EFFECTIVENESS OF BEST MANAGEMENT PRACTICES FOR REDUCING POLLUTION LOAD AT COAL REMINING SITES

Eleven best management practices (BMPs) associated with the remining of abandoned mine sites were statistically evaluated to determine their effectiveness. The BMPs occurred hydrologically upgradient from 231 discharges associated with the abandoned mines. Pollution loads were calculated pre- and post-mining for each discharge. Success was measured as a decrease in load following mining. Too few sites increased in load to evaluate, so comparisons were between decreases in load and no statistical difference in load. BMPs were used in groups, thus statistical models were needed to evaluate the effectiveness of each BMP individually. The BMPs studied affect load physically (e.g., reduce infiltration) or chemically (e.g., acid neutralization). Surface regrading, daylighting of deep mines, revegetation, coal refuse removal, water handling, and biosolids application largely have a physical effect. About half the reduction in pollution load can be attributed to reductions in flow. Regrading and daylighting can effectively restore positive drainage, thus reducing infiltration. Biosolids application was effective in reducing acidity, sulfate, iron, manganese and aluminum loads and probably contributed to decreases in flow through promoting thick vegetation. Water handling, a broad category of BMPs, resulted in improvements in acidity, sulfate, iron and manganese loads, and deserves further study. Chemical BMPs include alkaline addition and special handling. Four alkaline addition strategies were evaluated: alkaline addition <240 ton/ha, >240 ton/ha, on-site redistribution of calcareous strata, and mining calcareous strata at higher overburden. The last two, where the material exists onsite, were successful in reducing loads for acidity, sulfate, iron and manganese. Alkaline addition at <240 ton/ha and special handling were not statistically effective at reducing pollution loads. This is likely due to inadequate neutralizing materials being available in both instances.