Shelby County, AL's soil, for a septic absorption field

Very limited

79.4% of Shelby 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 79.4% of the county. Shelby County, AL is 785.455 square miles with a population of 235,969.

What Shelby County's reading doesn't cover

This is a countywide, area-weighted figure across every soil survey map unit in Shelby County, AL - never a reading for one specific parcel. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Shelby County will actually do.

What a system would cost here

With 79.4% of Shelby County rating "Very limited", a standard gravity system is not a safe assumption here. 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.

How Shelby County, AL compares

Nationally, Shelby County, AL is the 2,069-most-constrained of 3,058 rated counties for septic soil. Within Alabama alone it ranks 34 of 67.

Further reading

How this rating is built, and its real limits · Conventional vs. engineered septic systems