Undergrounding on Geary

There have been various ideas and proposals for Geary Street.  Including bus rapid transit and undergrounding.  Obviously, putting in a subway under Geary would be ridiculously expensive -- probably along the lines of the size of the Big Dig in Boston, but maybe it wouldn't be such a bad idea if it could be paid for.  Remember -- everyone thought the idea of getting rid of the freeway along the Embarcadero was impossible until mother nature took care of that one.