Frost line depth in Alamosa County, CO
How deep the ground freezes in Alamosa County, CO
46 in. Dig to 46 in, just below the frost. Nearest NOAA station: Alamosa 1e, 7.8 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.