Burning coal veins common throughout state, experts say
June 11, 2002
Burning coal seams like the one that apparently sparked the destructive wildfire in Glenwood Springs exist across Colorado.
In fact, underground coal fires also burn in the coal-producing eastern United States and elsewhere around the globe.
Virtually impossible to extinguish, they can burn for decades underground, sometimes at temperatures hot enough to melt steel.
“There are many of them in Colorado – as there are in almost every coal basin in the world,” according to Jim Cappa, chief of the mineral and mineral fuels section of the Colorado Geological Survey in Denver.
The burning seam in South Canyon outside Glenwood, blamed for lighting up tinder-dry surface vegetation, has apparently been smoldering for nearly a century, if not longer. U.S. Geological Survey records dating back to about 1910 make note of a burning vein in South Canyon, according to Steve Renner, a geologist with the state Division of Minerals and Geology.
A thriving coal-mining camp existed in South Canyon in the early 1900s and continued into the 1940s, though little remains of the abandoned community where coal was once extracted from several mines.
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Local historians aren’t sure what caused the fire, but mining operations weren’t necessarily the culprit, Cappa said.
Lightening strikes can ignite exposed coal beds. So can the normal oxidation that occurs in rocks. The chemical process generates heat, he said.
“Once enough heat gets produced, if conditions are right, and there’s coal nearby, it will ignite,” Cappa said. “It will burn and burn. It will burn for decades.”
There are some 20 to 25 underground coal fires burning in Colorado, according to various sources. Several are found along the Grand Hogback, a formation that runs from Redstone toward Meeker. The immense vein of coal in the Hogback stretches from Coal Basin outside Redstone, through South Canyon, to New Castle, Rifle and beyond, according to Renner. Mining occurred at various points along the way.
“It’s a pretty extensive formation,” Renner said.
Burning Mountain, the smoking peak west of New Castle, was the site of one of several coal mine explosions that occurred around New Castle in the late 1800s and early 1900s. Coal has smoldered inside the mountain for more than a century.
It was a dangerous underground mine fire near Rifle, however, that attracted national attention in the mid-1990s, when the Division of Minerals and Geology experimented with a new approach to extinguishing subterranean coal fires.
The fire, thought to have been ignited by spontaneous combustion about 90 years ago, produced temperatures of nearly 1,500 degrees and was considered among the most hazardous in the state.
Such fires produce deadly gases and the underground voids created as the coal is consumed can cause the ground to collapse, according to Renner.
For the Rifle fire, workers wearing gas masks drilled slanting holes into the red-hot coal seam and poured in a foamy grout – a mixture of fly ash, sand, cement, water, foam chemicals and air. The grout coated the hot coals, choking the fire.
The state geologist who was overseeing the work at the time believed the fire was about 70 percent extinguished with that trial effort, but coal apparently continues to burn in the old mine. Renner, who visited the site last year, said hot spots on the surface still exist.
With miles of unmapped coal seams, it can be difficult to pinpoint the location burning coal. And, a fire can smolder for years and them erupt again.
“It’s hard to tell where the fire is. You can’t see it,” Renner said.
Coal fires, like the one in South Canyon, can produce visible smoke that escapes from fissures in the surface.
As the coal turns to ash and collapses, soils can shift and new fissures formed to feed the fire with oxygen, according to Cappa.
In the case of old coal mines, the shafts and vent holes can feed a blaze with air.
“Until the coal is exhausted or the oxygen to keep the fire going is exhausted, it keeps on burning,” Cappa said. “It’s extremely difficult to put out.”