Ever taken a close look at the eastern side of the viaduct at the Argyle Red Line station? The concrete structure was so eroded that the CTA had affixed multiple sheets of steel to keep chunks of concrete and stone ballast from falling to the street.
That's history, as of Sunday afternoon, when crews were finishing up installation of pre-cast concrete parapet sections. It's the same repair method already seen at Thorndale and Morse. The eroded top section of the viaduct parapet is sawed off and then the pre-cast concrete is lifted to track level and attached with reinforcing bar.
The work isn't finished at any of the stations, yet, but I learned from one of the workers on site that the next step is to remove any remaining loose concrete and then refinish the old surfaces with a process called shot-crete, which involves shooting concrete onto the wall under pressure and then shaping and finishing it, just like any other concrete job.
The columns underneath the viaduct will get the same treatment. (Badly needed, in almost every case.) With fresh tuckpointing, new lighting and accessible sidewalks at each station entrance, it should make for quite an improvement.