Berkeley County is underlain by carbonate rocks, upon which karst topography has developed, and by noncarbonate rocks. Ground-water levels tend to follow seasonal trends, and fluctuate more in carbonate areas than in noncarbonate areas. Well yields of greater than 100 gallons per minute are possible from the carbonate rocks, but are unlikely from the noncarbonate rocks. The largest springs, which yield more than 2,000 gallons per minute, are located in the carbonate rocks and are typically on or near faults or the limestone-shale contacts. Ground-water-flow velocities in the carbonate rocks ranged from 32 to 1,879 feet per day. Recharge was estimated to be about 10 inches per year for a 60-square-mile area of carbonate rocks. Specific yield for carbonate rocks ranged from 0.044 to 0.049. Estimated transmissivity values for carbonate rocks ranged from 730 to 9,140 feet squared per day. Concentrations of the following constituents exceeded the maximum and secondary maximum contaminant levels set by the U.S. Environmental Protection Agency in ground water from at least one site: iron, manganese, nitrate, fecal coliform and fecal streptococcal bacteria, pH, total dissolved solids, and chloride. Analyses of the ground water indicated that the following organochlorine and organophosphate insecticides were present in detectable concentrations: chlordane, DDE, DDT, diazinon, dieldrin, endosulfan, endrin, heptachlor, heptachlor epoxide, and malathion. Triazine herbicides that were present in detectable concentrations were atrazine, cyanazine, and simazine. Radon concentrations ranged from 92 to 1,600 picocuries per liter. Ground water from four springs in the carbonate rocks was analyzed for 36 volatile organic compounds. None of the compounds were present in detectable concentrations.