transmission line relocation
transmission line relocation
transmission line relocation
transmission line relocation

Transmission Line Relocation for Cranes

When NC State Ports ordered two neo-Panamax cranes from China, McKim & Creed was tasked with transmission line relocation to accommodate the 151-foot-tall machines.

It took two months to ship the cranes from China to Wilmington, but eight months to plan the logistics surrounding their arrival. The cranes were so wide that a portion of the Cape Fear River had to be shut down to all commercial and recreational activity to accommodate the shipment. And they  were so tall—at 151 feet, each crane was literally the height of the Statue of Liberty minus the foundation—that they were unable to pass beneath two 230-kv transmission lines that cross the river near the Ports.

The Ports explored the option of modifying the structure of the cranes to make the legs shorter, but it wasn’t structurally viable. There was only one solution. Raise the high-voltage lines above the height of the cranes.

Ports officials assembled a team to plan and execute the complex delivery. The U.S. Coast Guard handled navigation and safety while the Cape Fear River was closed to traffic. The New Hanover County sheriff’s department provided security along the river. Meteorologists tracked the weather forecasts, because winds as high as 15-20 knots would make the entry into the Port too dangerous. River pilots were tasked with guiding the cranes into port, while the U.S. Army Corps of Engineers provided hydrographic surveys in the channel under the transmission line to verify depths.

Duke Energy was responsible for de-energizing and raising the transmission lines. And McKim & Creed was charged with ensuring that the lines were raised high enough to accommodate the cranes’ height.

“We started our surveys in February so we could tell how high we would be able to raise the lines,” said David Jones, PLS, CFS, regional manager with McKim & Creed. McKim & Creed surveyed the area again after the northern conductor line was de-energized. A final survey was conducted the day before the delivery, when the southern conductor was de-energized and raised 10 feet. “We were estimating the clearance to be 10 feet,” David said.

On the day of delivery, David and his crew watched from nearby. “There was no room for error,” said David. “It was an anxious moment for everyone.” The passage of the cranes beneath the lines was successful—with a few feet to spare.

The new cranes allow the Port to handle more container traffic by simultaneously accommodating two of massive ultra-Panamax ships now calling at East Coast ports. These ships are the result of the 2016 Panama Canal expansion, which doubled the canal’s capacity and allowed larger ships to pass. They can carry twice the cargo of the smaller, older ships, and are about one and a half times the size.

Project Details

Client NC State Ports
Location Wilmington, NC