Colville Indian Reservation (Parts of Ferry and Okanogan Counties), Washington
The dominant drainage class is Well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). 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.
| 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 |
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.