This has been going on for aboutxa month, now.

There is already a fence to prevent them from camping under the overpass, it needs to be fixed and they need to be ejected. Don’t hem & haw about whose responsibility it is, send an officer over there and boot them out!

Code Enforcement Division assigned this issue to Christina E., Community Services Section (CSS)

Thank you for reporting, this issue has been forwarded to Caltrans to address. In the future, please contact them directly with these types of issues (on state-owned property) by visiting the “Contact Us” section of their website at http://www.dot.ca.gov/contactus.html. SeeClickFix is one of the many tools available to the citizens of Vallejo to report non-emergency issues. We “close” an issue in SeeClickFix once we've acknowledged the complaint or have forwarded it to the appropriate agency. If there is anything else we can assist you with, please let us know. Thank you for using SeeClickFix!

Another thought, install lighting under the overpass right where they have been camping.
The lights will illuminate the area therefore deterring them from camping there.

Maybe fill in the space with cement?

Issue 4731894 has been marked as a duplicate of this issue.

removed

Thanks for fixing this request!