Winnebago County, Illinois
The most common soil here is Griswold, on about 7% of the land: a loam, a balanced mix that crumbles in your hand. Osco and Comfrey come next.
About 72% of the land drains well, and 24% stays wet for long stretches; groundwater comes within two feet of the surface under 23% of it.
USDA rates 69% of the land very limited for a standard septic drain field, and 33% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 9% of the land floods occasionally or more, and bedrock lies within 40 inches under 8% 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 Winnebago 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 Winnebago 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 |
|---|---|---|---|---|---|
| Griswold loam, 6 to 12 percent slopes, eroded | 22K | Well drained | B | Somewhat limited | Very limited |
| Comfrey loam, 0 to 2 percent slopes, frequently flooded | 15K | Poorly drained | B/D | Very limited | Very limited |
| Osco silt loam, 2 to 5 percent slopes | 15K | Well drained | B | Somewhat limited | Somewhat limited |
| Ogle silt loam, 2 to 5 percent slopes | 13K | Well drained | B | Somewhat limited | Somewhat limited |
| Greenbush silt loam, 2 to 5 percent slopes | 9K | Well drained | B | Somewhat limited | Somewhat limited |
| Winnebago silt loam, 2 to 5 percent slopes | 9K | Well drained | B | Somewhat limited | Somewhat limited |
| Plano silt loam, 2 to 5 percent slopes | 9K | Well drained | B | Somewhat limited | Very limited |
| Flagler sandy loam, 0 to 2 percent slopes | 9K | Somewhat excessively drained | A | Not limited | Very limited |
| Jasper silt loam, 2 to 5 percent slopes | 7K | Well drained | B | Somewhat limited | Very limited |
| Selmass loam, 0 to 2 percent slopes | 7K | Poorly drained | B/D | Very limited | Very limited |
| Warsaw loam, 0 to 2 percent slopes | 7K | Well drained | B | Not limited | Very limited |
| Hononegah loamy coarse sand, 0 to 2 percent slopes | 6K | Excessively drained | A | Not limited | Very limited |
| Kidder loam, 6 to 12 percent slopes, eroded | 6K | Well drained | B | Somewhat limited | Very limited |
| Water | 5K | Not rated | Not rated | ||
| Lahoguess loam, 0 to 2 percent slopes | 5K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Rockton and Dodgeville soils, 5 to 10 percent slopes, eroded | 5K | Well drained | C | Very limited | Very limited |
| Griswold loam, 2 to 4 percent slopes | 5K | Well drained | B | Not limited | Very limited |
| Drummer silty clay loam, 0 to 2 percent slopes | 5K | Poorly drained | B/D | Very limited | Very limited |
| Jasper silt loam, 0 to 2 percent slopes | 5K | Well drained | B | Not limited | Very limited |
| Lawson silt loam, cool mesic, 0 to 2 percent slopes, occasionally 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 33% of soils have significant building limitations, while the rest are generally suitable. Check specific sites carefully — conditions vary across the area.
Septic Systems
About 69% 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
Drainage is generally favorable for gardening. Adding compost and mulch will improve fertility and water retention. Test your soil's pH before planting — most vegetables prefer 6.0-7.0.