Coal mine 'dewatering' of saline wastewater into NSW streams and rivers : a growing headache for water pollution regulators

Alteration to the ionic chemistry of a river or stream as a result of a land use activity, such as mining, would ordinarily be defined as pollution under most water protection legislation and therefore should be regulated. However, this is not always the case, particularly in NSW. This paper reports water chemistry in the vicinity of four coal mines in NSW. Each mine caused elevated pH and salinity and also modified the geochemistry of downstream waters. In all cases there was a change to the relative concentration of major anions and cations. In this study most reference (upstream) waterways had an ionic composition dominated by sodium and chloride ions while most coal mine drainage discharges caused increased concentrations (and often dominance) of sulfate and bicarbonate and other ions, in downstream waters. Results are compared to the Gibbs (1970) model for world geochemistry of surface waters. I discuss the implications of my findings to aquatic ecosystems and to the current regulatory approach controlling NSW mine wastewater discharges. I conclude that the levels and types of salts discharged to waterways from the coal mines are inadequately regulated and may represent an emerging environmental pollution dilemma.