St. Mary Parish, Louisiana
The most common soil here is Maurepas, on about 9% of the land: a mucky clay, sticky when wet and rock-hard when dry. Kenner and Baldwin come next.
About 0% of the land drains well, and 89% stays wet for long stretches; groundwater comes within two feet of the surface under 78% of it.
USDA rates 84% of the land very limited for a standard septic drain field, and 83% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 60% of the land floods occasionally or more.
Soils change over short distances, so look up an address below for the soil at that exact spot and the reasons behind each rating.
The soils you're most likely standing on
The biggest named soils in St. Mary Parish, Louisiana, each drawn five feet deep from its official USDA description, in its recorded colors.
Dots mark gravel; white flecks mark lime. Shares are by acres across the survey area, and each mapped patch usually mixes several of these soils.
The biggest mapped areas
The dominant drainage class is Very poorly drained and the dominant hydrologic group is D (very slow infiltration, high runoff). The most common soil order is Alfisols — moderately leached forest soils with a clay-enriched subsoil. This report summarizes the major soil map units across the survey area to help you understand what to expect when buying, building, or gardening in St. Mary Parish, Louisiana. Search your address to find the exact soil composition, drainage, and series details at your specific location.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Water | 44K | Not rated | Not rated | ||
| Maurepas muck, 0 to 1 percent slopes, frequently flooded | 44K | Very poorly drained | A/D | Very limited | Very limited |
| Baldwin silty clay loam, 0 to 1 percent slopes | 42K | Poorly drained | D | Very limited | Very limited |
| Kenner muck, 0 to 1 percent slopes, very frequently flooded | 41K | Very poorly drained | D | Very limited | Very limited |
| Barbary muck, 0 to 1 percent slopes, frequently flooded | 38K | Very poorly drained | D | Very limited | Very limited |
| Larose muck, 0 to 0.5 percent slopes, tidal | 29K | Very poorly drained | C/D | Very limited | Very limited |
| Iberia clay, 0 to 1 percent slopes | 25K | Poorly drained | D | Very limited | Very limited |
| Allemands muck, 0 to 0.2 percent slopes, very frequently flooded | 25K | Very poorly drained | A/D | Very limited | Very limited |
| Aquents, dredged, 1 to 5 percent slopes, occasionally flooded | 20K | Very poorly drained | D | Not rated | Not rated |
| Schriever clay, 0 to 1 percent slopes, rarely flooded | 17K | Poorly drained | D | Very limited | Very limited |
| Balize silt loam, very frequently flooded | 15K | Very poorly drained | C/D | Very limited | Very limited |
| Hydraquents, Carville, and Glenwild soils, undulating, flooded | 14K | Very poorly drained | C | Very limited | Very limited |
| Schriever clay, 0 to 1 percent slopes, frequently flooded | 13K | Poorly drained | D | Very limited | Very limited |
| Carville and Hydraquents soils, undulating, flooded | 12K | Somewhat poorly drained | C | Very limited | Very limited |
| Galvez silt loam, 0 to 1 percent slopes | 11K | Somewhat poorly drained | C | Very limited | Very limited |
| Harahan and Allemands soils, drained | 8K | Poorly drained | D | Very limited | Very limited |
| Harahan clay, 0 to 1 percent slopes | 8K | Poorly drained | D | Very limited | Very limited |
| Uderts and Glenwild soils, 0 to 3 percent slopes, smoothed | 6K | Somewhat poorly drained | D | Very limited | Very limited |
| Fausse soils, 0 to 1 percent slopes, frequently flooded | 5K | Very poorly drained | C/D | Very limited | Very limited |
| Clovelly muck, 0 to 0.2 percent slopes, very frequently flooded | 4K | Very poorly drained | C/D | Very limited | Very limited |
Soil Orders in This Area
The USDA classifies every soil into one of 12 soil orders. Here are the dominant orders found in this survey area.
What This Means
Building & Foundations
About 83% of soils are rated "very limited" for dwellings with basements. Specific challenges include poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 84% of soils are rated "very limited" for septic absorption fields. Poorly drained soils can't absorb septic effluent effectively. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.
Gardening & Agriculture
Many soils hold water for extended periods. Raised beds are highly recommended to improve drainage for vegetables. Well-adapted native plants and water-loving species will do best in natural conditions.