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The Westborough Water District provides its customers with high quality drinking water that is safe to drink and meets standards set by the California Department of Health Services and the United States Environmental Protection Agency.

The Westborough Water District receives 100 percent of its water from the San Francisco Water Department. The water comes from Hetch Hetchy in Yosemite National Park and local reservoirs.

The California Department of Health Services and the United States Environmental Protection Agency set standards for drinking water quality.

The District collects samples throughout the system weekly to be analyzed for coliform bacteria, chlorine residual, pH, and turbidity. Every three months the District collect samples to monitor for trihalomethanes, or THMs, compounds formed when the chlorine used for disinfection reacts with naturally occurring organic compounds found in water. Water quality is monitored daily at the Harry Tracy treatment plant by the San Francisco Water Department.

Water Quality Reports

Our Drinking Water Sources and Treatment

The San Francisco Public Utilities Commission provides 2.7 million customers in cities and towns across the region through its San Francisco Regional Water System (SFRWS) with water so high quality that it meets all federal and state standards. They are committed to providing high-quality drinking water for all its customers.

The Westborough Water District purchases 100% of its water from the San Francisco Public Utility Commission (SFPUC). The SFRWS’s drinking water supply consists of surface water and groundwater that are well protected and carefully managed. These sources are diverse in both origin and location with the surface water stored in reservoirs located in the Sierra Nevada, Alameda County and San Mateo County, as well as groundwater stored in a deep aquifer located in the northern part of San Mateo County. Maintaining this variety of sources is an important component of our near- and long-term water supply management strategy. A diverse mix of sources protects us from potential disruptions due to emergencies or natural disasters, provides resiliency during periods of drought, and helps us ensure a long-term, sustainable water supply as we address issues such as climate uncertainty, regulatory changes, and population growth.

To meet drinking water standards for consumption, all surface water sources including the upcountry non-Hetch Hetchy sources undergo treatment before it is delivered to our customers. While the water from Hetch Hetchy Reservoir is exempt from state and federal filtration requirements, it does receive the following treatment before being delivered for your consumption: disinfection using ultraviolet light and chlorine, pH adjustment for optimum corrosion control, fluoridation for dental health protection, and chloramination for maintaining disinfectant residual and minimizing the formation of regulated disinfection byproducts. Water from local Bay Area reservoirs in Alameda County and upcountry non-Hetch Hetchy sources is delivered to Sunol Valley Water Treatment Plant; whereas water from local reservoirs in San Mateo County is delivered to Harry Tracy Water Treatment Plant. Water treatment at these plants consists of filtration, disinfection, fluoridation, optimum corrosion control, and taste and odor removal. In 2023, neither upcountry non-Hetch Hetchy sources nor groundwater was used by the SFRWS.

Water Quality

The SFRWS regularly collects and tests water samples from reservoirs and designated sampling locations throughout its system to ensure the water delivered to you meets all state and federal drinking water standards. In 2023, the SFRWS conducted more than 49,610 drinking water tests in the source, transmission, and distribution system. This is in addition to its extensive treatment process control monitoring performed by the certified operators and online instruments.

As water travels over the surface of the land or through the ground, it dissolves naturally occurring minerals and, in some cases, radioactive material, and can pick up substances resulting from the presence of animals or human activity. Collectively these are called contaminants. Therefore, drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of contaminants does not necessarily indicate that water poses a health risk. To ensure that tap water is safe to drink, the United States Environmental Protection Agency and the State Water Resources Control Board prescribe regulations that limit the amount of certain contaminants in water provided by public water systems. The United States Food and Drug Administration regulations and California law also establish limits for contaminants in bottled water that provide the same protection for public health.

Image of the Hetch Hetchy watershedProtection of Watersheds

The SFRWS conducts watershed sanitary surveys for its Hetch Hetchy source annually and, every five years for its local water sources and upcountry non-Hetch Hetchy sources. The latest sanitary surveys for the non-Hetch Hetchy watershed were completed in 2021 for the period of 2016-2020. All these surveys together with our stringent watershed protection management activities were completed with support from partner agencies including the National Park Service and the United States Forest Service. The purposes of these annual and quinquennial surveys are to evaluate the sanitary conditions and water quality of the watersheds and to review the results of watershed management activities conducted in the preceding years. Wildfire, wildlife, livestock, and human activities continue to be the potential contamination sources. You may contact the San Francisco District office of the State Water Resources Control Board’s Division of Drinking Water at 510-620-3474 for more information.

image of two children drinking water from a glassSpecial Health Needs

Some people may be more vulnerable to contaminants in drinking water than the general population. Immunocompromised persons, such as those with cancer undergoing chemotherapy, persons who have undergone organ transplants, people with Human Immunodeficiency Virus / Acquired Immunodeficiency Syndrome or other immune system disorders, and some elderly people and infants, can be particularly at risk from infections. These people should seek advice about drinking water from their healthcare providers.

Cryptosporidium is a parasitic microbe found in most surface water. The SFRWS regularly test for this waterborne pathogen and found it at very low levels in source water and treated water in 2023. However, current test methods approved by the United States Environmental Protection Agency do not distinguish between dead organisms and those capable of causing disease. Ingestion of Cryptosporidium may produce symptoms of nausea, abdominal cramps, diarrhea, and associated headaches. Cryptosporidium must be ingested to cause disease, and it may be spread through means other than drinking water.

The United States Environmental Protection Agency and the Centers for Disease Control and Prevention guidelines on appropriate means to lessen the risk of infection by Cryptosporidium and other microbial contaminants are available from the United States Environmental Protection Agency’s Safe Drinking Water Hotline at 800-426-4791 or at

No PFAS Detected

Per- and poly-fluoroalkyl substances (PFAS) comprise a group of man-made, persistent chemicals that have been used in the industry and consumer products since the 1940s. We did not detect PFAS in our water. To learn more, visit

Unregulated Contaminant Monitoring Rule

The SFRWS conducted four consecutive quarters of monitoring at designated locations approved by the United States Environmental Protection Agency in 2023, and all results have been non-detected.

Boron Detection Above Notification Level in Source Water

In 2023, boron was detected at a level of 1.7 ppm in the raw water stored in Pond F3 East, one of the San Francisco Regional Water System’s approved sources in the Alameda Watershed. Similar levels were also previously detected in the same pond. Although the detected value was above the California Notification Level (NL) of 1 ppm, the water was typically delivered to San Antonio Reservoir where it was substantially diluted to below the NL before treatment at the Sunol Valley Water Treatment Plant. Boron is an element in nature and is typically released into air and water when soils and rocks naturally weather.

Fluoridation and Dental Fluorosis

Mandated by state law, water fluoridation is a widely accepted practice proven safe and effective for preventing and controlling tooth decay. Our fluoride target level in the water is 0.7 milligram per liter (mg/L, or part per million, ppm), consistent with the May 2015 state regulatory guidance on optimal fluoride level. Infants fed formula mixed with water containing fluoride at this level may still have a chance of developing tiny white lines or streaks in their teeth. These marks are referred to as mild to very mild fluorosis and are often only visible under a microscope. Even in cases where the marks are visible, they do not pose any health risk. The Centers of Disease Control (CDC) considers it safe to use optimally fluoridated water for preparing infant formula. To lessen this chance of dental fluorosis, you may choose to use low fluoride bottled water to prepare infant formula. Nevertheless, children may still develop dental fluorosis due to fluoride intake from other sources such as food, tooth paste and dental products.

Contact your healthcare provider or the SWRCB if you have concerns about dental fluorosis. For additional information about fluoridation or oral health, visit the SWRCB website HERE, or the CDC website

Drinking Water and Lead

Exposure to lead, if present, can cause serious health effects in all age groups, especially for pregnant women and young children. Infants and children who drink water containing lead could have decreases in IQ and attention span and increases in learning and behavior problems. The children of women who are exposed to lead before or during pregnancy can have increased risk of these adverse health effects. Adults can have increased risks of heart disease, high blood pressure, kidney, or nervous system problems.

Lead in drinking water is primarily from materials and components associated with service lines and home plumbing. There are no known lead service lines in our water distribution system. We are responsible for providing high quality drinking water and removing lead pipes, but we cannot control the variety of materials used in plumbing components in your home. You share the responsibility for protecting yourself and your family from the lead in your home plumbing. You can take responsibility by identifying and removing lead materials within your home plumbing and taking steps to reduce your family’s risk. Before drinking tap water, flush your pipes for several minutes by running your tap, taking a shower, doing laundry or a load of dishes. You can also use a filter certified by an American National Standards Institute accredited certifier to remove lead from drinking water. If you are concerned about lead in your water and may wish to have your water tested, contact the Westborough Water District at 650-589-1435 for a lead test. Information about lead in drinking water, testing methods, and steps you can take to minimize exposure is available at USEPA website

Lead User Service Line (LUSL)

As previously reported in 2018, we completed an inventory of lead user service lines (LUSL) in our system and there are no known pipelines and connectors between water mains and meters made of lead. Our policy is to remove and replace any LUSL promptly if it is discovered during pipeline repair and/or maintenance.

Lead Testing of Drinking Water in Schools

South San Francisco Unified School District conducts their own lead and copper testing.

Lead and Copper Tap Sampling Results

We conducted the triennial Lead and Copper Rule (LCR) monitoring in 2022, and none of the 30 samples collected at the consumer taps had lead or copper concentrations above the action levels. The next round of LCR monitoring will be conducted in 2025.

Urban Water Management Report

In compliance with the Urban Water Management Planning Act, the Westborough Water District (WWD.) has prepared its sixth updated Urban Water Management Plan (UWMP) under the terms of AB797 (1983) and subsequent amending legislation.

On June 10, 2021, this plan was presented at a Public Hearing and approved by the WWD Board of Directors. It supercedes the existing plan prepared in 2015, and will be used by the District staff to guide the District's water conservation efforts through the year 2025.

Click here for 2020 Urban Water Management Report (UWMP) (PDF)

Click here for 2015 Urban Water Management Report (UWMP) (PDF)