In Your Community » Pierce » Construction Projects »

PSE Transmission project iconPSE Transmission project icon

Puget Sound Energy transmission line project

Central Pierce-Alderton 115 kV transmission reliability improvement project

Fall 2014 project updates

  • Phase 1 of construction is now complete. Work began in May 2014 and we energized the new transmission line on Oct. 9, 2014. Thank you for your patience during construction!
  • We're currently in the engineering, permitting and easment acquisition phase of Phase 2 of the project and expect to begin construction of Phase 2 as early as 2015.

Download full-sized map

Project map

Project overview

PSE is working to improve electric service reliability for approximately 24,000 customers in the Bonney Lake, Orting and central Pierce County areas. Currently, the local electric system is prone to power outages due to limited capacity and redundancy. With 17 outages in the past five years, it is one of the top five least reliable electric systems in PSE’s service territory, and outages can affect large numbers of customers.

The existing 38-mile-long transmission line, which ties together three major substations in the area, does not currently have the flexibility to continue to reliably serve customers in the event of an outage on the line – resulting in customers being put at risk for power outages (see reliability graphic).

To strengthen the current system and improve electric service reliability for our customers, we plan to construct three new 115 kilovolt transmission lines from points along the existing transmission system to the Alderton substation (14450 Old Military Road, Puyallup). The lines will be constructed in two phases:

  • Phase 1: Constructed one 115 kV transmission line along four miles of an existing water main corridor. The line runs from an interconnection point on an existing 115 kV line approximately 1,000 feet west of our existing Rhodes Lake substation (19650 Rhodes Lake Road, Bonney Lake) to Alderton substation (see map).
  • Phase 2: Construct two 115 kV transmission lines along 3.2 miles of an existing regional utility corridor. The two parallel lines will run from an interconnection point on an existing 115 kV line at Myers Road East near Highway 410 to Alderton substation (see map).

By constructing the new lines, we are segmenting the existing system into three smaller, more reliable systems that can back each other up in the event of a planned or unplanned outage on one of the lines (see reliability graphic).This “back-up” adds redundancy to the overall transmission system, limits the number of affected customers during an outage, and eliminates electric capacity constraints on the existing system – ultimately keeping the lights on for our customers. We estimate that this project will allow us to reduce outage exposure to all 24,000 customers by at least 50 percent.

This project is related to our Pierce County 230 kV project , which involves the construction of approximately eight miles of new 230 kV transmission line from the White River substation in Bonney Lake to the Alderton substation in Puyallup. These projects work together to strengthen the overall electric grid and increase electric reliability for our customers in Sumner, Bonney Lake, Orting and central Pierce County.

What is a transmission line?

Transmission lines are key elements in the electrical distribution system. The lines safely transport high voltage electricity from power generation sources like dams and wind generating facilities to substations in local communities. Transmission normally takes place at voltages of 55 kV and higher.

What is a substation?

Substations are critical links in the electricity distribution system, containing utility circuit protection, voltage regulation, and equipment that steps down higher voltage to lower voltage. Before reaching homes and businesses, power is routed through our transmission system to a substation where it is changed to a lower voltage that can be utilized by customers.