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First off, I am not a structural engineer, but I do have an engineering background. Here is my scenario. I've built a workshop next to my house and I and plumbing a bathroom in it that I'm trying to tie into the existing sewer lines under my home. I've calculated the drop required and I'm within tolerances on that, so my only remaining questions has to do with the hole I'm going to have to cut in the foundation to allow for the exterior drain pipe to connect to the existing sewer line. The house foundation is a post tension slab. I'll be drilling the hole at 15 inches below grade and the diameter is 3.25 inches. Here are a few questions I have. Will a hole this size in the foundation require any additional reinforcement? If so, what kind would you recommend? Is it better to core drill this diameter hole, or could I potentially jackhammer it out? In order to connect the plumbing up, I'll also have to partially excavate underneath my foundation to access the plumbing. You can see where I start to get concerned because I'll be drilling into the foundation on a section of beam that is likely to not be supported by any earth underneath. Thanks for any insight you can provide!