Soil series profile
Samsil soil series
Samsil is a well drained soil with a clay surface, mapped on 804,995 acres in 29 counties across 5 states. Hydrologic group D.
- Drainage class
- Well drained >99% of mapped acres
- Hydrologic group
- D 94% of mapped acres
- Typical topsoil pH
- 7.7 slightly alkaline · range 7.7–7.9
- Mapped area
- 805k acres in 29 counties, 5 states
Typical Samsil profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–2 in (A) | Clay | 7.7 | 52% | 12% | 1.5% |
| 2–7 in (AC) | Clay | 7.7 | 55% | 8% | 0.7% |
| 7–17 in (C) | Very parachannery clay | 7.9 | 55% | 8% | 0.55% |
| 17–79 in (Cr) | Bedrock | 8.0 | 41% | Not reported | 0.2% |
What this means
What Samsil soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Samsil soils is slightly alkaline: pH 7.7 (most land between 7.7 and 7.9). Acid-loving plants such as blueberries and azaleas struggle without amended beds, and some trees and shrubs show iron chlorosis (yellow leaves with green veins).
Clayey topsoil covers 91% of mapped Samsil acres. Clay holds water and nutrients but drains slowly and compacts if worked wet: add compost, avoid tilling soggy soil and consider raised beds. The most common surface texture is clay (79% of mapped Samsil acres).
>99% of mapped Samsil acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
On 100% 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 >99% of the acres in mapped Samsil 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 Samsil soil is found
Mapped acres
Samsil is mapped in South Dakota, Wyoming, Colorado, Nebraska and Montana.
| County | Acres | Share of county land |
|---|---|---|
| Pennington County, SD | 135,303 | 7.6% |
| Meade County, SD | 113,546 | 5.1% |
| Ziebach County, SD | 91,605 | 7.3% |
| Haakon County, SD | 75,240 | 6.5% |
| Crook County, WY | 73,555 | 4.0% |
| Jackson County, SD | 57,540 | 4.9% |
| Dawes County, NE | 48,860 | 5.5% |
| Fall River County, SD | 46,603 | 4.2% |
| Johnson County, WY | 32,105 | 1.2% |
| Campbell County, WY | 31,975 | 1.0% |
| Oglala Lakota County, SD | 18,832 | 1.3% |
| Huerfano County, CO | 11,671 | 1.1% |
| Arapahoe County, CO | 10,833 | 2.1% |
| Morgan County, CO | 6,579 | 0.8% |
| Sioux County, NE | 4,600 | 0.3% |
| Boulder County, CO | 4,303 | 0.9% |
| Adams County, CO | 3,872 | 0.5% |
| Weston County, WY | 2,779 | 0.2% |
| Butte County, SD | 2,630 | 0.2% |
| Custer County, SD | 2,069 | 0.2% |
| Broomfield County, CO | 1,121 | 3.9% |
| Powder River County, MT | 785 | 0.0% |
| Lawrence County, SD | 460 | 0.1% |
| Sheridan County, NE | 418 | 0.0% |
| Mellette County, SD | 396 | 0.0% |
| Todd County, SD | 135 | 0.0% |
| Denver County, CO | 100 | 0.1% |
| Bennett County, SD | 21 | 0.0% |
| Sheridan County, WY | 8 | 0.0% |
Septic absorption fields
NRCS rating, share of Samsil acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 99.9% |
| Not rated | 0.1% |
Drainage, water table and flooding
Share of Samsil 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 10–28% (median 23%).
- Topsoil organic matter
- Median 1.5%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 0.0% |
| Well drained | 99.9% |
| Moderately well drained | 0.0% |
| Somewhat poorly drained | 0.0% |
| Poorly drained | 0.0% |
| 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 | 5.6% |
| D: very slow infiltration (clayey, shallow or wet) | 94.4% |
| 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% |
| Not rated | 0.1% |
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 Samsil (component kind "Series") in SSURGO: 804,995 acres.
- Method
- Shares are by mapped acres of Samsil components. The profile comes from the single largest Samsil component. Full methodology.