The Illinois Basin has an extensive history of surface coal mining dating back to the early 1800’s. The Illinois Basin has experienced a resurgence of underground long wall operations with the migration of Appalachia-based coal mining operations over the last decade. This type of mining is conducted under hydraulic roof supports that advance as the coal seam is cut. As the supports advance, the roof collapses behind the cutting head, causing fractures to propagate through water-bearing sandstone formations and resulting in large volumes of fluid infiltrating into the underground workings. Up to 2 million gallons per day have been produced in the southern Illinois mines. The native groundwater contains naturally-occurring elevated chlorides that exceed surface water effluent limitations and are not permitted to discharge to Illinois surface waters. However, the fluid is permitted to be disposed of in Class I non-hazardous wells.