Soil series profile
Egan soil series
Egan is a well drained soil with a silty clay loam surface, mapped on 381,573 acres in 15 counties across 3 states. Hydrologic group C.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- C >99% of mapped acres
- Typical topsoil pH
- 6.7 neutral · range 6.0–6.7
- Mapped area
- 382k acres in 15 counties, 3 states
Typical Egan profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–5 in (Ap) | Silty clay loam | 6.0 | 31% | 9% | 6% |
| 5–29 in (Bw) | Silty clay loam | 6.4 | 32% | 4% | 2% |
| 29–37 in (Bk) | Silt loam | 8.0 | 26% | 9% | 0.5% |
| 37–54 in (2Bk) | Loam | 8.3 | 25% | 39% | 0.25% |
| 54–79 in (2Ck) | Loam | 8.5 | 20% | 51% | 0.25% |
What this means
What Egan soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Egan soils is neutral: pH 6.7 (most land between 6.0 and 6.7), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 100% of mapped Egan acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silty clay loam (>99% of mapped Egan acres).
100% of mapped Egan acres is moderately well to excessively drained, which suits most garden plants.
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.
For a septic system
For conventional septic absorption fields, NRCS rates 100% of the acres in mapped Egan soils very limited, 0% somewhat limited and 0% not limited.
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 Egan soil is found
Mapped acres
Egan is mapped in South Dakota, Iowa and Minnesota.
| County | Acres | Share of county land |
|---|---|---|
| Lake County, SD | 85,872 | 24.0% |
| Turner County, SD | 76,439 | 19.4% |
| Clay County, SD | 50,077 | 18.9% |
| Lincoln County, SD | 49,576 | 13.4% |
| Minnehaha County, SD | 43,752 | 8.5% |
| Moody County, SD | 28,456 | 8.6% |
| Yankton County, SD | 23,305 | 7.0% |
| Lyon County, IA | 6,542 | 1.7% |
| McCook County, SD | 5,053 | 1.4% |
| Hanson County, SD | 3,616 | 0.5% |
| Hutchinson County, SD | 3,616 | 0.5% |
| Union County, SD | 3,253 | 1.1% |
| Miner County, SD | 1,522 | 0.4% |
| Brookings County, SD | 394 | 0.1% |
| Rock County, MN | 99 | 0.0% |
Septic absorption fields
NRCS rating, share of Egan acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 100.0% |
Drainage, water table and flooding
Share of Egan acres
- Depth to seasonal high water table
- None reported within about 6.5 feet (median where reported).
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 1–6% (median 4%).
- Topsoil organic matter
- Median 4.5%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 0.0% |
| Well drained | 100.0% |
| Moderately well drained | 0.0% |
| Somewhat poorly drained | 0.0% |
| Poorly drained | 0.0% |
| Very poorly drained | 0.0% |
Hydrologic soil group
Show as a table
| Category | Share of acres |
|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.0% |
| B: moderate infiltration | 0.4% |
| C: slow infiltration | 99.6% |
| 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 | 0.0% |
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 Egan (component kind "Series") in SSURGO: 381,573 acres.
- Method
- Shares are by mapped acres of Egan components. The profile comes from the single largest Egan component. Full methodology.