Soil series profile

Oplin soil series

Oplin is a well drained soil with a very gravelly clay loam surface, mapped on 341,964 acres in 10 counties in TX. Hydrologic group D.

#964 by mapped area loamy-skeletal Lithic Calciustolls (Mollisols)

Drainage class: Well drained
Hydrologic group: D
Typical topsoil pH: 8.2
Mapped area: 342k

Typical Oplin 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 Oplin horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–12 in (H1)	Very gravelly clay loam	8.2	28%	34%	6%
12–18 in (H2)	Bedrock	Not reported	Not reported	Not reported	Not reported

Representative values from the most extensive Oplin map unit (Oplin very gravelly clay loam, 1 to 8 percent slopes, survey area TX353). 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 Oplin soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Oplin 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 >99% of mapped Oplin acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is very gravelly clay loam (44% of mapped Oplin acres).

>99% of mapped Oplin acres is moderately well to excessively drained, which suits most garden plants.

For lawns and yards

On >99% 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 >99% of the acres in mapped Oplin soils very limited, 0% somewhat limited and 0% not limited.

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 Oplin soil is found

Mapped acres

Oplin is mapped in Texas.

Counties with the most mapped Oplin soil
County	Acres	Share of county land
Nolan County, TX	149,420	25.5%
Taylor County, TX	64,896	11.1%
Edwards County, TX	57,984	4.3%
Concho County, TX	34,211	5.5%
Coke County, TX	15,416	2.7%
Callahan County, TX	6,273	1.1%
Real County, TX	5,870	1.3%
Llano County, TX	5,036	0.8%
San Saba County, TX	1,438	0.2%
Mason County, TX	1,419	0.2%

Septic absorption fields

NRCS rating, share of Oplin acres

Not limited 0%

Somewhat limited 0%

Very limited >99%

Not rated <1%

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

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Septic tank absorption field rating across mapped Oplin acres.
Category	Share of acres
Not limited	0.0%
Somewhat limited	0.0%
Very limited	99.6%
Not rated	0.4%

Drainage, water table and flooding

Share of Oplin 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 5–30% (median 5%).
Topsoil organic matter: Median 6%.

Drainage class

Excessively drained 0%

Somewhat excessively drained 0%

Well drained >99%

Moderately well drained 0%

Somewhat poorly drained 0%

Poorly drained 0%

Very poorly drained 0%

Not rated <1%

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

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Drainage class across mapped Oplin acres.
Category	Share of acres
Excessively drained	0.0%
Somewhat excessively drained	0.0%
Well drained	99.6%
Moderately well drained	0.0%
Somewhat poorly drained	0.0%
Poorly drained	0.0%
Very poorly drained	0.0%
Not rated	0.4%

Hydrologic soil group

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

B: moderate infiltration 0%

C: slow infiltration 0%

D: very slow infiltration (clayey, shallow or wet) >99%

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 <1%

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

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Hydrologic soil group across mapped Oplin acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	0.0%
B: moderate infiltration	0.0%
C: slow infiltration	0.0%
D: very slow infiltration (clayey, shallow or wet)	99.6%
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	0.4%

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 Oplin (component kind "Series") in SSURGO: 341,964 acres.
Method: Shares are by mapped acres of Oplin components. The profile comes from the single largest Oplin component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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