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Puget Sound Energy transmission line and substation projects

Pierce County 230 kV transmission line and Alderton substation expansion


Summer 2015 project updates

  • On Dec. 4, 2014 we hosted an open house at the Sumner Public Library. The meeting was also made available online. Thank you for your feedback and participation!
  • PSE has identified properties on which easements are needed and been in contact with private landowners to discuss negotiations.
  • We expect to begin construction on the 230 kV transmission line and Alderton 230 kV substation expansion as early as spring 2016 and complete the work in late 2016.
  • Click here to view a close-up map of the preferred route for the transmission line.
  • We'll continue to keep the community advisory committee informed as the project progresses and respond to questions and concerns from individual property owners.
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Project Overview

Due to current and projected customer energy use in Pierce County, the existing regional electric grid is approaching capacity, making it difficult to move power throughout the county. To help solve this problem, Puget Sound Energy plans to construct approximately eight miles of new 230 kilovolt transmission line from the White River transmission substation, located at 2120 Lakeland Hills Way in Bonney Lake, to the Alderton switching station, located at 14450 Old Military Road in Puyallup. Adding the new 230 kV line will allow PSE to respond to the county’s current and future need for power while increasing overall reliability to our customers served by 17 local distribution substations in the central Pierce County area.

We also plan to upgrade our existing Alderton switching station, which is currently designed to accommodate 115 kV transmission lines, enabling it to accommodate the increased capacity of the new 230 kV line. The upgrade will require us to expand the station’s footprint within our existing property.

This project is related to our Central Pierce-Alderton 115 kV transmission reliability project , which involves the construction of three new 115 kV transmission lines in the Bonney Lake, Orting, and central Pierce County areas. 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 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.

What is a switching station?

A switching station is a transmission substation where the utility can switch or reroute power flow from one line or path to another to allow the power to be isolated to clear a fault (e.g., a fallen tree in the wires) or to take the power line out of service for maintenance. It also may act as a point of interconnection between two different transmission operators (e.g., Bonneville Power Administration and PSE). Unlike a substation with a transformer serving neighborhood circuitry, switching stations do not step power up or down; they integrate power from one or more transmission sources on the regional and local grid to serve neighborhood substations.

Committed to keeping you informed

PSE will continue to provide updates to the community. We will notify residents and businesses near the project area when construction will occur. We aim to complete the work with as little disruption as possible.