Granite County's SSURGO septic rating
Very limited
Granite County, MT: USDA's soil survey calls 91.7% of the county "Very limited" for a septic leach field. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 91.7% of the county. The county spans 1,727.162 square miles, home to 3,602 people.
What this number does and doesn't tell you
USDA's survey covers the whole of Granite County, MT at once, not any single address. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Granite County: conventional vs. engineered cost
91.7% of Granite County carrying a "Very limited" reading changes the realistic budget here. Conventional systems run $3,000-$8,000 where they pass; where they don't, engineered alternatives (mound or aerobic treatment, whichever the health department requires) run $10,000-$40,000 - budget toward the higher figure until a perc test says otherwise.
How Granite County, MT compares
Among the 3,058 rated counties on this site, Granite County, MT ranks 1,087 most-constrained nationally, and 2 of 54 within Montana.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems