What Lake County, MT's soil rates for a septic system
Very limited
Soil across 71.6% of Lake County, MT rates "Very limited" in USDA's septic-absorption-field interpretation. 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. Lake County, MT is 1,490.505 square miles with a population of 33,403.
What Lake County's reading doesn't cover
Nothing about Lake County, MT's SSURGO figure applies to a specific address - it's a county-wide average. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Lake County will actually do.
What a system would cost here
With 71.6% of Lake County rating "Very limited", a standard gravity system is not a safe assumption here. 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.
Where this sits nationally
Nationally, Lake County, MT is the 2,418-most-constrained of 3,058 rated counties for septic soil. Within Montana alone it ranks 42 of 54.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems