Mercer County's SSURGO septic rating

Very limited

USDA puts Mercer County, IL at "Very limited" for septic absorption fields, the dominant reading across 57.7% of the county's soil. That reading means a conventional system is a poor bet here - 57.7% of Mercer County lands in the strictest "very limited" bucket USDA uses. For scale: 561.24 square miles and 15,292 people call Mercer County home.

Before you rely on this for one lot

This is a countywide, area-weighted figure across every soil survey map unit in Mercer County, IL - never a reading for one specific parcel. 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 Mercer County, IL

Mercer 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 Mercer County, IL compares

Among the 3,058 rated counties on this site, Mercer County, IL ranks 2,770 most-constrained nationally, and 96 of 101 within Illinois.

Before you act on this

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