I wouldn't plant one over a sewer pipe that is shallow and not completely sealed, but in general palm roots are more fibrous and concentrated and do not extend out far or to great depth. As a Butia palm trunk does eventually get fairly big, it could be a problem with concrete pavings if not given sufficient space of the roots, I would suggest that you should allow at least a meter square of open ground for planting, more is better.

Thanks a lot. The Butia is about 7 feet away from an underground water tank. I believe it should be ok, then.