Attachment 2 2023 2025 Annual Water Quality Reports — Thousand Oaks City Council, September 23, 2025

For additional information about your drinking
water, contact the Water Quality Supervisor in the
Public Works Department at 805-449-2499.

The City of Thousand Oaks (City) Public Works Department distributes up to 15 million gallons of water each day
to roughly 17,000 residences and businesses. Our
mission is to provide high quality water that meets the stringent water quality standards established by the
U.S. Environmental Protection Agency (USEPA) and the
State Water Resources Control Board (SWRCB). The Public Works Department is dedicated to providing you with a
dependable supply of safe and high-quality water.

Annual Water
Quality Report
(Reporting 2022 Data) PWSID # 5610020
2023

OUR MISSION
Este informe contiene información muy
importante sobre su agua para beber. Tradúzcalo
ó hable con alguien que lo entienda bien. Para
mas informacion, puede llamar al 805-449-2499.

ATTACHMENT #2
DPW:1025-40\ev\Counc il\2025\09232025\Triennial PHG Water Quality Att 2.pdf OUR WATER SOUR CES IN 2022
68% of the City’s water supply was from the State Water Project. This surface water is imported from Northern
California, which originates at Lake Oroville. The water then flows through the Sacramento River Delta system
and is transported via the California Aqueduct to Southern California. The water is treated, filtered and disinfected at the Metropolitan Water District’s (MWD) Jensen Filtration Plant in Granada Hills. 24% of the City’s water supply was from a blend of the Colorado River Aqueduct and the State Water Project. This water is treated, filtered and disinfected at MWD’s Weymouth Filtration Plant in La Verne. These
water supplies are then piped directly to the City through the transmission facilities of the Calleguas Municipal Water District (Calleguas) located in Thousand Oaks. 6% of the City’s water supply came from Calleguas’ Los Posas Wellfields and the last 2% of the City’s water supply came from the Calleguas Lake Bard Reservoir and Water Filtration Facility.

Should these water sources be interrupted by general
maintenance, earthquake or other calamity, Calleguas can deliver water to the City solely from their Las Posas Wellfields and their Lake Bard Reservoir and Water Filtration facilities.

PUBLIC PARTICIPATION
The City drinking water system is managed as an
enterprise fund by the elected City Council. Operations are conducted by the Public Works Department. The
City Council meets on Tuesday evenings at 6 PM in the
Scherr Forum Theater in the Civic Arts Plaza located at 2100 Thousand Oaks Blvd. For information about Council
meeting schedules, please call 805-449-2151 or visit
www.toaks.org.

PUBLIC EDUCATION
The City is pleased to present to you this year’s Annual Water Quality Report, which shows that the City’s water supply met or exceeded all State and Federal standards in 2022.

We are committed to providing you this information in the sincere belief that informed customers are our best partners.

Included in this report are details about where your water comes from, what it contains and how it compares to State standards. The City works very hard with our neighbors, our partners and suppliers to continually improve the quality of the water supply, the protection of our water sources, the dependability of supply and the integrity of our
storage and distribution system.

Miles
0 2 1
City Limits
Water Mains
Water Service Area
23 101
City of Thousand Oaks
Water System

PUBLIC HEALTH
Some people may be more vulnerable to contaminants in drinking water than the general population. Immuno-compromised persons such as those with cancer who are 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 their drinking water from their health care providers. The USEPA and the Centers for Disease Control guidelines on appropriate means to lessen the risk from infection by Cryptosporidium and other microbial contaminants are available from the USEPA Safe Drinking Water Hotline (800-426-4791).

Fluoride - MWD initiated a Fluoride Optimization Program in November of 2007. Naturally occurring fluoride level ranges from

0.1 to 0.4 mg/L (parts per million). MWD has adjusted the level to the optimal range for dental health of 0.7 mg/L. If you or your children are taking Fluoride supplements, please consult with your dentist or dental healthcare provider for further direction.

Purity and Contaminants - 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 the water poses a health risk. More information about contaminants and potential health risks may also be obtained by calling the Safe Drinking Water Hotline
(1-800-426-4791).

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.

During the year, thousands of tests were conducted on our drinking water for over 150 drinking water constituents and contaminants to ensure the safety of your drinking water. Prior to filtration and treatment, contaminants that may be present in source water include:

Inorganic contaminants, such as salts and metals that can be naturally occurring or result from urban stormwater run-off, industrial or domestic wastewater discharges, oil and gas production, mining, or farming.

Organic chemical contaminants, including synthetic and volatile organic chemicals, which are by-products of industrial processes and petroleum production, and can also come from gas stations, urban stormwater run-off, agricultural application and septic systems.

Microbial contaminants, such as viruses and bacteria that may come from sewage treatment plants, septic systems, agricultural livestock operations and wildlife.operations and wildlife.

Radiological contaminants can be naturally occurring or the result of oil and gas production and mining activities.

Pesticides and Herbicides that may come from a variety of sources such as agriculture, urban stormwater run-off and residential uses.

Lead was not detected in the City’s water supply. 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 private internal plumbing. The City does not use or install lead service lines and cannot control the variety of materials used in private plumbing components. If you are concerned about lead leaching out of your plumbing materials after your water has not been used for several hours, you can minimize the potential for lead exposure by flushing your tap for at least 30 seconds before using the water for drinking or cooking.

Also, if you still have concerns about lead in your water due to internal plumbing materials you can hire a private laboratory to test your water for lead. Information on lead in drinking water, testing methods and steps you can take to minimize exposure is available from the Safe Drinking Water Hotline (1-800-426-4791) or at
http://www.epa.gov/safewater/lead.

MWD has conducted a source water assessment of its State Water Project supplies. State Water Project supplies are most vulnerable to urban/ storm water runoff, wildlife, agriculture, recreation and wastewater. A copy of the assessment can be obtained by contacting MWD by phone at (213-217-6000).

In order to ensure that tap water is safe to drink, the SWRCB prescribes regulations that limit the number of certain contaminants in water provided by public water systems. The quality of our drinking water meets all State requirements for safe water.

The following table lists the drinking water contaminants that were detected in the City’s drinking water during 2022. The presence of any of these contaminants in the water does not necessarily constitute a health risk. As you can determine from the results, the quality of the water delivered by the City consistently meets all State standards. The data presented in this table is from testing performed between January 1 and December 31, 2022, unless otherwise noted. State of California Standards are either equal to, or more stringent than Federal USEPA water quality standards. Therefore, Federal MCLs are not listed. Applicable Abbreviations, Definitions and Notes are identified at the conclusion of the Table.

Pesticides/PCBs
28 chemicals were analyzed

ORGANIC CHEMICALS
None Were Detected
Semi-Volatile Organic
Compounds
6 Chemicals Were Analyzed
None Were Detected
Volatile Organic
Compounds
27 chemicals were analyzed (including
MTBE, PCE and TCE)
None Were Detected

WATER QUALITY DATA
Parameter Units
State

MCL-MRDL
PHG
(MCLG)-MRDLG
Range
Average
MWD Jensen
Plant
68% of Supply
MWD
Weymouth
Plant 24% of
Supply
Calleguas
Las Posas
Wellfield 6%
of Supply
Calleguas
LBWFP
2% of Supply
Potential Major Sources if De-
tected in Drinking Water
PRIMARY DRINKING WATER STANDARDS (PDWS) - Mandatory Health-Related Standards CLARITY [a]
Combined Filter
Effluent Turbidity NTU 0.3 Highest
Value 0.05 0.04 N/A 0.10 Soil runoff
TT= % of samples ≤0.3 NTU [a] 100% 100% N/A 100%
MICROBIOLOGICAL [b]
Total Coliform Bacteria
(State Total
Coliform Rule)
% of
Samples 5 % 0
Highest
Monthly
%

1.5% City of Thousand Oaks Results Naturally present in the environment
Effective July 1, 2021 Standards for Cryptosporidium, Giardia lamblia, Legionella, viruses and Heterotrophic Plate Count Bacteria are Treatment Techniques (TT) with which MWD and Calleguas comply. There were no detections of fecal coliform or E. Coli bacteria in the City’s distribution system in 2022.

Parameter Units
State

INORGANIC CHEMICALS
Aluminum [c] ppb 1000 600 Range ND - 81 58 - 240 ND ND Erosion of natural deposits; residue from water treatment processAverage 62 156 ND ND
Arsenic ppb 10 0.004 Range 2.4 ND 2.0 - 5.0 3.0 Erosion of natural deposits; runoff from orchards; electronics production wastesAverage 2.4 ND 3.0 3.0 Barium ppm 1 2 Range ND 0.107 ND ND Erosion of natural deposits; discharge from oil & metal refineriesAverage ND 0.107 ND ND
Copper [d] ppm AL=1.3 0.3 Range ND - 0.20 N/A N/A N/A Internal corrosion of household pipes; erosion of natural deposits90th % 0.15 N/A N/A N/A
Fluoride [e] ppm 2.0 1 Range 0.7 - 0.9 N/A N/A N/A
Water additive that promotes strong teeth
Highest RAA 0.7 N/A N/A N/A
Lead [d] ppb AL=15 0.2 Range ND - 5.4 N/A N/A N/A Internal corrosion of household pipes; erosion of natural deposits90th % 2.2 N/A N/A N/A
Nitrate (as N) ppm 10 10 Range 0.9 ND 0.1 - 0.6 ND Runoff & leaching from fertilizer use; erosion of natural depositsAverage 0.9 ND 0.4 ND
Selenium ppb 50 30 Range ND ND 6 - 13 11 Erosion of natural deposits; discharge from oil & metal refineriesAverage ND ND 8 11
14 other metals and chemicals were analyzed (including Asbestos, Chromium, Perchlorate, Mercury and Cyanide) none were detected. Copper and Lead were not detected in the water supply.

Treatment related
State
MCL-
MRDL
PHG
(MCLG)-
MRDLG
Range
Average
MWD
Jensen Plant
68% of Supply
MWD Weymouth
Plant 24% of
Supply
Calleguas Las
Posas Wellfield
6% of Supply
Calleguas
LBWFP 2%
of Supply
Potential Major Sources if Detected
in Drinking WaterParameter Units
RADIONUCLIDES [f] [analyzed every three years, for four consecutive quarters] Gross Alpha Particle Activity pCi/L 15 (0) Range ND ND ND - 3.1 ND Erosion of natural depositsAverage ND ND ND ND Gross Beta Particle Activity pCi/L 50 (0) Range ND - 5.0 4.0 - 7.0 ND 4.2 Decay of natural & man-made depositsAverage ND 6.0 ND 4.2
Uranium pCi/L 20 0.43 Range ND - 3.0 1.0 - 3.0 1.8 - 2.8 1.4 Erosion of natural depositsAverage ND 2.0 2.2 1.4 3 other radionuclides were analyzed - none were detected

DISINFECTANT RESIDUALS / DISINFECTION BY-PRODUCTS
Bromate [g] ppb 10 0.1 Range ND - 15.0 ND - 7.6 N/A ND By-product of drinking water ozonationHighest RAA 7.2 ND N/A ND
Control of DBP Precursors as
Total Organic Carbon (TOC)
ppm TT Range 1.0 - 1.4 1.7 - 2.6 0.9 - 1.0 1.1
Various natural and man-made sources;
TOC as a medium for formation of DBPs
Highest RAA 1.5 2.4 1.0 1.1

MRDL MRDLG
System-
wide
City of Thousand
Oaks Results
Total Chlorine Residual [h] ppm 4 4 Range 0.90 - 1.95 N/A N/A N/A Drinking water disinfectant added for treatment
Highest RAA 1.49 N/A N/A N/A
Haloacetic Acids [i] (HAA5) ppb 60 N/A Range 1.4 - 4.5 N/A N/A N/A By-product of drinking water disinfection
Highest LRAA 3.3 N/A N/A N/A
Total Trihalomethanes [i] ppb 80 N/A Range 11 - 22 N/A N/A N/A By-product of drinking water disinfection
(TTHM) Highest LRAA 20 N/A N/A N/A
SECONDARY DRINKING WATER STANDARDS (SDWS) - Aesthetic Standards Aluminum [c] ppb 200 600 Range ND - 81 58 - 240 ND ND Erosion of natural deposits; residue from water treatment processes
Average 62 156 ND ND
Chloride ppm 500 N/A Range 67 - 73 98 - 105 63 - 90 105 Runoff/leaching from natural deposits; seawater influence
Average 70 102 75 105
Color Units 15 N/A Range 1 1 ND ND Naturally occurring organic materialsAverage 1 1 ND ND Iron ppb 300 Range ND ND ND - 140 ND Runoff/leaching from natural deposits; industrial wastes
Average ND ND ND ND
Manganese [j] ppb 50 NL = 500 Range ND ND ND - 110 ND Leaching from natural depositsAverage ND ND ND ND Specific Conductance µS/cm 1600 N/A Range 557 - 572 964 - 1020 584 - 716 733 Substances that form ions when in water; seawater influence
Average 564 992 664 733
Sulfate ppm 500 N/A Range 71 - 80 212 - 232 90 - 133 89 Runoff/leaching from natural depositsAverage 76 222 105 89 Total Dissolved Solids ppm 1000 N/A Range 332 - 335 632 - 643 350 - 440 390 Runoff/leaching from natural depositsAverage 334 638 407 390 7 other metals and constituents were analyzed - none were detected ADDITIONAL PARAMETERS (Unregulated)
Alkalinity ppm NS NS Range 84 126 - 128 100 120
Average 84 127 100 120
Boron ppm NL=1 NS Range 0.22 0.14 0.20 - 0.46 0.30
Average 0.22 0.14 0.30 0.30
Calcium ppm NS NS Range 32 - 34 68 - 71 36 - 53 39
Average 33 70 42.7 39
Chlorate ppb NL = 800 NS Range 243 88 ND - 30 ND
Average 243 88 ND ND
Corrosivity [k] AI NS NS Range 12.1 12.5 11.4 - 12.2 12.2 Average 12.1 12.5 11.9 12.2
Hardness (Total Hardness) ppm NS NS Range 107 - 110 277 - 281 127 - 190 167 108 ppm = 6.25 grains per gallon (gpg) Average 108 279 160 167 279 ppm = 16.3 gpg
Magnesium ppm NS NS Range 6.2 -7.5 25 - 26 9.0 - 16 17
Average 6.8 26 13 17
N-Nitrosodimethylamine ppt NL = 10 3 Range ND ND 2.5 - 2.7 ND (NDMA) Average ND ND 2.6 ND
pH pH
units NS NS Range 8.2 - 8.3 8.1 7.4 - 8.2 8.1
Average 8.3 8.1 7.8 8.1
Potassium ppm NS NS Range 2.0 4.5 - 4.8 3.0 - 4.0 4.0
Average 2.0 4.6 3.7 4.0
Sodium ppm NS NS Range 71 - 72 98 - 103 58 - 78 89
Average 72 100 70 89
Total Organic Carbon ppm TT Range 1.0 - 1.4 1.7 - 2.6 0.9 - 1.0 1.1 Average 1.5 2.4 1.0 1.1
Vanadium ppb NL = 50 NS Range 6.2 ND 3.0 - 4.0 ND
Average 6.2 ND 3.5 ND
5 other constituents and metals were analyzed including Radon - none were detected Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) List (Unregulated) [l] Perfluoropentanoic acid ppt NS NS Range ND 2.0 N/A N/A
(PFPeA) Average ND 2.0 N/A N/A
28 other PFAS constituents were analyzed - none were detected AI = Aggressiveness Index.

AL = Federal Regulatory Action Level = The level of contaminant which when exceeded, triggers treatment or other requirements that a water system must follow.

DBP = Disinfection By-Product
LBWFP = Lake Bard Water Filtration Plant.

LRAA = Locational Running Annual Average
MCL = Maximum Contaminant Level = The highest level of
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 are set to protect the odor, taste, and appearance of drinking water.

MCLG = Maximum Contaminant Level Goal = The level of contaminant in drinking water below which there is no known or expected risk to health. MCLGs are set by the US Environmental Protection Agency (EPA).

MRDL = Maximum Residual Disinfectant Level = The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of disinfectant is necessary for control of microbial contaminants.

MRDLG = Maximum Residual Disinfectant Level Goal = The level of 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.

MWD = Metropolitan Water District.

N/A = Not Applicable
ND = None Detected. Detection Limits for the purposes of reporting (DLRs) available on request.

NL = Notification Level
NS = No Standard
NTU = Nephelometric Turbidity Units.
pCi/L = Picocuries per liter (units to measure radiation).

PHG = Public Health Goal = The level of contaminant in drinking water below which there is no known or expected risk to health. PHGs are set by the California Environmental Protection Agency (Cal-EPA).

Primary Drinking Water Standard (PDWS) = MCLs, MRDLs and treatment techniques (TTs) for contaminants that affect health, along with their monitoring and reporting requirements.
ppb = parts per billion, or micrograms per Liter (µg/L), equivalent to 1 drop of water in a standard swimming pool (13,208 gallons). ppm = parts per million, or milligrams per liter (mg/L), equivalent to 1 drop of water in a aquarium (13.2 gallons).
ppt = parts per trillion, or nanograms per Liter (ng/L), equivalent to 1 drop of water in 20 olympic swimming pools (13,208,000 gallons).

RAA = Running Annual Average
Secondary Drinking Water Standards (SDWS) = MCLs for
contaminants that affect taste, odor, or appearance of the drinking water. Contaminants with SDWSs do not affect health at the MCL levels.

WATER QUALITY DATA
Abbreviations, Definitions and Notes
www.toaks.org/waterqualityreport
[a] T he turbidity level of the filtered water shall be less than or equal to 0.3 NTU in 95% of the measurements taken each month and shall not exceed 1.0 NTU at any time. Turbidity is a measure of the cloudiness of the water. We monitor it because it is a good indicator of the effectiveness of the filtration system. [b]
T
he City’s water was in compliance with both the State Total Coliform Rule and the Federal Revised Total Coliform Rule. Over 1,000 samples were analyzed in 2022 for Total Coliform and E. Coli. [c]
A
luminum has both primary and secondary standards. Compliance with the MCL is based on a running annual average. The secondary standard MCL was not exceeded.
[d]
L
ead and Copper are sampled at the customer’s tap every (3) years.

Last event was conducted in 2022 and scheduled to occur again in 2025. 35 samples were collected and the 90th percentile was reported above. No samples exceeded the AL for Lead and Copper. [e]
MWD initia
ted a Fluoride Optimization Program in 2007. See text
for further detail.
[f ]
T
he MWD’s results are from 2020, part of a 4-quarter radiological monitoring program. Calleguas conducts radiological monitoring annually. Water utilities are required to make these surveys every three years.
[g]
C
ompliance for treatment plants that use ozone is based on a running annual average of monthly samples, which was in compliance in 2022.
[h]
T
otal chlorine residual measures the concentration of chloromines (5 parts chlorine and 1 part ammonia) that are added as a disinfectant system-wide.
[i]
C
ompliance was based on the LRAA of data collected at
distribution system-wide monitoring locations. The range of all samples collected is included.
[j]
C
ompliance for manganese is based on a running annual average.

Due to emergency drought conditions, Calleguas operated the Las Posas Wellfield as an extraordinary water supply measure to conserve MWD’s limited State Project Water supplies in 2022. The MCL was not violated.
[k]
AI measur
es the aggressiveness of water transported through
pipes. AI <10 is highly corrossive to water system materials. AI at 12 or above indicates non-aggressive water.
[l]
C
onsumer confidence report (CCR) detection limits are based on method detection limit for the EPA 533 Method. Results below CCR detection limits are considered ND. PFAS results below CCR detection limits but above reporting limits are included in this report.

TON = Threshold Odor Number
TT = Standards are Treatment Techniques for contaminants with which MWD and Calleguas are in compliance.
µS/cm = micro Siemen per Centimeter (to measure conductivity) © 2023 Goldstreet Design Agency, Inc. All Rights Reserved For additional information about your drinking water,
contact the Water Quality Supervisor in the Public
Works Department at 805-449-2499.

The City of Thousand Oaks (City) Public Works
Department distributes up to 15 million gallons of water each day to roughly 17,000 residences and businesses.

Our mission is to provide high-quality water that meets the stringent water quality standards established by the U.S. Environmental Protection Agency (USEPA) and the
State Water Resources Control Board (SWRCB). The Public Works Department is dedicated to providing you with a
dependable supply of safe and high-quality water.

Annual Water
Quality Report
(Reporting 2023 Data) PWSID # 5610020
2024

OUR MISSION
Este reporte contiene las instrucciones más recientes
para obtener información importante sobre su
agua potable. Traduzcalo o hable con alguien que
lo entienda bien, si necesita hablar con alguien en
español favor de comunicarse al 805-449-2499.

PUBLIC EDUCATION
The City is pleased to present to you this year’s Annual Water Quality Report, which shows that the City’s water supply met or exceeded all State and Federal standards in 2023. We are committed to providing you with this information in the sincere belief that informed customers are our best partners. Included in this report are details about where your water comes from, what it contains, and how it compares to State standards. The City works very hard with our neighbors, our partners, and suppliers to continually improve the quality of the water supply, the protection of our water sources, the dependability of supply, and the integrity of our storage and distribution system.

PUBLIC PARTICIPATION
The City drinking water system is managed as an enterprise fund by the elected City Council. Operations are conducted by the Public Works Department. The City Council meets on Tuesday evenings at 6 PM in the Scherr Forum Theater in the Civic Arts Plaza located at 2100 Thousand Oaks Blvd. For information about Council meeting schedules, please call 805-449-2151 or visit www.toaks.org.

OUR W ATER SOURCES IN 2023
99% of the City’s water supply was from the State
Water Project. This surface water is imported
from Northern California, which originates at
Lake Oroville. The water then flows through the
Sacramento River Delta system and is transported
via the California Aqueduct to Southern California.

The water is treated, filtered and disinfected at
the Metropolitan Water District’s (MWD) Jensen
Filtration Plant in Granada Hills. This water supply
is then piped directly to the City through the
transmission facilities of the Calleguas Municipal
Water District (Calleguas) located in Thousand
Oaks. The last 1% of the City’s water supply came
from the Calleguas Lake Bard Reservoir and Water
Filtration Facility.

Should these water sources be interrupted by
general maintenance, earthquake, or other
calamity, Calleguas can deliver water to the City
solely from their Las Posas Wellfields and their
Lake Bard Reservoir and Water Filtration facilities.

PUBLIC HEALTH
Some people may be more vulnerable to contaminants in drinking water than the general population. Immuno-compromised persons such as those with cancer who are 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 their drinking water from their healthcare providers. The USEPA and the Centers for Disease Control guidelines on appropriate means to lessen the risk of infection by Cryptosporidium and other microbial contaminants are available from the USEPA Safe Drinking Water Hotline (800-426-4791).

Fluoride - MWD initiated a Fluoride Optimization Program in November of 2007. Naturally occurring fluoride level ranges from

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 human activity.

During the year, thousands of tests were conducted on our drinking water for over 150 drinking water constituents and contaminants to ensure the safety of your drinking water. Before filtration and treatment, contaminants that may be present in source water include:

Inorganic contaminants, such as salts and metals can be naturally occurring or result from urban stormwater run-off, industrial or domestic wastewater discharges, oil and gas production, mining, or farming.

Organic chemical contaminants, including synthetic and volatile organic chemicals, are by-products of industrial processes and petroleum production, and can also come from gas stations, urban stormwater run- off, agricultural applications, and septic systems.

Microbial contaminants, such as viruses and bacteria may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife.

Radiological contaminants can be naturally occurring or the result of oil and gas production and mining activities.

Pesticides and Herbicides may come from a variety of sources such as agriculture, urban stormwater run-off, and residential uses.

Also, if you still have concerns about lead in your water due to internal plumbing materials you can hire a private laboratory to test your water for lead. Information on lead in drinking water, testing methods, and steps you can take to minimize exposure is available from the Safe Drinking Water Hotline (1-800-426-4791) or at
http://www.epa.gov/safewater/lead.

MWD has conducted a source water assessment of its State Water Project supplies. State Water Project supplies are most vulnerable to urban/ stormwater runoff, wildlife, agriculture, recreation, and wastewater. A copy of the assessment can be obtained by contacting MWD by phone at (213-217-6000).

To ensure that tap water is safe to drink, the SWRCB prescribes regulations that limit the number of certain contaminants in water provided by public water systems. The quality of our drinking water meets all State requirements for safe water.

Miles
0 21
City Limits
Water Mains
Water Service Area
23 101
City of Thousand Oaks
Water System
The following table lists the drinking water contaminants that were detected in the City’s drinking water during 2023. The presence of any of these contaminants in the water does not necessarily constitute a health risk. As you can determine from the results, the quality of the water delivered by the City consistently meets all State standards. The data presented in this table is from testing performed between January 1 and December 31, 2023, unless otherwise noted. State of California Standards are either equal to or more stringent than Federal USEPA water quality standards. Therefore, Federal MCLs are not listed. Applicable Abbreviations, Definitions, and Notes are identified after the Table.

W ATER QUALITY DATA
Parameter Units
State

MCL-MRDL
PHG
(MCLG)-MRDLG
Range
Average
MWD Jensen Plant
99% of Supply
Calleguas LBWFP
1% of Supply
Potential Major Sources if
Detected in Drinking Water
PRIMARY DRINKING WATER STANDARDS (PDWS) - Mandatory Health-Related Standards CLARITY [a]
Combined Filter
Effluent Turbidity NTU 0.3 Highest
Value 0.07 0.04 Soil runoff
TT= % of samples ≤0.3 NTU [a] 100% 100%
MICROBIOLOGICAL [b]
Total Coliform Bacteria % of
Samples 5 % 0 Highest
Monthly % 0 N/A Naturally present in the
environment
(State Revised Total
Coliform Rule, Effective
July 1, 2021)
Standards for Cryptosporidium, Giardia lamblia, Legionella, viruses and Heterotrophic Plate Count Bacteria are Treatment Techniques (TT) with which MWD and Calleguas comply. There were no detections of fecal coliform or E. Coli bacteria in the City’s distribution system in 2023.

Parameter Units
State

MCL-MRDL
PHG
(MCLG)-MRDLG
Range
Average
MWD Jensen Plant
99% of Supply
Calleguas LBWFP
1% of Supply
Potential Major Sources if
Detected in Drinking Water

INORGANIC CHEMICALS
Aluminum [c] ppb 1000 600 Range ND - 83 ND Erosion of natural deposits; residue from water treatment processHighest RAA ND ND
Arsenic ppb 10 0.004 Range ND 3.0 Erosion of natural deposits; runoff from orchards; electronics production
wastesAverage ND 3.0
Copper [d] ppm AL=1.3 0.3 Range ND - 0.20 N/A Internal corrosion of household pipes; erosion of natural deposits90th % 0.15 N/A
Fluoride [e] ppm 2.0 1 Range 0.6 - 1.0 N/A Water additive that promotes strong teethTreatment-related Highest RAA 0.7 N/A
Lead [d] ppb AL=15 0.2 Range ND - 5.4 N/A Internal corrosion of household pipes; erosion of natural deposits90th % 2.2 N/A
Nitrate (as N) ppm 10 10 Range 1.0 ND Runoff & leaching from fertilizer use; erosion of natural depositsAverage 1.0 ND
Selenium ppb 50 30 Range ND 8 Erosion of natural deposits; discharge from oil & metal refineriesAverage ND 8
15 other metals and chemicals were analyzed (including Asbestos, Chromium, Cyanide, Mercury and Perchlorate) none were detected. Copper and Lead were not detected in the water supply.

Pesticides/PCBs
28 chemicals were analyzed

ORGANIC CHEMICALS
None Were Detected
Volatile Organic
Compounds
27 chemicals were analyzed
(including MTBE, PCE and TCE)
Semi-Volatile
Organic Compounds
6 Chemicals Were Analyzed
None Were Detected None Were Detected
State

MCL-MRDL
PHG
(MCLG)-MRDLG
Range
Average
MWD Jensen
Plant 99% of
Supply
Calleguas
LBWFP 1% of
Supply
Potential Major Sources if
Detected in Drinking WaterParameter Units
RADIONUCLIDES [f] [analyzed every three years, for four consecutive quarters] Gross Alpha Particle Activity pCi/L 15 (0) Range ND 3.2 Erosion of natural depositsAverage ND 3.2 Gross Beta Particle Activity pCi/L 50 (0) Range ND 4.4 Decay of natural & man-made depositsAverage ND 4.4
Uranium pCi/L 20 0.43 Range 2.0 - 3.0 1.5 Erosion of natural depositsAverage 2 1.5 3 other radionuclides were analyzed - none were detected

DISINFECTANT RESIDUALS / DISINFECTION BY-PRODUCTS
Bromate [g] ppb 10 0.1 Range ND - 14.0 ND By-product of drinking water ozonationHighest RAA 7.6 ND
MRDL MRDLG System-wide
City of Thousand
Oaks Results
Total Chlorine Residual [h] ppm 4 4 Range 1.23 - 1.83 N/A Drinking water disinfectant added for treatmentHighest RAA 1.59 N/A
Haloacetic Acids [i] (HAA5) ppb 60 N/A Range 5.0 - 15 N/A By-product of drinking water disinfectionHighest LRAA 8.9 N/A
Total Trihalomethanes [i] ppb 80 N/A Range 11 - 51 N/A By-product of drinking water disinfection(TTHM) Highest LRAA 26 N/A
SECONDARY DRINKING WATER STANDARDS (SDWS) - Aesthetic Standards Aluminum [c] ppb 200 600 Range ND - 83 ND Erosion of natural deposits; residue from water treatment processesHighest RAA ND ND
Chloride ppm 500 N/A Range 48 - 58 105 Runoff/leaching from natural deposits; seawater influenceAverage 53 105
Color Units 15 N/A Range 1 ND Naturally occurring organic materialsAverage 1 ND
Odor Threshold TON Units 3 -- Range 2 ND Naturally occurring organic materialsAverage 2 ND
Specific Conductance µS/cm 1600 N/A Range 578 - 604 752 Substances that form ions when in water; seawater influenceAverage 591 752
Sulfate ppm 500 N/A Range 95 - 112 98 Runoff/leaching from natural depositsAverage 104 98
Total Dissolved Solids ppm 1000 N/A Range 357 - 367 420 Runoff/leaching from natural depositsAverage 362 420
9 other metals and constituents were analyzed - none were detected ADDITIONAL PARAMETERS (Unregulated)
Alkalinity ppm NS NS Range 85 - 102 120
Average 94 120
Boron ppm NL=1 NS Range 0.2 0.2
Average 0.2 0.2
Calcium ppm NS NS Range 39 - 40 36
Average 40 36
Corrosivity [j] AI NS NS Range 12.2 - 12.6 12.1
Average 12.4 12.1
Hardness (Total Hardness) ppm NS NS Range 138 - 153 156 138 ppm = 8.07 grains per gallon (gpg)
Average 146 156 156 ppm = 9.12 gpg
Magnesium ppm NS NS Range 10 - 12 16
Average 11 16
N-Nitrosodimethylamine ppt NL = 10 3 Range 3.5 ND
(NDMA) Average 3.5 ND
pH pH units NS NS Range 8.2 - 8.6 8.1
Average 8.4 8.1
Potassium ppm NS NS Range 2.4 - 2.6 4.0
Average 2.5 4.0
Sodium ppm NS NS Range 60 - 68 81
Average 64 81
Total Organic Carbon ppm TT Range 1.4 - 2.6 1.8
Average 2.1 1.8
Vanadium ppb NL = 50 NS Range 3.9 ND
Average 3.9 ND
13 other constituents and metals were analyzed including Radon - none were detected Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) List (Unregulated) [k] 29 PFAS constituents were analyzed - none were detected AI = Aggressiveness Index.

AL = Federal Regulatory Action Level = The level of contaminant which when exceeded, triggers treatment or other requirements that a water system must follow.

DBP = Disinfection By-Product
LBWFP = Lake Bard Water Filtration Plant.

MCLG = Maximum Contaminant Level Goal = The level of
contaminant in drinking water below which there is no known or expected risk to health. MCLGs are set by the US Environmental Protection Agency (EPA).

MWD = Metropolitan Water District.

N/A = Not Applicable
ND = None Detected. Detection Limits for the purposes of reporting (DLRs) available on request.

NL = Notification Level
NS = No Standard
NTU = Nephelometric Turbidity Units.
pCi/L = Picocuries per liter (units to measure radiation).

PHG = Public Health Goal = The level of contaminant in drinking water below which there is no known or expected risk to health.

PHGs are set by the California Environmental Protection Agency (Cal-EPA).

Primary Drinking Water Standard (PDWS) = MCLs, MRDLs and treatment techniques (TTs) for contaminants that affect health, along with their monitoring and reporting requirements. ppm = parts per million, or milligrams per liter (mg/L), equivalent to 1 drop of water in a aquarium (13.3 gallons).
ppb = parts per billion, or micrograms per Liter (µg/L), equivalent to 1 drop of water in a standard swimming pool (13,333 gallons). ppt = parts per trillion, or nanograms per Liter (ng/L), equivalent to 1 drop of water in 20 olympic swimming pools (13,333,333 gallons).

W ATER QUALITY DATA
Abbreviations, Definitions and Notes
[a] The turbidity level of the filtered water shall be less than or equal to 0.3 NTU in 95% of the measurements taken each
month and shall not exceed 1.0 NTU at any time. Turbidity is a measure of the cloudiness of the water. We monitor it because it is a good indicator of the effectiveness of the filtration system.
[b] The City’s water was in compliance with both the State Total Coliform Rule and the Federal Revised Total Coliform Rule.

Over 1,000 samples were analyzed in 2023 for Total Coliform and E. Coli.
[c] Aluminum has both primary and secondary standards.

Compliance with the MCL is based on a running annual
average. The secondary standard MCL was not exceeded.
[d] Lead and Copper are sampled at the customer’s tap every 3 years. Last event was conducted in 2022 and scheduled to occur again in 2025. 35 samples were collected and the 90th percentile was reported above. No samples exceeded the AL for Lead and Copper.
[e] MWD initiated a Fluoride Optimization Program in 2007. See text for further detail.
[f] The MWD’s results are from 2023, part of a 4-quarter radiological monitoring program. Calleguas conducts
radiological monitoring annually. Water utilities are required to make these surveys every three years.
[g] Compliance for treatment plants that use ozone is based on a running annual average of monthly samples, which was in compliance in 2023.
[h] Total chlorine residual measures the concentration of chloromines (5 parts chlorine and 1 part ammonia) that are added as a disinfectant system-wide.
[i] Compliance was based on the LRAA of data collected at distribution system-wide monitoring locations. The range of all samples collected is included.
[j] AI measures the aggressiveness of water transported through pipes. AI <10 is highly corrossive to water system materials. AI at 12 or above indicates non-aggressive water. [k] Consumer confidence report (CCR) detection limits are based on method detection limit for the EPA 533 and 537.1 Methods. Results below CCR detection limits are considered ND. PFAS results below CCR detection limits but above
reporting limits are included in this report.

TON = Threshold Odor Number
TT = Standards are Treatment Techniques for contaminants with which MWD and Calleguas are in compliance.
µS/cm = micro Siemen per Centimeter (to measure conductivity) © 2024 Goldstreet Design Agency, Inc. All Rights Reserved www.toaks.org/waterqualityreport
For additional information about your drinking
water, contact the Water Quality Supervisor in the
Public Works Department at 805-449-2499.

The City of Thousand Oaks (City) Public Works
Department distributes up to 15 million gallons of water each day to roughly 17,000 residences and businesses.

OUR MISSION
Este reporte contiene las instrucciones más re -
cientes para obtener información importante sobre
su agua potable. Traduzcalo o hable con alguien
que lo entienda bien, si necesita hablar con alguien
en español favor de comunicarse al 805-449-2499.
(Reporting 2024 Data) PWSID # 5610020
ATTACHMENT #2
DPW:1025-40\ev\Council\2025\09232025\Tr iennial PHG Water Quality Att 2.pdf

PUBLIC EDUCATION
The City is pleased to present to you this year’s Annual Water Quality Report, which shows that the City’s water supply met or exceeded all State and Federal standards in 2024. We are committed to providing you with this information in the sincere belief that informed customers are our best partners. Included in this report are details about where your water comes from, what it contains, and how it compares to State standards. The City works very hard with our neighbors, our partners, and suppliers to continually improve the quality of the water supply, the protection of our water sources, the dependability of supply, and the integrity of our storage and distribution system.

PUBLIC PARTICIPATION
The City drinking water system is managed as an enterprise fund by the elected City Council. Operations are conducted by the Public Works Department. The City Council meets on Tuesday evenings at 6 PM in the Scherr Forum Theater in the Civic Arts Plaza located at 2100 Thousand Oaks Blvd. For information about Council meeting schedules, please call 805-449-2151 or visit www.toaks.gov.

OUR W ATER SOURCES IN 2024
98% of the City’s water supply was from the State Water Project. This surface water is imported from Northern
California, which originates at Lake Oroville. The water then flows through the Sacramento River Delta system
and is transported via the California Aqueduct to Southern California. The water is treated, filtered, and disinfected at the Metropolitan Water District’s (MWD) Jensen Filtration Plant in Granada Hills. This water supply is then piped directly to the City through the transmission facilities of the Calleguas Municipal Water District (Calleguas) located in Thousand Oaks. The last 2% of the City’s water supply came from the Calleguas Lake Bard Reservoir and Water
Filtration Plant.

Should these water sources be interrupted by general
maintenance, earthquake, or other calamity, Calleguas
can deliver water to the City solely from their Las Posas Wellfields and their Lake Bard Reservoir and Water
Filtration Plant.

PUBLIC HEALTH
Some people may be more vulnerable to contaminants in drinking water than the general population. Immuno-compromised persons such as those with cancer who are 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 their drinking water from their healthcare providers. The USEPA and the Centers for Disease Control guidelines on appropriate means to lessen the risk of infection by Cryptosporidium and other microbial contaminants are available from the USEPA Safe Drinking Water Hotline (800-426-4791).

Fluoride - MWD initiated a Fluoride Optimization Program in November of 2007. Naturally occurring fluoride level ranges from 0.1 to 0.4 mg/L (parts per million). MWD has adjusted the level to the optimal range for dental health of 0.7 mg/L. If you or your children are taking Fluoride supplements, please consult with your dentist or dental healthcare provider for further direction.

Organic chemical contaminants, including synthetic and volatile organic chemicals, are by-products of industrial processes and petroleum production, and can also come from gas stations, urban stormwater run-off, agricultural applications, and septic systems.

Microbial contaminants, such as viruses and bacteria may come from sewage collection systems, septic systems, agricultural livestock operations, and wildlife.

Radiological contaminants can be naturally occurring or the result of oil and gas production and mining activities.

Pesticides and Herbicides may come from a variety of sources such as agriculture, residential uses, and urban stormwater run-off.

Lead can cause serious health effects in people of all ages, especially pregnant people, infants (both formula-fed and breastfed), and young children. Lead in drinking water is primarily from materials and parts used in service lines and in home plumbing. The City is responsible for providing high-quality drinking water and removing lead pipes but cannot control the variety of materials used in the plumbing in your home. Because lead levels may vary over time, lead exposure is possible even when your tap 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 Miles
0 21
City Limits
Water Mains
Water Service Area
23 101
City of Thousand Oaks
Water System
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. You can do this by running your tap, taking a shower, doing laundry or a load of 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. If you are concerned about lead in your water and wish to have your water tested for lead, contact the Water Quality Supervisor in the Public Works Department at 805-449-2499. Information on lead in drinking water, testing methods, and steps you can take to minimize exposure is available from the US EPA Safe Drinking Water Hotline (1- 800-426-4791) or at http://www.epa.gov/safewater/lead.

The City has prepared a lead service line inventory report that can be found at https://toaks.co/leadservicelinereport . The City’s distribution system has no lead service lines.

MWD has conducted a source water assessment of its State Water Project supplies. State Water Project supplies are most vulnerable to urban/stormwater runoff, wildlife, agriculture, recreation, and wastewater. A copy of the assessment can be obtained by contacting MWD by phone at (213-217-6000).

To ensure that tap water is safe to drink, the US EPA and SWRCB prescribe regulations that limit the amount of certain contaminants in water provided by public water systems. U.S. Food and Drug Administration regulations and California law also establish limits for contaminants in bottled water that provide the same protection for public health. The quality of our drinking water meets all State requirements for safe water.

The following table lists the drinking water contaminants that were detected in the City’s drinking water during 2024. The presence of any of these contaminants in the water does not necessarily constitute a health risk. As you can determine from the results, the quality of the water delivered by the City consistently meets all State standards. The data presented in this table is from testing performed between January 1 and December 31, 2024, unless otherwise noted. State of California Standards are either equal to or more stringent than Federal USEPA water quality standards. Therefore, Federal MCLs are not listed. Applicable Abbreviations, Definitions, and Notes are identified after the Table.

W ATER QUALITY DATA
Parameter Units
State

MCL-MRDL
PHG
(MCLG)-MRDLG
Range
Average
MWD Jensen Plant
98% of Supply
Calleguas LBWFP
2% of Supply
Potential Major Sources if
Detected in Drinking Water
PRIMARY DRINKING WATER STANDARDS (PDWS) - Mandatory Health-Related Standards CLARITY [a]
Combined Filter
Effluent Turbidity NTU 0.3 Highest
Value 0.04 0.14 Soil runoff
TT= % of samples ≤0.3 NTU [a] 100% 100%
MICROBIOLOGICAL [b]
Total Coliform Bacteria % of
Samples 5 % 0 Highest
Monthly % 0 N/A Naturally present in the
environment
(State Revised Total
Coliform Rule, Effective
July 1, 2021)
Standards for Cryptosporidium, Giardia lamblia, Legionella, viruses and Heterotrophic Plate Count Bacteria are Treatment Techniques (TT) with which MWD and Calleguas comply. There were no detections of fecal coliform or E. Coli bacteria in the City’s distribution system in 2024.

Parameter Units
State

MCL-MRDL
PHG
(MCLG)-MRDLG
Range
Average
MWD Jensen Plant
98% of Supply
Calleguas LBWFP
2% of Supply
Potential Major Sources if
Detected in Drinking Water

INORGANIC CHEMICALS
Aluminum [c] ppb 1000 600 Range 52 - 91 ND Erosion of natural deposits; residue from water treatment processHighest RAA 62 ND
Arsenic ppb 10 0.004 Range ND 2.0 - 4.0 Erosion of natural deposits; runoff from orchards; electronics production
wastesAverage ND 3.0
Copper [d] ppm AL=1.3 0.3 Range ND - 0.20 N/A Internal corrosion of household pipes; erosion of natural deposits90th % 0.15 N/A
Fluoride [e] ppm 2.0 1 Range 0.6 - 1.0 N/A Water additive that promotes strong teethTreatment-related Highest RAA 0.7 N/A
Lead [d] ppb AL=15 0.2 Range ND - 5.4 N/A Internal corrosion of household pipes; erosion of natural deposits90th % 2.2 N/A
Nitrate (as N) ppm 10 10 Range 0.5 ND Runoff & leaching from fertilizer use; erosion of natural depositsAverage 0.5 ND
Selenium ppb 50 30 Range ND ND - 6 Erosion of natural deposits; discharge from oil & metal refineriesAverage ND ND
15 other metals and chemicals were analyzed (including Asbestos, Chromium, Cyanide, Mercury and Perchlorate) none were detected. Copper and Lead were not detected in the water supply.

Pesticides/PCBs
28 chemicals were analyzed

MCL-MRDL
PHG
(MCLG)-MRDLG
Range
Average
MWD Jensen
Plant 98% of
Supply
Calleguas
LBWFP 2% of
Supply
Potential Major Sources if
Detected in Drinking WaterParameter Units
RADIONUCLIDES [f] [analyzed every three years, for four consecutive quarters] Gross Beta Particle Activity pCi/L 50 (0) Range ND 5.4 - 5.6 Decay of natural & man-made depositsAverage ND 5.5
Uranium pCi/L 20 0.43 Range 2.0 - 3.0 1.4 - 1.5 Erosion of natural depositsAverage 2 1.5 4 other radionuclides were analyzed - none were detected

DISINFECTANT RESIDUALS / DISINFECTION BY-PRODUCTS
Bromate [g] ppb 10 0.1 Range ND - 5.4 ND By-product of drinking water ozonationHighest RAA 3.1 ND
MRDL MRDLG System-wide
City of Thousand
Oaks Results
Total Chlorine Residual [h] ppm 4 4 Range 1.18 - 1.94 N/A Drinking water disinfectant added for treatmentHighest RAA 1.53 N/A
Haloacetic Acids [i] ppb 60 N/A Range 0 - 9.3 N/A By-product of drinking water disinfection(HAA5) Highest LRAA 6.7 N/A
Total Trihalomethanes [i] ppb 80 N/A Range 13 - 20 N/A By-product of drinking water disinfection(TTHM) Highest LRAA 17.8 N/A
SECONDARY DRINKING WATER STANDARDS (SDWS) - Aesthetic Standards Aluminum [c] ppb 200 600 Range 52 - 91 ND Erosion of natural deposits; residue from water treatment processesHighest RAA 62 ND
Chloride ppm 500 N/A Range 39 - 41 99 - 100 Runoff/leaching from natural deposits; seawater influenceAverage 40 99
Color Units 15 N/A Range 1 ND Naturally occurring organic materialsAverage 1 ND
Odor Threshold TON Units 3 -- Range 1 ND Naturally occurring organic materialsAverage 1 ND
Specific Conductance µS/cm 1600 N/A Range 498 - 522 773 - 790 Substances that form ions when in water; seawater influenceAverage 510 782
Sulfate ppm 500 N/A Range 89 - 92 102 - 103 Runoff/leaching from natural depositsAverage 90 103
Total Dissolved Solids ppm 1000 N/A Range 291 - 322 410 - 450 Runoff/leaching from natural depositsAverage 306 430
Zinc ppm 5.0 N/A Range ND 0.06 Runoff/leaching from natural depositsAverage ND 0.06
8 other metals and constituents were analyzed - none were detected ADDITIONAL PARAMETERS (Unregulated)
Alkalinity, total as CaCO3 ppm NS NS Range 94 - 101 120 - 130 Average 98 125
Boron ppm NL=1 NS Range 0.17 0.27 - 0.28
Average 0.17 0.28
Calcium ppm NS NS Range 38 - 39 36 - 38
Average 38 37
Corrosivity [j] AI NS NS Range 12.2 12.1 - 12.4
Average 12.2 12.3
Hardness (Total Hardness) ppm NS NS Range 143 - 153 160 - 165 148 ppm = 8.65 grains per gallon (gpg)
Average 148 163 163 ppm = 9.53 gpg
Magnesium ppm NS NS Range 13 - 14 17
Average 14 17
pH pH units NS NS Range 8.2 - 8.3 8.1 - 8.3
Average 8.3 8.2
Potassium ppm NS NS Range 2.6 4.0
Average 2.6 4.0
Sodium ppm NS NS Range 46 86 - 91
Average 46 89
Total Organic Carbon ppm TT Range 2.0 - 2.5 2.6 - 2.8
Average 2.4 2.7
14 other constituents and metals were analyzed including Radon - none were detected Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) List (Unregulated) [k] 29 PFAS constituents were analyzed - none were detected AI = Aggressiveness Index.

AL = Federal Regulatory Action Level = The level of contaminant which when exceeded, triggers treatment or other requirements that a water system must follow.

DBP = Disinfection By-Product
LBWFP = Lake Bard Water Filtration Plant.

LRAA = Locational Running Annual Average
MCL = Maximum Contaminant Level = The highest level of 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 are set to protect the odor, taste, and appearance of drinking water.

MCLG = Maximum Contaminant Level Goal = The level of contaminant in drinking water below which there is no known or expected risk to health.

MCLGs are set by the US Environmental Protection Agency (EPA).

MWD = Metropolitan Water District.

N/A = Not Applicable
ND = None Detected. Detection Limits for the purposes of reporting (DLRs) available on request.

NL = Notification Level
NS = No Standard
NTU = Nephelometric Turbidity Units.

Primary Drinking Water Standard (PDWS) = MCLs, MRDLs and treatment techniques (TTs) for contaminants that affect health, along with their monitoring and reporting requirements.
pCi/L = Picocuries per liter (units to measure radiation). ppm = parts per million, or milligrams per liter (mg/L), equivalent to 1 drop of water in a aquarium (13.3 gallons).
ppb = parts per billion, or micrograms per Liter (µg/L), equivalent to 1 drop of water in a standard swimming pool (13,333 gallons). ppt = parts per trillion, or nanograms per Liter (ng/L), equivalent to 1 drop of water in 20 olympic swimming pools (13,333,333 gallons).

TT = Standards are Treatment Techniques for contaminants with which MWD and Calleguas are in compliance.
µS/cm = micro Siemen per Centimeter (units to measure conductivity)

Over 1,000 samples were analyzed in 2024 for Total Coliform and E. Coli.
[c] Aluminum has both primary and secondary standards.

Compliance with the MCL is based on a running annual
average. The secondary standard MCL was not exceeded.
[d] Lead and Copper are sampled at the customer’s tap every 3 years. Last event was conducted in 2022 and scheduled to occur again in 2025. 35 samples were collected and the 90th percentile was reported above. No samples exceeded the AL for Lead and Copper.
[e] MWD initiated a Fluoride Optimization Program in 2007. See text for further detail.
[f] The MWD’s results are from 2023, part of a 4-quarter radiological monitoring program. Calleguas conducts
radiological monitoring annually. Water utilities are required to make these surveys every three years.
[g] Compliance for treatment plants that use ozone is based on a running annual average of monthly samples, which was in compliance in 2024.
[h] Total chlorine residual measures the concentration of chloromines (5 parts chlorine and 1 part ammonia) that are added as a disinfectant system-wide.
[i] Compliance was based on the LRAA of data collected at distribution system-wide monitoring locations. The range of all samples collected is included.
[j] AI measures the aggressiveness of water transported through pipes. AI <10 is highly corrossive to water system materials. AI at 12 or above indicates non-aggressive water.
[k] Consumer confidence report (CCR) detection limits are based on method reporting limit for the EPA 533 and 537.1 Methods.

Results below CCR detection limits are considered ND. PFAS results below CCR detection limits but above reporting limits are included in this report.
© 2025 Goldstreet Design Agency, Inc. All Rights Reserved www.toaks.co/waterqualityreport

Thousand Oaks City CouncilSeptember 23, 2025

Thousand Oaks City Council
September 23, 2025