Domestic mine article by Harold Hough

The gold rich Carlin Trend is heading into its sesquicentennial (150 years) of gold mining. What began as small operations in the 1870s has grown so much that Nevada, if it were its own country, would be one of the largest gold producers in the world.

But, with that history comes a lot of safety issues. The ground of the Carlin Trend is riddled with unmapped underground tunnels that are uncovered on a regular basis by Nevada mining companies. And, since Newmont is the largest operator in the state, it usually finds the most. That’s why it has been one of the first to focus on remote controlled equipment to remove the operator from the equation when involved in operating heavy equipment around unstable parts of the property.

Integrated Operations Help Newmont

Newmont Nevada operations include 14 open-pit and four underground mines and 14 processing facilities (In September, Newmont announced signing of a Letter of Intent to sell Newmont’s underground Midas Mine in Nevada to Waterton Global Resource). There are hundreds of different types of gold ore in the state, each with a different “ideal” way to process it for the maximum recovery rate. The goal for any gold mine in the state is to obtain the best recovery rate at the lowest cash price per ounce.

Newmont’s challenge is that their operations produce dozens of different type of gold ore. In fact, the Twin Creeks operation had eight different ores from 40 different zones. Flotation might be better for one type of ore at the mine, while biooxidation would be better for another type of ore. There is no single, perfect answer. Together, Newmont boasts the widest variety of processing methods of any gold mining complex in the world. This is critical as the ore grade of its Nevada ore has declined.

The answer to lowering the cash cost per ounce of gold is to send the different ores to different processes at different operations in order to achieve the highest recovery rates. “That is the real advantage we have in Nevada,” said a Newmont spokesman. “We constantly have trucks moving up and down Interstate 80.”

While some of the Twin Creeks ore goes elsewhere, the rest of it and other material from Newmont properties are processed in a massive autoclave that provides a 90% recovery rate. These autoclaves are 76 feet long, 22 ½ feet wide and weigh 950,000 lbs. each. By heating and pressurizing the ore, it not only negates the carbon present, it meets the strictest environmental standards. According to Newmont, pressure oxidation has higher capital costs than other methods, but the costs are predictable and it avoids the higher operational costs and disposal problems for the arsenic resulting from roasting and biooxidation methods.

By having several processing alternatives, Newmont has managed to effectively increase its ore reserves in Nevada. And, by using several processes, Newmont can increase the recovery rate at its current operations and bring lower grade ore deposits on-line.

Remote Control Critical at Previously Mined Sites

However, as Newmont has expanded its mining to lower grade deposits, it has found itself working around older operations that mined the high grade gold ore and then moved on – often leaving miles of dangerous underground tunnels. Experts estimate that the state contains some 300,000 abandoned mines, 50,000 of which are classified as potential public hazards. This is where remote controlled heavy equipment comes in.

Underground tunnels pose more than a sinkhole problem for heavy equipment. A dozer working on a slight slope may cause a void to collapse, causing a slight slope to become a dangerous incline – causing the equipment to tip over or even tumble down the slope in a landslide.

The answer for Newmont is a simple add-on developed by Caterpillar. It’s called Command and it can be purchased with new Cat equipment or added on. The controls are portable and are easily carried by an operator as they move around the site. The system was shown to the mining community in October 2010 at Cat’s training facility in Tucson, AZ. The equipment can also be used in environments that might easily tire an operator or pose other environmental risks.

Unlike totally automated equipment, which is becoming more common around mine sites, Command is a remote controlled device that is controlled by the equipment operator within sight of the equipment. Since the controls are just like those on the dozer, a heavy equipment operator familiar with dozer operations can quickly learn how to use them.

If an unstable area needs work, the operator can move the equipment to the site and then carry out the job from a safe location with Command. There are also several automatic shutoffs in the system is the equipment loses contact with the remote control device, the operator trips and falls down, or an emergency shutoff switch is activated on the cab, remote console, or mine control center.

Although automated equipment is still viewed by many miners with suspicion, equipment like the remote controlled dozer offers an attractive combination of low cost, safety, and hands-on attention by a skilled operator. It is clearly the most attractive and logical path to more mine automation.