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Tue September 23, 2008 - Midwest Edition
In spite of early summer flooding throughout Iowa the recent completion and opening of a 1 mi. (1.6 km) stretch of I-235 through Des Moines remained high and dry from the high water in the region, said Wes Musgrove, PE and project manager of the Iowa Department of Transportation (Iowa DOT) .
“As far as recent flood events in Iowa, there were no impacts to the project,” Musgrove said. “The I-235 Bridge over the Des Moines River and other locations along the corridor remained well above floodwaters. Critical infrastructure including retaining walls, roadway elements and bridges was completed well in advance of the flooding.”
And that’s good news for Des Moines motorists, who didn’t need any more driving challenges after six years of heavy construction and congested traffic. With the heavy construction behind them, these motorists now have much easier driving conditions and more pavement to maneuver through in the area.
Road workers completed the final stretch of pavement on this mammoth road reconstruction project last season and now are working on roadway amenities including landscaping, erosion control, bridge staining and pavement markings.
Noteworthy for being the largest highway project to be let in the state, Iowa DOT awarded the $429 million contract to five Iowa contractors.
“It was also noteworthy when the team of contractors, Cramer and Associates, United Contractors Inc., Jensen Construction, Reilly Construction Company and Des Moines Asphalt and Paving finished the project ahead of schedule and picked up $600,000 in incentives,” said Robert Cramer, president of Cramer and Associates.
An additional 75 subcontractors worked on the site over the last six years.
Funding for the roadwork came from a 90-percent/10-percent split between the federal and state governments.
A Project of Firsts
“The I-235 reconstruction was also a project of firsts,” said William Lusher, former Iowa DOT project manager.
“It was the first Iowa road project to use soil anchored retaining walls, the first time stone columns were installed to support embankment and the first time the Iowa DOT activated a Traffic Management Center (TMC) to manage traffic control during the length of the project,” Lusher noted.
In addition to paving the final stretch of freeway, roadwork in the sixth and final year centered on reconstructing the 9th Street Bridge, the last remaining structure out of 70 replaced or renovated as part of this project, reconstructing the downtown interchange and completing reconstruction of the center portion of the Des Moines River Bridge.
The six years of intensive construction raised clouds of dust, forced multiple day and night ramp and lane closures and created congestion to frustrate motorists. However, motorists did see some relief during the final year.
“Compared to 2006, last year it was pretty easy to meet the completion deadline and earn the maximum incentive of $600,000,” Cramer said.
At the same time, work crews faced a rigorous schedule. While crews poured the final concrete at the downtown interchange, motorists faced some driving inconvenience when the eastbound exit ramp and 5th Street on ramp were closed to finish the interchange.
At the Des Moines River Bridge, crews removed the bridge deck and existing girders and set new steel to widen the bridge deck. During the final year of construction here, workers switched traffic over to the westbound lanes of the bridge while completing the eastbound lanes.
Over the last six years, workers reconstructed 14 mi. (22.5 km) of pavement and raised 70 new bridges. The new freeway configuration features three lanes of traffic in each direction and a fourth through the downtown district where traffic volumes exceed 120,000 vehicles per day (vpd).
Workers removed 2.2 million cu. yd. (1.8 million cu m) of material from the construction zone. To bring the road back to life, they placed 292,000 tons (265,000 t) of HMA pavement and 634,000 sq. yd. (530,000 sq m) of PCC pavement.
Ironworkers hung 35 million lbs. (15.7 million kg) of structural steel for the bridges and another 65 million cu. yd. (49.7 million cu m) of structural concrete was poured.
Additionally, 165 homes, five apartment buildings and 14 commercial properties were removed to make room for the additional lanes.
United Contractors put into action a Link-Belt 8028 crane, several American Crawler cranes, several Cat and Komatsu excavators, Cat dozers and loaders, and JLG and APE boom lifts to erect the five bridges under their contract.
Similar to other interstate reconstruction throughout the country, this section of I-235 was overdue for an overhaul according to Iowa DOT documents. Not only is I-235 the primary transportation corridor through the Des Moines metropolitan area, but this stretch of the interstate also carries significantly more traffic than any other corridor in the state and is a key component to continued economic growth of the area.
Crash statistics of 850 collisions per year also were higher than the average throughout the state and continually rising.
According to Iowa DOT, these crash statistics, the high ADT (that is projected to hit 150,000) and the rapidly deteriorating concrete, low bridge clearances, closely spaced interchanges, limited traffic lanes and outdated traffic capacity sparked the construction.
A Well-Organized Plan
Plan specifications mandated that two lanes of traffic in each direction remain open during construction, creating tight working conditions for and exposing crews to the danger of working in and around thousands of moving vehicles.
Musgrove and Cramer agree that a well-organized communication plan was a key to making the construction move forward in a timely manner while the TMC contributed to keeping crews safe and maintaining movement on the road.
Both of these pieces of the plan were particularly crucial during times when the state shut down sections of the freeway completely for the demolition and construction of 29 overhead bridges during 24-hour work shifts on weekends state officials said.
“Also, there was a host of other work not allowed over traffic including traffic shifts, sign truss installations and overhead utility crossings, that forced traffic to be routed off the freeway at these locations,” Lusher said.
“The communication and coordination among the 70 plus contractors along with a mix of government agencies were critical components to keeping the project moving forward and eventually completing it ahead of schedule,” said Musgrove.
“Over six years of reconstruction beginning in 2002, I witnessed and was part of a progressive evolution of how this varied group of personalities interacted and gradually grew to function as a unit in making project-related decisions and in responding to various situations that arose during reconstruction. It was very interesting and rewarding,” Musgrove remarked.
Robert Cramer agreed that coordinating the work of the subcontractors played a big part in making the project a success.
“The biggest challenge with this last project was dealing with so many different contractors and keeping them pointed in the same direction,” Cramer explained. “We had a great group of contractors to work with and they all did an amazing job.”
“All good contractors have strong leadership with good ideas of how they want to proceed. Therefore it takes an extra effort to keep everyone on the same page when contractors are getting in the way of each other,” Cramer explained further.
“And the first time use of the TMC on an Iowa Department of Transportation project turned out to be a definite asset,” Musgrove noted.
“A series of cameras mounted throughout the construction corridor streamed video back to the TMC,” Musgrove explained. “There, dispatch staff monitored the video and could respond instantly and contact the appropriate personnel to respond to any traffic problems or emergency.”
“It was very beneficial in monitoring traffic flow throughout the corridor and within work zones, and in mitigating congestion due to disabled vehicles, accidents, construction activity, etc,” Musgrove explained. “It enabled the DOT to respond instantly to changing traffic conditions to maximize traffic flow and minimize congestion.”
Musgrove also found it beneficial from a personal perspective and allowed him to monitor construction progress from a “bird’s eye view.”
“Construction of the Mechanically Stabilized Earth retaining walls also proceeded well. These walls consist of stacked concrete panels and galvanized steel straps that extend back behind the face of the wall into sand back-fill material,” Musgrove explained.
“This structure creates a reinforced mass of material that is extremely stable and relies on the sand and strap interface to hold the wall vertical,” Musgrove noted.
According to the bid estimate, a total of 499,278 sq. ft. (46,384 sq m) of retaining walls were to be constructed on this project.
“A well-designed set of engineering plans also kept the project on track and ahead of schedule and no major design changes had to be made, except for an occasional adjustment to construction to optimize traffic flow,” Musgrove said.
Clean-up work will continue through this year into early 2009 with little or no traffic impacts, Iowa DOT officials said. CEG