Soil series profile

Edgway soil series

Edgway is a well drained soil with a very gravelly ashy loam surface, mapped on 113,924 acres in 7 counties across 3 states. Hydrologic group B.

#3166 by mapped area loamy-skeletal Vitrandic Argicryolls (Mollisols)

Drainage class: Well drained
Hydrologic group: B
Typical topsoil pH: 6.1
Mapped area: 114k

Typical Edgway 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 Edgway horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–1 in (Oi)	Slightly decomposed plant material	6.5	15%	35%	75%
1–11 in (A)	Very gravelly ashy loam	6.7	20%	42%	8.5%
11–16 in (E)	Very gravelly loam	6.7	20%	42%	5%
16–43 in (Bt)	Very gravelly clay loam	6.7	29%	34%	4.5%
43–60 in (BC)	Very cobbly loam	6.7	21%	42%	3%

Representative values from the most extensive Edgway map unit (Edgway very gravelly loam, 15 to 40 percent slopes, survey area ID758). 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 Edgway soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Edgway soils is slightly acidic: pH 6.1 (most land between 6.1 and 6.7), the range most vegetables, flowers and lawn grasses prefer.

Loamy topsoil (loam, silt loam and similar) covers >99% of mapped Edgway acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is ashy silt loam (54% of mapped Edgway acres).

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

For lawns and yards

Most land is in hydrologic groups B and C, where rain soaks in at a moderate pace.

For a septic system

For conventional septic absorption fields, NRCS rates >99% of the acres in mapped Edgway 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 Edgway soil is found

Mapped acres

Edgway is mapped in Idaho, Wyoming and Montana.

Counties with the most mapped Edgway soil
County	Acres	Share of county land
Clark County, ID	42,371	3.8%
Bonneville County, ID	33,079	3.0%
Fremont County, ID	17,162	1.6%
Teton County, WY	10,359	0.4%
Teton County, ID	10,234	3.9%
Madison County, ID	701	0.2%
Beaverhead County, MT	18	0.0%

Septic absorption fields

NRCS rating, share of Edgway acres

Not limited 0%

Somewhat limited 0%

Very limited >99%

Not rated <1%

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

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Septic tank absorption field rating across mapped Edgway acres.
Category	Share of acres
Not limited	0.0%
Somewhat limited	0.0%
Very limited	99.9%
Not rated	0.1%

Drainage, water table and flooding

Share of Edgway 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 25–33% (median 28%).
Topsoil organic matter: Median 5.5%.

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

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Drainage class across mapped Edgway acres.
Category	Share of acres
Excessively drained	0.0%
Somewhat excessively drained	0.0%
Well drained	99.9%
Moderately well drained	0.0%
Somewhat poorly drained	0.0%
Poorly drained	0.0%
Very poorly drained	0.0%
Not rated	0.1%

Hydrologic soil group

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

B: moderate infiltration 54%

C: slow infiltration 46%

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 <1%

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

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Hydrologic soil group across mapped Edgway acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	0.0%
B: moderate infiltration	54.3%
C: slow infiltration	45.6%
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	0.1%

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 Edgway (component kind "Series") in SSURGO: 113,924 acres.
Method: Shares are by mapped acres of Edgway components. The profile comes from the single largest Edgway component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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