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Colorado’s abandoned mines pose many dangers — this state program works to protect, preserve the relics

"It's a great opportunity to truly dig in and solve what hasn't been solved for 100 years," said Jeff Graves, director of the program.
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Pennsylvania Mine
Jefferson County mine reclamation project_Colorado Department of Reclamation, Mining and Safety
Posted at 2:22 PM, Oct 31, 2023

Stuck between a rich past and uncertain future, Colorado’s abandoned mining structures that carried much of the identity of the state now dot mountainsides in various states of decay.

The latest estimates have counted about 23,000 abandoned mines in Colorado, though experts say this is a low approximation and there are likely hundreds of thousands of mining features leftover from the mid-19th century into the 20th century.

Time has rotted the wood. Animals have moved into the tunnels. Wind tested their stability. Snow collapsed roofs. And yet, these derelict mines continue to draw in human curiosity.

A state program created in 1980 called the Inactive Mine Reclamation Program, under the Colorado Department of Mining, Reclamation and Safety (DRMS), helped curb the number of rescues and recoveries by blocking public access to the abandoned mine openings.

Colorado’s abandoned mines pose many dangers. This program works to protect them

The program has successfully safeguarded an average of 300 mines per year in Colorado, but is regularly challenged by vandals, a limited budget and the rough high country.

"I think for myself, and a lot of my staff, we like solving problems," said Jeff Graves, program director for the reclamation program. "I think most of us recognize that this is an opportunity to pay it back to some extent also. We're protecting the public from hazards that they may or may not be aware of. We're also doing projects that help to clean up our environment, while also protecting Colorado's heritage."

Colorado's origins in mining

For every abandoned mining structure along a popular trail, there are dozens of others hidden far from any trailhead, road or town. But they're all part of the story of how mining was the engine that made Colorado run.

Graves said mining was likely the state's only economic driver at the time, outside of potentially ranching and some forestry.

"Most of the mining took place within Colorado along what's kind of referred to as the Colorado Mineral Belt," Graves said. "Generally, that's the kind of northeast-southwest trending geographic area that goes from about Boulder County all the way down to the San Juan Mountains in southwestern Colorado. It's kind of a long linear feature and most of the mining took place along that zone."

map showing abandoned mines_Colorado Division of Reclamation, Mining, and Safety
This map shows about 12,500 abandoned mines that have been safeguarded, reclaimed, or restored by the Inactive Mine Reclamation Program since 1980. Tens of thousands of abandoned mines are still candidates for this work.

Rachel Storm with the History Colorado Center said the lasting impact of historical mining in the state left the landscape dotted with derelict mining structures.

"Headhouses and, you know, leftover mining buildings," she said. "And underground, of course, we have an extensive cleanup that needs to be done as well to make our environment safe for us."

She said miners first stormed into Colorado in 1858 to pan for gold and the subsequent gold rush in Colorado exploded the following year (and again in the 1890s), followed by the silver boom in the 1870s. Coal was produced throughout and remained mostly steady, while gold and silver mining was much more tumultuous.

"But it does, in general, for people who are not in mining, bring a lot of money into the state of Colorado, because Colorado becomes a state during that time," Storm said. "And part of that statehood in 1876 is in large part due to the mineral wealth of the state, and the ability of the state to be able to contribute to the nation as far as wealth goes."

Mining was a dangerous occupation. Miners worked on 12-hour shifts in dark, cramped spaces. Injuries and deaths were common, so much so that the women who ran nearby boarding houses were often widows. Children were responsible for placing dynamite deep in the mine and if they were not fast enough, could get caught in an explosion.

"The other thing too is you're working with mine shafts that have been hastily built," Storm said. "Crumbling infrastructure that's in the mine is not well-maintained. And so there's just a lot of hazards."

Funding for the mining industry began to decline in 1893, when Congress repealed the Sherman Silver Purchase Act of 1890. This started with big mergers and smaller wages for miners, which led to a labor shortage and strikes.



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"And so as mines are abandoned — they are really just left," Storm said. "There was not the same kind of concern about safety that we have today back then. So they just walked away from them, which is why you can drive around up in the mountains of Colorado and find so many random mining structures there."

Graves said some mining structures look like workers just up and left one day, leaving everything behind.

"And they would just walk away, I think a lot of times with the anticipation that they would be coming back, potentially," he said. "But for whatever reason, economics or something else drove them to not return in a lot of situations."

Environmental impacts were rarely, if ever, considered at the time, he added. Most of the state's mineral mining activity predated environmental regulations of the 1970s and 1980s. By the 1940s, most mining structures were deserted.

Curiosity leads to rescues and recoveries at Colorado's abandoned mines

The disregarded mines were built to last decades but the structures weakened without proper maintenance and routine care. It wouldn't take long before curious minds did more than just walk by, admire, and move on.

Open mine shafts, portals and adits — which are essentially gaping mouths that led to a mine's inner workings — became temptations and were treated more like caves than unstable mines.

The DRMS has reports dating back to the 1950s on abandoned mine-related rescues and fatalities, though it notes there are no official documents detailing these incidents, so they are instead compiled from state records and search and rescue organizations.

There were two airmen in November 1962 who were exploring a mine when one fell about 170 feet and was seriously injured. A 19-year-old boy was walking outside at night in August 1967 when he fell 40 feet into a shaft and held onto a rock, dangling about 600 feet above the next level in the mine. One of his rescuers suffered from shock. During the summer of 1986, three drunk men broke into a Gilpin County decrepit mine and had to be rescued. One punctured a lung and another had a collapsed lung. In July 1998, rescue workers spent a full night helping two men from Commerce City get out of a crumbling mine. According to the report, the men had ropes to lower themselves into the mine, but had no plan to get back out.

More recently, emergency crews had to rescue a 15-year-old boy in Golden after he used clothes line to rappel into an abandoned mine shaft in December 2017. And within the past year, the Sugarloaf Fire Protection District helped in a rescue at an abandoned mine in Boulder County. That opening was closed afterward.

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Earlier this year, the Sugarloaf Fire Protection District helped in a rescue in Boulder County. The mine was closed up afterward (photo on right).

But other rescue efforts simply weren't enough.

Some of the fatalities were from falls: A boy fell 320 feet to his death in a mine in May 1965, a Colorado Springs man fell 900 feet in a Cripple Creek mine in April 1986, and a 2-year-old slipped and fell 200 feet into a mine behind his family's home in Central City in March 1989.

Others died of lack of oxygen or lethal concentrations of carbon dioxide. A soldier from Fort Carson died in September 1968 after he was overcome by gasses in a Cripple Creek mine and fell 90 feet. Three teens explored a Mesa County mine and died of carbon dioxide poisoning about 300 feet from the entrance, which had been previously safeguarded but the steel door was vandalized and pried opened a few weeks prior.

And some people were killed by the overall unsteadiness of dilapidated mines, like a man who was exploring one in Fremont County in August 1989 and triggered an 800-rock to move, which pressed against his chest and suffocated him. Human remains were found as recent as 2020 in an abandoned mine west of Pueblo.

It quickly became apparent that people needed protections from the mines (namely their own curiosities) and the many threats that reside within the dark underground tunnels.

The dangers that lurk in abandoned mines

While the pace of rescues and recoveries of the 1950s through the 1990s has slowed nowadays, the same hazards remain within the hollowed out parts of an abandoned mine.

First, there's the structures themselves.

"These are not safe features," Graves explained. "Even though they may seem like they're stable, oftentimes you can't understand those risks because it's just an unfamiliar type of situation."

Rotten timbers can collapse at any time.

"While it may be a horizontal entry, there will be vertical features that are sometimes disguised on the floor, covered with rotten timber, water-filled, something like that," Graves said. "And so, if you're not watching your step or understanding the context of the environment you're in, you can fall into a vertical opening, even though it was a horizontal opening to begin with. And so, there's a lot of overhead hazards and falling hazards associated with those mines."

Many mines are also located on private property, meaning landowner's permission is required to enter.

"Even though there may not be signage around those locations or an indication that this is private property, most of these are on patented mining claims and so are private property," Graves said.

Explosives inside the mines can grow more unstable over time and old dynamite, which contained nitroglycerine, can explode with the slightest disturbance. Rodents can scatter blasting caps on the ground and if stepped on, they will detonate.

Then there is the wildlife that can call mines home. Take for one denning bears, which have been found in portals in Boulder County. Bats also often settle into the darkness beyond the opening. Venomous rattlesnakes wander into the mines closer to the Front Range in search of shelter and prey. In 2020, a 250-pound elk was found in a mine shaft near Creede.

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Abandoned mines are home to more than a dozen species of bat in Colorado. Bat-related information gathered during a project’s development stage can help managers decide which mine features need bat-friendly closures.

A 2022 study that focused on 50 abandoned mines in the northern Sangre de Cristo Mountains also found that the underground tunnels are used by mountain lions, foxes, bobcats, coyotes, skunks, weasels, ringtails and raccoons.

Along the unventilated tunnels, mines also store invisible killers.

"A lot of times the hazards can be things that are unseen, like dangerous gasses," Graves said. "So, you can have low-oxygen environments in a lot of these situations and you don't recognize that until you get far enough back that oftentimes it can be difficult to get back to the surface."

Especially in western Colorado, abandoned uranium mines are also potential sources for radiation, which can be deadly.

The DRMS' Stay Out, Stay Alive campaign was created with these hazards in mind. Its message to the public is simple: Don't try to access these kinds of mines.

"We've seen a reduction in the number of rescues and certainly in the fatalities, which we're very encouraged by," Graves said. "But there still are situations where, you know — it seems like every couple of years, we have some kind of a rescue from a site, oftentimes by teenagers."

In the last five years, at least two teenagers have been rescued from abandoned mine sites where they repelled inside to explore and became stuck, he said.

"So that's really where we try to get the word out," he continued. "We've recently launched some social media, trying to reach out to the younger generation and get the word out regarding safety hazards associated with abandoned mines."

What it takes, and costs, to close mine opening

As of the summer of 2023, nearly 13,000 mining sites — predominantly the ones most easily accessible to the public — have been safeguarded over the past 43 years.

big mine closure_Colorado Division of Reclamation, Mining, and Safety
This large mine opening in Fremont County needed custom-fabricated grates.

"I'm really proud of what our program accomplished over the last 40 years," Graves said. "We've gotten a lot of mine features closed. And I think from most of the partners that we work with, I think our program has been very effective, and working with local agencies, local municipalities to address their concerns. And then working with local landowners to safeguard their properties and reduce their liability and risk."

He explained that the department spreads both project managers and funding around the state. The managers are plugged into the local community and communicate with the U.S. Forest Service and Bureau of Land Management to recognize any local sites that need to be addressed.

"And so we'll plan projects geographically in those different areas and prioritize things that we know are easily accessible — that based on our observations, create a significant safety hazard," Graves explained. "And then we'll start to put together a project with a number of features in a localized geographic area, and then figure out how much funding we're going to need based on the closures that we're going to recommend for those types of features."

That process can last anywhere from two to three years, and typically ends with a cost estimate.

That's when the DRMS will go through the National Environmental Policy Act (NEPA) process, which requires agencies to assess any environmental effects of a specific proposal, like closing a mine.

"Since these are federal funds that we're spending, we have to go through and evaluate things like impacts to threatened and endangered species, (and) impacts to historical structures through our State Historic Preservation Office," Graves said.

Once complete, the DRMS can put out a bid for a contractor and begin the project. On average, each one takes a year or so to complete. One of the final touches is the installation of interpretive signs if the site is notable or near trails or roads.

Based on the structure that needs safeguarding, the project can take different forms.

Most of the time, the entrances are blocked using adit bars or adit grades.

Backfill is also used if enough material is available and if it works with wildlife usage and doesn't damage historic features.

"Sometimes we'll have large culverts — corrugated steel pipe with a grate on the end of that — and those grates will look very different," he said. "Some will have bars that have gaps of about six inches in between. And those allow bats to ingress and egress out of those sites. Sometimes we won't have bars because we've identified that there's no bat usage for that feature and it’ll just have grates."

Colorado was one of the first states to include bat habitat preservation in its mine land reclamation program.

bat ladder gate for mine_Colorado Department of Reclamation, Mining and Safety
This is the first bad ladder to be installed by the Colorado Department of Reclamation, Mining and Safety in 1995. Since then, the department has used the expertise of bat biologists and other professionals to refine its design.

Other mine openings have doors, if the landowner decides they may want access to the site in the future.

Regardless of the safeguarding methods, crews find evidence of human visitation at just about every site, especially at ones that have easy public access. In some cases, it's something harmless — albeit creepy — like a discarded skeleton dummy. In others, it's the broken and bent pieces of the door grates.

As a result, some abandoned mine openings must undergo regular maintenance.

"And so, we'll try and adapt our closures to make them as inaccessible as possible," Graves said. "But we've always found that if somebody wants to get into something, they're probably going to find a way to. So we do encourage the public to let us know when they notice things that have been vandalized, so we can come out and repair those, in addition to just being aware that no closure is going to keep somebody out forever."

DRMS stresses that vandalism not only endangers people, but it also wastes taxpayer dollars.

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The DRMS worked in 2023 to safeguard this mine in Clear Creek Canyon's Virginia Canyon. The diagonal mine opening was a hazard for both people and animals. The slots in the finished grate allow bats to get in and out.

The multi-step process to close a single hazardous abandoned mine comes with an average price to the tune of about $5,000.

Graves explained the Colorado’s Inactive Mine Reclamation Program receives about $3 million in funding from the federal government through the U.S. Office of Surface Mining, Reclamation and Enforcement, which is part of the Department of the Interior. The Colorado reclamation program started in 1980, after the Surface Mining Control and Reclamation Act of 1977 passed and the Colorado General Assembly passed the Colorado Surface Coal Mining Reclamation Act, also known as the Coal Act, in 1979.

Those funds come in annually, Graves said.

"It's a function of how much coal is produced in the state of Colorado," he continued. "There's a fee that those operators pay to the federal government. The state receives half of that fee back to assist in reclaiming pre-1977 sites. And that's typically what we refer to as abandoned sites, or pre-1977, pre-law."

DRMS Project Manager on western slope_Colorado Division of Reclamation, Mining and Safety
A project manager with DRMS works at a site on the Western Slope for the Inactive Mine Reclamation Program on the West Slope.

In addition, the State of Colorado utilizes severance tax that is collected on oil and gas production to address some of those pre-1977 issues within the state, he said. That ends up being about $1 million each year.

The vast majority of this funding goes to safety closure work, Graves said. That includes not only protecting the public, but preserving the historic nature of the mining site.

"We also do fund a few historic restoration projects each year through a grant process to assist those local historic societies and protecting what their priority features are for a particular area," he added. "And so, we have done some historic restoration as part of that safety closure process."

The final arm of funding came with the passage of the Infrastructure Investment and Jobs Act.

"With the passage of the Infrastructure Investment and Jobs Act, or BIL — the Bipartisan Infrastructure Law — we're receiving a significant increase in our funding to address coal-related problems," Graves said. "So, we're receiving an additional roughly $10 million for the next 15 years annually to address coal-related problems."

That exact amount is $9,962,000 , according to the U.S. Department of the Interior.

Safeguarding abandoned mines is a 'great opportunity' for problem-solvers

The Inactive Mine Reclamation Program has successfully safeguarded about 13,000 sites over its 43 years. Using the estimate of 23,000 total abandoned mines in the state, that means they're more than halfway.

"The vast majority of the sites we've addressed so far are those that are most easily accessible to the public — directly adjacent to roadways, closer to population centers," Graves said.

Graves said the program protects about 300 abandoned mines on average each year. By that math, it seems like the program could be on track to finish the remaining 10,000 in about 33 years. However, Graves explained that the currently unprotected mine openings are mostly in more challenging locations, like up on rocky cliffs, far from any trails, or in places blocked by snow.

"We actually just did a project... that required a helicopter to fly materials to the location to add a grate to prevent access," he said. "I mean, it was along a trail, kind of trail system, just east of Jones Pass. But the only way to get equipment there to actually construct the safety closure was by helicopter."

So, the going may be slower moving forward.

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But these are challenges the DRMS team is eager to tackle.

The work is tangible and Graves' team can see each checkmark on the lengthy list.

"We've seen the benefits to the public in the long run," he said. "And certainly, for me, I like solving problems and a lot of these sites pose significant problems. And so, it's a great opportunity to truly dig in and solve what hasn't been solved for 100 years."

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Mayflower Gulch, located in the Dillon Ranger District, features multiple old mining cabins.