Mount Si, photo by Seattle City Light employee, Todd Andrews
Seattle City Light LARRY WEIS, General Manager and CEO
Denny Substation Project
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Denny Substation Project Update

Project Status

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 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.

Denny Substation Construction

Crews have completed onsite soil characterization and installation of noise monitoring equipment, and will soon complete drilling foundation support columns. Utility work will continue on John Street and Minor Avenue N, as well as onsite. There will be periodic lane closures on Denny Way during the day and night.

In late-August, crews will complete excavation, hauling, and utility work onsite. They will begin pouring substation foundation support and installing duct bank and vaults. Please be aware of increased truck traffic in the neighborhood.

Early Notice: There will be extensive work on Denny Way in August, September, and October. This work could require a full closure of eastbound traffic at night, single lane closures during the day and a full closure of westbound traffic round the clock for up to a month. More information about these closures will be provided once the work dates are scheduled.

Typical work hours are 7 a.m. to 7 p.m., Monday through Friday, but there will be some night work and occasional work on Saturdays between 9 a.m. and 5 p.m.

Note: This schedule is subject to change due to weather or other circumstances.

Denny Network Construction

We have completed the bulk of the preconstruction activities (potholing to confirm utility locations, soil characterization, and installation of noise monitoring equipment) south of Denny Way and have now moved this work to the South Lake Union neighborhood. This work is being done in preparation for duct bank and vault installations.

As of August 1, eight electrical vaults and 1,400 feet of duct bank have been installed. See the below map showing where these installations have occurred.

Completed vault and duct banks installation

Network Construction Traffic Restrictions

From now through September 2016, drivers should expect congestion on Stewart Street between Yale and Westlake avenues and on Virginia Street between Minor and 7th avenues as the project continues with the installation of vaults and duct banks. To stay informed about traffic conditions, subscribe to SDOT's email alerts by following this link:

Stewart Street Roadway Restoration

In August, construction crews will begin roadway restoration of Stewart Street between Minor Avenue and 6th Avenue. Restoration activities will require peak time and non-peak time lane configurations. During the peak hour commute, 5 a.m. and 10 a.m., Monday through Friday, one lane will be closed. During non-peak times, 10 a.m. to 5 a.m., Monday through Friday, two lanes will be closed. On weekends, two lanes will remain if work is being done, otherwise three lanes will be open to traffic. Roadway restoration work on Stewart Street is expected to continue through November.

Peak hour traffic configuration (5 a.m. to 10 a.m.)

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

Bi-Monthly Online Construction Meetings

The project team remains committed to providing the public with regular and reliable information about construction. Together with the contractor, the team is hosting bi-monthly online construction updates. The previous updates covered details on current and upcoming work, lessons on vault and duct bank installation, and how the crews are staying safe on the job. Listen to the most recent recording! Please note that you may be prompted to register, but only your first name is required (your email address is not required).

Updated: August 2016

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    P.O. Box 34023
    Seattle, WA 98124-4023

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