Clay County, MS: the USDA septic-suitability picture
Very limited
Clay County, MS's SSURGO dominant class comes back "Very limited", covering 97.4% of the county. A standard gravity system routinely fails on ground like this; the same share of the county falls in USDA's worst absorption-field bucket outright. The county spans 410.011 square miles, home to 18,213 people.
What this number does and doesn't tell you
This is a countywide, area-weighted figure across every soil survey map unit in Clay County, MS - never a reading for one specific parcel. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Clay County: conventional vs. engineered cost
97.4% of Clay County carrying a "Very limited" reading changes the realistic budget here. Conventional systems run $3,000-$8,000 where they pass; where they don't, engineered alternatives (mound or aerobic treatment, whichever the health department requires) run $10,000-$40,000 - budget toward the higher figure until a perc test says otherwise.
How Clay County, MS compares
Among the 3,058 rated counties on this site, Clay County, MS ranks 336 most-constrained nationally, and 18 of 82 within Mississippi.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems