Update: The tunnel was completely filled in by the winter of 2013. See construction photos from July of 2010.
The Post-Dispatch reports that the Tucker Tunnel, collapsing now for two years, will be filled with Styrofoam blocks. I am perplexed by the statement that the tunnel has absolutely no possible future usage; I still think it could have been used for the proposed Metrolink North-South Line one day as it traveled through downtown. Check out my photos here; much of what is shown will be filled in soon with Styrofoam and dirt.
The styrofoam blocks have begun to be used in railroad track beds and elsewhere and have performed well. I think it’s a good fit for this project. But expect to hear shouts the first time a project with these blocks fails. Of course many dirt fill project have issues – which is specifically why these blocks are a good alternative . . .