Soil series profile

Elloam soil series

Elloam is a well drained soil with a loam surface, mapped on 883,401 acres in 14 counties in MT. Hydrologic group D.

#225 by mapped area fine Aridic Natrustalfs (Alfisols)

Drainage class: Well drained
Hydrologic group: D
Typical topsoil pH: 6.7
Mapped area: 883k

Typical Elloam 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 Elloam horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–3 in (E)	Loam	6.7	24%	39%	1.5%
3–6 in (Btn)	Clay	7.7	41%	29%	1%
6–10 in (Btkn)	Clay loam	8.3	39%	30%	1%
10–28 in (Bknz)	Clay loam	8.2	36%	33%	0.75%
28–43 in (BCyz)	Clay loam	8.0	33%	34%	0.5%
43–79 in (Cz)	Clay loam	7.8	33%	34%	0.5%

Representative values from the most extensive Elloam map unit (Phillips-Elloam complex, 0 to 4 percent slopes, survey area MT608). 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 Elloam soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Elloam soils is neutral: pH 6.7 (most land between 6.7 and 7.0), the range most vegetables, flowers and lawn grasses prefer.

Loamy topsoil (loam, silt loam and similar) covers 91% of mapped Elloam acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (74% of mapped Elloam acres).

100% of mapped Elloam 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 18% of the acres in mapped Elloam soils very limited, 0% somewhat limited and 82% not limited.

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 Elloam soil is found

Mapped acres

Elloam is mapped in Montana.

Counties with the most mapped Elloam soil
County	Acres	Share of county land
Phillips County, MT	369,641	9.9%
Valley County, MT	212,639	6.6%
Blaine County, MT	155,255	5.7%
Hill County, MT	65,835	3.6%
Chouteau County, MT	29,793	1.2%
Liberty County, MT	22,870	2.5%
Toole County, MT	11,133	1.0%
Pondera County, MT	6,730	0.6%
Teton County, MT	4,507	0.3%
Roosevelt County, MT	4,264	0.3%
Cascade County, MT	299	0.0%
Glacier County, MT	271	0.0%
McCone County, MT	158	0.0%
Garfield County, MT	4	0.0%

Septic absorption fields

NRCS rating, share of Elloam acres

Not limited 82%

Somewhat limited 0%

Very limited 18%

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

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Septic tank absorption field rating across mapped Elloam acres.
Category	Share of acres
Not limited	82.4%
Somewhat limited	0.0%
Very limited	17.6%

Drainage, water table and flooding

Share of Elloam 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 2–6% (median 2%).
Topsoil organic matter: Median 1.5%.

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

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

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Hydrologic soil group across mapped Elloam 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 Elloam (component kind "Series") in SSURGO: 883,401 acres.
Method: Shares are by mapped acres of Elloam components. The profile comes from the single largest Elloam component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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