Effects of passive reclamation on water quality in the northeastern drainage of Augusta Lake, Pike County, Indiana

Abstract

Augusta Lake is a 33-acre man-made lake located on Mill Creek, a tributary of the Patoka River in the coal mining region of south-central Pike County, Indiana. The lake is strongly acidic (pH = 3.1-4.4) and mostly barren, receiving acidic inflows from a 1.5-square-mile drainage area, 60 percent of which consists of abandoned coal mines. The dominant source of acidity, sulfate, and metals is in the northeastern drainage area where acidic water seeps from mine spoil. An array of wetlands, anoxic limestone drains, and successive alkaline-producing systems (SAPS) was emplaced to treat this area. Beginning in 1997, water quality was monitored for 2 years at eight sites to evaluate the effectiveness of this passive reclamation strategy. The pH of water at all sites, other than the discharge from the SAPS and where surface water and SAPS outflow mix, remained acidic throughout the monitoring period. Acidity and pH varied seasonally at four sites, and pH was lowest and acidity highest during the months from late spring to early fall. Although Augusta Lake remained strongly acidic, outflows contained significantly reduced metals concentrations, indicating that natural processes operating in the lake remove metals from solution. Water flowing northward from the lake along Mill Creek rapidly approaches pH neutrality through natural reactions with the bedrock and sediments, and downstream reaches support aquatic life. Although Augusta Lake may not be suitable for recreational uses, it does serve the important function of cleaning dissolved metals from mine effluent.