Septic suitability in Smith County, MS
Very limited
USDA puts Smith County, MS at "Very limited" for septic absorption fields, the dominant reading across 86.3% of the county's soil. Practically, that rules out a simple gravity system for most of the county - 86.3% of it sits in USDA's most-constrained bucket. The county spans 636.268 square miles, home to 14,051 people.
What this number does and doesn't tell you
USDA's survey covers the whole of Smith County, MS at once, not any single address. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Smith County: conventional vs. engineered cost
86.3% of Smith 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.
Smith County's rank among Mississippi counties
Among the 3,058 rated counties on this site, Smith County, MS ranks 1,591 most-constrained nationally, and 57 of 82 within Mississippi.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems