Hawaii bridges old, need work — but safe
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By Jan TenBruggencate
Advertiser Staff Writer
By Jan TenBruggencate
There are no Hawai'i bridges built exactly like the one that collapsed into the Mississippi River in Minneapolis Wednesday, and engineers say the state's bridge inventory — though it has its deficiencies — is safe.
"The state does a good job of inspecting all bridges," said Ian Robertson, professor of structural engineering at the University of Hawai'i-Manoa.
That said, inspections don't catch everything, as the Minnesota disaster shows.
"That bridge was inspected in 2006, and one year after the last inspection, the thing totally falls down. That's kind of scary," Robertson said.
Federal Transportation Secretary Mary Peters yesterday signed a request that the nation's state transportation departments immediately inspect any bridges like the steel-deck truss bridge that failed in Minnesota.
"Even though we don't know what caused this collapse, we want states to immediately and thoroughly examine all similar spans out of an abundance of caution," Peters said in a statement.
Scott Ishikawa, spokesman for the state Department of Transportation, said Hawai'i has seven steel truss bridges, but only one — the Kolekole Bridge near Akaka Falls outside Hilo — is a steel-decked arch truss bridge, the same general type as the Interstate 35W bridge in Minnesota. Big Island transportation engineers will be instructed to immediately inspect that bridge, he said.
"All the Big Island bridges were last inspected in 2005 and at that time, Kolekole Bridge was found to be satisfactory, but at the request of federal officials, we'll take another look," he said.
The Kolekole bridge has additional precautions built into its design that state engineers believe were not present in the Minnesota bridge, including a redundancy feature in which other beams support the bridge when one fails, Ishikawa said.
He also said the bridge underwent a seismic retrofit three years ago to make it more resistant to earthquakes.
"We have a small number of steel bridges, but they are built so that if one beam fails, the others can take up some of the load, so you don't have a total collapse in a short period of time," Ishikawa said.
Every state and county bridge is inspected under federal requirements every two years. There is no need for an emergency statewide inspection of all bridges, said both Robertson and Ishikawa.
Robertson said the inspection process generally works.
"I think the inspection process that we have in place at the moment has served us well," he said.
"Our inspections of (concrete bridges) are mostly visual," Ishikawa said. "They look for spalls (chips or slabs that have cracked off), for cracks, for anything that looks amiss. If they see anything, they do further inspection."
In some cases engineers may also call for load tests, in which bridges are physically loaded with weight such as heavy trucks or piles of concrete blocks. Inspectors then test for deformation of the bridge, watch for widening of cracks and conduct other tests, Robertson said.
Weakness in a bridge structure does not always mean it must be closed. Often, posted allowable loads are reduced.
The failed Minnesota bridge, built in 1967, stretched 1,900 feet and had a single 458-foot steel arch to avoid dropping piers into the river that would interfere with navigation.
"We don't have any 6- or 8-lane bridges crossing a wide river like the Mississippi," Ishikawa said.
But Peters, the federal transportation secretary, said she is calling for a complete review of all bridge inspection procedures — not just for steel-truss bridges.
"What happened in Minnesota is simply unacceptable. We must have a top-to-bottom review of the bridge inspection program to make sure that everything is being done to keep this kind of tragedy from occurring again," she said.
70,000 DEFICIENT BRIDGES
Nationally, more than 70,000 bridges across the country are rated structurally deficient — including the span that collapsed in Minneapolis — and engineers estimate repairing them all would take at least a generation and cost more than $188 billion.
That works out to at least $9.4 billion a year over 20 years, according to the American Society of Civil Engineers.
The bridges carry an average of more than 300 million vehicles a day.
It is unclear how many of the spans pose actual safety risks.
In a separate cost estimate, the Federal Highway Administration has said addressing the backlog of needed bridge repairs would take at least $55 billion. That was five years ago, with expectations of more deficiencies to come.
At least 73,533 of 607,363 bridges in the nation, or about 12 percent, were classified as "structurally deficient," including some built as recently as the early 1990s, according to 2006 statistics from the Federal Highway Administration.
The federal government provides 80 percent of the money for construction, repair and maintenance of the so-called federal-aid highway system including interstate highways and bridges. But states set priorities and handle construction and maintenance contracts.
A bridge is typically judged structurally deficient if heavy trucks are banned from it or there are other weight restrictions, if it needs immediate work to stay open or if it is closed. In any case, such a bridge is considered in need of considerable maintenance, rehabilitation or even replacement.
The latest assessment, from 2006, shows 46 percent of Hawai'i bridges are considered substandard. The state has the third-worst record in the country, with 513 of its 1,110 bridges rated substandard.
Only Rhode Island and Massachusetts have a higher proportion of substandard bridges, and the national average is 25.8 percent.
Officials have said a reason for the poor ranking is that Hawai'i has many old bridges that don't meet current federal highway standards, but are in no danger of failing.
Bringing the 275 deficient or obsolete bridges out of the total 758 bridges under the Transportation Department's control up to standard would cost about $2 billion, state transportation officials have said. The rest of the state's 1,100 bridges are generally under county authority.
But Robertson said the failure rate for bridges is extremely low.
Most of Hawai'i's bridges are made of reinforced concrete. It is the material of choice in part because of the corrosive nature of Hawai'i's salt air on steel structures.
Roberston said concrete is a forgiving construction material in that structures are often built with wide safety margins, and because potential failures in the material provide plenty of obvious signs.
"Reinforced concrete will normally show signs of stress. You will see things going wrong long before a collapse," he said.
Many of Hawai'i's substandard bridges are like the the historic one-lane 'Opaeka'a Road Bridge in Wailua Homesteads on Kaua'i, which is touted as perhaps the only British-built bridge in the United States. Its beams were forged in 1890 by Alex. Findlay & Co. in Motherwell, Scotland.
They were originally part of the Wailua River Bridge, and when that bridge was replaced in 1919, the steel beams were hauled up the hill and reassembled over 'Opaeka'a Stream by County Engineer Joseph Moragne.
Today, the 117-year-old steel is nearly rusted away. Great slabs of twisted steel hang off the bridge bottom, and the bridge's rated load is now just 5 tons.
"There's not many people can use it if it gets any lower than that. That's not ideal. You want to bring it back up," Robertson said.
Kaua'i County Engineer Donald Fujimoto said he doubts restoration is possible.
"I think we're past the point of preserving it. We're putting it on our capital improvements projects budget for replacement, but based on the past public input, a lot of people said they wanted the same rural character of the bridge," he said.
If the community insists, the county could build a new one-lane bridge to match the old, Fujimoto said.
Community historian Pat Griffin said that would be welcome.
"The 'Opaeka'a and Pu'u 'Opae bridges are natural traffic calmers. People have to slow down when they go through there. And they are also really important parts of our history," Griffin said.
Ishikawa conceded that communities from Hana to Hanalei fight hard to keep their one-lane bridges. Even if such bridges are rebuilt with new materials, they will always fail to meet federal highway standards for things such as easy traffic flow, pedestrian and bike paths and crash resistant barriers.
"Our bridges are not in danger of falling down, although a lot of them are historic and will never be up to standards," he said.The Associated Press contributed to this report.
Reach Jan TenBruggencate at firstname.lastname@example.org.