JEKYLL ISLAND, Ga. – Conventional wisdom warns against building on shaky ground, but the future of Georgia’s coastline could very well rest on 5 acres of “pluff mud.”
(Watch a video about the pilot project here.)
Workers with Cottrell Contracting of Chesapeake, Va., are currently wrapping up a three-month-long dredging pilot project, which seeks to find cost-effective, environmentally friendly disposal methods for this especially silty, watery material that comprises much of Georgia’s portion of Atlantic Intracoastal Waterway (AIWW).
The project will deepen a channel near Jekyll Creek to 10 feet, placing 5,000 cubic yards into a nearby marsh and the other 220,000 cubic yards into a naturally scouring “deep hole” in St. Simons Sound. Contractors expect to complete the project by the end of June.
“The closest disposal options are about seven miles offshore and that’s very costly,” said Jonathan Broadie, project manager for the pilot project and acting chief of navigation, U.S. Army Corps of Engineers, Savannah District. “So not only are we finding a place to put the material but we’re also finding ways to help protect the marsh.”
The experienced contractors quickly discovered this wasn’t a typical dredging gig and had to adjust throughout the project.
“It’s different because it is maintenance material that is extremely soft and silty and high liquid,” said Burt Moore, chief of dredging for Savannah District. “It doesn’t like to stay in place, it likes to move.”
Moore, who has more than 25 years of experience working with the dredging industry, described the difficulties contractors faced. Not only must they position the dredge safely in the waterway but they must also wait for favorable tides to dredge. Plus, they need to contend with the wind, which could easily undo a day’s work.
Contractors placed porous coconut coir logs along the border of the designated 5-acre portion of the marsh to retain the dredged material and allow marsh grasses to adapt to the new level, which was anywhere from 2 inches to a foot higher in elevation.
Scientists and researchers with Georgia Southern University and the University of South Carolina will monitor the marsh and associated wildlife periodically over the next few years to ensure the health of the marsh and the associated ecosystem.
The deep water placement portion of the pilot project had a different set of challenges.
According to Moore, contractors had to run a 40,000 foot sub-line to deliver the material within 3 feet of the bottom of the deep hole. They are also adding sediment tracers to the dredged material to ensure it actually makes it to the bottom.
Researchers with LG2 Environmental, along with USACE Savannah District survey team experts will use the tracers to study how the material naturally disperses in the surrounding areas and determine if this disposal method is viable for future projects.
If successful, the thin layer placement dredging technique, which has been used in Maryland, New Jersey and Louisiana, could be used throughout Georgia’s Atlantic Intracoastal Waterway as an environmentally sound, cost-effective method that also bolsters the state’s coast against the negative effects of sea level rise and climate change.
After the pilot project wraps up at the end of June, three other troublesome portions of the AIWW including Buttermilk Sound, Hell Gate and Fields Cut, will be dredged.
Other partners in the project include U.S. Army Corps of Engineers, Jacksonville District, Jekyll Island Authority, The Nature Conservancy, the Georgia Department of Natural Resources, U.S. Fish and Wildlife Service, the U.S. Environmental Protection Agency and the National Oceanographic and Atmospheric Administration.
~ Jeremy S. Buddemeier, Corporate Communications Office