to reduce the potential for seepage to enter the groundwater system. Although in-pit tailings storage is different to Waihi’s existing tailings storage facilities, the approach to tailings storage management remains the same:
- Robust design and site management including consenting, operational management, monitoring and reporting.
- Regular auditing of conformance with standards and consent requirements at a site and corporate level.
- Independent reviews by third-party experts.
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