Alexander County, Illinois
The dominant drainage class is Well drained and the dominant hydrologic group is B (moderate infiltration). 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 Alexander County, Illinois.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Water | 13K | Not rated | Not rated | ||
| Stookey-Clarksville complex, 18 to 35 percent slopes | 11K | Well drained | B | Very limited | Very limited |
| Darwin silty clay, 0 to 2 percent slopes, occasionally flooded | 6K | Poorly drained | D | Very limited | Very limited |
| Stookey silt loam, 25 to 35 percent slopes | 6K | Well drained | B | Very limited | Very limited |
| Bonnie silt loam, 0 to 2 percent slopes, occasionally flooded | 6K | Poorly drained | C/D | Very limited | Very limited |
| Armiesburg-Sarpy complex, 0 to 2 percent slopes, frequently flooded, long duration | 5K | Well drained | B | Very limited | Very limited |
| Darwin silty clay, 0 to 2 percent slopes, frequently flooded, long duration | 4K | Very poorly drained | D | Very limited | Very limited |
| Elsah silt loam, 1 to 4 percent slopes, occasionally flooded | 4K | Well drained | B | Very limited | Very limited |
| Karnak clay, 0 to 2 percent slopes, occasionally flooded | 4K | Poorly drained | C/D | Very limited | Very limited |
| Riley silty clay loam, 0 to 2 percent slopes, frequently flooded, long duration | 4K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Karnak silty clay, 0 to 2 percent slopes, frequently flooded, long duration | 3K | Very poorly drained | C/D | Very limited | Very limited |
| Ware loam, 1 to 6 percent slopes, frequently flooded, long duration | 3K | Well drained | B | Very limited | Very limited |
| Clarksville-Stookey complex, 35 to 70 percent slopes | 3K | Somewhat excessively drained | B | Very limited | Very limited |
| Haymond silt loam, 0 to 3 percent slopes, occasionally flooded | 3K | Well drained | B | Very limited | Very limited |
| Karnak and Cape silty clays, undrained, 0 to 2 percent slopes, frequently flooded | 3K | Very poorly drained | C/D | Very limited | Very limited |
| Drury silt loam, 10 to 18 percent slopes | 3K | Well drained | B | Somewhat limited | Somewhat limited |
| Cairo silty clay, 0 to 2 percent slopes, occasionally flooded | 3K | Poorly drained | D | Very limited | Very limited |
| Wakeland silt loam, 0 to 2 percent slopes, occasionally flooded | 3K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Darwin and Jacob silty clays, undrained, 0 to 2 percent slopes, frequently flooded | 3K | Very poorly drained | D | Very limited | Very limited |
| Menfro silt loam, 10 to 18 percent slopes | 3K | Well drained | B | Somewhat limited | Somewhat limited |
What This Means
Building & Foundations
About 79% 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 79% 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.