From introduction: The U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, conducted a 1-year study to determine the effects of proposed deepening of the navigation channel on the surficial aquifer. A specific objective was to determine the degree of interconnection that exists current between the limestone adjacent to the river and the limestone in the riverbed that is to be dredged.

"Duval County in northeastern Florida and adjacent to the Atlantic Ocean contains approximately 840 square miles of which approximately 80 square miles are covered by water. The county is drained by three major rivers, the St. Johns, Nassau, and St. Marys. In addition, the coastal areas are drained by numerous small streams that empty into the Intracoastal Waterway or the Atlantic Ocean."