Soil series profile

Austin soil series

Austin is a well drained soil with a silty clay surface, mapped on 351,463 acres in 20 counties in TX. Hydrologic group D.

#934 by mapped area fine-silty Udorthentic Haplustolls (Mollisols)

Drainage class
Well drained
100% of mapped acres
Hydrologic group
D
85% of mapped acres
Typical topsoil pH
8.2
moderately alkaline · range 8.2–8.2
Mapped area
351k
acres in 20 counties, 1 state

Typical Austin profile

Texture and pH by depth

Typical Austin soil profile by depth 0 in 10 in 20 in 30 in 40 in 50 in 0–16 in · Ap · pH 8.2 · 45% clay Silty clay 16–22 in · Bw · pH 8.2 · 45% clay Silty clay 22–29 in · Bk · pH 8.2 · 45% clay Silty clay 29–57 in · Cr · pH 8.2 Bedrock
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 Austin horizons (representative values)
Depth Texture pH Clay Sand Organic matter
0–16 in (Ap) Silty clay 8.2 45% 7% 2.5%
16–22 in (Bw) Silty clay 8.2 45% 7% 0.75%
22–29 in (Bk) Silty clay 8.2 45% 7% 0.5%
29–57 in (Cr) Bedrock 8.2 Not reported Not reported Not reported

Representative values from the most extensive Austin map unit (Austin silty clay, 1 to 3 percent slopes, survey area TX139). 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 Austin soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Austin 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).

Clayey topsoil covers 97% of mapped Austin acres. Clay holds water and nutrients but drains slowly and compacts if worked wet: add compost, avoid tilling soggy soil and consider raised beds. The most common surface texture is silty clay (95% of mapped Austin acres).

100% of mapped Austin 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 97% of the acres in mapped Austin 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 Austin soil is found

Mapped acres

Austin is mapped in Texas.

Counties with the most mapped Austin soil
County Acres Share of county land
Collin County, TX 62,776 11.6%
Ellis County, TX 55,597 9.3%
Dallas County, TX 38,368 6.8%
Bell County, TX 37,876 5.6%
Williamson County, TX 34,955 4.9%
Grayson County, TX 26,688 4.5%
Travis County, TX 21,675 3.4%
Bexar County, TX 18,001 2.3%
Hill County, TX 15,577 2.5%
McLennan County, TX 11,221 1.7%
Fannin County, TX 6,470 1.1%
Lamar County, TX 5,811 1.0%
Red River County, TX 5,523 0.8%
Guadalupe County, TX 3,385 0.7%
Falls County, TX 3,070 0.6%
Comal County, TX 1,954 0.5%
Medina County, TX 1,285 0.2%
Delta County, TX 784 0.5%
Denton County, TX 227 0.0%
Hays County, TX 218 0.1%

Septic absorption fields

NRCS rating, share of Austin acres

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

Drainage, water table and flooding

Share of Austin 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 2–4% (median 2%).
Topsoil organic matter
Median 2.5%.

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 Austin acres. Scale 0 to 100% of mapped land.
Show as a table
Drainage class across mapped Austin acres.
CategoryShare of acres
Excessively drained0.0%
Somewhat excessively drained0.0%
Well drained100.0%
Moderately well drained0.0%
Somewhat poorly drained0.0%
Poorly drained0.0%
Very poorly drained0.0%

Hydrologic soil group

A: fast infiltration (mostly sandy or gravelly) 0%
B: moderate infiltration 0%
C: slow infiltration 15%
D: very slow infiltration (clayey, shallow or wet) 85%
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 Austin acres. Scale 0 to 100% of mapped land.
Show as a table
Hydrologic soil group across mapped Austin acres.
CategoryShare of acres
A: fast infiltration (mostly sandy or gravelly)0.0%
B: moderate infiltration0.0%
C: slow infiltration15.4%
D: very slow infiltration (clayey, shallow or wet)84.5%
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 rated0.2%

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 Austin (component kind "Series") in SSURGO: 351,463 acres.
Method
Shares are by mapped acres of Austin components. The profile comes from the single largest Austin component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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