Stockton 2022 Water Quality Report

District: Stockton
System: Stockton

A printable version of this report is also available.


RaindropsSince 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 26,999 tests on 3,728 water samples for 235 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 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 to ensure you receive important emergency and other information.

Jeremiah Mecham, District Manager, Stockton District

[Stockton District | 1505 East Sonora Street, Stockton, CA 95205 | (209) 547-7900]

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 (209) 547-7900 or through the Contact Us page.

Your Water System

Water treatment plantCal Water has provided high-quality water utility services in Stockton since 1927. To meet the needs of our customers, we use a combination of local groundwater and water purchased from the Stockton East Water District, which is obtained from the New Melones and New Hogan Reservoirs. The Stockton system includes 25 active wells, 13 booster pumps, and 8 storage tanks.

Our 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.


Chlorination is the addition of chlorine to drinking water systems. It is the most common type of drinking water disinfection, killing bacteria, viruses, and other microorganisms that cause disease or immediate illness. Chlorine is effective and continues to keep water safe as it travels through pipelines to the consumer's tap.

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 for details.

The Water Quality Lab

Laboratory equipment

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.


Dishes in dish water

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. All reports are available for viewing or copying at our office.

The water sources in your district are considered most vulnerable to the following activities associated with contaminants detected in the water supply:

  • Sewer collection systems
  • Agricultural drainage
  • Irrigated crops
  • Fertilizer/pesticide/herbicide applications
  • Pesticide/fertilizer/petroleum storage and transfer areas
  • Appliance/electronic repair
  • Junk/scrap/salvage yards
  • Machine shops
  • Metal plating/finishing/fabricating
  • Golf courses
  • Septic tanks
  • Historic railroad right-of-ways
  • Chemical/petroleum processing or storage
  • Farm chemical distributor/application service
  • Farm machinery repair
  • Automobile body and repair shops
  • Fleet/truck/bus terminals
  • Car washes
  • Road right-of-ways
  • Wells (water supply)
  • Parks
  • RV parks
  • Medical/dental offices/clinics
  • Hospitals
  • Lumber processing/manufacturing
  • Electrical/electronic manufacturing
  • Hardware/lumber/parts stores

The water sources are considered most vulnerable to the following activities, for which no associated contaminant has been detected:

  • Gas stations
  • Underground storage tanks (confirmed leaking tanks)
  • Dry cleaners
  • Railroad yards/maintenance/fueling areas
  • Recreational areas (surface water source)
  • Wells (agricultural)
  • Photo processing/printing
  • Storm drain discharge points

We encourage customers to join us in our efforts to prevent water pollution and protect our most precious natural resource.

2022 Results


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

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

Possible Contaminants

Water pouring into a glassAll 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

Water reaching to the horizonAs 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

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.


Water pitcher and glassesPer- 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

Woman drinking waterIn 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

Laboratory equipmentEvery 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
  • MD: Discharge from metal-degreasing sites and other factories
  • OC: Runoff from orchards; glass and electronics production waste
  • OD: Discharges of oil-drilling waste and from metal refineries
  • OM: Naturally occurring organic materials
  • RU: Runoff/leaching from natural deposits
  • RS: Residue from some surface water treatment processes
  • SO: Soil runoff
  • SP: Discharge from steel and pulp mills and chrome plating
  • 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 2022 Positive Samples 01 (0) Yes 0 FE
Radiological Year Tested Unit MCL PHG (MCLG) In Compliance Groundwater SEWD2 Source
Range Average Range Average
Gross alpha particle activity 2015–2022 pCi/L 15 (0) Yes ND–12 ND ND–3.24 ND ER
Uranium 2015–2022 pCi/L 20 0.43 (0) Yes ND–5.7 1.9 N/A N/A ER
Inorganic Chemicals Year Tested Unit MCL PHG (MCLG) In Compliance Groundwater SEWD Source
Range Average Range Result
Arsenic3 2020–2022 ppb 10 0.004 (0) Yes ND–7.4 4.3 N/A ND ER, OC
Barium 2020–2022 ppm 1 2 (2) Yes ND–0.29 0.15 N/A ND ER, OD
Chromium (total) 2020–2022 ppb 50 (100) Yes ND–10 ND N/A ND ER, SP
Fluoride 2020–2022 ppm 2 1 (4.0) Yes ND–0.11 ND N/A ND ER, FL
Nitrate as N4 2022 ppm 10 10 (10) Yes ND–8.3 3.3 N/A ND ER, FR
Lead and Copper Year Tested Unit AL PHG (MCLG) In Compliance Distribution System-Wide Source
90th Percentile Samples > AL
Copper 2021 ppm 1.3 0.3 Yes ND 0 of 50 IC, ER, WD
Lead 2021 ppb 15 0.2 Yes ND 0 of 50 IC, IM, ER
Volatile Organic Compounds Year Tested Unit MCL PHG (MCLG) In Compliance Groundwater SEWD Source
Range Average Range Average
Trichloroethylene (TCE) 2020–2022 ppb 5 1.7 (0) Yes ND–0.74 ND N/A ND MD
Disinfection Byproducts Year Tested Unit MCL PHG (MCLG) In Compliance Distribution System-Wide Source
Range Highest Annual Average
Total haloacetic acids (THAA) 2022 ppb 60 N/A Yes 5.9–20 16 DI
Total trihalomethane (TTHM) 2021–2022 ppb 80 N/A Yes 16–73 63 DI
Disinfectants Year Tested Unit MRDL MRDLG In Compliance Distribution System-Wide Source
Range Average
Free chlorine 2022 ppm 4 4 Yes ND–1.5 0.63 DS
SEWD—Turbidity and TOC Year Tested Unit MCL PHG (MCLG) In Compliance Groundwater SEWD Source
Highest Level Lowest Monthly Percent Highest Level Lowest Monthly Percent
Turbidity5 2022 NTU TT N/A Yes 0.11 100% VA
Year Tested Unit MCL PHG (MCLG) In Compliance Highest Level Lowest Monthly Percent Removal Ratio Highest Level Lowest Monthly Percent Removal Ratio Source
Total organic carbon (TOC)6 2022 ppm TT N/A Yes 3.0 0.83 VA

Secondary Drinking Water Standards

Contaminants Year Tested Unit SMCL PHG (MCLG) In Compliance Groundwater SEWD Source
Range Average Range Result
Aluminum 2020–2022 ppb 200 600 Yes ND–84 ND N/A 70 ER, RS
Chloride 2020–2022 ppm 500 N/A Yes 7.1–29 17 N/A 9 RU, SW
Color 2018–2022 UNITS 15 N/A Yes ND–5.0 ND N/A ND OM
Specific conductance 2020–2022 µS/cm 1600 N/A Yes 250–640 432 N/A 223 SW, IO
Iron 2020–2022 ppb 300 N/A Yes ND–130 ND N/A ND RU, IW
Manganese7 2020–2022 ppb 50 N/A Yes ND–62 ND N/A ND RU
Odor 2018–2022 T.O.N. 3 N/A Yes ND–1.3 ND N/A ND OM
Sulfate 2020–2022 ppm 500 N/A Yes 3.4–34 19 N/A 18.9 RU, IW
Total dissolved solids 2020–2022 ppm 1000 N/A Yes 170–400 281 N/A 150 RU
Turbidity (groundwater) 2018–2022 NTU 5 N/A Yes ND–0.79 0.20 N/A N/A SO

State-Regulated Contaminants with Notification Levels

Contaminants Year Tested Unit NL PHG (MCLG) In Compliance Groundwater SEWD Source
Range Average Range Average
Dichlorodifluoromethane (Freon 12) 2020–2022 ppb 1000 N/A Yes ND–1.5 ND N/A ND UR
Perfluorhexanesulfonic acid (PFHxS)8 2020–2022 ppt 3 N/A Yes ND–4.8 0.24 N/A ND UR
Perfluorooctanesulfonic acid (PFOS)1 2020–2022 ppt 6.5 N/A Yes ND–9.0 1.2 N/A ND UR
Vanadium 2020–2022 ppb 50 N/A Yes ND–35 20 N/A ND UR

Unregulated Contaminant Monitoring Rule (UCMR)

Constituents Year Tested Unit MCL PHG (MCLG) In Compliance Groundwater SEWD Source
Range Average Range Average
Germanium 2019–2020 ppb N/A N/A N/A ND–2.5 0.35 UR
Haloacetic acids five 2019 ppb N/A N/A N/A ND–4.1 ND UR
Haloacetic acids six brominated 2019 ppb N/A N/A N/A ND–4.0 ND UR
Haloacetic acids nine 2019 ppb N/A N/A N/A 9.2–25 17 UR

Unregulated Compounds

Constituents Year Tested Unit MCL PHG (MCLG) In Compliance Groundwater SEWD Source
Range Average Range Result
Alkalinity (total) 2020–2022 ppm N/A N/A N/A 110–230 166 N/A 70 UR
Calcium 2018–2022 ppm N/A N/A N/A 5.5–57 34 N/A 18 UR
Hexavalent chromium9 2014–2020 ppb N/A 0.02 N/A ND–8.3 1.9 N/A N/A UR
Hardness (total) 2018–2022 ppm N/A N/A N/A 21–270 149 N/A 73.7 UR
Potassium 2018–2022 ppm N/A N/A N/A 0.71–7.6 5.0 N/A 2 UR
Magnesium 2018–2022 ppm N/A N/A N/A 1.8–30 16 N/A 7 UR
Sodium 2018–2022 ppm N/A N/A N/A 5.6–41 23 N/A 14 UR
pH 2019–2022 Units N/A N/A N/A 6.9–8.8 8.0 N/A 8.1 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 A part of Stockton's water supply is purchased from Stockton East Water District (SEWD).

3 The average arsenic level was 4.3 ppb, with a maximum level of 7.4 ppb. While your drinking water meets the federal and state standards for arsenic, it does contain low levels of arsenic. The arsenic standards balance the current understanding of arsenic's possible health effects against the costs of removing arsenic from drinking water. The EPA continues to research the health effects of low levels of arsenic, which is a mineral known to cause cancer in humans at high concentrations and is linked to other health effects, such as skin damage and circulatory problems.

4 The average nitrate level was 3.3 ppm, with a maximum level of 8.3 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.

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 the measurements taken each month and not exceed 1 NTU at any time. Turbidity is a measurement of the 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 In one sample in the Stockton groundwater system, manganese exceeded the SMCL of 50 ppb in February 2022. A confirmation sample was taken and confirmed to be non-detect. Compliance with the SMCL is based a running annual average, which was less then the SMCL. We are monitoring the levels to ensure we do not exceed the SMCL running annual average. The SMCL was set to protect you against unpleasant aesthetic effects, such as color, taste, odor, and the staining of plumbing fixtures and clothing when washed. Exceeding the SMCL does not pose a health risk.

8 Per-and polyfluoroalkyl substances (PFAS) is a broad class of chemicals, which includes perfluorooctanic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorobutanesulfonic acid (PFBS), and perfluorohexanesulfonic acid (PFHxS). NLs have been established for these four compounds. NLs are non-regulatory, health-based advisory levels established for constituents that may be candidates for regulation in the future. Studies indicate that long-term exposure to PFOS/PFOA/PFBS/PFHxS over certain levels could have adverse health effects, including developmental effects to fetuses during pregnancy or breastfed infants; cancer; or liver, immunity, thyroid, and other effects. Cal Water is working closely with DDW and EPA to conduct extensive monitoring and have identified the best available treatment technology for treatment of PFAS.

9 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. The state recommends that any hexavalent chromium results above the detection limit of 1 ppb still be reported.

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