Soil series profile

Ahwahnee soil series

Ahwahnee is a well drained soil with a coarse sandy loam surface, mapped on 146,857 acres in 6 counties in CA. Hydrologic group B.

#2513 by mapped area coarse-loamy Mollic Haploxeralfs (Alfisols)

Drainage class: Well drained
Hydrologic group: B
Typical topsoil pH: 6.1
Mapped area: 147k

Typical Ahwahnee 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 Ahwahnee horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–8 in (H1)	Coarse sandy loam	6.1	13%	68%	1.5%
8–48 in (H2)	Sandy loam	6.1	16%	65%	0.75%
48–60 in (Cr)	Weathered bedrock	Not reported	Not reported	Not reported	Not reported

Representative values from the most extensive Ahwahnee map unit (Ahwahnee and Vista rocky coarse sandy loams, 8 to 30 percent slopes, survey area CA651). 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 Ahwahnee soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Ahwahnee soils is slightly acidic: pH 6.1 (most land between 5.8 and 6.1), the range most vegetables, flowers and lawn grasses prefer.

Loamy topsoil (loam, silt loam and similar) covers 96% of mapped Ahwahnee acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is coarse sandy loam (73% of mapped Ahwahnee acres).

96% of mapped Ahwahnee acres is moderately well to excessively drained, which suits most garden plants.

For lawns and yards

46% 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 96% of the acres in mapped Ahwahnee 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.

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

Where Ahwahnee soil is found

Mapped acres

Ahwahnee is mapped in California.

Counties with the most mapped Ahwahnee soil
County	Acres	Share of county land
Madera County, CA	85,781	8.8%
Mariposa County, CA	21,781	2.5%
Fresno County, CA	20,106	0.4%
Nevada County, CA	11,530	0.9%
El Dorado County, CA	4,429	0.4%
Amador County, CA	3,074	0.8%

Septic absorption fields

NRCS rating, share of Ahwahnee acres

Not limited 0%

Somewhat limited 0%

Very limited 96%

Not rated 4%

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

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Septic tank absorption field rating across mapped Ahwahnee acres.
Category	Share of acres
Not limited	0.0%
Somewhat limited	0.0%
Very limited	96.0%
Not rated	4.0%

Drainage, water table and flooding

Share of Ahwahnee 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 12–50% (median 20%).
Topsoil organic matter: Median 1.5%.

Drainage class

Excessively drained 0%

Somewhat excessively drained 0%

Well drained 96%

Moderately well drained 0%

Somewhat poorly drained 0%

Poorly drained 0%

Very poorly drained 0%

Not rated 4%

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

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Drainage class across mapped Ahwahnee acres.
Category	Share of acres
Excessively drained	0.0%
Somewhat excessively drained	0.0%
Well drained	96.0%
Moderately well drained	0.0%
Somewhat poorly drained	0.0%
Poorly drained	0.0%
Very poorly drained	0.0%
Not rated	4.0%

Hydrologic soil group

A: fast infiltration (mostly sandy or gravelly) 46%

B: moderate infiltration 48%

C: slow infiltration 2%

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 4%

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

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Hydrologic soil group across mapped Ahwahnee acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	46.4%
B: moderate infiltration	47.6%
C: slow infiltration	2.0%
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	4.0%

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 Ahwahnee (component kind "Series") in SSURGO: 146,857 acres.
Method: Shares are by mapped acres of Ahwahnee components. The profile comes from the single largest Ahwahnee component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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