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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 Westborough Water District purchases 100% of its water from the San Francisco Public Utility Commission (SFPUC). The water supplied by the San Francisco Regional Water System (SFRWS), which is owned and operated by the SFPUC, our major water source originates from Spring Yosemite National Park snowmelt flowing down the Tuolumne River to storage in Hetch Hetchy Reservoir. The supply consists of surface water and groundwater that are well protected and carefully managed by the SFPUC. These sources are diverse in both the origin and the location with the surface water stored in reservoirs located in the Sierra Nevada, Alameda County and San Mateo County, and 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 the SFPUC’s near- and long-term water supply management strategy.

To meet drinking water standards for consumption, all surface water supplies including the upcountry non-Hetch Hetchy sources (UNHHS) undergo treatment by the SFRWS before it is delivered. Water from Hetch Hetchy Reservoir is exempt from federal and state filtration requirements but receives the following treatment: 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 UNHHS is delivered to Sunol Valley Water Treatment Plant (SVWTP); whereas water from local reservoirs in San Mateo County is delivered to Harry Tracy Water Treatment Plant (HTWTP). Water treatment at these plants consists of filtration, disinfection, fluoridation, optimum corrosion control, and taste and odor removal. In 2022, no UNHHS water was used.

Water Quality

Together with the SFRWS, we regularly collect and test water samples from reservoirs and designated sampling points throughout the system to ensure the water delivered to you meets or exceeds federal and state drinking water standards. In 2022, the SFRWS conducted more than 46,810 drinking water tests in the sources and the transmission system. This is in addition to the extensive treatment process control monitoring performed by SFRWS’s certified operators and online instruments.
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. In order to ensure that tap water is safe to drink, the U.S. Environmental Protection Agency (USEPA) and the State Water Resources Control Board (State Board) prescribe regulations that limit the amount of certain contaminants in water provided by public water systems. State Board regulations also establish limits for contaminants in bottled water that provide the same protection for public health.

Watersheds Protection

Image of Lake Tanya as part of the watershedThe SFRWS conducts watershed sanitary surveys for the Hetch Hetchy source annually and for non-Hetch Hetchy surface water sources every five years. The latest sanitary surveys for the non-Hetch Hetchy watersheds were completed in 2021 for the period of 2016-2020. All these surveys, together with SFRWS’s stringent watershed protection management activities, were completed with support from partner agencies including National Park Service and US Forest Service. The purposes of the surveys are to evaluate the sanitary conditions and water quality of the watersheds and to review results of watershed management activities conducted in the preceding years. Wildfire, wildlife, livestock, and human activities continue to be potential contamination sources. You may contact the San Francisco District office of the State Water Resources Control Board’s Division of Drinking Water (SWRCB) at 510-620-3474 for the review of these reports.

Special Health Needs

Some people may be more vulnerable to contaminants in drinking water than the general population. Immuno-compromised persons, such as those with cancer undergoing chemotherapy, persons who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly people and infants, can be particularly at risk from infections.

These people should seek advice about drinking water from their healthcare providers. USEPA/CDC guidelines on appropriate means to lessen the risk of infection by Cryptosporidium and other microbial contaminants are available from the USEPA’s Safe Drinking Water Hotline 800-426-4791 or at

Monitoring of Per- and Polyfluoroalkyl Substances (PFAS)

PFAS is a group of approximately 5,000 man-made, persistent chemicals used in a variety of industries and consumer products. In 2021, our wholesaler conducted a second round of voluntary monitoring using a newer analytical method adopted by the USEPA for some other PFAS contaminants. No PFAS were detected above the SWRCB’s Consumer Confidence Report Detection Levels in surface water and groundwater sources. For additional information about PFAS, you may visit SWRCB website, SFPUC website, and/or USEPA website

State Revised Total Coliform Rule

This report reflects changes in drinking water regulatory requirements during 2022, in which the SWRCB adopted California version of the federal Revised Total Coliform Rule. The revised rule, effective on July 1, 2021, maintains the purpose to protect public health by ensuring the integrity of the drinking water distribution system and monitoring for the presence of microbials (i.e., total coliform and E. coli bacteria). Greater public health protection is anticipated, as the revised rule requires water systems that are vulnerable to microbial contamination to identify and fix problems. Water systems that exceed a specified frequency of total coliform occurrences are required to conduct an assessment to determine if any sanitary defects exist. If found, these must be corrected by the water system.

Boron Detection Above Notification Level in Source Water

In 2022, boron was detected at a level of 1.3 ppm in the raw water stored in Pond F3 East, one of the SFRWS’s approved sources in the Alameda Watershed. Similar levels were also detected in the same pond in 2017 and 2019. Although the detected value is above the California Notification Level of 1 ppm for source water, the corresponding level in the treated water from the SVWTP was only 0.11 ppm due to blending with water from San Antonio Reservoir in the influent pipeline to the 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)