St. Mary's County, Maryland
The most common soil here is Beltsville, on about 13% of the land: a silt loam, smooth, like flour. Othello and Sassafras come next.
About 40% of the land drains well, and 19% stays wet for long stretches; groundwater comes within two feet of the surface under 20% of it.
USDA rates 88% of the land very limited for a standard septic drain field, and 58% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 9% 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's County, Maryland, 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 Well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). The most common soil order is Ultisols — strongly weathered soils with clay-enriched subsoils, common in warm humid climates. 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's County, Maryland. 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 |
|---|---|---|---|---|---|
| Beltsville silt loam, 2 to 5 percent slopes, moderately eroded | 33K | Moderately well drained | C | Very limited | Very limited |
| Water | 28K | Not rated | Not rated | ||
| Othello silt loams, 0 to 2 percent slopes, Northern Coastal Plain | 18K | Poorly drained | C/D | Very limited | Very limited |
| Evesboro-Westphalia complex, 20 to 45 percent slopes, moderately eroded | 16K | Well drained | B | Very limited | Very limited |
| Bibb silt loam, frequently flooded | 13K | Poorly drained | B/D | Very limited | Very limited |
| Evesboro-Westphalia complex, 12 to 20 percent slopes, moderately eroded | 9K | Well drained | B | Very limited | Very limited |
| Croom gravelly sandy loam, 10 to 15 percent slopes, severely eroded | 8K | Well drained | C | Somewhat limited | Very limited |
| Croom gravelly sandy loam, 10 to 15 percent slopes, moderately eroded | 6K | Well drained | C | Somewhat limited | Very limited |
| Sassafras sandy loam, 2 to 5 percent slopes, Northern Coastal Plain | 6K | Well drained | B | Not limited | Very limited |
| Elkton silt loam | 6K | Poorly drained | C/D | Very limited | Very limited |
| Mattapex silt loam, 0 to 2 percent slopes, Northern Coastal Plain | 5K | Moderately well drained | C | Very limited | Very limited |
| Sassafras sandy loam, 5 to 10 percent slopes, Northern Coastal Plain | 5K | Well drained | B | Not limited | Very limited |
| Beltsville silt loam, 5 to 10 percent slopes, severely eroded | 5K | Moderately well drained | C | Very limited | Very limited |
| Othello fine sandy loam, 0 to 2 percent slopes | 5K | Poorly drained | C/D | Very limited | Very limited |
| Evesboro loamy sand, 0 to 8 percent slopes | 4K | Excessively drained | A | Not limited | Very limited |
| Alluvial land | 4K | Moderately well drained | B | Very limited | Very limited |
| Mattapex fine sandy loam, 0 to 2 percent slopes | 4K | Moderately well drained | C | Very limited | Very limited |
| Tidal marsh | 4K | Very poorly drained | D | Very limited | Very limited |
| Chillum loam, 2 to 5 percent slopes moderately eroded | 4K | Well drained | C | Not limited | Very limited |
| Matapeake silt loam, 0 to 2 percent slopes | 3K | Well drained | C | Not 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 58% of soils are rated "very limited" for dwellings with basements. Specific challenges include steep slopes, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 88% of soils are rated "very limited" for septic absorption fields. Despite good drainage overall, limitations may stem from shallow bedrock, steep slopes, or seasonal conditions. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.
Gardening & Agriculture
Well-drained soils on sloped terrain — good for most plants but watch for erosion. Terracing, contour planting, and mulching help retain moisture and topsoil. Drip irrigation is more effective than sprinklers on slopes.