The U.S. Army Corps of Engineers (USACE) has proposed dredging a 13-mile reach of the St. Johns River navigation channel in Jacksonville, Florida, deepening it to depths between 50 and 54 feet below North American Verti- cal Datum of 1988. The dredging operation will remove about 10 feet of sediments from the surficial aquifer system, includ- ing limestone in some locations.