Daylighting (strip mining of coal seams previously deep mined) operations are being conducted on the Anna S Mine, that underlies about 850 acres that are drained by three major discharges. The Hunter Drift drains an underground area of about 400 acres, the Anna S 1 main entry, an area of 330 acres, and Mitchel 2 discharge an area of about 120 acres. As of August 1, 1979, about 55 acres (15%) had been daylighted in the Hunter Drift basin, about 15 acres (5%) in the Anna S main entry basin and about 30 acres (25%) in the Mitchel basin. The acidity of the Mitchel 2 discharge changed the most, from 176 milligrams per liter (as CaCO3) in 1975-76 to 1,190 in 1978-79, an increase of 580%. The acidity of the Hunter Drift discharge increased from 348 milligrams per liter during 1975-76 to 710 milligrams per liter during 1978-79, an increase of 100%. The acidity of Anna S 1 increased about 45%.