Most wells drilled in valley bottoms are adequate for a domestic supply. About three-quarters of the wells drilled on hillsides and one-third of the wells drilled on hilltops are adequate for a domestic supply. Wells drilled 200 feet or more below the level of the principal valley bottoms may yield enough water for small municipal or industrial supplies. Few wells in this county drilled less than 300 feet below the level of the principal valley bottoms will yield salty water, except in the small corner of the county north of Pine Mountain, where salty water can be found in the range of 200 feet below the principal valley bottoms. Wells drilled in the Pine Mountain area that reach limestone may yield as much as several hundred gallons per minute. Groundwater obtained from most drilled wells in this area is soft but contains noticeable amounts of iron, except north of Pine Mountain, where the water is moderately hard. Some of the most productive springs in eastern Kentucky are found along Pine Mountain in Harlan County. Limestone springs can yield more than 50 gallons per minute but generally yield less than 10 gallons per minute.