From The Colorado Springs Gazette (Ryan Maye Handy):

Once a booming mining region, Teller County remains punctured by more than a thousand abandoned mines, but state officials say none are likely to poison the environment with toxic waste…

…in Teller County, the dangers of abandoned mines are different, said Bruce Stover, director of the inactive mine reclamation program for the Colorado Division of Reclamation, Mining and Safety. More than a century ago Cripple Creek was one of the most thriving gold mine sites in the world. In the 21st century, nearly all of the mines have been abandoned, and Stover is more concerned about people falling down shafts and dying of asphyxiation.

“We are not talking about any environmental issues in the Cripple Creek district,” he said.

Despite its extensive mining history, a few things ensure that Teller County mines are less prone to an environmental disaster, unlike areas of the San Juan mountains, where abandoned mines continue to pour toxic metals into nearby water sources.

Teller is home to one of the state’s largest mines, the Cripple Creek & Victor gold mine, which operates under heavy regulations passed in Colorado after the last mining disaster in the early 1990s. Unlike the San Juans, underground water networks in Teller are regulated and monitored, making the likelihood of toxic waste pooling unlikely.

But another thing that sets Teller County apart from the San Juans is geological luck. The formation of mountains millions of years ago made gold mining in Teller less toxic than in the San Juans, Stover said.

“There is really no comparison at all between the two districts,” he said.

Buffering minerals

Volcanic eruptions millions of years ago formed gold deposits in the San Juans and Teller County, and ancient reactions between lava and rock created the kind of minerals still found in local mines.

In the Gold King Mine, which was last operational in the 1920s, an underground lake of toxic sludge had been pooling for decades before a barrier broke on Aug. 5 and released 3 million gallons into the Animas. The Environmental Protection Agency was trying to address the pooling, and the agency has accepted blame for a reclamation job gone awry.

That level of toxicity is unlikely to occur in the Cripple Creek mining district, thanks in part to those ancient volcanoes. In Cripple Creek, the eruptions created a layer of minerals known as telluride ore, which does not have as much pyrite as the rock formations in the San Juans, Stover said. When it decomposes, pyrite can transform into a type of toxic acid.

The Cripple Creek formation also contains what Stover calls “buffering minerals,” which decrease the levels of acidity in the rock.

“It’s just the geology of the district,” he said. “It’s far less conducive to acid rock drainage. There are some but it’s not much.”

The Cripple Creek landscape is relatively young in terms of geological formation – about 35 million years old, said Christine Siddoway, a professor at Colorado College who specializes in the geological development of the Front Range.

The mountainous border between El Paso and Teller counties shows all the signs an economically profitable region for gold mining. According to Siddoway, western El Paso County sits on a fault system that allows underground fluid to heat, circulate and bring metals to the surface.

“Those high-temperature fluids are successful at carrying any metals, which leads to economic-scale mineral deposits,” Siddoway said. “In Colorado, gold, silver, precious metals are on ancient faults where there is much circulation of geothermal waters.”

But in the early mining days when prospecting was an unregulated free-for-all, separating gold from other minerals in a rock formation often came at a high cost. Sometimes chemical reactions using cyanide were used, but the reactions left behind toxic metals. To this day, even the most heavily regulated mines legally produce millions of pounds a year of lead and other carcinogenic elements as a by-product of the mining process, according to data from the EPA’s Toxic Release Inventory.

But chemical means of extracting gold were less common in Cripple Creek, Siddoway said.

“Historically in (the Colorado Springs area), those mines did not use any chemical reactions to liberate the gold,” she said.

But that doesn’t mean that the Pikes Peak Region was spared repercussions from decades of active mining. Decades ago, miners shipped ore to Colorado Springs, where it was mechanically crushed. The remaining mineral tailings were deposited in west Colorado Springs in modern-day Bear Creek Regional Park.

“Those historical deposits are still here in the Colorado Springs city limits,” Siddoway said. “There are some elevated concentrations of heavy metals. There is still particulate gold in those tailings.”

Tunnel network

In addition to the area’s geological makeup, heavy regulation of underground water tunnels and active mining will help the Pikes Peak Region avoid a toxic disaster like that in the Animas River.

Beneath Cripple Creek, a network of underground tunnels shuttle water away from mines, Stover said.

“The district is already completely drained from underground by large drainage tunnels drilled by large mines,” he said. “Those do have permits, discharge is meeting water quality. (The area) doesn’t have water collecting in pits and mine shafts.”

The Carlton Tunnel drains the entire Cripple Creek mining district into Fourmile Creek, a tributary of the Arkansas River, said Stover. Discharge from the Carlton Tunnel is monitored under a National Pollutant Discharge Elimination System permit, issued by the state of Colorado, EPA records show. The permit was first issued in 1992, and while documents show that the permit expired in 2011, the latest inspections of the tunnel were done in 2014. For 2015, permit data for the tunnel and the Cripple Creek mine showed that manganese, iron and zinc were the main pollutants released in the watershed.

While the tunnel network takes care of shuttling away and treating any toxic waste, Colorado’s mining regulations ensure that the still-active Cripple Creek and Victor mine complies with environmental standards, Stover said.

The environmental protections were borne of yet another Colorado mine project gone wrong: In the 1980s and 1990s, the Summitville gold mine in Rio Grande County was found to be poisoning the Alamosa River with heavy metals and acid from its tailings.

When the mine’s owners declared bankruptcy and were forced to abandon reclamation, the federal government took over and declared the mine a Superfund site, opening the door to federal funds for the clean up.

“Summitville was a slow-motion sort of thing that unfolded as the mine was being constructed,” Stover said. “That was a permitted site that went horribly wrong.”

The disaster sparked massive changes in Colorado law.

“It caused a lot of changes in Colorado mining reclamation rules and regulations,” Stover said. “So we have some much more stringent laws.”

The regulations came decades too late to impact many abandoned districts, like the Gold King mine, which had been mined and shuttered long before the state cracked down on mining. The Colorado Division of Reclamation, Mining and Safety estimates there are 22,000 inactive mines around Colorado, more than 6,000 of which have been reclaimed.

In Teller County there are 1,100 mines, nearly 500of which have been reclaimed and are blocked off with metal grates, Stover said. In El Paso County there are 153 mines, one of which has been reclaimed. The area mines that have been reclaimed and safeguarded are those that needed it most, Stover said.

“We started working concentrically out from Cripple Creek, we did around 493 mine closures in and around the towns,” Stover said. “And of course that all changed when the mine came in. A lot of the closures are gone, they would be hanging in space because of the new mine.”

Even so, mine disasters are possible in southern Colorado, even if the odds have been decreased by geology and regulations, Siddoway said.

“Because the mine is not in our watershed – it’s off away on the southwest corner of the Pikes Peak elevated area – it’s not of immediate concern. But the mine is on a drainage that follows a tributary of the Arkansas River, and the Arkansas River flows into Pueblo Reservoir, and soon into the Southern Delivery System,” Siddoway said.

“There is kind of a daisy chain there, were any accident to happen at the Cripple Creek mine.”