What Lemhi County, ID's soil rates for a septic system
Very limited
87.4% of Lemhi County, ID's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 87.4% of the county. Lemhi County, ID is 4,563.704 square miles with a population of 8,397.
What Lemhi County's reading doesn't cover
This is a countywide, area-weighted figure across every soil survey map unit in Lemhi County, ID - never a reading for one specific parcel. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Lemhi County will actually do.
What a system would cost here
With 87.4% of Lemhi 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.
How Lemhi County, ID compares
Nationally, Lemhi County, ID is the 1,519-most-constrained of 3,058 rated counties for septic soil. Within Idaho alone it ranks 22 of 44.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems