Bridge Inspectors Battle Small Cracks, Big Bureaucracy

Aug. 3, 2007 — -- In his 41 years inspecting bridges, Ken Whelton has seen just about everything, but even he was unprepared for footage of the Minnesota bridge collapsing without warning into the Mississippi River.

"That totally shocked me that the bridge would fall straight down," Whelton said. "That is very, very unusual and difficult for me to comprehend."

Everyone now wants to know who was inspecting that bridge, and how the inspectors might have missed a crucial flaw in its structure -- or worse, identified the flaw but let it go unfixed.

The answer to this question is not so simple in the byzantine world of bridge inspection. Inspections are conducted by a mix of state and local government agencies, many of which subcontract the jobs out to private bridge inspection agencies.

Often armed with high-tech equipment but sometimes using nothing more than their eyes and a camera, inspectors are the front line of bridge safety. They dive under water, stand underneath and sometimes scale the sides of bridges to inspect beams of steel, sometimes hidden by layers of paint or rust, and roadbeds of concrete.

Some of the things inspectors dread the most characterized the collapsed Minnesota bridge, including nonredundant design, cold climates and heavy traffic loads, Whelton said.

But in conversations with state transportation officials, it became clear that much as they fight bridge deterioration, they also must contend with the tension of trying to go beyond the minimum federal inspection requirements, which some say are insufficient and lead to potentially vague and unhelpful inspection reports.

Sleuthing for Clues

Whelton and his team of inspectors examine not only at a bridge's overall structure but throughout the bridge's nooks and crannies, looking for water and ice leaking into corroding joints, and steel beams rusting away.

These small things -- weaknesses in small joints or the destruction caused by ice water running through cracks in the bridges -- are often key to the integrity of a bridge, and can have destructive consequences if they are not maintained, Whelton said.

Whelton, who is now semi-retired, most recently worked for the Non-Destructive Testing Group, a private contractor that worked for the Michigan Department of Transportation.

Indeed, state departments of transportation inspect only a fraction of bridges themselves. They often subcontract to inspectors like Whelan, or they do not control the bridges altogether: Local towns and cities often assume full inspection responsibilities.

Having worked in Michigan throughout his career, Whelton knows the harm that the freeze and thaw cycle can have on bridges in cold climates like Minnesota. Ice is used to clear those roads, particularly when they are used as much as I-35W was, eventually creating ice water runoff that causes steel to rust.

Then "the corrosion is accelerated by the warm temperatures" of the summertime, often requiring repair and repainting.

Whelton said nonredundant bridges like the one that collapsed in Minnesota don't often pose serious problems. Though they lack ancillary support systems, in his study of bridges he found that they are usually some of the strongest bridges because their structures cannot break.

But if there are weaknesses, they could spell disaster, he said, as may have been the case in Minnesota this week.

States and Standards

Inspectors' jobs require close attention to detail, and some states have responded by ramping up their regulations to ensure more expertise and a more-detailed rating measure for their inspectors.

The basic standards for bridge inspection, including the training required of inspectors and the grading system for bridges, are all set at the national level by the Federal Highway Administration, and were last updated in 2005.

Those inspecting bridges must be either professional engineers or have a certain number of years' experience working with bridges, using the federal code, which was last updated in 2005.

Three parts of bridges -- the substructure, superstructure and roadway -- are graded on a 10-point scale and then labeled if necessary as structurally deficient or functionally obsolete.

But some state departments of transportation are increasingly finding these minimum requirements insufficient, and are ramping up their regulations at the local level.

In Texas, the state with the most bridges in the country but also one of the strongest safety records, bridge managers must specifically be bridge engineers -- any other type of engineering degree won't do, according to Randy Cox of Texas' Department of Transportation.

"There are many kinds of professional engineers, and we want to make sure that they have the proper engineering training," Cox said.

And in Oklahoma, the department of transportation has joined other states in following a more rigorous grading system for bridges that go beyond the three numerical grades required by the government with upward of 15 ratings, said Bob Rusch, the chief bridge engineer for the Oklahoma Department of Transportation.

Rusch said that the basic federal guidelines are too vague and may cause inspectors and bridge managers to overlook certain critical flaws in a bridge. A blanket grade of 5 on a bridge's superstructure, for example, might occlude a more serious flaw in its beams or welds.

While this decentralized system that has states and even cities and towns overseeing bridge inspection does have the benefit of allowing ambitious regions to impose stricter regulations, it can leave behind poorer or less-ambitious regions with only the minimum minimal standards.

Perhaps one of the most persistent problems caused by this highly decentralized system is inconsistency in the grading of bridges, Rusch said, particularly if it is done on a simple 10-point scale. Because they rest on the assessment of individuals with different levels of training and experience, maintaining the integrity of the ratings can be a challenge, he said.

"The inspections are a little too varied. They're subjective and different inspectors will rate the same bridges differently," said Rusch.

But Oklahoma has devised another solution to this problem, one that once again goes beyond the federal regulations. The state has begun to require refresher courses for inspectors to help maintain quality across the state's bridge ratings, with the aim of helping standardize grading procedures.