Colville Indian Reservation (Parts of Ferry and Okanogan Counties), Washington

Survey Area WA648• Washington

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 Colville Indian Reservation (Parts of Ferry and Okanogan Counties), Washington. 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
Nevine silt loams association, 20 to 40 percent slopes	34K	Well drained	C	Very limited	Very limited
Swakane-Rock outcrop complex, 30 to 70 percent slopes	23K	Well drained	D	Very limited	Very limited
Mineral-Rock outcrop complex, 20 to 40 percent slopes	21K	Well drained	B	Very limited	Very limited
Timentwa loam, 0 to 8 percent slopes	20K	Well drained	B	Not limited	Somewhat limited
Nevine silt loams association, 5 to 20 percent slopes	19K	Well drained	C	Somewhat limited	Somewhat limited
Manley silt loam, dry, 20 to 40 percent slopes	18K	Well drained	D	Very limited	Very limited
Couleedam-Rock outcrop complex, 30 to 70 percent slopes	18K	Well drained	D	Very limited	Very limited
Timentwa very bouldery loam, 0 to 30 percent slopes	15K	Well drained	B	Somewhat limited	Somewhat limited
Donavan loam, dry, 5 to 15 percent slopes	13K	Well drained	B	Somewhat limited	Somewhat limited
Conconully stony fine sandy loam, 3 to 25 percent slopes	13K	Well drained	C	Somewhat limited	Somewhat limited
Nevine-Rock outcrop association, 20 to 40 percent slopes	13K	Well drained	C	Very limited	Very limited
Baldknob-Thout, dry,-Rock outcrop complex, 20 to 65 percent slopes	13K	Well drained	D	Very limited	Very limited
Centralpeak loams association, 20 to 40 percent slopes	12K	Well drained	C	Very limited	Very limited
Conconully bouldery fine sandy loam, 5 to 30 percent slopes	12K	Well drained	C	Very limited	Very limited
Inkler gravelly ashy silt loam, dry, 20 to 40 percent	12K	Well drained	B	Very limited	Very limited
Rock outcrop	11K			Very limited	Very limited
Malott stony very fine sandy loam, 3 to 25 percent slopes	11K	Well drained	B	Somewhat limited	Somewhat limited
Oxerine silt loam, 40 to 65 percent slopes	10K	Well drained	C	Very limited	Very limited
Merkel sandy loam, 20 to 40 percent slopes	10K	Well drained	B	Very limited	Very limited
Spokane loam, 20 to 40 percent slopes	10K	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.

Inceptisols

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

Entisols

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

Andisols

Volcanic ash soils — light, porous, and fertile. Excellent drainage, but low density can complicate foundations.

What This Means

Building & Foundations

About 70% of soils are rated "very limited" for dwellings with basements. Specific challenges include steep slopes. A geotechnical assessment is recommended before building.

Septic Systems

About 70% 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.