Lewis County, ID: the USDA septic-suitability picture

Very limited

Lewis County, ID's SSURGO dominant class comes back "Very limited", covering 93.8% of the county. This is the reading that pushes a project toward an engineered system rather than a conventional one, and it covers 93.8% of Lewis County's land. For scale: 478.822 square miles and 3,728 people call Lewis County home.

Before you rely on this for one lot

Lewis County's rating is an average across the whole county, not a promise about any one lot inside it. The real answer for one lot is still a site-specific perc test, running about $750-$1,850 (typically near $1,300).

Budgeting for a system in Lewis County, ID

Lewis County's soil reading pushes the likely outcome toward an engineered system rather than a conventional one. Conventional systems run $3,000-$8,000 where they pass; where they don't, engineered alternatives (mound or aerobic treatment, whichever the health department requires) run $10,000-$40,000 - budget toward the higher figure until a perc test says otherwise.

Where this sits nationally

Among the 3,058 rated counties on this site, Lewis County, ID ranks 828 most-constrained nationally, and 7 of 44 within Idaho.

Further reading

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