St. Mary's County, Maryland
The dominant drainage class is Well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). 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.
| 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 |
What This Means
Building & Foundations
About 65% 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 85% 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.