SCE to update Chino Hills, Calif., residents about TRTP underground construction

Southern California Edison (SCE) will hold a town hall meeting for resident of the city of Chino Hills, Calif., and surrounding communities Oct. 9 at Chino Hills City Hall to provide a project update on the Tehachapi Renewable Transmission project (Docket No. 07-06-031).

SCE will answer questions, discuss concerns and present various displays related to the undergrounding of the 3.5 miles of Segment 8A that will pass through the city. The displays are intended to provide information about the project and its impacts, the utility said in its announcement of the meeting.

Preliminary work has already begun on the portion of the project that will be placed underground. SCE said its crews have begun placing wooden survey sticks at various locations along the project area. Construction activities will take place in Chino Hills and the city of Chino, to the northeast, Mondays through Saturdays through 2016, according to the project website.

Other construction activities related to the actual construction of the TRTP segment cannot be performed until the California Public Utilities Commission (CPUC) rules on a Sept. 9 petition for modification of its July 11 order directing the undergrounding. In the original order, the CPUC directed the utility to study the possibility of changing the basic insulation level (BIL) rating for the underground line, but the utility has asked for permission to build the system with voltage control equipment included in the original design instead of undertaking a BIL study, which it said would significantly delay the in-service date of the TRTP, perhaps as late as 2019.

Originally, the TRTP was planned to enter service at the end of 2015 but SCE warned repeatedly during its lengthy battle with Chino Hills that undergrounding the line would place that deadline at risk.

Demolition underway

In late September, crews began dismantling 16 towers constructed to accommodate the overhead alignment originally approved by the CPUC when it approved the TRTP on Dec. 17, 2009.

Constructed in 2011, five lattice steel towers and 11 tubular steel poles along the 3.5-mile route will be disassembled differently than they were built.

“Lattice steel towers are more complicated to deconstruct,” Sandra Blain, SCE construction manager, said on the project website. “When built, the tower sections were bolted together under tension. To disassemble each tower, crews have to slowly remove the bolts connecting the sections before a 250-ton crane then separates each section, ensuring the tension is under control before bringing it to the ground.”

Removing the poles also requires a different approach than their construction. The crews will either use a large crane to pull the poles’ welded sections apart, or will cut each pole into three sections. Following each pole’s removal, crews will then remove part of the foundation that supported each pole. The foundations range in depth from 45 to 62 feet deep and will be removed to a level to support the underground structures yet to be built.

SCE expects to take approximately two workdays to remove each tower and another three days to remove or rework the foundations. The cost to remove the structures is estimated at $4m, according to SCE.

Calls seeking additional details from SCE were not responded to by press time Oct. 7.

When completed, the 250-mile, $2.5bn, 500-kV project will be capable of moving up to 4,500 MW of renewable energy from the Tehachapi, Calif., area to population centers in Los Angeles and San Bernardino counties in California.

SCE has called the Tehachapi project “a critically important, high-voltage transmission line, the timely completion of which is essential for California’s progress toward its aggressive renewable energy goals.”

California’s renewable portfolio standard calls for 33% renewable energy by 2020.

SCE is a subsidiary of Edison International (NYSE:EIX).