Office of Surface Mining, Mid-Continent Regional Coordinating Center, Alton, IL

Abstract

Passive treatment technology has been primarily developed in Appalachia for treatment of discharges that lie above drainage. Because of differences in geochemistry, hydrogeology and mining methods in the Illinois and Interior Coal Basins, the application of passive treatment technology for the treatment of Acid Mine drainage (AMD) requires additional design considerations. In the Illinois Basin, most of the surface and underground mines lie below drainage. At a typical discharge, the acidic and metal-laden ground water seeps directly into streams and agricultural ditches as diffuse base flow. In this hydrologic setting AMD impacts are reduced (the deep and dark prevention method applies). Many AMD problems in the Midwest are associated with coal refuse disposal areas. These facilities are usually placed above the surface and, as such, above drainage. Common practice for prevention of AMD, where the coarse refuse is net acidic, is to use compaction followed by the construction a soil cap to restrict infiltration. This paper presents several problems that have restricted application of passive treatment at a number of mid-continent sites and suggest measures needed to remedy these limitations. The problems discussed include: 1) the collection of AMD from diffuse sources and the generation of sufficient hydraulic head for application of a vertical flow pond (VFP), 2) treatment of AMD with high acidity and metal loading, and 3) high aluminum content. Several sites will be discussed, including the Old Bevier, Cedar Creek, and Otter Creek AML projects in Missouri and the artesian Rock Island No.7 mine pool discharge in Oklahoma.