Dewey County, South Dakota
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 Dewey County, South Dakota.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Sansarc-Opal clays, 9 to 25 percent slopes | 345K | Well drained | D | Very limited | Very limited |
| Water | 98K | Not rated | Not rated | ||
| Opal clay, 3 to 9 percent slopes | 83K | Well drained | D | Very limited | Very limited |
| Sansarc-Dupree, acid, clays, 6 to 25 percent slopes | 82K | Well drained | D | Very limited | Very limited |
| Opal-Sansarc clays, 6 to 15 percent slopes | 78K | Well drained | D | Very limited | Very limited |
| Dupree-Opal clays, 3 to 9 percent slopes | 65K | Well drained | D | Very limited | Very limited |
| Vebar fine sandy loam, 3 to 6 percent slopes | 54K | Well drained | B | Somewhat limited | Very limited |
| Morton silt loam, 2 to 6 percent slopes | 44K | Well drained | C | Somewhat limited | Very limited |
| Rhoades-Daglum complex, 0 to 6 percent slopes | 37K | Moderately well drained | D | Very limited | Somewhat limited |
| Wayden-Moreau silty clays, 25 to 40 percent slopes | 36K | Well drained | D | Very limited | Very limited |
| Regent-Ridgeview silty clay loams, 2 to 6 percent slopes | 36K | Well drained | D | Very limited | Very limited |
| Opal-Hurley complex, 0 to 9 percent slopes | 35K | Well drained | D | Very limited | Very limited |
| Chantier clay, 2 to 9 percent slopes | 33K | Well drained | D | Very limited | Very limited |
| Cabba-Lantry complex, 25 to 40 percent slopes | 26K | Well drained | D | Very limited | Very limited |
| Hurley-Slickspots complex, 2 to 9 percent slopes | 26K | Well drained | D | Very limited | Very limited |
| Morton-Lantry silt loams, 2 to 9 percent slopes | 25K | Well drained | C | Somewhat limited | Very limited |
| Belfield-Reeder loams, 2 to 6 percent slopes | 25K | Well drained | C | Very limited | Very limited |
| Moreau-Wayden silty clays, 9 to 25 percent slopes | 24K | Well drained | D | Very limited | Very limited |
| Promise-Wendte clays, channeled, occasionally flooded | 22K | Well drained | D | Very limited | Very limited |
| Promise clay, 3 to 6 percent slopes | 18K | Well drained | D | Very limited | Very limited |
What This Means
Building & Foundations
About 81% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes. 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.