(Adds details, background on project)
WASHINGTON, May 22 (Reuters) - The U.S. Transportation Department said on Monday it will release grant funds for a project to electrify a northern California commuter rail system.
In February, the Transportation Department withheld a $647 million grant for the San Carlos Peninsula Corridor Electrification, or Caltrain, project, from San Francisco to San Jose to allow a review by Transportation Secretary Elaine Chao.
California Governor Jerry Brown said in February the project would allow the state to "run more trains, cut commute times, save fuels costs, improve air quality, reduce noise and ease congestion."
The agreement releases $100 million that Congress approved to electrify the 51-mile line, and Senator Kamala Harris of California said it commits the government "to prioritize an additional $408 million" for the project in future years.
Caltrain has about 65,000 daily riders and transports many workers throughout Silicon Valley. The Transportation Department did not immediately confirm how much in funds it is approving. (Reporting by David Shepardson; Editing by Sandra Maler and Dan Grebler)