Cowlitz 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 Cowlitz County, Washington.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Olympic silt loam, 8 to 20 percent slopes | 40K | Well drained | B | Somewhat limited | Somewhat limited |
| Hazeldell gravelly silt loam, 30 to 65 percent slopes | 34K | Well drained | B | Very limited | Very limited |
| Hazeldell gravelly silt loam, 20 to 30 percent slopes | 28K | Well drained | B | Very limited | Very limited |
| Olympic silt loam, 20 to 30 percent slopes | 20K | Well drained | B | Very limited | Very limited |
| Pheeney-Beigle complex, 30 to 65 percent slopes | 20K | Well drained | C | Very limited | Very limited |
| Hazeldell gravelly silt loam, tuff substratum, 30 to 65 percent slopes | 19K | Well drained | C | Very limited | Very limited |
| Gobar silt loam, 30 to 65 percent slopes | 19K | Well drained | B | Very limited | Very limited |
| Centralia silt loam, 20 to 30 percent slopes | 18K | Well drained | B | Very limited | Very limited |
| Olympic silt loam, tuff substratum, 5 to 30 percent slopes | 17K | Well drained | B | Very limited | Very limited |
| Cinebar silt loam, 5 to 20 percent slopes | 13K | Well drained | B | Somewhat limited | Somewhat limited |
| Caples silty clay loam, 0 to 3 percent slopes | 13K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Baumgard silt loam, 30 to 65 percent slopes | 11K | Well drained | B | Very limited | Very limited |
| Hazeldell gravelly silt loam, 8 to 20 percent slopes | 11K | Well drained | B | Somewhat limited | Somewhat limited |
| Pheeney-Beigle complex, 5 to 30 percent slopes | 11K | Well drained | C | Very limited | Very limited |
| Germany silt loam, 20 to 30 percent slopes | 10K | Well drained | B | Very limited | Very limited |
| Water | 10K | Not rated | Not rated | ||
| Swift sandy loam, 30 to 65 percent slopes | 8K | Well drained | B | Very limited | Very limited |
| Buckpeak silt loam, 30 to 65 percent slopes | 8K | Well drained | B | Very limited | Very limited |
| Mulholland silt loam, 5 to 30 percent slopes | 8K | Well drained | B | Very limited | Very limited |
| Vanson-Hatchet complex, 30 to 65 percent slopes | 8K | Well drained | B | Very limited | Very limited |
What This Means
Building & Foundations
About 77% of soils are rated "very limited" for dwellings with basements. Specific challenges include steep slopes, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 77% 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.