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Puget Sound Energy substation and transmission line project

Lake Holm substation and Berrydale-Lake Holm transmission line​

Fall 2014 project updates

  • Construction of the substation and transmission line is planned for 2018. We will continue to engage and inform customers as engineering, critical area studies and permit efforts move forward.
  • Based on feedback received at the June 2012 public meeting​, PSE has selected its preliminary preferred route corridor for the new transmission line along 156th Ave SE; Kent Kangley Rd; and Kent-Black Diamond Rd. The new line will be co-located on the same poles as the existing distribution line. Many of the existing wood poles will be replaced with taller wood poles that can accommodate both the existing distribution line and the new transmission line.
  • We have purchased a site for the new substation.

Project overview

As part of Puget Sound Energy’s commitment to providing the communities of Covington, Black Diamond and Kent with dependable service, we are planning a series of electric system upgrades to improve reliability in the area. These will be multi-year projects, and will include the construction of a new substation in Lake Holm, a new 115 kilovolt (kV) transmission line and associated distribution lines. We will also upgrade four existing substations in the area to accommodate the new transmission line.

The multi-year construction effort includes the following projects and expected timelines:

2012-2016 efforts

  • Inform the public of the planned projects, gather community feedback and answer questions.
  • Finalize the route for the transmission line.
  • Begin work to engineer and permit the projects.

Lake Holm substation

PSE will construct a new distribution substation to increase system capacity and ensure that we can continue to meet the area’s increased energy needs now and well into the future.

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Berrydale-Lake Holm 115 kV transmission line
PSE will construct approximately six miles of new 115 kV transmission line between the pre-existing Berrydale substation and the new Lake Holm substation. This new line will provide a source of power for the new Lake Holm substation, and will be the first portion of a new transmission line intended to increase overall electric reliability for customers in the area. Additionally, the existing Berrydale substation will be upgraded to accommodate the new Berrydale-Lake Holm transmission line.

PSE has identified our preliminary preferred route for the new transmission line along 156th Ave SE, Kent Kangley Rd and Kent-Black Diamond Rd. To minimize the impact to private property and residents as much as possible, we plan to “overbuild” the existing overhead distribution lines along the roadway. This means that the new transmission line would be co-located on the same poles as the existing distribution line. Many of the existing wood poles would be replaced with taller wood poles that can accommodate both the existing distribution line and the new transmission line.

Distribution system improvements

PSE will also construct new distribution lines and reconfigure existing distribution circuits in the Lake Holm area to decrease the likelihood of power outages for customers. Currently, three distribution lines bring power long distances to the Lake Holm area. If an outage occurs on one of the existing lines, there is not enough redundancy or capacity in the system to continue to serve customers. These distribution lines are notorious for lengthy tree-related power outages. PSE will increase the system’s flexibility by shortening the length of the existing distribution lines and adding more lines, allowing us to move power around more easily and reduce the possibility of overloading lines. The end result will be a decrease in the number and length of power outages our customers experience.

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.