Clay County, South Dakota
The most common soil here is Egan, on about 19% of the land: a silty clay loam, smooth and slightly sticky. Luton and Ethan come next.
About 57% of the land drains well, and 28% stays wet for long stretches; groundwater comes within two feet of the surface under 44% of it.
USDA rates 93% of the land very limited for a standard septic drain field, and 46% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 11% 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 Clay 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 C (slow infiltration, moderate 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 Clay 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 |
|---|---|---|---|---|---|
| Egan-Chancellor-Davison complex, 0 to 3 percent slopes | 25K | Well drained | C | Somewhat limited | Very limited |
| Egan-Ethan-Trent complex, 1 to 6 percent slopes | 19K | Well drained | C | Somewhat limited | Very limited |
| Egan-Clarno-Chancellor complex, 0 to 3 percent slopes | 17K | Well drained | C | Somewhat limited | Very limited |
| Luton silty clay, 0 to 2 percent slopes, rarely flooded | 16K | Poorly drained | D | Very limited | Very limited |
| Egan-Clarno-Trent complex, 0 to 2 percent slopes | 13K | Well drained | C | Somewhat limited | Very limited |
| Davison-Tetonka-Egan complex, 0 to 3 percent slopes | 11K | Moderately well drained | C | Somewhat limited | Very limited |
| Egan-Clarno-Tetonka complex, 0 to 2 percent slopes | 10K | Well drained | C | Somewhat limited | Very limited |
| Egan-Trent silty clay loams, 0 to 2 percent slopes | 10K | Well drained | C | Somewhat limited | Very limited |
| Blencoe silty clay, 0 to 2 percent slopes, clayey substratum | 10K | Somewhat poorly drained | C | Very limited | Very limited |
| Egan-Ethan-Tetonka complex, 0 to 6 percent slopes | 7K | Well drained | C | Somewhat limited | Very limited |
| Wakonda-Wentworth-Whitewood complex, 0 to 2 percent slopes | 7K | Moderately well drained | C | Very limited | Very limited |
| Egan-Clarno-Trent complex, 1 to 6 percent slopes | 6K | Well drained | C | Somewhat limited | Very limited |
| Baltic silty clay loam, 0 to 2 percent slopes, occasionally flooded | 5K | Poorly drained | C/D | Very limited | Very limited |
| Trent-Tetonka-Wakonda complex, 0 to 3 percent slopes | 4K | Moderately well drained | B | Very limited | Very limited |
| Owego silty clay, 0 to 2 percent slopes | 4K | Poorly drained | D | Very limited | Very limited |
| Egan-Trent-Chancellor silty clay loams, 0 to 2 percent slopes | 4K | Well drained | C | Somewhat limited | Very limited |
| Wentworth-Trent complex, 0 to 2 percent slopes | 3K | Well drained | C | Somewhat limited | Very limited |
| Blyburg silt loam, 0 to 2 percent slopes | 3K | Well drained | B | Very limited | Somewhat limited |
| Onawa silty clay, 0 to 2 percent slopes | 3K | Somewhat poorly drained | C | Very limited | Very limited |
| Albaton silty clay, 0 to 2 percent slopes | 3K | Poorly 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 46% of soils have significant building limitations, while the rest are generally suitable. Check specific sites carefully — conditions vary across the area.
Septic Systems
About 93% 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.