The CTA moved one step closer in its plan to replace three aging viaducts at Greenleaf, Dempster and Grove Streets in Evanston.

The agency selected transportation contractor Kiewit Infrastructure for the $10.3 million contract. The CTA's board approved the choice Friday.

No timeline has been set up for the project, which would include replacing the concrete viaducts with steel structures. New landscaping and lighting would be placed under the bridges.

Purple Line service will be affected sometime during the project but there are no specifics yet, the CTA said. The Purple Line was shut down for a few days when the viaduct on Main Street in Evanston was replaced in 2005. The CTA shuttled Purple Line riders.

Project funding is through an Illinois Department of Transportation grant.

Evanston aldermen advocated for viaduct replacement at a CTA board meeting in November. The aldermen said the look of the viaducts hurts nearby businesses because potential customers don't want to walk under the bridges.

Also Friday, the CTA approved two concession leases. Dunkin' Donuts will open at the Central Purple Line stop and at the Ashland Orange Line stop. The 10-year lease agreement is expected to generate a total $288,165.