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San Benito County, California

Shrink-swell clay limits houses without basements on 21% of San Benito County's mapped land, a higher share than 71% of US counties. A shallow water table limits basements on 4%.

The soil survey maps 85% of the county's land area; these shares describe the mapped part. None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 78 flood losses here since 2016, 0% of them in buildings with basements. 35% of homes were built before 1980, against 50% nationally; the median home dates from 1989.

Data as of October 13, 2026 · sources

21%

expansive clay: shrink-swell limits slab homes

4%

high water table: limits basements

0%

in drought, October 13, 2026

35%

of homes built before 1980

Soil under San Benito County

Expansive clay (limits slab homes)20.7%
High water table (limits basements)4.0%
Septic fields very limited83.0%
Clay swell (LEP, by area)4.5%
High-swell land (LEP 6%+)18.4%
Mapped soil758,567 acres
Soil seriesShare hereSeries nationally: expansive clay
San Benito12%n/a
Diablo5%n/a
Vallecitos5%n/a
Gaviota5%n/a
Kettleman4%n/a
Sorrento3%n/a
Monterey County: 15%Merced County: 28%Santa Clara County: 24%Santa Cruz County: 10%Stanislaus County: 24%Kings County: 32%Fresno County: 14%Alameda County: 38%San Benito County MontereyMercedSanta ClaraSanta CruzStanislausKingsFresnoAlamedaSan Benito
San Benito County (heavy outline) and nearby counties, shaded by expansive clay share.under 10%10-25%25-40%40-60%60%+

How we count · survey areas CA069 (2025-08-29), CA788 (2025-09-02)

What the numbers mean here

Clay swell averages a linear extensibility of 4.5% by land area here, and 18% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 21% of the mapped land.

Rain over the 12 months to August 2026: 19.66 in, 2.47 in above the 1991-2020 average year of 17.19 in.

USDA rates 83% of the land very limited for septic absorption fields.

Drought

0% of the county is in drought (D1 or worse) on the October 13, 2026 map. No part of the county was in drought in the last 52 weeks.

October 21, 2025Share of area in drought, weeklyOctober 13, 2026
Category, October 13, 2026Share of county
D0 abnormally dry or worse0%
D1 moderate drought or worse0%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

78 flood losses since 2016, $3.2 million paid. The worst year was 2017, with 39. Foundations of the buildings, where recorded: 21% slabs, 65% crawl spaces, 14% elevated. Median water depth outside the building: 17 in.

YearFlood losses
20162
201739
20180
20191
20200
20210
20220
202336
20240
20250
2026 to date0

Rain

Average year, 1991-202017.19 in
12 months to August 202619.66 in (+2.47)
202517.83 in (+0.64)
Wettest year since 18951983: 33.86 in
Driest year since 18952013: 3.53 in
Days with 1 inch or more, normal at PINNACLES NM (10 mi away)3.6

Homes

Housing units21,322
Median year built1989
Built before 198035%
Built 2000 or later27%
Owner-occupied68%
Median value, owner-occupied$793,400
Single-family detached80%

What repairs cost

Published ranges from cost guides, not quotes. More sources, and where they disagree.

WorkRangeSource
Foundation repair, US $2,200 to $8,200 Fixr, January 27, 2026
Pier-and-beam repair, US $2,000 to $15,000 Fixr, January 27, 2026
Foundation inspection, US $300 to $600 Fixr, January 31, 2025

Nearby counties

PlaceDistanceExpansive clayHigh water table
Monterey County, CA 29 mi 15% 2%
Merced County, CA 45 mi 28% 27%
Santa Clara County, CA 54 mi 24% 3%
Santa Cruz County, CA 58 mi 10% 1%
Stanislaus County, CA 66 mi 24% 7%
Kings County, CA 80 mi 32% 33%
Fresno County, CA 80 mi 14% 2%
Alameda County, CA 84 mi 38% 8%

Sources: USDA SSURGO (September 2, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status