A statewide effort to ensure bridges and freeway overpasses will better withstand earthquakes is well on its way toward its goal of improving hundreds of structures from the Big Island to Kaua'i.

State transportation officials are finishing upgrades to the 52 most critical bridges and overpasses on the Big Island, including the Honokoa Bridge north of Kawaihae Harbor.

And they have spent millions of dollars upgrading 38 of O'ahu's most fragile bridges and are working their way through a list of 321 potential bridges and overpasses on O'ahu that also might have to come up to federal earthquake standards.

The Big Island has the greatest potential for quakes, so it was targeted first, said Scott Ishikawa, spokesman for the state Department of Transportation. O'ahu, with the most bridges and overpasses and the highest traffic volume, came next, he said.

Iao Stream Bridge and Ho-nolua Stream Bridge on Maui will be rebuilt next year to current seismic standards. But retrofitting contracts for 39 other Neighbor Island bridges and overpasses are years away because of limited funding, Ishikawa said.

Ian Robertson surveyed the damage to the Big Island's Ho-nokoa Bridge right after the October 2006 earthquakes and was impressed by the improvements he saw during an informal visit last month.

"It's already been repaired and will survive an earthquake a lot better the next time," said Robertson, a University of Hawai'i structural engineering professor.

"They're all considered seismically deficient," said Robertson, who visited the Big Island last year as part of a three-person UH engineering team surveying earthquake damage. "But I think the DOT is doing a great job of keeping up."

The retrofitting projects began in 1994 to comply with federal legislation and have gone on mostly unnoticed to the thousands of drivers who pass by.

"Much of the work is on the sides of the road where you have the support posts holding up the overpass," Ishikawa said. "It hasn't really disrupted traffic too much."

But Robertson, who knows what to look for, has noticed more and more upgrades as he drives around O'ahu.

"California jumped on the retrofits fairly quickly when it was mandated," Robertson said. "Hawai'i isn't far behind at all. I wouldn't say we're lagging."

NOT QUAKE-PROOF

The work took on renewed interest after a Minnesota bridge collapsed into the Mississippi River on Aug. 1, and last year's 6.7- and 6.0-magnitude earthquakes damaged Big Island buildings and knocked out power across O'ahu.

The retrofitting isn't designed to make the bridges and overpasses earthquake-proof.

But by firming up their beams, increasing the width of the pillars that bridges sit on and reinforcing the pillars with concrete and other materials, transportation officials hope to prevent collapses that could shut down freeways and block emergency vehicles from getting through.

"You don't want a catastrophic failure where there's a total collapse," Ishikawa said. "This work will help keep the freeways up and standing after an earthquake. And it'll provide us enough time to fix the bridge."

Commuters saw firsthand the fragility of O'ahu's freeway system in September 2006 when a military rig damaged H-1's 'Aiea overpass, forcing the freeway's closure just before pau hana time. Thousands of drivers were forced to improvise alternative routes home as they crawled for hours through gridlock.

Preventing similar problems by retrofitting bridges and overpasses isn't cheap.

The money has to come from less than half of the $20 million or so that state transportation officials receive in federal highway funds each year, Ishikawa said.

"Given the limited finances," Robertson said, "they're doing what they can."

HANDFUL OF PROJECTS

The DOT accepts bids on only a handful of seismic retrofit bridge and overpass projects each year, and "literally hundreds of companies bid," said Steve Baginski, president of Kalihi-based Kaikor Construction, which is wrapping up a $300,000 contract to retrofit the east-bound Vineyard Street H-1 on-ramp.

Kaikor specializes in building bridges around the state. But it's much more challenging and interesting to retrofit an existing bridge, Baginski said.

Because each project is unique, however, it can be difficult for a company to estimate its costs, Baginski said.

"It's an adventure," he said. "There's definitely not a lot of wiggle room for profit. Everybody's built a bridge from scratch before, but each retrofit project has to be custom-tailored. You can't just cut a hole in the freeway and pour the concrete in. It's hard to pour a new column under a structure all the way to the roof with an existing structure already in your way."

Even though the profit margins could be smaller with seismic retrofit work, Baginski said, "it's always worth it."

"We like the challenging jobs. And we definitely want to do more of them."

Reach Dan Nakaso at dnakaso@honoluluadvertiser.com.