Soil series profile
Millsholm soil series
Millsholm is a well drained soil with a loam surface, mapped on 369,867 acres in 27 counties in CA. Hydrologic group D.
- Drainage class
- Well drained 92% of mapped acres
- Hydrologic group
- D 89% of mapped acres
- Typical topsoil pH
- 6.5 slightly acidic · range 6.0–7.0
- Mapped area
- 370k acres in 27 counties, 1 state
Typical Millsholm profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–2 in (A) | Loam | 7.0 | 21% | 42% | 0.75% |
| 2–8 in (Bw1) | Loam | 7.5 | 21% | 42% | 0.75% |
| 8–14 in (Bw2) | Gravelly sandy clay loam | 7.5 | 23% | 60% | 0.25% |
| 14–24 in (R) | Unweathered bedrock | Not reported | Not reported | Not reported | Not reported |
What this means
What Millsholm soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Millsholm soils is slightly acidic: pH 6.5 (most land between 6.0 and 7.0), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 93% of mapped Millsholm acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (66% of mapped Millsholm acres).
95% of mapped Millsholm acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
On 93% 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 93% of the acres in mapped Millsholm soils very limited, 0% somewhat limited and 0% not limited (7% 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 Millsholm soil is found
Mapped acres
Millsholm is mapped in California.
| County | Acres | Share of county land |
|---|---|---|
| Colusa County, CA | 69,222 | 9.4% |
| Alameda County, CA | 30,692 | 6.5% |
| Lake County, CA | 28,940 | 3.3% |
| Shasta County, CA | 28,043 | 1.6% |
| Monterey County, CA | 26,955 | 1.2% |
| Merced County, CA | 26,581 | 2.1% |
| Yolo County, CA | 26,023 | 4.0% |
| Contra Costa County, CA | 25,790 | 5.6% |
| Tehama County, CA | 17,485 | 0.9% |
| Fresno County, CA | 16,330 | 0.3% |
| Napa County, CA | 14,465 | 3.3% |
| San Luis Obispo County, CA | 13,020 | 0.8% |
| Solano County, CA | 11,404 | 2.2% |
| Kern County, CA | 10,437 | 0.2% |
| Ventura County, CA | 6,822 | 1.1% |
| Stanislaus County, CA | 6,769 | 0.7% |
| Glenn County, CA | 3,904 | 0.5% |
| Kings County, CA | 2,853 | 0.3% |
| Los Angeles County, CA | 1,216 | 0.0% |
| Trinity County, CA | 1,094 | 0.4% |
| Santa Clara County, CA | 963 | 0.1% |
| San Benito County, CA | 367 | 0.0% |
| Santa Barbara County, CA | 84 | 0.0% |
| Mendocino County, CA | 16 | 0.0% |
| Santa Cruz County, CA | 2 | 0.0% |
| Butte County, CA | 0 | 0.0% |
| Yuba County, CA | 0 | 0.0% |
Septic absorption fields
NRCS rating, share of Millsholm acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 93.0% |
| Not rated | 7.0% |
Drainage, water table and flooding
Share of Millsholm 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 22–60% (median 40%).
- Topsoil organic matter
- Median 2%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 2.5% |
| Well drained | 92.0% |
| Moderately well drained | 0.0% |
| Somewhat poorly drained | 0.0% |
| Poorly drained | 0.0% |
| Very poorly drained | 0.0% |
| Not rated | 5.5% |
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 | 3.7% |
| D: very slow infiltration (clayey, shallow or wet) | 89.3% |
| 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 | 7.0% |
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 Millsholm (component kind "Series") in SSURGO: 369,867 acres.
- Method
- Shares are by mapped acres of Millsholm components. The profile comes from the single largest Millsholm component. Full methodology.