Washington County, Oklahoma
The most common soil here is Dennis, on about 16% of the land: a silt loam, smooth, like flour. Verdigris and Bates come next.
About 39% of the land drains well, and 41% stays wet for long stretches; groundwater comes within two feet of the surface under 56% of it.
USDA rates 97% of the land very limited for a standard septic drain field, and 85% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 19% 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, Oklahoma, 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 Mollisols — grassland soils with a thick, dark, fertile topsoil rich in organic matter. 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, Oklahoma. 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 |
|---|---|---|---|---|---|
| Dennis silt loam, 1 to 3 percent slopes | 37K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Bates-Coweta complex, 3 to 5 percent slopes | 30K | Well drained | C | Somewhat limited | Very limited |
| Shidler stony silty clay loam, 1 to 20 percent slopes | 20K | Well drained | D | Very limited | Very limited |
| Osage clay, 0 to 1 percent slopes, occasionally flooded | 19K | Poorly drained | D | Very limited | Very limited |
| Coweta-Eram complex, 5 to 20 percent slopes | 18K | Well drained | D | Very limited | Very limited |
| Verdigris clay loam, 0 to 1 percent slopes, occasionally flooded | 16K | Well drained | C | Very limited | Very limited |
| Eram-Verdigris complex, 0 to 12 percent slopes | 14K | Moderately well drained | D | Very limited | Very limited |
| Summit silty clay loam, 1 to 3 percent slopes | 14K | Moderately well drained | D | Very limited | Very limited |
| Okemah silt loam, 0 to 1 percent slopes | 13K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Dennis silt loam, 3 to 5 percent slopes | 11K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Verdigris silt loam, 0 to 1 percent slopes, frequently flooded | 10K | Well drained | B | Very limited | Very limited |
| Parsons silt loam, 0 to 1 percent slopes | 9K | Somewhat poorly drained | D | Very limited | Very limited |
| Water | 8K | Not rated | Not rated | ||
| Verdigris silt loam, 0 to 1 percent slopes, occasionally flooded | 7K | Well drained | B | Very limited | Very limited |
| Eram clay loam, 5 to 15 percent slopes | 6K | Moderately well drained | D | Very limited | Very limited |
| Summit silty clay loam, 3 to 5 percent slopes | 6K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Niotaze-Bigheart-Rock outcrop complex, 15 to 25 percent slopes, extremely stony | 6K | Somewhat poorly drained | D | Very limited | Very limited |
| Aliceville silty clay loam, 1 to 3 percent slopes | 4K | Moderately well drained | D | Very limited | Very limited |
| Bartlesville-Bigheart complex, 1 to 5 percent slopes, very rocky | 3K | Moderately well drained | C | Very limited | Very limited |
| Dennis silt loam, 3 to 5 percent slopes, eroded | 3K | Somewhat 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 85% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 97% 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
Drainage is generally favorable for gardening. Adding compost and mulch will improve fertility and water retention. Test your soil's pH before planting — most vegetables prefer 6.0-7.0.