California Highway Patrol press release: 

On 09/20/2019, in the early morning hours, a female was driving a 2010 Kenworth semi truck hauling lumber on a flat bed trailer traveling south on US 101 north of Woodruff Road.

For reasons still under investigation, the Kenworth veered off the west side of the road over an embankment.  The Kenworth overturned and came to rest on its roof along the east river bank.  The Kenworth was discovered at approximately 8:00 am by Cal-Trans.  The driver was pronounced deceased at the scene. 

The driver’s identity is being withheld pending next of kin notification.  Neither alcohol nor drugs appeared to be a factor in the collision.