As the Manns Harbor Bridge over the Croatan Sound nears its 70th birthday, it’s getting what North Carolina Department of Transportation Resident Engineer Pablo Hernandez recently called “the first major renovation that I’m aware of in my 28-, almost 29-year career here in Dare County.”

The bridge, he added quickly, needs work, but overall, “the fact is that we got almost 70 years out of it without a tremendous amount of maintenance investing.”

Hernandez also added that the work that had been done, mainly minor concrete repairs and a paint job about every 25 to 30 years, “but the current project seems to be the most complete.”

When the William B. Umstead Bridge, as it is officially known, opened to traffic in December 1956, Outer Banks newspaper the Coastland Times described it as “a fine Christmas present for the Southern Albemarle region,” adding that it “will make possible a lot of holiday visiting, particularly on the Dare County mainland.”

The bridge connects mainland Dare County with Roanoke Island and the Outer Banks. This delivered 20th century amenities to the isolated hamlets and towns of mainland Dare County that had yet to be electrified. With the bridge carrying connections for electric power and telephones, “some eight families will have electric lights for the first time” in the sleepy fishing village of Mashoes. And in the longstanding, unincorporated Manns Harbor community, “the bridge makes possible modern telephone,” the Coastland Times reported.

Although the bridge may appear to be in surprisingly good shape, it is a solid 40 years beyond its expected lifespan, and when the $33.75 million project began in summer 2023, uncertainty remained about the extent of repairs needed.

The original price tag has risen: “Estimated projections of total costs are currently around $45 million,” Hernandez wrote in an email. “We are doing what we can to control the costs but not to the detriment of the structure.”

“Until you’re there, you don’t know what you’re going to find, just like with an old house,” Hernandez said, “you start renovating it, and things need attention.”

The project is a blend of modern materials and traditional, often hands-on applications. Resurfacing the deck, for example, was completed using an epoxy that included an aggregate material to provide a textured surface. During the application process, the bridge was closed for nine months.

“All of those layers of the epoxy, as well as the aggregate to provide the textured surface, were all applied by hand, so over 300,000 square feet of bridge deck was rolled and squeegeed with these four separate layers of epoxy,” Hernandez explained.

The decision to apply the new surface in this way, instead of using “specialty trucks and pavers,” was in part because of the bridge’s 70-year-old design and the weight of the materials. “We don’t put a lot of what we call dead load on the bridge,” said Hernandez.

Other factors were also considered. “The deck was in surprisingly solid, good condition,” Hernandez said, “so there was no need to remove an inch just to put back another inch.”

The epoxy used is a viscous material that seals any cracks that may have developed.

Hernandez said the bridge design has a “certain robustness to begin with. It’s kind of like building a a deck on your house when you use a six-by-six post or an eight-by-eight or four-by-four post.”

Home to purple martins, pre-dedication damage

The bridge has for years been home to thousands of purple martins during summer. Hernandez, in response to Coastal Review’s query, was emphatic that the birds’ droppings had not damaged the bridge. He pointed out that the aerobatic birds roost on the bridges steel beams and atop the caps, concrete members that support the steel beams and are only there at night.

“From my experience, we have not seen a tremendous amount of bird droppings,” he said. Hernandez cited as evidence one night when he was with the Purple Martin Society conducting bird surveys. “We provided a boat and there were hundreds of thousands flying around. I don’t think anybody got nailed (with droppings).”

The most recent work has been below the bridge deck and the view down there is concerning. On the north side of the bridge, toward the mainland side, an entire piling is missing. In its place, iron girders support this part of the bridge. A March 1957 storm took out the piling before the bridge was officially dedicated the following month.

A grain barge, the C. W. Curlett “struck the bridge when it got out of control, said to have been due to the failure of one of the two motors. It swung down and struck the North side of bridge, shattering one of the huge concrete piles, so that the reinforcing steel inside it was exposed and bent,” the Coastland Times reported.

Just to the east of the bridge’s center rise, workers have been lowered to assess its condition. One worker taps the concrete with a hammer while another makes notes of their observations.

“They are listening for a hollow or dull sound,” Hernandez explained. “This indicates a deteriorated concrete layer.  If it is solid, it will have a distinct sharp, pinging sound.”

Repairs to the concrete pilings are now the project’s focus. The concrete is showing its age, largely because of the limited materials available in 1956, as compared to current designs. The bridge pilings, Hernandez said, were only “mildly” reinforced. “It just has reinforcing bars in it.”

The reinforcing bars, or rebar, is exposed through cracks in the concrete. Repairs involve removing any rust from the iron and replacing the concrete. Although there is visible rust on the rebar, the one-inch bars are still in good shape with only basic maintenance needed to clean the rust and repack the concrete.

Hernandez compared the Manns Harbor Bridge pilings to those supporting the nearby new Lindsay C. Warren Bridge, aka the Alligator River Bridge, a project to replace the early 1960s-era structure that Hernandez also supervises. The pilings there are prestressed, by “basically taking a very dense and durable cable and stretching it, pouring concrete around it, and then letting that elastic force come back in (and) help squeeze the concrete together, so you get a denser piling that can go through a lot more cycles without any kind of cracking.”

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The cracks in the Umstead Bridge were not unexpected after seven decades. Temperature variations and cycles of freezing and thawing in a marine environment will cause the material to develop small fissures. Once air reaches the rebar, the iron begins to rust. Conversely, below the surface of the water, in what is considered anaerobic conditions, “the concrete is dense and sound, and the rebar is protected from water and oxygen,” Hernandez replied in an follow-up email. “The majority of the deterioration of the concrete and rebar is in the splash zone where there his ample oxygen to facilitate the corrosion process of ferrous metals.”

Repacking the piling concrete is one of the most labor-intensive, hands-on parts of the project. After removing the damaged concrete and cleaning the rebar of rust, barges form a protected area around the work zone under the bridge. On a barge deck, workers mix Speed Crete Blue Line, a product described by Hernandez as a “rapid-setting underwater concrete repair mortar.” According the manufacturer, Euclid Chemical, the product will set in three to five minutes after coming in contact with water.  

Three divers are also employed in the repairs, reaching into buckets of mortar, pulling out a handful and pushing it into the voids and continuing the process until the piling is back to its original specs.

The mortar creates an airtight seal, protecting the rebar inside the piling. Then the pilings get an additional layer of protection.

“After we do the concrete piling, we come back with an epoxy-saturated carbon-fiber sheet of fabric and wrap that around the piling shell,” Hernandez said.

The bridge is considered one of the state’s “high-value bridges,” Hernandez said, referring to bridges within a $50 to $70 million range replacement cost.

Hernandez noted an NCDOT assessment of the bridge that asked, “Could we invest in a significant bridge preservation effort to get another 20, 30 or 40 years of life out of those structures?”

The repairs, Hernandez said, are going well, but the work originally slated for a Nov. 26 completion date that is “around the corner,” is unlikely to wrap up as scheduled. “Unfortunately we’re not going to be complete with the concrete repairs.”