CAISO has selected Viridon as the project owner to develop transmission infrastructure in Humboldt County, Calif., to support future offshore wind power in the region.
Over the next decade, Viridon will develop about 400 miles of new transmission lines for two primary projects: Collinsville and Fern Road. The projects could cost an estimated $4.1 billion.
The Collinsville project includes a new 260-mile high-voltage direct current line that initially will operate at 500 kV alternating current, along with a new substation and transformer in Humboldt. The estimated project cost is $1.9 billion to $2.7 billion, and the project is expected to be online by June 2034, CAISO wrote in its 2023-2024 transmission plan.
The Fern Road project includes a new 140-mile 500-kV line from the New Humboldt substation to the Fern Road substation for an estimated $0.98 billion to $1.4 billion. Since the line’s voltage level is more than 200 kV, Viridon will be responsible for submitting progress reports to WECC, CAISO wrote in its plan. This line also is expected to open by June 2034. Viridon will be required to submit nonconfidential cost-tracking information for CAISO’s approval during the project.
However, there is inherent uncertainty in the future of floating offshore wind off the California coast, CAISO wrote. CAISO therefore will “balance the need to engage promptly on long lead time transmission with the need to remain in step with the numerous other parallel development paths needed to enable offshore wind to develop,” the ISO wrote.
California’s North Coast has “world class” offshore wind power potential, but the location of that power is a long distance from the load centers in the state, the California Energy Commission (CEC) wrote in a 2024 transmission corridor evaluation report. The transmission system will require significant infrastructure investment to move North Coast OSW power to major urban load centers, and “large amounts of transmission upgrades will be needed in the coming decades,” the report says.
The CEC’s report includes possible transmission line paths for both the Collinsville and Fern Road projects. For the Collinsville project, the most favorable route is a southern path, which has two potential barriers: residential development in the City of Eureka and critical habitat for threatened or endangered species.
For the Collinsville project, a coastal overhead path had fewer potential difficulties than a coastal underground path. The overhead path’s primary potential barriers include traversing valuable property in wine country, while the underground path’s primary potential barriers include active fault lines and possible landslides.
CAISO’s 20-Year Transmission Outlook, published in 2022, shows 10 GW of offshore wind development in the state: 4 to 7 GW in the North Coast region and 3 to 6 GW in the Central Coast region.
Viridon currently is developing two transmission projects in the NYISO region, one planned to be online in 2026 and the other in 2033.
