Septic soil in Hinds County, MS, by the numbers
Very limited
85.8% of Hinds County, MS'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 - 85.8% of it sits in USDA's most-constrained bucket. Hinds County covers 869.845 square miles and counts 211,975 residents.
This is a county figure, not a parcel figure
Hinds 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 Hinds County.
System cost, conventional vs. engineered
Given Hinds 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, Hinds County, MS is the 1,632-most-constrained of 3,058 rated counties for septic soil. Within Mississippi alone it ranks 58 of 82.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems