Lewis and Clark County Area, 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 Lewis and Clark County Area, Montana.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Holter-Castner channery loams, 8 to 45 percent slopes | 50K | Well drained | C | Very limited | Very limited |
| Tolex-Mocmont-Rock outcrop complex, 25 to 60 percent slopes | 39K | Well drained | D | Very limited | Very limited |
| Reeder-Regent-Cabba loams, 2 to 8 percent slopes | 37K | Well drained | D | Very limited | Very limited |
| Reeder-Regent-Cabba loams, 8 to 25 percent slopes | 35K | Well drained | D | Very limited | Very limited |
| Castner-Tolex-Rock outcrop complex, 8 to 60 percent slopes | 32K | Well drained | D | Very limited | Very limited |
| Hauz-Sieben-Tolman channery loams, 8 to 45 percent slopes | 31K | Well drained | C | Very limited | Very limited |
| Reeder-Regent-Castner complex, 8 to 25 percent slopes | 30K | Well drained | D | Very limited | Very limited |
| Fairfield-Beanlake-Winspect stony loams, 2 to 25 percent slopes | 28K | Well drained | C | Somewhat limited | Very limited |
| Castner-Holter-Rock outcrop complex, 15 to 60 percent slopes | 25K | Well drained | D | Very limited | Very limited |
| Beanlake-Winspect stony loams, dry, 2 to 25 percent slopes | 22K | Well drained | B | Somewhat limited | Somewhat limited |
| Mocmont-Tolex complex, 25 to 60 percent slopes | 22K | Well drained | A | Very limited | Very limited |
| Fluvaquents and Fluvaquentic Haplustolls soils, 0 to 4 percent slopes | 22K | Poorly drained | C | Very limited | Very limited |
| Water | 21K | Not rated | Not rated | ||
| Beanlake-Winspect stony loams, 4 to 25 percent slopes | 21K | Well drained | B | Very limited | Very limited |
| Mocmont-Tolex complex, cool, 25 to 60 percent slopes | 21K | Well drained | A | Very limited | Very limited |
| Musselshell-Crago complex, 2 to 8 percent slopes | 20K | Well drained | B | Not limited | Somewhat limited |
| Reeder-Castner-Rock outcrop complex, 8 to 45 percent slopes | 17K | Well drained | C | Very limited | Very limited |
| Sappington-Amesha loams, 1 to 4 percent slopes | 16K | Well drained | B | Not limited | Somewhat limited |
| Regent-Reeder-Work stony loams, 4 to 30 percent slopes | 14K | Well drained | C | Very limited | Very limited |
| Marmarth-Delpoint loams, 2 to 8 percent slopes | 14K | Well drained | C | Somewhat limited | Very limited |
What This Means
Building & Foundations
About 76% 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 84% 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.