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Oregon bridges to get high tech treatment

GOLD BEACH – Oregon's signature coastal bridges are undergoing a high-tech retrofit designed to short-circuit the natural process of corrosion and extend their useful lives by decades and perhaps centuries.

The state Transportation Department is midway through a 30-year, $200 million program to preserve a string of arched seaside bridges built by legendary civil engineer Conde B. McCullough that have become Oregon icons.

The landmark 1,932-foot Isaac Lee Patterson Bridge across the Rogue River is the seventh and latest of the bridges to be coated with zinc and then electrified. The electrochemical process draws corrosive ions away from the reinforcing steel so that they instead corrode the easily replaced metallic surface.

"The basic idea is, if you run current in the opposite direction of corrosion, you stop corrosion," said Frank Nelson, interim bridge engineer for ODOT. "The beauty of this is, it's sort of like a Botox treatment for this grand dame. We make the wrinkles go away, and they stay away."

But impressed-current cathodic protection, as the process is called, entails far more than a skin-deep face-lift, project engineer Dave Fletcher said.

Inside a containment building 40 feet wide, 65 feet tall and 260 feet long that hangs 20 feet above the Rogue River, the concrete bridge is sandblasted. Workers then examine every inch of the bridge's 360,000-square-foot surface.

"This bridge has been touched a lot. Probably nine or 10 times it's been touched before we're done," Fletcher said. "That's a lot of hands on."

The tools used in the examination range from hammers that test the concrete - when beaten, good concrete goes "ding," Fletcher said, and bad concrete goes "thunk" - to sophisticated detectors that record the extent of the corrosion on the steel reinforcing bar, or rebar, buried inside the concrete.

Crucial to extending the life of the bridge is making sure every piece of rebar within the concrete touches another, so the electrical current flows through every inch of steel.
ODOT engineers will control the low-voltage electrification of the bridge from Salem, tracking the rate of corrosion with monitors inside and outside the bridge and adjusting the electricity as needed.

The new wiring, as with most elements of the four-year, $18 million project, is invisible to the thousands of passers-by who cross the bridge each week. Most of the action is taking place below the road deck.

From a distance, what is most noticeable is the 1932 bridge's new color: silver-gray with the patina of well-rubbed pewter.

Up close, the most visible aspect of the project is a new railing along the highway deck. The railing replicates the original bridge's purely decorative accents, which have made McCullough's coast bridges landmarks of Art Deco design.

But the new rail also contains structural steel to meet modern federal requirements for highway safety.

The effort to preserve the McCullough bridges dates to the 1970s, when ODOT maintenance crews concluded that coastal bridges were corroding faster than they could be repaired.

In the 1980s, ODOT bridge builders discovered that 50 years of salt air had left McCullough's 1936 Alsea Bay Bridge in Waldport too damaged for rehabilitation. The bridge was replaced in 1991 at a cost of $44 million.

"That gave us a big heads-up that if we were going to save any of these coastal bridges, we were going to have to do something pretty substantial and pretty quickly," said James Norman of ODOT's cultural resources unit.

The department formed an engineering team that was charged with figuring out how to restore the bridges to their original condition and preserve them from further deterioration.

Cathodic protection had long been employed on buried pipelines, but state engineers joined others experimenting in California and Florida to perfect the method for use in above-ground structures.

At the same time, local boosters, state tourism officials and transportation historians drew attention to the historical importance of McCullough's bridges.

In 1982, the American Society of Civil Engineers named Gold Beach's Patterson Bridge, built in 1932, a national historic civil engineering landmark.

Now the Transportation Department is preparing to nominate six of McCullough's coast bridges - those at Gold Beach, Coos Bay, Reedsport, Florence, Cape Creek and Newport - as individual national historic landmarks, and all of the Oregon coast highway's arched bridges as a themed group in the National Register of Historic Places.

"These historic bridges are very much of an event on the coastal highway," Norman said. "Our coastal highway and these coastal bridges are a major tourist destination."

Transportation historian Robert W. Hadlow encountered McCullough's bridge at Gold Beach as a graduate student in 1990, when he joined five architects and three historians to document the Isaac Lee Patterson Bridge for the National Park Service's Historic American Engineering Record.

He went on to make McCullough the subject of his doctoral dissertation, which was published as "Elegant Arches, Soaring Spans" by Oregon State University Press.

"That bridge in Gold Beach was one of the big ones that really put him out in the forefront and used cutting-edge technology," Hadlow said, noting that it was the first U.S. bridge to use French engineer Eugene Freyssinet's method for pre stressing concrete structures.

"The goal was in a sense a cost-saving measure, because you'd use less concrete," Hadlow said.

"But the other end of it was, you'd end up with a bridge that was very light, very thin and very artistic.

"His philosophy all along was, if you could do it and the site warranted it, to incorporate some of these architectural elements to give the bridges a beautiful appearance. He's looking for something that just floats across."

McCullough, an Iowa native, came to Oregon in 1916 to teach at Oregon Agricultural College and became head of the state's bridge department in 1919.

During the next 13 years, he oversaw construction of nearly 600 bridges in Oregon, including 162 that he designed. In the mid-1930s, he led the construction of suspension bridges in Panama, Guatemala and Honduras. McCullough died in 1946.

Engineers and historians agree that McCullough's genius was to marry engineering innovation with an artistic vision to create light and airy structures that bridge the crossings between Oregon's rugged coastal headlands like skipping stones skimming across the water.

"One might call McCullough both the consummate bridge engineer and one of the world's true bridge architects," Nelson said. "He brought art and engineering together in a way nobody else has."

By 2022, when the Transportation Department expects to begin preservation work on McCullough's Umpqua River Bridge in Reedsport, it will be time to begin reapplying zinc to the exterior surfaces of the 10 other bridges that will have received cathodic protection.

At a minimum, engineers expect the high-tech retrofit to keep McCullough's coast bridges in use for another 70 years. And they hope future innovations will extend their lives for centuries to come.

"I think our grandkids will be, on the one side, demanding that we keep them," Nelson said.

"And on the other side, they'll be sharper engineers who can figure out other technologies that we can do to make them last."