First Sunrise Powerlink Tower Completed

Tower “Bridge” Section Airlifted into Place, Signaling Major Project Milestone

The first 142-foot Sunrise Powerlink transmission tower was completed March 9, near McCain Valley Road in Boulevard, just north of Interstate 8. This tower was completed by air using SDG&E’s “Sun Bird” helicopter and demonstrates that overhead tower construction has shifted into high gear.

The Sun Bird flew the first component to be set by helicopter, the tower bridge, from the nearby Rough Acres Ranch and hovered atop the tower for only about a minute before deftly placing the bridge squarely into position. 

“The entire SDG&E project management and engineering team, as well as the PAR construction crew should be very proud of how smoothly this procedure went,” said Bob Jackson, general manager and director of construction and engineering for Sunrise Powerlink. “All the months of engineering, advanced planning and assembly preparations paid off as the entire bridge setting operation, which requires absolute precision fitting of parts and extraordinary flying skills, took only moments to complete. It was a text book operation all around.”

The completion of the tower stands as a significant achievement and is the jumping off point for extensive aerial construction related to the project.  Although only the bridge was set with the helicopter on this structure, over half of the 421 towers along the 117-mile route will be completely installed via helicopters. The next bridge expected to be flown by the Sun Bird is Tower EP 244 in Jacumba.

How’d they do that?
This first tower bridge setting only took about five minutes from start to finish because of the outstanding crew and the intense planning put in beforehand. Here is a very simplified outline of how they did it:

• Concrete footings are poured and set for approximately two weeks.
  
  
• Once the concrete has cured and achieved minimum required strength, the tower assembly begins. The tower legs and body components are set using a crane from the ground.
  
  
• The Sun Bird sky crane picks up the entire tower bridge via a specially designed lifting apparatus. A special anti-rotation device keeps the bridge stable in the air so there is no swinging or movement of any kind.
  
  
• A spotter helicopter (yellow in the accompanying video) monitors the position of the Sun Bird as it maneuvers the bridge into place.
  
  
• The spotter aircraft’s job is to “call the load” by constantly providing a steady stream of instructions to the Sun Bird crane operator and pilots so they can adjust elevation and direction of the tower bridge.
  
  
• When it’s perfectly aligned, the tower bridge is set on the brackets.
  
  
• When confirmation is given by the spotter, the slings are electronically unlocked.
  
  
• Next, a crew from PAR, the project’s construction contractor, climbs the tower and installs splice plates and back bolts the bridge into place to secure it.
  
  
• Finally, the bolts’ torque is checked for quality assurance and quality control.

Did you know?

• The tower bridge is the top portion of the transmission tower that supports the wires and insulators.
  
  
• The steel in the tower weighs about 40,000 pounds
  
  
• The tower bridge weighs about 14,000 pounds
  
  
• Each of the three strings of insulators on the bridge weighs an additional 1,000-1,5000 pounds
  
  
• The official tower name is “EP 217”

With the completion of this first overhead transmission tower by the Sun Bird, the San Diego region is one step closer to its clean energy future.  The Sunrise Powerlink will enhance reliability, transport vast amounts of clean, renewable energy and boost the local economy through project expenditures and job creation.  The project is expected to be completed in 2012.