Tripp County, South Dakota
The most common soil here is Millboro, on about 17% of the land: a silty clay, smooth and very sticky when wet. Anselmo and Lakoma come next.
About 89% of the land drains well, and 3% stays wet for long stretches.
USDA rates 95% of the land very limited for a standard septic drain field, and 58% 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 31% 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 Tripp 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 Tripp 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 | 98K | Well drained | D | Very limited | Very limited |
| Millboro silty clay, 0 to 3 percent slopes | 57K | Well drained | D | Very limited | Very limited |
| Lakoma-Millboro silty clays, 6 to 9 percent slopes | 57K | Well drained | D | Very limited | Very limited |
| Doger loamy fine sand, 0 to 6 percent slopes | 45K | Well drained | A | Not limited | Very limited |
| Lakoma-Okaton silty clays, 6 to 15 percent slopes | 44K | Well drained | D | Very limited | Very limited |
| Sansarc-Opal clays, 9 to 25 percent slopes | 41K | Well drained | D | Very limited | Very limited |
| Valentine-Dunday complex, 3 to 9 percent slopes | 32K | Excessively drained | A | Not limited | Very limited |
| Reliance silty clay loam, 3 to 6 percent slopes | 26K | Well drained | C | Somewhat limited | Very limited |
| Anselmo-Longpine fine sandy loams, 10 to 20 percent slopes | 25K | Well drained | A | Somewhat limited | Very limited |
| Boro-Millboro silty clays, 6 to 9 percent slopes | 24K | Well drained | D | Very limited | Very limited |
| Okaton-Lakoma silty clays, 15 to 40 percent slopes | 22K | Well drained | D | Very limited | Very limited |
| Witten silty clay, 0 to 3 percent slopes | 21K | Moderately well drained | C | Very limited | Very limited |
| Boyd-Okaton association, 9 to 25 percent slopes | 20K | Well drained | D | Very limited | Very limited |
| Dunday-Doger loamy fine sands, 3 to 9 percent slopes | 19K | Somewhat excessively drained | A | Not limited | Very limited |
| Dunday loamy fine sand, 3 to 9 percent slopes, eroded | 18K | Somewhat excessively drained | A | Not limited | Very limited |
| Anselmo-Vetal fine sandy loams, 0 to 3 percent slopes | 18K | Well drained | A | Not limited | Very limited |
| Reliance silty clay loam, 0 to 3 percent slopes | 17K | Well drained | C | Somewhat limited | Very limited |
| Millboro silty clay, 6 to 9 percent slopes | 16K | Well drained | D | Very limited | Very limited |
| Anselmo fine sandy loam, 3 to 6 percent slopes | 16K | Well drained | A | Not limited | Very limited |
| Anselmo-Holt fine sandy loams, 3 to 9 percent slopes | 14K | Well drained | A | Not 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 58% 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 95% 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.