Polk County, Oregon
The most common soil here is Jory, on about 7% of the land: a silty clay loam, smooth and slightly sticky. Valsetz and Klickitat come next.
About 69% of the land drains well, and 18% stays wet for long stretches; groundwater comes within two feet of the surface under 18% of it.
USDA rates 96% of the land very limited for a standard septic drain field, and 84% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 11% of the land floods occasionally or more, and bedrock lies within 40 inches under 40% of it.
Soils change over short distances, so look up an address below for the soil at that exact spot and the reasons behind each rating.
The soils you're most likely standing on
The biggest named soils in Polk County, Oregon, each drawn five feet deep from its official USDA description, in its recorded colors.
Dots mark gravel; white flecks mark lime. Shares are by acres across the survey area, and each mapped patch usually mixes several of these soils.
The biggest mapped areas
The dominant drainage class is Well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). The most common soil order is Ultisols — strongly weathered soils with clay-enriched subsoils, common in warm humid climates. 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 Polk County, Oregon. Search your address to find the exact soil composition, drainage, and series details at your specific location.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Kilchis-Klickitat complex, 60 to 90 percent slopes | 22K | Well drained | D | Very limited | Very limited |
| Woodburn silt loam, 0 to 3 percent slopes | 16K | Moderately well drained | C | Very limited | Very limited |
| Bohannon gravelly loam, 50 to 75 percent slopes | 15K | Well drained | B | Very limited | Very limited |
| Valsetz-Yellowstone complex, 50 to 90 percent slopes | 14K | Well drained | B | Very limited | Very limited |
| Waldo silty clay loam | 14K | Poorly drained | C/D | Very limited | Very limited |
| Dayton silt loam | 13K | Poorly drained | D | Very limited | Very limited |
| Jory silty clay loam, 12 to 20 percent slopes | 13K | Well drained | C | Very limited | Very limited |
| Valsetz stony loam, 50 to 75 percent slopes | 11K | Well drained | B | Very limited | Very limited |
| Amity silt loam | 11K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Klickitat gravelly clay loam, 50 to 75 percent slopes | 10K | Well drained | B | Very limited | Very limited |
| Jory silty clay loam, 20 to 30 percent slopes | 9K | Well drained | C | Very limited | Very limited |
| Woodburn silt loam, 3 to 12 percent slopes | 9K | Moderately well drained | C | Very limited | Very limited |
| Blachly silty clay loam, 3 to 30 percent slopes | 9K | Well drained | C | Very limited | Very limited |
| Honeygrove silty clay loam, 3 to 25 percent slopes | 8K | Well drained | C | Somewhat limited | Very limited |
| Bellpine silty clay loam, 3 to 12 percent slopes | 7K | Well drained | C | Somewhat limited | Very limited |
| Helmick silt loam, 3 to 12 percent slopes | 7K | Somewhat poorly drained | D | Very limited | Very limited |
| Valsetz stony loam, 3 to 30 percent slopes | 7K | Well drained | B | Very limited | Very limited |
| Astoria silt loam, 5 to 30 percent slopes | 7K | Well drained | B | Very limited | Very limited |
| Astoria silt loam, 30 to 60 percent slopes | 7K | Well drained | B | Very limited | Very limited |
| Jory silty clay loam, 2 to 12 percent slopes | 6K | Well drained | C | Somewhat limited | Very limited |
Soil Orders in This Area
The USDA classifies every soil into one of 12 soil orders. Here are the dominant orders found in this survey area.
What This Means
Building & Foundations
About 84% 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 96% 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.