Williamson County, Illinois
The dominant drainage class is Moderately well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). 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 Williamson County, Illinois.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Belknap silt loam, 0 to 2 percent slopes, frequently flooded | 29K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Ava silt loam, 2 to 5 percent slopes | 19K | Moderately well drained | C | Very limited | Very limited |
| Water | 15K | Not rated | Not rated | ||
| Plumfield silty clay loam, 5 to 10 percent slopes | 11K | Moderately well drained | D | Somewhat limited | Very limited |
| Ava silt loam, 5 to 10 percent slopes, eroded | 9K | Moderately well drained | C | Very limited | Very limited |
| Ava silty clay loam, 5 to 10 percent slopes, severely eroded | 8K | Moderately well drained | C | Somewhat limited | Very limited |
| Rend silty clay loam, 5 to 10 percent slopes, severely eroded | 8K | Moderately well drained | C | Very limited | Very limited |
| Bonnie silt loam, 0 to 2 percent slopes, frequently flooded | 7K | Poorly drained | C/D | Very limited | Very limited |
| Bluford silt loam, 2 to 5 percent slopes | 7K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Hickory-Kell silt loams, 18 to 35 percent slopes | 7K | Well drained | B | Very limited | Very limited |
| Grantsburg silt loam, 2 to 5 percent slopes | 7K | Moderately well drained | C | Somewhat limited | Very limited |
| Bluford silt loam, bench, 2 to 5 percent slopes | 6K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Hickory clay loam, 10 to 18 percent slopes, severely eroded | 6K | Well drained | B | Somewhat limited | Somewhat limited |
| Plumfield silty clay loam, 10 to 18 percent slopes | 6K | Moderately well drained | D | Somewhat limited | Very limited |
| Rend silt loam, 5 to 10 percent slopes, eroded | 6K | Moderately well drained | C | Very limited | Very limited |
| Sharon silt loam, 0 to 2 percent slopes, frequently flooded | 5K | Moderately well drained | C | Very limited | Very limited |
| Fairpoint gravelly silt loam, 7 to 20 percent slopes | 5K | Well drained | C | Somewhat limited | Very limited |
| Hickory-Kell silt loams, 10 to 18 percent slopes, eroded | 5K | Well drained | B | Somewhat limited | Somewhat limited |
| Hickory-Kell clay loams, 10 to 18 percent slopes, severely eroded | 5K | Well drained | B | Somewhat limited | Somewhat limited |
| Rend silt loam, 2 to 5 percent slopes | 5K | Moderately well drained | C | Very limited | Very limited |
What This Means
Building & Foundations
About 61% 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 82% 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.