Air may not seem like an effective barrier for some things, but when coupled with a trailer-mounted blower and heat, it provides a very efficient barrier and environmentally friendly way of clearing land with little smoke. The U.S. Army Corps of Engineers, Savannah District is using this method also known as “air curtain burning” as part of the reactivation process for one of its dredge disposal sites in Georgia.
The 130-acre area officially referred to as Dredged Material Containment Area 1N, located on Onslow Island, once consisted of 95 acres of heavily vegetated and wooded land. After clearing the area, workers for the Savannah District used the air curtain for quick, clean disposal of piled-up vegetation.
Air curtain burning involves a trailer-mounted air blower that generates a barrier or curtain of air over a fire burning pit. The process limits the amount of smoke released into the air during the burning process. The curtain of air traps the smoke and forces it back into the hot, burning fire to be combusted instead of escaping into the atmosphere.
“The process is more efficient because the air being blown over it makes it burn faster and at a higher temperature, so it’s less burning time and less smoke, which makes for a much cleaner burn,” said Corps Civil Engineer Jessica Power. “Once the waste flows through the burner, the ashes are also a very useful soil additive.”
The project, which began in October, aims to rehabilitate the disposal area back into a functional state to store dredged material and create habitat for a variety of birds and other species.
“The site, which is owned by U.S. Fish and Wildlife Service, was used by the Corps of Engineers as a dredge disposal area years ago but has not been used for dredging in almost 15 years now,” said Power.
As a result, the area had become overgrown with vegetation, including many invasive species. The USFWS had been using the site for sand mining and equipment storage until construction started last October.
Now that the land has been totally cleared, Power said the existing perimeter dike, or outer surrounding wall of the disposal site, will be raised to a more uniform height to gain additional capacity to contain Savannah Harbor dredge material. By restoring the site, the Corps will gain around 600,000 cubic yards of sediment storage capacity.
“This increased capacity is very important for the Savannah Harbor Expansion and all dredging projects,” said Power. “It helps to keep costs down on dredging contracts, because contractors don’t have to pipe dredge material as far.”
As part of an agreement with the USFWS, half of the area will be used as a water fowl wildlife sanctuary. This includes improving the existing bird island to create an optimal habitat for bird nesting.
“Currently there are many small hills and excavation cuts on the land, some of which are now overgrown and ponding with water, so our next step is to smooth the existing bird island and its slopes out to create a more suitable environment for the birds,” said Power.
A ditch will also be added to provide a protective barrier to deter other animals from inhabiting the area. The area surrounding the bird island will be closed off and filled with water, creating an island for the bird nesting area.
The project is scheduled for completion in June 2014.
View video footage of air curtain burner in action: http://youtu.be/cHrWcwUyt2s.