Frost line depth in Wapello County, IA
How deep the ground freezes in Wapello County, IA
33 in. Dig to 34 in, just below the frost. Nearest NOAA station: Ottumwa Industrial Ap, 5.6 mi.
Your building department sets the legal frost line depth (IRC Table R301.2(1)); footings must go below it (R403.1.4.1). Call them before you dig.