Influence of water erosion on fire hazards in a coal waste dump — A case study

Dump fires are a significant environmental problem in post-mining areas. The TEXMIN project has shown that climate change could lead to more extreme weather events in the future, intense precipitation among them. The impact of water erosion on the development of endogenous fires in coal waste heaps has not been investigated thus far. Meteorological data collected from the studied dump area in Libiąż, Poland confirmed that heavy rainfall occurred many times, causing surface erosion on the slope. Gully erosion was observed on the western slope of the heap, the depth of which was up to 1.6 m. Data showed that between areas with and without water erosion, there was a significant difference in measured temperatures and gas concentrations that defined the fire intensity. Erosion facilitated self-heating such that internal temperatures increased to 52.9 °C. Further, at a depth of 1 m in the self-heating zone, maximum gas concentrations were 15.65 vol%. CO2, 10 ppm CO, and 0.435 vol%. CH4, while the O2 concentration dropped below 1.0 vol%. These results show that despite preventative measures, thermal activity reactivated in the vicinity of gully erosion and caused the self-heating zone to expand. [Display omitted] •In situ research was carried out on a coal waste dump.•The influence of precipitation on the condition of the slope surface was investigated with the use of photogrammetry.•Variations of temperature and gases concentration were analyzed for selected slope.•Water erosion contribution to spontaneous ignition of a coal waste dump was shown.