Septic soil in Des Moines County, IA, by the numbers

Very limited

95.3% of Des Moines County, IA'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 - 95.3% of it sits in USDA's most-constrained bucket. Des Moines County, IA is 416.129 square miles with a population of 38,411.

What Des Moines County's reading doesn't cover

Two lots a mile apart in Des Moines County can carry different soil, even though they share one countywide rating. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Des Moines County will actually do.

What a system would cost here

With 95.3% of Des Moines 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.

Des Moines County's rank among Iowa counties

Nationally, Des Moines County, IA is the 630-most-constrained of 3,058 rated counties for septic soil. Within Iowa alone it ranks 46 of 99.

Further reading

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