Mellette County, South Dakota
The most common soil here is Lakoma, on about 10% of the land: a silty clay, smooth and very sticky when wet. Okaton and Promise come next.
About 94% of the land drains well.
USDA rates 89% of the land very limited for a standard septic drain field, and 73% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 5% of the land floods occasionally or more, and bedrock lies within 40 inches under 64% 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 Mellette 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 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 Mellette 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 |
|---|---|---|---|---|---|
| Okaton-Lakoma silty clays, 15 to 40 percent slopes | 124K | Well drained | D | Very limited | Very limited |
| Lakoma-Okaton silty clays, 6 to 15 percent slopes | 55K | Well drained | D | Very limited | Very limited |
| Imlay and Conata soils, 15 to 40 percent slopes | 39K | Well drained | D | Very limited | Very limited |
| Sansarc-Schamber complex, 9 to 35 percent slopes | 27K | Well drained | D | Very limited | Very limited |
| Promise clay, 3 to 6 percent slopes | 25K | Well drained | D | Very limited | Very limited |
| Imlay-Norrest silt loams, 9 to 25 percent slopes | 20K | Well drained | D | Very limited | Very limited |
| Millboro silty clay, 3 to 6 percent slopes | 18K | Well drained | D | Very limited | Very limited |
| Opal-Promise clays, 6 to 9 percent slopes | 17K | Well drained | D | Very limited | Very limited |
| Norrest-Imlay silt loams, 9 to 15 percent slopes | 15K | Well drained | C | Somewhat limited | Very limited |
| Ree and Keya loams, 0 to 2 percent slopes | 15K | Well drained | B | Not limited | Somewhat limited |
| Huggins-Epping silt loams, 5 to 15 percent slopes | 14K | Well drained | C | Very limited | Very limited |
| Imlay-Badland association | 14K | Well drained | D | Very limited | Very limited |
| Reliance silty clay loam, 0 to 3 percent slopes | 13K | Well drained | C | Somewhat limited | Very limited |
| Opal clay, mounded, 6 to 9 percent slopes | 13K | Well drained | D | Very limited | Very limited |
| Wendte silty clay loam, channeled | 11K | Moderately well drained | C | Very limited | Very limited |
| Ree and Keya loams, 2 to 5 percent slopes | 11K | Well drained | B | Not limited | Somewhat limited |
| Imlay and Conata soils, 6 to 15 percent slopes | 10K | Well drained | D | Very limited | Very limited |
| Schamber-Sansarc complex, 6 to 40 percent slopes | 10K | Well drained | D | Very limited | Very limited |
| Promise clay, 0 to 3 percent slopes | 10K | Well drained | D | Very limited | Very limited |
| Inavale and Munjor soils | 9K | Well drained | A | 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 73% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 89% 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.