District: Los Altos Suburban District
System: Los Altos Suburban
System ID: #4310001
Since 1926, California Water Service (Cal Water) has been committed to providing a reliable supply of safe, clean water to our customers and communities. With the coronavirus pandemic, access to high-quality water became particularly top of mind. Throughout the pandemic and beyond, our commitment to our customers has remained as strong as ever.
In this system in 2021, we conducted 11,999 tests on 1,820 water samples for 223 constituents. We are pleased to confirm that we met every primary and secondary federal and state water quality standard last year.
Our promise to provide quality, service, and value means more than just treatment and testing. It means having expert professionals available to assist with routine services in a safe and efficient manner. It means having personnel available to handle emergencies 24 hours per day. It means maintaining and upgrading the infrastructure needed to transport water through a network of pumps, tanks, and pipes to your tap. It also means that, even with costs increasing across the country, we do everything we can to operate as efficiently as possible to keep your water affordable.
I encourage you to review this annual water quality report, also called your Consumer Confidence Report, as it details any constituents detected in your water supply in 2021 and shows how your water compares to federal and state standards. It also provides information on current water quality issues and steps we are taking to protect your health and safety.
If you have any questions, we are here to assist you. You can reach us by phone or email at our local Customer Center, or online. You can also get water service news on our web site, and via our Facebook, Twitter, and Instagram pages. If you're an account holder, you can find updates in your monthly bill and should keep your contact information up to date by visiting ccu.calwater.com to ensure you receive important emergency and other information.
Dawn Smithson, District Manager, Los Altos Suburban District
There were no significant issues in your water system in 2021, and we have no recommended action items for our customers in this area.
If you have any questions, suggestions, or concerns, please contact our local Customer Center, either by phone at (650) 917-0152 or through the Contact Us page.
Your Water System
Cal Water has provided high-quality water utility services in the Los Altos area since 1931. To meet the needs of our customers in Los Altos and parts of Los Altos Hills, Cupertino, Mountain View, and Sunnyvale, we use a combination of local groundwater and purchased water. Our purchased water, which is treated surface water from Valley Water (formerly called the Santa Clara Valley Water District), comes from Valley Water reservoirs and the San Joaquin-Sacramento River Delta.
Our water system includes 297 miles of main, 65 booster pumps, and 46 storage tanks. Cal Water's company-wide water quality assurance program includes vigilant monitoring throughout our systems and testing at our state-of-the-art laboratory. Additionally, we proactively maintain and upgrade our facilities to ensure a reliable, high-quality supply.
The Water Quality Lab
Water professionals collect samples from throughout the water system for testing at our newly upgraded, state-of-the-art water quality laboratory, which is certified each year through the stringent Environmental Laboratory Accreditation Program (ELAP).
Scientists, chemists, and microbiologists test the water for 326 constituents with equipment so sensitive it can detect levels as low as one part per trillion. In order to maintain the ELAP certification, all of our scientists must pass blind-study proficiency tests for every water quality test performed. Water quality test results are entered into our Laboratory Information Management System (LIMS), a sophisticated software program that enables us to react quickly to changes in water quality and analyze water quality trends in order to plan effectively for future needs.
By the end of 2002, Cal Water had submitted to the Division of Drinking Water (DDW) a Drinking Water Source Assessment and Protection Program (DWSAPP) report for each water source in the water system. The DWSAPP report identifies possible sources of contamination to aid in prioritizing cleanup and pollution prevention efforts.
The water sources in your district are considered most vulnerable to the following activities, for which no associated contaminant has been detected:
- Sewer collection systems
- Gas stations
- Dry cleaners
- Underground storage tanks (confirmed leaking tanks)
- Chemical/petroleum pipelines
- Electrical/electronic manufacturing
- Research laboratories
- Agricultural drainage
- Wells (agricultural)
Valley Water provides treated surface water to the Silicon Valley from three water treatment plants. Valley Water surface water is mainly imported from the South Bay Aqueduct, Lake Del Valle, and San Luis Reservoir, which all draw water from the Sacramento-San Joaquin Delta watershed. Valley Water's local water sources include Anderson and Calero Reservoirs.
Valley Water's source waters are vulnerable to potential contamination from a variety of land-use practices, such as:
- Agricultural and urban runoff
- Recreational activities
- Livestock grazing
- Residential and industrial development
The imported sources are also vulnerable to:
- Wastewater treatment plant discharges
- Seawater intrusion
- Wildland fires in open space areas
Additionally, local sources are vulnerable to potential contamination from:
- Commercial stables
- Historic mining practices
No contaminant associated with any of these activities has been detected in Valley Water or Los Altos treated water. The water treatment plants provide multiple barriers for physical removal and disinfection of contaminants. For additional information, visit the Valley Water web site at .
We encourage customers to join us in our efforts to prevent water pollution and protect our most precious natural resource.
All 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.
More information about contaminants and potential health effects can be obtained by calling the EPA Safe Drinking Water Hotline at (800) 426-4791.
The sources of drinking water (both tap and bottled) include rivers, lakes, streams, ponds, reservoirs, springs, and wells. 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.
Contaminants that may be present in source water include:
- Microbial contaminants, such as viruses and bacteria, which may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife.
- Inorganic contaminants, such as salts and metals, which can be naturally occurring or result from urban stormwater runoff, industrial or domestic wastewater discharges, oil and gas production, mining, or farming.
- Pesticides and herbicides, which may come from a variety of sources such as agriculture, urban stormwater runoff, and residential uses.
- Organic chemical contaminants, including synthetic and volatile organic chemicals, which are byproducts of industrial processes and petroleum production, and can also come from gas stations, urban stormwater runoff, agricultural application, and septic systems.
- Radioactive contaminants, which can be naturally occurring or the result of oil and gas production and mining activities.
In order to ensure that tap water is safe to drink, the EPA and DDW prescribe regulations that limit the amount of certain contaminants in water provided by public water systems. FDA regulations establish limits for contaminants in bottled water, which must provide the same protection for public health.
Some people may be more vulnerable to contaminants in drinking water than the general population. Immunocompromised people, such as those with cancer undergoing chemotherapy, those who have undergone organ transplants, and those 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 from their health care providers about drinking water. EPA and Centers for Disease Control and Prevention (CDC) guidelines on appropriate means to lessen the risk of infection by Cryptosporidium and other microbial contaminants are available from the Safe Drinking Water Hotline.
As the issue of lead in water continues to be top of mind for many Americans, Cal Water wants to assure you about the quality of your water. We are compliant with health and safety codes mandating use of lead-free materials in water system replacements, repairs, and new installations. We have no known lead service lines in our systems. We test and treat (if necessary) water sources to ensure that the water delivered to customer meters meets all water quality standards and is not corrosive toward plumbing materials.
The water we deliver to your home meets lead standards. However, if present, elevated levels of lead can cause serious health problems, especially for pregnant women and young children. Lead in drinking water is primarily from materials and components associated with service lines and home plumbing (for example, lead solder used to join copper plumbing, and brass and other lead-containing fixtures).
Cal Water is responsible for providing high-quality drinking water to our customers' meters, but cannot control the variety of materials used in plumbing components. When your water has been sitting for several hours, you can minimize the potential for lead exposure by flushing your tap for 30 seconds to 2 minutes before using water for drinking or cooking.
If you are concerned about lead in your water, you may wish to have your water tested by a certified lab. More information about lead in drinking water can be found on the Safe Drinking Water Hotline or at www.epa.gov/safewater/lead.
In your system, results from our lead monitoring program, conducted in accordance with the Lead and Copper Rule, were below the action level for the presence of lead.
Testing for Lead in Schools
The State of California required that all public schools built before 2010 test for lead in their drinking water by July 1, 2019. We are committed to supporting our school districts' efforts to protect students and ensure that the drinking water at their school sites are below lead limits. We worked with all school districts in our service area that serve kindergarten through 12th grade to develop sampling plans, test samples, and conduct follow-up monitoring, if needed, for corrective actions.
Lead and Copper Rule
The Lead and Copper Rule requires us to test water inside a representative number of homes that have plumbing most likely to contain lead and/or lead solder to determine the presence of lead and copper or any action level exceedance. An action level is the concentration of a contaminant which, when exceeded, triggers corrective actions before it becomes a health concern. If action levels are exceeded, either at a customer's home or system-wide, we work with the customer to investigate the issue and/or implement corrosion control treatment to reduce lead levels.
Lead Service Line Inventory (LSLI)
Protecting our customers' health and safety is our highest priority. As part of this commitment, we have been working to identify and replace any old customer water service lines and fittings that may contain lead. California Senate Bill (SB) 1398 required all water utilities in California to develop an inventory of all distribution service line materials, and submit a list of known service lines to the state by 2018. A list of unknown service lines that may contain lead, along with a plan for replacement, was due to the state by July 1, 2020. Known lines must be replaced as soon as possible.
More information regarding LSLI and specific data for each water system can be found on the state web site.
In Compliance: Does not exceed any applicable MCL, SMCL, or action level, as determined by DDW. For some compounds, compliance is determined by averaging the results for one source over a one-year period.
Level 1 Assessment: A Level 1 assessment is a study of the water system to identify potential problems and determine (if possible) why total coliform bacteria have been found in our water system.
Level 2 Assessment: A Level 2 assessment is a very detailed study of the water system to identify potential problems and determine (if possible) why an E. coli MCL violation has occurred and/or why total coliform bacteria have been found in our water system on multiple occasions.
Maximum Contaminant Level (MCL): The highest level of a contaminant that is allowed in drinking water. Primary MCLs are set as close to the PHGs (or MCLGs) as is economically and technologically feasible. Secondary MCLs (SMCLs) are set to protect the odor, taste, and appearance of drinking water.
Maximum Contaminant Level Goal (MCLG): The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs are set by the U.S. Environmental Protection Agency.
Maximum Residual Disinfectant Level (MRDL): The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.
Maximum Residual Disinfectant Level Goal (MRDLG): The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.
Notification Level (NL) and Response Level (RL): Health-based advisory levels for unregulated contaminants in drinking water. They are used by DDW to provide guidance to drinking water systems.
Primary Drinking Water Standards (PDWS): MCLs and MRDLs for contaminants that affect health along with their monitoring and reporting requirements, and water treatment requirements.
Public Health Goal (PHG): The level of a contaminant in drinking water below which there is no known or expected risk to health. PHGs are set by the California Environmental Protection Agency.
Regulatory Action Level (AL): The concentration of a contaminant which, if exceeded, triggers treatment or other requirements that a water system must follow.
Treatment Technique (TT): A required process intended to reduce the level of a contaminant in drinking water.
Variances and Exemptions: Permissions from the State Water Resources Control Board (State Board) to exceed an MCL or not comply with a treatment technique under certain conditions.
- AL: Action level
- Max: Maximum
- Min: Minimum
- N/A: Not applicable
- NL: Notification level
- NTU: Nephelometric turbidity unit
- ND: Constituent not detected
- pCi/L: Picocuries per liter (a measure of radiation)
- ppb: Parts per billion or micrograms per liter (μg/L)
- ppm: Parts per million or milligrams per liter (mg/L)
- ppq: Parts per quadrillion or picogram per liter (pg/L)
- ppt: Parts per trillion or nanograms per liter (ng/L)
- μS/cm: Microsiemens/centimeter
Cal Water tests your water for a large number of both regulated and unregulated contaminants. This table lists only those contaminants that were detected.
In the table, water quality test results are divided into four major sections: "Primary Drinking Water Standards," "Secondary Drinking Water Standards," "State-Monitored Contaminants with Notification Levels," and "Unregulated Compounds." Primary standards protect public health by limiting the levels of certain constituents in drinking water. Secondary standards are set for substances that don't impact health but could affect the water's taste, odor, or appearance. Some unregulated substances (hardness and sodium, for example) are included for your information.
The State allows us to monitor for some contaminants less than once per year because the concentrations of these contaminants do not change frequently. Some of our data, though representative, are more than one year old.
Our testing equipment is so sensitive, it can detect constituents as small as 1 part per trillion. That is equivalent to 1 inch over 15 million miles.
- DI: Byproduct of drinking water disinfection
- DS: Drinking water disinfectant added for treatment
- EN: Naturally present in the environment
- ER: Erosion of natural deposits
- FE: Human and animal waste
- FL: Water additive that promotes strong teeth; discharge from fertilizer and aluminum factories
- FR: Runoff and leaching from fertilizer use; leaching from septic tanks and sewage
- IC: Internal corrosion of household plumbing systems
- IM: Discharge from industrial manufacturers
- IO: Substances that form ions when in water
- IW: Industrial waste
- OD: Discharges of oil-drilling waste and from metal refineries
- OM: Naturally occurring organic materials
- PG: Discharge from petroleum, glass, and metal refineries; discharge from mines and chemical manufacturers; runoff from livestock lots (feed additive)
- RU: Runoff/leaching from natural deposits
- SO: Soil runoff
- SW: Seawater influence
- VA: Various natural and manmade sources
- WD: Leaching from wood preservatives
- UR: Unregulated constituents with no source listed and that do not have standardized "source of substance" language
Water Quality Table
Primary Drinking Water Standards
|Microbiological||Year Tested||Unit||MCL||PHG (MCLG)||In Compliance||Distribution System-Wide||Source|
|Total coliform||2021||Positive samples||5%||(0)||Yes||0%||EN|
|Fecal coliform and E. coli||2021||Positive samples||1||(0)||Yes||0||FE|
|Radiological||Year Tested||Unit||MCL||PHG (MCLG)||In Compliance||Groundwater||Valley Water||Source|
|Gross alpha particle activity||2013–2021||pCi/L||15||(0)||Yes||ND–3.1||ND||N/A||N/A||ER|
|Inorganic Chemicals||Year Tested||Unit||MCL||PHG (MCLG)||In Compliance||Groundwater||Valley Water||Source|
|Barium||2019–2021||ppm||1||2 (2)||Yes||ND–0.20||ND||N/A||N/A||ER, OD|
|Fluoride||2019–2021||ppm||2||1 (4.0)||Yes||ND–0.18||0.11||ND–0.12||ND||ER, FL|
|Nitrate as N||2021||ppm||10||10 (10)||Yes||1.6–7.7||4.7||ND–0.4||ND||ER, FR|
|Lead and Copper||Year Tested||Unit||AL||PHG (MCLG)||In Compliance||Distribution System-Wide||Source|
|90th Percentile||Samples > AL|
|Copper||2019||ppm||1.3||0.3||Yes||0.27||0 of 31||IC, ER, WD|
|Lead||2019||ppb||15||0.2||Yes||ND||0 of 31||IC, IM, ER|
|Schools that requested lead sampling in 2021: 0|
|Disinfection Byproducts||Year Tested||Unit||MCL||PHG (MCLG)||In Compliance||Distribution System-Wide||Source|
|Range||Highest Annual Average|
|Disinfectants||Year Tested||Unit||MRDL||MRDLG||In Compliance||Distribution System-Wide||Source|
|Surface Water—Turbidity||Year Tested||Unit||MCL||PHG (MCLG)||In Compliance||Valley Water||Source|
|Highest Level||Lowest Monthly
|Surface Water—TOC||Year Tested||Unit||MCL||PHG (MCLG)||In Compliance||Valley Water||Source|
|Total organic carbon (TOC)||2021||ppm||TT||N/A||Yes||1.5–2.3||1.9||VA|
Secondary Drinking Water Standards
|Chemical||Year Tested||Unit||SMCL||PHG (MCLG)||In Compliance||Groundwater||Valley Water||Source|
|Specific conductance||2019–2021||US||1600||N/A||Yes||560–960||756||604–684||652||SW, IO|
|Total dissolved solids||2019–2021||ppm||1000||N/A||Yes||340–590||451||362–392||378||RL|
State Monitored Contaminants with Notification Levels
|Chemical||Year Tested||Unit||NL||PHG (MCLG)||In Compliance||Groundwater||Valley Water||Source|
Unregulated Contaminant Monitoring Rule (UCMR)
|Chemical||Year Tested||Unit||MCL||PHG (MCLG)||In Compliance||Groundwater||Valley Water||Source|
|Brominated haloacetic acids||2019||ppb||N/A||N/A||N/A||ND–25||15||N/A||N/A||UR|
|Haloacetic acids and brominated haloacetic acids||2019||ppb||N/A||N/A||N/A||ND–32||21||N/A||N/A||UR|
|Chemical||Year Tested||Unit||MCL||PHG (MCLG)||In Compliance||Groundwater||Valley Water||Source|
1 This table reflects changes in drinking water regulatory requirements during 2021. These revisions add the requirements of the federal Revised Total Coliform Rule, effective since April 1, 2016, to the existing state Total Coliform Rule. The revised rule 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). The EPA anticipates greater public health protection as the 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. The state Revised Total Coliform Rule became effective July 1, 2021.
2 This means a routine sample and a repeat sample are total coliform-positive, and one of these is also E. coli-positive.
3 Valley Water supply data reported is from 2021. Valley Water delivered to our system during 2021 may have been from SFPUC via an SFPUC-Valley Water intertie.
4 The average nitrate level in our sources was 4.7 ppm, with a maximum level of 7.7 ppm. We are closely monitoring the nitrate levels. Nitrate in drinking water at levels above 10 ppm is a health risk for infants of less than six months of age. Such nitrate levels in drinking water can interfere with the capacity of the infant's blood to carry oxygen, resulting in a serious illness; symptoms include shortness of breath and blueness of the skin. Nitrate levels above 10 ppm may also affect the ability of the blood to carry oxygen in other individuals, such as pregnant women and those with certain specific enzyme deficiencies. If you are caring for an infant or you are pregnant, you should seek advice from your health care provider.
5 For surface water systems, the treatment technique dictates that the turbidity level of the filtered water be less than or equal to 0.3 NTU in 95% of measurements taken each month and not exceed 1 NTU at any time. Turbidity is a measurement of cloudiness of water. We monitor it because it is a good indicator of the effectiveness of our filtration system.
6 TOC has no health effects; however, TOC provides a medium for the formation of disinfection byproducts. These byproducts include trihalomethanes and haloacetic acids. The treatment technique dictates that a removal ratio of 1 or higher must be achieved. Drinking water containing these byproducts in excess of the MCL may lead to adverse health effects such as liver, kidney, or nervous system problems, and may lead to an increased risk of cancer. Concerns regarding disinfection byproducts are based upon exposure over many years.
7 The previous MCL of 0.010 mg/L (10 ppb) for hexavalent chromium was withdrawn on September 11, 2017, and there is currently no MCL in effect. A draft MCL of 10 ppb was released in 2022.
A full-color, printable version of this report in PDF format is also available.
If you have any questions about your water quality table, please Contact Us.