Coal Mine Fires and Burning Refuse
Caveat: Coal mine fires or underground mine fires are generic terms for coal seam fires. The reason the “mine” is used within the description is due to the starting point of the fire. The majority of coal seam fires start within active or abandoned coal mines. It is important to note that the mine itself is not on fire, but the remaining coal pillars, remaining coal seam, poor quality coal, or burnable debris left behind is what burns.
Majority of mine fires start through careless human activity, such as burning debris within an abandoned surface mine; however, mine fires can also start naturally via forest fires, lightning strikes, lava flows or other natural heat sources.
Underground coal mine fires occur around the world, sending thousands of tons of soot, toxic vapors, and greenhouse gases into the atmosphere, leading to pollution of surface and groundwater, mine subsidence as the coal is consumed, and ignition of forest and structural fires. Areas like the resort town of Glenwood Springs, Colorado has been plagued by series of suspected mine fire caused forest fires which burned thousands of acres of forest and many local residences.
Anatomy of Mine Fires Chart
Underground Mine Fire Thermal Cycle
When the fire travels into the ground from the surface it creates a thermal cycle. The thermal cycle consists of the fire heating the air causing it to rise and escape through passageways in the ground. The point on the ground surface where the heated air discharges into the atmosphere are known as vents. The heated air also carries the greenhouse gasses, noxious fumes, soot, and smoke. These vents are extremely dangerous and pose a serious health risk. Vents encountered or discovered need to be avoided, never get closer than 100 feet to a vent.
Back at the fire, with the hot gasses rapidly venting, this creates a negative pressure at the fire face. Cooler, oxygenated air drawn from the atmosphere outside of the discharge vents is pulled into the ground and ultimately to the fire, thus completing the thermal cycle. As the fire spreads into the coal seam new vents can form and old vents can change becoming intake vents.
Eastern Kentucky Mine Fire. The smoke is coming from underground haulage ways, exposed by surface mining. (SOURCE: Geology of Coal Fires: Case Studies from Around the World, The Geological Society of America.
According to e-AMLIS, in 2013 there were 98 underground mine fires in 9 states. This is considered to be an underestimate for the actual number of fires nationwide.
Road Subsidence and venting of mine fire in Centralia, PA
Coal Mine States address mine fire and coal refuse fire related emergencies within the states of Michigan, Maryland, and Georgia and within the Commonwealths of Kentucky and Pennsylvania. These projects range from burning coal refuse piles that threaten to ignite forest fires to underground mines fires that can burn beneath buildings, roadways and grounds releasing deadly gases and leading to mine subsidence. Abatement methods range from complete excavation and quenching with water (where practicable and affordable) to the use of specialty foaming cements and fire fighting foams that are injected into the fire through boreholes drilled from the ground surface. The intent of the injection is to isolate the fire with a barrier of foaming cement followed by the extinguishment of the fire by using a fire fighting foam. Other techniques that may be used include the use of liquid nitrogen to extinguish the fire by the rapid removal of heat.
Warning Sign from Centralia, PA
Frequently Asked Questions
Types of mine fires:
- Burning coal seam: This type of underground fire follows the fuel source (carbon) along the coal seam. Based on geological structure, these fires break into two categories:
- Horizontal coal beds
- Coal seams which are generally flat lying. Occurrences are generally east of the Rockies and in Northern Alaska. Fires within these coal beds are typically easier to characterize and delineate.
- Angular beds
- These coal seams follow geologic structures such as anticlines and synclines. The angle degree can be up to 90 degrees. These type of coal seams occur within the Rocky Mountain and Southern Alaskan Ranges as well as the anthracite fields of Eastern Pennsylvania. Due to the angled bedrock, characterization and delineation of these fires can be difficult.
- Horizontal coal beds
- Burning Refuse: These fires occur within coal waste piles or culm piles. Not confined to a singular seam, this fire type will burn from the ignition point spreading out into the pile. The difficulty in extinguishing these fires is due to the size of these piles. These piles can range in size from an acre to hundreds of acres, with the largest being 1.5 miles in length.