HALE'IWA — The people of Hale'iwa may be happy to know that Matt Blackburn has a sense of history.

"One of the things I tell the guys every morning when we have our meeting is that this bridge has historical significance," said Blackburn, 33. "This is something that you can come and appreciate for the next 40 or 50 years."

Blackburn is project foreman for a $2 million renovation of Hale'iwa's Anahulu Stream bridge — built in 1921 and famously known to locals and visitors as the Rainbow Bridge.

For years the North Shore landmark had been crumbling and cracking. Rusting interior steel bars were expanding and popping chunks of concrete off the columns and into the ocean.

The city patched it up over the years, but this time it will be a complete overhaul, said Blackburn, who works for KAIKOR Construction.

Blackburn and his crew have engineered a way to avoid restricting the narrow, two-lane bridge — a linchpin of community and tourist traffic — to a single lane for six months.

Realizing that with so much tourist traffic on the North Shore, vehicles would be backed up for miles, workers built screens to catch the flying concrete and allow two-lane operation.

The mauka side of the bridge is nearly complete. On the ocean side, workers continue to man jackhammers and dodge debris.

Yet to be completed is the trestle's under portion — the most difficult work of all, according to Blackburn. Five floating scaffolds have been built to accomplish the task.

The project is expected to be finished in time for Christmas. Until then, traffic on the narrow bridge will remain two-lane — except, of course, when wide trucks or buses cross over and, as has been the case for decades, two-way traffic briefly comes to a halt.

"The community is happy that the bridge is being repaired and that both lanes will remain open," said Antya Miller, executive director of the North Shore Chamber of Commerce, which uses the Anahulu bridge as its logo.

Community activist Meryl Andersen, who had long advocated repairing the bridge, was so happy that she let the crew have the use of her land adjacent to the bridge as a construction yard.

"I was on the Neighborhood Board and every time the subject came up, I would always mention the bridge," said Andersen, adding that the span is listed on the National Historic Register. "The last time they patched it up was years ago.

"This time it will last for a hundred."

In 2003 there was concern that the bridge might have to be closed because cracks in the columns had become so wide, the rusting steel reinforcement bars, or rebars, were exposed to the elements.

However, city officials assured the public that the bridge was structurally sound and would not need to be closed before this year's construction project got under way.

Blackburn agreed that the bridge is still sound, although he said the crossing had deteriorated more than originally thought.

"From a hanger standpoint, it was a safety concern," said Blackburn. He demonstrated by twisting an exposed and badly rusted rebar with his bare fingers.

The bridge's columns, or hangers, do not hold up the bridge's familiar arches. Blackburn said that the columns hang from the arches and that the load of the deck itself is suspended from the columns — much as how San Francisco's Golden Gate Bridge functions.

"It was really bad," he said. "When we started chipping away the concrete, we quickly realized that several times workers had tried to repair the bridge by patching it up, and it hadn't worked."

Over time, the underlying problem had grown worse.

"These are actually new concrete columns," Blackburn said, slapping one of the finished hangers on the mauka side. "It's not just the old columns patched up to cover up the cracks."

Still, many of the original reinforcing steel bars remain in place — cleaned of rust and coated with a protective seal that should keep them rust-free for decades. Where new rebars were required, they're of a special fiber that won't rust, Blackburn said.

When it's finished, Rainbow Bridge will look virtually identical to the way it did the day it opened more than eight decades ago, except that its curbing and railings will be slightly higher for safety reasons.

Meanwhile, the dust and noise kicked up by the work is OK by Joe Lazar, who owns Hale'iwa Joe's on one side of the bridge and who lives in the first home on the other side.

"We're stoked about it," Lazar said. "Most people who knew about the state of the bridge are going, 'It's about time, man.' It's good for Hale'iwa.

"As for me personally, to get awakened by the sound some mornings — even after some late nights — hey, it's no problem. I'm just glad it's finally getting done."

Reach Will Hoover at whoover@honoluluadvertiser.com.