Rio Tinto continues work to lessen the visibility of Bingham Canyon Mine waste rock piles

(Al Hartmann | Tribune File Photo) Rio Tinto spent almost $10 million last year reclaiming the east waste rock projected, pointed out in 2015 by company official Michael Piercey. and a similar waste pile south of there.

Rio Tinto Kennecott continued to chip away last year at one of the mining company’s long-term goals — making the giant waste-rock piles from its Bingham Canyon Mine less visible from throughout the Salt Lake Valley.

But it’s going to take time, Rio Tinto Kennecott officials Steve Schnoor and Trevor Heaton said Wednesday in the company’s annual report to the state Board of Oil, Gas and Mining.

“They’re steep and they’re tall,” reclamation engineer Heaton said of the 1,000-foot-tall piles of gray, yellow and red waste rock left behind in excavating the huge copper mine in the Oquirrh Mountains.

Because existing waste piles east and south of the pit are at a steep angles of repose, topsoil cannot be added to induce vegetation to grow and lessen the stark appearance of the rock walls. So for the past year, he said, the company has deposited new waste rock in front of the existing piles, looking to flatten the slope over time. The new material also will be regraded to create a more natural topography.

(Al Hartmann | Tribune File Photo) Zeb Kenyon, senior environmental advisor for Rio Tinto, points out the newly constructed waste dump and cut-off wall that stabilizes the bottom of the tailings pile and deals with runoff from large rain events on June 22, 2015.

“We’re just starting this project,” Heaton said. “These projects will take years to accomplish.”

State mining officials should have no concerns about Rio Tinto Kennecott going the distance to fulfill its commitments, said Schnoor, the company’s manager of environment, land and water. The company has “far exceeded” the requirements of a reclamation agreement signed by Kennecott and the state in 1978, 11 years before London-based Rio Tinto bought the mining company from British Petroleum.

That contract required Kennecott to spend $50,000 a year in 1978 dollars — roughly $200,000 today — on reclamation. Heaton said Rio Tinto’s bills for work on the south and east waste piles last year amounted to almost $10 million, or about $2.7 million in ’78 dollars.

The projects started last year will be maintained this year, he said. More rock will be piled up to relax the angle of the waste-pile slopes, a soil cap will be added, seeds will be mixed in and a variety of testing “pods” will be established to help project managers determine what’s working best in revegetating the new surface.

(Al Hartmann | Tribune File Photo) A reporter stands in the foreground of a former rail dump that was rehabilitated in the 1990s on June 22, 2015. The native vegetation has taken hold at the bottom of the tailings mountain.

Heaton said Rio Tinto also is conducting some “cutting edge studies” of how waste-rock piles evolve geochemically over time, with particular attention focusing on the movement of water through them.

While those piles are commanding the most time and money, Kennecott also is continuing reclamation at the Barney’s Canyon Mine, which primarily produced gold from a pit north of the Bingham Canyon Mine for roughly 20 years. The work there is focusing on contaminated heap leach pads.

Board members asked only a few questions at the end of the presentation, all dealing with peripheral matters. Several commended the detailed nature of the report, which went through all of the reclamation projects undertaken by Rio Tinto. Those included the cleanup of evaporation ponds that led to the creation of the Daybreak community.

Bingham Canyon Mine<br>• Has yielded more than 20 million tons of copper in the 115 years it has been excavated out of the Oquirrh Mountains.<br>• Produces 13 percent of the copper needed annually in the U.S.<br>• Was purchased by Rio Tinto from British Petroleum in 1989.<br>• Is one of 48 mines and processing facilities, across 35 countries spanning six continents, owned by Rio Tinto.