Levy said Occupy Philadelphia did not delay the project, which had been working through government approvals.
The major initial work will take place underground, as the array of entrances, exits, stairways, and concourses is altered to make navigation simpler and safer.
Today, the dimly lit complex seems designed to maximize danger, Levy said.
"The maze that exists underground will be completely transformed," he said, with new entrances for the Broad Street and Market Street lines.
Access will be maintained for commuters during construction, with alternative entrances, stairs, and other routes staying open.
At Dilworth Plaza itself, expect to see only preliminary work, such as the removal of overgrown trees and some demolition, for several months. In early 2013, after the underground improvements are well under way, the public should start to see the new plaza taking shape.
When it reopens in spring 2014, the area will have undergone dramatic reimagining in four major ways.
Glass-enclosed entrances to the subways at the western edge will replace current multilevel cutouts with staircases, adding more than 20,000 square feet of usable street-level space.
A cafe at the northern end, with built-in handicap-accessible elevators to the subways, will be lighted at night, visible from the Convention Center, and will have views all the way to the Art Museum.
The cafe's footprint will be about only 1,100 square feet, or about 1 percent of the plaza, Levy said. All cafe revenue will go toward plaza maintenance.
