Sampling & Testing

LaboratoryAs your water provider, the City is required to meet stringent drinking water regulations. These requirements are regulated by the U.S. Environmental Protection Agency (EPA) and the California State Water Resources Control Board in accordance with the Safe Drinking Water Act and Title 22 of the California Code of Regulations. Continual sampling and testing is conducted at our source waters, throughout our treatment plant processes, at key locations in the distribution system, and even at some customers’ taps.

Laboratory testing monitors both regulated and unregulated contaminants to address the following:

Primary Standards (Health)

***Testing Confirms Your Drinking Water Meets all Primary Standards***

U.S. EPA regulations protect the public by establishing legally enforceable Maximum Contaminant Levels (MCLs) or treatment techniques for drinking water contaminants that present a risk to human health. An MCL is the highest level of a contaminant allowed in drinking water delivered to customers. These health-based standards are set for about 90 contaminants including:

  • Microorganisms, such as viruses and bacteria
  • Disinfectants, such as Chlorine
  • Disinfection Byproducts, such as Bromate, Trihalomethanes (THMs), and Haloacetic Acids (HAAs)
  • Inorganic Chemicals, such as salts and metals
  • Organic Chemicals, including synthetic and volatile organic chemicals (VOCs)
  • Radionuclides, naturally occurring or the result of industrial activities

There are some minor differences between California MCLs and Federal MCLs.

Special rules and testing protocols govern contaminants of particular interest:

Under State law, the City is required to send monthly water monitoring reports to the State Water Resources Control Board to ensure test results comply with water quality standards. View the City’s 2020 Monthly Summaries of Water Quality Data (PDF).

An annual Drinking Water Quality Report provided to customers summarizes test results for any substances detected during the most recent calendar year.

Secondary Standards (Aesthetic)

***Testing Confirms Your Drinking Water Meets all Secondary Standards***

Secondary MCLs address contaminants that can adversely affect the taste, odor, or appearance of drinking water.

  • Taste & Odor may be impacted by:
    • Chloride, Copper, Foaming Agents, Iron, Manganese, Sulfate, Threshold Odor Number (TON), Total Dissolved Solids (TDS), Zinc
  • Appearance may be impacted by:
    • Aluminum, Color, Copper, Iron, Manganese, TDS

Occasionally, some City customers experience a different taste or odor in their drinking water. Some describe the water as tasting and smelling earthy, musty, or moldy. This is caused by naturally occurring compounds produced by algae blooms in Lake Hennessey. This tends to be a seasonal issue in the fall when the lake is ’turning over’. While algae itself is removed by the water treatment process, odor-causing compounds can remain. The City works to mitigate this issue through source water monitoring and a pre-treatment oxidizer. A more complete solution will be achieved with upgrades to the Hennessey Water Treatment Plant. Now in the very early planning stage, these upgrades will require a large capital investment that must be approved in future City budgets.

For the annual Drinking Water Quality Report, Color (MCL=15 units) and Odor (MCL=3 units TON) tested below detection limits and were therefore excluded from the published test results.

If specific Taste & Odor or Color issues are ever known in advance, the City will do its best to inform affected water customers via social media, local news media, and this web site. One example is the scheduled annual Hydrant Flushing Program which can temporarily impact water color in the affected zones.

Unregulated Contaminant Monitoring

Some contaminants are not presently regulated by an MCL, but testing and monitoring are required due to State regulations or the Federal Unregulated Contaminant Monitoring Rule (UCMR4). The City participated in the UCMR4 program which helps provide EPA with scientifically valid data on the occurrence of emerging contaminants suspected to be in drinking water. This sampling and testing benefits the environment and public health by informing future EPA regulatory standards. Unregulated contaminant monitoring data are available to the public, so if interested please call 707-253-0822 or Email the Water Quality Manager