cqaigy,
thanks for the concern with this. I considered this but I really didn't have a choice in this instance, and the line is out to my livestock and will not be drinking water for humans. Having said that the lines are not leaky and the soils involved did not have any unusual odors or discolorations. Also there will be approximatedly 5ft between the two. The water line will not have any joints nearby the crossing, and as far as a capilary action I can't see them letting people run potable water through this pipe if it wasn't rated to keep the inside material safe. In addition to that the primary ground material is hard clay which they use for retaining leachate in many instances, so it will form a natural barrier of sorts between the two.
One of my other thoughts on this is that this must happen in cities all the time with services crossing. When you need to get from point a to point b, there's really no way around it.