Lewis and Clark National Forest Area, Montana
The dominant drainage class is Well drained and the dominant hydrologic group is C (slow infiltration, moderate 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 National Forest Area, Montana.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Dryadine, stony-Helmville families, complex, 35 to 70 percent slopes | 46K | Well drained | C | Very limited | Very limited |
| Cowcoulee, stony-Ettienridge families, complex, 35 to 70 percent slopes | 42K | Well drained | C | Very limited | Very limited |
| Ettienridge, very stony-Tropal, very rubbly, families-Rock outcrop complex, 50 to 70 percent slopes | 37K | Well drained | C | Very limited | Very limited |
| Tigeron, rubbly-Targhee, very bouldery-Como, very stony families, complex, 35 to 60 percent slopes | 36K | Well drained | B | Very limited | Very limited |
| Dryadine, very rubbly family-Monumentpeak, extremely stony-Helmville, very stony family, complex, 45 to 70 percent slopes | 34K | Well drained | C | Very limited | Very limited |
| Elve, extremely stony-Lake Creek, very stony-Comad, rubbly families, complex, 35 to 60 percent slopes | 33K | Well drained | C | Very limited | Very limited |
| Ettienridge, extremely stony-Checkerboard, rubbly families-Rock outcrop complex, 30 to 60 percent slopes | 27K | Well drained | C | Very limited | Very limited |
| Ettienridge, very stony-Checkerboard, extremely stony families-Rock outcrop complex, 50 to 70 percent slopes | 26K | Well drained | D | Very limited | Very limited |
| Tigeron, very stony-Como, extremely stony-Cowood, rubbly families, complex, 15 to 35 percent slopes | 24K | Well drained | B | Very limited | Very limited |
| Rubble land-Rock outcrop-Oorang family, very rubbly complex, 45 to 70 percent slopes | 20K | A | Not rated | Not rated | |
| Rubble land-Worock family, very rubbly complex, 20 to 70 percent slopes | 20K | A | Not rated | Not rated | |
| Targhee, extremely stony-Worock, very stony families-Rock outcrop complex, 15 to 35 percent slopes | 19K | Well drained | C | Very limited | Very limited |
| Dryadine, stony-Monumentpeak, extremely stony families, complex, 4 to 20 percent slopes | 19K | Well drained | C | Very limited | Very limited |
| Starman, extremely stony-Rock outcrop-Garlet, very rubbly families, complex, 35 to 70 percent slopes | 17K | Well drained | D | Very limited | Very limited |
| Tigeron, very stony-Como, extremely stony-Cowood, very rubbly families, complex, 35 to 60 percent slopes | 17K | Well drained | B | Very limited | Very limited |
| Ettienridge-Checkerboard, very stony-Cowcoulee, stony families, complex, 15 to 35 percent slopes | 16K | Well drained | C | Very limited | Very limited |
| Helmville, extremely stony-Ouselfal, very stony-Parkay, very stony families, complex, 15 to 60 percent slopes | 15K | Well drained | C | Very limited | Very limited |
| Jaegie, very stony-Lonniebee, extremely stony-Jefflake, stony families, complex, 1 to 8 percent slopes | 15K | Well drained | C | Very limited | Very limited |
| Maiden, stony-Lap, very stony families-Rock outcrop complex, 45 to 70 percent slopes | 15K | Well drained | D | Very limited | Very limited |
| Lonniebee-Como, very stony-Cowood, extremely stony families, complex, 4 to 15 percent slopes | 15K | Well drained | C | Very limited | Very limited |
What This Means
Building & Foundations
About 91% 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 91% 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.