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Figure 2.4.2. The fire triangle. From Kim et al. 1993.
may include isolating the burning portion of the mine through controlled ventilation and flooding the area
with inert gases or nitrogen entrained foam extinguishing agents which are often successful. Inert gas usage
may include the introduction of cryogenic nitrogen or carbon dioxide or even combustion gases with a low
O
2
content that will not support combustion.
Fires in abandoned mines are quite another matter. Often they reside in the abandoned room-and-pillar
workings for many years before they are detected. Such long residence time heats the surrounding overburden
and rock strata, conditions the coal and dries the undergroundworkingsresultinginanever-increasingrate
of fire progression. These fires become intractable and may require heroic efforts and staggering cost to
bring them under control, usually with no guarantee of success. More often than not, the cost and effort
required for mitigation strains both government and industryresultinginapolicytodolittleornothing
(Michalski, 2004, p. 90).
The Centralia Mine Fire, located in the steep pitch, room-and-pillar mines in the anthracite coal fields of eastern
Pennsylvania, is an example of an underground mine fire on abandoned mined lands. The fire began in 1962 in
an abandoned strip mine pit made into a landfill dump (Dekok, 1986, p.20). The Buck Mountain coal seam was
exposed at the bottom of the pit underlying the landfill. As the trash in the landfill burned, the fire came in
contact with the coal seam and quickly spread into the underground workings. Eventually, the fire spread from
the Buck Mountain seam into the workings of other, overlying, mined coal seams (Bruhn, et al., 1983, v. 1,
p. 3.35). Over the years, numerous investigation and abatement projects were initiated that had either too little
funding or were implemented too late. As the fire spread, abatement cost escalated. Consequently, in 1983, the
United States Congress appropriated 42 million dollars to buy out the Borough of Centralia (Dekok, 1986.
p. 276) and relocate its 1000 residents and more than 600 buildings (Krajick, 2005, p. 52, 59). This was
considered to be the most cost-effective measure to distance the population from the dangers of the mine fire
(Tietz, 2004, p. 42) since a total excavation of the burning zone in 1983 would have cost 663 million dollars
(Bruhn, et al., 1983, v. 2, p. 6.36). This final buyout was in addition to the 200 buildings and 178 houses that
were demolished in the 1960s due to the fire
s encroachment on the Borough (Krajick, 2005, p. 60). The cost of
all abatement measures over the years and the final buyout, did nothing to abate the fire which has expanded
from ~195 acres in 1983 (Bruhn, et al., 1983, v. 2, p. 6.5) to ~400 acres in 2005 (Krajick, 2005, p. 60) to a
potential ultimate spread of 3700 acres (Bruhn, et al., 1983, v. 2, p. 6.29).
'
Acknowledgments
T
he author thanks Tomas A. Gray, P.E., Tetra Tech, Inc., Pittsburgh, Pennsylvania for his review of this chapter.
