Steve, you obviously know what compaction can cost in yields. And pipeline construction technique is very bad in that regard--and it is a deep compaction which is next to impossible to cure--even with tillage radishes.

Their standard practice is to strip off a couple feet of topsoil 50-100 ft. wide. Then they compact that lower layer with heavy equipment during construction. Then they cover it back up. Looks fine on the surface, but the deep damage will be very long lasting. 

If it was my ground I would want a clause in there to specify exactly how they will rid that lower layer of compaction.

As other posters have mentioned, tile is a second major concern. If you even remotely think you might tile in the future, get the system designed now so you know how deep to specify the pipeline must be to clear it by at least a foot. Don't forget to negotiate reimbursement for the extra cost of tiling around the pipeline. They are VERY picky (as they should be) after the pipeline is in service. You can cross it with mains (by hand digging under their direct supervision). But it is not practical to cross it with laterals so often it requires the extra expense of a separate submain.