I get back to Chicago a couple times a year. Last trip, I couldn’t help but notice the decaying concrete viaduct under the Loyola station. Given that nothing lasts forever, does the City have a timetable/plan in place for replacing the elevated structures? If so, how could the existing structures be demolished and new ones built, all the while keeping the trains running? What’s the remaining life expectancy for these structures? To someone faced with the responsibility of such a project, it has to be a source of recurring nightmares. To some labor union it must be a pleasant dream.
I’m not an engineer, but it should be a relatively simple matter to put up temporary supports around the old decaying support, demolish the old support, and build a new one to replace it.
I’m assuming that at some point the entire elevated structure, start to finish, will have to go, not just the street overpasses. Can’t imagine the complexity of the project, the logistics and the disruption to the neighborhoods.
Reconstruction of the Red and Purple Lines is currently in the planning stages; see:
http://m.transitchicago.com/news_initiatives/planning/redpurplevision.aspx
Decaying, yes, but they can probably last pretty long. Case in point…I was in Queens for a weekend last summer and took the 7 train…it’s elevated in Queens, subway in Manhattan. Anyhoo, going up the stairs on the elevated track there were literally missing STEPS that had fallen out, but the structure itself was still pretty sturdy…
(BTW - couldn’t help but notice that all the dates mentioned in that study – meetings, etc. – have come and gone. Anything come about as a result?)
They published a collection of comments received, which is available on the site somewhere. About a third (or so it seemed) complained about slow service due to the numerous stops. I presume they’re mulling this over. Which reminds me. In his recent column on “L” energy efficiency:
http://chicago.straightdope.com/sdc20100401.php
… the Master alluded to his master plan to improve north side service. He’s greatly disappointed no one has asked what his master plan is. Someone needs to do this. Dealing with Cecil is no walk in the park even when he’s cheerful, and when his mood darkens, life for his underlings becomes very grim indeed.
OK, I’ll bite… What is the master’s master plan to improve El service and efficiency?
Myself, I’d like to go back to George Kramble’s old A/B stops, even though it seems that the current run of Chicago breeding stock is too stupid to follow signs with letters. Some of them can barely deal with colors.
In answer to the thread’s original question, a number of the worst bridges have already been replaced, at least one nearly under service. This was done by prepping the site around the current bridge structure, then building a new steel structure parallel to the existing bridge and sliding it into place while nearly simultaneously sliding the old one out. Pretty cool display of advanced hydraulics watching that one. Hook up the tracks and wires and you have a working, new bridge. They even did it on a Sunday to minimize rail and traffic problems.
The CTA (sometimes called Chicago’s Tragic Attempt) management may not all be a world-class brain trust, but their are times when they aren’t completely stupid.
About damn time. Thank you. We’re on it.