What St. Charles Parish, LA's soil rates for a septic system

Very limited

Soil across 60.2% of St. Charles Parish, LA rates "Very limited" in USDA's septic-absorption-field interpretation. 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. St. Charles Parish covers 277.742 square miles and counts 50,400 residents.

This is a county figure, not a parcel figure

Two lots a mile apart in St. Charles Parish can carry different soil, even though they share one countywide rating. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in St. Charles Parish.

System cost, conventional vs. engineered

Given St. Charles 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 St. Charles Parish, LA compares

Nationally, St. Charles Parish, LA is the 2,725-most-constrained of 3,058 rated counties for septic soil. Within Louisiana alone it ranks 60 of 61.

Further reading

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