Chesterfield County, in northeastern South Carolina and bordering North Carolina, has two markedly different sources of ground water. About 20 percent of the county is in the Piedmont physiographic province, where the crystalline rocks beneath a thin weathered zone contain ground water only in fractures. Wells in these rocks generally provide very low yields, often less than 5 gpm (gallons per minute); although there are exceptions—some 50-200 gpm wells have been reported. The chemical quality of water from both types of aquifer—the hard rock and the sand—is suitable for all uses.