New Solutions for Old Problems

Borax faces unique safety challenges associated with abandoned underground mine works lying beneath its primary mine in Boron, California. Men and machines work in close proximity to miles of underground tunnels. To mitigate the risk, Borax developed a high-precision global positioning satellite (GPS) system to help shovel operators navigate safely in potentially hazardous areas.

Borax produced nine million tons of ore from its underground mining operations from 1927 to 1957. With the introduction of large-scale mining equipment, the company closed its underground workings and converted the operation to a single open pit mine. Today, Borax mines ore at a rate of three million tons per year, using electric shovels and 240-ton haul trucks to expose the ore.

Tim Cotton is Borax's Manager of Mine Technical Services. “We have mined safely around our old underground mines for many years, but recently our operations began intersecting the oldest, which were mined in a method that left large voids. To compound the problem, these voids or ‘stopes’ were not filled.
The end result is that we have unstable ground which can result in voids opening up more than 300 feet above the known underground workings,” says Cotton.

Armed with this knowledge, Borax began developing a safety system, working closely with federal and state safety experts. First, Borax cordoned off all hazardous areas and limited access to designated personnel only. Next, exploration holes were drilled to detect any voids and confirm the location of underground stopes and development drives. Large voids were blasted to collapse and close them, then re-drilled to confirm that no new voids had opened up. Finally, the company applied a high-tech solution to its low-tech problem.

“We have extensive experience with GPS-based surveying and dispatch systems and excellent digital maps of the underground workings, so applying the equipment and principles to this challenge was relatively easy,” according to Cotton.

The system consists of a high-precision GPS receiver, radio data receiver and touch screen computer. The satellite antenna is mounted on top of the seven-story tall shovel, where it has an unobstructed view of orbiting satellites. The GPS receiver calculates the shovel's position in three dimensions, 10 times per second and provides visual guidance to the operator by showing shovel position relative to hazards such as underground voids.

“Our operators have adapted well to the system and have adopted it as an integral part of their safety protocol,” he says.