What St. Clair County, IL's soil rates for a septic system

Very limited

In St. Clair County, IL, 83.7% 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 83.7% of the county. St. Clair County, IL is 657.748 square miles with a population of 251,149.

What St. Clair County's reading doesn't cover

St. Clair County's rating is an average across the whole county, not a promise about any one lot inside it. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in St. Clair County will actually do.

What a system would cost here

With 83.7% of St. Clair 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.

Where this sits nationally

Nationally, St. Clair County, IL is the 1,807-most-constrained of 3,058 rated counties for septic soil. Within Illinois alone it ranks 62 of 101.

Before you act on this

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