With the deepest water in the South Atlantic, Charleston offers a maintained harbor of -45 feet (13.7 meters) of depth at mean low tide throughout the main shipping channel and -47 feet (14.3 m) in the entrance channel. A five to six foot tidal lift provides even deeper access for several hours during the day. Harbor deepening to 52 feet is currently underway; the following chart illustrates Charlestons current big ship handling capability throughout the day:
Vessel Movement Hours Per Day
Channel Depth (mean low water):
Entrance Channel 47 ft (14.3m)
Harbor channel and dockside 45 ft (13.7m)
Soft mud bottom
Minimum 500 feet (152m)
Maximum 1,000 feet (304.8m)
Average 1.5 knots.
Columbus Street Terminal has no air draft limitations. Vessels access the ports largest facility, the Wando Welch Terminal, as well as the new terminal under construction at the former Navy Base, by sailing underneath the Ravenel Bridge, which allows for 186 feet (56.7 m) of vertical clearance at mean high water. Ships sailing to North Charleston Terminal transit underneath the Don Holt Bridge, with 155 feet (47.24 m) of air draft.