Transmission Towers in Chino Hills Safely Demolished to Make Way for First 500-Kilovolt Underground Transmission Line in the United States

The high-voltage underground transmission line is part of the 179-mile Tehachapi Renewable Transmission project.

November 26, 2013 | By Paul Klein

Before Southern California Edison (SCE) constructs the first 500-kilovolt underground transmission line in the United States through a portion of Chino Hills, it had to remove large tubular steel poles and lattice steel towers along the 3.5-mile underground route. 

The 11 poles, five towers and accompanying foundations were built in Chino Hills in 2011 to support the interconnection of SCE’s Tehachapi Renewable Transmission Project overhead line, before the California Public Utilities Commission ordered the company to underground.

When completed, the 179-mile Tehachapi project will run through a number of Southern California communities and will be able to deliver up to 4,500 megawatts of largely renewable energy, enough electricity to power three million homes.

Sandra Blain, SCE principal project manager, said that while different processes were used to bring the poles and towers down, crews removed these structures at a rate of one every two days, with the entire demolition taking about two months.

“A torch was first used to cut the pole cross arms, which would have carried the overhead transmission line,” said Blain. “Using the torch, workers then cut the 200-foot-poles into 35-foot sections before using cranes each with a lifting capacity of 250 tons to bring the pole sections to ground. The pole sections were then taken to a salvage/recycling center in Anaheim.

“Two cranes, working in tandem, were required to remove each pole, one to hold the workers in a man lift to cut the poles, and the other to keep the poles stable,” she said.

Removing the towers presented a special challenge. Unlike the poles, the towers were installed under tension, which was created when workers bolted pieces and sections of the towers together. The tension resulted from tightening 5,000 to 7,000 bolts on each of the five towers.

“Our crews took great care to very slowly unbolt each section in order to control the release of tension,” said Blain. “Workers slowly and methodically removed each section as the company will use these tower sections to construct other transmission projects.”

Jennifer Wolf, SCE project manager, who daily managed on-site activities associated with the project, said the demolition of the poles and towers was accomplished by five, five-man crews.

“Our work attracted a great deal of neighborhood attention. Once the work fell into something of a routine, the project moved along smoothly,” said Wolf. “It was fascinating to watch how quickly the crews came together, working as coordinated teams to bring these structures down.”

Once the structures were demolished, SCE then removed major portions of the concrete foundations that supported each pole and tower. Wolf said the crews first broke the concrete foundations apart and then removed them to depths of five to 20 feet, depending on the location of the structure.

Blain noted that as with all work done at SCE, the project reflected the highest commitment to safety.

“Safety zones were established to ensure public safety, and crews met daily to assess potential safety risks before implementing the appropriate procedures,” she said. “Monitors continually were on site to ensure a safe work environment.” 

While both Blain and Wolf emphasized that the project was a team effort — ranging from lawyers to engineers to project managers — the project’s uniqueness was also reflected in the fact that this one-of-a-kind demolition was managed by two women.                

Topics: Safety