Columbia County Area, Washington
The dominant drainage class is Well drained and the dominant hydrologic group is B (moderate infiltration). 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 Columbia County Area, Washington.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Athena silt loam, 8 to 25 percent slopes | 50K | Well drained | B | Very limited | Very limited |
| Walla Walla silt loam, 8 to 30 percent slopes | 43K | Well drained | B | Very limited | Very limited |
| Gwin extremely rocky silt loam, 30 to 65 percent slopes | 21K | Well drained | C | Very limited | Very limited |
| Kuhl extremely rocky silt loam, 30 to 65 percent slopes | 20K | Well drained | D | Very limited | Very limited |
| Walla Walla silt loam, 30 to 40 percent slopes | 20K | Well drained | B | Very limited | Very limited |
| Athena silt loam, 25 to 40 percent slopes | 17K | Well drained | B | Very limited | Very limited |
| Rock outcrop | 11K | Very limited | Very limited | ||
| Palouse silt loam, 8 to 25 percent slopes | 10K | Well drained | B | Very limited | Very limited |
| Roloff-Kuhl complex, 30 to 65 percent slopes | 9K | Well drained | C | Very limited | Very limited |
| Tolo silt loam, 40 to 65 percent slopes | 8K | Well drained | C | Very limited | Very limited |
| Walla Walla silt loam, 40 to 65 percent slopes | 8K | Well drained | B | Very limited | Very limited |
| Ritzville silt loam, 8 to 30 percent slopes | 8K | Well drained | B | Very limited | Very limited |
| Athena silt loam, 0 to 8 percent slopes | 7K | Well drained | B | Not limited | Somewhat limited |
| Anatone extremely rocky silt loam, 30 to 65 percent slopes | 6K | Well drained | D | Very limited | Very limited |
| Larkin silt loam, 40 to 65 percent slopes | 6K | Well drained | C | Very limited | Very limited |
| Walla Walla silt loam, 0 to 8 percent slopes | 6K | Well drained | B | Not limited | Somewhat limited |
| Tolo silt loam, 3 to 15 percent slopes | 5K | Well drained | C | Somewhat limited | Very limited |
| Couse silt loam, 0 to 15 percent slopes, eroded | 4K | Moderately well drained | C | Very limited | Very limited |
| Klicker very rocky silt loam, 40 to 65 percent slopes | 4K | Well drained | C | Very limited | Very limited |
| Farrell very fine sandy loam, 15 to 30 percent slopes | 4K | Well drained | B | Very limited | Very limited |
What This Means
Building & Foundations
About 93% 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 95% 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.