Frost line depth in San Juan County, NM
How deep the ground freezes in San Juan County, NM
18 in. Dig to 18 in, just below the frost. Nearest NOAA station: Farmington Ag Sci Cnt, 12.3 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.