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Flood Wall at Iowa State University Passes the Test of Recent Flooding

STORY COUNTY, IA – The Maple-Willow-Larch Resident Halls, located on the campus of Iowa State University (ISU), provide housing for nearly 1,600 students. The three high-rise buildings surround the Commons, a two-story building, where offices, study areas, the dining center, and a convenience store are located. On July 9, 1993, floodwaters entered the complex at various locations and caused extensive damages to the Commons and ground floors of each building, which included laundry rooms, guest apartments, elevators, and mechanical rooms.

Squaw Creek and Skunk River surround the city of Ames and Squaw Creek runs adjacent to the Maple-Willow-Larch complex. Before the 1993 Great Midwestern Floods, major storms brought constant rains and caused the creek to overflow and spill into the low-lying areas and the resident complex.

At most, floodwaters would push into the nearby parking lot of the complex. The 1993 Midwestern Floods resulted from an unusual weather pattern which caused substantial rainfall coupled with an overly saturated ground from the previous winter and spring moisture. Every river and tributary in the state was filled beyond capacity. There were only about 13 days without measureable rainfall somewhere in Iowa between April 23 and September 1, 1993.

“During the storm, floodwaters reached up to five feet in the lower level of the Commons. It came up really fast. At the time, I worked with construction and maintenance for the facility and saw tables floating. Trays with water and milk cartons still on them were in the water. The bread truck had just made a delivery so loaves of bread were floating everywhere. I had to wade through the water to shut off the gas valves, which was no easy task since the valves were under water,” said Construction Manager, Leroy R. Brown, with ISU Facilities Planning and Management.

Luckily, only a few students had to be evacuated as the storm occurred near the end of the summer session. Those that were on campus at the time were either attending summer school or attending conferences. All were safely evacuated and provided housing in other locations. The total complex was out of service for approximately 6 weeks following the storm and school officials estimated the total cost of damages at the complex to be at least $1.4 million. “Construction crews worked 12 to 14 hour days, 7 days a week to make the residence hall habitable,” stated Brown.

Eight weeks later, the mission was accomplished and the dining and cafeteria area was functional just in time for the fall session. Brown, school officials and managers needed to reduce the devastation of future flooding at the complex. The team commissioned a local engineering firm to assess the situation and determine the best floodproofing plan to keep high waters at bay. “We did not ever want to see anything like that again,” stated Brown.

Relying on the results of the study, officials were convinced that constructing a flood wall around the perimeter of the Maple-Willow-Larch complex was the best way to mitigate future damage, safeguard its students and staff, and protect the property. Even though some members of the community were opposed to the idea, officials were not deterred. The project cost totaled $1,166,723. The Federal Emergency Management Agency (FEMA), through its Hazard Mitigation Grant Program (HMGP), awarded $875,042 or 75 percent of the cost. The State of Iowa and local agencies contributed the remaining 25 percent of $291,681. The Iowa Homeland Security and Emergency Management Division administered the funds.

Ranging in height from zero to 4 1/2 feet, the flood wall surrounds the complex at the low-lying areas and was sand blasted to resemble the outside walls of the resident units. The flood wall is buried in the ground and is designed to withstand floodwaters 18 inches higher than those of the 1993 floods. It consists of a combination of earthen berm and concrete wall system. There are six gaps in the wall that allow natural walkways. In a flood, water is stopped from entering the complex by gates placed in the walkways of the concrete wall. Each gate, made of steel and rubber, is numbered to correspond with its place in the concrete wall. The floodwater pushing against the gate helps seal the rubber to the concrete and steel, further reinforcing the flood wall.

The flood wall and surrounding earth, built up to keep floodwaters out, also traps rainwater inside the area. During normal amounts of rain, a pump system senses rising water levels, flood stage or lower, and pumps the water out of the area. As a precaution, a back-up generator is in place if electricity is lost. During 3 days of heavy rainfall in August 2010, low-lying areas flooded again as the Skunk River and Squaw Creek exceeded capacity and in some areas surpassed record flood levels of 1993. Extensive flooding occurred throughout the city, as well as other buildings and facilities on the ISU campus, but floodwaters did not breach the flood wall at the Maple-Willow-Larch complex.

“When you consider the damage that was done in 1993, the benefits certainly outweigh the cost of the project. When I walked away from it, everything was done right. I am happy about it,” stated Brown. “It worked!”

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