Putting out a coal-mine fire, which can burn for years or even decades, is no small feat.
A recently extinguished fire in an abandoned coal mine on the Southern Ute Indian Tribe reservation required excavating all coal that was burning or was hot enough to catch fire spontaneously.
This highlights the challenges facing the state as it attempts to catalogue and mitigate the impacts of such fires.
Coal-mine fires are caused when the inherently flammable coal, exposed through mining activities, is somehow ignited. Possible ignition sources include lightning strikes, wildfires, human activities and spontaneous combustion. Once sparked, the fire can burn as long as coal and oxygen are available.
The potential dangers to the public and the environment have prompted the state to conduct a new statewide coal-mine fire survey, said Kirstin Brown, a project manager with the Colorado Division of Reclamation, Mining and Safety.
An expert will spend about a year in Colorado studying and analyzing coal-mine fires, Brown said. The last complete survey was completed about three years ago.
Brown, a geologist, also works on projects around Silverton to stop acid-waste drainage from abandoned mines that once produced gold, silver, copper and zinc.
The recently extinguished Ute reservation fire ignited from spontaneous combustion in the old Fort Lewis Mine, which was closed and the terrain revegetated in 1986, Brown said. The fire was discovered in March 2009 when the tribe noticed steam rising from a bare spot in the snow, she said.
The fire was near the Fruitland outcrop, where coal seams reach the surface in an arc running from the New Mexico border southwest of Marvel to the northern rim of the San Juan Basin northeast of Bayfield.
Brown said the reservation coal mine, located in Soda Springs Canyon about four miles southeast of Marvel, was worked from 1888 to 1941, when operations ceased.
When the fire was discovered two years ago, the federal Office of Surface Mining, which did the 1986 reclamation, passed the responsibility for extinguishing it to her agency, Brown said.
The Office of Surface Mining funded her agencys work in Soda Springs through an annual grant to reclaim abandoned coal mines, Brown said.
Wheatridge-based RMC Consultants was hired to do the on-site spade work, Brown said. The operator, with an excavator and loaders, dug out four of the old mines nine portals.
Surface temperature at fissures in the Earth reached as much as 900 degrees Fahrenheit, Brown said.
Fire shot from a fissure on one occasion during excavation when oxygen reached smoldering coal.
The coal was removed, mixed with dirt and sprayed with water laced with a fire-retardant foam. When it was cold, the mixture was replaced in the excavated area and compacted to reduce contact with oxygen, Brown said. The surface was then covered with straw mulch and native grass and shrub seeds.
This was our way of putting out the fire, Brown said. Other ways would be to dig a cut-off trench to prevent the fire from spreading or cut off oxygen with a dirt cap or by injecting grout to fill underground air pockets.
The excavated area was about 250 feet long and ran as deep as 45 feet.
We think we got all the fire out, Brian Sweet, the RMC Consultants employee on the job, said. Its an achievement because its very challenging.
Monitoring devices called thermocouplers are keeping watch on the site, Sweet said. A thermocoupler is a wire that runs from a point where the coal seam meets an excavated area to the surface. There, a thermometer can be plugged in to check the temperature.
Five thermocouplers were installed, Sweet said.
The Utes will take charge of monitoring the site for possible temperature changes, Sweet said.
Coal-mine fires arent new to the area, Brown said. At a spot known as Cinder Buttes, about three miles south of Redmesa and two miles east of Colorado Highway 140, red rocks offer evidence that in a past geological period, coal fires oxidized material in the rocks, giving them their telltale color.
About five years ago, her agency helped the National Park Service extinguish a coal fire at Mesa Verde National Park. The work helped protect archaeological artifacts, she said.
Otherwise, there arent a lot of large coal fires in Southwest Colorado except on the Ute reservation where numerous coal fires smolder, Brown said. The Utes deal with those fires themselves. Kyle Siesser, with the Southern Ute Growth Fund, said he must get approval from the Tribal Council before discussing the tribes firefighting efforts.
Brown estimated that 30 fires similar to the Soda Springs fire are burning throughout the state. Hundreds of coal fires smolder over the entire country, including one in Centralia, Pa., which has been burning since 1962 and which forced almost all its residents to abandon the town site.
Sweet said a coal-mine fire expert who is going to conduct the one-year survey visited the Soda Springs job site about a year ago with a thermal-imaging device to determine where to excavate.
The radar-like instrument indicated where there were hot spots, Sweet said.
The coal-mine fire expert will be based in Glenwood Springs, Brown said. He will use instruments such as a magnotometer, which measures the intensity and direction of magnetic fields in the Earth. Magnotometers also serve to locate sunken ships and obstacles for drilling operations.