“Invisible” Wall Protects Red River Valley
by George Fryklund, P.E. & and Jennifer Reeder
During initial construction, both vertical imbeds and the metal sill plate are joined with the concrete foundation, which is laced with reinforcing bar.
“Our downtown district was basically destroyed,” says Mayor Lynn Stauss of the Red River flood that devastated East Grand Forks, Minnesota in 1997. “The sandbags and levees just didn’t hold; we couldn’t raise them fast enough.”
Only eight homes in East Grand Forks were unaffected by the flood. The water level of 54-feet reached the top of handrails on the Demers Ave. Bridge, and four feet of water submerged the city’s Main Street. Flood damage was estimated at $500 million.
“The river can be harmful one season of the year, but the rest of the time it should be enjoyed. We decided to embrace the river by facing the downtown district towards it, since people like to look at things of beauty,” Stauss says. “That’s where the invisible wall came in.”
The “invisible wall” Stauss mentions is actually a removable flood wall called the Invisible Flood Control Wall (IFCM), a patented product distributed in North America by New England-based Flood Control America. Stauss says he and other city planners saw the wall as a way to solve the problem of how to protect the community from further flooding while revitalizing and preserving the quality of life normally enjoyed by the city’s citizens and visitors alike. A primary focus was the main boardwalk that overlooked the river and featured a number of riverfront restaurants and stores. The flood, of course, had devastated that important economic feature of the community.
City Engineer Gary Sanders, who refers to the river’s boardwalk as the “heartbeat” of the community, suggested the use of the invisible wall during the planning meetings that ensued. Sanders says he felt the invisible wall was more positive than wall closures because it could promote the “asthetics and liveability” of the community, since the wall is only erected in the event of a flood. Patented 20-foot sealed, interlocking hollow aluminum planks “stack” on top of a sill plate integrally constructed on a permanent concrete foundation. Posts and pin-mounted diagonal braces provide additional support, and the “interlocking” planks create a unique “redundant” feature as well.
In the case of the IFCW™ installation at East Grand Forks, intermediate and vertical parting supports bolt into anchor devices mounted deep in a concrete wall base. When needed, the 20-foot sealed (horizontally) and extruded aluminum planks stack between them. (Additional support for walls over 8-feet in height, are provided by pin-connected diagonal braces with a horizontal tension rod to transfer the load to post base anchorage.) A final step is tightening down the vertical parting support anchor bolts and adjusting vertical hold-down clamps over the top of the highest aluminum plank. The vertical hold-down clamps squeeze the horizontal seals tightly into the plank mounting surfaces.
The aluminum planks weigh less than five pounds per foot. “I can lift one section by myself and put it in place,” says Saunders. An interesting aspect of the design is that as the floodwaters rise, the planks fill with water, which increases stability and working weight. Additionally, an internal diaphragm in the plank doubles the strength of the component as the horizontal seal snugs onto the mating plank interlocks.
Construction at East Grand Forks occurred from September of 1998 to March of 1999, providing over 980 linear feet of floodwall protection up to 14 feet in height. Two main gate abutments are featured at Demers Ave. for a 60-lineal foot by 14-vertical foot closure.
“We would have a 12-foot concrete wall there right now if it weren’t for the invisible wall. Many people comment on how attractive the approach to the riverfront is. They don’t feel like they’re driving into a flood control project,” says Sanders.
Since project completion, East Grand Forks has experienced close to $20 million in investment, including a new $8 million Cabela’s; restaurants like Applebee’s, the Blue Moose Café, and Whitey’s; and reconstruction of the city’s Riverwalk Center. The city is in Phase 1 of a four-year project to develop the 2200-acre Red River State Recreation Area where about 700 homes were demolished; it will feature an extensive trail system and a 360-unit campground, according to plans.
Because of the East Grand Forks project, the IFCW was awarded the “Seven Wonders of Engineering in Minnesota Award for Distinguished Engineering Achievement 2000” by the Minnesota Society of Professional Engineers, and was recognized by the U.S. Dept. of Commerce Economic Development Administration as one of its five major “success stories” in the 20th century.
Though East Grand Forks was the first U.S. city to sign on with the new technology, its Red River floodplain neighbors in Fargo, North Dakota, weren’t far behind in implementing the invisible wall where it was later put to the test.
Fargo also suffered a record flood during the same 1997 flood that devastated East Grand Forks. For example, Oak Grove Lutheran School itself sustained an estimated $3.5 million in damage. Temporary earthen dikes and sandbagging had failed to protect the school and the town. The public subsequently spent an estimated $7 million on restoration and flood protection, and $20 million on improvements.
According to City Engineer Mark Bittner, city officials considered acquiring the school and relocating it away from the river, but instead hired a local architect to design flood barrier access points to the school. Then they invested in five invisible wall closures four to seven feet in height and 10 to 17 feet in width to provide access from sidewalks to the school, which has several hundred of feet of brick-clad concrete wall.
He says a selling point was that the invisible wall offered permanent, secure protection without permanent barriers, so that the school was easily accessible when the river wasn’t flooding.
Construction on the project in Fargo occurred from July of 2000 to November of the same year. In the spring of 2001, the Red River flooded again, and the wall was put to the test. “It worked like a charm,” says Bittner. “We’d just finished construction on it we were just in time.”
Senior Engineer Lynn Brilz says that the invisible wall was quickly erected when the flooding began because the crew had previously practiced a “dry run” to put in the flood panels and become familiar with the system.
“When the flood came, we had half a dozen crew members (erect it) in 1 hour and 15 minutes,” Brilz says. He credits the wall with not only protecting the school, but also preventing a breach in a sanitary source system in an adjacent neighborhood. In fact, city officials in Fargo were so pleased that a second project was contracted to protect the Fargodome with 110 lineal feet of 8.5 feet high wall.
“A permanent structural wall would have detracted from the river; with the Invisible Flood Control Wall it’s the best of both worlds. The best aspect is the permanence it’s more secure than temporary earth dykes. But the other advantage is that it allows us to utilize facilities for the 90 percent of the time we don’t need protection,” Bittner says.
“I look at people eating on balconies on the river if we didn’t have the invisible wall, they wouldn’t be there,” Sanders says. “It’s been a real plus for us.”
For more information, visit: www.floodcontrolam.com.
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