Water diversion gates in the Delta near Walnut Grove became stuck open Tuesday, posing a potential threat to juvenile salmon.
The Delta cross channel gates, operated by the U.S. Bureau of Reclamation, divert Sacramento River water into the interior of the Sacramento-San Joaquin Delta, then to pumps near Tracy.
The gates are normally closed on weekdays so salmon are not diverted from their migratory path in the Sacramento River and open on weekends for boat traffic.
While officials were attempting to close the two gates on Tuesday, one gate could not be moved due to a mechanical problem. So reclamation workers left both gates open while they work on a fix.
Jim Milbury, spokesman for the National Marine Fisheries Service, said via email a "preliminary assessment" indicates a low risk of harm.
"Most juvenile salmon have already migrated past the gates," Milbury said.