Types of Impoundments
Coal Waste Impoundments
Coal waste impoundments are constructed for the permanent disposal of waste coal, rock, and related material as a by-product of coal mining. Coal waste is produced during the cleaning of coal for market, and usually occurs at “coal preparation plants.” The coal cleaning process produces coarse (usually 6-inch or smaller material) and fine coal waste (silt/sand-size particles, usually in a “slurry” with water) as the impurities are segregated from the clean coal. Most coal waste is shale (often called “slate,” “gob,” “refuse,” or by other terms like “reject,” “culm,” “bony,” etc.), but in the development of an underground mine, may include sandstone, siltstone, limestone, etc.
In the mountainous Appalachian coal-mining region, coal waste is deposited in embankments and impoundments. Embankments are typically located in valleys close to the preparation plant and typically comprised of coarse coal waste. Impoundments are constructed by building a retaining embankment with coarse coal waste across a valley to create a fine coal waste collection basin. The water transporting the fine coal slurry is often decanted from the top of the impoundment and repeatedly recycled to the preparation facility to “wash” more coal.
Coal waste embankments and impoundments are subject to the regulatory requirements of OSMRE and the Mine Health and Safety Administration (MSHA). These regulatory programs complement each other, with the intent of MSHA to provide for the health and safety of miners, and the intent of OSMRE to protect the public and to limit environmental effects.
OSMRE's Appalachian Region (AR) is involved with all of the OSMRE regulatory issues involving coal waste, including inspections, oversight, citizen complaint investigations, coordination with MSHA, and program amendments. The AR is conducting evaluations with the States of selected coal waste impoundments in the region where there is a potential for leakage or failure of the impoundment into subjacent underground mine works. AR scientists and engineers have worked closely with MSHA to develop action plans from recommendation of the 2002 National Science Foundation, National Research Council report on coal waste impoundments. The AR has also been involved in an experimental practice at a Kentucky coal waste impoundment site that was successfully reclaimed into a recreational lake and community park.