Lewis and Clark National Forest Area, Montana
The most common soil here is Ettienridge, on about 5% of the land: a very gravelly loam, a balanced mix that crumbles in your hand. Dryadine and Helmville come next.
About 89% of the land drains well, and 3% stays wet for long stretches; groundwater comes within two feet of the surface under 6% of it.
USDA rates 93% of the land very limited for a standard septic drain field, and 89% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: bedrock lies within 40 inches under 85% 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 Lewis and Clark National Forest 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 C (slow infiltration, moderate 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 Lewis and Clark National Forest 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 |
|---|---|---|---|---|---|
| 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 |
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 89% 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 93% 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.