It’s not a gentle environment.
In Nevada’s central mountains, the Big Smoky Valley sits halfway between Las Vegas and Reno. The landscape combines mountains, high desert and endless sky--it’s equal parts beauty and desolation. The climate is extremely dry, and the little precipitation that does fall comes mainly as snow in the bitterly cold winters. In the summer, temperatures top 105oF (40oC). Along the east side of the valley, the Round Mountain Gold Mine sits near the town of Hadley, roughly 6,000 feet (1,800 m) above sea level. The enormous mine--its permit boundary covers more than 14,500 acres (~5,870 hectares)--operates year round, exposing its people and equipment to the difficult conditions.
But to the mine’s chief surveyor and operations support engineer Richard Musselman, who has worked at the mine for 16 years, it doesn’t get much better than this. “I’m working at a world-class gold mine with world-class people: nothing could be better,” he says. His statement is sincere--and he has the results to back it up.
Musselman’s team of surveyors and support engineers handles the surveying load for mining operations, planning and construction. For the team, the rugged locale contains a nugget of good news: It’s RTK heaven. Open skies and low vegetation allow the vast majority of Round Mountain’s surveying work to take place using RTK GNSS.
The geodetic framework for surveying in Big Smoky Valley is tied to a GNSS reference station on the Round Mountain site. Musselman worked with Artisan Spatial Technology in Las Vegas to develop a single calibration covering more than 200 square miles (520 km2) in the valley. Operating with a Trimble NetR9 GNSS Reference Station, the mine’s reference point is qualified as a High Accuracy Reference Network (HARN) station. The station operates 24/7 and is the positioning basis for Round Mountain’s surveying, monitoring and mine operations.
Round Mountain’s surveyors provide stakeout and quality control for construction projects such as roads, leach pads and tailings impoundments. The team also performs extensive work for as-builts and volumetrics, and provides general support to mining operations. The crews are equipped with Trimble R8 GNSS receivers and Trimble TSC3 Controllers running Trimble Access software. In addition to work in the mine proper, the Round Mountain surveyors use RTK for their work on boundary and mine claim surveys throughout the valley.
The surveyors use optical methods as well, operating a Trimble S6 Total Station or Trimble VX Spatial Station in locations where highwalls and equipment can block satellite signals or introduce multipath issues. The crews also used the optical instruments underground for control and data collection in an exploration drift at the mine.
Using assays from blasting drill holes, mine geologists determine which of the four process streams each load of ore will follow. After blasting, surveyors set color-coded lath to mark polygonal boundaries of the various ore grades, which are determined in the office and loaded into the survey data collectors. The polygons are also loaded into dispatch systems onboard the loading equipment. Based on the color codes, the machine operators know where to take the ore.
Like most production operations, labor and consumables are primary cost components. At Round Mountain, the major consumables include fuel, tires for the trucks and loaders, and cyanide for leaching. In 2011, the mine moved 77.5 million tons of material (57,407,407 cubic yards at 100 pounds per cubic foot); virtually all of it traveled in the mine’s gigantic haul trucks driving on specially designed haulage roads. Musselman’s group approaches haulage road design, stakeout and as-builts with the idea of reducing the mine’s operating costs. “We work to put in superelevations and make sure all the grades are good,” Musselman says. “That prevents rocks from falling out of trucks and getting run over, which can damage a tire. Tires stay cooler because they are on a nice consistent grade. And if you’re not shifting too often, you save fuel.” The effort has not gone unnoticed--Round Mountain has become a world leader in reduced tire wear.
As the mine extracts new ore, the pit gets deeper and its walls get steeper. Common in large pits, the steep walls reduce the amount of material removed to deepen the pit. In addition, the mine is located on the geologic faults that brought the gold near the surface in the first place. As a result, says Round Mountain geologist John Keefner, “something is always moving, somewhere.” To monitor the slopes and walls, Round Mountain teamed with Trimble to install an advanced slope monitoring system that integrates optical and GNSS positioning into a single, centrally-controlled operation.
The system uses two Trimble S8 total stations installed in monitoring buildings at opposite ends of the pit. The instruments are mounted on 8-inch (20-cm) steel pipes drilled and grouted into the ground. The buildings, which are connected to the mine’s power and communications system, provide 180-degree views for the total stations. Meteorological sensors at each shack collect information for atmospheric corrections. The instruments are controlled by Trimble 4D Control software running on servers in the mine office.
The control stations stream GNSS data to the server running Trimble 4D Control. There, the data are post processed in 24-hour sessions to produce daily updates on the station positions. The long data sets provide precise measurements and let operators detect any small, slow motion of the GNSS stations. As part of each measurement cycle, the total stations measure the control points. If the measurements reveal discrepancies, the staff can use the GNSS results to make any needed changes in the control points’ coordinates. Data from the GNSS receivers are also utilized by the RTK processing engine in Trimble 4D Control, which computes RTK positions at 1-second intervals. The RTK results can be used to detect sudden, larger movements at the antenna locations.
Setting up the monitoring stations presented unique challenges. The monitoring stations must have visibility to the entire pit, and Round Mountain offers few locations that meet the criteria. The station locations--by necessity very close to the lip of the enormous pit--are inherently unstable. As a result, it’s important to monitor the instruments themselves. The GNSS/optical control attached to each monitoring shack provides a control point for the instrument across the pit and also reveals any motion of the ground beneath the shack.
The mine’s slopes and highwalls are dotted with more than 200 nitrogen-filled sealed canister prisms. As new slopes are constructed, teams install prisms on steel posts driven into the earth. During mining, prisms are often lost or destroyed. “We buy a lot of prisms in the course of a year,” Musselman says. “The cost of the prisms is tiny in comparison to the value of the information and protection we receive from the monitoring system.”
The system automatically measures the prisms 24/7 at two-hour intervals. Each total station measures to all the prisms it can see, including the prism on its counterpart shack on the opposite side of the pit 8,000 feet (2,400 m) away. Using long-range targeting, the instruments point and measure directly to the center of each prism in a few seconds. Keefner says that earlier systems relied on an edge-scanning technique to detect the prism; the method was slow and could not provide precise measurement to the prism. With the new system, the mine’s geologists saw a significant decrease in variability of slope distances measured for a stationary prism. And because the monitoring system provides 3D coordinate measurements for analysis, it reduces the chances of overlooking the motion of a prism moving with a constant slope distance from the instrument.
Monitoring also gives the geologists a picture of the behavior of the slopes and materials. The mine is always changing and expanding, and monitoring helps in planning for new cuts and excavations. The system provides information on how the walls fail, and at what rates. For example, a slow-developing failure is underway at the south end of the mine. Over the long term, it will affect the south access ramp into the pit; the team is using data from monitoring points on the south wall to redesign the next highwall in that area. “Monitoring gives us better information on the modes of failure and what to expect,” says Keefner.
In addition to expanding the pit and production capacity at the Round Mountain Mine, Kinross has received a permit to develop a new mine a few miles north of the existing pit. The new Gold Hill mine will have its own leaching facilities and will utilize existing milling operations at Round Mountain. A 5-mile (8-kilometer) haulage road will connect the two mines. Mining, production and reclamation activities at the two facilities are expected to last nearly two decades. The work will require a steady stream of skilled surveyors and technicians, and Round Mountain has established an in-house training and development program for its surveyors. Surveyors regularly attend user groups and follow a progression plan that includes training on CAD software and techniques for design and volume computations. “Most of our surveyors attended the local high school and have come up through the ranks,” Musselman says. “By using good [training] products, I can develop these younger people into serious professionals.”
Round Mountain’s plans extend beyond training programs. Keefner already makes heavy use of the analysis and reporting in Trimble 4D Control, and has plans to take advantage of the system’s SQL functionality in Trimble 4D Control to read information directly from the monitoring database for use in Excel and specialized, third-party software. And there are plans to implement the software’s automated alerts and alarms to notify mine geologists when any motion in a prism or GNSS receiver exceeds preset levels.
In the longer term, Musselman sees opportunities for long-range 3D scanning and lightweight unmanned aerial vehicles (UAV) for photogrammetry and terrain mapping. Currently, the mine captures aerial data once per year to develop information for volume computations and updated terrain models. With a UAV, Round Mountain could fly its site monthly. Musselman has calculated that payback for the system is about one year, not including the benefits of more accurate photos, models and contours.
Mining is a very specialized, high-tech world. Most ore deposits are very low-grade, and it takes a combination of technology, people and processes to stay ahead financially. The high-tech surveying and monitoring systems make clear contributions on the financial side. But for Musselman, the bottom line is safety. “That’s what it’s really about. I can actually sleep better at night knowing that we are providing a safe place for our people to work.”
Musselman and his team extend their appreciation to Monsen Engineering for their extensive help and support on this project.
For more information about the Round Mountain Gold Mine, visitwww.kinross.com/operations/operation-round-mountain,-usa.aspx. Additional details about Trimble surveying solutions can be found atwww.trimble.com