Expansive Soil in Utah: County Ratings
None of the 28 rated counties in Utah 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 |
|---|---|---|---|
| Beaver County | Low | 16% | 41% * |
| Box Elder County | Low | 5% | 69% * |
| Cache County | Low | 27% | 94% |
| Carbon County | Low | 0% | 98% |
| Daggett County | Low | 3% | 99% |
| Davis County | Low | 14% | 36% * |
| Emery County | Low | 8% | 99% |
| Garfield County | Low | 12% | 89% |
| Grand County | Low | 8% | 96% |
| Iron County | Moderate | 8% | 99% |
| Juab County | Low | 4% | 90% |
| Kane County | Low | 2% | 95% |
| Millard County | Low | 16% | 93% |
| Morgan County | Low | 19% | 97% |
| Piute County | Low | 0% | 100% |
| Rich County | Low | 2% | 95% |
| Salt Lake County | Low | 23% | 78% * |
| San Juan County | Low | 6% | 93% |
| Sanpete County | Low | 20% | 94% |
| Sevier County | Low | 2% | 99% |
| Summit County | Moderate | 8% | 99% |
| Tooele County | Low | 0% | 71% * |
| Uintah County | Low | 13% | 99% |
| Utah County | Low | 9% | 81% |
| Wasatch County | Low | 25% | 95% |
| Washington County | Low | 11% | 63% * |
| Wayne County | Low | 20% | 93% |
| Weber County | Low | 14% | 81% |
* Less than 80% of this county's map acres have completed soil survey data; treat its rating as provisional.
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.