Soil series profile
Ashkum soil series
Ashkum is a poorly drained soil with a silty clay loam surface, mapped on 592,404 acres in 39 counties across 3 states. Hydrologic group C/D.
- Drainage class
- Poorly drained >99% of mapped acres
- Hydrologic group
- C/D 99% of mapped acres
- Typical topsoil pH
- 7.0 neutral · range 7.0–7.0
- Mapped area
- 592k acres in 39 counties, 3 states
Typical Ashkum profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–12 in (Ap) | Silty clay loam | 7.0 | 37% | 8% | 5% |
| 12–29 in (Bg1) | Silty clay | 6.8 | 41% | 8% | 1.25% |
| 29–54 in (2Bg2) | Silty clay loam | 7.3 | 33% | 9% | 0.3% |
| 54–60 in (2Cg) | Silty clay loam | 7.9 | 30% | 9% | 0.25% |

What this means
What Ashkum soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Ashkum soils is neutral: pH 7.0, the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 99% of mapped Ashkum acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silty clay loam (99% of mapped Ashkum acres).
>99% of mapped Ashkum acres is somewhat poorly to very poorly drained, so soil stays soggy for long spells after rain and in wet seasons. Raised beds, plants that tolerate wet feet, and not working the soil while wet all help.
For lawns and yards
On 99% of mapped acres, rain soaks in slowly (hydrologic groups C and D, including dual groups that are D until drained). Expect runoff and puddles after heavy rain: core-aerate compacted lawns and keep ground sloping away from foundations.
A seasonal high water table comes within 18 inches of the surface on >99% of mapped acres, often in spring. Basements, sump pumps and lawns in low spots feel it first.
For a septic system
For conventional septic absorption fields, NRCS rates 99% of the acres in mapped Ashkum soils very limited, 0% somewhat limited and 0% not limited (1% not rated, such as urban land, pits or water).
Where the soil is very limited (slow permeability, a high water table, flooding, shallow bedrock or steep slopes), alternative systems such as mound or sand-filter designs are common and cost more.
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Ashkum soil is found
Mapped acres
Ashkum is mapped in Illinois, Wisconsin and Indiana.
| County | Acres | Share of county land |
|---|---|---|
| Livingston County, IL | 112,826 | 17.0% |
| Will County, IL | 87,973 | 16.7% |
| Vermilion County, IL | 63,656 | 11.2% |
| Ford County, IL | 45,535 | 14.7% |
| Cook County, IL | 32,989 | 5.5% |
| Champaign County, IL | 29,231 | 4.6% |
| DuPage County, IL | 27,507 | 13.0% |
| McLean County, IL | 25,199 | 3.3% |
| Racine County, WI | 23,985 | 11.3% |
| Grundy County, IL | 21,817 | 8.3% |
| Lake County, IL | 21,186 | 7.6% |
| Kankakee County, IL | 20,567 | 4.8% |
| Kenosha County, WI | 18,598 | 10.8% |
| Iroquois County, IL | 12,258 | 1.7% |
| LaSalle County, IL | 7,643 | 1.1% |
| Milwaukee County, WI | 6,995 | 4.5% |
| Waukesha County, WI | 5,643 | 1.6% |
| Kane County, IL | 5,320 | 1.6% |
| McHenry County, IL | 5,314 | 1.5% |
| Fond du Lac County, WI | 4,417 | 1.0% |
| Lake County, IN | 3,562 | 1.1% |
| Benton County, IN | 3,480 | 1.4% |
| Porter County, IN | 1,671 | 0.6% |
| Kendall County, IL | 1,427 | 0.7% |
| Washington County, WI | 1,095 | 0.4% |
| Ozaukee County, WI | 822 | 0.6% |
| LaPorte County, IN | 411 | 0.1% |
| Warren County, IN | 378 | 0.2% |
| Jasper County, IN | 185 | 0.1% |
| White County, IN | 179 | 0.1% |
| Woodford County, IL | 174 | 0.1% |
| Winnebago County, IL | 121 | 0.0% |
| Ogle County, IL | 52 | 0.0% |
| St. Joseph County, IN | 47 | 0.0% |
| Boone County, IL | 44 | 0.0% |
| Bureau County, IL | 37 | 0.0% |
| Marshall County, IL | 22 | 0.0% |
| Piatt County, IL | 22 | 0.0% |
| Putnam County, IL | 14 | 0.0% |
Septic absorption fields
NRCS rating, share of Ashkum acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 98.8% |
| Not rated | 1.2% |
Drainage, water table and flooding
Share of Ashkum acres
- Depth to seasonal high water table
- About 6 inches (median where reported); within 18 inches on >99% of acres.
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 0–0% (median 0%).
- Topsoil organic matter
- Median 5%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 0.0% |
| Well drained | 0.0% |
| Moderately well drained | 0.0% |
| Somewhat poorly drained | 0.0% |
| Poorly drained | 99.9% |
| Very poorly drained | 0.0% |
| Not rated | 0.1% |
Hydrologic soil group
Show as a table
| Category | Share of acres |
|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.0% |
| B: moderate infiltration | 0.0% |
| C: slow infiltration | 0.0% |
| D: very slow infiltration (clayey, shallow or wet) | 0.0% |
| A/D: D as is, A if drained | 0.0% |
| B/D: D as is, B if drained | 0.0% |
| C/D: D as is, C if drained | 98.8% |
| Not rated | 1.2% |
Sources & data dates
- Source
- USDA NRCS Soil Survey Geographic Database (SSURGO), queried through Soil Data Access. Public domain.
- Data date
- SSURGO as published on November 3, 2026 (most recent survey area update October 26, 2026). NRCS refreshes SSURGO each October.
- Scope
- All map unit components named Ashkum (component kind "Series") in SSURGO: 592,404 acres.
- Method
- Shares are by mapped acres of Ashkum components. The profile comes from the single largest Ashkum component. Full methodology.