Denny Substation Program Update
Seattle City Light is constructing a new electrical substation (Denny Substation) and an underground distribution network (Denny Network) to accomplish a major electrical system upgrade for the city of Seattle.
Construction of the substation began in May 2016 and is expected to be complete in mid-2018. Construction of the network, which is being installed underground in the South Lake Union and Denny Triangle neighborhoods, began in February 2016. This work is also anticipated to be complete in mid-2018. Learn more about the sequence of work, the construction schedule, and what to expect on our interactive construction map
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Denny Substation Construction
In mid-November, crews completed five weeks of construction along Denny Way to install the underground distribution lines that will deliver electricity to customers once substation construction is complete. Also in November, on the substation site at Denny Way near Stewart Street, crews began installing the structural steel “cranes” that will help support the outer wall of the substation. They will continue to install other structural steel elements throughout December and into the new year. Utility work will continue on John Street, Minor Avenue N and the substation site. Other activities that will continue through early 2017 include hauling, pouring the foundation for the substation and installing duct bank and vaults. Please be aware of increased truck traffic in the neighborhood
Note: This schedule is subject to change due to weather or other circumstances.
Structural steel “cranes” being installed to support the outer wall of the substation.
What to Expect During Substation Construction
- Monday to Friday work hours: 7 a.m. to 7 p.m.
- Saturday work hours: 9 a.m. to 5 p.m.
- Sunday work hours: 11 p.m. to 6 a.m.
- Occasional night and early morning work hours: 9 p.m. to 5 a.m.
- Lane and sidewalk closures around the construction site
- Sidewalk and crosswalk closures
- Noise from construction equipment
- Detour signage and construction flaggers
- Increased truck traffic during excavation
- Access to driveways, businesses and residences will be maintained
- Advance notice of construction activities
Denny Network Construction
Network construction consists of installing underground electrical duct bank and vaults. We have completed the bulk of the preconstruction activities (potholing to confirm utility locations, soil characterization, and ins¬¬talling vibration monitoring equipment) south of Denny Way and are now moving this work to the South Lake Union neighborhood.
As of mid-November, nine electrical vaults and 2,100 feet of duct bank have been installed. The map below shows where these installations have occurred.
Completed vault and duct banks installation
Network Construction Traffic Restrictions
As Denny Network construction proceeds through the Denny Triangle and South Lake Union neighborhoods, expect traffic congestion and detours due to lane restrictions and closures. To stay informed about traffic conditions, subscribe to SDOT's email alerts
for the greater downtown area.
What to Expect During Construction
- Lane restrictions and some traffic and pedestrian detours
- Typical weekday work hours will be from 6 a.m. to 7 p.m.
- Some weekend, night and early morning work
- Nighttime work between the hours of 7 p.m. and 6 a.m.
- Parking and loading restrictions near work zones
- Typical construction impacts such as dust, noise and truck activity
Online Construction Meetings
The project team is committed to providing the public with regular and reliable information about construction. In addition to emailing Weekly Program Updates to subscribers, we host online construction updates. These live reports cover current and upcoming work, include information about various construction processes, and provide opportunities to ask questions. We held several of these online updates in 2016 and anticipate holding them in 2017 as needed. You can watch the most recent recording online!