Walworth County, South Dakota
The most common soil here is Highmore, on about 26% of the land: a silt loam, smooth, like flour. Mobridge and Williams come next.
About 80% of the land drains well, and 5% stays wet for long stretches; groundwater comes within two feet of the surface under 5% of it.
USDA rates 37% of the land very limited for a standard septic drain field, and 22% 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 9% 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 Walworth 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 Walworth 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 |
|---|---|---|---|---|---|
| Highmore silt loam, cool, 2 to 6 percent slopes | 63K | Well drained | B | Somewhat limited | Somewhat limited |
| Highmore-Eakin silt loams, cool, 2 to 6 percent slopes | 28K | Well drained | B | Somewhat limited | Somewhat limited |
| Water | 27K | Not rated | Not rated | ||
| Mobridge silt loam, cool, 0 to 2 percent slopes | 22K | Moderately well drained | B | Somewhat limited | Somewhat limited |
| Williams-Bowbells loams, 3 to 6 percent slopes | 21K | Well drained | B | Somewhat limited | Somewhat limited |
| Highmore silt loam, cool, 0 to 2 percent slopes | 20K | Well drained | B | Somewhat limited | Somewhat limited |
| Sansarc-Opal clays, 9 to 25 percent slopes | 18K | Well drained | D | Very limited | Very limited |
| Highmore silt loam, 2 to 6 percent slopes | 17K | Well drained | C | Somewhat limited | Very limited |
| Williams-Zahl-Zahill complex, 6 to 9 percent slopes | 16K | Well drained | B | Somewhat limited | Somewhat limited |
| Opal-Sansarc silty clays, very stony, 6 to 15 percent slopes | 15K | Well drained | D | Very limited | Very limited |
| Highmore silt loam, cool, 6 to 9 percent slopes | 10K | Well drained | B | Somewhat limited | Somewhat limited |
| Opal silty clay, very stony, 3 to 9 percent slopes | 9K | Well drained | D | Very limited | Very limited |
| Highmore-Bearpaw complex, cool, 6 to 9 percent slopes | 8K | Well drained | B | Somewhat limited | Somewhat limited |
| Highmore-Bearpaw complex, cool, 2 to 6 percent slopes | 7K | Well drained | B | Somewhat limited | Somewhat limited |
| Agar silt loam, cool, 2 to 6 percent slopes | 7K | Well drained | B | Somewhat limited | Somewhat limited |
| Bearpaw-Gettys complex, cool, 6 to 15 percent slopes | 7K | Well drained | C | Somewhat limited | Somewhat limited |
| Promise clay, 3 to 6 percent slopes | 7K | Well drained | D | Very limited | Very limited |
| Zahl-Williams-Zahill complex, 6 to 9 percent slopes | 6K | Well drained | B | Somewhat limited | Somewhat limited |
| Promise clay, 0 to 3 percent slopes | 6K | Well drained | D | Very limited | Very limited |
| Gettys clay loam, cool, 9 to 40 percent slopes | 6K | Well drained | C | 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 22% of soils have significant building limitations, while the rest are generally suitable. Check specific sites carefully — conditions vary across the area.
Septic Systems
About 37% of soils have significant septic limitations, while others are more suitable. A perc test is essential — conditions vary across the area.
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.