hide captionWisconsin bridge inspector Joel Alsum uses an ultrasound device to check the integrity of a pin that secures steel plates under an I-43 bridge in Green Bay. He's looking at a portable screen that shows the pin's ultrasonic image.
Wisconsin bridge inspector Joel Alsum uses an ultrasound device to check the integrity of a pin that secures steel plates under an I-43 bridge in Green Bay. He's looking at a portable screen that shows the pin's ultrasonic image.
hide captionThis portable screen provides an ultrasound image of the steel pin.
The portable screen that shows the ultrasound image of the pin.
In the year since the Minneapolis I-35W bridge collapsed, states appear to be aggressively inspecting bridges to locate problems. But some experts say not enough is being done to fund the maintenance of the nation's aging and crumbling bridges.
Federal Highway Administration figures indicate there are still about 150,000 bridges across the country rated as structurally deficient or functionally obsolete, according to a new report issued by the American Association of State Highway and Transportation Officials.
"One in four of the nation's more than 590,000 bridges is rated as either in need of repair or inadequate to handle today's traffic," says Pete Rahn, Missouri's transportation director and president of the state highway officials group.
The report indicates the average age of the nation's bridges is 43 years; most bridges are designed to last 50 years, meaning many are nearing the age of retirement.
The cost to fix or replace all the bridges in need of attention? A whopping $140 billion — and the cost is rising every day because of skyrocketing construction costs.
"Steel, concrete, asphalt [and] earth work have increased at least 50 percent," says Rahn. "And oil has quadrupled in the last four years, forcing states to delay needed repairs."
What's more, Rahn says that every state is short on funds needed to provide the kind of systematic preventive care that can extend the lives of these aging bridges.
The group is calling for "significant and radically increased federal help."
"We need federal intervention — and federal intervention at a big level," says Gov. Ed Rendell (D-PA), the new head of the National Governors Association.
But more federal funding may be hard to come by. The federal highway trust fund is running out of money, and high gas prices are partly to blame. The 18.4 cents-a-gallon federal gas tax is what fills up the trust fund, but with Americans driving less and turning to more fuel-efficient vehicles, gas tax revenue is on the decline, meaning the trust fund could be $3 to $4 billion in the red by next spring.
Legislation that moves $8 billion from the general fund to the highway trust fund passed the U.S. House of Representatives last week, as did a bill to create a $1 billion bridge repair fund. Both were sponsored by Rep. James Oberstar (D-MN), who heads the House Transportation and Infrastructure Committee.
"My objective is that those lives lost in the [I-35 bridge] tragedy will not have been lost in vain — that, indeed, the Congress will act, the president will sign a bill, state departments of transportation will act," Oberstar said in an interview with NPR.
Oberstar's bill, which now moves to the Senate, also would mandate more frequent bridge inspections, higher standards for inspections, and more and better training for bridge inspectors.
"Inattention by the states to their bridge needs — and sort of an overconfidence that they've built bridges to high standards and don't need to revisit them — is the principal concern I have, and I think the underlying cause for escalating deteriorating bridges, corrosion and metal fatigue," Oberstar said.
Oberstar says in recent years, states, including his own, had shifted $5 billion of federal funding out of their bridge funds to other needs, leading to neglect of bridges. Though a National Transportation Safety Board inquiry concludes that undersized gusset plates and an outdated design seem to be the primary factors that led to the I-35 bridge collapse, Oberstar and others point out that investigators also found significant corrosion on the gusset plates and on other parts of the bridge that may have been contributing factors.
Ultrasound Tools Can Detect Flaws
Oberstar wants to make more funding available for states to use cutting-edge tools for inspecting bridges so they can better identify potential structural problems before they become serious.
To check for trouble spots in Wisconsin bridges, inspector Joel Alsum uses an ultrasound device. Wisconsin is one of a few states to use the tool to try to find cracks and corrosion before they are visible to the naked eye. Problem areas can be watched over time, or repaired or replaced, if necessary.
Underneath the deck of the I-43 bridge over Green Bay, Wis., Alsum takes a detailed look at some pins that are part of the structure holding this bridge together.
"We are going from pin to pin and doing phased-array ultrasound, which is a volumetric test ... to look for cracks or corrosion in the pins."
The steel pins are huge — five to six inches in diameter and about 10 inches long. They fasten together steel plates that hold the bridge's steel girders together at its joints. It's critical to the integrity of the bridge. The ultrasound technology is not unlike what doctors use to get an image of a fetus.
Alsum rubs a gel on the face of the pin, like a doctor would on a pregnant woman's belly. Then he moves the handheld ultrasound device over the surface as it pulsates sound waves into the pin.
It creates a color image of the inside of the solid-steel pin on a portable screen.
"What we're looking for here is something out of the ordinary...." Alsum says. "Typically, we're looking for cracks, and we're also looking for large areas of corrosion. Visual inspection would not be able to identify these areas, so we need to use this volumetric test."
This phased array ultrasound puts Wisconsin ahead of the curve in bridge inspections. Wisconsin has been using the tool for about four years, Alsum says.
More Emphasis On Maintenance
Since the Minneapolis bridge's tragic collapse, states have stepped up inspections of their bridges, especially those of similar steel deck truss design.
A handful of states, including Minnesota, have moved aggressively to close bridges they feared weren't structurally sound. Just last week, Illinois and Iowa reduced traffic by one lane on the I-80 bridge over the Mississippi as a precaution after inspectors found cracks.
"I think the bridge collapse has made bridge inspections more of a priority...." says Andrew Herrmann, a member of the American Society of Civil Engineers' board of directors. "There's been some progress, but there could be more. The other area that should get attention is maintenance."
Michael Pagano, dean of the college of urban planning at the University of Illinois, agrees states are spending too little on the maintenance of bridges and other parts of the transportation infrastructure. Pagano recently graded the states on infrastructure management for Governing magazine.
He says politicians often budget only for what a bridge like this will cost, but not what it costs to keep up.
"What we have today is crumbling and neglected infrastructure, words that seem to go together all the time," Pagano says. "And the reason is we've never planned for how we should adequately pay for the use of that facility over the design life of an asset."
Pagano says the failure of the Minneapolis bridge should have been a wake-up call but says it has yet to lead to a significant change in how the nation funds the maintenance, repairing and replacement of it's aging bridges.
Q&A: A Guide To Understanding Bridge Talk
After the I-35W bridge collapsed in Minnesota last year, terms to describe bridge conditions — such as "structurally deficient" and "functionally obsolete" — peppered news stories. The I-35 bridge had been classified as structurally deficient, but what does that really mean? Are structurally deficient bridges unsafe? And how often are bridges inspected? Here, an explanation of bridge lingo and what it reveals about safety.
When is a bridged deemed to be "structurally deficient"?
Bridges are classified as structurally deficient bridge when inspectors find trouble spots that need to be monitored and/or repaired.
What is a "functionally obsolete" bridge?
That refers to bridges that were built to design standards no longer in use today.
Do either of these classifications mean a bridge is unsafe?
No. Neither classification suggests a bridge is unsafe or likely to collapse. Both suggest that the bridge must be monitored, inspected and maintained. In some cases, bridges may have weight or speed restrictions placed on them until they can be repaired or replaced.
How are these classifications determined?
Bridges are rated using a scale of zero to 9; a zero rating means the bridge should be shut down, while a 9 rating means it is in perfect condition. At the time that the I-35 bridge in Minneapolis collapsed, it was rated 4, a classification that meant the state could continue to operate the bridge without load restrictions.
How often are bridges inspected?
Under federal law, all bridges are inspected every two years. Standards for inspections, frequency of inspections, and training and standards for inspectors would all be increased under legislation that recently passed the House and is headed to the Senate.
Is it rare to find a crack in a steel bridge?
Not according to Wisconsin bridge inspector Joel Alsum. He says it is common to find cracks in steel bridge structures in secondary members such as girders, plates and beams.
"Often people will hear 'crack on a bridge' and think it's ready to fall down. But on a secondary member, it's very common. And on a steel bridge, probably about 90 percent have some kind of crack on them," Alsum says.
What are common causes of structural deficiencies?
Water, salt, stress and corrosion can make a bridge structurally deficient. So can age. As a bridge ages, corrosion and decay can reduce its ability to support vehicles, according to the Department of Transportation.
How much would it cost to fix these bridges?
If the U.S. were to repair every single bridge labeled as structurally deficient or functionally obsolete, it would cost at least $140 billion, according to a recently released report from the American Association of State Highway and Transportation Officials. But that's in today's dollars, and highway officials caution that the price tag is rapidly rising. The cost of concrete, steel, asphalt and diesel fuel for heavy equipment have all been spiraling upward, forcing some states to delay repairs.
How do we pay for bridge maintenance and repairs?
At the gas pump, mostly. The federal gas tax — which is 18.4 cents per gallon on regular gas and 24.4 cents per gallon on diesel — goes directly into the federal highway trust fund; highway and bridge projects are paid out of that fund.
But the fund may soon run out of money. Four dollar-a-gallon gasoline has led to an unprecedented drop in vehicle miles driven in the first six months of this year, so Americans are buying less gas and paying less in motor fuel taxes. States often match federal transportation funds with their own, which they, too, usually collect at the gas pump. It's a double whammy that could leave some states short on road and bridge repair funds next year.