Water Quality Data

Lab TestingYour water is regularly tested for more than 120 chemicals and other substances, as well as radioactivity. Every year, we produce an Annual Water Quality Report, which lists the annual results for the chemicals and other substances detected in your water. The table below provides detailed information about the water that is delivered to your home or business after it is treated (treated water) and before it is treated (untreated water). The substances shown in this table are ones that our customers have the most questions about. Call our Water Quality Hotline with questions at 925-688-8156 or send us an email.

Also, the US Environmental Protection Agency collects data for contaminants that may be present in drinking water, but are not currently subject to EPA drinking water regulations. Learn about the fifth Unregulated Contaminant Monitoring Rule.

Recent Water Quality Results

  1. SubstanceMaximum Contaminant LevelMost Recent ResultDateSource
    Arsenic0.01 mg/L< 0.002 mg/L7/18/2023BCWO Annual
    ChlorideNo MCL30 mg/L10/10/2023BCWO
    Chlorine Residual4.0 mg/L3.0 mg/L10/31/2023BCWO
    Total Coliforms>5% positive0% positive10/2023Last DDW Report
    HardnessNo MCL61 mg/L10/10/2023BCWO
    HardnessNo MCL3.6 grains/gallon10/10/2023BCWO


Maximum Contaminant Level (MCL): The highest level of a contaminant that is allowed in drinking water based on health risk coupled with economic and technical feasibility for control/treatment.

mg/L (milligrams per liter)
ppm (parts per million)
1 second in 11.5 days


R/BCWO = Randall-Bold Water Treatment Plant Clearwell Out

BCWO = Bollman Water Treatment Plant Clearwell Out

DDW = Division of Drinking Water