AMES, Iowa – June 22, 2011 – The Iowa Department of Transportation (DOT) will be deploying flood mitigation strategies for Interstate 29 and U.S. 30 near Missouri Valley. The effort is to address a specific flood inundation scenario. The work is expected to begin this week. Meanwhile, some limited sandbagging was performed today to prevent water from reaching the travel lanes of U.S. 30.
The Iowa DOT recognizes that U.S. 30, I-29 and the Missouri River crossing between Missouri Valley, Iowa, and Blair, Nebr., are important to personal mobility and commerce. They serve as a critical transportation lifeline for citizens living, working and conducting business in this area between the two states, as well as other parts along the I-29 corridor.
The Iowa DOT has examined the unique characteristics and challenges associated with this area, including the location of the levees, roadway elevations, hydraulics,railroad, and area creeks and streams, to determine what, if any, mitigation strategies could be deployed to keep the roadway open. Based on the assessment, it was determined there are two most plausible scenarios that would cause an inundation of the roadways in this area.
The first scenario involves a breach or overtopping of the levee upstream from U.S. 30. For this scenario, there are no emergency mitigation efforts that would prevent the roadways from being inundated due to the volume of water and characteristics of the area.
The second scenario involves a breach or overtopping of the levee downstream from U.S. 30. For this scenario, the Iowa DOT has developed a plan that would help mitigate the flooding of U.S. 30 west of Missouri Valley and I-29 north of the I-29/U.S. 30 interchange.
The mitigation plan includes two strategies:
· On I-29, north of Missouri Valley, the Iowa DOT will place a TrapBag® flood barrier wall on both the inside and outside shoulders of the north- and southbound lanes. The wall will be approximately a half-mile in length. Pumping of flood waters will also be performed in the median.
· On U.S. 30, the Iowa DOT will place a TrapBag flood barrier wall on both sides of the roadway in a location approximately 2 miles east of the Missouri River crossing where the roadway is the lowest.
Reiterating, these mitigation measures will not prevent U.S. 30 or I-29 from being inundated with flood waters if a breach occurs upstream from U.S. 30.
Due to the complexity of the flooding situation, vulnerability of the levee systems and increased water levels, there are also other unanticipated scenarios that could occur that would result in road closures.