Footer Position

Hello there, I am working on WP 3.5 and responsive theme latest version. I have a 3 column template as you can see in this picture and the designer asked to put the footer on the left sidebar but the footer is 400px width and the sidebar is only 220px. She basically wants to have the same look as the png.

My question is, how can I do so the footer moves up and down depending the side of the content?

Thanks a lot.
The HTML and CSS code can be seen here