The Rainbow Bridge in Folsom, for many decades the main way over the American River into old town from Greenback Lane, will be closed this week.
Major repair work will be done during the closure from 6 a.m. Monday to 5 p.m. Friday.
Motorists are encouraged to take the Lake Natoma Crossing. Detours will be marked.
Nearly 100 years old, the concrete-arched Rainbow Bridge is showing its age. The $1.1 million project will eventually provide a smoother ride.
The project, which is set to be completed by October, will include repaving the bridge and repairing the approaches to the span.
The bridge normally carries 25,000 vehicles each day.