Rock Island County, Illinois
The most common soil here is Fayette, on about 13% of the land: a silt loam, smooth, like flour. Sylvan and Hickory come next.
About 65% of the land drains well, and 28% stays wet for long stretches; groundwater comes within two feet of the surface under 29% of it.
USDA rates 56% of the land very limited for a standard septic drain field, and 44% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 15% of the land floods occasionally or more, and bedrock lies within 40 inches under 2% of it.
Soils change over short distances, so look up an address below for the soil at that exact spot and the reasons behind each rating.
The soils you're most likely standing on
The biggest named soils in Rock Island County, Illinois, each drawn five feet deep from its official USDA description, in its recorded colors.
Dots mark gravel; white flecks mark lime. Shares are by acres across the survey area, and each mapped patch usually mixes several of these soils.
The biggest mapped areas
The dominant drainage class is Well drained and the dominant hydrologic group is B (moderate infiltration). The most common soil order is Alfisols — moderately leached forest soils with a clay-enriched subsoil. 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 Rock Island County, Illinois. Search your address to find the exact soil composition, drainage, and series details at your specific location.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Fayette silt loam, glaciated, 2 to 5 percent slopes | 28K | Well drained | B | Somewhat limited | Somewhat limited |
| Water | 18K | Not rated | Not rated | ||
| Muscatune silt loam, 0 to 2 percent slopes | 14K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Hickory-Sylvan-Fayette silt loams, 18 to 30 percent slopes | 12K | Well drained | B | Very limited | Very limited |
| Orion silt loam, 0 to 2 percent slopes, frequently flooded | 9K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Sylvan silty clay loam, 10 to 18 percent slopes, severely eroded | 9K | Well drained | B | Somewhat limited | Somewhat limited |
| Hickory-Sylvan silt loams, 35 to 60 percent slopes | 8K | Well drained | B | Very limited | Very limited |
| Orthents, loamy, undulating | 8K | Well drained | C | Not limited | Very limited |
| Sparta loamy sand, Illinois till plain, 0 to 2 percent slopes | 7K | Excessively drained | A | Not limited | Very limited |
| Osco silt loam, 2 to 5 percent slopes | 7K | Well drained | B | Somewhat limited | Somewhat limited |
| Sawmill silty clay loam, 0 to 2 percent slopes, frequently flooded | 7K | Poorly drained | B/D | Very limited | Very limited |
| Coffeen silt loam, 0 to 2 percent slopes, rarely flooded | 6K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Greenbush silt loam, 2 to 5 percent slopes | 6K | Well drained | B | Somewhat limited | Somewhat limited |
| Osco silt loam, 5 to 10 percent slopes, eroded | 5K | Well drained | B | Somewhat limited | Somewhat limited |
| Hickory-Sylvan-Fayette silt loams, 10 to 18 percent slopes, eroded | 5K | Well drained | B | Somewhat limited | Somewhat limited |
| Fluvaquents, loamy, 0 to 2 percent slopes, frequently flooded, long duration | 5K | Poorly drained | B/D | Very limited | Very limited |
| Radford silt loam, 0 to 2 percent slopes, frequently flooded | 5K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Rozetta silt loam, 0 to 2 percent slopes | 5K | Well drained | B | Somewhat limited | Somewhat limited |
| Sylvan silt loam, 18 to 35 percent slopes | 5K | Well drained | B | Very limited | Very limited |
| Lawson silt loam, cool mesic, 0 to 2 percent slopes, frequently flooded | 4K | Somewhat poorly drained | B/D | Very limited | Very limited |
Soil Orders in This Area
The USDA classifies every soil into one of 12 soil orders. Here are the dominant orders found in this survey area.
What This Means
Building & Foundations
About 44% of soils have significant building limitations, while the rest are generally suitable. Check specific sites carefully — conditions vary across the area.
Septic Systems
About 56% 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.