Septic suitability in Oldham County, KY
Very limited
USDA puts Oldham County, KY at "Very limited" for septic absorption fields, the dominant reading across 76% of the county's soil. Practically, that rules out a simple gravity system for most of the county - 76% of it sits in USDA's most-constrained bucket. The county spans 187.294 square miles, home to 70,525 people.
What this number does and doesn't tell you
Oldham County's rating is an average across the whole county, not a promise about any one lot inside it. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Oldham County: conventional vs. engineered cost
76% of Oldham 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, Oldham County, KY ranks 2,235 most-constrained nationally, and 96 of 119 within Kentucky.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems