On Friday, May 12, 2017 at 3:05:33 PM UTC-4, wrote:
On Fri, 12 May 2017 17:44:02 GMT, Michael
m wrote:

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 framed. It's probably 18 inches plus or minus 3. Maybe plus or minus 6 in spots. So moving laterally can sometimes help too.