Dallas County, Iowa
The most common soil here is Clarion, on about 29% of the land: a loam, a balanced mix that crumbles in your hand. Canisteo and Nicollet come next.
About 43% of the land drains well, and 44% stays wet for long stretches; groundwater comes within two feet of the surface under 46% of it.
USDA rates 66% of the land very limited for a standard septic drain field, and 54% 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.
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 Dallas County, Iowa, 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 Mollisols — grassland soils with a thick, dark, fertile topsoil rich in organic matter. 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 Dallas County, Iowa. 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 |
|---|---|---|---|---|---|
| Clarion loam, Bemis moraine, 2 to 6 percent slopes | 76K | Well drained | B | Somewhat limited | Somewhat limited |
| Canisteo clay loam, Bemis moraine, 0 to 2 percent slopes | 49K | Poorly drained | C/D | Very limited | Very limited |
| Nicollet loam, 1 to 3 percent slopes | 40K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Webster clay loam, Bemis moraine, 0 to 2 percent slopes | 28K | Poorly drained | C/D | Very limited | Very limited |
| Clarion loam, Bemis moraine, 6 to 10 percent slopes, moderately eroded | 23K | Well drained | B | Somewhat limited | Somewhat limited |
| Clarion loam, 2 to 5 percent long slopes | 14K | Well drained | B | Somewhat limited | Somewhat limited |
| Sharpsburg silty clay loam, 5 to 9 percent slopes, eroded | 9K | Moderately well drained | C | Somewhat limited | Very limited |
| Sharpsburg silty clay loam, 2 to 5 percent slopes | 8K | Moderately well drained | C | Somewhat limited | Very limited |
| Coland clay loam, 0 to 2 percent slopes, occasionally flooded | 8K | Poorly drained | C/D | Very limited | Very limited |
| Hayden-Storden loams, 25 to 50 percent slopes | 6K | Well drained | B | Very limited | Very limited |
| Dockery-Quiver silt loams, 0 to 2 percent slopes, occasionally flooded | 5K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Coland-Terril complex, 2 to 5 percent slopes | 5K | Poorly drained | C/D | Very limited | Very limited |
| Hanlon-Spillville complex, channeled, 0 to 2 percent slopes | 5K | Moderately well drained | A | Very limited | Very limited |
| Ladoga silty clay loam, dissected till plain, 5 to 9 percent slopes, eroded | 5K | Moderately well drained | C | Very limited | Very limited |
| Water | 4K | Not rated | Not rated | ||
| Lindley silt loam, 18 to 40 percent slopes | 4K | Well drained | C | Very limited | Very limited |
| Gara-Armstrong complex, 14 to 18 percent slopes | 4K | Somewhat poorly drained | D | Very limited | Very limited |
| Clarion loam, 9 to 14 percent slopes, moderately eroded | 3K | Well drained | B | Somewhat limited | Somewhat limited |
| Lester loam, Bemis moraine, 2 to 6 percent slopes | 3K | Well drained | C | Somewhat limited | Very limited |
| Colo, occasionally flooded-Ely silty clay loams, dissected till plain, 2 to 5 percent slopes | 3K | Poorly drained | C/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 54% 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 66% 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.