Orleans Parish, LA has no septic-suitability rating on file
Unrated
The dominant soil here (often already-developed urban land) carries no septic-suitability interpretation from USDA - too rare a gap to guess at. A local percolation test is the only way to know. Orleans Parish, LA covers 169.578 square miles and is home to 362,701 people, but the dominant soil here carries no SSURGO absorption-field interpretation to report.
What Orleans Parish's reading doesn't cover
Two lots a mile apart in Orleans Parish can carry different soil, even though they share one countywide rating. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Orleans Parish will actually do.
What a system would cost here
Orleans Parish carries no dominant soil rating, so there's no shortcut here - it comes down entirely to the site-specific test. Nationally, conventional systems run $3,000-$8,000 and engineered alternatives run $10,000-$40,000 - which one applies to a lot in Orleans Parish is exactly what a perc test settles.
Further reading
How this rating is built, and its real limits · What to check before buying rural land on septic