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.