Puget Sound Energy (PSE) has began preliminary construction work to replace 2.5 miles of two high-voltage electric transmission lines in Snohomish County’s Ebey Slough basin in Washington state. The $15 million project will replace decades old 115 kV and 230 kV transmission lines and structures, and help increase the safety and reliability of the regional high-voltage electric transmission system.

Currently, PSE’s existing power lines in the basin are supported by wooden H-frame poles, which are not designed for use in the standing tidal water that is now there. Over time, environmental conditions have deteriorated the frames and, in some cases, the anchors and guy wires supporting them have pulled out of the soft, saturated soils.

“Replacing the existing deteriorating wooden structures in Ebey Slough basin with steel poles that can withstand the changing environmental conditions of the basin is a necessary upgrade to the PSE infrastructure,” said Sue McLain, senior vice president of Operations at PSE. “Not only will replacing the unstable frames with sturdy poles and stringing new wire enhance the safety and reliability of our region’s transmission system, it will also protect the fragile surrounding wetland habitat from potential damage in the future.”

“We worked long and hard to keep everyone involved in the process to find the best solution to replace the lines and obtain all of the necessary permits,” McLain added. “We thank the community and permitting jurisdictions for their cooperation then and now as we work in a short six-month environmental window to complete the job before the next storm season.”

This month’s preliminary work has PSE placing erosion and sedimentation control silt fences and silt curtains in work areas to prevent erosion. The company will then install foundations at each end of the project at Fobes Road and near Home Acres Road, and install two conventional pier foundations near Home Acres Road. PSE will use Marsh buggies, lightweight amphibious tracked vehicles designed to have less impact on wetlands than conventional vehicles, to minimize impacts on the surrounding environment.

Beginning the week of June 2, PSE is scheduled to start constructing 11 micropile foundations (unique, deep foundations appropriate for wetland areas). PSE will then:

• Begin verification testing of micropiles, and
• Complete installing micropile foundations near the cross dike and continue working to the south throughout June, July and August.

Beginning in mid- to late-August, PSE is scheduled to:

• Begin work on the approved wetland migration site north of the remnant dike area along Fobes Road and re-route the mouth of Moser Creek. This work is designed to enhance fish habitat and salmon passage in the creek.

In September, PSE is scheduled to:

• Use a sky crane helicopter to install 15 steel poles on the conventional and micropile foundations.

From mid-September through early November, PSE is scheduled to:

• String wire on the newly installed steel poles, and
• Use two smaller helicopters to remove the existing 84 wooden poles and wires.

Construction is scheduled to be complete in November.