Officials are warning commuters to leave early and plan an alternative route.
Even as he acknowledged the inconvenience the Brown Line reroutes are causing commuters, Chicago Mayor Rahm Emanuel encouraged CTA riders to ride the train.
"I'm going to continue to take the train, the CTA, like I do, twice a week," Emanuel said.
It will take nine days to complete the track replacement over the bridge.
In the meantime, there will be no elevated Brown Line service in the Loop. Over the weekend, the Brown Line will run from Kimball to Chicago Ave., where shuttle buses will take customers into the business district. On weekdays the Brown Line trains will run to the Merchandise Mart or along the Red Line's subway tracks. The Purple Line express will not run at all until the work is complete.
"It will be more crowded than usual. It will be slower than usual, but we have a good plan in place that will allow people to connect," CTA President Forrest Claypool said.
Claypool joined Emanuel and CDOT Commissioner Gabe Klein this morning to detail the construction project. The Wells Street Bridge has been in service since 1922 and the bridge was last rehabbed in the mid-1950's.
All three emphasized that despite the inconvenience to residents, by coordinating their resources and doing both the bridge reconstruction and the track replacement at the same time is saving both time and money.
"It is going to be an inconvenience. On the other hand, four of the nine days are on the weekend when there is less commuter business traffic," Emanuel said.
The dual project is a major task, in no small part because it's taking place over the Chicago River.
"It's making a truss connection with active trains on top of it. It's never been done before in the City of Chicago," CDOT Project Manager Johnny Morcos said.