I had to put in a radon mitigation system in the basement. This required i drill out a hole slightly bigger than 4 “. Under the slab there was a thin layer of plastic and maybe 1″ of what looked like Styrofoam. Beneath that there was a decent layer of gravel and then dirt/sand. I dug out a pit that is roughly 9″ below the slab (8 below foam) and has a radius anywhere from 6″ to 9”. My pipe will extend an inch below the foam. My question is this. I just put a 4″ wide hole in the vapor barrier. How do I seal that? The radon mitigation videos I’ve seen they typically use backer rod and then sealant but that is usually a quarter to a half inch from the top of the slab. What I do need to do 6 inches down where the slab ends and the vapor barrier and foam begins? I would think i need to try and restore the continuity of the vapor barrier right right?