Soil series profile

Vallecitos soil series

Vallecitos is a well drained soil with a loam surface, mapped on 227,368 acres in 8 counties in CA. Hydrologic group D.

#1549 by mapped area clayey Lithic Ruptic-Inceptic Haploxeralfs (Alfisols)

Drainage class: Well drained
Hydrologic group: D
Typical topsoil pH: 6.3
Mapped area: 227k

Typical Vallecitos 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 Vallecitos horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–2 in (A1)	Loam	6.5	21%	42%	1.5%
2–10 in (A2)	Loam	6.0	21%	42%	1.5%
10–16 in (Bt1)	Clay	6.0	43%	28%	0.75%
16–19 in (Bt2)	Clay	6.0	43%	28%	0.75%
19–23 in (R)	Bedrock	Not reported	Not reported	Not reported	Not reported

Representative values from the most extensive Vallecitos map unit (Vallecitos rocky loam, 15 to 30 percent slopes, eroded, survey area CA646). 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 Vallecitos soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Vallecitos soils is slightly acidic: pH 6.3 (most land between 6.3 and 6.5), the range most vegetables, flowers and lawn grasses prefer.

Loamy topsoil (loam, silt loam and similar) covers 98% of mapped Vallecitos acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (80% of mapped Vallecitos acres).

98% of mapped Vallecitos acres is moderately well to excessively drained, which suits most garden plants.

For lawns and yards

On 98% 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 98% of the acres in mapped Vallecitos soils very limited, 0% somewhat limited and 0% not limited (2% 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 Vallecitos soil is found

Mapped acres

Vallecitos is mapped in California.

Counties with the most mapped Vallecitos soil
County	Acres	Share of county land
Santa Clara County, CA	92,574	11.0%
San Benito County, CA	61,852	7.0%
Alameda County, CA	43,993	9.3%
Stanislaus County, CA	14,417	1.5%
San Joaquin County, CA	5,429	0.6%
Riverside County, CA	5,134	0.2%
Contra Costa County, CA	3,795	0.8%
Fresno County, CA	176	0.0%

Septic absorption fields

NRCS rating, share of Vallecitos acres

Not limited 0%

Somewhat limited 0%

Very limited 98%

Not rated 2%

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

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Septic tank absorption field rating across mapped Vallecitos acres.
Category	Share of acres
Not limited	0.0%
Somewhat limited	0.0%
Very limited	97.6%
Not rated	2.4%

Drainage, water table and flooding

Share of Vallecitos 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 23–50% (median 40%).
Topsoil organic matter: Median 1.5%.

Drainage class

Excessively drained 0%

Somewhat excessively drained 0%

Well drained 98%

Moderately well drained 0%

Somewhat poorly drained 0%

Poorly drained 0%

Very poorly drained 0%

Not rated 2%

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

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Drainage class across mapped Vallecitos acres.
Category	Share of acres
Excessively drained	0.0%
Somewhat excessively drained	0.0%
Well drained	97.8%
Moderately well drained	0.0%
Somewhat poorly drained	0.0%
Poorly drained	0.0%
Very poorly drained	0.0%
Not rated	2.2%

Hydrologic soil group

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

B: moderate infiltration 0%

C: slow infiltration <1%

D: very slow infiltration (clayey, shallow or wet) 97%

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 2%

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

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Hydrologic soil group across mapped Vallecitos acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	0.0%
B: moderate infiltration	0.0%
C: slow infiltration	0.6%
D: very slow infiltration (clayey, shallow or wet)	96.9%
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	2.4%

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 Vallecitos (component kind "Series") in SSURGO: 227,368 acres.
Method: Shares are by mapped acres of Vallecitos components. The profile comes from the single largest Vallecitos component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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