PROJECT  QUATTRO

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GLADSTONE OPEN PIT

 

Recent exploration work has identified a new open pit mining opportunity in the Waihi area. As part of Project Quattro, OceanaGold Waihi will seek land use, and other consents for this pit on Company-owned land near our processing plant. The Gladstone Open Pit will be much smaller than Martha and will mine out parts of Gladstone Hill and Winner Hill. 

Options for using this pit as a tailings storage facility are currently being investigated. If these do not eventuate, it is proposed that the pit will be rehabilitated by backfilling it to a profile that approximates the existing landform. We will share more in-depth details of the proposed options as they become available. Community feedback will contribute to the final project design.

 

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.

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 removal of the existing underground mine portal and its infrastructure.

• Re-establishing the portal and portal infrastructure in an area north of Gladstone Hill.

• A bridge will need to be built across the Ohinemuri River to the North of the existing bridge. This bridge will allow for rock material from the pit to be hauled across the river to the TSFs and Northern Rock Stack.

• 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.

HOURS OF OPERATION

OceanaGold Waihi is proposing that the Gladstone pit operate 24/7, however it is proposed that blasting will occur daily between Monday and Saturday; 7 am - 7 pm.

DEWATERING

The Gladstone pit may not be effectively dewatered by the existing underground mines. Some dewatering will be required to lower 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.

REHABILITATION

The option to backfill the Gladstone pit with tailings is currently being investigated. This option would see the pit backfilled with tailings then capped with layers of rock and soil and planted.

If this option proves not to be practical, the pit will be backfilled with rock sourced from within the Gladstone pit or from Martha Open Pit Phase 5, and sealed with a capping layer. Stockpiled topsoil saved from the initial excavation work will be re-laid to a form profile that approximates the existing landform. This process is expected to take around three years to complete.


KEY EFFECTS

HERITAGE

Whilst most of the adverse effects on archaeological and historical sites is confined to the Martha Phase 5 pit area; there are also lesser effects attributed to the Gladstone pit.

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 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 offset and compensate for these effects as part of the broader Project Quattro archaeological and heritage management measures.


NOISE

If Project Quattro is approved, we will be required to manage our activities so that we comply with strict noise limits in line with the Hauraki District Plan.

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.


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 am - 7 pm.

OceanaGold Waihi will propose a compliance level of 5 mm/s for 95% of the monitored events. This is 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. In an effort to offset this, 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 Project Quattro is approved, we will be required to comply with consent conditions for air quality through a regional consent from the Waikato Regional Council. This will require OceanaGold Waihi to produce an Air Quality Management Plan, which must be approved by the Regional Council.

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 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 the amount of light is protective of the amenity of nearby residents.

PROPERTY EFFECTS

DAMAGE

Consent conditions for vibration will be set well below the level where cosmetic 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.


VALUES

The extension of the mine life to 2037, 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 Project Quattro 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.