Originally Posted by
JohnDThompson
This. ^
The only plausible way to safely repair the frame would be to cut out the whole tube, weld in a replacement, and re-heat-treat the entire frame. The cost of doing this would likely approach that of a brand-new replacement bike.
^fixed.
New frames of similar quality are dirt cheap, and if you want to stay with Cannondale they have a crash-replacement program. Unless you are an experienced aluminum tig welder and posses equipment ready to do the heat treatment then a proper repair will almost definitely be more expensive than buying a replacement frame.