Oakley Water Hardness & Quality Report (2026)

Oakley, California, in Contra Costa County — a rapidly growing east Contra Costa County community in the Sacramento–San Joaquin Delta region, a major Delta fringe community transitioning from agricultural to residential character, adjacent to Brentwood and Antioch on the east Bay Area Delta fringe, and a diverse east Contra Costa County community in the growing eastern Bay Area exurban corridor — draws its municipal water supply from the Sacramento–San Joaquin Delta via the Contra Costa Water District (CCWD) and the City of Oakley Water Division. Water hardness in Oakley measures 145 mg/L — classified as moderately hard.

Oakley's moderate hardness reflects the east Contra Costa County CCWD Sacramento–San Joaquin Delta supply characteristics. The CCWD draws from the Sacramento–San Joaquin Delta (water draining the Central Valley — the Sierra Nevada granitic calcareous-moderate runoff blended with San Joaquin Valley calcareous agricultural return flows and the Delta tidal mixing zone). CCWD stores and treats Delta water in the Los Vaqueros Reservoir (off-stream storage in the Diablo Range foothill). The Delta supply and CCWD treatment produce the moderate 145 mg/L at Oakley in the east Contra Costa distribution zone.

At 145 mg/L, Oakley residents encounter moderate scale accumulation. Monthly cleaning with citric acid solution is recommended. CCWD consistently delivers water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.