Shoreline Substation Transformer Replacement Project

Seattle City Light recently completed a transformer replacement project at the Shoreline Substation.

Crews worked tirelessly to remove the old transformer, prepare the pad for the new transformer and then assembled it. The new transformer was installed, tested, commissioned and began serving the Shoreline community in late 2016.

Old equipment being removed from the Shoreline Substation.


New transformer installed and operating.

Now that the work is complete, the improvements will maintain reliable power for Shoreline customers for years to come. The substation is located at 2136 N. 163rd St.

To learn more about this project as well as other electrical infrastructure investment projects, please visit:

New Transformers Coming to Ross Powerhouse

For the first time in over 60 years, Seattle City Light is replacing several large transformers in the Ross Powerhouse at Diablo Lake. Colonial Creek Campground users may see some temporary impacts during the summers of 2016 and 2017.

The transformers in question have the important job of converting the electricity produced from the hydro-generators to a higher voltage before it travels over transmission lines. The existing transformers have been in continuous use since the beginning of Ross Powerhouse’s operations in the 1950s, and they have reached the end of their useful life.

Three transformers can be seen in this photo from 2004

Ross Powerhouse is located on the Skagit River at the upper end of Diablo Lake and it is not accessible by road; all equipment must be transported up Diablo Lake by barge. The transformers are very heavy–up to 80 tons–and the delivery trucks are too long to drive across Diablo Dam to reach City Light’s existing barge loading area. So, City Light built a temporary gravel road near Colonial Creek campground to reach the lake. 

Seattle City Light will deliver seven new transformers and remove six existing transformers over the next two years. Half of the work will be performed during the summer of 2016, with the other half to be completed in summer 2017.


  • The first batch of new transformers will barge to Ross Powerhouse in the second half of June. The process will take approximately ten days.
  • The first batch of old transformers will barge out of Ross Powerhouse in late July 2016 and the process will take about one week

Impacts to Parks users:

  • Most of the parking spaces in the lot immediately next to Highway 20 will be unavailable from approximately June 15 to June 25, 2016, and again in late July, 2016.
  • Signs restricting parking will be posted several days in advance.
  • If towing is necessary, cars will be relocated to the parking lot across Highway 20 near the boat launch.
  • There may be construction noise during the night as transformers arrive by truck and are stored near the access road. The Washington Department of Transportation restricts the hours that very heavy loads can operate on highways.
  • There will be construction noise during the day as transformers are loaded onto special moving vehicles and placed on the barge. Work may begin as early as 6 AM.  The hours of operation are restricted by water levels on the lake and weather conditions.
  • During the transformer deliveries, Diablo Lake will be at normal to high elevations.

If you have any questions, please contact Chris Woelfel, Seattle City Light Project Manager, at 206-684-3553 or

Seattle substation upgrades make West Coast grid more reliable

From the first hydroelectric facility on the Cedar River, to the massive concrete arc of Boundary Dam, City Light is founded on a tradition of big and bold engineering.

Residents of the Central District and Capitol Hill are currently getting a peek at that tradition, as workers and contractors work on massive upgrades of the East Pine substation. The work is designed to make that facility stronger during an earthquake and more reliable as it helps to transmit power from Canada to the West Coast of the United States.

The most visible part of that project happened last week. Between Aug. 1 and Aug. 8, contractors moved a 30-foot-long, 22-foot-tall, 480,000-pound transformer from its staging location near the Port of Seattle, all the way to the substation at 1501 22nd Ave.

The machine replaces an older, smaller transformer that has served its operational life. It was manufactured in Korea by the Hyosung Corporation. It arrived by ship at the Port of Tacoma and was barged to Seattle this summer.

Moving it from the port to its final location has been a logistical odyssey. It is so heavy and unwieldy that it had to be transported in two trips, from the port to a staging area in a tandem trailer, and from there to the station in a relatively smaller rig.

Over the weekend, the transformer was slipped into position with the help of pneumatic pistons and metal rails. It will be fully assembled and filled with oil so it can go into service in November.

The rigs and moving equipment may be the most visible part of the project, but what’s under and around the new transformer is perhaps the most important.

The new transformer will sit on a base of pendulum bearings. These bearings serve as shock absorbers, allowing the transformer to glide back and forth during an earthquake. By transferring movement for force, the bearings help to keep the transformer upright and connected. It will be the third transformer in the entire United States – and the second at City Light – to use this new technology.

In addition to the gliding bases, the transformer and the equipment around it will be supported by new metal structures designed and custom built by City Light engineers and steel workers to be stronger and more resilient during an earthquake.

The structures include supports and tall pedestals shaped like mini Eiffel Towers that will hold solid conductors. They resonate at a different range of frequencies than the motion of an earthquake, so that they won’t rattle apart during ground shaking.

“To the equipment, it will feel like everything is fixed directly to the ground,” said Robert Cochran, the civil engineer who designed the new structures.

All these upgrades will make the substation more reliable. This is a critical issue for our city and the entire West Coast. The East Pine Substation supplies power to all the major hospitals on First Hill and to parts of downtown. It is also part of the Bulk Electric System that moves power from Canada all the way down to California.

71 ton transformer delivered to Seattle City Light

Large tractor-trailer delivers 71 ton transformer

Goal is to move transformer to this concrete pad


Omega Morgan crew assembles rail system to move the transformer from the trailer to the pad.

Moving a 71-ton transformer from the Port of Seattle to

Shoreline required some specialized skills and equipment.

Seattle City Light ordered the new substation transformer, which is used to step down transmission voltages of 115 kilovolts to the distribution voltages of 26 kilovolts, to enhance reliability by replacing an older model that has reached the end of its useful life. The $1.5 million transformer was specially built for City Light by Hyundai Industries.

Omega Morgan-Seattle used a special articulated tractor trailer rig to move the transformer into the Shoreline Substation on Monday, June 30, 2014. There, a special rail system was assembled to move the 143 ,000-pound transformer from the trailer to a concrete pad. The pad was constructed with special earthquake dampers to minimize any damage, should an earthquake occur.

The new transformer will be completed with equipment required to tie it in to the transmission/distribution system by mid-September.