North Carolina’s coastline is one of the most vulnerable for a direct hurricane strike facing the Atlantic Ocean due to its protruded coastline. Factor in low-lying land, the Lumber, Pee Dee, and Cape Fear rivers, and the potential of catastrophic flooding is very high. In 2016, Hurricane Matthew stalled across the region keeping inland waterways above flood levels for weeks. Less than two years later, Hurricane Florence struck southeast North Carolina dumping more than 25 inches of rain. As a result, multiple Duke Energy substations were inundated with flood water and power to much of the region was out. Technicians were unable to begin making repairs until the water receded. This left substations down for more than five weeks, leaving thousands of Carolina residents without power.
Having faced a pair of “Storms of the Century” in two years, Duke Energy had to develop a solution to protect their substations from flooding. After failed attempts to raise the substations and construct a temporary flood wall, which was destroyed by Hurricane Florence, Duke Energy needed a permanent solution. Ultimately Duke Energy chose CMI’s UltraComposite FRP and ShoreGuard vinyl sheet pile due to the material’s longevity, non-conductivity, and lower total cost of ownership compared to steel or concrete.
“We put a lot of thought, did a lot of research, went around the country to see what other utility companies were doing in this space,” Duke Energy Corporate Communications Director, Ryan Mosier says. “We learned that we are the first utility to do this type of effort.” One of the sites Duke Energy visited was the Atlantic County Utilities Authority (ACUA) wastewater treatment plant and wind and solar farm in Atlantic City, NJ. The ACUA project utilizes a 4,896 linear foot flood wall built with CMI’s UC-95 UltraComposite (FRP) Sheet Piling. CMI’s PileClaw Steel Mandrel was employed to help drive the UltraComposite sheets into the ground. The same equipment and methods were utilized for Duke Energy’s seven substations.
Sheet pile installation began in June 2020 and each of the seven sites presented its own challenges. Gary Greene Engineers, with assistance from CMI’s Engineering department, was the lead engineer on the project. Construction was completed by HEPACO, Langston, and Cianbro. ShoreGuard 950, UltraComposite 50, and UltraComposite 75 synthetic sheet pile profiles were ultimately chosen based on site-specific soil parameters and varying flood wall height design requirements. The seven flood walls extend six to eight feet above grade at each site and the sheets were driven to varying depths utilizing CMI’s PileClaw mandrel to drive the sheets accurately and increase daily production. Removable aluminum gates allow crews access to the sites and can be quickly installed ahead of any forecasted flooding. TimberGuard® walers were installed at the top and each side of the flood walls to add strength.
After dealing with two catastrophic “Storms of the Century”, resulting in millions of dollars of damage, loss of life, and extended periods of power outages, Duke Energy has stepped up its commitment when it comes to protecting the substations.
“We’ve had a struggle the last few years with the flood waters getting into the substations, but Duke Energy really stepped up to the plate,” Duke Energy Supervisor, Davy Gregg says. “They put a big investment in the community, and it really helps us out.”
Now Duke Energy’s infrastructure is more protected for when the next hurricane or flood event strikes the coast.
