Union County, South Dakota
The most common soil here is Crofton, on about 12% of the land: a silt loam, smooth, like flour. Alcester and Moody come next.
About 57% of the land drains well, and 29% stays wet for long stretches; groundwater comes within two feet of the surface under 20% of it.
USDA rates 74% of the land very limited for a standard septic drain field, and 55% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 20% of the land floods occasionally or more.
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 Union 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 B (moderate infiltration). 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 Union 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 |
|---|---|---|---|---|---|
| Crofton-Nora complex, 6 to 11 percent slopes, eroded | 37K | Well drained | B | Somewhat limited | Somewhat limited |
| Alcester silty clay loam, 2 to 6 percent slopes | 26K | Well drained | C | Somewhat limited | Very limited |
| Forney silty clay | 16K | Poorly drained | D | Very limited | Very limited |
| Moody-Nora silty clay loams, 6 to 10 percent slopes | 15K | Well drained | B | Somewhat limited | Somewhat limited |
| Kennebec silty clay loam, 0 to 2 percent slopes, occasionally flooded | 12K | Moderately well drained | C | Very limited | Very limited |
| Wakonda-Worthing-Chancellor complex | 12K | Moderately well drained | C/D | Very limited | Very limited |
| Luton silty clay | 12K | Poorly drained | D | Very limited | Very limited |
| Crofton silt loam, 12 to 20 percent slopes, eroded | 11K | Well drained | B | Very limited | Very limited |
| Moody silty clay loam, 2 to 6 percent slopes | 11K | Well drained | C | Somewhat limited | Very limited |
| Calco silty clay loam, wet, 0 to 2 percent slopes, occasionally flooded | 9K | Very poorly drained | C/D | Very limited | Very limited |
| McPaul silt loam, 0 to 2 percent slopes, occasionally flooded | 9K | Well drained | B | Very limited | Very limited |
| Wentworth silty clay loam, 0 to 2 percent slopes | 9K | Well drained | C | Somewhat limited | Very limited |
| Albaton silty clay | 8K | Poorly drained | D | Very limited | Very limited |
| Haynie silt loam | 7K | Well drained | B | Very limited | Somewhat limited |
| Onawa silty clay | 6K | Somewhat poorly drained | C | Very limited | Very limited |
| Modale silt loam | 6K | Moderately well drained | C | Very limited | Very limited |
| Norway loamy sand | 5K | Poorly drained | A/D | Very limited | Very limited |
| Benclare silty clay loam, somewhat poorly drained | 5K | Somewhat poorly drained | D | Very limited | Very limited |
| Blyburg silt loam | 5K | Well drained | B | Very limited | Somewhat limited |
| Wentworth-Worthing silty clay loams | 4K | Well drained | C/D | Somewhat 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 55% of soils are rated "very limited" for dwellings with basements. Specific challenges include poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 74% 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
Drainage is generally favorable for gardening. Adding compost and mulch will improve fertility and water retention. Test your soil's pH before planting — most vegetables prefer 6.0-7.0.