Septic soil in Flathead County, MT, by the numbers

Very limited

In Flathead County, MT, 78.4% of the surveyed land carries a "Very limited" rating for a standard septic drain field. Practically, that rules out a simple gravity system for most of the county - 78.4% of it sits in USDA's most-constrained bucket. Flathead County covers 5,087.304 square miles and counts 114,527 residents.

This is a county figure, not a parcel figure

Flathead County's rating is an average across the whole county, not a promise about any one lot inside it. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Flathead County.

System cost, conventional vs. engineered

Given Flathead 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.

Flathead County's rank among Montana counties

Nationally, Flathead County, MT is the 2,119-most-constrained of 3,058 rated counties for septic soil. Within Montana alone it ranks 32 of 54.

Related guides

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