In a stone and clay crawl space, digging down I hit concrete along the wall? How far from wall should I go through it so as not to risk the foundation footing? I'll have to rent some kind of jackhammer to get through it.
Try another hole a foot or so away from the wall. The footer should be ~18" wide. You should be able to miss it if you get a foot or two away from the wall.
Also, this is not high precision NASA work. That footer isn't 18" plus or minus .001. It can vary back and forth as forms sag or are sloppily frame d. It's probably 18 inches plus or minus 3. Maybe plus or minus 6 in spot s. So moving laterally can sometimes help too.
Jackhammer seems to be a brute force method. Is there no other way, like a vent hole? How about a concrete drill? Directional drilling under the footing?
If a contractor said he was gonna use a jackhammer to poke a 1" hole thru my foundation, I'd go rent a different contractor.
A related question is how much good a sump pump hole will do without being connected to a drainage system that is installed along the perimeter of the footings, which is what is typically done.
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