By Army Sgt. Ann Knudson
Special to American Forces Press Service

April 24, 2009 - The North Dakota National Guard finished pulling out two barrier systems that proved to be useful new tools in the fight against recent flooding in the state. The flood threat has gone away, and the rapid-deployment flood walls, known as RDFWs, that National Guard members has installed south of Minot are no longer needed, officials said.

RDFWs act as a flood barrier through a series of interlocking plastic dividers. The dividers lie flat for shipping, and when used, unfold into a grid of square cells, much like the grid on a fluorescent light. The 4-by-4-foot cells interlock end to end to form a line, and up and down to form a wall. The grids are 11 inches high per layer. The internal cells line up with each other vertically, forming a column, so sand can be poured in after several layers are in place.

"It all holds together throughout," Army Sgt. Aaron Wall, the noncommissioned officer in charge for the first RDFW project, said. "The ends are capped with sandbags, and we'll put sandbags two high on the upstream side." Wall is a member of the 164th Engineer Battalion's Forward Support Company and an officer in the Minot Police Department.

Wall and nine other soldiers put up the first RDFW south of Minot, on the upstream side of the bridge over First Larson Coulee. The bridge is in an area called Crystal Springs. The RDFW was a precautionary measure to keep the bridge passable in case the stream in the coulee rose to road level.

As it turned out, the water did not get that high, but the exercise did show how much training was needed to use the RDFW, how many soldiers it took, and how fast it could be done. Soldiers said the RDFW didn't take a lot of training to put up. "We read the directions out of the box and watched a five-minute video clip," Wall said.

It didn't take much time, either. About 10 soldiers started the project at 10 a.m. By 7 p.m., they had a wall 400 feet long, 4 feet across and 33 inches high filled with sand and leveled off. They also had placed sandbags at the ends and on the upstream side for reinforcement.

"We could have been done even sooner, but we spent a little time waiting for sand and sandbags," said Army Spc. Paul F. Vining of Minot, a member of the 164th Engineer Battalion's Forward Support Company. Vining is an emergency room nurse at Trinity Hospital.

Here's the math: A filled sandbag weighs about 40 pounds. A cubic foot of sand weighs 100 pounds. The RDFW was the equivalent of about 12,000 sandbags. A two-person team can fill and tie one sandbag a minute, so a team of 10 would take a little more than three 12-hour days to fill and tie 12,000 sandbags.

As a very rough estimate, it takes as many work hours to palletize, load, drive, unload and heave sandbags into place as it does to fill them. Thus, it would have taken about a week to equal the RDFW with sandbags, officials said.

"It went pretty well overall," Wall said. "The most time-consuming part was that you need equipment to finish it up, but you'd need that with [Hesco barriers], too. We used a payloader on the first RDFW and a cement truck for the second."

"Those [RDFWs] were nice," Vining said. "We used them on 35th Avenue Southwest, which turns into County Road 14. Water was across the road about 40 feet wide. We didn't want to put the RDFW in the middle, in case the water washed it away before we got the sand in, so we used sandbags in the middle and the RDFW on the ends. It worked real well."

Sandbags are cheap, and better for use on bumpy ground, steep slopes, or when there are more people than equipment. However, like Hesco barriers, the RDFW can save time on flat surfaces, officials said.

(Army Sgt. Ann Knudson serves with the North Dakota National Guard.)