International Dredging Review

International Dredging Review

Proponents of deepening Charleston Harbor to beyond the existing 45-foot authorized depth have dubbed the project the “Charleston Harbor Post-45 Project.” The deepening will allow the port to better serve the post-Panamax ships that will begin plying the seas in greater numbers when the Panama Canal expansion is complete next year.

A fully loaded post-Panamax container ship will draw between 48 and 52 feet of water. These ships are able to call to the Port of Charleston today under restricted conditions associated with their sailing draft and the tidal stage of the harbor. The Port of Charleston offers a maintained depth of 45 feet at mean low tide and 47 feet in the entrance channel. This allows vessels with a 43-foot draft 24-hour access to the port. A five to six-foot tidal lift provides even deeper access for several hours during the day allowing ships with a draft of 48 feet access to the port for two hours; 47-foot draft for six hours; 46-foot draft for 10 hours 45-foot draft for 14 hours and 44-foot draft for 18 hours. 


An overview of Charleston Harbor shows the location of the terminals and other features. There are 44.6 miles of channel three turning basins and one anchorage basin. (Courtesy South Carolina State Ports Authority)

The channels are from 500 feet to 1000 feet wide with tidal currents running at an average of 1.5 knots. There are no air draft restrictions. Ships sailing to the terminals cross under either the Ravenel Bridge which has an air draft of 186 feet or the Don Holt Bridge with an air draft of 155 feet.

“Deepening should require removing an estimated 30 to 40 million cubic yards of material and the depth of the selected plan will be the greatest factor affecting the amount of material to be dredged” Bret Walters chief of the Charleston District planning branch said.

“The integrated Draft Feasibility Report and Draft Environmental Impact Statement which will be released to the public in late summer 2014 will detail the selected plan. Other still-to be-determined factors such as widening berthing and maneuvering features will also affect the amount of material to be dredged” Walters said.

As of the beginning of January all the physical data collection had been completed for the feasibility study and project managers at the Charleston District were analyzing the information to include in the draft environmental impact statement (DEIS) planned to be ready for public review this summer. The Final EIS (FEIS) and Final Report are on track for completion in spring 2015 and the final Chief of Engineers report is expected in September 2015.


Sampling has not revealed any soil characteristics that will require special dredging equipment blasting or treatment for contaminants. (Corps of Engineers photo)

Decisions about placement/disposal and beneficial use of dredged material are highly dependent on the volumes and locations where material will be excavated Walters said. These decisions will not be made until an alternative is selected. It is anticipated that several upland sites and an ocean disposal site will be used and some material is expected to be usable for beneficial uses near the harbor he said.

“Testing performed to date indicates that no significant contamination will be encountered within areas that would be dredged for a deepening project” Walters continued. “No special handling or disposal requirements related to contaminants are anticipated” he said.

A wide range of dredging equipment is expected to be used in the deepening. Anamar Environmental Consulting and Athena Technologies Inc. performed widespread core sampling and strength testing and interpretation of the results are happening now. But highly specialized equipment to dredge hard material is not anticipated nor is the need for blasting Walters said.


The Charleston District created this icon to depict the deepening project.

The project began with a Congressional addition to the President’s fiscal year 2010 budget which allowed the Charleston District to complete a reconnaissance study to determine if there was federal interest in conducting a feasibility study. The reconnaissance report completed in July 2010 found that a large percentage of vessels calling in Charleston are tiderestricted and that it would be in the national interest to do the feasibility study.

On June 20 2011 the Corps Charleston District and project sponsor the South Carolina State Ports Authority (SCSPA) signed the feasibility cost-sharing agreement (FCSA) which stated that the study would be cost shared 50/50 between the two entities and conducted by the Charleston District. The study will identify the National Economic Development (NED) plan that maximizes the net benefits to the nation as a result of deepening the federal channel.

The District’s engineers planners surveyors and project manager are working along with many environmental resource agencies to analyze a full array of alternatives to determine what depth the Corps will recommend to Congress for authorization.


Field workers from Anamar collecting sediment samples in Charleston Harbor. They collected and tested sediment samples throughout the harbor to determine if dredging and disposal will have any negative impacts on the environment. The results will help the Corps determine where and how sediment from a deepening can be disposed of. (Corps of Engineers photo)

As part of the Corps of Engineers’ Civil Works Modernization Initiative the Charleston District along with division and headquarters subject matter experts developed a plan that targets completion of the feasibility study chief’s report by September 2015 at a cost of $13 million or less. This was shaved down from an original estimate of a five- to eight-year process costing between $18-20 million. The Post 45 project was also named in the president’s “We Can’t Wait” initiative for critical national infrastructure projects. The South Carolina legislature has also appropriated funds for the port upgrades needed to make Charleston post-Panamax ready which includes cranes capable of loading and unloading post-Panamax ships and docks engineered to handle the bigger cranes in addition to increased channel depth and sufficient channel width and turning basin size.

At the end of the feasibility phase if the study recommends a deepening of Charleston Harbor the Charleston District will move to the preconstruction engineering and design phase– an approximately two-year undertaking. If Congress authorizes construction of the Post 45 project and provides funds to do so the District will enter the construction phase which could take approximately four years to complete the deepening of the 44.6 miles of channel three turning basins and one anchorage basin that make up the Charleston Harbor project.

The Corps has maintained Charleston Harbor for more than 130 years and has dredged it every year during that time to ensure the channel is at the required federal project depth spending approximately $10 to $15 million and removing two to three million cubic yards of maintenance material from the harbor floor each year. Construction to deepen the harbor to the now federally authorized 45-foot depth began in 1999 and was completed in 2004.