NewsLocal News


East Boulder mine reopens in Big Timber after new round of mercury tests

Latest tests show mercury below federal standards
sibanye stillwater logo.png
Posted at 7:39 PM, Apr 16, 2024

About two dozen Sibanye Stillwater employees will return to work Tuesday and Wednesday at the East Boulder mine near Big Timber after new testing showed low mercury levels underground, according to a company official.

Kevin Robertson, Sibanye Stillwater executive vice president of U.S. operations, wrote in a letter to employees that the highest level of mercury in the new test, conducted last week, was 20 percent below federal standards set by the Mine Safety and Health Administration (MHSA).

Those tests were conducted with "gold foil badges," which Robertson described as more sensitive to mercury. In addition, mine officials have tested underground work areas with devices known as Jerome J505 Mercury Vapor Analyzers, which Robertson called the "best detection devices for mercury vapor." Those tests showed mercury levels .05 percent of the MHSA standard, according to Robertson.

Robertson's letter was obtained by MTN News by the company in response to a query.

The mine shut down last weekafter employees wearing different sensors, called carbon-based "static badges," tested low levels of mercury slightly above MHSA levels, according to Robertson. The mine voluntarily removed employees from underground.

Mercury is a natural occurring element often found in underground mines. It can be toxic to humans, even in small amounts, with risks of damage to nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes.

Sibanye Stillwater was required to conduct mercury testing after obtaining a new water-discharge permit at East Boulder last fall. Those new test showed low levels of mercury, which prompted additional testing with the carbon-based static badges, Robertson wrote.

The mine is allowing employees to return underground on a voluntary basis Tuesday because of the short notice, and Wednesday's shift will be mandatory, according to Robertson.

For the initial shifts, workers will be required to wear half-respirators until the work area is deemed safe by testing with the Jerome mercury analyzer, according to Robertson.

The mine will continue testing with the gold-foil badges with the goal of phasing out the Jerome testing, Robertson wrote.

South Africa-based Sibanye Stillwater owns two hard-rock mines in Montana, the East Boulder and the main Stillwater mine near Nye. The company is North America's only producer of platinum and palladium, which have multiple applications, including as components in catalytic converters in automobiles.