Macon County, AL: the USDA septic-suitability picture
Very limited
USDA puts Macon County, AL at "Very limited" for septic absorption fields, the dominant reading across 82.3% of the county's soil. Practically, that rules out a simple gravity system for most of the county - 82.3% of it sits in USDA's most-constrained bucket. The county spans 608.665 square miles, home to 18,159 people.
What this number does and doesn't tell you
Two lots a mile apart in Macon County can carry different soil, even though they share one countywide rating. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Macon County: conventional vs. engineered cost
82.3% of Macon 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.
Where this sits nationally
Among the 3,058 rated counties on this site, Macon County, AL ranks 1,908 most-constrained nationally, and 29 of 67 within Alabama.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems