Soil series profile

Somervell soil series

Somervell is a well drained soil with a very gravelly loam surface, mapped on 78,599 acres in 9 counties across 2 states. Hydrologic group C.

#4243 by mapped area loamy-skeletal Typic Calciustolls (Mollisols)

Drainage class: Well drained
Hydrologic group: C
Typical topsoil pH: 8.2
Mapped area: 79k

Typical Somervell 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 Somervell horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–15 in (H1)	Very gravelly loam	8.2	30%	36%	2%
15–27 in (H2)	Very gravelly clay loam	8.2	30%	36%	0.55%
27–35 in (H3)	Bedrock	Not reported	Not reported	Not reported	Not reported

Representative values from the most extensive Somervell map unit (Somervell gravelly loam, 1 to 5 percent slopes, survey area TX121). 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 Somervell soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Somervell soils is moderately alkaline: pH 8.2. Acid-loving plants such as blueberries and azaleas struggle without amended beds, and some trees and shrubs show iron chlorosis (yellow leaves with green veins).

Loamy topsoil (loam, silt loam and similar) covers 98% of mapped Somervell acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is very gravelly loam (64% of mapped Somervell acres).

100% of mapped Somervell 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 Somervell 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 Somervell soil is found

Mapped acres

Somervell is mapped in Texas and Oklahoma.

Counties with the most mapped Somervell soil
County	Acres	Share of county land
Denton County, TX	32,624	5.8%
Wise County, TX	17,992	3.1%
Hill County, TX	9,788	1.6%
Comanche County, OK	8,028	1.2%
Caddo County, OK	4,642	0.6%
Coleman County, TX	2,331	0.3%
Kiowa County, OK	1,816	0.3%
Erath County, TX	1,080	0.2%
Hamilton County, TX	296	0.1%

Septic absorption fields

NRCS rating, share of Somervell acres

Not limited 0%

Somewhat limited 0%

Very limited 98%

Not rated 2%

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

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Septic tank absorption field rating across mapped Somervell acres.
Category	Share of acres
Not limited	0.0%
Somewhat limited	0.0%
Very limited	98.0%
Not rated	2.0%

Drainage, water table and flooding

Share of Somervell 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 3–20% (median 5%).
Topsoil organic matter: Median 2%.

Drainage class

Excessively drained 0%

Somewhat excessively drained 0%

Well drained 100%

Moderately well drained 0%

Somewhat poorly drained 0%

Poorly drained 0%

Very poorly drained 0%

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

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Drainage class across mapped Somervell acres.
Category	Share of acres
Excessively drained	0.0%
Somewhat excessively drained	0.0%
Well drained	100.0%
Moderately well drained	0.0%
Somewhat poorly drained	0.0%
Poorly drained	0.0%
Very poorly drained	0.0%

Hydrologic soil group

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

B: moderate infiltration 0%

C: slow infiltration 98%

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 2%

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

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Hydrologic soil group across mapped Somervell acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	0.0%
B: moderate infiltration	0.0%
C: slow infiltration	98.0%
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	2.0%

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 Somervell (component kind "Series") in SSURGO: 78,599 acres.
Method: Shares are by mapped acres of Somervell components. The profile comes from the single largest Somervell component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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