Expansive Soil in Oregon: County Ratings
3 of the 34 rated counties in Oregon have a dominant shrink-swell rating of High or Very High. Each rating below is the NRCS shrink-swell class covering the largest share of the county's mapped soil acres, computed from USDA SSURGO data. Open a county for the full class breakdown and what it means for a slab foundation.
| County | Dominant class | High + Very High share | Survey coverage |
|---|---|---|---|
| Baker County | High | 52% | 99% |
| Benton County | Moderate | 19% | 99% |
| Clackamas County | Low | 5% | 99% |
| Clatsop County | Low | 1% | 92% |
| Columbia County | Low | 6% | 99% |
| Coos County | Low | 8% | 98% |
| Crook County | High | 66% | 99% |
| Curry County | Low | 20% | 99% |
| Deschutes County | Low | 10% | 100% |
| Douglas County | Low | 15% | 98% |
| Gilliam County | Low | 3% | 98% |
| Harney County | Moderate | 38% | 99% |
| Hood River County | Low | 10% | 96% |
| Jackson County | Low | 33% | 99% |
| Jefferson County | Moderate | 31% | 98% |
| Josephine County | Low | 18% | 99% |
| Klamath County | Low | 24% | 91% |
| Lake County | Low | 31% | 97% |
| Lane County | Low | 12% | 97% |
| Lincoln County | Low | 1% | 98% |
| Linn County | Moderate | 24% | 96% |
| Malheur County | Low | 1% | 95% |
| Marion County | Moderate | 20% | 99% |
| Morrow County | Low | 8% | 99% |
| Multnomah County | Low | 0% | 86% |
| Polk County | Moderate | 18% | 99% |
| Sherman County | Low | 0% | 98% |
| Tillamook County | Low | 0% | 98% |
| Umatilla County | Low | 9% | 99% |
| Union County | Moderate | 31% | 100% |
| Wallowa County | High | 39% | 100% |
| Wasco County | Low | 15% | 98% |
| Washington County | Moderate | 6% | 99% |
| Yamhill County | Moderate | 27% | 99% |
How these ratings are computed
Ratings come from USDA NRCS SSURGO soil survey data: for each soil component we take the maximum linear extensibility percent (lep_r) in the top 100 cm, apply the NRCS Handbook Part 618 class limits (Low under 3 percent, Moderate 3 to 6, High 6 to 9, Very High 9 and above), assign map units by plurality of component percent, and roll acres up to the county. Full details on the methodology section of the lookup page. A county rating is not a parcel-level geotechnical assessment.