Fast-tracked Bridge Design Relieves Flooded Iowa Highway Corridor, Wins Awards
August 21, 2020
Muscatine, Iowa – Stanley Consultants, a worldwide provider of engineering, environmental and construction services, and its industry partners were awarded the Outstanding Civil Engineering Achievement by the Iowa Section of the American Society of Civil Engineers (ASCE) for its work in battling Missouri River basin flooding and restoring mobility.
The Missouri River Overflow Bridges project also received an honor award from the American Council of Engineering Companies (ACEC) of Iowa.
In 2019, Iowa experienced the wettest January to May period on record. A bomb cyclone struck in mid-March, dropping intense rain and snow while Nebraska, the Dakotas and Iowa were still snow-covered. The frozen ground led to intense runoff and subsequent flooding. Levee breaches were common along the Missouri River and flood fighting was an all hands-on deck mission from March to September for the Iowa Department of Transportation staff and its consultants to repair bridges and roadways and restore mobility.
Flooding and the resulting damage closed IA 2 at the Missouri River bridge near Nebraska City. Iowa Governor Kim Reynolds challenged Iowa DOT to re-align the levee and elevate traffic on a new bridge to increase river overflow conveyance and improve the resiliency of the IA 2 corridor before spring 2020, less than a year away.
“Initially I thought there was a low probability of it being achieved,” said Jim Nelson, IDOT director of bridges and structures.“But the governor laid down the challenge and the folks responded.”
The re-aligned levee and bridge construction was completed ahead of schedule. Dual 1,100-foot x 40-foot bridges were designed in just nine weeks and the first bridge was constructed and open to traffic on IA 2 less than six months after contract letting,which was over two months ahead of an already accelerated schedule. Stanley Consultantswas the design engineer and engineer of record for the expedited bridge design.
Reconstructing a constriction in the levee system was identified as a potential improvement that would increase conveyance by opening the floodway. This was accomplished by raising the roadway and pushing back the U-shaped levee that had been originally designed around the existing roadway embankment. This provided room to realign and straighten the levee, allowing water to flow straight past. The new bridges were constructed to carry traffic over the river overbank which is now within the levee system and subject to high water events.
In April 2019, the main objective was established that the first bridge be open to traffic and the levee realigned, allowing the river conveyance to be open to flow by March 1, 2020. The first bridge was open to traffic in December 2019 quickly followed by opening the river overflow conveyance before the end of 2019, more than two months ahead of schedule.
About Stanley Consultants
Stanley Consultants provides program management, planning, engineering, environmental and construction services worldwide. Recognized for its commitment to client service and a passion to make a difference, Stanley Consultants brings global knowledge, experience and capabilities to serve federal, municipal and industrial clients in the energy and infrastructure sectors. Since 1913, Stanley Consultants has successfully completed more than 25,000 engagements in all 50 states, U.S. territories, and in 110 countries. For more information on Stanley Consultants, please visit http://www.stanleyconsultants.com.