Cruise ships docking in San Francisco could connect to The City’s power grid through a massive electrical cable, allowing operators to switch off idling engines in the first week of October.

Testing is about to begin on the Port of San Francisco’s new shoreside power project.

The project will improve Bay Area air quality because ships will be powered with hydroelectric power generated in Yosemite National Park through a cable instead of running diesel engines while berthed.

Diesel engines create soot and other pollution.

If testing goes well, the cable could start to be used Oct. 6, according to Port official Peter Dailey.

The Port calculated that the shoreside power supply will prevent 140 pounds of diesel soot emissions and 1.3 tons of airborne nitrogen oxide emissions for every 9-hour call by the Dawn Princess.