Septic soil in Clark County, SD, by the numbers

Very limited

92.4% of Clark 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 - 92.4% of it sits in USDA's most-constrained bucket. Clark County covers 957.512 square miles and counts 3,974 residents.

This is a county figure, not a parcel figure

Clark County's rating is an average across the whole county, not a promise about any one lot inside it. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Clark County.

System cost, conventional vs. engineered

Given Clark County's rating, plan for the engineered-system range rather than the conventional one. 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, Clark County, SD is the 994-most-constrained of 3,058 rated counties for septic soil. Within South Dakota alone it ranks 17 of 66.

Related guides

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