What's My Soil

A field guide to the soil under your feet

Soil series profile

Cometa soil series

Cometa is a well drained soil with a sandy loam surface, mapped on 93,668 acres in 9 counties in CA. Hydrologic group D.

#3721 by mapped area fine Typic Palexeralfs (Alfisols)

Drainage class
Well drained
89% of mapped acres
Hydrologic group
D
89% of mapped acres
Typical topsoil pH
6.1
slightly acidic · range 6.1–6.1
Mapped area
94k
acres in 9 counties, 1 state

Typical Cometa profile

Texture and pH by depth

Typical Cometa soil profile by depth 0 in 10 in 20 in 30 in 40 in 50 in 0–17 in · H1 · pH 6.1 · 15% clay Sandy loam 17–27 in · H2 · pH 6.7 · 43% clay Sandy clay 27–60 in · H3 · pH 7.0 · 20% clay Stratified sandy loam to sandy clay 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 Cometa horizons (representative values)
Depth Texture pH Clay Sand Organic matter
0–17 in (H1) Sandy loam 6.1 15% 66% 0.75%
17–27 in (H2) Sandy clay 6.7 43% 50% 0.25%
27–60 in (H3) Stratified sandy loam to sandy clay loam 7.0 20% 61% 0.25%

Representative values from the most extensive Cometa map unit (Cometa sandy loams, 3 to 8 percent slopes, survey area CA651). 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 Cometa soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Cometa soils is slightly acidic: pH 6.1, the range most vegetables, flowers and lawn grasses prefer.

Loamy topsoil (loam, silt loam and similar) covers 97% of mapped Cometa acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is sandy loam (84% of mapped Cometa acres).

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

For lawns and yards

On 97% 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 97% of the acres in mapped Cometa soils very limited, 0% somewhat limited and 0% not limited (3% 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 Cometa soil is found

Mapped acres

Cometa is mapped in California.

Counties with the most mapped Cometa soil
County Acres Share of county land
Madera County, CA 42,381 4.4%
Placer County, CA 24,050 4.3%
Sutter County, CA 8,839 2.3%
Fresno County, CA 7,453 0.2%
San Joaquin County, CA 6,944 0.8%
Stanislaus County, CA 3,373 0.3%
San Benito County, CA 508 0.1%
Merced County, CA 65 0.0%
Tulare County, CA 56 0.0%

Septic absorption fields

NRCS rating, share of Cometa acres

Not limited 0%
Somewhat limited 0%
Very limited 97%
Not rated 3%
Septic tank absorption field rating across mapped Cometa acres. Scale 0 to 100% of mapped land.
Show as a table
Septic tank absorption field rating across mapped Cometa acres.
CategoryShare of acres
Not limited0.0%
Somewhat limited0.0%
Very limited96.8%
Not rated3.2%

Drainage, water table and flooding

Share of Cometa 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 2–7% (median 6%).
Topsoil organic matter
Median 0.8%.

Drainage class

Excessively drained 0%
Somewhat excessively drained 0%
Well drained 89%
Moderately well drained 8%
Somewhat poorly drained 0%
Poorly drained 0%
Very poorly drained 0%
Not rated 3%
Drainage class across mapped Cometa acres. Scale 0 to 100% of mapped land.
Show as a table
Drainage class across mapped Cometa acres.
CategoryShare of acres
Excessively drained0.0%
Somewhat excessively drained0.0%
Well drained89.1%
Moderately well drained7.8%
Somewhat poorly drained0.0%
Poorly drained0.0%
Very poorly drained0.0%
Not rated3.1%

Hydrologic soil group

A: fast infiltration (mostly sandy or gravelly) 0%
B: moderate infiltration 0%
C: slow infiltration 8%
D: very slow infiltration (clayey, shallow or wet) 89%
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 3%
Hydrologic soil group across mapped Cometa acres. Scale 0 to 100% of mapped land.
Show as a table
Hydrologic soil group across mapped Cometa acres.
CategoryShare of acres
A: fast infiltration (mostly sandy or gravelly)0.0%
B: moderate infiltration0.0%
C: slow infiltration8.2%
D: very slow infiltration (clayey, shallow or wet)88.6%
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 rated3.2%

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 Cometa (component kind "Series") in SSURGO: 93,668 acres.
Method
Shares are by mapped acres of Cometa components. The profile comes from the single largest Cometa component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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