Washington County, Missouri
The dominant drainage class is Well drained and the dominant hydrologic group is D (very slow infiltration, high 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 Washington County, Missouri.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Alred-Sonsac complex, 15 to 35 percent slopes, very rocky, very stony | 91K | Well drained | D | Very limited | Very limited |
| Goss very cobbly silt loam, 15 to 50 percent slopes, extremely stony | 43K | Well drained | D | Very limited | Very limited |
| Rueter very gravelly silt loam, 15 to 35 percent slopes, very stony | 32K | Somewhat excessively drained | B | Very limited | Very limited |
| Useful-Courtois complex, 8 to 15 percent slopes, eroded | 25K | Moderately well drained | D | Very limited | Very limited |
| Goss gravelly silt loam, 3 to 15 percent slopes, stony | 18K | Well drained | D | Somewhat limited | Very limited |
| Rueter-Hildebrecht complex, 3 to 15 percent slopes, stony | 18K | Moderately well drained | C | Somewhat limited | Very limited |
| Alred-Rueter complex, 15 to 35 percent slopes, very stony | 17K | Well drained | C | Very limited | Very limited |
| Sonsac-Moko-Rock outcrop complex, 15 to 50 percent slopes, extremely stony | 17K | Well drained | D | Very limited | Very limited |
| Coulstone-Bender complex, 15 to 35 percent slopes, extremely stony | 16K | Somewhat excessively drained | B | Very limited | Very limited |
| Tiff gravelly clay, 1 to 20 percent slopes, very rocky | 15K | Well drained | D | Somewhat limited | Very limited |
| Cedargap gravelly silt loam, 1 to 3 percent slopes, frequently flooded | 14K | Well drained | B | Very limited | Very limited |
| Gravois silt loam, 8 to 15 percent slopes | 14K | Moderately well drained | C | Very limited | Very limited |
| Gravois silt loam, 3 to 8 percent slopes | 13K | Moderately well drained | C | Very limited | Very limited |
| Gravois-Goss complex, 3 to 15 percent slopes, stony | 13K | Moderately well drained | C | Very limited | Very limited |
| Cedargap gravelly silt loam, 0 to 2 percent slopes, frequently flooded | 11K | Well drained | B | Very limited | Very limited |
| Sonsac gravelly silt loam, 15 to 40 percent slopes, very stony | 11K | Well drained | D | Very limited | Very limited |
| Useful-Courtois complex, 3 to 8 percent slopes | 10K | Moderately well drained | D | Somewhat limited | Very limited |
| Caneyville-Rock outcrop complex, 8 to 15 percent slopes | 9K | Moderately well drained | C/D | Very limited | Very limited |
| Courtois-Goss complex, 8 to 15 percent slopes | 9K | Well drained | D | Somewhat limited | Very limited |
| Sonsac gravelly silt loam, 3 to 15 percent slopes, very stony | 9K | Well drained | D | Very limited | Very limited |
What This Means
Building & Foundations
About 82% of soils are rated "very limited" for dwellings with basements. Specific challenges include steep slopes, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 100% 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.