Stillwater County Area, Montana
The most common soil here is Tanna, on about 16% of the land: a clay loam, firm and a little sticky. Lambeth and Absarokee come next.
About 93% of the land drains well, and 4% stays wet for long stretches.
USDA rates 89% of the land very limited for a standard septic drain field, and 53% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 1% of the land floods occasionally or more, and bedrock lies within 40 inches under 74% 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 Stillwater County Area, Montana, 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 Entisols — young soils with little profile development, often on floodplains or steep slopes. 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 Stillwater County Area, Montana. 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 |
|---|---|---|---|---|---|
| Tanna-Rentsac complex, 4 to 15 percent slopes | 143K | Well drained | D | Somewhat limited | Very limited |
| Yawdim-Lambeth-Rock outcrop association, steep | 123K | Well drained | D | Very limited | Very limited |
| Hilger-Castner-Rock outcrop complex, 25 to 60 percent slopes | 52K | Well drained | D | Very limited | Very limited |
| Tanna clay loam, 2 to 8 percent slopes | 47K | Well drained | D | Somewhat limited | Very limited |
| Wayden-Castner association, steep | 41K | Well drained | D | Very limited | Very limited |
| Birney-Yawdim-Rock outcrop association, steep | 38K | Well drained | B | Very limited | Very limited |
| Lambeth-Yawdim complex, 4 to 15 percent slopes | 33K | Well drained | C | Somewhat limited | Very limited |
| Tanna-Beenom complex, 4 to 8 percent slopes | 33K | Well drained | D | Somewhat limited | Very limited |
| Absarokee-Sinnigam complex, 15 to 50 percent slopes | 27K | Well drained | D | Very limited | Very limited |
| Absarokee-Sinnigam clay loams, 8 to 15 percent slopes | 25K | Well drained | C | Very limited | Very limited |
| Lardell clay loam, 0 to 2 percent slopes | 25K | Somewhat poorly drained | C | Very limited | Very limited |
| Bonfri-Lambeth complex, 2 to 8 percent slopes | 21K | Well drained | C | Somewhat limited | Very limited |
| Winkler-Hilger-Rock outcrop association, steep | 21K | Somewhat excessively drained | A | Very limited | Very limited |
| Absarokee-Sinnigam clay loams, 2 to 8 percent slopes | 19K | Well drained | C | Very limited | Very limited |
| McKenzie clay, saline | 15K | Poorly drained | D | Very limited | Very limited |
| Absher silty clay loam, 0 to 8 percent slopes | 14K | Well drained | D | Somewhat limited | Not limited |
| Lonna silt loam, 2 to 8 percent slopes | 13K | Well drained | B | Not limited | Somewhat limited |
| Absarokee clay loam, 2 to 8 percent slopes | 12K | Well drained | C | Very limited | Very limited |
| Torrifluvents-Camborthids association, gently sloping | 12K | Not rated | Not rated | ||
| Work loam, 4 to 8 percent slopes | 12K | Well drained | C | 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 53% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 89% 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.