Iowa's bridges still among nation's worst, 10 years after Minneapolis' bridge collapse

A decade after the catastrophic collapse of an interstate bridge in Minneapolis, Iowa's bridges are still among the nation's worst.

The I-35W bridge tragedy on Aug. 1, 2007, killed 13 people and injured 135 others when the eight-lane structure over the Mississippi River failed amid evening rush hour traffic. Federal investigators blamed a design flaw as the likely cause and cited additional weight on the 43-year-old bridge that day.

The Minnesota disaster sparked a national debate and worries about America's deteriorating infrastructure. Those concerns were particularly felt in Iowa, which has 24,184 bridges — the seventh-most nationally, according to the Iowa Department of Transportation.

Ten years later, Iowa's bridge statistics still reflect a large, aging rural system in need of repairs.

Iowa has 4,968 bridges rated as structurally deficient. That number ranks No. 1 in the nation based on overall numbers and No. 2 based on the percentage (21 percent) of deficient bridges, according to the American Road & Transportation Builders Association, an industry group that analyzed 2016 federal highway data. 

But Lyle Brehm, a county engineer in Tama and Powershiek counties and a spokesman for the Iowa County Engineers Association, said motorists shouldn't be worried when they get behind the wheel.

"I don't think there is much reason for fear. We are required by federal statute to inspect every 24 months and we monitor the deterioration of them," Brehm said.

If there are serious problems, a bridge is closed until repairs are made or until the bridge can be replaced, he added.

Having a bridge classified as structurally deficient means one or more of the key bridge elements, such as the deck, superstructure or substructure, is considered in "poor" or worse condition. Most of these deficient bridges in Iowa are rural county bridges in farming communities with relatively low traffic volumes.

In fact, DOT officials said, Iowa has one of the lowest ratios of people per bridge in the country — about 129 people per bridge, according to 2016 data. (Kansas and Nebraska are lower at around 120 people per bridge.)

By making them a priority for state road construction spending, the DOT also says it has reduced the number of structurally deficient bridges on state and interstate highways from 256 in 2006 to 64 in 2016. The DOT's highways represent only about 8 percent of Iowa's overall road system, but they handle about 63 percent of Iowa's traffic volume.

Government and industry officials say improvements are underway in Iowa, particularly because of a 10-cent-per-gallon state fuel tax increase enacted in 2015. The tax hike generates about $200 million in additional money annually for state and local road and bridge projects. 

State Sen. Tim Kapucian, R-Keystone, chairman of the Iowa Senate Transportation Committee, said there is no question that progress is being made to upgrade Iowa's bridges. He added that lawmakers are continuing to push for ways to find more money for bridge projects, such as making government more efficient and revising funding procedures.

"We are definitely moving in the right direction," Kapucian said.

Brehm agreed, saying the extra fuel tax revenue will continue to make a positive difference in the coming years. 

"But this will not make it so that all of our bridges are in good condition in short order," he added.

Norm McDonald, director of the Iowa DOT's Office of Bridges and Structures in Ames, said the state's focus on repairing structurally deficient bridges has "made a pretty big difference" on the state and interstate highway system. But he cautions that the work is far from finished.

"A lot of interstate bridges were constructed in the 1960s, and a lot of those will be coming up for replacement in the next 10 years or so. So there will be a huge investment there," McDonald said. 

Kapucian, who farms in eastern Iowa, said Iowa's large network of county roads and bridges has served the state's agricultural sector well. It's important to maintain that system as farmers compete in global markets against other countries that are pushing to improve their transportation systems, he added. 

However, some of Iowa's county bridges are more than 100 years old and many others date to the 1940s and 1950s, when crop yields were lower and farmers weren't transporting such heavy loads. Some of these older bridges are now posted with weight limits, which impacts the movement of goods and services. But Brehm said the influx of additional fuel tax revenue is helping to accelerate improvements, such as installing culverts to replace small bridge structures.

In other cases, though, traffic counts have diminished so much that it may not be worth the expense of rebuilding some deficient rural bridges.

"They can't do every one of them so they are re-prioritizing those that have the most traffic or have the most school bus routes," said Scott Newhard, executive vice president of Associated General Contractors of Iowa.

Nationally, there are 55,710 structurally compromised bridges, according to a report in February by the American Road & Transportation Builders Association. If they were placed end to end, the line would stretch 1,276 miles, which is about halfway from New York to Los Angeles, the organization said

Alison Premo Black, the association's chief economist, said federal data shows 28 percent of bridges nationally — 173,919 of them — are more than 50 years old and have never had any major reconstruction work.

"America's highway network is woefully underperforming. It is outdated, overused and in desperate need of modernization," Black said. 

President Donald Trump has proposed a plan to rebuild America's infrastructure that includes reducing government regulations and seeking private-sector capital and expertise. He has called for dedicating $200 billion for infrastructure that he says can be leveraged for a $1 trillion investment. However, critics have been skeptical, saying more details are needed.

In the days after the 2007 Minnesota bridge collapse, Iowa bridge inspectors moved hurriedly to check the conditions of some questionable bridges, and then-Gov. Chet Culver called for a safety review of all Iowa bridges. But civil engineers said Iowa bridges were not in danger of sudden catastrophic failure, and the vast majority have multiple parts to absorb stress, aging and damage. 

Bridge failures in Iowa have been rare and have typically occurred on rural roads in circumstances such as when trucks were were too heavily loaded or when floods have washed out bridges.

In May, for example, a bridge in northeast Iowa's Winneshiek County collapsed after the driver of a grain truck weighing more than 10 times the bridge's weight limit tried to drive across it. 

County officials said the bridge over the Upper Iowa River east of Cresco was clearly posted with a sign limiting loads to 3 tons, but the grain truck had a load estimated at more than 30 tons. The truck driver was cited for violating the weight embargo and no one was injured.