BPA Transmission to rebuild 75-year-old transmission line in Puget Sound area

With over 15,000 miles of high-voltage transmission line stretching across its service territory, the Bonneville Power Administration carries out a large asset management program that focuses on needed replacements to sustain the reliability and resilience of the federal grid. That's why BPA is planning to rebuild the 60-mile-long Shelton-Fairmount No. 1 115-kilovolt wood pole transmission line along the Hood Canal in Northwest Washington. Construction is currently expected to begin in spring 2025, with energization slated for late 2028.

Built in 1949, the line is showing signs of deterioration and nearing the end of its service life. As the sole point of service for multiple customers in the area, preserving line's integrity and reliability is critical.

The Shelton-Fairmount No. 1 line stretches from BPA's Shelton Substation in Mason County to its Fairmount Substation in Jefferson County. The line rebuild project includes replacing nearly 440 wood pole structures, 60 miles of conductor and accompanying hardware. New structures will be included at additional locations along the line where needed, and access routes to the line will be upgraded or repaired to ensure safety and accessibility when the line requires maintenance.

The project also includes 107 miles of fiber optic cable replacement from the Olympia Substation in Thurston County, Washington, to Shelton Substation, as well as from Fairmount Substation to BPA's Port Angeles Substation in Clallam County, Washington. BPA's fiber network is critical to the agency's communications system used to control, monitor and protect the grid. 

Project Manager Rusty Ludt says the line rebuild has faced many obstacles, such as design contract changes and ensuring compliance with the National Environmental Policy Act (NEPA).

“After the design for the project was completed, a new challenge occurred with a change in the manufacture of fiber optic cable," said Ludt. “In spring 2023, the project engineer advised that the new fiber optic cable would be about 9% lighter, which created the need for an analysis of cable-to-cable clearances, as the lighter fiber will sag differently and respond to wind differently."

As a result of this change, Ludt and the rebuild team must undergo a formal process to request an updated design package from a partner contract design firm. Ludt says that this request is one of the biggest hurdles currently facing the project, as it extends the project timeline leading up to construction in 2025.

Verifying that the rebuild complies with NEPA standards adds another process that may impact the project's timeline. As of June of 2024, BPA released its final Environmental Assessment, including a Finding of No Significant Impact (FONSI) and Mitigation Action Plan (MAP) to mitigate potential environmental impacts of the project.

However, according to the project's Environmental Protection Specialist Mike O'Connell, the project poses some impacts to wetlands that BPA is trying to offset. Under the Clean Water Act, BPA is required to estimate and mitigate projects' environmental impacts and effects to wetlands. For this project, environmental mitigation means undertaking compensatory offsite mitigation projects, which are currently in development.

“The Hood Canal Coordinating Council, based in Poulsbo, Washington, administers an In-Lieu-Fee Area for wetland impact mitigation in the Washington Water Resource Inventory Areas in which impacts occur," O'Connell said. BPA assessed mitigation needs for this project and will purchase the credit equivalents to offset impacts.

The total impact acreage of the project has been converted to credit equivalents that BPA must purchase. These credit purchases will ensure that BPA's impacts are offset by Hood Canal Coordinating Council's offsite mitigation projects.

With numerous processes needing completion before construction begins on the Shelton-Fairmount No. 1 Transmission Line Rebuild project, Ludt remains optimistic the project is on track to start construction in spring 2025.

“We're almost there," said Ludt, adding that the team is eager to break ground and ultimately deliver a safer, stronger and more resilient for customers.