e57,
Some of these underground contractors have gear where they can drill a bore sideways, underneath stuff like retaining walls.
My impression is that, in general, it's cheaper to use these direction drills than it is to tear up and replace concrete. I've seen them use these machines to drill under the sidewalk to install fiber, and, in another case, to drill under the street to replace a water-service lateral.
That might work for your situation. (I don't have pointers to any contractors. The machine I saw drilling to install the fiber was made by Ditch Witch, if that's of any help.)
[This message has been edited by SolarPowered (edited 07-15-2004).]
