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Dredging Keeps Vital Waterway Passable in SC

Thu October 27, 2005 - Southeast Edition
Jeff Cronin

More than 1 million cu. yds. of material has been dredged from the Intracoastal Waterway between Georgetown and Charleston, SC, during the past four months.

As part of a regular upkeep to the manmade waterway, the U.S. Army Corps of Engineers let a contract to Enterprise LLC, of North Charleston.

The $2-million project has cleared the way for commercial and recreational crafts that have had to deal with sandbars that limited the waterway’s depth to as little as 6 ft. in some spots.

Army Corps Project Manager Jimmy Hadden said the depth of this portion of the waterway is now between 10 and 12 ft.

Sandbars creep up through natural sedimentation and reach these heights in two or three years.

To remove the material from the bottom of the waterway, crews used a hydraulic pipeline dredge, which Hadden describes as “an egg beater on the end of a vacuum cleaner hose.”

The device is placed over the shoal and chews up the material — which was mainly a soft organic material called pluff mud — and carries it through tubing to a designated disposal site.

Several disposal sites can be found along the length of the waterway and the material was never pumped more than 2,000 or 3,000 ft. away. The contract required the Enterprise crew to remove at least 300,000 cu. yds. (230,000 cu m) of material per month.

Hadden said the material pumped through the dredge is 70 to 80 percent water. The disposal areas are designed to allow the material to settle and lets the water flow back into the waterway.

Hadden said it sometimes takes up to a year for the material to dry out. At that point, crews will break out the iron and will use the material to build up the waterway’s dike system. That part of the job usually calls for bulldozers, pull pans and amphibious excavators.

The waterway remained open during the dredging process. He said vessels could normally pass by the contractor at work, but sometimes the contractor had to move out of the way.

Crews ran into some difficulty during the project when they ran out of room at one disposal area. They were not able to dredge one shoal just south of McClellanville to the desired depth.

Army Corps officials are still deciding how to create more capacity in this area. Hadden said they could work with the county to build new disposal sites or move the dried out material to the beach. As it is a fine material, it is not appropriate for construction purposes, Hadden added.

Depending on the Corps’ funding levels next year, Hadden said dredging this area will be a priority.

But getting enough money to maintain the Intracoastal Waterway has proved to be difficult in recent years, Hadden said.

According to the Associated Press, Congress last year appropriated less than $4 million for the entire 1,200-mi. stretch from Norfolk, VA, to Miami.

Without enough money, “I can’t dredge the waterway,” Hadden said, which could lead to navigational problems for commercial traffic. CEG

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