Closures will be in effect on the southbound 99 on-ramp, at Olive Avenue.
The Belmont off-ramp on the southbound lanes of Highway 99 is also being closed off.
Detour signs are in place to alert drivers of these changes.
Crews will be constructing a lane between the two ramps and installing a new light system as part of this project, which is expected to last about a month.
Caltrans officials say the closures should be lifted on March 13 but could take longer, depending on how the weather cooperates.