Septic soil in Logan County, IL, by the numbers

Very limited

86.8% of Logan County, IL's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. Practically, that rules out a simple gravity system for most of the county - 86.8% of it sits in USDA's most-constrained bucket. Logan County, IL is 618.052 square miles with a population of 27,518.

What Logan County's reading doesn't cover

Logan 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 Logan County will actually do.

What a system would cost here

With 86.8% of Logan 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.

Logan County's rank among Illinois counties

Nationally, Logan County, IL is the 1,560-most-constrained of 3,058 rated counties for septic soil. Within Illinois alone it ranks 55 of 101.

Before you act on this

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