Stanley County, South Dakota

Survey Area SD117• South Dakota

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 Stanley 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
Sansarc-Dupree, acid, clays, 6 to 25 percent slopes	149K	Well drained	D	Very limited	Very limited
Sansarc-Opal clays, 6 to 15 percent slopes	89K	Well drained	D	Very limited	Very limited
Promise clay, 3 to 6 percent slopes	84K	Well drained	D	Very limited	Very limited
Sansarc-Opal clays, 9 to 25 percent slopes	76K	Well drained	D	Very limited	Very limited
Promise clay, 0 to 3 percent slopes	63K	Well drained	D	Very limited	Very limited
Sansarc-Badland complex, 9 to 40 percent slopes	51K	Well drained	D	Very limited	Very limited
Water	50K			Not rated	Not rated
Opal clay, 3 to 6 percent slopes	46K	Well drained	D	Very limited	Very limited
Opal-Promise clays, 6 to 9 percent slopes	43K	Well drained	D	Very limited	Very limited
Bullcreek clay, 0 to 6 percent slopes	29K	Well drained	D	Very limited	Very limited
Lakoma-Okaton silty clays, 6 to 15 percent slopes	26K	Well drained	D	Very limited	Very limited
Chantier clay, 2 to 9 percent slopes	25K	Well drained	D	Very limited	Very limited
Chantier-Sansarc clays, 3 to 15 percent slopes	25K	Well drained	D	Very limited	Very limited
Opal-Chantier clays, 2 to 9 percent slopes	23K	Well drained	D	Very limited	Very limited
Okaton-Lakoma silty clays, 15 to 40 percent slopes	20K	Well drained	D	Very limited	Very limited
Capa silt loam, 0 to 6 percent slopes	13K	Moderately well drained	D	Very limited	Somewhat limited
Bullcreek-Slickspots complex, 0 to 6 percent slopes	13K	Well drained	D	Very limited	Very limited
Promise clay, 6 to 9 percent slopes	9K	Well drained	D	Very limited	Very limited
Carter-Capa silt loams, 0 to 3 percent slopes	8K	Moderately well drained	D	Very limited	Very limited
Wendte clay, channeled, occasionally flooded	8K	Moderately well 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.

Mollisols

Fertile grassland soils with thick, dark topsoil. Among the best for agriculture, building, and gardening.

Vertisols

High-clay soils that shrink and swell dramatically. Fertile but challenging for foundations and septic systems.

Entisols

Young soils with little development — found on floodplains, dunes, and steep slopes. Properties vary widely by setting.

Inceptisols

Young but developing soils found in mountains and river terraces. Variable properties — check drainage and bedrock depth.

What This Means

Building & Foundations

About 94% 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 92% 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.