Bridging a gap: safety vs. sightly
By Christie Wilson
Advertiser Neighbor Island Editor
HANA, Maui — A high-tech system that is being used to save Oregon's picturesque coastal bridges could be just the fix for corroding low-tech spans along the winding Hana Highway.
Photo courtesy Maui County
The system uses an electric current to control corrosion and has allowed public officials to save money and satisfy community concerns by rehabilitating historic bridges instead of replacing them.
The Hana Highway's Waikani Bridge near Wailua needs fixing, but repairing it without causing it to lose its character is a challenge.
The cathodic protection system is being considered for two significant arch bridges along the Hana Highway: the Waikani Bridge near Wailua and the Koukou'ai Bridge in Kipahulu.
Both the Oregon and Maui bridges are vulnerable to corrosion from salty ocean air. And both serve communities fiercely protective of local landmarks.
"We don't want any modern bridges," said longtime Hana businessman Carl Lindquist. "The character of Hana has a lot to do with the bridges. If the bridges all became modernized and widened, with yellow lines and sidewalks and everything else needed to meet federal highway standards, it would lose its character."
The Hana Highway Historic District is listed on the state and national registers of historic places. It has 59 bridges and eight culverts more than 50 years old. Most are one-lane bridges under state jurisdiction, with the county claiming responsibility for 14 bridges south of Hana town.
The East Maui community galvanized in the 1990s when an old wooden bridge in Kaupo, outside the historic district, was torn down and replaced with a 32-foot-wide concrete bridge that residents said was better-suited for Honolulu's H-1 Freeway.
Two other bridges, including Koukou'ai, were slated for a similar makeover, but the community let government officials know they would not allow that to happen.
In addition to concerns about preserving the area's rural character, residents worried that wider bridges would mean wider roads and more and faster traffic. There was also fear that better roads would open the remote area to further development.
In response, officials revised policies to favor preservation of the one-lane bridges as much as possible, or replacing them with structures of similar design. The county also developed a historical preservation plan for the Hana bridges.
Oregon Department of Transportation official Frank Nelson said it likewise took public outcry to get officials in his state to adopt a different approach to bridge repair.
Nelson, a former Navy Civil Engineer Corps officer who lived on O'ahu, has been invited to Maui to meet with state and county engineers and will make a public presentation on cathodic protection systems today.
He said that when the severely corrosion-damaged 3,011-foot Alsea Bay Bridge was to be replaced in 1988 by a simple
$20 million bridge, "the folks in Oregon didn't take kindly to that. The citizens demanded it be replaced with one as striking in design as the original."
The Alsea Bay Bridge, built in 1936, was designed by noted bridge engineer Conde B. McCullough, who designed the bridges along U.S. Coast Highway 101 in Oregon, and hundreds of others.
To meet public concerns, the bridge was replaced with a dramatic structure featuring a 450-foot steel-through-arch design for the main span at a cost of $44 million — more than double the original replacement cost.
"When we looked at other bridges having problems, the public told us, 'Don't do that again. Figure out how to save the bridges.' And that became the defining direction the State of Oregon has taken on the coastal highway bridges," he said.
The Department of Transportation was determined to avoid similar controversies and expense, Nelson said, and began developing a technology to protect the remaining McCullough-designed arch bridges from deterioration.
A bridge preservation team was created within the department. Nelson is the bridge preservation managing engineer, supervising a team of eight engineers and technicians who specialize in restoring Oregon's coastal highway bridges, movable bridges, covered bridges and painted bridges.
They proposed adapting a cathodic protection system for use on bridges.
Cathodic protection systems are used in Hawai'i and elsewhere in a variety of applications, such underground pipelines, docks, vessels and offshore oil platforms.
Nelson said the system protects metal, such as iron or steel, from corrosion in a salt-water environment by connecting it to a more "active" metal, such as magnesium, zinc or aluminum, which will corrode in its place.
Oregon bridge preservation engineer Frank Nelson will make a presentation at 6 p.m. today in the Maui County Planning Department Conference Room. Nelson will offer an overview of how Oregon developed technology to preserve its historic bridges while meeting modern traffic safety standards.
The "sacrificial" element, called an anode, must be periodically replaced to continue protecting the original steel or iron, which is called the cathode. The connection between the two metals may be direct, such as attaching zinc blocks to the steel hull of a vessel, or through a power supply that provides a direct current, which further transfers the corrosion activity from the cathode to the anode.
Oregon's Way
Nelson said the power demand to maintain the current is minimal, and engineers can monitor the systems from their offices via computers and make adjustments in the electric current as needed.
The initial cathodic protection will last 30 years, at which time the thermal-sprayed zinc that was applied to the bridges will have to be replaced, he said. One Oregon bridge rehabilitated 14 years ago using the cathodic protection system "looks like it did when we finished it," Nelson said.
The process was first used in Oregon on a full scale to repair and protect the 619-foot Cape Creek Bridge, patterned after a Roman aqueduct in France, at a cost of $2.5 million, a fraction of the expense of building a replacement.
Five other coastal bridges have been similarly rehabilitated, including the 3,223-foot Yaquina Bay Bridge. A sixth bridge is currently undergoing restoration and cathodic protection while still carrying traffic, and design work is starting for repairs to two other bridges.
The Maui bridges are nowhere near the scale and complexity of the Oregon structures, but with power lines running the length of Hana Highway, Nelson said the cathodic protection system would appear to be feasible.
The Koukou'ai bridge, built in 1911, is a one-lane reinforced concrete arch bridge 15 feet wide and 58 feet in length. The concrete arch Waikani Bridge, built in 1926, is almost 18 feet wide and 108 feet in length.
Dawn Duensing, a Maui County cultural resources planner, said the technology "could go a very long way in helping us preserve the beautiful structures along Maui's historic Hana Belt Road."
Nelson said the original designers and builders of the Hana bridges "could have built junk" but instead put "a lot of thinking and feeling" into the structures, which deserve protection.
"I hope county and state engineers will see this as a much clearer path than fighting with the public over replacing bridges," he said.
Reach Christie Wilson at (808) 244-4880 or cwilson@honoluluadvertiser.com.
