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Puget Sound Energy substation and transmission line project

Yelm area reliability projects


Summer 2015 project updates

  • We are planning to begin design and permitting for the Blumaer-Yelm transmission line rebuild in 2015.
  • Construction is expected to begin in 2016 and should be completed in 2017.

Project overview

PSE is working to upgrade the electric system in Yelm and Thurston County in order to increase our customers' electric reliability and meet growing demand for power in the area. Currently, the region is only served by two north-south transmission lines, which are prone to tree-related outages and limit the power flow in Thurston County.

From 2010 through 2018, we will be completing four projects, collectively called the Yelm area reliability projects.

These projects entail adding three new transmission lines, rebuilding an existing transmission line, and upgrading two substations, allowing us to move power throughout the county more efficiently and provide additional sources of power in the event of scheduled or unscheduled outages.

Yelm transmission line and substation - Complete

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Yelm project map

The Yelm transmission line and substation project entailed constructing four miles of new 115 kilovolt (kV) transmission line from the Yelm substation to a point along the Blumaer-Yelm 115 kV transmission line. The new transmission line is located primarily in and along public road rights of way. In addition to the new transmission line, we upgraded the Yelm substation and provided space to add a second electric transformer, which will allow PSE to double the capacity in the future without changing the substation footprint.

Blumaer-Yelm transmission line rebuild

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Blumaer-Yelm project map

The existing 17-mile transmission line between the Blumaer substation and the Yelm substation is approaching its capacity, straining the local electric system and making it difficult to reliably meet the energy needs of our customers in Yelm, Rainier, and Tenino. The line was originally installed in the 1960s and the poles and wire are aging and need to be replaced.

We are planning to rebuild the existing line with new wood poles and higher-capacity wire, which will alleviate the strain on the system and improve electric reliability for our customers. Construction is expected to take place in two phases:
  • Phase 1: PSE will rebuild the line between Tenino and Rainier.
  • Phase 2: PSE will rebuild the line between Rainier and Yelm.

Work is anticipated to be completed by 2017.

Longmire transmission line

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Longmire project map

The Longmire transmission line project entails constructing three to four miles of 115 kV transmission line from the Longmire substation to a point along the Blumaer-Yelm 115 kV line along 123rd Ave SE. We plan to replace the distribution poles along the route with taller poles to accommodate both the existing distribution lines and the new transmission line. As part of this project, we will also need to upgrade the Longmire substation in order to accommodate the new line.

Currently, the Longmire substation is served radially, which means it is served only by one transmission line. If the line serving the substation goes out, the substation and the customers served by it lose power. This new transmission line will increase service reliability for customers by creating a "loop", meaning that each substation will be fed by two transmission lines. If one line goes out, the other line will still feed the substation to keep power on for our customers in the area. Construction of the new line is expected to begin in 2020. 

St. Clair-Yelm transmission line

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St. Clair-Yelm project map

The St. Clair-Yelm transmission line project entails constructing 15-17 miles of new 115 kV transmission line from the St. Clair switching station to a point along the Blumaer-Yelm 115 kV line near the intersection of SR 507 and 123rd Ave SE. Specific route alternatives are currently being evaluated, and we will construct the new line in existing utility corridors whenever possible. The new line is expected to be completed by 2020.


What is a transmission line?

Transmission lines are key elements in the electrical distribution system. These 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.