Why some producers are looking underground for answers

Yanik

The overwhelming number of crushed stone, sand and gravel sites I’ve visited throughout the last 10 years were surface operations. 

Only a handful of the producers visited mined underground. 

Still, the ratio of surface to underground mines in the U.S. could change in the coming years, with a shift emerging due to a few key factors. Jonathan Kolbe, vice president of production at Pennsylvania-based Allegheny Mineral Corp., is one such believer.

“There aren’t many underground mines right now, but I think you’re going to see more,” Kolbe says. “Because of development now, people are going to be pushed underground just to access reserves.”

Industry stakeholders have long shared how the nation’s best or most accessible reserves were already mined. The same people note how the deposits pursued today aren’t of the quality that was mined 50 or 100 years ago.

These days, producers are sometimes forced to get creative with their vendors to come up with processing solutions that are capable of manufacturing marketable materials. The nature of the nation’s remaining reserves can be costly and problematic, but producers work with what’s available because reserves, while aplenty in 2022, aren’t easily permittable.

Case in point

Allegheny Mineral Corp. opened up the Bison Plant, which mines underground, in 2017. Photo: P&Q Staff

In recent years, I’ve heard more stories about producers tapping into abandoned aggregate reserves that possess plenty of life. Allegheny Mineral’s Bison Plant in Worthington, Pennsylvania, is a classic example.

“Way back when, there was an underground mine here – years and years ago – and it went out of business,” Kolbe says.

Such narratives played out time and again throughout the course of U.S. history. Early in 2021, geologist Don Mikulic shared with P&Q how his yearslong research unveiled that more than 250 Chicago-area mines – some of which were underground – ultimately closed over the course of about 200 years. A number of the operations were rather small, Mikulic says, and many were eventually built over. But the collection of one-time active sites represents a substantial amount of reserves that could have been better utilized. 

Fortunately, some sites are being reassessed today for second lives. While the mine in Worthington at one time transitioned to mushroom harvesting, Kolbe says Allegheny Mineral’s parent company eventually stepped in and purchased the land holdings containing plentiful limestone reserves.

While an industry veteran like Kolbe can attest to the learning curve associated with going underground, ample reserves are available beneath the earth’s surface. Producers just need to know where to look.