Buying Land in Contra Costa County, California

A county of contrasts: refinery corridor, suburbs, and the Delta

Contra Costa County spans genuinely distinct landscapes: an industrial waterfront along the Carquinez Strait and northern shoreline (Richmond, Martinez, Rodeo, and Pittsburg all host major petroleum refining and related industry), a dense band of East Bay suburban cities (Walnut Creek, Concord, San Ramon, Danville) surrounding Mount Diablo, and, in the county's far eastern reaches, agricultural land around Brentwood and Byron that gives way to the leveed island communities of the Sacramento-San Joaquin Delta. Which part of the county a parcel sits in changes the relevant due-diligence questions almost entirely.

The Delta: levees, reclamation districts, and land below sea level

Communities including Bethel Island, Oakley's Delta-adjacent areas, and Knightsen sit within the Sacramento-San Joaquin Delta, a network of leveed islands and channels where decades of peat-soil oxidation and subsidence have left some land sitting below the level of the surrounding waterways, protected only by levees that local reclamation districts (special districts organized under state law) are responsible for maintaining. This is a genuinely distinctive flood-risk profile compared to ordinary floodplain land, and it's covered in more depth on the dedicated flood-zones page below.

On top of levee and reclamation-district considerations, the Delta Reform Act of 2009 established the Delta Stewardship Council and a statutory Delta Plan that governs land use and development decisions within the legally defined Delta boundary -- a state-level review layer distinct from, and additional to, Contra Costa County's ordinary zoning process. Confirm whether a specific parcel falls within the statutory Delta boundary before assuming county zoning tells the whole story.

Agricultural land around Brentwood and Byron

East of the Delta communities, the area around Brentwood and Byron has a long-standing identity as productive farmland, historically known for orchard crops and u-pick operations along with row crops, benefiting from the same rich Delta-adjacent soils. A meaningful share of this land carries Williamson Act contracts. Separately, this area has also been the subject of long-running local growth-management planning -- including habitat conservation planning covering new development at the urban edge -- worth asking the county about directly if a parcel sits near the boundary between agricultural land and expanding suburban development.

General zoning, water, and septic

Outside Contra Costa County's many incorporated cities, unincorporated land is governed by the Contra Costa County Department of Conservation and Development, which handles zoning and building permits. Where public water and sewer aren't available -- mainly in the eastern and Delta-adjacent parts of the county -- private wells and septic systems are permitted through Contra Costa Environmental Health under California's statewide OWTS framework. Confirm well and septic feasibility, and the applicable reclamation district's assessment obligations for Delta parcels, directly with the relevant agency.