So of all the places to hit caliche....
We hit it digging our fake stream bed out. Never hit an ounce of it digging holes for trees.
We need to dig six inches down to hollow out the fake drainage streambed and hit the caliche three inches down.
Right now we have water soaking into it to attempt loosening it up a bit. The tiller makes a decent dent in it, but only can get through about an inch at a time. I'm going to try the 35 lb digging bar next. If neither of those work I'm going to inquire with my one neighbor at the end of the culdesac and see if he has a pickaxe.
At least we think it's caliche, it's in a very strange spot to be caliche as it's on the man made slope on the yard. It could be hard packed soil from construction equipment but dang this stuff is like concrete so I really want to think it's caliche. It even has that off-white color of caliche...