Septic soil in Fremont County, ID, by the numbers
Very limited
In Fremont County, ID, 78.1% of the surveyed land carries a "Very limited" rating for a standard septic drain field. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 78.1% of the county. Fremont County, ID is 1,863.96 square miles with a population of 14,399.
What Fremont County's reading doesn't cover
Nothing about Fremont County, ID'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 Fremont County will actually do.
What a system would cost here
With 78.1% of Fremont 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 Fremont County, ID compares
Nationally, Fremont County, ID is the 2,134-most-constrained of 3,058 rated counties for septic soil. Within Idaho alone it ranks 33 of 44.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems