Washington County, Missouri
The most common soil here is Goss, on about 14% of the land: a gravelly silt loam, smooth, like flour. Sonsac and Alred come next.
About 72% of the land drains well; groundwater comes within two feet of the surface under 8% of it.
USDA rates 98% 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: 8% of the land floods occasionally or more, and bedrock lies within 40 inches under 39% of it.
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 Washington County, Missouri, 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 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 Washington County, Missouri. 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 |
|---|---|---|---|---|---|
| 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 |
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 steep slopes, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 98% 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.