The Irvine Ranch Water District 2026 Water Quality Report includes water quality test results and reporting from 2025. As in years past, we are proud to report that your water passed every test and met or exceeded every quality standard. Learn more at IRWD.com/waterquality.
Every year, Irvine Ranch Water District provides an annual Water Quality Report, sharing information on the safety and quality of its drinking water. We safeguard our water supply year-round to ensure that your drinking water is clean, tasty and high-quality. IRVINE RANCH WATER DISTRICT 2026 Water Quality Report
The Irvine Ranch Water District 2026 Water Quality Report includes water quality test results and reporting from 2025. As in years past, we are proud to report that your water passed every test and met or exceeded every quality standard.
At a glance: Your Water Quality Report • Your drinking water is continually tested and safe straight from the tap. • IRWD has a state-of-the-art and state-certified Water Quality Laboratory — one of the best-equipped labs in Southern California. • IRWD is leading the way on water quality testing and tests its water for many more chemicals than required by the state and federal government, including unregulated metals, pesticides and volatile organic compounds. Drink up! In 2025, IRWD drinking water met or exceeded all state and federal standards. The U.S. Environmental Protection Agency (EPA) and the State Water Resources Control Board’s Division of Drinking Water (DDW) establish and enforce drinking water quality standards to ensure public health. IRWD and its regional water suppliers (Orange County Water District and Metropolitan Water District of Southern California) frequently go beyond what is required by these federal and state regulatory agencies — monitoring your water from source to tap for regulated and unregulated elements.
Questions about your water? Contact Regulatory Compliance Manager Lori Rigby at 949-453-5344 or rigby@IRWD.com. A copy of this report is available at IRWD.com/waterquality , where you’ll also find information on IRWD’s drinking water quality monitoring. Go to IRWD.com for information on water reliability, customer support and services, and additional resources.
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IRWD Water Quality Report 2026
Providing safe, clean drinking water — day in and day out Diversity of supply
Water hardness and other aesthetics Water hardness refers to naturally occurring mineral content, mostly calcium and magnesium, which are essential for health and found in all water sources in varying amounts. The white deposits sometimes left by hard water on fixtures or cookware can be removed with a simple vinegar solution, and hard water does not pose a threat to human health. Because water sources vary and are a blend of various sources including local groundwater, local surface water, and imported water, you may notice a difference in the taste or hardness (mineral content) of the water at different times of year. None of these factors affect the safety of your water. Having multiple sources of water is beneficial for IRWD customers.
IRWD has meticulously diversified its water supply and is not dependent upon only one source of water. Your drinking water is a blend of local groundwater, groundwater from the Orange County Groundwater Basin managed by the Orange County Water District (OCWD), and to a lesser degree surface water imported by Metropolitan Water District of Southern California (MWD), which comes from the State Water Project and the Colorado River Aqueduct. IRWD also has a local watershed that feeds rainwater to Irvine Lake, which is used as a surface water source. Local water sources keep costs lower for our customers and significantly increase the overall reliability and resiliency of your water supply. In managing these various water sources, IRWD will sometimes switch water sources or blend them based on availability, local geography, treatment needs, time of the year and to assist other partner agencies. Recycled water is another important water source. While not used for drinking, it significantly reduces demand for drinking water. IRWD has been recycling highly treated wastewater since 1967, and it’s now used to irrigate landscaping, flush toilets in large commercial buildings and support industrial functions like cooling towers. Using recycled water for these purposes is important because every gallon of recycled water saves a gallon of high-quality drinking water for you, our customers.
IRWD Water Quality Report 2026 | Page 3
IRVINE RANCH WATER DISTRICT WATER SOURCES
Where does your water come from? IRWD water comes from local groundwater, recycled water, local surface water (rainwater capture), and from imported water from Northern California and the Colorado River. Recycled water is not used for drinking but is an important water source that reduces demand for drinking water.
Shasta Lake
Lake Oroville
SACRAMENTO- SAN JOAQUIN RIVER DELTA
SACRAMENTO
SAN FRANCISCO
STATE WATER PROJECT (imported water)
GROUNDWATER BANKING
COLORADO RIVER AQUEDUCT (imported water)
PACIFIC OCEAN
LOS ANGELES
Lake Mathews
LOCAL GROUNDWATER
ORANGE COUNTY IRWD SERVICE AREA
SAN DIEGO
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IRWD Water Quality Report 2026
Tap water vs. bottled water Tap water is regulated by the U.S. Environmental Protection Agency (EPA) under the Safe Drinking Water Act, while bottled water is regulated by the Food and Drug Administration (FDA). The EPA requires tap water to be tested more frequently than bottled water using state-certified laboratories. Public water systems are required to provide annual reports, and the EPA enforces regulations through frequent testing and inspections. The FDA does not have the same rigorous certified testing requirements for bottled water. What does all this mean? The next time you need to quench your thirst, do so confidently and safely with IRWD tap water. Grab a glass of water straight from your tap and drink up! Commitment to scientific innovation IRWD is proud to have a state-of-the-art and state-certified Water Quality Laboratory — one of the best-equipped water labs in Southern California — right in Irvine, on-site at IRWD’s Operations Center. A key objective of IRWD’s laboratory is to analyze and report precise, reliable data for regulatory monitoring and reporting, process control and research projects — meaning that every day, bright, analytical minds are hard at work in our lab to make sure your drinking water meets or exceeds state and federal standards.
Water Quality staff continually monitors the water supply to ensure drinking water is safe and reliable. • IRWD’s lab is accredited in 13 different fields of testing that include more than 300 analytes. This allows the Water Quality team to turn around test results faster and more efficiently. • On-site lab instrumentation can identify and measure substances in the low parts-per-trillion (ppt) range. This is akin to identifying one drop of water in 20 Olympic-sized swimming pools. • IRWD is leading the way in water quality testing.
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IRWD Water Quality Report 2026
Understanding drinking water and water quality testing
The sources of drinking water (both tap and bottled water) 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 from human activity.
In order to ensure that tap water is safe to drink, the EPA and the State Water Resources Control Board (State Water Board) prescribe regulations that limit the amount of certain contaminants in water provided by public water systems. FDA regulations and California law also establish limits for contaminants in bottled water that provide the same protection for public health. 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. Immunocompromised people Some people may be more vulnerable to contaminants in drinking water than the general population. Immunocompromised persons such as persons with cancer undergoing chemotherapy, persons who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly and infants can be particularly at risk from infections. These people should seek advice about drinking water from their health care providers. U.S. EPA/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 at 800-426-4791.
Contaminants that may be present in source water include: • Microbial contaminants, such as viruses and bacteria, that may come from sewage treatment plants, septic systems, agricultural livestock operations and wildlife. • Inorganic contaminants, such as salts and metals, that 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 that 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 that can be naturally occurring or the result of oil and gas production and mining activities.
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Drinking water additives Fluoride IRWD’s drinking water is a blend of local groundwater and surface water, including water imported by MWD. IRWD’s local groundwater contains some naturally occurring fluoride, but we do not supplement with additional fluoride. In 2007, MWD joined a majority of the nation’s public water suppliers in adding fluoride to drinking water to help prevent tooth decay. MWD was in compliance with all provisions of the state’s fluoridation system requirements. For information on MWD’s fluoride program, visit bit.ly/MWDfluoride . For information on the fluoridation of drinking water, contact the DDW or U.S. Centers for Disease Control and Prevention. Disinfectants Drinking water regulations require some form of chlorine to be used at water treatment plants and to be maintained throughout the entire distribution system to prevent harmful bacteria from making it to the customer’s tap. IRWD uses chloramines to maintain a robust disinfectant for these purposes. Chloramines effectively inactivate harmful bacteria and are safe for consumption by humans (as well as our furry four-legged friends) at certain levels. Chloramines are monitored throughout the system, and we also watch for the presence of bacteria to be sure your drinking water is safe from end to end. People who use kidney dialysis machines may want to take special precautions and consult their physician for the appropriate type of water treatment. Customers who maintain fishponds, tanks or aquariums should also make necessary adjustments in water quality treatment, as these disinfectants are toxic to fish. For more information or questions about chloramines, visit IRWD.com or call 949-453-5300 .
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IRWD Water Quality Report 2026
Water quality and your health
Lead IRWD has no lead pipes nor galvanized service lines in its water-distribution system. That good news was confirmed in a comprehensive 2024 inventory of the District’s water lines. See the complete results at IRWD.com/nonlead . Lead can cause serious health effects in people of all ages, especially pregnant people, infants (formula- fed and breastfed) and young children. While the District’s service lines are lead-free, lead in drinking water is primarily from materials in home plumbing. IRWD is responsible for providing high-quality drinking water and removing any lead pipes in its distribution system but cannot control materials in home plumbing. Because lead levels may vary over time, lead exposure is possible even when sampling results do not detect lead at one point in time. You can help protect yourself and your family by identifying and removing lead materials within your home plumbing and taking steps to reduce your family’s risk. Using a filter certified by an American National Standards Institute accredited certifier to reduce lead is effective in reducing lead exposures. Follow the instructions provided with the filter to ensure the filter is used properly. Use only cold water for drinking, cooking and making baby formula.
Boiling water does not remove lead from water. Before using tap water for drinking, cooking or making baby formula, flush your pipes for several minutes by running your tap, taking a shower or doing laundry or dishes. If you have a lead service line or galvanized requiring replacement service line, you may need to flush your pipes for a longer period. Contact info@IRWD.com if you are concerned about lead in water and have questions. Find information on testing methods and steps to minimize exposure at epa.gov/safewater/lead . Nitrates The drinking water IRWD supplies to its customers is below the maximum allowable levels for nitrates. Nitrates in drinking water at levels above 10 mg/L is a health risk for infants less than 6 months of age. Such nitrate levels in drinking water can interfere with the capacity of infants’ blood to carry oxygen, resulting in a serious illness; symptoms include shortness of breath and blueness of skin. Nitrate levels above 10 mg/L may affect the ability of 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 are pregnant, ask advice from a health care provider.
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IRWD water quality results for 2025
Chart legend Drinking water standards established by U.S. EPA and DDW set limits for substances that may affect consumer health or aesthetic qualities of drinking water. These charts show the following water quality standards: • Maximum Contaminant Level (MCL): 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. • 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. • Secondary MCLs : Set to protect odor, taste and appearance of drinking water. • Primary Drinking Water Standard: MCLs for contaminants that affect health along with monitoring and reporting requirements and water treatment requirements. • Regulatory Action Level (AL): Concentration of contaminant, which, if exceeded, triggers treatment or requirements that a water system must follow. What is a water quality goal? U.S. EPA and DDW set voluntary water quality goals for some contaminants. Water quality goals are often set at such low levels that they are not achievable in practice and are not directly measurable. Nevertheless, these goals provide useful guide posts and direction for water management practices. The charts in this report include three types of water quality goals: • Maximum Contaminant Level Goal (MCLG): Level of a contaminant in drinking water below which there is no known or expected risk to health; set by U.S. EPA. • Maximum Residual Disinfectant Level Goal (MRDLG): Level of a drinking water disinfectant below which there is no known or expected risk to health; do not reflect the benefits of the use of disinfectants to control microbial contaminants. • Public Health Goal (PHG): Level of a contaminant in drinking water below which there is no known or expected risk to health; set by the California EPA. How are contaminants measured?
How to read this report This Water Quality Report lists results from drinking water quality assessments in 2025. Chart data includes the range of detection, the typical sources of contaminants for a variety of regulated elements and how they compare to water quality standards. To provide customers more insight, tables include secondary standards for aesthetic qualities of the water, such as hardness, pH, color, and corrosivity. The legend defines acronyms, explains water quality standards and goals, and outlines how substances are measured. Your water has been tested for many more chemicals than are listed in this report, including unregulated metals, pesticides and volatile organic compounds. If you don’t see something on the chart, don’t worry. That does not mean we didn’t test for it. Rather, if we test for a chemical and don’t find it — or if its concentration is too low to be distinguishable — we don’t list it. For example, we tested for mercury. We didn’t find it. So we didn’t list it.
• Parts per million (ppm) or milligrams per liter (mg/L) • Parts per billion (ppb) or micrograms per liter (μg/L) • Parts per trillion (ppt) or nanograms per liter (ng/L)
2025 IRWD distribution system water quality
MCL (MRDL/MRDLG)
Average amount
Range of detections
MCL violation?
Disinfection byproducts Total Trihalomethanes (ppb) Haloacetic Acids (five) (ppb) Chlorine residual (ppm)
Typical source of contaminant Byproducts of chlorine disinfection Byproducts of chlorine disinfection Disinfectant added for treatment
80 60
32.0 *** 13.0 ***
ND - 43.4 ND - 13.2 ND - 5.4
No No No No No No
(4.0 / 4)
1.8
Aesthetic quality Color (color units)
15*
<3 0.1 <1
ND - 5
Erosion of natural deposits Erosion of natural deposits Erosion of natural deposits
Turbidity (NTU)
5* 3*
ND - 14.2
Odor (threshold odor number)
ND - 4
Other Fluoride (mg/L)
2/0.8**
0.54
0.11 - 0.82
No
Erosion of natural deposits, water treatment
Twelve locations in the distribution system are tested quarterly for total trihalomethanes and haloacetic acids; 60 locations are tested monthly for color and odor, and weekly for chlorine residual and turbidity. MRDL = Maximum Residual Disinfectant Level; MRDLG = Maximum Residual Disinfectant Level Goal; ND = not detected *Contaminant is regulated by a secondary standard; **MCL/Optimum Level for our climate; *** Highest running annual average at any individual sample location Lead and copper action levels at residential taps Action Level (AL) Public Health Goal (PHG) 90th percentile value Sites exceeding AL / number of sites AL violation?
Typical source of contaminant
Copper (ppm)
1.3
0.3 0.2
0.2476
0/73 0/73
No No
Corrosion of household plumbing
Lead (ppb) Corrosion of household plumbing The most recent lead and copper at-the-tap samples were collected from 72 residences in 2025. Lead was detected in zero homes and copper was detected in 60 homes, but none of the samples for lead and copper exceeded the respective regulatory Action Level (AL). A regulatory Action Level is the concentration of a contaminant which, if exceeded in more than 10% of samples, triggers treatment or other requirements that a water system must follow. Unregulated chemicals requiring monitoring in the distribution system Chemical Notification level PHG (MCLG) Average local and imported Range of detections Most recent sampling date Lithium, Total (ppb) n/a n/a 23.6 11.7 - 42 2025 Perfluoropentanoic acid (PFPeA) (ppt) n/a n/a 1.9 ND - 3.8 2025 Perfluorobutanoic acid (PFBA) (ppt) n/a n/a 7.85 7.8 - 7.9 2025 Perfluorooctanoic Acid (PFOA) (ppt) 4.0 0.007 0.19 ND - 2.3 2024 *Contaminant is regulated by a secondary standard. 15 <5
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IRWD Water Quality Report 2026
Local and imported drinking water quality results
PHG (MCLG)
Average local treated
Average local treated
Average imported MWD
Range of detections
MCL violation? Typical source of contaminant
Chemical
MCL
Radiologicals — tested in 2025 Alpha Radiation (pCi/L)
15
0 0
1.2 0.6
ND ND
ND ND ND ND
ND -5 ND - 6
No No
Erosion of natural deposits
Beta Radiation (pCi/L) Radium-228 (pCi/L)
50
Decay of natural and man-made deposits
Not regulated
0.019
0.33 0.55
0.42 0.45
ND - 0.42
n/a
Erosion of natural deposits Erosion of natural deposits Erosion of natural deposits
Combined Radium-226 + 228 (pCi/L)
5
0
ND - 1.0
No No
Uranium (pCi/L)
20
0.43
1.8
1.9
1
ND - 3
Inorganic chemicals — tested in 2025 Aluminum (ppb)
1000
600
ND 1.8
ND 1.7
Highest RAA = 58 ppb
ND - 123 ND - 2.8 9.9 - 141 ND - 8.4
No No No No No No No No No No No No No No No No No No
Treatment process residue, natural deposits
Arsenic (ppb) Barium (ppb) Bromate (ppb) Chlorine (ppm)
10
0.004 2000
ND
Erosion of natural deposits Erosion of natural deposits
1000
23.1
129 NR 2.3
130
10
0.1 4.0
NR 2.6 0.1
Highest RAA = 2.4 ppb
Byproduct of drinking water ozonation
4.0
Highest RAA = 2.6 ppm 1.1 - 3.9
Drinking water disinfectant added for treatment Erosion of natural deposits; industrial discharge Erosion of natural deposits; IRWD does not add fluoride to its local treated groundwater and surface water
Hexavalent Chromium (ppb)
10
0.02
ND
ND NR 0.7 ND ND
ND - 0.2
Fluoride (ppm) naturally-occurring
2
1
0.32
0.33
0.05 - 0.81
Control range 0.6 - 1.2 ppm Optimal level 0.7 ppm
Fluoride (ppm) treatment-related
NR 1.9 2.0
NR ND ND
0.6 - 0.8 ND - 4.0 ND - 4.0
Water additive for dental health
Nitrate (ppm as N)
10 10
10 10
Fertilizers, septic tanks Fertilizers, septic tanks
Nitrate+Nitrite (ppm as N)
Secondary standards* — tested in 2025 Aluminum (ppb)
200* 500*
600
ND
ND
Highest RAA = 58 ppb
ND - 123 17.7 - 118
Treatment process residue, natural deposits Leaching from natural deposits; seawater influence
Chloride (ppm) Color (color units)
n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a
72.1
109
92
15*
3
<3
1
ND - 3 ND - 3
Naturally occurring organic substances Naturally occurring organic materials Ions in water; seawater influence Runoff or leaching from natural deposits Runoff or leaching from natural deposits
Odor (TON)
3*
1
1
ND
Specific Conductance (µmho/cm)
1,600*
561 103
1,049
873 182 545
363 - 1151 22.4 - 221 196 - 748
Sulfate (ppm)
500*
219 625
Total Dissolved Solids (ppm)
1,000*
343 0.10
Turbidity (NTU)
5*
Highest RAA = 0.25 NTU†
ND
ND - 7†
Erosion of natural deposits
Unregulated contaminants – tested in 2025 Alkalinity, Total (ppm as CaCO3) Not regulated
133 148 172
119 149 143
108
66 - 269 81 - 273 ND - 262 0.13 - 0.15 16.1 - 130 ND - 2.5
n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a
Runoff or leaching from natural deposits Runoff or leaching from natural deposits Runoff or leaching from natural deposits Runoff or leaching from natural deposits Runoff or leaching from natural deposits Runoff or leaching from natural deposits Byproduct of drinking water chlorination
Bicarbonate (ppm as HCO3)
Not regulated
NR
Boron (ppb)
NL = 1000
130
Bromide (ppm) Calcium (ppm) Carbonate (ppm) Chlorate (ppb)
Not regulated Not regulated Not regulated
0.14 48.5
NR
NR 56 NR
73
0.6 NR
<0.6
NL = 800
NR
32.0 12.4 0.58 236 13.8 22.0
32.0
Corrosivity (Aggressiveness)
Not regulated Not regulated Not regulated Not regulated Not regulated Not regulated
12.0 0.24 214 12.5 14.5
11.9
11.0 - 12.6
Elemental balance in water Elemental balance in water
Corrosivity (Langlier Index) @ Ambient Temp
(-0.66) - 0.61
0.07 293
Hardness, Total (ppm as CaCO3) Hardness, Total (grains/gal)
52.0 - 469 12.5 - 17.1 0.59 - 35.0
Runoff or leaching from natural deposits Runoff or leaching from natural deposits Runoff or leaching from natural deposits
17.1
Magnesium (ppm) Molybdenum (ppb)
26.9
9.6
5.2
NR
4.9 - 5.5
Drinking water treatment chemical for aesthetic quality Industrial chemical factory discharges; runoff/leaching from landfills; used in fire-retarding foams and various industrial processes Measures of the balance between pH and calcium carbonate saturation in the water
0.007 (0)
Perfluorooctanoic acid (PFOA) (ppt)
NL = 4.0
1.2
ND
ND
ND - 2.3
No
Calcium Carbonate Precipitation Potential (CCPP) (as CaCO3) (ppm)
Not regulated
n/a
NR
NR
7.4
2.4 - 11
n/a
pH (pH units)
Not regulated Not regulated Not regulated
n/a n/a n/a n/a n/a n/a
8.0
7.6 5.4 101 NR 2.9 ND
8.3 4.3 88
7.0 - 8.6 0.61 - 6.0 24.7 - 106 333 - 657
n/a n/a n/a
Acidity, hydrogen Ions
Potassium (ppm)
1.5
Runoff or leaching from natural deposits Runoff or leaching from natural deposits Runoff or leaching from natural deposits Various natural and man-made sources
Sodium (ppm)
61.2
Total Dissolved Solids, Calculated (TDS)
1000*
NR
507 2.4
No TT
Total Organic Carbon (ppm)
TT
0.20
ND - 2.9 ND - 11.1
Vanadium (ppb) Runoff or leaching from natural deposits Your water has been tested for many more chemicals than are listed above, including metals (such as mercury), pesticides and volatile organic compounds. Chemicals not detected in any water sources are not included in the table. ppb = parts-per-billion; ppm = parts-per-million; ppt = parts-per-trillion; pCi/L = picoCuries per liter; ntu = nephelometric turbidity units; ND = not detected; N/A = not applicable; NR = not required to be tested; < = average is less than the detection limit for reporting purposes; MCL = Maximum Contaminant Level; (MCLG) = federal MCL Goal; PHG = California Public Health Goal; µmho/cm = micromho per centimeter; NL = Notification Level; TT = Treatment Technique; RAA = Highest Running Annual Average; *Contaminant is regulated by a secondary standard to maintain aesthetic qualities (taste, odor, color). Turbidity — Combined Filter Effluent Treatment Technique TT violation? Typical source Baker Water Treatment Plant 1) Highest single turbidity measurement 0.03 NTU No Soil run-off 2) Percentage of samples less than or equal to 0.3 NTU 100% No Soil run-off Metropolitan Water District Diemer Filtration Plant 1) Highest single turbidity measurement 0.05 NTU No Soil run-off 2) Percentage of samples less than or equal to 0.3 NTU 100% No Soil run-off NL = 50 4.9 ND n/a Turbidity is the measurement of the cloudiness of water, an indication of particulate matter, some of which might include harmful microorganisms. Low turbidity in treated surface water is a good indicator of effective filtration. Filtration is called a treatment technique (TT) . TT is a required process intended to reduce the level of contaminants in drinking water that are difficult and sometimes impossible to measure directly. Data is taken from a continuous online meter. +On Jan. 21, 2025, a higher than normal (7 NTU) grab sample was reported. This value is inconsistent with the continuous online analyzer, which showed a reading of 0.0259 NTU at the same time that the grab sample was taken. The available evidence suggests that the higher than normal grab sample was not a valid representation of the water quality produced by the plant at the time. No other result above 0.1 NTU was reported throughout the year.
IRWD Water Quality Report 2026 | Page 11
Water sources are assessed regularly to examine potential pollutant sources in the area. This does not mean contaminants are actively being discharged into these water sources. Rather, these surveys are used to evaluate the vulnerability of water sources to contamination and determine what protective measures are needed. Source water assessments
Date of assessment
Location/assessment
Vulnerabilities assessed
IRWD Baker Water Treatment Plant water assessment Santiago Reservoir (Irvine Lake) Sanitary Survey
Septic systems and wildfires
2025
See MWD Imported Water Assessment below for water received from MWD IRWD groundwater assessment Lake Forest service area of IRWD
Dry cleaners and sewer collection systems
December 2022
Gas stations, historic gas stations, metal plating/ finishing/fabrication facilities, military installations, and plastics/synthetics producers Sewer collection systems, automobiles (gas stations), historic gas stations, and underground storage tanks (confirmed leaking tanks)
Dyer Road Well Field
July 2023
Wells 21–22 Desalter
May 2009
Irvine Desalter Project
Crop irrigation and fertilizers Sewer collection systems Historical mining operations
March 2006 March 2003 January 2003
Orange Park Acres service area of IRWD Santiago Canyon service area of IRWD MWD Imported Water Assessment Colorado River Watershed Sanitary Survey Northern California’s State Water Project Watershed Sanitary Survey
Recreation, urban/stormwater runoff, increasing urbanization in the watershed, and wastewater Urban/stormwater runoff, wildlife, agriculture, recreation, and wastewater
2020
2021
You can request copies of the IRWD reports listed above by writing to IRWD, Attn: District Secretary, 15600 Sand Canyon Ave., Irvine, CA 92618. To request copies of MWD reports, call MWD at 800-225-5693 .
At-home water testing At-home test kits provide generic, approximate detections of substances in water but do not offer the analytical testing levels necessary to determine the quality of the water sample. These test kits are not based on standardized methods and do not have any way to verify accuracy. Customers who have their home’s water tested should contact a certified laboratory to ensure accurate results. Find a list at IRWD.com/laboratories . IRWD does not endorse specific laboratories for home testing. The data presented in this report is analyzed and reported by California Environmental Laboratory Accreditation Program certified laboratories that follow extensive quality assurance and quality control
programs and are managed by qualified, trained scientists. Water providers take on the responsibility of verifying water quality data, and that process is heavily regulated by state and federal agencies. Call IRWD at 949-453-5300 for any questions.
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IRWD Water Quality Report 2026
Stay in the know
NOTE OF IMPORTANCE This report contains important information about your drinking water. Contact Irvine Ranch Water District at 15600 Sand Canyon Ave., Irvine, CA 92618, or 949-453-5500 for assistance in other languages. Chinese (Simplified) 这份报告含有关于您的饮用水的重要讯息。请用以下地址和电 话联系 Irvine Ranch Water District 以获得中文的帮助: 15600 Sand Canyon Ave., Irvine, CA 92618, 949-453-5500. Chinese (Traditional) 這份報告含有關於您的飲用水的重要訊息。請用以下地址和電 話聯繫 Irvine Ranch Water District 以獲得中文的幫助: 15600 Sand Canyon Ave., Irvine, CA 92618, 949-453-5500. Korean 이 보고서는 당신의 식수에 관한 중요한 정보를 포함하고 있습니다. 한국어로 된 도움을 원하시면 Irvine Ranch Water District, 15600 Sand Canyon Ave., Irvine, CA 92618, 949-453-5500 로 문의 하시기 바랍니다. Spanish Este informe contiene información muy importante sobre su agua para beber. Favor de comunicarse Irvine Ranch Water District a 15600 Sand Canyon Ave., Irvine, CA 92618, o 949-453-5500 para asistirlo en español. Arabic برشلا هايم لوح ةمهم تامولعم ىلع ريرقتلا اذه يوتحي عم لصاوتلا ىجرُي ،تامولعملا نم ديزمل .كيدل Irvine Ranch Water District مقرلا ىلع 15600 Sand Canyon Ave., Irvine, CA 92618. وه فتاهلا مقر 949-453-5500. Farsi .تسامش یندیماشآ بآ دروم رد یمهم تاعالطا یواح شرازگ نیا رب افتل یندیماشآ بآ نامزاس هب تاعالطا بسک یا Irvine Ranch Water District سردآ رد هک 15600 Sand Canyon Ave., Irvine, CA 92618 نفلت هرامش .دیریگب سامت 949-453-5500 .تسا Hindi इस रि पोर्ट में आपके पीने के जल से सम्बंधि त महत्वपूर्ण जानकारी है l हिं दी में सहायता के लि ए, Irvine Ranch Water District को 15600 Sand Canyon Ave., Irvine, CA 92618 अथवा 949-453-5500 पर संपर्क करें. Japanese この報告書には上水道に関する重要な情報が記されております。ご 質問等ございましたら、 Irvine Ranch Water District, 15600 Sand Canyon Ave., Irvine, CA 92816 949-453-5500 まで日本語でご連絡下さい。
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IRWD website Visit IRWD.com for the latest news and information.
Board meetings The IRWD Board of Directors meets the second and fourth Monday of each month at 5 p.m. at IRWD headquarters, 15600 Sand Canyon Ave., Irvine, CA 92618. Members of the public are welcome to attend.
IRWD Water Quality Report 2026 | Page 13
About Irvine Ranch Water District
IRWD provides high-quality drinking water, reliable sewage collection and treatment, drought-proof recycled water, and natural urban runoff treatment for central Orange County. IRWD serves all of Irvine , most of Lake Forest , and parts of Newport Beach , Tustin , Costa Mesa , Orange and unincorporated Orange County .
Orange
Unincorporated Orange County
Tustin
Costa Mesa
Irvine Ranch Water District
Lake Forest
Irvine
Newport Beach
Newport Coast
181 square miles (nearly 20% of Orange County)
450,000 residential population served
640,000 daytime population served
IRWD water treatment facilities IRWD is Orange County's largest retail water district. Below are just a few of our major facilities used in the delivery and treatment of drinking water. Learn more about all IRWD facilities at IRWD.com/facilities .
Baker Water Treatment Plant The Baker Water Treatment Plant in Lake Forest provides 28.1 million gallons of reliable, high-quality drinking water per day — enough to serve more than 60,000 homes.
Deep Aquifer Treatment System The Deep Aquifer Treatment System purifies drinking water from the Orange County Groundwater Basin and produces 8 million gallons of drinking water each day.
Irvine Desalter Plant The Irvine Desalter Project consists of five wells in Irvine. Water from the wells is sent to the IDP treatment facility, which provides 1.6 billion gallons of drinking water per year.
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IRWD Water Quality Report 2026
IRWD.com/waterquality
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