The pop-pop of chopper blades and the sight of helicopters ferrying transmission line towers and heavy equipment to and from the Cuesta Grade are common these days in San Luis Obispo as Pacific Gas and Electric Co. finishes a three-year transmission line upgrade project.
The utility is upgrading its 70 kilovolt transmission lines from Atascadero over the Cuesta Grade to San Luis Obispo. The $36 million project includes replacing 132 wooden utility poles with light-duty steel poles, and replacing 41 out of 45 steel transmission towers.
Work began in 2011, is 70 percent complete and will wrap up this year. The purpose is to protect the transmission lines from such environmental degradation as salty air and fire with the goal of increasing grid reliability, said Lee Ellis, project manager.
The first phase of the project included installing new transmission tower foundations and tower bases along an existing 8-mile stretch of line from the top of the Cuesta Grade to PG&Es San Luis Obispo substation, and replacing four towers with tubular steel poles within the city of San Luis Obispo.
The first phase also included replacing about 60 percent of the existing wood poles from the Atascadero substation to the top of Cuesta Grade with light duty steel poles. The new steel poles are not susceptible to fire, Ellis said.
The final phase of the project involves replacing the existing steel towers and remaining wood poles, and then installing new lines along the 16-mile stretch from the Atascadero substation to the San Luis Obispo substation. The transmission towers will also be strung with new aluminum line, which is cheaper and weighs less than copper.
This final phase will use multiple helicopters transporting the new towers and crew members to the various locations along the Cuesta Grade where ground crews will complete the installations, Ellis said.
The old equipment dates to the 1930s. The new equipment could last a century.