Out of sight, not out of mind
In the late 1800s, Nevada had claim to the second-deepest mine shaft in the world. The Combination Shaft in Virginia City hit 3,250 feet (991 m) deep in 1875, second only to the Adalbert Shaft in the silver mines of Bohemia (Czech Republic). In the twenty-first century, the future of mining in Nevada may lie below the surface — this time, hundreds of meters down.
Underground hard-rock mining accounts for 40% of the world’s mining activities, but only 12% of run-of-mine production, according to consulting management firm McKinsey & Company. Currently, North America lags behind other regions like Latin America and Oceania in terms of run-of-mine by volume. Yet the majority of surface-level ores have already been mined, and the current rate of project initiations will eventually outpace the finite nature of the state’s surface-level resources. Forward-focused jurisdictions like Nevada are increasingly investing in underground mining methods with the hopes of improving productivity and costs associated with the processes.
By nature, underground mining is more challenging than its open-pit counterpart. Deep rock mass can be categorized by its high in situ stress, high temperature, and high water pressure. Additional technical and safety considerations are required to help prevent the risk of disasters like rockbursts, squeezing and creeping rocks, and redistributed stresses.
Importantly, each mine also has its own distinct geographical considerations that largely determine extraction methods — stoping may be profitable at one site whereas block caving may be sufficient at another. For these reasons, selecting the right underground contractor to provide the necessary technical acumen is of paramount importance to keep an underground mine safe and economically viable.
New technology makes underground drilling more attractive
In Nevada, underground contractors are partnering with mining companies to develop more efficient ways of mining deeper. Nevada Copper brought on mining contractor Redpath USA for a long-term contract to help with the ramp-up strategy at Pumpkin Hollow. The copper mine, which also yields gold, silver and iron, utilizes a mechanized transverse longhole mining method to help simplify stope sequencing along with cemented paste fill (CPF) methods. With its processing facility now in production, Pumpkin Hollow is expected to reach 3,000 mt/d by the end of the second quarter of 2022.
Small Mine Development (SMD) has carved a name for itself in Nevada’s underground drilling sector. In addition to providing underground platforms for exploration drilling, the company specializes in developing underground hardrock mine development. In particular, SMD has partnered with Nevada Gold Mines on several of their underground operations. SMD helped establish the requisite infrastructure at the Leeville mine, a gold mine that is part of the Carlin Complex, by installing bulkheads and long-term ground support. The Carlin Complex is also home to the Goldstrike and Portal underground mines, and all three use drift and fill, long-hole stoping, or both.
SMD’s work with Nevada Gold Mines expands to its operations at the Turquoise Ridge Complex in the Potosi Mining District. Here, the complex includes the Turquoise Ridge and Vista underground mines as well as surface pit operations. As the holder of the largest gold assets in the country, Nevada Gold Mines is setting the pace for its competitors to follow suit in conducting operations deeper underground.
The popularity of SMD’s services proves just how desirable underground mining is becoming in Nevada. Within recent years, the underground contractor has worked with a variety of other companies including First Majestic at its SSX and Smith mines, i-80 Gold Corp, Sabre Gold, and Jervois. The contracting company’s general manager Keith Jones attributes this activity largely to the cost of gold, but sees broader potential applications of Small Mine Development’s services in the region: “Underground mining services are currently a significant revenue generator since there is considerable expansion in the gold sector due to the favorable prices. We also see nearby growth prospects for battery metals.”
Jones believes that in the present day, innovations for underground mining will increasingly be related to automation and electrification of operating machines. Redpath is undertaking a project to do just that — working on automating both the drill and blast processes of conventional shaft sinking. Being tested in Germany, the technology has the potential to eliminate workers at the shaft bottom as well as increase sinking performance. As the method of extraction gains more popularity, it is likely that more investment will go into improving electrification and automation of underground mining equipment.
Image courtesy of Dariusz Sankowski on Pixabay