Allen Parish, LA's soil, for a septic absorption field

Very limited

99.5% of Allen Parish, LA's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. A standard gravity system routinely fails on ground like this; the same share of the county falls in USDA's worst absorption-field bucket outright. Allen Parish covers 762.085 square miles and counts 22,501 residents.

This is a county figure, not a parcel figure

This is a countywide, area-weighted figure across every soil survey map unit in Allen Parish, LA - never a reading for one specific parcel. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Allen Parish.

System cost, conventional vs. engineered

Given Allen Parish'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.

How Allen Parish, LA compares

Nationally, Allen Parish, LA is the 25-most-constrained of 3,058 rated counties for septic soil. Within Louisiana alone it ranks 1 of 61.

Before you act on this

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