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Flurry of Big and Tall Engineering Hits the South End

lattice tower google view2City Light workers had a busy week of big and tall engineering near Seattle’s south end, all in an effort to make our transmission system safer.

Between July 21 and July 24, City Light workers and engineers straightened out a leaning 150-foot transmission tower, installed a massive metal pole in the middle of a rail yard, and replaced an aging wooden transmission structure in a wetland.

The work was performed during a planned outage of a major transmission corridor, near Interstate 5 south of Boeing Field, and over a busy train corridor. It required a delicate dance of permits, agreements with regional agencies and community outreach in a diverse neighborhood with territorial views.

All of it is part of a larger project to upgrade the aging structures and cables connecting the Creston-Nelson substation in the Rainier View neighborhood with the Duwamish substation to the west.

The first and probably trickiest part involved a transmission lattice tower on the west side of I-5, near the Martin Luther King. Jr. Way exit. During planning for replacement of adjacent poles, engineers discovered that the tower’s foundations gradually sank over the past 30 years, causing it to lean three feet to the side.

Crew chiefs Tolattice shimdd Warren and Bruce Lee, their crews, and Ironworkers Curt Blazich, Shaina Cornelius and Justin Forrest took on the job, with planning and design by Civil Engineers Norm Hodges and Irv Ogi. They first built an enclosing cage and reinforced the bottom of the structure. Using 100-ton hydraulic jacks and wires, they moved the tower’s legs up 11 inches on the northeast corner, seven inches on the southeast corner and four inches on the northwest corner. When they were done, the tower was within one inch of true plumb, an amazing feat.

“This was a first for the lineworkers, including the crew chiefs, manager and myself,“ Line Supervisor Tom Caddy said.

At the same time, workers led by Crew Chiefs Anthony Borgioli, James Alexander and Kath Johnsen got going on the installation of a 150-foot tall metal monopole in the middle of the Burlington Northern Santa Fé (BNSF) train yard. The pole raises the lines to allow BNSF to safely use a new crane to move cargo on and off trains under the power corridor.Site 3S connecting raised conductors 2014-07-24

The massive monopole was custom built for the job and installed in sections ranging from 30- to 40-feet long. Workers installed the pole and lifted and reconnected the transmission cables.

Concurrently, workers lead by Crew Chiefs Gary Legere and Ken Busby completed the replacement of an older wooden “H” frame structure (named for its shape) carrying transmission lines between the Creston-Nelson and Duwamish substations. The job was scheduled for last year, but issues related to the wetla nd terrain delayed it until now.

“All of this work happened in only four days, during the time-limited clearance on two of 230kV transmission lines,” said Mary Junttilla, project manager.

Between now and October, City Light workers and contractors will remove 10 H frames in the area and replace them with eight metal monopoles 120 to 153 tall, install new cables, and restore the landscape of the area, including enhancing existing wetlands. The upgrades will improve transmission system safety, increase reliability and flexibility and add capacity in the Duwamish industrial area.