Whitman County, 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 Whitman County, Washington.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Palouse silt loam, 7 to 25 percent slopes | 266K | Well drained | B | Very limited | Very limited |
| Athena silt loam, 7 to 25 percent slopes | 176K | Well drained | A | Somewhat limited | Very limited |
| Walla Walla silt loam, 7 to 25 percent slopes | 144K | Well drained | B | Somewhat limited | Somewhat limited |
| Thatuna silt loam, 7 to 25 percent slopes | 69K | Moderately well drained | C | Very limited | Very limited |
| Palouse-Thatuna silt loams, 7 to 25 percent slopes | 62K | Well drained | B | Very limited | Very limited |
| Anders-Kuhl complex, 3 to 15 percent slopes | 55K | Well drained | C | Very limited | Very limited |
| Kuhl-Alpowa complex, 30 to 65 percent slopes | 52K | Well drained | D | Very limited | Very limited |
| Naff silt loam, 7 to 25 percent slopes | 28K | Well drained | C | Very limited | Very limited |
| Latah silt loam | 21K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Athena silt loam, 25 to 40 percent slopes | 18K | Well drained | A | Very limited | Very limited |
| Bakeoven-Tucannon complex, 0 to 30 percent slopes | 16K | Well drained | D | Very limited | Very limited |
| Walla Walla silt loam, 25 to 40 percent slopes | 15K | Well drained | B | Very limited | Very limited |
| Caldwell silt loam, 0 to 3 percent slopes | 15K | Somewhat poorly drained | C | Very limited | Very limited |
| Kuhl-Anders complex, 3 to 15 percent slopes | 15K | Well drained | D | Very limited | Very limited |
| Water | 14K | Not rated | Not rated | ||
| Starbuck-Alpowa complex, 30 to 65 percent slopes | 14K | Well drained | D | Very limited | Very limited |
| Snow silt loam, 7 to 15 percent slopes | 12K | Well drained | B | Somewhat limited | Somewhat limited |
| Naff-Garfield complex, 3 to 25 percent slopes | 12K | Well drained | C | Very limited | Very limited |
| Benge complex, 0 to 15 percent slopes | 11K | Well drained | B | Not limited | Very limited |
| Palouse silt loam, 25 to 40 percent slopes | 11K | Well drained | B | Very limited | Very limited |
What This Means
Building & Foundations
About 65% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 83% 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.