The proposed Bulldog coal mine needs up to 20,000 gallons a day of treated water for drinking and other purposes, including shower houses where coal miners, per regulations, clean up at the end of their shift. Sunrise's Indiana mine uses on average 13,000 gallons a day of treated water.
Sunrise expects the Bulldog mine will also need 350,000 gallons of raw, or untreated, water per day, initially, and up to 500,000 gallons a day at full capacity, according to Suzanne Jaworowski, communications director for Sunrise. And the company has also asked the village of Homer to provide that water as well, but the village board has not started to consider that request yet.
The raw water is sprayed in the underground mine to keep down coal dust, and it's used above ground to wash the coal after it's brought to the surface.
Raw coal has rock and clay attached to it when it comes to the surface, and the primary purpose of coal washing, which can require large amounts of water, is to remove the rock, clay and mineral impurities that reduce the heating value of coal and contribute to air emissions when it's burned, according to a report by the Office of Surface Mining Reclamation and Enforcement in the U.S. Department of the Interior.
According to Sunrise officials, its coal-washing process uses a closed-loop system in which some water is reused. Coal is brought to the surface and into a wash plant where water is added, putting the coal in a slurry form that's pumped throughout the plant in a coal-rock separation process.
About 70 percent of the washed coal is shipped to customers, and 15 percent goes to a course gob pile for permanent storage. Course gob includes the rock and other unusable material separated from the coal. The remaining 15 percent, which includes all the waste water from the plant and coal fines — powdery form of coal leftover in the process — is pumped into a slurry pond where the coal fines settle to the bottom, and the clear water is sucked out and pumped back to the wash plant for reuse.