Soil series profile

Waiakoa soil series

Waiakoa is a well drained soil with a extremely stony silty clay loam surface, mapped on 21,628 acres in 1 county in HI. Hydrologic group C.

#9977 by mapped area fine Torroxic Haplustolls (Mollisols)

Drainage class: Well drained
Hydrologic group: C
Typical topsoil pH: 7.0
Mapped area: 22k

Typical Waiakoa 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 Waiakoa horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–1 in (A)	Extremely stony silty clay loam	7.0	38%	19%	2%
1–8 in (Bw1)	Silty clay loam	6.4	38%	19%	1.5%
8–16 in (Bw2)	Silty clay loam	6.4	38%	19%	1.5%
16–25 in (2Bw3)	Paragravelly silty clay loam	6.7	38%	19%	1.5%
25–33 in (2C)	Stony silty clay loam	7.0	38%	19%	1.25%
33–43 in (2R)	Bedrock	Not reported	0%	0%	0%

Representative values from the most extensive Waiakoa map unit (Waiakoa extremely stony silty clay loam, 3 to 25 percent slopes, eroded, MLRA 157, survey area HI980). 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 Waiakoa soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Waiakoa soils is neutral: pH 7.0 (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 100% of mapped Waiakoa acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is extremely stony silty clay loam (69% of mapped Waiakoa acres).

100% of mapped Waiakoa 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 Waiakoa 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 Waiakoa soil is found

Mapped acres

Waiakoa is mapped in Hawaii.

Counties with the most mapped Waiakoa soil
County	Acres	Share of county land
Maui County, HI	21,628	2.9%

Septic absorption fields

NRCS rating, share of Waiakoa acres

Not limited 0%

Somewhat limited 0%

Very limited 100%

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

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

Drainage, water table and flooding

Share of Waiakoa 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 5–14% (median 14%).
Topsoil organic matter: Median 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 Waiakoa acres. Scale 0 to 100% of mapped land.

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Drainage class across mapped Waiakoa 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 100%

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

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Hydrologic soil group across mapped Waiakoa acres.
Category	Share of acres
A: fast infiltration (mostly sandy or gravelly)	0.0%
B: moderate infiltration	0.0%
C: slow infiltration	100.0%
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 Waiakoa (component kind "Series") in SSURGO: 21,628 acres.
Method: Shares are by mapped acres of Waiakoa components. The profile comes from the single largest Waiakoa component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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