Major Phase of Mercer Project’s Electrical Relocations Done Ahead of Schedule

Seattle City Light crews recently completed the removal of a major overhead power line serving key customers in South Lake Union, and the construction of new vaults and conduits to replace those lines underground. The work was done on budget and four weeks ahead of schedule.

The Mercer Mess just got a little cleaner, thanks to the hard work of Seattle City Light civil construction, underground and overhead line crews.

This past July, our crews completed the removal of a major overhead power line serving key customers in South Lake Union, and the construction of new vaults and conduits to replace those lines underground. The work was done on budget and four weeks ahead of schedule.

The work took place along six blocks of Mercer Street, as part of the Mercer Corridor Program. This major Seattle project aims to redirect and improve traffic flow along Mercer Street between Interstate 5 and Elliot Avenue West. The city is using the opportunity to replace older infrastructure, build new sidewalks and improve views, ahead of planned new development in the area.

The Mercer Corridor Project is broken into four phases. Seattle City Light is involved in three of them. The first two of those included the burying of overhead distribution lines, and the installation of conduit for the future relocation of a transmission line connecting Broad and University substations. About 75 percent of that transmission line conduit was installed in this phase of the work.

This fall, the new 115 kilovolt transmission cables will be installed in the conduits that were built this summer

This portion of the project had many challenges. The work required eight planned outages that impacted more than 100 residential and 30 commercial customers, including four different buildings in the new Amazon.com campus. The City Light project manager is Greg Stamatiou.

In several segments, civil construction crews had to dig trenches underneath the tracks for the South Lake Union Streetcar, while the line was active. Getting the work completed right the first time was critical.

The conversion of overhead to underground lines is jointly funded by City Light and the Seattle Department of Transportation.

City Light and Seattle Department of Transportation are now focusing on the next phase (Phase 4) of the Mercer East project that will continue the installation of underground distribution feeders on Valley Street and the completion of transmission work. Phase 4 is scheduled to be completed by April 2013.