Soil series profile
Tannin soil series
Tannin is a well drained soil with a loam surface, mapped on 75,205 acres in 2 counties in CA. Hydrologic group B.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- B 81% of mapped acres
- Typical topsoil pH
- 6.0 moderately acidic · range 5.8–6.4
- Mapped area
- 75k acres in 2 counties, 1 state
Typical Tannin profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–2 in (Oi) | Slightly decomposed plant material | 6.0 | 15% | 35% | 75% |
| 2–4 in (A1) | Loam | 6.4 | 20% | 42% | 6% |
| 4–8 in (A2) | Loam | 6.2 | 20% | 42% | 4% |
| 8–22 in (Bt1) | Loam | 5.8 | 24% | 39% | 2% |
| 22–28 in (Bt2) | Loam | 5.6 | 24% | 39% | 1% |
| 28–47 in (Bt3) | Clay loam | 5.6 | 28% | 34% | 0.5% |
| 47–63 in (Bt4) | Clay loam | 5.4 | 28% | 34% | 0.5% |
| 63–71 in (Bt5) | Clay loam | 5.2 | 28% | 34% | 0% |
What this means
What Tannin soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Tannin soils is moderately acidic: pH 6.0 (most land between 5.8 and 6.4). Many vegetables grow well here, and some gardens benefit from a little lime. Test before adding any.
Loamy topsoil (loam, silt loam and similar) covers 100% of mapped Tannin acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (87% of mapped Tannin acres).
100% of mapped Tannin acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
Most land is in hydrologic groups B and C, where rain soaks in at a moderate pace.
For a septic system
For conventional septic absorption fields, NRCS rates 100% of the acres in mapped Tannin 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 Tannin soil is found
Mapped acres
Tannin is mapped in California.
| County | Acres | Share of county land |
|---|---|---|
| Humboldt County, CA | 71,249 | 3.5% |
| Mendocino County, CA | 412 | 0.0% |
Septic absorption fields
NRCS rating, share of Tannin 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 Tannin 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 25–63% (median 40%).
- Topsoil organic matter
- Median 6%.
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 | 81.4% |
| C: slow infiltration | 18.6% |
| 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 Tannin (component kind "Series") in SSURGO: 75,205 acres.
- Method
- Shares are by mapped acres of Tannin components. The profile comes from the single largest Tannin component. Full methodology.