Arapaho-Roosevelt National Forest Area, Colorado, Parts of Boulder, Clear Creek, Gilpin, Grand, Park and Larimer Counties

Survey Area CO645• Colorado

The dominant drainage class is Somewhat excessively drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). The most common soil order is Inceptisols — young soils with minimal horizon development but more than Entisols. 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 Arapaho-Roosevelt National Forest Area, Colorado, Parts of Boulder, Clear Creek, Gilpin, Grand, Park and Larimer 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
Bullwark-Catamount families-Rock outcrop complex, 40 to 150 percent slopes	69K	Somewhat excessively drained	B	Very limited	Very limited
Leighcan family, till substratum, 5 to 40 percent slopes	63K	Somewhat excessively drained	C	Very limited	Very limited
Frisco-Catamount, moist families complex, 5 to 40 percent slopes	54K	Well drained	D	Somewhat limited	Very limited
Leighcan-Catamount, moist families complex, 5 to 40 percent slopes	51K	Somewhat excessively drained	C	Very limited	Very limited
Cypher-Wetmore-Ratake families complex, 5 to 40 percent slopes	51K	Somewhat excessively drained	D	Very limited	Very limited
Cypher-Ratake families complex, 5 to 40 percent slopes	50K	Somewhat excessively drained	D	Very limited	Very limited
Bullwark-Catamount families-Rubble land complex, 10 to 40 percent slopes	47K	Somewhat excessively drained	B	Very limited	Very limited
Leighcan family, 40 to 75 percent slopes	47K	Somewhat excessively drained	C	Very limited	Very limited
Leighcan family, 5 to 40 percent slopes	45K	Somewhat excessively drained	C	Very limited	Very limited
Leighcan family, till substratum-Cryaquolls complex, 5 to 40 percent slopes	44K	Somewhat excessively drained	C	Very limited	Very limited
Frisco, sandstone substratum-Howlett, moist-Scout, moist families complex, 5 to 40 percent slopes	39K	Well drained	B	Somewhat limited	Very limited
Cirque land, 40 to 150 percent slopes	37K			Very limited	Very limited
Leighcan family-Rock outcrop complex, 40 to 150 percent slopes, south aspects	36K	Somewhat excessively drained	C	Very limited	Very limited
Leighcan-Catamount, moist families-Rock outcrop complex, 40 to 150 percent slopes	33K	Somewhat excessively drained	C	Very limited	Very limited
Ratake-Cathedral families-Rock outcrop complex, 40 to 150 percent slopes	32K	Somewhat excessively drained	D	Very limited	Very limited
Typic Haplustolls-Cathedral family-Rock outcrop complex, 40 to 150 percent slopes	32K	Somewhat excessively drained	B	Very limited	Very limited
Leighcan family-Rock outcrop complex, 40 to 150 percent slopes	30K	Somewhat excessively drained	C	Very limited	Very limited
Cryaquolls-Gateview family complex, 0 to 15 percent slopes	29K	Poorly drained	B/D	Very limited	Very limited
Matcher family-Rock outcrop-Lithic Cryorthents complex, 40 to 150 percent slopes	28K	Excessively drained	D	Very limited	Very limited
Catamount, moist-Leighcan families-Rock outcrop complex, 5 to 40 percent slopes	27K	Excessively 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.

Inceptisols

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

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.

Entisols

Young soils with little development — found on floodplains, dunes, and steep slopes. Properties vary widely by setting.

What This Means

Building & Foundations

About 88% 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, sandy or gravelly soils with low bearing capacity. A geotechnical assessment is recommended before building.

Septic Systems

About 100% of soils are rated "very limited" for septic absorption fields. The well-drained soils may actually drain too fast for standard leach fields, allowing effluent to reach groundwater. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.

Gardening & Agriculture

Soils tend to drain very quickly, meaning nutrients and water don't stick around long. Raised beds with amended soil, drip irrigation, and heavy mulching will give the best results. Compost is your best friend here — it improves water retention dramatically.