Rio Grande NF Area, Colorado, West Part, Parts of Archuleta, Conejos, Hinsdale, Mineral, Rio Grande, Saguache, and San Juan Counties

Survey Area CO664• Colorado

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 Rio Grande NF Area, Colorado, West Part, Parts of Archuleta, Conejos, Hinsdale, Mineral, Rio Grande, Saguache, and San Juan Counties. 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
Frisco-Agneston association, 5 to 50 percent slopes	141K	Well drained	A	Very limited	Very limited
Seitz cobbly loam, 15 to 60 percent slopes	111K	Well drained	C	Very limited	Very limited
Cryoboralfs-Rock outcrop complex, 35 to 75 percent slopes	106K	Well drained	C	Very limited	Very limited
Leighcan-Frisco association, 5 to 60 percent slopes	72K	Well drained	A	Very limited	Very limited
Cryumbrepts-Rock outcrop-Rubble land complex, 20 to 80 percent slopes	69K	Well drained	D	Very limited	Very limited
Mirror-Teewinot association, 8 to 45 percent slopes	64K	Well drained	B	Very limited	Very limited
Rock outcrop and Rubble land	64K		D	Not rated	Not rated
Frisco-Scout association, 15 to 60 percent slopes	64K	Well drained	A	Very limited	Very limited
Leighcan-Endlich association, 2 to 50 percent slopes	59K	Well drained	A	Very limited	Very limited
Endlich-Hechtman association, 5 to 60 percent slopes	58K	Well drained	B	Very limited	Very limited
Tellura, moist-Seitz association, 15 to 60 percent slopes	56K	Well drained	C	Very limited	Very limited
Pergrin-Agneston-Hechtman association, 15 to 60 percent slopes	53K	Well drained	B	Very limited	Very limited
Cryaquolls-Cryoborolls association, 0 to 20 percent slopes	52K	Poorly drained	C	Very limited	Very limited
Seitz-Winz association, 8 to 60 percent slopes	48K	Well drained	C	Very limited	Very limited
Seitz cobbly loam, dry, 15 to 60 percent slopes	45K	Well drained	C	Very limited	Very limited
Cryoborolls-Cryochrepts-Rock outcrop complex, 15 to 80 percent slopes	37K	Well drained	C	Very limited	Very limited
Cryochrepts-Rock outcrop association, 5 to 70 percent slopes	36K	Well drained	C	Very limited	Very limited
Tellura-Gothic association, 2 to 45 percent slopes	34K	Well drained	C	Very limited	Very limited
Bowen, cool-Agneston association, 15 to 50 percent slopes	33K	Well drained	C	Very limited	Very limited
Embargo-Tellura association, 12 to 50 percent slopes	32K	Well drained	D	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 94% 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 94% 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.