Mill Operating

Waihi Gold's mill is back up and running ahead of schedule, just twelve weeks after the electrical fire in the Motor Control Centre.

The fire destroyed the switchboards that control power to plant equipment such as the SAG mill, where ore is ground to a fine powder before further processing. As this equipment is vital to precious metals production there has been no gold and silver poured since the beginning of May apart from what was in the mill circuit at the time of the fire.

The financial impact of loss of production is estimated at around $4M a week in lost revenue. There have also been significant impacts on staffing, suppliers and sub-contractors.

Several Newmont employees were redeployed to Boddington, Western Australia, for a few weeks to assist with the commissioning of a project due to start operations within the next month.

In the meantime staff who remained at the Waihi mill have been kept busy overhauling every corner of the process plant and attending a raft of training courses.

Mill manager Kirsty Hollis is pleased with the progress made during recovery operations.

"The early start up of the mill is a credit to everyone involved in the recovery project. I would like to convey my sincere thanks and praise to everyone who has helped ensure that the project was completed in both a safe and timely manner."

On the mill recovery job approximately 14,000 man hours have been spent installing around 10 kilometres of new cables and rewiring 95 motors.

Exploration staff and drillers are a hardy bunch.

At this time of the year, while most of us are high and dry during the day and we enjoy the warmth and comfort of our homes every night, these guys have gone camping. The campsite is so far off the beaten track the only way in or out is by helicopter or you would spend a few hours getting there on foot. Winter conditions are not conducive to access by wheeled vehicles.

These men work as part of Newmont's regional exploration programme. Their job is to drill for core samples to determine the potential for an economic gold deposit in the area.

A long time before the site was identified as a prospect worthy of drilling, the geology of the area was mapped and surface samples such as soils, rocks and stream sediments were analysed. Low impact ground and airborne geophysics activities also formed a vital part of the exploration process. The results of each of these pre-drilling activities helped to decide whether further investigation, i.e., drilling, was warranted.

Drill sites are chosen with consideration for the general lay of the land - geography and topography.

Right: The helicopter delivers a portacom to the exploration site.

Department of Conservation regulations control proximity of the site to streams and rivers, fauna and flora. The site must be approved by DoC before work can start. Any site clearing must be done by hand.

A drilling programme may comprise three or four drill holes. A drill hole samples a 100mm diameter core of rock from depths up to 600 metres. Each hole can take up to three weeks to drill. Not all areas are as remote as this one; in remote sites the drillers camp out on the site. Ahead of their arrival a helicopter delivers portacoms, materials to establish the camp and drill rig equipment, tools, fuel and supplies.

Four or five workers are flown in to the job by helicopter, accompanied by food and provisions. They live at the site for up to ten days at a time. The site is operating 24 hours a day with two workers on each 12 hour shift and one floating. They are in constant contact with staff back in Waihi through satellite phones and RT radio.

There are some home comforts. Generators provide power for cooking, lighting and hot showers. Fresh meat, vegetables, drinking water and other supplies are replenished every two or three days, weather permitting, via helicopter, and core samples are flown back to Waihi.

Typically a drill site covers an area approximately ten metres by ten metres. Water and drilling fluids are contained within the site. When drilling work is finished all equipment is removed and the site is rehabilitated. Everything that was taken to the site is returned to base. The camp and drilling site is returned to a state at least the same as it was before work began and enhanced by extra plantings.

Above: A home away from home.

Above: The aerial photograph shows the exploration camp adjacent to the drill rig.