Mills County's SSURGO septic rating

Very limited

USDA puts Mills County, IA at "Very limited" for septic absorption fields, the dominant reading across 71% of the county's soil. 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. For scale: 437.431 square miles and 14,717 people call Mills County home.

Before you rely on this for one lot

Two lots a mile apart in Mills County can carry different soil, even though they share one countywide rating. 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 Mills County, IA

Mills 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, Mills County, IA ranks 2,434 most-constrained nationally, and 91 of 99 within Iowa.

Further reading

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