A water-table contour map of the carbonate rocks of central Chester Valley in Chester County, Pennsylvania was constructed based on water levels measured in 104 wells in May and June 1984 , the altitude of 10 springs, and the level reported in 16 wells and one active quarry. The area of carbonate rock underlies parts of East Whiteland, West Whiteland, East Caln, and Caln Townships, the Borough of Downingtown, an the city of Coatesville. Water-level altitudes in the carbonate rocks range from 396 ft above sea level in the western part of East Whiteland Township to 232 ft in Downingtown Borough. (USGS)