Water Quality Data
Your water is regularly tested for more than 120 chemicals and other substances, as well as radioactivity. The table below provides detailed information about the water that comes from your tap after it is treated (treated water) and before it is treated (raw water). The substances shown are ones that our customers have the most questions about.
You can also view the latest Annual Water Quality Report, which lists the annual results for these substances as well as many others.
For a comprehensive list of contaminants that we test for and have not been detected in our water supply, see our 2018 Contaminants Not Detected List (PDF).
Also, the United States Environmental Protection Agency has additional contaminant list information about the fourth Unregulated Contaminant Monitoring Rule (UCMR 4). For general background information, see their UCMR Basic Information Fact Sheet (PDF).
Questions? Call our Water Quality Hotline at 925-688-8156 or email us.
|Substance||Maximum Contaminant Level*||Most Recent Result||Date||Source|
|Arsenic||0.01 mg/L||< 0.002 mg/L||7/16/2018||BCWO annual|
|Chloride||No MCL (65 mg/L CCWD Internal Action Level)||56 mg/L||5/14/2019||BCWO|
|Chlorine Residual||4.0 mg/L||3.6 mg/L||5/28/2019||BCWO|
|Mercury||0.002 mg/L||<0.0002 mg/L||7/16/2018||BCWO annual|
|Radon **||300 pci/L||<100pci/L||3/2019||Mallard Res; triennial|
|Total Coliforms||>5% positive||0.5% positive||5/2019||Last DDW report|
|Hardness||No MCL||82 mg/L||5/14/2019||BCWO|
|Hardness||No MCL||4.8 grains/gallon||5/14/2019||BCWO|
*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.
**untreated (raw) water sample
pci/L = picocuries per liter
mg/L = milligrams per liter = parts per million
ug/L = micrograms per liter = parts per billion
R/BCWO = Randall-Bold Clearwell Out
BCWO = Bollman Clearwell Out
DDW = Division of Drinking Water