Danville Water Hardness & Quality Report (2026)

East Bay Municipal Utility District (EBMUD) provides water to Danville, California, in Contra Costa County, serving over 1.4 million people across Alameda and Contra Costa counties. Primary supply (80–90%) comes from the Mokelumne River via three aqueducts from Pardee Reservoir in the Sierra foothills. Local reservoirs including San Pablo, Chabot, Lafayette, and Briones supply the remainder during dry periods. Treatment occurs at the El Cerrito Plant, Sobrante Plant, and Walnut Creek Plant, using conventional filtration, ozonation, and chloramination.

The Mokelumne Watershed spans 1,400 square miles in the Sierra Nevada, with headwaters in granitic batholiths and metavolcanic terrains of the Calaveras Complex. Surface runoff flows over quartz-rich igneous rocks — quartz diorite and granodiorite of the Sierra Nevada Batholith — picking up minimal dissolved minerals. Local East Bay reservoirs drain the Franciscan Formation's sheared sandstones and shales, geologically young low-carbonate formations that further limit mineral content, contributing to a naturally soft supply.

As a soft water supply, Danville experiences minimal scale buildup on fixtures, pipes, and appliances such as water heaters, dishwashers, and coffee makers. Soap lathers easily, reducing usage and avoiding dry skin or residue issues common in harder areas. No softener is needed; basic maintenance like periodic descaling of visible deposits and checking aerators is sufficient. EBMUD consistently meets lead and copper rules under the EPA LCR, with 90th percentile copper below 1.0 mg/L and no lead action level exceedances. No PFAS detections above advisory levels are reported in annual CCRs.