Contra Costa County, California: drinking water report. Contra Costa County sits east of San Francisco Bay, home to about 1.2 million residents.
Contra Costa County sits east of San Francisco Bay, home to about 1.2 million residents. The Contra Costa Water District (CCWD) is the largest provider, drawing from the Sacramento-San Joaquin Delta and Los Vaqueros Reservoir. The East Bay Municipal Utility District (EBMUD) serves western county communities from the Mokelumne River. This split means residents just a few miles apart may drink water from entirely different sources with distinct quality profiles.
The Sacramento-San Joaquin Delta is one of the most complex water quality environments in California. The Delta receives agricultural drainage, treated wastewater, and stormwater from the entire Central Valley, and saltwater intrusion from San Francisco Bay pushes upstream during dry periods. CCWD has invested heavily in Los Vaqueros Reservoir to store higher-quality water during wet months and use it when Delta water quality degrades.
UCMR5 data shows PFAS detections in several Contra Costa County systems. The former Concord Naval Weapons Station is a potential PFAS source. According to the California State Water Resources Control Board, five public water systems in the county reported PFAS above notification levels during 2024 monitoring.
Knowing whether you are on CCWD, EBMUD, or another provider is the first step – it determines your source water and contaminant profile.
Check your water to identify your provider and see monitoring data. For Delta-sourced water, activated carbon helps with taste and disinfection byproducts. For PFAS, reverse osmosis is more effective. Our water filter guide covers the tradeoffs. Pull your detailed report, and visit our California page for statewide patterns.