Lesson learned

Three adjacent projects raise Mississippi River levee after close call

By Sam Barnes

The rumble of equipment can be heard day and night along a 10-mi. stretch of levee bordering the Mississippi River north of Tallulah.

Advance Construction Services Inc. of Brewton, Ala., is working nearly 24 hours a day on two adjacent levee sections to reinforce the levee system against future flooding. W. G. Yates & Sons Inc. of Jackson, Miss., was beginning the third and northernmost section this fall. All the projects total nearly $20 million.

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David Townsend, construction representative with the U. S. Army Corps of Engineers' Vidalia office, said a flood in the 1970s prompted the corps' long-term investment in the levee-raising initiative.

"The river came very close to topping the levee system, which would have been catastrophic for this area," Townsend said. The corps subsequently began plans to raise the levee through out the area.

Dean Boling, jobsite superintendent with Advance, said the company is working two crews, with the day crew working the longest levee section to the north.

Boling, who supervises the day crew, said approaching the project in such a fashion has enabled the contractor to use the same equipment for both jobs, which "cuts the amount of machinery out here in half" and "saves significantly on the cost of performing the two projects."

Still, an impressive fleet of equipment is rumbling across the cropland that borders the new levee system. Three excavators dig nearby pits that supply dirt for the levee raising, while 11 dump trucks transport the material from the pits to the levee in a continuous procession. Five bulldozers help distribute the dirt once it's placed on top of the levee.

Boling said the success of the operation hinges on the uninterrupted hauling of nearly 4 million cu. yds. of dirt from the three pits, which are less than a mile from the levee sites. The pits were determined to offer the highest-quality soil after soil boring.

"The water table is extremely shallow here, so we had to get a little creative," he added. "We have to dig a ditch around the pit deeper than the pit itself so the water has someplace to drain. We keep it pumped down to that level." The method doesn't keep the soil dry but does keep the hole from filling up with groundwater.

But the method didn't prove impenetrable when cold fronts packed with heavy rains began sweeping through the area in late September.

"We've got a pond out in the middle of one of them," Boling said, adding that working in southeast Texas along the Sabine River has prepared him for working under such conditions. He said the soil was purchased from a local landowner.

After an excavator loads the dirt onto a dump truck, the truck transports the material to the levee, which was stripped of grass.

"We also disk the existing soil before placing the new soil," he said. "It makes the dirt bond together by giving it a rough surface to grab onto."

The corps' Townsend said raising the levee would ultimately result in the widening of the levee base to maintain the same slope. In some locations the new levee pushes out by as much as an additional 140 ft.

"In a few locations, we're having to push the levee into water," Townsend added. "There's a few pits out there that were dug years ago to create the existing levee. They're now small ponds full of water."

To help the new lifts of soil adhere to the existing levee, the crew is "benching" the slopes by cutting stair steps into the soil with bulldozers.

"That way, it keeps it from being a slick surface," Boling added. "Every time we put down a lift of dirt, we cut into it by about 1 ft." As many as 20, 1-ft. lifts are needed in some locations.

Each lift is dumped, spread by bulldozers and compacted with a tractor and dirt-filled pan.

The contractor must adhere to strict 90 percent compaction requirements and an average of 34.8 percent soil moisture (plus or minus 6 percent). By achieving the desired compaction and moisture specifications, the new lifts can compact properly.

Ladner Testing of Jackson, Miss., and the Corps of Engineers test the soil with nuclear gauges to determine compaction and moisture levels. Achieving the desired moisture level has been especially difficult when digging from water-saturated pits.

"We usually have to dry it to get it where it needs to be," Boling said. While making the soil wetter by distributing water from a truck is relatively simple, drying it is the greater task.

"We put the dozers out there to till it up to let the sun dry it out," he added. "We have to be careful not to dry it out too much."

Melvin Boutwell, Advance Construction's night shift (6 p.m. to 5 a.m.) project manager, said working by moonlight has required more time and energy.

"We have seven or eight portable light towers in all of our work areas (around the dirt pits and laydown areas), and of course all of our equipment has lights," Boutwell added. "We have to move the towers around as we work our way down the levee."

Just the fact that the towers have to be maneuvered throughout such a large, sometimes muddy area can create time-consuming problems, he said.

Townsend said the Advance projects should be completed by fall 2005 and will conclude with the "grassing" of the entire site.

"We expect another project to be let in the next couple of months that will take the levee to the Interstate-20 bridge (to the south)," he added.

The W. G. Yates project, which connects to the northernmost Advance section, was just starting in the fall and will follow the same process.

Yates' work will require a sizeable fleet of equipment to raise the levee.

Useful Information

For more information about U. S. Army Corps of Engineers - Vicksburg District projects, go to: http://www.mvk.usace.army.mil/