Bridge Work: Coatings Dive Deep
By Jen Kramer
Carolina Marine Structures
8443 Caratoke Highway, Suite A
Powells Point, NC 27966
American Concrete Institute
38800 Country Club Drive
Farmington Hills, MI 48331
Structural concrete patch
750 Commerce Drive
Fairfield, CT 06825
Neptune Research Inc. (NRI)
1346 S. Killian Drive
Lake Park, FL 33403
Until recently, The Lucius J. Kellam Jr. Bridge-Tunnel, more popularly known as the Chesapeake Bay Bridge-Tunnel was also known as one of the “Seven Engineering Wonders of the Modern World,” joining the Golden Gate Bridge and the Panama Canal on the list of structural marvels. Although the “aging technology” has been replaced on the official list, the achievement behind it remains impressive: the location, daunting. This fact became immediately apparent to the coatings crew charged with repairing and recoating the bridge’s 54" (137.16cm) concrete piles after they were badly damaged by a run-away barge.
The Bridge-Tunnel crosses Chesapeake Bay, carries US 13, the main north-south highway on Virginia’s eastern shore and is the only direct link between the eastern shore and South Hampton Roads, Virginia. Spanning 23 total miles (37km), the Bridge-Tunnel features dual one-mile (1.6km) tunnels, dual bridges, four man-made islands, 12 miles (19.3km) of low-level trestle, and two miles (3.2km) of causeway. According to its owner, the Chesapeake Bay Bridge and Tunnel Commission, the four lane Bridge-Tunnel is “the largest Bridge-Tunnel complex in the world.” In addition to heavy traffic, located at the mouth of Chesapeake Bay, it is also subjected to strong tides from the Atlantic Ocean.
Those tides create stress on the Bridge-Tunnel’s concrete columns under normal conditions. After the barge incident, 85 piles had been rubbed by the run-away barge and four were badly damaged. Each crashing wave removed more concrete and further exposed the rebar support structure. If the erosion wasn’t halted, it could potentially weaken the integrity of the entire structure. The Commission needed a solution to their growing problem.
They found their solution based on the American Concrete Institute’s (ACI) 440.2R requirements for strengthening the flexural and compressive characteristics of the damaged concrete piles using a fiber-reinforced polymer system. The system ultimately specified was Titan-Saturant Epoxy and Titan-218 carbon fiber from Neptune Research Inc. (NRI). The coatings contractor chosen to apply it was a crew of certified commercial divers from Carolina Marine Structures, led by John Porter.
Time And Tide
Located in North Carolina, Carolina Marine Structures provides marine design, engineering, and construction services and, with multiple government and Department of Transportation (DOT) contacts, was an apt choice for the high-profile project.
The crew was given eight weeks to complete the coatings project, two of which were consumed by the extensive permitting process. “Depending on the type of work, the size of the crew varied between six and 15 men,” Porter says. There were a lot of variables that affected the job, but the main one was the site itself.
“The mouth of the Bay is large,” Porter describes the unique jobsite. “Sometimes it was gorgeous and calm and we’d see whales and dolphins. Sometimes we were faced with strong currents of 10 to 15 knots--which is pushing 18 miles an hour (29km)—and then the divers would work, tethered to poles, with their bodies straight out behind them. Sometimes it was just too rough and we’d have to come up. The average dive is an hour, but not if you’re fighting a strong current.”
Even with a flat tide, “this was an extreme environment,” Porter continues. “The boat was roped off. The divers were tethered with nylon ropes and harnesses. Sometimes when the tide was rough we worked inside aluminum cages and those were roped. The piles themselves were roped. It was like a spaghetti warehouse in the water.”
The worst damage was located about 40' (12.19m) deep at regular tide. “At low tide, the damage was at surface level, but some areas of damage went as deep as 80' (24.38m)” Porter says. “The deeper areas were the easier ones to work on. It was the splash zone that was the most difficult.”
Not only did the crew have to contend with fluctuating tides, they had to keep an eye on both the ambient conditions and the water temperature. “The job took place in early winter. The specified coatings would not cure in water below 40°F (4°C),” Porter recounts. “The temperature never dropped below 42°F (5°C) the entire time. It was intense. We got lucky.”
Porter and crew may have gotten lucky on the cure, but the cold temperature did influence their dive times. If the current was too rough or the temperature was too cold, Porter made sure that his crew stuck to hour-long shifts in the murky water. “In extreme conditions, the average dive is an hour, period,” Porter says. He has been in and on the Bay himself for the last 20 years. “I basically grew up in and on these waters,” he explains. “So I have a real respect for the area and for what my crew faces.” In fact, Porter made the dive himself—this is one crew that is literally in the same boat when it comes to the work load. “Safety comes first and foremost every day, every dive.”
Whether 80' (24.38m) below the water’s surface or in the bright sun, the coating process was essentially the same. First, if it was exposed, the crew cleaned the area to be coated using a 5,000 psi pressure washer powered by a Honda generator. “This part got a little tricky simply because fish swim close to eat the dislodged barnacles and the gunk that is removed from the pile,” Porter says. “Then we attached anodes to any exposed metal to stop electrolysis.”
Next it was time for Five Star Products’ structural cementitious concrete patch. “We used our hands to pack meatball-sized bits of the patch into the damaged areas and to smooth it out as the piles’ circumference would not accommodate a trowel. Some damaged areas are 1' (0.3m) and some are 1 ½' (0.5m). It took several meatballs to fill in one area. We did this procedure at low-tide because the tide will erode the soft “meatballs” from the holes.”
Once the patch was in place, Titan Saturant Epoxy was then applied over the repair area to completely encapsulate the column’s circumference. The two-part, 100% solids epoxy is designed for use with Titan’s carbon-fiber wrap and comes in pre-measured kits. This meant that the crew did not have to worry about measuring product on the bobbing boat.
“We saturated Titan’s 218 Carbon-Fiber wrap with epoxy in a specially-designed 2' by 4' (0.6m by 1.2m) trough,” Porter describes the process. We put the carbon fiber in the trough, pour the epoxy on top, squeegee, flip over and repeat. Then we’d wrap it around the pile, overlapping by 2' (0.6m).” Typically, this process continued to a repair height of 12' (3.7m), 6' (1.8m) above the water line and 6' (1.8m) below, and applied to the column in a circumferential manner. The carbon fiber wrapped piles were covered with shrink wrap for protection until a fiberglass jacket could be installed. With the epoxy and the jackets, the Titan repair system restored and reinforced the piles while adding flexural and compressive strength.
Although the Bridge-Tunnel may no longer be on the official list of engineering marvels, it remains an impressive achievement. The coatings work of the crew from Carolina Marine Structures is also an impressive feat. Using NRI’s system, the divers completed a challenging repair with minimum resources in adverse conditions. That is truly a wonder of the coatings world.
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