Gilliam County, Oregon
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 Gilliam County, Oregon.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Lickskillet-Rock outcrop complex, 40 to 70 percent slopes | 92K | Well drained | D | Very limited | Very limited |
| Ritzville silt loam, 2 to 7 percent slopes | 59K | Well drained | B | Not limited | Somewhat limited |
| Wrentham-Rock outcrop complex, 35 to 70 percent slopes | 58K | Well drained | C | Very limited | Very limited |
| Lickskillet very stony loam, 7 to 40 percent slopes | 46K | Well drained | D | Very limited | Very limited |
| Condon and Valby silt loams, 1 to 7 percent slopes | 44K | Well drained | C | Very limited | Very limited |
| Morrow silt loam, 1 to 7 percent slopes | 36K | Well drained | C | Very limited | Very limited |
| Bakeoven-Condon complex, 2 to 20 percent slopes | 35K | Well drained | D | Very limited | Very limited |
| Condon and Valby silt loams, 7 to 12 percent slopes | 27K | Well drained | C | Very limited | Very limited |
| Ritzville silt loam, 7 to 12 percent slopes | 25K | Well drained | B | Somewhat limited | Somewhat limited |
| Mikkalo silt loam, 7 to 12 percent slopes | 21K | Well drained | C | Very limited | Very limited |
| Bakeoven-Morrow complex, 2 to 20 percent slopes | 19K | Well drained | D | Very limited | Very limited |
| Waha-Rockly complex, 2 to 20 percent slopes | 16K | Well drained | D | Very limited | Very limited |
| Mikkalo silt loam, 2 to 7 percent slopes | 14K | Well drained | C | Very limited | Very limited |
| Olex silt loam, 0 to 5 percent slopes | 13K | Well drained | B | Not limited | Somewhat limited |
| Willis silt loam, 2 to 5 percent slopes | 12K | Well drained | C | Somewhat limited | Very limited |
| Ritzville silt loam, 12 to 20 percent slopes | 12K | Well drained | B | Very limited | Very limited |
| Roloff-Rock outcrop complex, 1 to 20 percent slopes | 12K | Well drained | C | Very limited | Very limited |
| Water | 12K | Not rated | Not rated | ||
| Ritzville silt loam, 20 to 40 percent north slopes | 10K | Well drained | B | Very limited | Very limited |
| Morrow silt loam, 7 to 12 percent slopes | 9K | Well drained | C | Very limited | Very limited |
What This Means
Building & Foundations
About 79% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes. A geotechnical assessment is recommended before building.
Septic Systems
About 81% 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.