Introduction

Past, present, and future coal mining in the Appalachian basin has caused, now causes, and will continue to cause changes in hydrologic conditions that result in oxidation and dissolution of minerals in coal and coal-bearing strata. Once mines are closed and abandoned, the oxidation and dissolution of minerals in coal-bearing strata often results in contaminated mine drainage (CMD). CMD may develop when closed water-filled underground mines overflow to the surface through leakages in mine seals, through fractures induced by mining, or through natural fractures. In contrast to underground mines, CMD develops after closure of surfaces mines when the ground and surface water that infiltrates and percolates through materials disturbed by mining and reclamation subsequently discharges to the surface and into surface streams.

The degree of development of CMD is highly dependent on the geologic history of coal-bearing strata that have undergone disturbance by mining. The geologic history controls the chemical and mineralogical composition of coal and coal-bearing strata (Cecil and others, 1985) and the geologic history is a primary control on pre-mining and post-mining hydrology. Although mining-related environmental degradation of streams occurs throughout the coal fields in the Appalachian basin, CMD is most acute in Pennsylvania, Maryland, Ohio, and northern West Virginia (the northern coal field of this report) where mining primarily occurs in upper Middle and Upper Pennsylvanian strata. It is in upper Middle and Upper Pennsylvanian strata where the oxidation of pyrite results in the generation of sulfuric acid, which leads to acidic mine drainage and the associated leaching of certain metals, particularly iron, aluminum, and manganese (see Brady and others, 1998). In contrast, CMD is relatively rare in the coal fields of southern West Virginia, western Virginia, and eastern Kentucky (the southern coal field of this report) in lower Middle and Lower Pennsylvanian strata. Mining disturbances in lower Middle and Lower Pennsylvanian strata occasionally result in manganese contamination, and even more rarely, minor acidic drainage may occur. In contrast to the notorious CMD problems in the northern fields, water contained in abandoned underground mines in the southern field is often potable, and is sometimes used as municipal water supplies. Thus, the regional and stratigraphic variations in the chemical and mineralogical properties of coal and coal-bearing strata are highly variable. Therefore, long-term goals for this study have been developed as follows:

1) evaluate the geologic controls on the chemistry, mineralogy, and spatial distribution (both regional and stratigraphic) of deleterious substances in coal and coal-bearing strata in the Appalachian basin; 2) develop methodologies that can be used to predict stratigraphic trends in materials that control CMD; and 3) develop methodologies for specific stratigraphic intervals that can be used to predict the regional spatial variability of materials that control CMD.

This preliminary report includes both stratigraphic and regional data on the chemistry and mineralogy of coal-bearing strata in both the northern and southern coal fields of the Appalachian basin.