Soil series profile

Mariposa soil series

Mariposa is a well drained soil with a gravelly silt loam surface, mapped on 163,593 acres in 9 counties in CA. Hydrologic group C.

#2245 by mapped area fine-loamy Ruptic-Lithic-Xerochreptic Haploxerults (Ultisols)

Drainage class: Well drained
Hydrologic group: C
Typical topsoil pH: 5.8
Mapped area: 164k

Typical Mariposa 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 Mariposa horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–8 in (H1)	Gravelly silt loam	5.8	15%	30%	2%
8–26 in (H2)	Gravelly silt loam	5.6	28%	23%	0.75%
26–30 in (H3)	Unweathered bedrock	Not reported	Not reported	Not reported	Not reported

Representative values from the most extensive Mariposa map unit (Mariposa very rocky silt loam, 3 to 50 percent slopes, survey area CA624). 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 Mariposa soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Mariposa soils is moderately acidic: pH 5.8 (most land between 5.8 and 6.1). Many vegetables grow well here, and some gardens benefit from a little lime. Test before adding any.

Loamy topsoil (loam, silt loam and similar) covers 91% of mapped Mariposa acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is gravelly loam (54% of mapped Mariposa acres).

97% of mapped Mariposa acres is moderately well to excessively drained, which suits most garden plants.

For lawns and yards

On 91% 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 91% of the acres in mapped Mariposa soils very limited, 0% somewhat limited and 0% not limited (9% 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 Mariposa soil is found

Mapped acres

Mariposa is mapped in California.

Counties with the most mapped Mariposa soil
County	Acres	Share of county land
El Dorado County, CA	69,800	6.8%
Nevada County, CA	34,219	2.5%
Placer County, CA	32,221	5.8%
Amador County, CA	24,282	6.6%
Yuba County, CA	2,700	0.7%
Calaveras County, CA	94	0.0%
Butte County, CA	51	0.0%
Sierra County, CA	26	0.0%
Plumas County, CA	4	0.0%

Septic absorption fields

NRCS rating, share of Mariposa acres

Not limited 0%

Somewhat limited 0%

Very limited 91%

Not rated 9%

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

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Septic tank absorption field rating across mapped Mariposa acres.
Category	Share of acres
Not limited	0.0%
Somewhat limited	0.0%
Very limited	90.6%
Not rated	9.4%

Drainage, water table and flooding

Share of Mariposa 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 18–60% (median 33%).
Topsoil organic matter: Median 2%.

Drainage class

Excessively drained 0%

Somewhat excessively drained 0%

Well drained 97%

Moderately well drained 0%

Somewhat poorly drained 0%

Poorly drained 0%

Very poorly drained 0%

Not rated 3%

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

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Drainage class across mapped Mariposa acres.
Category	Share of acres
Excessively drained	0.0%
Somewhat excessively drained	0.0%
Well drained	96.9%
Moderately well drained	0.0%
Somewhat poorly drained	0.0%
Poorly drained	0.0%
Very poorly drained	0.0%
Not rated	3.1%

Hydrologic soil group

A: fast infiltration (mostly sandy or gravelly) 0%

B: moderate infiltration 0%

C: slow infiltration 88%

D: very slow infiltration (clayey, shallow or wet) 3%

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 9%

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

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Hydrologic soil group across mapped Mariposa acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	0.0%
B: moderate infiltration	0.0%
C: slow infiltration	87.5%
D: very slow infiltration (clayey, shallow or wet)	3.1%
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	9.4%

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 Mariposa (component kind "Series") in SSURGO: 163,593 acres.
Method: Shares are by mapped acres of Mariposa components. The profile comes from the single largest Mariposa component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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