Friday, Nov. 1, 2019 | 2 a.m.
In 1857, the Grosh brothers almost hit pay dirt.
Ethan and Hosea are said to be the first to discover the Comstock Lode, a massive silver deposit located near modern-day Virginia City. They died, however, before they could lay claim to it.
Within a few years, the lode attracted thousands—Virginia City’s population ballooned to 25,000. A silver rush had begun, and mines began to spread throughout Nevada.
The Comstock Lode was the largest deposit of ore discovered in the state, but prospectors also searched for other productive mines—gypsum, gold and silver—leaving behind history, environmental concerns and public safety hazards.
The state’s Abandoned Mine Lands (AML) Program, which spans multiple government divisions, targets abandoned mines for cleanup and safety actions.
The Division of Minerals targets physical safety hazards. The Bureau of Corrective Actions in the Nevada Division of Environmental Protection (NDEP) deals with ecological and environmental effects of abandoned mine sites.
“We look at how close [mines] are to populated areas. ... If somebody is going to stumble on this site, what’s the exposure risk?” said Jeff Collins, chief of the Bureau of Corrective Actions. “Some of these are very remote, some are ... closer to population areas, some of them are closer to natural drainage areas.”
There are 190-200 legacy mines that operated between the 18th century and September 1989 that are being monitored by the AML Program. Mines in operation after 1989 are monitored by the federal Bureau of Mining Regulation and Reclamation.
What kind of physical dangers can mines contain?
The Nevada Bureau of Mines and Geology has a laundry list of potentially fatal things people may find in an abandoned mine.
For example, ladders and timber supporting sections of the mine can be weakened by years of neglect and dry rot, leading to cave-ins or falls.
“If a person is caught, he can be crushed to death,” the Bureau’s warning reads. “A less cheerful possibility is to be trapped behind a cave-in without anyone knowing you are there. Death may come through starvation, thirst or gradual suffocation.”
Deteriorating dynamite and blasting caps left behind can be prone to exploding when disturbed, and many mine shafts themselves have become hidden by vegetation, are not visible in darkness and are deep enough that falls can be fatal. It is recommended to not even walk near a shaft—the deterioration of the surrounding area can collapse.
In short, don’t enter an abandoned mine. And if you aren’t sure how to spot one, there are telltale signs.
“You’re obviously looking for ground disturbance. You’re looking for maybe a little different color of soil” from displaced dirt in the mine, Collins said.
Look for waste rock piles, abandoned equipment, buildings or visible excavations. On mountains, switchback roads zigzagging up can also indicate a mine is nearby.
Mines can also mean chemical hazards.
Coal mines are known for flammable gases such as “firedamp,” chiefly made of methane.
Methane and other flammable gases can build up in metal mines as well, which can cause fire-related dangers and a significant drop in oxygen.
There are other “damps” as well, such as “blackdamp,” a gaseous mixture high in carbon dioxide that can extinguish lights and cause suffocation. “Whitedamp” is a high level of carbon monoxide, which can be extremely deadly.
To help prevent accidents, locations of known abandoned mines are not public record. Collins said the Bureau doesn’t want to encourage exploration of the sites.
“We try to deter that, so we feel like the less we put out there, the better,” he said.
What kind of environmental impacts can mines cause?
Mining can cause severe ecological problems, including the release of harmful substances into the environment and groundwater contamination.
Ore, such as gold, silver and copper, often is found in the ground with sulfide mineral deposits. Those deposits are left behind when the sought-after metal is pulled from the area. Once uncovered, the deposits are exposed to the elements, which cause a weathering reaction and the formation of environmentally damaging materials such as sulfuric acid and more.
“Arsenic and lead are very common in the state of Nevada. We typically see those components of mining left behind,” Collins said.
This can disrupt drinking water, plant growth and can corrode infrastructure such as bridges.
Mine cleanup
Mines can be incredibly difficult to clean up, mainly because of cost, which Collins said can start at $3 million to $4 million, and go up to hundreds of millions.
Acid rock drainage is the flow of water out of a mine area in which the water picks up amounts of sulfur-bearing minerals as a byproduct of the mining process. This water, now highly acidic, can wreak havoc on the environment.
Typically, mining operations end up below the water table, requiring pumping when in use to stop the chambers of the mine from flooding. When the mine is left and pumping ceases, the water comes into contact with the minerals that make it acidic.
“It’s really hard to mitigate this contamination once it starts,” Collins said.
Acid mine drainage can have an orange or reddish hue to it and generally looks rusty. It can be clear and still dangerously acidic, however.
“If there’s water running out of what looks to be an old … tunnel in the side of the mountain, we recommend [that people] stay out of that water and keep their pets and their kids clear of that,” Collins said. “Just avoid that as best you can.”
If you stumble across an abandoned mine site, call the NDEP and ask to speak with the Abandoned Land Mines Branch at 775-687-4670 or the Abandoned Mine Lands Program with the Nevada Department of Minerals at 775-684-7040.
This story originally appeared in Las Vegas Weekly.
