Septic suitability in Lewis and Clark County, MT

Very limited

USDA puts Lewis and Clark County, MT at "Very limited" for septic absorption fields, the dominant reading across 83.7% of the county's soil. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 83.7% of the county. For scale: 3,458.38 square miles and 75,129 people call Lewis and Clark County home.

Before you rely on this for one lot

Lewis and Clark 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 and Clark County, MT

Lewis and Clark 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.

How Lewis and Clark County, MT compares

Among the 3,058 rated counties on this site, Lewis and Clark County, MT ranks 1,810 most-constrained nationally, and 19 of 54 within Montana.

Further reading

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