Lyman 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 Lyman County, South Dakota.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Millboro silty clay, 3 to 6 percent slopes | 201K | Well drained | D | Very limited | Very limited |
| Sansarc-Opal clays, 9 to 25 percent slopes | 124K | Well drained | D | Very limited | Very limited |
| Opal-Sansarc clays, 6 to 15 percent slopes | 101K | Well drained | D | Very limited | Very limited |
| Millboro silty clay, 0 to 3 percent slopes | 61K | Well drained | D | Very limited | Very limited |
| Water | 49K | Not rated | Not rated | ||
| Promise clay, 0 to 3 percent slopes | 44K | Well drained | D | Very limited | Very limited |
| Millboro silty clay loam, 3 to 6 percent slopes | 35K | Well drained | D | Very limited | Very limited |
| Promise clay, 3 to 6 percent slopes | 35K | Well drained | D | Very limited | Very limited |
| Sansarc-Opal-Promise clays, 6 to 35 percent slopes | 32K | Well drained | D | Very limited | Very limited |
| Lakoma-Okaton silty clays, 6 to 15 percent slopes | 30K | Well drained | D | Very limited | Very limited |
| Opal-Promise clays, 6 to 9 percent slopes | 25K | Well drained | D | Very limited | Very limited |
| Boro-Millboro silty clays, 6 to 9 percent slopes | 25K | Well drained | D | Very limited | Very limited |
| Rock outcrop-Sansarc-Opal complex, 6 to 40 percent slopes | 25K | Well drained | D | Very limited | Very limited |
| Bullcreek clay, 0 to 6 percent slopes | 20K | Well drained | D | Very limited | Very limited |
| Opal clay, 3 to 6 percent slopes | 20K | Well drained | D | Very limited | Very limited |
| Wendte silty clay, channeled, occasionally flooded | 19K | Moderately well drained | D | Very limited | Very limited |
| Boro-Millboro silty clays, 3 to 6 percent slopes | 18K | Well drained | D | Very limited | Very limited |
| Kolls silty clay | 17K | Poorly drained | D | Very limited | Very limited |
| Capa silt loam, 0 to 6 percent slopes | 16K | Moderately well drained | D | Very limited | Somewhat limited |
| Promise-Capa complex, 0 to 3 percent slopes | 15K | Well drained | D | Very limited | Very limited |
What This Means
Building & Foundations
About 94% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 92% 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.