Coal preparation refuse
Refuse material is generated in the coal preparation process. Disposal of the refuse is regulated by federal and state laws. Coarse refuse (particle sizes generally greater than 1/3 of an inch in size) are called gob (which means “garbage of bituminous”). Gob is generally transported from the plant by truck or conveyor belt back to mining areas for fill and other uses as allowed by regulations. Fine refuse is carried in suspension as a water slurry. Slurry is usually piped into a specially designed impoundment called a slurry pond (NRC, 2002). In the pond, suspended fine sediment slowly falls out of the water column and accumulates on the bottom of the pond. The pipe from the plant may be moved to different positions in the pond for optimal filling of the available space. Clarified water (upper part of the settled water column) from the ponds is recycled through the preparation plant. Ultimately the ponds are filled, and then capped with soil according to federal and state regulations. Further treatments may be used depending on the chemistry of the material as required by law. More information about the environmental impacts of preparation wastes can be found in the coal and environment section of this web site.