Septic soil in Sweet Grass County, MT, by the numbers

Very limited

85% of Sweet Grass County, MT's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. A standard gravity system routinely fails on ground like this; the same share of the county falls in USDA's worst absorption-field bucket outright. Sweet Grass County covers 1,855.536 square miles and counts 3,757 residents.

This is a county figure, not a parcel figure

Two lots a mile apart in Sweet Grass County can carry different soil, even though they share one countywide rating. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Sweet Grass County.

System cost, conventional vs. engineered

Given Sweet Grass County's rating, plan for the engineered-system range rather than the conventional one. The engineered-system range, $10,000-$40,000 (mound or aerobic treatment), is the more realistic number to plan around, against $3,000-$8,000 for a conventional system on the rare lot that passes.

Sweet Grass County's rank among Montana counties

Nationally, Sweet Grass County, MT is the 1,695-most-constrained of 3,058 rated counties for septic soil. Within Montana alone it ranks 14 of 54.

Before you act on this

How this rating is built, and its real limits · Conventional vs. engineered septic systems