Soil series profile
Whatcom soil series
Whatcom is a moderately well drained soil with a ashy silt loam surface, mapped on 31,845 acres in 1 county in WA. Hydrologic group C.
- Drainage class
- Moderately well drained 100% of mapped acres
- Hydrologic group
- C 96% of mapped acres
- Typical topsoil pH
- 6.1 slightly acidic · range 6.1–6.1
- Mapped area
- 32k acres in 1 county, 1 state
Typical Whatcom profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–9 in (H1) | Ashy silt loam | 6.1 | 15% | 30% | 6% |
| 9–16 in (H2) | Ashy silt loam | 6.1 | 20% | 27% | 2% |
| 16–26 in (H3) | Loam | 6.5 | 27% | 38% | 0.75% |
| 26–60 in (H4) | Loam | 7.2 | 27% | 38% | 0.25% |
What this means
What Whatcom soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Whatcom soils is slightly acidic: pH 6.1, the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 96% of mapped Whatcom acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is ashy silt loam (96% of mapped Whatcom acres).
100% of mapped Whatcom acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
On 96% 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 96% of the acres in mapped Whatcom soils very limited, 0% somewhat limited and 0% not limited (4% 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 Whatcom soil is found
Mapped acres
Whatcom is mapped in Washington.
| County | Acres | Share of county land |
|---|---|---|
| Whatcom County, WA | 31,845 | 3.0% |
Septic absorption fields
NRCS rating, share of Whatcom acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 96.1% |
| Not rated | 3.9% |
Drainage, water table and flooding
Share of Whatcom acres
- Depth to seasonal high water table
- About 2.2 feet (26 in) (median where reported).
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 2–12% (median 6%).
- 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 | 0.0% |
| Moderately well drained | 100.0% |
| 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 | 0.0% |
| C: slow infiltration | 96.1% |
| 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% |
| Not rated | 3.9% |
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 Whatcom (component kind "Series") in SSURGO: 31,845 acres.
- Method
- Shares are by mapped acres of Whatcom components. The profile comes from the single largest Whatcom component. Full methodology.