Soil series profile

Tappan soil series

Tappan is a poorly drained soil with a loam surface, mapped on 263,413 acres in 11 counties in MI. Hydrologic group B/D.

#1318 by mapped area fine-loamy Typic Epiaquolls (Mollisols)

Drainage class: Poorly drained
Hydrologic group: B/D
Typical topsoil pH: 7.5
Mapped area: 263k

Typical Tappan 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 Tappan horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–11 in (Ap)	Loam	7.5	22%	48%	5.08%
11–22 in (Bg)	Loam	7.8	24%	40%	0.86%
22–43 in (Cg)	Loam	7.9	21%	40%	0.59%
43–79 in (Cd)	Loam	8.0	21%	40%	0.4%

Representative values from the most extensive Tappan map unit (Tappan loam, 0 to 1 percent slopes, survey area MI017). 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 Tappan soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Tappan soils is slightly alkaline: pH 7.5 (most land between 7.5 and 7.6). 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 Tappan acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (97% of mapped Tappan acres).

100% of mapped Tappan acres is somewhat poorly to very poorly drained, so soil stays soggy for long spells after rain and in wet seasons. Raised beds, plants that tolerate wet feet, and not working the soil while wet all help.

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.

A seasonal high water table comes within 18 inches of the surface on >99% of mapped acres, often in spring. Basements, sump pumps and lawns in low spots feel it first.

For a septic system

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

Mapped acres

Tappan is mapped in Michigan.

Counties with the most mapped Tappan soil
County	Acres	Share of county land
Bay County, MI	95,374	33.4%
Tuscola County, MI	89,301	17.2%
Saginaw County, MI	52,615	10.2%
Huron County, MI	20,075	3.8%
Sanilac County, MI	3,303	0.5%
Arenac County, MI	1,168	0.5%
Midland County, MI	922	0.3%
Gladwin County, MI	332	0.1%
St. Clair County, MI	320	0.1%
Genesee County, MI	4	0.0%
Gratiot County, MI	0	0.0%

Septic absorption fields

NRCS rating, share of Tappan acres

Not limited 0%

Somewhat limited 0%

Very limited 100%

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

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

Drainage, water table and flooding

Share of Tappan acres

Depth to seasonal high water table: About 0 inches (median where reported); within 18 inches on >99% of acres.
Flooding: Not mapped as flooding on most acres.
Slope: Typically 0–0% (median 0%).
Topsoil organic matter: Median 5.1%.

Drainage class

Excessively drained 0%

Somewhat excessively drained 0%

Well drained 0%

Moderately well drained 0%

Somewhat poorly drained 0%

Poorly drained 100%

Very poorly drained 0%

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

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Drainage class across mapped Tappan acres.
Category	Share of acres
Excessively drained	0.0%
Somewhat excessively drained	0.0%
Well drained	0.0%
Moderately well drained	0.0%
Somewhat poorly drained	0.0%
Poorly drained	100.0%
Very poorly drained	0.0%

Hydrologic soil group

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

B: moderate infiltration 0%

C: slow infiltration <1%

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 88%

C/D: D as is, C if drained 12%

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

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Hydrologic soil group across mapped Tappan acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	0.0%
B: moderate infiltration	0.0%
C: slow infiltration	0.1%
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	88.0%
C/D: D as is, C if drained	11.9%

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 Tappan (component kind "Series") in SSURGO: 263,413 acres.
Method: Shares are by mapped acres of Tappan components. The profile comes from the single largest Tappan component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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