Soil series profile

Arnold soil series

Arnold is a somewhat excessively drained soil with a sand surface, mapped on 90,620 acres in 8 counties in CA. Hydrologic group A.

#3806 by mapped area Typic Xeropsamments (Entisols)

Drainage class: Somewhat excessively drained
Hydrologic group: A
Typical topsoil pH: 6.2
Mapped area: 91k

Typical Arnold profile

Texture and pH by depth

Depth to scale. More strongly shaded layers hold more clay. Horizon names are the soil survey's (A = topsoil, B = subsoil, C = parent material).

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Typical Arnold horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–23 in (H1)	Sand	5.6	3%	96%	0.75%
23–55 in (H2)	Sand	5.6	5%	94%	0.25%
55–59 in (H3)	Weathered bedrock	Not reported	Not reported	Not reported	Not reported

Representative values from the most extensive Arnold map unit (Arnold sand, 15 to 45 percent slopes, survey area CA672). Other map units of this series vary within the series range.

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

What this means

What Arnold soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Arnold soils is slightly acidic: pH 6.2 (most land between 5.6 and 6.4), the range most vegetables, flowers and lawn grasses prefer.

Sandy topsoil covers 89% of mapped Arnold acres. It drains fast and warms early in spring, but dries out and loses nutrients quickly: mulch, compost and steady watering help. The most common surface texture is sand (41% of mapped Arnold acres).

91% of mapped Arnold acres is excessively or somewhat excessively drained: water moves through fast, so gardens need more frequent watering in dry spells.

For lawns and yards

89% of mapped acres is in hydrologic group A, where water soaks in fast. Lawns there dry out quickly; deeper, less frequent watering and organic matter help.

For a septic system

For conventional septic absorption fields, NRCS rates 89% of the acres in mapped Arnold soils very limited, 0% somewhat limited and 0% not limited (11% 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.

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

Where Arnold soil is found

Mapped acres

Arnold is mapped in California.

Counties with the most mapped Arnold soil
County	Acres	Share of county land
Monterey County, CA	36,613	1.7%
Santa Barbara County, CA	35,072	3.1%
San Luis Obispo County, CA	8,994	0.6%
Ventura County, CA	6,636	1.0%
San Benito County, CA	2,216	0.2%
Los Angeles County, CA	23	0.0%
Santa Cruz County, CA	9	0.0%
Contra Costa County, CA	1	0.0%

Septic absorption fields

NRCS rating, share of Arnold acres

Not limited 0%

Somewhat limited 0%

Very limited 89%

Not rated 11%

Septic tank absorption field rating across mapped Arnold acres. Scale 0 to 100% of mapped land.

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Septic tank absorption field rating across mapped Arnold acres.
Category	Share of acres
Not limited	0.0%
Somewhat limited	0.0%
Very limited	88.6%
Not rated	11.4%

Drainage, water table and flooding

Share of Arnold 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 15–40% (median 30%).
Topsoil organic matter: Median 0.8%.

Drainage class

Excessively drained 0%

Somewhat excessively drained 91%

Well drained 0%

Moderately well drained 0%

Somewhat poorly drained 0%

Poorly drained 0%

Very poorly drained 0%

Not rated 9%

Drainage class across mapped Arnold acres. Scale 0 to 100% of mapped land.

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Drainage class across mapped Arnold acres.
Category	Share of acres
Excessively drained	0.0%
Somewhat excessively drained	90.7%
Well drained	0.0%
Moderately well drained	0.0%
Somewhat poorly drained	0.0%
Poorly drained	0.0%
Very poorly drained	0.0%
Not rated	9.3%

Hydrologic soil group

A: fast infiltration (mostly sandy or gravelly) 89%

B: moderate infiltration 0%

C: slow infiltration 0%

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 11%

Hydrologic soil group across mapped Arnold acres. Scale 0 to 100% of mapped land.

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Hydrologic soil group across mapped Arnold acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	88.6%
B: moderate infiltration	0.0%
C: slow infiltration	0.0%
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	11.4%

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 Arnold (component kind "Series") in SSURGO: 90,620 acres.
Method: Shares are by mapped acres of Arnold components. The profile comes from the single largest Arnold component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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