Your operation’s purpose is to use water and chemicals to remove impurities from the excavated coal prior to shipping. The wastewater left over from the cleaning is called coal slurry or coal sludge.
South Wings (read the section on coal slurry): http://www.southwings.org/our-work/coal-slurry-ash/
Public Health & Coal Slurry: http://auroralights.org/map_project/theme.php?theme=prenter&article=15
Appalachian Voices: http://appvoices.org/end-mountaintop-removal/community/
The Dominion: News from the Grass Roots: http://www.dominionpaper.ca/articles/2093
Fox News: http://www.foxnews.com/us/2010/10/10/toxic-coal-sludge-pollutes-ky-town-years-later.html