What Crenshaw County, AL's soil rates for a septic system
Very limited
76.8% of Crenshaw County, AL's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 76.8% of the county. Crenshaw County covers 608.865 square miles and counts 13,114 residents.
This is a county figure, not a parcel figure
Nothing about Crenshaw County, AL's SSURGO figure applies to a specific address - it's a county-wide average. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Crenshaw County.
System cost, conventional vs. engineered
Given Crenshaw 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, Crenshaw County, AL is the 2,192-most-constrained of 3,058 rated counties for septic soil. Within Alabama alone it ranks 37 of 67.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems