A study of the effects on water quality of coal mining in the basin of the North Fork Kentucky River shows increases in the mean annual total dissolved solids concentrations from about 8 to 50 milligrams per liter. It shows that the Hazard Number 9 coal seam produces the largest quantities of acid and sulfate. The study also shows that most of the acid mine drainage is neutralized by carbonate minerals or is replaced by exchangeable bases from the aquifer materials before it reaches the streams. The generation of sediment is probably the most damaging effect of strip mining on water quality in the basin. (USGS)