District: Los Altos Suburban
System: Los Altos Suburban
A printable version of this report is also available.
Welcome
Since 1926, Cal Water has been committed to providing a reliable supply of safe, clean water to our customers and communities. As water quality regulations have become more stringent, we have added or adjusted treatment to ensure the water we deliver meets or surpasses all standards, because protecting our customers' health and safety is our highest priority.
In this system in 2022, we conducted 11,031 tests on 1,816 water samples for 203 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 treating and testing water. 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 2022 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 office, or online at www.calwater.com. 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.
Sincerely,
Dawn Smithson, District Manager, Los Altos Suburban District
[Los Altos Suburban District | 949 "B" Street, Los Altos, CA 94024 | (650) 917-0152]
Action Items
There were no significant issues in your water system in 2022, and we have no recommended action items for our customers in this area.
Contact Us
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.
Chloramines
Chloramines are most commonly formed when ammonia is added to chlorine. They are used as a disinfectant to treat your drinking water, and provide long-lasting disinfection as water moves through pipes to consumers.
Water Resource Sustainability
Cal Water helps our customers conserve water by offering programs and incentives to reduce indoor and outdoor water use, develop more efficient habits, and educate the next generation about the importance of managing water resources sustainably. We also continue to invest diligently in our infrastructure to reduce the amount of water lost to pipeline leaks and, in 2022, completed an updated assessment of the impacts of climate change on water supply and demand. Whether in wet or dry years, it's important that we make saving water every day a way of life. Using water wisely will ensure that we have enough water in periods of drought and for generations to come.
Visit www.calwater.com/conservation for details.
The Water Quality Lab
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.
Cross-Connection Control
To ensure that the high-quality water we deliver is not compromised in the distribution system, Cal Water has a robust cross-connection control program in place. Cross-connection control is critical to ensuring that activities on customers' properties do not affect the public water supply. Our cross-connection control specialists ensure that all of the existing backflow prevention assemblies are tested annually, assess all connections, and enforce and manage the installation of new commercial and residential assemblies.
Backflow can occur when certain pressure conditions exist either in our distribution system or within the customer's plumbing, so our customers are our first line of defense. A minor home improvement project—without the proper protections—can create a potentially hazardous situation, so careful adherence to plumbing codes and standards will ensure the community's water supply remains safe. Please be sure to utilize the advice or services of a qualified plumbing professional.
Many water-use activities involve substances that, if allowed to enter the distribution system, would be aesthetically displeasing or could even present health concerns. Some common cross-connections are:
- Garden hoses connected to a hose bib without a simple hose-type vacuum breaker (available at a home improvement store)
- Improperly installed toilet tank fill valves that do not have the required air gap between the valve or refill tube
- Landscape irrigation systems that do not have the proper backflow prevention assembly installed on the supply line
The list of materials that could potentially contaminate the water system is vast. According to the United States Environmental Protection Agency (EPA), a wide variety of substances have contaminated drinking water systems throughout the country as a result of poor cross-connection control. Examples include:
- Antifreeze from a heating system
- Lawn chemicals from a garden hose or sprinkler head
- Blue water from a toilet tank
- Carbonated water from a soda dispenser
Customers must ensure that all plumbing is in conformance with local plumbing codes. Additionally, state law requires certain types of facilities to install and maintain backflow prevention assemblies at the water meter. Cal Water's cross-connection control staff will determine whether you need to install a backflow prevention assembly based on water uses at your location.
DWSAPP
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 of contaminants and disinfection of the water. For additional information, visit the Valley Water web site at www.valleywater.org.
We encourage customers to join us in our efforts to prevent water pollution and protect our most precious natural resource.
2022 Results
Fluoride
State law requires Cal Water to add fluoride to drinking water if public funding is available to pay for it, and it is a practice endorsed by the American Medical Association and the American Dental Association to prevent tooth decay. In this area, low levels of fluoride occur naturally, and Cal Water doesn't add any to the water supply. Show the table in this report to your dentist to see if he or she recommends giving your children fluoride supplements.
More information about fluoridation, oral health, and related issues can be found on the DDW web site.
For general information on water fluoridation, visit us online at www.calwater.com/waterquality/fluoride.
Water Hardness
Hardness is a measure of the magnesium, calcium, and carbonate minerals in the water. Water is considered soft if its hardness is less than 75 parts per million (ppm), moderately hard at 75 to 150 ppm, hard between 150 and 300 ppm, and very hard at 300 ppm or higher.
Hard water is generally not a health concern, but it can have an impact on how well soap lathers and is significant for some industrial and manufacturing processes. Hard water may also lead to mineral buildup in pipes or water heaters.
Some people with hard water opt to buy a water softener for aesthetic reasons; however, some water softeners add salt to the water, which can cause problems at wastewater treatment plants. Additionally, people on low-sodium diets should be aware that some water softeners increase the sodium content of the water.
For more information on water hardness, visit www.calwater.com/video/hardness.
Possible Contaminants
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, lake, 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 activities. Prior to entering the distribution system, source water with constituents over maximum contaminant levels is treated to reduce levels to meet standards set by public health experts.
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 compounds, which are byproducts of industrial processes and petroleum production, and can also come from gas stations, urban stormwater runoff, agricultural applications, 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 contaminants. 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.
About Lead
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 properties' 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 regulatory 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.
For more information, please see our Testing for Lead in Schools web page. For specific information regarding local school data, see the state web portal.
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 lead 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.
PFAS
Per- and polyfluoroalkyl substances (PFAS) are manmade compounds that have been used to make carpets, clothing, fabrics for furniture, paper packaging for food, and other materials (e.g., cookware) that are resistant to water, grease, or stains. These compounds are also used for firefighting at airfields, which is one way they have found their way into groundwater in certain areas.
In March 2023, EPA issued a proposed national primary drinking water regulation for certain PFAS. The proposed regulation calls for a maximum containment level for PFOS and PFOA of 4 ppt each. Four additional PFAS—PFNA, PFHxS, PFBS, and GenX—would have a combined hazard index limit of 1.0; the hazard index calculation would determine if the levels of these PFAS as a mixture pose a potential risk.
Knowing that these were constituents of emerging concern, Cal Water proactively tested active sources in our systems for these PFAS years ago. Although not required, we believed it was the right thing to do. In any areas across the state where detections were above levels at which DDW recommends water suppliers take action (the response level), we took the affected sources out of service until treatment was or can be installed.
None of our active water sources have levels of these six PFAS compounds over current California response levels. The response level, which is the level at which a water system should make operational changes to reduce the concentration of a compound, is set with a margin of protection for all people (including sensitive populations) over a lifetime of exposure. We are currently evaluating the impact of the proposed regulation on our systems and any treatment required should the proposed regulation be adopted as is.
Additionally, we believe a comprehensive approach is needed to properly address the situation. We urged the EPA to establish a consistent, science-based standard as quickly as feasible, and strongly supported state legislation that will prohibit the sale and use of certain products that contain PFAS, require the certification of accurate testing methods for PFAS, and establish a publicly accessible database that houses the sources of PFAS entering water supplies. We have also filed a lawsuit to hold PFAS manufacturers responsible—and ultimately prevent our customers from bearing the costs of treatment, to the extent possible—and are pursuing grants where available to further offset customer cost impacts.
Studies indicate that long-term exposure to PFAS over certain levels could have adverse health effects, including developmental effects to fetuses during pregnancy or infants; cancer; or impacts on liver, immunity, thyroid, and other functions. Potential health effects related to PFAS are still being studied, and research is still evolving on this issue.
While we are doing our part to treat the water and meet the standards public health experts have set, it's important that our population as a whole focuses on being good stewards of the environment and takes steps to prevent impacting the water supply.
More information on PFAS is available on the DDW web site.
Key Definitions
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 the 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 the 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, MRDLs, and TTs for contaminants that affect health along with their monitoring, reporting, 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 without regard to technological or economic feasibility.
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.
Standard Abbreviations
- 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
Table Introduction
Every year, Cal Water performs hundreds of thousands of tests to monitor the quality of our water. If any contaminants are detected, they are included in this annual water quality report. However, most of the contaminants we test for are not detected, so they are not listed.
See the Potential Contaminants web page for a complete list of contaminants we test for.
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.
Substance Sources
- 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)
- PR: Inorganic chemical used in solid rocket propellant, fireworks, explosives, flares, matches, and a variety of industries; usually gets into drinking water as a result of environmental contamination from historic aerospace or other industrial operations that used or use, store, or dispose of perchlorate and its salts
- 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
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
2022 Water Quality
Primary Drinking Water Standards |
||||||||||
| Microbiological | Year Tested | Unit | MCL | PHG (MCLG) | In Compliance | Distribution System-Wide | Source | |||
| Highest Monthly | ||||||||||
| Fecal coliform and E. coli | 2021 | Positive samples | 01 | (0) | Yes | 0 | FE | |||
| Radiological | Year Tested | Unit | MCL | PHG (MCLG) | In Compliance | Groundwater | Valley Water2 | Source | ||
| Range | Average | Result | ||||||||
| Gross alpha particle activity | 2022 | pCi/L | 15 | (0) | Yes | ND | ND | 3.3 | ER | |
| Uranium | 2014–2022 | pCi/L | 20 | 0.43 (0) | Yes | ND–1.4 | ND | 1.3 | ER | |
| Inorganic Chemicals | Year Tested | Unit | MCL | PHG (MCLG) | In Compliance | Groundwater | Valley Water | Source | ||
| Range | Average | Range | Average | |||||||
| Barium | 2020–2022 | ppm | 1 | 2 (2) | Yes | ND–0.20 | ND | N/A | N/A | ER, OD |
| Fluoride | 2020–2022 | ppm | 2 | 1 (4.0) | Yes | ND–0.16 | ND | ND–0.13 | ND | ER, FL |
| Nitrate as N3 | 2022 | ppm | 10 | 10 (10) | Yes | 1.2–7.9 | 4.4 | ND–0.7 | 0.4 | ER, FR |
| Perchlorate | 2020–2022 | ppb | 6 | 1 | Yes | ND–3.2 | ND | N/A | N/A | PR |
| Selenium | 2020–2022 | ppb | 50 | 30 (50) | Yes | ND–5.6 | ND | N/A | N/A | PG, ER |
| Lead and Copper | Year Tested | Unit | AL | PHG (MCLG) | In Compliance | Distribution System-Wide | Source | |||
| 90th Percentile | Samples > AL | |||||||||
| Copper | 2022 | ppm | 1.3 | 0.3 | Yes | 0.39 | 0 of 35 | IC, ER, WD | ||
| Lead | 2022 | ppb | 15 | 0.2 | Yes | ND | 0 of 35 | IC, IM, ER | ||
| Disinfection Byproducts | Year Tested | Unit | MCL | PHG (MCLG) | In Compliance | Distribution System-Wide | Source | |||
| Range | Highest Annual Average | |||||||||
| Haloacetic acids | 2022 | ppb | 60 | N/A | Yes | ND–29 | 21 | DI | ||
| Total trihalomethanes (TTHM)4 | 2022 | ppb | 80 | N/A | Yes | ND–83 | 70 | DI | ||
| Disinfectants | Year Tested | Unit | MRDL | MRDLG | In Compliance | Distribution System-Wide | Source | |||
| Range | Average | |||||||||
| Chloramine | 2022 | ppm | 4 | 4 | Yes | ND–2.8 | 1.4 | DS | ||
| Surface Water—Turbidity | Year Tested | Unit | MCL | PHG (MCLG) | In Compliance | Groundwater | Valley Water | Source | ||
| Highest Level | Lowest Monthly Percent Removal | Highest Level | Lowest Monthly Percent Removal | |||||||
| Turbidity5 | 2022 | NTU | TT | N/A | Yes | — | — | 0.28 | 100% | SO |
| Surface Water—TOC | Year Tested | Unit | MCL | PHG (MCLG) | In Compliance | Groundwater | Valley Water | Source | ||
| Range | Average | Range | Average | |||||||
| Total organic carbon (TOC)6 | 2022 | ppm | TT | N/A | Yes | — | — | 1.5–3.0 | 2.3 | VA |
Secondary Drinking Water Standards |
||||||||||
| Chemical | Year Tested | Unit | SMCL | PHG (MCLG) | In Compliance | Groundwater | Valley Water | Source | ||
| Range | Average | Range | Average | |||||||
| Chloride | 2020–2022 | ppm | 500 | N/A | Yes | 32–88 | 53 | 71–95 | 83 | RU, SW |
| Color | 2020–2022 | UNITS | 15 | N/A | Yes | ND–15 | 2.1 | ND–5 | 2 | OM |
| Odor7 | 2020–2022 | T.O.N. | 3 | N/A | Yes | ND | ND | 1 | 1 | OM |
| Specific conductance | 2020–2022 | μS/cm | 1600 | N/A | Yes | 430–960 | 730 | 562–626 | 581 | SW, IO |
| Sulfate | 2020–2022 | ppm | 500 | N/A | Yes | 4.2–88 | 36 | 50–74 | 65 | RU, IW |
| Total dissolved solids | 2020–2022 | ppm | 1000 | N/A | Yes | 250–590 | 431 | 308–362 | 335 | RU |
| Turbidity (groundwater) | 2020–2022 | NTU | 5 | N/A | Yes | ND–1.3 | 0.39 | 0.01–0.28 | 0.06 | SO |
State-Regulated Contaminants with Notification Levels |
||||||||||
| Chemical | Year Tested | Unit | NL | PHG (MCLG) | In Compliance | Groundwater | Valley Water | Source | ||
| Range | Average | Range | Average | |||||||
| Boron | 2016–2018 | ppm | 1 | N/A | Yes | ND–0.11 | ND | 126–182 | 163 | UR |
| Chlorate | 2014–2016 | ug/L | 800 | N/A | Yes | 64–220 | 137 | 96–221 | 150 | UR |
| Vanadium | 2022 | ppb | 50 | N/A | Yes | 4.3–10 | 7.4 | 2–3 | 2 | UR |
Unregulated Contaminant Monitoring Rule (UCMR) |
||||||||||
| Chemical | Year Tested | Unit | MCL | PHG (MCLG) | In Compliance | Groundwater | Valley Water | Source | ||
| Range | Average | Range | Average | |||||||
| HAA5 (DBAA, DCAA, MBAA, MCAA, and TCAA) | 2019 | ppb | 60 | N/A | N/A | ND–14 | 8.4 | N/A | N/A | UR |
| HAA6Br (BCAA, BDCAA, DBAA, CDBAA, MBAA, and TBAA) | 2019 | ppb | N/A | N/A | N/A | ND–25 | 15 | N/A | N/A | UR |
| HAA9 (BCAA, BDCAA, CDBAA, DBAA, DCAA, MBAA, MCAA, TBAA, and TCAA) | 2019 | ppb | N/A | N/A | N/A | ND–32 | 21 | N/A | N/A | UR |
Unregulated Compounds |
||||||||||
| Chemical | Year Tested | Unit | MCL | PHG (MCLG) | In Compliance | Groundwater | Valley Water | Source | ||
| Range | Average | Range | Average | |||||||
| Alkalinity (total) | 2020–2022 | ppm | N/A | N/A | N/A | 110–310 | 252 | 61–78 | 73 | UR |
| Calcium | 2018–2022 | ppm | N/A | N/A | N/A | 23–140 | 85 | 17–25 | 23 | UR |
| Hexavalent chromium8 | 2014–2022 | ppb | N/A | 0.02 | N/A | ND–2.6 | 1.3 | N/A | N/A | UR |
| Hardness (total) | 2020–2022 | ppm | N/A | N/A | N/A | 89–470 | 319 | 92–122 | 114 | UR |
| Potassium | 2020–2022 | ppm | N/A | N/A | N/A | ND–1.2 | 0.07 | 3.6–4.6 | 4.1 | UR |
| Magnesium | 2020–2022 | ppm | N/A | N/A | N/A | 8.0–41 | 26 | 12–15 | 14 | UR |
| Sodium | 2020–2022 | ppm | N/A | N/A | N/A | 21–53 | 33 | 65–79 | 71 | UR |
| pH | 2022 | Units | N/A | N/A | N/A | 6.8–9.0 | 7.6 | 7.5–8.0 | 7.8 | UR |
1 Exceeded if routine and repeat samples are total coliform-positive and either is E. coli-positive, the system fails to take repeat samples following an E. coli-positive routine sample, or the system fails to analyze a total coliform-positive repeat sample for E. coli.
2 Valley Water supply data reported is from 2022. Valley Water deliveries to our system during 2022 may have been from SFPUC via the SFPUC-Valley Water intertie.
3 The average nitrate level was 4.4 ppm, with a maximum level of 7.9 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 an 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.
4 The average locational running annual average (LRAA) for TTHM levels was 70 ppb, with a maximum level of 83 ppb. The MCL is calculated using the LRAA, the average of sample analytical results for samples taken at a particular monitoring location during the previous four calendar quarters. Some people who drink water containing trihalomethanes in excess of the MCL over many years may experience liver, kidney, or central nervous system problems, and may have an increased risk of getting cancer.
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 four odor samples Valley Water collected in 2022 were found to be 1 T.O.N.
8 There is currently no MCL in effect for hexavalent chromium. The state recommends that any hexavalent chromium results above the detection limit of 1 ppb still be reported.
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