Polk County, Iowa
The most common soil here is Clarion, on about 19% of the land: a loam, a balanced mix that crumbles in your hand. Webster and Nicollet come next.
About 41% of the land drains well, and 41% stays wet for long stretches; groundwater comes within two feet of the surface under 43% of it.
USDA rates 67% of the land very limited for a standard septic drain field, and 50% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 16% 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 Polk 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 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 Polk 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 | 46K | Well drained | B | Somewhat limited | Somewhat limited |
| Webster clay loam, Bemis moraine, 0 to 2 percent slopes | 32K | Poorly drained | C/D | Very limited | Very limited |
| Nicollet loam, 1 to 3 percent slopes | 30K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Canisteo clay loam, Bemis moraine, 0 to 2 percent slopes | 26K | Poorly drained | C/D | Very limited | Very limited |
| Urban land | 15K | Not rated | Not rated | ||
| Clarion loam, Bemis moraine, 6 to 10 percent slopes, moderately eroded | 13K | Well drained | B | Somewhat limited | Somewhat limited |
| Water | 12K | Not rated | Not rated | ||
| Coland clay loam, 0 to 2 percent slopes, occasionally flooded | 11K | Poorly drained | C/D | Very limited | Very limited |
| Dockery-Quiver silt loams, 0 to 2 percent slopes, occasionally flooded | 10K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Clarion-Urban land complex, 2 to 5 percent slopes | 10K | Well drained | B | Somewhat limited | Somewhat limited |
| Spillville-Coland complex, channeled, 0 to 2 percent slopes | 9K | Moderately well drained | B | Very limited | Very limited |
| Clarion-Urban land complex, 5 to 9 percent slopes | 7K | Well drained | B | Somewhat limited | Somewhat limited |
| Spillville loam, 0 to 2 percent slopes, occasionally flooded | 6K | Somewhat poorly drained | B/D | Very limited | Very limited |
| Colo-Judson silty clay loams, 0 to 5 percent slopes, occasionally flooded | 6K | Poorly drained | C/D | Very limited | Very limited |
| Lester loam, Bemis moraine, 2 to 6 percent slopes | 6K | Well drained | C | Somewhat limited | Very limited |
| Orthents, loamy | 5K | Not rated | Not rated | ||
| Tama silty clay loam, 5 to 9 percent slopes, eroded | 5K | Well drained | C | Somewhat limited | Very limited |
| Hayden loam, Bemis moraine, 22 to 40 percent slopes | 4K | Well drained | C | Very limited | Very limited |
| Coland, occasionally flooded-Terril complex, 2 to 5 percent slopes | 4K | Poorly drained | C/D | Very limited | Very limited |
| Orthents-urban land complex, 0 to 5 percent slopes | 3K | Not rated | Not rated |
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 50% of soils have significant building limitations, while the rest are generally suitable. Check specific sites carefully — conditions vary across the area.
Septic Systems
About 67% 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.