Frost line depth in Chester County, TN
How deep the ground freezes in Chester County, TN
15 in. Dig to 15 in, just below the frost. Nearest NOAA station: Henderson 4 W, 6.6 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.