What's My Soil

A field guide to the soil under your feet

Soil series profile

Colpien soil series

Colpien is a moderately well drained soil with a loam surface, mapped on 87,516 acres in 4 counties in CA. Hydrologic group C.

#3909 by mapped area fine-loamy Calcic Pachic Haploxerolls (Mollisols)

Drainage class
Moderately well drained
85% of mapped acres
Hydrologic group
C
85% of mapped acres
Typical topsoil pH
7.5
slightly alkaline · range 7.5–7.5
Mapped area
88k
acres in 4 counties, 1 state

Typical Colpien profile

Texture and pH by depth

Typical Colpien soil profile by depth 0 in 20 in 40 in 60 in 0–6 in · Ap · pH 7.5 · 23% clay Loam 6–24 in · Bt · pH 7.5 · 25% clay Loam 24–60 in · Btk · pH 7.5 · 25% clay Loam 60–65 in · C · pH 7.5 · 20% clay Sandy loam
Depth to scale. More strongly shaded layers hold more clay. Horizon names are the soil survey's (A = topsoil, B = subsoil, C = parent material).
Show as a table
Typical Colpien horizons (representative values)
Depth Texture pH Clay Sand Organic matter
0–6 in (Ap) Loam 7.5 23% 40% 2%
6–24 in (Bt) Loam 7.5 25% 39% 2%
24–60 in (Btk) Loam 7.5 25% 39% 1.25%
60–65 in (C) Sandy loam 7.5 20% 65% 0.25%

Representative values from the most extensive Colpien map unit (Colpien loam, 0 to 2 percent slopes, survey area CA659). Other map units of this series vary within the series range.

Hands holding dark garden soil
Stock photo for illustration, not a sample of this soil series. Credit on the Sources & method page.

What this means

What Colpien soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Colpien soils is slightly alkaline: pH 7.5. 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).

Loamy topsoil (loam, silt loam and similar) covers 85% of mapped Colpien acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (85% of mapped Colpien acres).

85% of mapped Colpien acres is moderately well to excessively drained, which suits most garden plants.

For lawns and yards

On 85% 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 85% of the acres in mapped Colpien soils very limited, 0% somewhat limited and 0% not limited (15% 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.

Flooding is mapped on 85% of the acres (0% occasional, 0% frequent).

Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.

Generated from the mapped numbers above using fixed rules, not a site visit. See how these notes are written.

Where Colpien soil is found

Mapped acres

Colpien is mapped in California.

Counties with the most mapped Colpien soil
County Acres Share of county land
Tulare County, CA 84,874 3.4%
Kings County, CA 2,628 0.3%
Fresno County, CA 14 0.0%
Kern County, CA 0 0.0%

Septic absorption fields

NRCS rating, share of Colpien acres

Not limited 0%
Somewhat limited 0%
Very limited 85%
Not rated 15%
Septic tank absorption field rating across mapped Colpien acres. Scale 0 to 100% of mapped land.
Show as a table
Septic tank absorption field rating across mapped Colpien acres.
CategoryShare of acres
Not limited0.0%
Somewhat limited0.0%
Very limited85.4%
Not rated14.6%

Drainage, water table and flooding

Share of Colpien acres

Depth to seasonal high water table
None reported within about 6.5 feet (median where reported).
Flooding
Mapped as flooding on 85% of acres (0% occasional, 0% frequent).
Slope
Typically 1–1% (median 1%).
Topsoil organic matter
Median 2%.

Drainage class

Excessively drained 0%
Somewhat excessively drained 0%
Well drained 0%
Moderately well drained 85%
Somewhat poorly drained 0%
Poorly drained 0%
Very poorly drained 0%
Not rated 15%
Drainage class across mapped Colpien acres. Scale 0 to 100% of mapped land.
Show as a table
Drainage class across mapped Colpien acres.
CategoryShare of acres
Excessively drained0.0%
Somewhat excessively drained0.0%
Well drained0.0%
Moderately well drained85.4%
Somewhat poorly drained0.0%
Poorly drained0.0%
Very poorly drained0.0%
Not rated14.6%

Hydrologic soil group

A: fast infiltration (mostly sandy or gravelly) 0%
B: moderate infiltration 0%
C: slow infiltration 85%
D: very slow infiltration (clayey, shallow or wet) 0%
A/D: D as is, A if drained 0%
B/D: D as is, B if drained 0%
C/D: D as is, C if drained 0%
Not rated 15%
Hydrologic soil group across mapped Colpien acres. Scale 0 to 100% of mapped land.
Show as a table
Hydrologic soil group across mapped Colpien acres.
CategoryShare of acres
A: fast infiltration (mostly sandy or gravelly)0.0%
B: moderate infiltration0.0%
C: slow infiltration85.4%
D: very slow infiltration (clayey, shallow or wet)0.0%
A/D: D as is, A if drained0.0%
B/D: D as is, B if drained0.0%
C/D: D as is, C if drained0.0%
Not rated14.6%

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 Colpien (component kind "Series") in SSURGO: 87,516 acres.
Method
Shares are by mapped acres of Colpien components. The profile comes from the single largest Colpien component. Full methodology.

Independent reference site. No government affiliation or endorsement.

Full narrative description: USDA Official Soil Series Description for Colpien.