Lyman County, South Dakota
The most common soil here is Millboro, on about 25% of the land: a silty clay, smooth and very sticky when wet. Opal and Promise come next.
About 87% of the land drains well, and 2% stays wet for long stretches; groundwater comes within two feet of the surface under 2% of it.
USDA rates 91% of the land very limited for a standard septic drain field, and 92% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 2% of the land floods occasionally or more, and bedrock lies within 40 inches under 38% 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 Lyman County, South Dakota, 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 Vertisols — clay-rich soils that shrink and swell dramatically with moisture changes. 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. 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 |
|---|---|---|---|---|---|
| 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 |
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 92% 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 91% 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.