Lewis and Clark National Forest Area, Montana

Survey Area MT632• Montana

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.

Mollisols

Fertile grassland soils with thick, dark topsoil. Among the best for agriculture, building, and gardening.

Alfisols

Moderately weathered forest soils with clay-enriched subsoil. Productive for agriculture, generally good for building and septic.

Inceptisols

Young but developing soils found in mountains and river terraces. Variable properties — check drainage and bedrock depth.

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.