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
"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
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
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
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