During construction using post-tension slab, a problem has required an extensive hole to be made in the slab.?

The hole in the slab of new house construction will be about 30 x 3 feet in order to correct a problem with the slope of the sanitary drain. This hole will extend about a foot or so into the subsoil in order to remove drain pipe and re-grade the slope, then re-install/connect the drain pipe, backfill and replace concrete. The method of making the hole will involve cutting the concrete and chiselling around the post-tensioning cables. Should there be concern that the tension of the 30 foot span could cause the existing concrete to fail? How reliable of a concrete repair can be made so as not to effect the integrity of the slab? What other questions should I be asking the builder? Thanks for your ideas.