Expansive Soil in South Dakota: County Ratings
13 of the 66 rated counties in South Dakota 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 |
|---|---|---|---|
| Aurora County | Moderate | 28% | 99% |
| Beadle County | Moderate | 35% | 99% |
| Bennett County | Low | 12% | 99% |
| Bon Homme County | Low | 18% | 97% |
| Brookings County | Moderate | 6% | 98% |
| Brown County | Moderate | 31% | 99% |
| Brule County | Moderate | 37% | 97% |
| Buffalo County | Moderate | 37% | 97% |
| Butte County | Very High | 78% | 99% |
| Campbell County | Moderate | 15% | 96% |
| Charles Mix County | Moderate | 23% | 95% |
| Clark County | Moderate | 14% | 100% |
| Clay County | Moderate | 21% | 99% |
| Codington County | Moderate | 6% | 96% |
| Corson County | Low | 37% | 97% |
| Custer County | Low | 22% | 100% |
| Davison County | Low | 11% | 99% |
| Day County | Moderate | 16% | 97% |
| Deuel County | Moderate | 10% | 98% |
| Dewey County | Very High | 79% | 93% |
| Douglas County | Moderate | 19% | 100% |
| Edmunds County | Moderate | 25% | 100% |
| Fall River County | Very High | 56% | 99% |
| Faulk County | Moderate | 16% | 100% |
| Grant County | Moderate | 24% | 99% |
| Gregory County | Very High | 69% | 96% |
| Haakon County | High | 89% | 99% |
| Hamlin County | Moderate | 8% | 95% |
| Hand County | Moderate | 23% | 100% |
| Hanson County | Low | 16% | 100% |
| Harding County | Moderate | 11% | 100% |
| Hughes County | Moderate | 36% | 92% |
| Hutchinson County | Low | 16% | 100% |
| Hyde County | Moderate | 42% | 99% |
| Jackson County | Very High | 52% | 100% |
| Jerauld County | Moderate | 30% | 100% |
| Jones County | Very High | 97% | 99% |
| Kingsbury County | Moderate | 27% | 94% |
| Lake County | Moderate | 22% | 98% |
| Lawrence County | Low | 30% | 100% |
| Lincoln County | Moderate | 21% | 100% |
| Lyman County | Very High | 95% | 95% |
| Marshall County | Moderate | 22% | 96% |
| McCook County | Low | 13% | 100% |
| McPherson County | Moderate | 19% | 99% |
| Meade County | Moderate | 51% | 100% |
| Mellette County | Very High | 68% | 99% |
| Miner County | Low | 44% | 100% |
| Minnehaha County | Moderate | 13% | 99% |
| Moody County | Moderate | 5% | 100% |
| Oglala Lakota County | Low | 30% | 100% |
| Pennington County | High | 59% | 100% |
| Perkins County | Moderate | 19% | 99% |
| Potter County | Moderate | 21% | 96% |
| Roberts County | Moderate | 25% | 97% |
| Sanborn County | Low | 19% | 100% |
| Spink County | Moderate | 46% | 99% |
| Stanley County | Very High | 95% | 95% |
| Sully County | Moderate | 20% | 93% |
| Todd County | Low | 12% | 100% |
| Tripp County | Very High | 59% | 100% |
| Turner County | Moderate | 10% | 100% |
| Union County | Moderate | 24% | 99% |
| Walworth County | Moderate | 23% | 94% |
| Yankton County | Low | 13% | 98% |
| Ziebach County | Very High | 59% | 100% |
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.