As used in this article, unless the context requires a different meaning: “Coal refuse” means waste material resulting from the mining and screening or processing of coal. “Coal slurry” means waste water and impurities produced as the result of coal washing and preparation of coal for market, containing a combination of coal, shale, claystone, siltstone, sandstone, limestone, or related materials that are excavated, moved, and disposed of from underground workings. “Mine refuse impoundment” means a mine refuse pile that retains water that has been used in carrying out any part of the process necessary in the production or preparation of coal. “Mine refuse pile” means a pile of coarse or fine coal refuse that is a result of the mining or screening process that may be stacked, spread, or graded and covers 20 acre-feet or more. “Operator” means any person who operates, controls, or supervises a retaining dam or a mine refuse impoundment. “Retaining dam” means an artificial barrier or obstruction that is designed to impound water, coal slurry, or silt (i) to an elevation of five feet or more above the upstream toe of the structure and has a storage volume of 20 acre-feet or more or (ii) to an elevation of 20 feet or more measured at the open channel spillway or from the crest of the dam in a closed system, regardless of storage volume. “Silt” means fine particles resulting from a mining operation, suspended in or deposited by water. “Water” means liquid or slurry resulting from the processing of coal in mining operations.