GEOCHEMISTRY OF COAL MINE DRAINAGE IN RESPONSE TO IMPROVED MATERIAL HANDLING: PRELIMINARY RESULTS OF KINETIC TESTING

In recent years, both U.S. Environmental Protection Agency (USEPA) and Illinois Environmental Protection Agency (IEPA) suggest regulating SO₄^2- and Cl^- discharges into natural waters to a lower standard than the current levels of 3,500 mg/L for SO₄^2- and 1,000 mg/L for Cl^-, respectively. To assist the coal industry, this study is performed to identify good management practices (GMPs) for minimizing SO₄^2- and Cl^- discharges from Illinois coal mines. Previous investigations by the authors and others have identified coal refuse disposal areas as a significant source of elevated SO₄^2- in mine discharge. In all cases, the main source of SO₄^2- in mine waters was the oxidation of pyrite.

This paper provides preliminary results for the kinetic tests performed to demonstrate the advantages of several proven GMPs identified for the reduction of SO₄^2- levels from coal refuse disposal areas.  In theory, the increase in the amount of fine refuse particles should allow increased compaction of the fill material.  This practice should reduce infiltration and weathering of pyrite contained in the waste rock. Ten, 6-inch-diameter by 24-inch-high leaching columns were employed to compare the SO₄^2- discharge from a compacted blend of dewatered fine and coarse coal mine refuse to the control columns containing only compacted coarse refuse.  The fine coal refuse was dewatered to 65-70% solids content and either blended or inter-layered with coarse refuse.  Additional tests were performed on columns, where an alkaline amendment, fluidized bed combustion (FBC) ash was added to coarse refuse and compacted. This extends the work of other researchers who successfully demonstrated this management practice. Finally, the two additional columns were constructed to evaluate the SO₄^2- discharge for raw coal stockpiles. The paper will present preliminary geochemical results of the column leaching tests and discuss the implications of these results.