Contra Costa County Soil Data
Contra Costa County, California
USDA SSURGO / PHZMAvg pH
6.4
Texture
Clay Loam
Drainage
N/A
Organic Matter
4.1%
Hydrologic Group
D
Data Story
About Soil in Contra Costa County, California
Perfectly Balanced Coastal Soils
Contra Costa County boasts a near-perfect average pH of 6.44, sitting just under the national 6.5 median. This puts it slightly above the state average of 6.34, creating a highly hospitable environment for diverse plant life. It is an ideal baseline for most gardening and agricultural projects.
A Rich Loam-Like Texture
The soil is comprised of 32.9% sand, 33.0% silt, and 29.7% clay. This remarkably balanced distribution offers excellent nutrient storage while maintaining enough structure to support healthy root systems. It provides a great mix of workability and water retention.
Superior Organic Wealth and Hydration
The county excels with 4.14% organic matter, well above the California average of 3.30%. Combined with an available water capacity of 0.152 in/in, these soils are naturally fertile and resilient against dry spells. Your plants will have plenty of fuel to thrive.
Planning for High Runoff Potential
As part of Hydrologic Group D, the soil naturally absorbs water slowly and is prone to high runoff. This means gardeners should consider using raised beds or adding drainage channels to protect roots during heavy rain. Careful site planning will help you manage these heavy soils effectively.
Prime Growing in Zone 9b
With a high soil score of 65.1 compared to the state average of 48.6, Contra Costa is a gardener's dream. Hardiness Zone 9b is perfect for tomatoes, peppers, and world-class grapes, so grab your shovel and get planting.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Group D — High Runoff
Clay soils with very slow infiltration rates. Highest runoff potential. These soils have a permanent high water table or are shallow over impervious material.
Drainage Class
Drainage class data not available.
Soil Profile
Dominant texture: Clay Loam
Typical soil profile. Actual depths vary by location.
USDA Soil Orders
Clay Soil Detected
Clay soils can struggle with drainage. These products improve soil structure and water flow.
Browse Soil AmendmentsFrequently Asked Questions
What type of soil does Contra Costa County have?
Contra Costa County's soil is classified as Clay Loam. This indicates the relative proportions of sand, silt, and clay — 33% sand, 33% silt, and 30% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Contra Costa County's soil acidic or alkaline?
Contra Costa County's soil has a pH of 6.4, which is moderately acidic. This range suits many crops and is common across much of the eastern US.
What is the drainage class for Contra Costa County?
Drainage class data is not currently available for Contra Costa County.
What crops or plants grow well in Contra Costa County's soil?
Based on Contra Costa County's Clay Loam texture, pH of 6.4, and drainage class, the soil is well suited for vegetables, grains, and most field crops, row crops and vegetable gardens.
What USDA soil order is found in Contra Costa County?
The dominant USDA soil order for Contra Costa County is not currently available in our dataset.
Soil & Planting Advisory: Contra Costa County
Soil Verdict
Contra Costa County is in USDA hardiness zone 9b, a warm climate zone. where winter lows can reach 25°F. Warm winters keep soil biology active nearly year-round, accelerating decomposition but increasing pest and disease pressure in topsoil.
Planting Guidance
Tropical and subtropical plants are viable. Year-round gardening is possible, though summer heat may limit some cool-season crops. Frost is rare; tender plants can overwinter with minimal protection. Always match plant selections to the specific microclimate of your property — low spots, slopes, and wind exposure can shift effective hardiness by half a zone.
Soil Implications
Rapid organic matter turnover means soils can become nutrient-poor quickly; test annually and fertilize based on results. High soil temperatures favor certain soilborne pathogens; practice crop rotation and avoid overwatering.
Regional Context
Contra Costa County closely matches the California average hardiness conditions. The zone range of 9b-10a within the county means soil and planting decisions should account for local elevation and topography.
Planning your lawn? View lawn care data for Contra Costa County on LawnByCounty.com →
Other Counties in California
Soil data sourced from USDA SSURGO via Soil Data Access. Data is informational only and should not be used as a substitute for on-site soil testing. Contact your local NRCS office for site-specific soil information.