Petroleum County, Montana
The dominant drainage class is Well drained and the dominant hydrologic group is D (very slow infiltration, high runoff). 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 Petroleum County, Montana.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Gerdrum-Vanda-Creed complex, 0 to 8 percent slopes | 71K | Well drained | D | Very limited | Not limited |
| Bascovy-Neldore-Neldore, moist, silty clays, 6 to 60 percent slopes | 55K | Well drained | D | Very limited | Very limited |
| Cabbart, moist-Blacksheep-Delpoint, calcareous complex, 6 to 60 percent slopes | 41K | Well drained | D | Very limited | Very limited |
| Neldore-Bascovy-Rock outcrop complex, 6 to 60 percent slopes | 39K | Well drained | D | Very limited | Very limited |
| Cabbart-Yawdim-Rock outcrop complex, 4 to 35 percent slopes | 37K | Well drained | D | Very limited | Very limited |
| Neldore, moist-Bascovy-Neldore, dry, silty clays, 6 to 60 percent slopes | 35K | Well drained | D | Very limited | Very limited |
| Delpoint-Cabbart-Yamac loams, 4 to 15 percent slopes | 34K | Well drained | C | Somewhat limited | Very limited |
| Gerdrum-Vanda complex, 1 to 6 percent slopes | 31K | Well drained | D | Very limited | Not limited |
| Gerdrum-Creed complex, 1 to 6 percent slopes | 31K | Well drained | D | Very limited | Not limited |
| Neldore-Abor silty clays, 15 to 45 percent slopes | 29K | Well drained | D | Very limited | Very limited |
| Evanston loam, 2 to 8 percent slopes | 26K | Well drained | B | Somewhat limited | Somewhat limited |
| Neldore-Abor silty clays, 4 to 15 percent slopes | 26K | Well drained | D | Very limited | Very limited |
| Bascovy-Neldore silty clays, 2 to 15 percent slopes | 23K | Well drained | D | Very limited | Very limited |
| Neldore-Rock outcrop complex, 15 to 60 percent slopes | 22K | Well drained | D | Very limited | Very limited |
| Yawdim-Orinoco complex, 4 to 15 percent slopes | 21K | Well drained | D | Very limited | Very limited |
| Cabbart-Delpoint-Cabbart, moist, loams, calcareous 4 to 35 percent slopes | 21K | Well drained | D | Very limited | Very limited |
| Verson clay loam, 0 to 4 percent slopes | 21K | Well drained | C | Not limited | Very limited |
| Neldore-Volborg silty clays, 4 to 25 percent slopes | 20K | Well drained | D | Very limited | Very limited |
| Twilight-Blacksheep sandy loams, 2 to 8 percent slopes | 18K | Well drained | B | Somewhat limited | Very limited |
| Yawdim-Crago complex, 4 to 35 percent slopes | 16K | Well drained | D | Very limited | Very limited |
What This Means
Building & Foundations
About 84% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes. 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
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.