Troubled Waters?

Despite deficiency ratings, local officials say Central Texas bridges safe

By Pamela Bond

Waco Tribune-Herald

Aug. 10, 2007

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Minneapolis may be more than 1,000 miles from Waco, but the effects of the Aug. 1 Mississippi River bridge collapse reach all the way to Central Texas.

Despite questions over the national state of bridges, and local concern since a hole appeared in the Interstate 35 overpass at University-Parks Drive on July 5, local authorities say Waco-area bridges are safe.

“About six or seven years ago, we were worried that the Washington Avenue bridge would flunk its inspection,” said Chris Evilia, director of the Metropolitan Planning Organization, a federally created group that coordinates transportation planning in McLennan County. “If it did, (the Texas Department of Transportation) said they’d come in overnight and barricade it so no one could cross.” Evilia added, “So if you’re not facing a concrete barricade, I’d say you’re pretty safe.”

U.S. Transportation Secretary Mary Peters has advised all state transportation agencies to inspect steel deck truss bridges, the type of design of the Minneapolis bridge. On Wednesday, Texas Department of Transportation inspectors checked the steel trusses of the bridge on State Highway 174 near Kimball in Hill County, one of 16 such bridges in the state.

“Our inspection procedures are sound,” said Ken Roberts, TxDOT’s Waco spokesman. “Our inspectors are not suddenly going to be doing their jobs differently, because some of the most aggressive and thorough inspections happen in Texas.”

Peters cautioned all states to beware of the weight loads on bridges during repair or construction, because early signs in the National Transportation Safety Board’s investigation point to gusset plates, which hold bridge trusses together, as a possible reason for the bridge’s collapse. The board suggested that the plates were not made of metal strong enough to hold the weight of traffic.

“It’s a learning process,” Roberts said. “We’ve seen no situations similar to what you’ve seen in the Minneapolis bridge. Bridges collapse for a variety of reasons, but normally it is a fire or some sort of accident. Those kinds of things you can’t prevent. There might be changes in (inspection) procedure and frequency.”

Texas has almost 50,000 bridges, each inspected every two years, said Alan Kowalik, state bridge inspection engineer.

“That means a routine inspection,” Kowalik said. “Basically our consultants go and they perform an inspection of the bridge and look at all the different elements of the bridge. It’s broken down into the deck, the superstructure (the beams), the substructure (the columns or piers), the channel. They get a rating from nine to zero.”

Bridges over water receive an underwater inspection of their piers every five years. The 27 consultants who inspect bridges for TxDOT are constantly working, Kowalik said.

“If there’s something ther that needs to be looked at closer, then it can be looked at every year,” Kowalik said. “It there’s something that we need to go back and look at more frequently then we’ll look at it more frequently.”

After the inspection, the bridge’s report is filed with the federal government and the city or county. The report includes a sufficiency rating, which is a number on a scale of 1-100, with 100 being perfect condition. Bridges with a score of 50 or below are labeled “structurally deficient.” The Minneapolis bridge had a score of 50. Almost 30 bridges in McLennan County have this rating, but County Commissioner Wendell Crunk said this is not necessarily cause for alarm.

“I think Texas has the safest bridges in the world,” Crunk said. “We immediately respond and take action.”

The number of structurally deficient bridges in Texas has been decreasing every year, according to state officials. In 2001, 70 percent of state bridges were rated as good or better, and 77 percent received that rating in 2006. TxDOT’s goal is to increase that number to 80 percent by 2011.

Out of Texas’ 49,518 bridges, 4.4 percent have a structurally deficient rating, compared to 8.7 percent of Minnesota’s 13,008 bridges that have the rating. Kowalik said the sufficiency rating takes into account factors including the ratings for each of a bridge’s elements, its age and average daily traffic.

“That thing has so many different factors into it, there’s not just one thing that makes that number go down,” Kowalik said. “If we saw something on the bridge, if there were some concrete deterioration or there was some concrete exposed, then we rate the superstructure down a certain amount.” Kowalik added, “You can’t just say because it’s a 50 then it’s in bad shape.”

If a bridge was built before requirements became more stringent, it could be labeled “Functionally obsolete.” Most older bridges have this classification. However, Roberts said, a bridge’s rating may not be the best means by which to judge its condition.

“Structurally deficient really relates more to truckloads than automobiles,” Roberts said. “Just because a bridge is labeled as structurally deficient doesn’t mean it’s unsafe. Functionally obsolete means that maybe the bridge was built in an age where the safety requirements (weren’t) what they are now, so maybe the lanes are not wide enough or the guard rails are not high enough.”

From the inspection reports, TxDOT issues a recommendation for a bridge, often calling for a replacement or repairs. A common recommendation is lowering the posted load limit, because as a bridge gets older, the amount of weight it can safely withstand decreases.

“The biggest safety issue is the load limit,” Crunk said. “If the state lowers the legal limit for the bridge, then we post that. Nothing heavier can go across that bridge. That might mean that we have to call the school district and tell them they have to find a different route for their school buses, because (they) can’t go over that bridge anymore.”

The load limit for the Washington Avenue bridge, built in 1901, was lowered after its most recent inspection.

“As long as we don’t have heavy trucks going across it, it’s pretty safe,” Evilia said.

If a bridge is beyond repair, it is recommended for the state replacement program. If Tx- DOT recommends a bridge for the program, the city or county will only fund 20 percent of the new bridge.

“They’re designed with a life span of 75 years,” Kowalik said. “There’s some that have been out there longer than that. There’s some in service that were built in the 1920s that are just stout, heavy bridges. And some don’t get a lot of traffic so they’ll last longer. For a bridge to last 50, 60, 70 years is very typical.”

While transportation authorities say not to judge a bridge by its sufficiency rating, Texas has more bridges than any other state but the fifth-lowest percentage of structurally deficient bridges, according to the Federal Highway Administration.

“For the Texas Department of Transportation and the transportation commission, bridge safety is the No. 1 priority right now,” Evilia said. “In fact, they are talking about shifting money away from new highways and into maintenance. Basically, we’ve taken the attitude that before we start building the new bridge, we should maintain what we’ve got.”