CHARLESTON, S.C. -- A dredge, appropriately named Dredge Charleston, a daily crew of 53 workers, and heavy earthmoving equipment worked 24 hours a day for seven weeks constructing a landmark legacy of the Charleston Harbor Post 45 Deepening project: the restoration of Crab Bank. Crab Bank is a bird sanctuary located in the Charleston Harbor near the shoreline of the Old Village in Mount Pleasant.
The project is a landmark legacy of Post 45 because the rest of the $550M deepening project is underwater and that massive investment is not visible to the public. In the case of Crab Bank, it has now become a feature of the Charleston Harbor that can easily be seen and noticed from as far as the Arthur Ravenel Jr. Bridge. Beneficially using material from the deepened channel restored 32 acres of prime nesting grounds, giving shorebirds and seabirds much-needed habitat for increasing their populations this spring and those to follow.
Because placing the dredged material on Crab Bank was not the least-cost placement method, a non-federal sponsor was needed to make the concept a reality. The South Carolina Department of Natural Resources (SCDNR) stepped up to fill that role and share in the costs of the project. If not for their commitment and our partnership together, this sandy material would have wound up sequestered in the ocean placement site and this seabird sanctuary lost for good.
Although the actual construction only took a few weeks, the idea came about years ago when the Post 45 project delivery team was trying to identify potential projects to maximize the beneficial use of the available sandy dredged material from the harbor deepening. Crab Bank rose to the top.
“Nine years ago, Crab Bank was just a concept, three years ago SCDNR stepped up to make it a reality, and this spring it becomes vital habitat and nesting grounds for shorebirds. It is rare in an engineer’s career to see a project from concept to completion. Seeing this to completion is very rewarding,” said Brian Williams, one of the project managers.
Approximately 660,000 cubic yards, or 66,000 dump truck loads (one dump truck carries about 10 cubic yards), of material created the crescent-shaped footprint, which can be seen from the Ravenel Bridge, Alhambra Hall, or other waterfront spots on the harbor side of Mount Pleasant.
“The work is fascinating to see”, said Jeff Livasy, project manager. “The hydraulic cutterhead suction dredge sucks up the material from the channel floor, similar to a vacuum cleaner, and it is pumped onto the island through various types of pipe. Once the material is on the island, bulldozers begin shaping the material.”
“This is a little different than a beach renourishment project,” said Chip Forbes, the field engineer for Norfolk Dredging Company, the contractor working for the District. “We usually have our guys smooth out the sand perfectly, so it is flat and even terrain, but in this case, the birds do not want that. Different birds like different terrain so this has been fun creating something with lumps, bumps and some flat surfaces.”
The natural isolation of the island keeps the birds and nests safe from predators. Over fifteen different species of bird have been spotted nesting on the island in previous years. The number of shorebirds and seabirds’ nests are declining each year,” said Janet Thibault, a wildlife biologist for SCDNR. “Having places for them to have refuge is really important. Around March or April, the birds will come back, find mates and build nests. So, I’m just really excited to see this project happening.”
This one-time placement of material could have as much as a 50-year life span, but in such a dynamic environment we know the footprint will be reduced and change each year. Mother Nature will play a large role in the life of Crab bank. SCDNR will monitor the island each season with special cameras. This live webcam will also allow the public to view the island’s inhabitants in real-time.
Visitors are not allowed on the island during the official nesting season which runs from March 15 - Oct. 15 each year. During the remaining months, the island is only open below the high tide line, and pets are prohibited.
With most of the island inaccessible, exploring the island by kayak or motorized boat is a fun way to see the activity. We do ask that visitors avoid generating boat wakes because that aids with erosion and we want to protect the island as much as we can.
USACE is proud to have partnered with the SCDNR on the restoration of this vital habitat and we will be excited to “Welcome Back the Birds” with a public event this April. Stay tuned to the social media channels of both agencies this spring for more information.