Mine Drainage and Surface Mine Reclamation. Volume I: Mine Water and Mine Waste. Vol. I. Pittsburgh, PA: U.S. Bureau of Mines, 1988 Apr; :11-19
Prediction of the potential for acid drainage formation is required as part of the coal mine permitting process. Overburden analyses, by methods such as the acid-base account, are in common usage as part of this prediction despite the fact that a quantitative correlation between overburden properties and post-mining water quality had never been demonstrated adequately in the field. This study was designed to test the accuracy of predictions based solely on overburden analytical data. The study sites were selected to represent cases that have proven difficult to predict. Overburden samples were obtained from freshly exposed surfaces on highwalls or from cores preserved prior to mining. Post-mining drainage was analyzed at a reclaimed section of each site, paired to match the sampled overburden in terms of the presence and thickness of lithologic units. Overburden samples were analyzed by the acid-base account and a simulated weathering method. Overburden data were aggregated on thickness- and volume-weighted bases and water quality data were aggregated on a flow-weighted basis for each site. Drainage net alkalinity was correlated significantly (p<0.05) with the volume-weighted acid-base account parameters acid potential, neutralization potential, and net neutralization potential (r=0.358, 0.4197, 0.3799, respectively). However, when five sites having net neutralization potentials greater than 20 tons/1000 tons were excluded, these relationships became insignificant. Acid base account data showed boundaries useful in predicting the acid or alkaline character of post-mining drainage but no quantitative predictive equation could be developed. Simulated weathering test data correlated with actual sulfate concentrations in the post-mining seeps (r=0.4089, p=0.046), but the alkaline or acid nature of the seeps was not correlated with laboratory data (r=0.088, p=0.364).