The undersea power line would run south from San Luis Obispo County, hugging the California coast for 200 miles before making landfall in or near Los Angeles. It would be able to carry electricity from a fleet of offshore wind turbines, providing Southern California with clean power after sundown and helping to replace fossil-fueled generators.

Fewer planet-warming emissions, less risk of blackouts and no chance of igniting the wildfires sometimes sparked by traditional power lines: Those are the arguments for the $1.9-billion Pacific Transmission Expansion.