Soil series profile

Bonnydoon soil series

Bonnydoon is a somewhat excessively drained soil with a gravelly loam surface, mapped on 25,903 acres in 3 counties in CA. Hydrologic group D.

#9081 by mapped area loamy Entic Haploxerolls (Mollisols)

Drainage class: Somewhat excessively drained
Hydrologic group: D
Typical topsoil pH: 6.5
Mapped area: 26k

Typical Bonnydoon 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).

Show as a table

Typical Bonnydoon horizons (representative values)
Depth	Texture	pH	Clay	Sand	Organic matter
0–15 in (H1)	Gravelly loam	6.5	24%	39%	2%
15–19 in (H2)	Bedrock	Not reported	Not reported	Not reported	Not reported

Representative values from the most extensive Bonnydoon map unit (Bonnydoon gravelly loam, 30 to 75 percent slopes, survey area CA041). 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 Bonnydoon soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Bonnydoon soils is slightly acidic: pH 6.5 (most land between 6.3 and 6.5), the range most vegetables, flowers and lawn grasses prefer.

Loamy topsoil (loam, silt loam and similar) covers 85% of mapped Bonnydoon acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is gravelly loam (59% of mapped Bonnydoon acres).

85% of mapped Bonnydoon acres is excessively or somewhat excessively drained: water moves through fast, so gardens need more frequent watering in dry spells.

For lawns and yards

On 85% 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 85% of the acres in mapped Bonnydoon soils very limited, 0% somewhat limited and 0% not limited (15% not rated, such as urban land, pits or water).

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 Bonnydoon soil is found

Mapped acres

Bonnydoon is mapped in California.

Counties with the most mapped Bonnydoon soil
County	Acres	Share of county land
Marin County, CA	18,998	5.7%
Santa Cruz County, CA	6,723	2.4%
Santa Clara County, CA	182	0.0%

Septic absorption fields

NRCS rating, share of Bonnydoon acres

Not limited 0%

Somewhat limited 0%

Very limited 85%

Not rated 15%

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

Show as a table

Septic tank absorption field rating across mapped Bonnydoon acres.
Category	Share of acres
Not limited	0.0%
Somewhat limited	0.0%
Very limited	85.1%
Not rated	14.9%

Drainage, water table and flooding

Share of Bonnydoon 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 18–63% (median 40%).
Topsoil organic matter: Median 2%.

Drainage class

Excessively drained 0%

Somewhat excessively drained 85%

Well drained 0%

Moderately well drained 0%

Somewhat poorly drained 0%

Poorly drained 0%

Very poorly drained 0%

Not rated 15%

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

Show as a table

Drainage class across mapped Bonnydoon acres.
Category	Share of acres
Excessively drained	0.0%
Somewhat excessively drained	85.1%
Well drained	0.0%
Moderately well drained	0.0%
Somewhat poorly drained	0.0%
Poorly drained	0.0%
Very poorly drained	0.0%
Not rated	14.9%

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) 85%

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 15%

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

Show as a table

Hydrologic soil group across mapped Bonnydoon 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)	85.1%
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	14.9%

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 Bonnydoon (component kind "Series") in SSURGO: 25,903 acres.
Method: Shares are by mapped acres of Bonnydoon components. The profile comes from the single largest Bonnydoon component. Full methodology.

Independent reference site. No government affiliation or endorsement.

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