Highway 99 will close in Manteca for five nights. When will interchange be ready?
Five straight nighttime closures await drivers on Highway 99 at Austin Road in south Manteca.
They are part of the $48.2 million upgrade to the interchange with Highway 120, a key commuter link to the Bay Area.
The northbound lanes on 99 will be closed between Sunday, Jan. 25, and Friday, Jan. 30, from 10 p.m. to 4 a.m. each time. The southbound side will shut down between Monday and Friday, 11 p.m. to 5 a.m.
The schedule avoids the peak commute hours. The detours will involve short stretches in that area, south of the Yosemite Avenue interchange.
The good news: The project remains on schedule for completion in summer. That update came from the San Joaquin Council of Governments, which oversees transportation funding in the county.
Construction launched in August 2024 by Teichert Inc. of Pleasanton. It involves the southwest quadrant of the interchange, including:
- A second lane on the ramp between eastbound 120 and southbound 99
- A fourth lane on southbound 99 to about Austin Road
- A new bridge for Austin across 99 and the Union Pacific Railroad tracks
- New links to Atherton Drive and Woodward Avenue in south Manteca.
SJCOG said about 180,000 vehicles go through the interchange on a typical day. Many are Stanislaus County residents headed for jobs in Silicon Valley and other parts of the Bay Area.
The upgrade is funded in part by San Joaquin County’s Measure K sales tax and fees on property developers. SJCOG also tapped state and federal transportation programs and federal payments to local governments amid COVID-19.
The agency still seeks about $90 million to improve other parts of the junction in two other phases by 2042. They would add lanes to both highways and to the ramps between them.
The public can get updates on the current project’s detours and other details at www.sjcog.org.
This story was originally published January 23, 2026 at 12:06 PM.
