Soil series profile

Stewval soil series

Stewval is a well drained soil with a very gravelly fine sandy loam surface, mapped on 724,773 acres in 7 counties across 2 states. Hydrologic group D.

#320 by mapped area loamy-skeletal Lithic Xeric Haplargids (Aridisols)

Drainage class: Well drained
Hydrologic group: D
Typical topsoil pH: 7.7
Mapped area: 725k

Typical Stewval 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 Stewval horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–1 in (A)	Very gravelly fine sandy loam	7.7	15%	69%	1.25%
1–4 in (Bt)	Extremely gravelly loam	7.7	26%	38%	0.75%
4–14 in (R)	Bedrock	Not reported	Not reported	Not reported	Not reported

Representative values from the most extensive Stewval map unit (Stewval-Bellehelen-Rock outcrop association, survey area NV783). 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 Stewval soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Stewval soils is slightly alkaline: pH 7.7 (most land between 7.7 and 7.9). 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 100% of mapped Stewval acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is very gravelly fine sandy loam (73% of mapped Stewval acres).

100% of mapped Stewval acres is moderately well to excessively drained, which suits most garden plants.

For lawns and yards

On 100% 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 100% of the acres in mapped Stewval 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 Stewval soil is found

Mapped acres

Stewval is mapped in Nevada and California.

Counties with the most mapped Stewval soil
County	Acres	Share of county land
Nye County, NV	458,163	5.1%
Mineral County, NV	105,014	4.4%
Esmeralda County, NV	66,885	3.0%
Lincoln County, NV	65,545	1.1%
White Pine County, NV	16,826	0.3%
Elko County, NV	6,632	0.1%
Churchill County, NV	5,513	0.2%

Septic absorption fields

NRCS rating, share of Stewval acres

Not limited 0%

Somewhat limited 0%

Very limited 100%

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

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Septic tank absorption field rating across mapped Stewval acres.
Category	Share of acres
Not limited	0.0%
Somewhat limited	0.0%
Very limited	100.0%

Drainage, water table and flooding

Share of Stewval 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 15–33% (median 18%).
Topsoil organic matter: Median 1.2%.

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 Stewval acres. Scale 0 to 100% of mapped land.

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Drainage class across mapped Stewval 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 0%

D: very slow infiltration (clayey, shallow or wet) 100%

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%

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

Show as a table

Hydrologic soil group across mapped Stewval 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)	100.0%
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%

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 Stewval (component kind "Series") in SSURGO: 724,773 acres.
Method: Shares are by mapped acres of Stewval components. The profile comes from the single largest Stewval component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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