Bed rock in the Red Oak area consists of shale, siltstone, and sandstone of the McAlester and Savanna Formations of Pennsylvanian age. Water in bedrock occurs in bedding planes, joints, and fractures and is confined. The potentiometric surface generally is less than 20 feet below the land surface. Wells yield enough water for domestic and stock use, but larger amounts of ground water are not available. Ground water commonly is a sodium or mixed cation carbonate/bicarbonate type with dissolved-solids concentrations ranging from 321 to 714 milligrams per liter. Although variable in quality, ground water generally is suitable for domestic use. No relationship between water chemistry and well depth or location is apparent. Brazil Creek, the principal stream in the area, has no flow 15 percent of the time, and flow is less than 1 cubic foot per second about 25 percent of the time. Water in Brazil Creek is a mixed cation carbonate/bicarbonate type. Dissolved-solids concentrations in Brazil Creek upstream from areas of old and recent mining ranged from 31 to 99 milligrams per liter with a mean of 58 milligrams per liter, whereas concentrations downstream from the mine areas ranged from 49 to 596 milligrams per liter with a mean of 132 milligrams per liter. Water in Brazil and Rock Creeks had concentrations of cadmium, chromium, lead, and mercury that exceeded maximum contaminant levels established by the U.S. Environmental Protection Agency at least once during the 1979-81 water years. Maximum suspended-sediment discharge, in tons per day, was 2,500 for Brazil Creek and 3,318 for Rock Creek. Silt-clay particles (diameters less than 0.062 millimeter) were the dominant sediment size. A significant hydrologic effect of surface mining is creation of additional water storage in mine ponds; one such pond supplies water for the town of Red Oak. Other effects or potential effects of surface mining include changes in rock permeability and ground-water storage, changes in drainage patterns, and changes in the chemical quality and sediment loads of streams.