Colville Indian Reservation (Parts of Ferry and Okanogan Counties), Washington
The most common soil here is Nevine, on about 5% of the land: a ashy loam, a balanced mix that crumbles in your hand. Conconully and Timentwa come next.
About 92% of the land drains well, and 2% stays wet for long stretches; groundwater comes within two feet of the surface under 4% of it.
USDA rates 87% of the land very limited for a standard septic drain field, and 73% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 2% of the land floods occasionally or more, and bedrock lies within 40 inches under 38% 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 Colville Indian Reservation (Parts of Ferry and Okanogan Counties), Washington, 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 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.
What This Means
Building & Foundations
About 73% 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 87% 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.