Septic soil in Clay County, SD, by the numbers

Very limited

88.2% of Clay County, SD'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 - 88.2% of it sits in USDA's most-constrained bucket. Clay County, SD is 412.022 square miles with a population of 15,245.

What Clay County's reading doesn't cover

Clay 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 Clay County will actually do.

What a system would cost here

With 88.2% of Clay 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.

How Clay County, SD compares

Nationally, Clay County, SD is the 1,451-most-constrained of 3,058 rated counties for septic soil. Within South Dakota alone it ranks 35 of 66.

Before you act on this

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