what do you mean “if i’m in Pa.” The number one rule in construction is to know what state you’re in. OK? Now I know I’m in Mo. Here,for concrete foundations and footings it is 37 in. But 2 yrs ago I fenced in several acres w/post in concrete. Towards the end I was runninshort on concrete,so some holes were drilled no more than 25 in.deep. those post have sinced been redrilled and dug to the recommended 37 in. They could be pushed over in the spring. A cold winter will pop them up like icecubes if they are shallow. So, once you decide which state you’re in call the state conservation or a county agent. then follow their advice!