Soil series profile

Spanaway soil series

Spanaway is a somewhat excessively drained soil with a gravelly sandy loam surface, mapped on 115,198 acres in 6 counties in WA. Hydrologic group A.

#3138 by mapped area sandy-skeletal Typic Melanoxerands (Andisols)

Drainage class: Somewhat excessively drained
Hydrologic group: A
Typical topsoil pH: 5.6
Mapped area: 115k

Typical Spanaway 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 Spanaway horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–15 in (A)	Gravelly sandy loam	5.4	5%	70%	10%
15–20 in (Bw)	Very gravelly sandy loam	5.8	5%	70%	2%
20–60 in (C)	Extremely gravelly sand	6.1	2%	95%	0.5%

Representative values from the most extensive Spanaway map unit (Spanaway gravelly sandy loam, 0 to 3 percent slopes, survey area WA777). 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 Spanaway soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Spanaway soils is moderately acidic: pH 5.6 (most land between 5.4 and 5.6). Many vegetables grow well here, and some gardens benefit from a little lime. Test before adding any.

Loamy topsoil (loam, silt loam and similar) covers 63% of mapped Spanaway acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is gravelly sandy loam (73% of mapped Spanaway acres).

100% of mapped Spanaway acres is excessively or somewhat excessively drained: water moves through fast, so gardens need more frequent watering in dry spells.

For lawns and yards

100% of mapped acres is in hydrologic group A, where water soaks in fast. Lawns there dry out quickly; deeper, less frequent watering and organic matter help.

For a septic system

For conventional septic absorption fields, NRCS rates 100% of the acres in mapped Spanaway 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 Spanaway soil is found

Mapped acres

Spanaway is mapped in Washington.

Counties with the most mapped Spanaway soil
County	Acres	Share of county land
Pierce County, WA	66,068	6.0%
Thurston County, WA	45,474	9.1%
Lewis County, WA	3,112	0.3%
Grays Harbor County, WA	525	0.1%
Pacific County, WA	10	0.0%
Wahkiakum County, WA	10	0.0%

Septic absorption fields

NRCS rating, share of Spanaway acres

Not limited 0%

Somewhat limited 0%

Very limited 100%

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

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

Drainage, water table and flooding

Share of Spanaway 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 2–9% (median 2%).
Topsoil organic matter: Median 10%.

Drainage class

Excessively drained 0%

Somewhat excessively drained 100%

Well drained 0%

Moderately well drained 0%

Somewhat poorly drained 0%

Poorly drained 0%

Very poorly drained 0%

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

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Drainage class across mapped Spanaway acres.
Category	Share of acres
Excessively drained	0.0%
Somewhat excessively drained	100.0%
Well drained	0.0%
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) 100%

B: moderate infiltration 0%

C: slow infiltration 0%

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%

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

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Hydrologic soil group across mapped Spanaway acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	100.0%
B: moderate infiltration	0.0%
C: slow infiltration	0.0%
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%

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 Spanaway (component kind "Series") in SSURGO: 115,198 acres.
Method: Shares are by mapped acres of Spanaway components. The profile comes from the single largest Spanaway component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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