Groundwater Pollution Resulting from Disposal of Pyritic Coal Wastes

Abstract

Coal-cleaning refuse, like, most other sulfide-bearing mineral wastes, is capable of oxidizing and producing very poor quality leachates, containing high concentrations of acidity, sulfate, and dissolved metals. Hydrologic and water quality monitoring at an abandoned refuse disposal site in southwestern Illinois was conducted six months prior to and four years following grading, liming, covering, and revege-tating the site. Although the coal refuse lay unreclaimed at the site for over 50 years, contamination of groundwater from acid leachates was not detected more than 150 m from the gob pile. The hydraulic conductivity was low enough and the neutralizing capacity of the underlying calcareous, silty-clay till was great enough to prevent further subsurface migration of the acid leachates. The effects of the 1977 site reconstruction on groundwater was monitored using 47 piezometers and 16 residential wells. Rapid acidification of parts of the basal portion of the graded refuse and underlying till were observed. However, some improvements have occurred in this area since 1979. Water quality in the slurry disposal area has improved significantly since reclamation and is now approaching ambient groundwater quality.