OUR MISSION: To provide our customers with high-quality, efficient and reliable water, power and sewer services in a manner that values environmental and community interests and sustains the resources entrusted to our care.
Water Quality Division
1657 Rollins Rd
Burlingame, CA 94010
T 650.652.3100
F 650.692.6704
June 3, 2025
TO: Commis
sioner Kate Stacy, President
Commissioner Joshua Arce, Vice President
Commissioner Avni Jamdar
Commissioner Steve Leveroni
Commissioner Meghan Thurlow
THROUGH:
Dennis J. Herrera, General Manager
Steve R. Ritchie, Assistant General Manager – Water Enterprise FROM: A
ndrew DeGraca, Water Quality Division Director
SUBJE
CT: 2025 Public Health Goal Report
Atta
ched for your review is the triennial Public Health Goal (PHG) Report. It is required under California Health and Safety Code §116470(b) through (f), of which sub-section (c) requires a public hearing be held for the purpose of accepting and responding to public comment on the report. The required public hearing is tentatively scheduled to be part of a Commission meeting in September 2025 for the purpose of accepting and responding to public comments on the PHG report.
PHGs ar
e non-enforceable, numerical health protection goals adopted by the California Office of Environmental Health Hazard Assessment (OEHHA). Basically, a PHG is the level of a contaminant in drinking water that does not pose a significant risk to health.
The law requires a water system with more than 10,000 service connections, like the San Francisco Water System (SFWS), to prepare a PHG report every three years if any contaminant in drinking water is found at a level above its PHG during the reporting period. When a PHG has not been adopted for a contaminant by OEHHA, the water system must use the Maximum Contaminant Level Goal (MCLG) adopted by the U.S.
Environmental Protection Agency (USEPA) for evaluation.
Unli
ke the enforceable drinking water standards such as Maximum Contaminant Levels (MCLs) or treatment techniques, with which all public water systems are required to comply, both PHGs and MCLGs are ideal health protection levels that do not consider economic and technical feasibility of treatment. In cases where the PHG or MCLG (in the absence of PHG) of a contaminant that has an established MCL is exceeded, water systems must identify the existing best available technology (BAT) commercially available and estimate the cost to reduce the level of the contaminant to below or at its PHG, regardless of how minimal the risk may be. However, §116470(d)
2025 PHG Report Page 2 of 4
Memo to Commissioners June 3, 2025
mandates that the State Water Resources Control Board (SWRCB) shall not require a water system to take any action to reduce or eliminate any exceedance of a PHG.
This PHG Report provides the Commissioners and the public with information on water quality, numerical health risks, any identified best available technology, treatment cost estimates, and actions being implemented/recommended by staff in response to contaminants exceeding PHGs. Overall, the SFWS complies with all enforceable health-based drinking water standards adopted by the SWRCB and the USEPA between 2022 and 2024 (herein the reporting period). However, three drinking water contaminants were detected at levels above the corresponding PHGs. These include bromate, hexavalent chromium (Cr-6), and lead. The following are highlights of the report:
1. Bromate in drinking water is typically a disinfection byproduct from ozonation in the presence of bromide. It is a probable human carcinogen, and it can also cause non-cancer adverse health effects like hyperplasia. This contaminant was detected in the treated water from Harry Tracy Water Treatment Plant with a maximum running annual average value of 3 parts per billion (ppb). It was below the MCL of 10 ppb but was above the PHG of 0.1 ppb. Several available technologies were identified with very preliminary estimates of annualized treatment costs. These could increase the annual water rate by at least $42 to $312 for each customer served by the SFWS. The USEPA and the SWRCB have identified that optimal control of ozone dosage in the treatment process is the BAT for reducing bromate formation. Staff has already implemented optimal ozone dosages, but the variation of the naturally occurring bromide in the raw water presents a continuing challenge in reducing bromate formation. As such, a regular monitoring program for trending the seasonal variation of bromide levels in raw water is maintained in conjunction with optimum control of ozone dosage in the treatment process.
2. The SWRCB adopted a MCL of 10 ppb for Cr-6 in late 2024. The OEHHA developed the PHG based on toxic effects from both oral and inhalation exposure to Cr-6 that may be present in drinking water. Cr-6 is known to be naturally occurring in groundwater and surface waters but also can enter the environment from industrial sources. The SFPUC initiated Cr-6 monitoring at approved surface water sources in 2002. In 2018, the SFWS began its groundwater supply to the Sunset Reservoir with the SWRCB approval of using blending in the reservoir for the reduction of Cr-6 to below the MCL. In the reporting period, Cr-6 was detected in both non-Hetch Hetchy surface water sources and local groundwater sources. These detections were either at or above the PHG of 0.02 ppb with all results below the MCL in treated or blended water supplies. Although the SWRCB has identified BAT treatments for Cr-6, none of them are intended to reduce the contaminant to a level below or at the PHG. Based on very preliminary estimates of annualized costs associated with the applicable anion- exchange treatment, the corresponding increase in the water rate could range from $92 2025 PHG Report Page 3 of 4
Memo to Commissioners June 3, 2025
to $1,800 for each customer served by the SFWS. As no anthropogenic sources have been identified in our groundwater and surface water sources and the current Cr-6 levels in the drinking water supplied by the SFWS are well below the MCL through blending, additional treatment is not considered a cost-effective measure to control the naturally occurring Cr-6 in the water sources.
3. Our latest triennial customer tap monitoring in 2024 continued demonstrating that no lead was in the system water. All results of the tap monitoring were below the regulatory Action Level of 15 ppb, although the 90th percentile value of 4.9 ppb was above the PHG of 0.2 ppb. According to OEHHA, lead is toxic and has multiple chronic health effects including negative neurobehavioral effects in children and hypertension in adults. It also has the potential to cause kidney disease and cancer. Lead enters drinking water primarily through leaching of lead-containing materials in household plumbing and some service lines between water mains and houses. The USEPA and the SWRCB consider a combination of actions by utilities as equivalent to BAT. These actions include, but are not limited to, corrosion control optimization, replacement of identified lead service lines, monitoring of lead at select customer taps and appropriate water quality parameters in the distribution system, and proactive public outreach to educate customers. We will continue the following actions in the SFWS, and implement additional programs as needed, to assist customers in reducing lead exposure from drinking water.
Ongoing Actions
• Practice optimal corrosion control treatment.
• Replace meters and curb stop valves with lead-free units, if found. • Offer low-cost lead tests for City customers and free lead tests for enrollees of the Woman, Infants, and Children Program.
• Provide analytical service in support of the lead reduction efforts of San Francisco Department of Public Health.
• Conduct proactive public outreach to inform consumers of lead's health risks and ways of minimizing lead exposure from drinking water. • Complete replacement of remaining lead user service lines on the utility side of water meters before 2030.
• Keep updating the material inventory and associated location map for utility- side and customer-side service lines.
Additional Programs
• Collaborate with the SFUSD on lead monitoring at K-12 schools and childcare facilities.
• Identify new Tier 3 sites to recruit volunteers for future lead and copper monitoring under the USEPA's new regulatory requirements related to the Lead and Copper Rule Improvements. These are homes that had a lead utility service line previously removed and have a galvanized customer service line. 2025 PHG Report Page 4 of 4
Memo to Commissioners June 3, 2025
• Evaluate potential methods to facilitate replacement of the customer-side galvanized service lines requiring replacement per the Lead and Copper Rule Improvements.
In summary, the SFPUC has already implemented the BATs that are effective in controlling and minimizing customer exposure to the three contaminants detected above their PHGs. Drinking water that meets the MCLs is considered acceptable for public consumption, even if it contains contaminants at levels exceeding the PHGs.
The identified treatment technologies above are meant for reducing the corresponding contaminants to achieve MCL compliance only, whereas their performance and effectiveness to attain a level at or below the PHG have not been demonstrated commercially. As such, implementing additional treatment technologies to further reduce the currently MCL-compliant parameters to PHG levels is not warranted.
Encl.: 2025 Public Health Goal Report for San Francisco Water System
cc: Bill Teahan, San Francisco Water Division
Enio Sebastiani, Water Quality Division
Eddy So, Water Quality Division
Records Management, Water Quality Division
2025 Public Health Goal Report
For
San Francisco Water System
Prepared by:
San Francisco Public Utilities Commission
Water Quality Division
1657 Rollins Road
Burlingame, CA 94010
D
ate: M ay 28, 2025
ii
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iii
Acronyms and Abbreviations
ACWA Association of California Water Agencies
BAT Best Available Technology
CHSC California Health and Safety Code
DBP Disinfection By-Product
DLR Detection Limit for the Purposes of Reporting
HTWTP Harry Tracy Water Treatment Plant
LUSL Lead User Service Line
MCL Maximum Contaminant Level
MCLG
MGD
Maximum Contaminant Level Goal
Million Gallons per Day
O&M Operations and Maintenance
OEHHA Office of Environmental Health Hazard Assessment
PHG Public Health Goal
ppb Part per Billion
SFDPH San Francisco Department of Public Health
SFGW San Francisco Groundwater Project
SFPUC San Francisco Public Utilities Commission
SFWS San Francisco Water System
SVWTP Sunol Valley Water Treatment Plant
SWRCB State Water Resources Control Board
USEPA
TT
LCR
United States Environmental Protection Agency
Treatment Technique
Lead and Copper Rule
iv
RAA
POE
GRR
LCRI
Running Annual Average
Points Of Entry
Galvanized Steel Pipeline Requiring Replacement
Lead and Copper Rule Improvements
v
San Francisco Water System
2025 Public Health Goal Report
Table of Contents
I. Introduction ..................................................................................................................................... 1 A. Regulatory Requirements .......................................................................................................... 1 B. Public Health Goal (PHG) and Maximum Contaminant Level (MCL) ..................................... 1 C. Guidelines .................................................................................................................................. 2 D. Water Supplies to San Francisco Water System (SFWS)...…………………………………...2 II. Elements of PHG Report ............................................................................................................... 2 A. Target Drinking Water Contaminant Levels ............................................................................. 2
1. Detection Limit for Reporting Purposes ....................................................................... 3
2. Exceedance .................................................................................................................... 3 B. Health Risks ............................................................................................................................... 3 C. Best Available Technology (BAT) and Treatment Cost Estimate ............................................. 4 D. SFWS Programs......................................................................................................................... 5 III. Water Quality Data and Analysis ............................................................................................... 5 A. Contaminants Detected above PHGs/MCLGs ........................................................................... 5 B. Contaminants that Meet Requirements of Treatment Techniques ............................................. 6 IV. Evaluation of Contaminants Exceeding PHGs or MCLGs ....................................................... 6 A. Bromate ..................................................................................................................................... 6
1. Water Sample Results ................................................................................................... 7
2. Health Risk Category and Level ................................................................................... 7
3. BAT and Treatment Cost Estimate ............................................................................... 8
4. SFWS Programs ............................................................................................................ 8 B. Hexavalent Chromium (Cr-6) .................................................................................................... 8
1. Water Sample Results ................................................................................................... 9
2. Health Risk Category and Level ................................................................................... 9
3. BAT and Treatment Cost Estimate ............................................................................. 11
4. SFWS Programs .......................................................................................................... 11
vi
C. Lead ......................................................................................................................................... 11
1. Water Sample Results ................................................................................................. 13
2. Health Risk Category and Level ................................................................................. 13
3. BAT and Treatment Cost Estimate ............................................................................. 13
4. SFWS Programs .......................................................................................................... 14 V. Recommendations for Further Actions ...................................................................................... 16
vii
Tables
1 Contaminants Detected Above PHGs/MCLGs ............................................................................. 5 2 Summary of Bromate Monthly Results in Reporting Period ........................................................ 7
3. Cr-6 Level in Compliance Samples for SFWS and Supply Sources in Reporting Period ……..10
Figures
1. S FWS Water Quality Targets vs. PHGs/MCLGs and MCLs ....................................................... 3
2. Potential Contributors to Lead in Tap Water from Household Plumbing ................................... 12
Attachments
A Excerpt from California Health and Safety Code, Section 116470(b)- (f) B Health Risk Information for Public Health Goal Exceedance Reports C SFWS Water Quality Reports – 2022, 2023, and 2024
D. Bromate Technical Assessment and Cost Estimate for 2025 Public Health Goal Report E. Hexavalent Chromium Technical Assessment and Cost Estimate for 2025 Public Health Goal Report
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2025 Public Health Goal Report San Francisco Water System 1 San Francisco Water System
2025 Public Health Goal (PHG) Report
I. Introduction
A. Regulatory Requirements
California Health and Safety Code (CHSC) §116470(b)-(f) (Attachment A) requires a public water system with more than 10,000 service connections to prepare a brief written report by July 1, triennially, for any contaminant that exceeds its Public Health Goal (PHG) in drinking water. The report, which is referred to as the PHG Report herein, is to provide consumers with the following information:
• Each contaminant that exceeds the applicable PHG in drinking water, • Numerical public health risk, including the risk category for the contaminant, associated with the maximum contaminant level (MCL) and the PHG,
• Any commercially available best technology and associated cost estimates to reduce the contaminant to a level at or below the PHG, and
• Actions already taken, or intended to be taken, by the water system to reduce the contaminant in drinking water supplies.
Wat er systems are required to use the applicable maximum contaminant level goal (MCLG) adopted by the United States Environmental Protection Agency (USEPA) if no PHG is available. While the primary drinking water standards, which are expressed in MCLs or as treatment technique (TT) are enforceable, both the PHGs and the MCLGs are not. Systems preparing the PHG Report are required to hold a hearing for the purpose of accepting and responding to public comment on the report.
The period f or this report covers the years between 2022 and 2024, inclusively (Reporting Period).
B. PHG and MCL
PHGs are published by the California Office of Environmental Health Hazard Assessment (OEHHA) to support the MCL development effort of the State Water Resources Control Board (SWRCB). A PHG is the concentration of a contaminant in drinking water that poses no significant health risk if consumed for a lifetime, whereas the MCL is set as close to the PHGs, or MCLGs, as is economically and technologically feasible.
A PHG is based solely on public health risk using current risk assessment principles and methods, without consideration of practical risk-management factors, which are used by the SWRCB to set enforceable drinking water standards. MCLG is determined by the USEPA using a similar process. However, the USEPA sets the MCLGs of all carcinogens at zero, even though the goal of zero is difficult or impossible to meet.
Therefore, adopted MCLs are the criteria for regulatory compliance determination by the regulatory agencies, not those proposed or possible MCLs in the future and certainly not MCLGs or PHGs. 2025 Public Health Goal Report San Francisco Water System 2 C. Guidelines
San Francisco Public Utilities Commission (SFPUC) staff prepared its first PHG report for the San Francisco Water System (SFWS) in 1998 without any regulatory guidance. The Association of California Water Agencies (ACWA) developed its first guidelines to help water systems prepare the PHG report in 2007. The guidelines, though not of a regulatory nature, provide a structured approach to enhance consistency in PHG report preparation among water systems across the State of California. However, water systems may still use their own protocols in handling data review/analysis and treatment evaluation. The SFPUC has essentially used the latest available ACWA guidelines, April 2025, in the preparation of this PHG report.
D. Water Supply to SFWS
The SFWS’s drinking water is supplied by its wholesaler, San Francisco Regional Water System (SFRWS), and is supplemented with a small contribution from its own local groundwater sources1. Although both SFWS and SFRWS are operated by the SFPUC, these two water systems are separately permitted by the SWRCB.
Each water system has its own regulatory responsibilities to fulfill. All treatment and watershed management of the surface water sources are the responsibility of the SFRWS, whereas the SFWS is responsible for the operations and maintenance of its own distribution system and local groundwater wells that are within the City and County of San Francisco. As a wholesaler, the SFRWS delivers drinking water, which is typically a blend of unfiltered water from Hetch Hetchy Reservoir and filtered water from two treatment plants using local surface water sources. The contribution of each water source in the blend varies throughout the year.
II. Elements of PHG Report
This section discusses the key elements of the report that will help explain the significance of a PHG exceedance. These include target drinking water levels, health risks, identified best available technology (BAT) and cost estimates, and SFPUC programs. Only contaminants that have an existing primary drinking water standard and were “detected” at a level that “exceeds” the existing PHG or MCLG are included in the report. There are a few constituents, including total trihalomethanes and five haloacetic acids, that are routinely detected in water systems at levels usually well below the MCLs for which neither a PHG nor a MCLG exists. These will be addressed in future reports after a PHG or a MCLG has been adopted.
A. Target Drinking Water Contaminant Levels
To ensure that customers receive high-quality drinking water, the SFPUC sets its own operational water quality targets at levels more stringent than the MCLs. These operational target levels help the SFPUC operate the two water systems to prevent MCL violations. Figure 1 is a graphical illustration showing the relative hierarchy of SFWS’s water quality targets, PHGs/MCLGs, DLRs, and MCLs.
1 In this Reporting Period, the local groundwater sources contributed to an average of less than 0.1% of the drinking water delivered to the customers.
2025 Public Health Goal Report San Francisco Water System 3 Figure 1. SFWS Water Quality Targets vs. PHGs/MCLGs and MCLs Contaminants that have existing MCLs or TTs and have confirmed detections in exceedance of the applicable PHGs or MCLGs (if no PHGs available) in drinking water delivered to the SFWS are included in this report.
However, there are two terms worthy of further explanation:
1. Detection Limit for Reporting Purposes
Along with each MCL, the SWRCB also adopted a corresponding Detection Limit for Purposes of Reporting (DLR) to help determine a water system’s compliance with the drinking water standard. When a contaminant has a confirmed level above the DLR, it is considered as “detected” according to the drinking water requirements in Title 22 of the California Code of Regulations (Title 22). Per SWRCB guidance and procedure on compliance reporting, results that are reported below the DLR would be treated as zero for calculation purposes. A similar approach was used for PHG comparison in this report.
2. Exceedance
There are no regulations that relate to data handling for PHG comparison. According to ACWA guidelines and consistent with the procedure acceptable to the SWRCB for MCL compliance determination, this report essentially follows the same approach in evaluating water quality data for PHG comparison. For example, if Title 22 or the SWRCB guidance specifies that the average of a group of samples be compared to the MCL for compliance purposes, the same averaging approach is used to determine the detection level for comparison to the PHG or MCLG. If wells are blended or treated before delivery to the system, the judgment as to whether there was a “detection exceeding the MCLG or PHG” is based on the “point of entry” data just as for compliance with MCLs. As in all cases of reporting results to the SWRCB, the analytical results are rounded to reflect the appropriate number of significant figures matching the corresponding PHG or MCLG.
B. Health Risks
The OEHHA evaluates toxicological data from scientific literature to assess health risks for each contaminant in categories that include, among others, the following:
• Carcinogenic: capable of producing cancer.
DLRs
2025 Public Health Goal Report San Francisco Water System 4 • Cardiovascular toxicity: adverse effects on the structure or function of the heart or the vascular system following exposure to a chemical substance.
• Developmental toxicity: adverse effects on a developing organism that may result from exposure prior to conception (either parent), during prenatal development, or postnatally to the time of sexual maturation. Adverse developmental effects may be detected at any point in the life span of the organism. The major manifestations include (1) death of the developing organism, (2) structural abnormality (birth defects), (3) altered growth, and (4) functional deficiency. • Neurotoxicity: capable of adversely affecting or destroying parts of the nervous system or interfering with nerve signal transmission. Effects may be reversible (for example, effects on chemicals that carry nerve signals across gaps between nerve cells) or irreversible (for example, destruction of nerve cells). • Reproductive toxicity: adverse effects on the reproductive system of females or males. The toxicity may cause changes to the female or male reproductive organs, the regulating endocrine system, or pregnancy outcomes.
OEHHA calculates numerical risks associated with a contaminant’s non-carcinogenic, and carcinogenic effects if any, on human health (Attachment B). The PHG is then developed as a public health-protective concentration based on the most sensitive health effects. For contaminants with non-carcinogenic effects, PHGs are set at concentrations at which no known or anticipated adverse health effects occur. For carcinogens, OEHHA typically establishes PHGs at the risk level of not more than 1 in 1,000,000 additional cases of cancer development as a result of exposure to the contaminants of concern. By regulations, OEHHA cannot set a PHG at zero. However, the USEPA considers no safe level of exposure to carcinogens and sets MCLGs for carcinogens at zero.
C. Best Available Technology (BAT) and Treatment Cost Estimate For drinking water, both the USEPA and the SWRCB have specified BATs that have been determined to be the best available methods for reducing contaminant levels to MCLs. Costs can be readily estimated for such technologies. However, since most PHGs and MCLGs are set much lower than the corresponding MCLs (and some MCLGs are set at zero), it is not always possible to determine what treatment could further reduce a contaminant down from MCL to PHG or MCLG. Estimating the costs to reduce a contaminant to absolute zero is impossible, as it is not technically feasible to verify by existing analytical methods that the level has truly been lowered to zero. Only very preliminary cost estimates, if applicable, are required in PHG reports.
ACWA has compiled unit cost estimates (dollars per thousand gallons treated) for BATs from various sources.
For presenting cost estimates, ACWA guidelines suggest including both total project cost and the cost per customer. As the amount of water used by each SFWS customer varies, this report presents costs in a percent increase of a customer’s water bill. Since other wholesale customers uses approximately two-thirds of SFRWS’s surface water supply, only one third of estimated costs for surface water treatment (if any and to be presumably installed in the SFRWS) will be assigned to SFWS retail customers. However, any estimated costs of additional treatment, if needed, for San Francisco’s own groundwater sources would be solely borne by SFWS retail customers.
It should be noted that installing a treatment system to reduce the already low levels of a single contaminant could have unexpected and adverse consequences on other aspects of water quality.
2025 Public Health Goal Report San Francisco Water System 5 D. SFWS Programs
Other than the applicable BATs, the SFPUC also engages in various water quality efforts in association with these contaminants to enhance public health protection and quality of the drinking water supply. These consist of, but are not limited to, source water protection and watershed management, public outreach, treatment chemical quality assurance, and optimization of treatment and operations.
III. Water Quality Data and Analysis
Drinking water regulations require compliance with MCLs or TTs but not PHGs. Thus, the logical approach for determination of PHG or MCLG exceedance would be to use the same procedures and requirements specified in Title 22 for determining compliance with MCLs. All water quality data collected for regulatory monitoring in the Reporting Period for purposes of determining compliance with drinking water standards were reviewed and considered. These data include those collected at the entry points to the SFRWS and within the SFWS’s own distribution system, as appropriate. A summary of the appropriate concentrations of analytes detected above DLRs in treated water delivered to SFWS customers in 2022, 2023, and 2024 were presented in the corresponding Annual Water Quality Reports (a.k.a. Consumer Confidence Reports) in Attachment C.
A. Contaminants Detected above PHGs/MCLGs
Table 1 summarizes the monitoring results of three contaminants that are found exceeding the applicable PHGs or MCLGs during the Reporting Period.
Table 1. Contaminants Detected above PHGs/MCLGs in SFWS Compliance Determination
Contaminant Unit MCL DLR PHG MCLG RAA(a)
Value Average 90th-
Percentile
Bromate ppb 10 1 0.1 0 3(b) N/A N/A
Hexavalent
Chromium ppb 10 0.1 0.02 - N/A 0.1 N/A
Lead ppb 15(c) 5 0.2 0 N/A N/A 4.9
Notes: (a) MCL compliance is based on the running annual average (RAA) result. (b) This is the calculated highest RAA value over the 3-year Reporting Period. (c) Lead has no MCL but has an Action Level (AL); compliance with which is based on the 90th percentile value of the monitoring results during a Lead and Copper tap monitoring at customer premises.
Key: N/A = not applicable ppb = parts per billion
The data in Table 1 above is based on the following sample collection information:
2025 Public Health Goal Report San Francisco Water System 6 • Bromate exceeded the PHG in monthly samples collected at Harry Tracy Water Treatment Plant (HTWTP) effluent in the Reporting Period.
• Hexavalent chromium exceeded the PHG in annual samples collected at the points of entry to the wholesaler system (SFRWS) but not at the points of entry to the SFWS. However, this contaminant is found exceeding the PHG in the SFWS at the points of entry (Sunset Reservoir) from the blended groundwater and surface water supplies.
• The 90th-percentile value of lead results exceeded the PHG based on customer tap samples collected by the system in 2024 Lead and Copper Rule (LCR) monitoring.
B. Contaminants that Meet Requirements of Treatment Techniques The OEHHA does not establish PHGs for pathogenic microorganisms (i.e., Cryptosporidium, Giardia lamblia, Legionella, heterotrophic bacteria, and viruses). These microorganisms are regulated under the Surface Water Treatment Rule and Long-Term 2 Enhanced Surface Water Treatment Rule. Compliance with these standards is achieved if a water supplier uses prescribed treatment techniques that meet the performance requirements specified in the drinking water regulations. Although the MCLGs for these pathogens are set to zeros, the USEPA does not mandate monitoring as there are no standardized methods that can identify an individual infectious pathogen. The SFPUC performed voluntary monitoring of Giardia lamblia and Cryptosporidium for both the SFRWS and the SFWS during the Reporting Period. These monitoring results are for operational tracking and not for compliance purposes. These contaminants are considered to not have exceeded their MCLGs because the SFPUC continues meeting the TT requirements.
Similarly, there are no primary drinking water standards expressed in MCL values for lead and copper, but the corresponding regulations establish optimized corrosion control treatment as the TT along with tap monitoring results not to exceed the applicable ALs (i.e., 15 ppb for lead and 300 ppb for copper during the Reporting Period).
IV. Evaluation of Contaminants Exceeding PHGs or MCLGs
During the Reporting Period, San Francisco’s drinking water has met all MCLs and TTs adopted by the USEPA and the SWRCB. However, bromate, hexavalent chromium, and lead exceeded the corresponding PHG. The following sections discuss water quality monitoring results and the applicable health goals, associated health risks, identified BATs, if any, and the associated preliminary cost estimates, programs in place or to be implemented by the SFPUC to address these contaminants.
A. Bromate
The OEHHA established a PHG of 0.1 ppb for bromate, which is 1% of the MCL (10 ppb). Bromate salts are used as a food ingredient and a neutralizing agent in hair products. Bromate is usually not found in water sources. In drinking water, bromate is typically formed as a disinfection byproduct from ozonation when naturally occurring bromide reacts with ozone. The HTWTP uses ozone for primary disinfection and pre- oxidation.
2025 Public Health Goal Report San Francisco Water System 7 1. Water Sample Results
Bromate is subject to monthly monitoring at the HTWTP effluent; compliance with the MCL of 10 ppb is determined quarterly based on the annual average results. Since 2020 when the laboratory’s method of analysis was changed with a lower detection limit, bromate has been reported at levels above the SWRCB’s DLR. The highest running annual average value was 3 ppb reported in the 3rd quarter and the 4th quarter of 2024. Whilst all monthly reported values in 2022 and 2023 were between non-detect and 1.9 ppb, the last three quarters of 2024 had much higher monthly detections with a maximum value of 5.9 ppb detected in June 2024. Table 2 summarizes the monthly compliance monitoring results with the corresponding maximum Running Annual Average (RAA), which is the value used for compliance for each year in the Reporting Period. The variations of the bromide level in the raw water and the ozone dosage at the HTWTP dictate the detection levels of bromate in the treated water.
Bromide concentrations in the raw water ranged from 17 ppb to 37 ppb, as reported between 2022 and mid- 2024. However, an increasing trend beyond 40 ppb was observed between June and December 2004. During this 6-month period, the bromide level had a peak value of 51.4 ppb that was approximately two times the average for the remaining time of the Reporting Period. The increase coincided with the water level in San Andreas Reservoir being lowered to accommodate road construction along its perimeter. The reservoir was held at 14 feet below normal for more than four months. The San Andreas Reservoir construction activities ended in November 2024. With the bromide level in the raw water trending downward, the bromate formation in the HTWTP treated water was also reduced.
Table 2. Summary of Bromate Monthly Results in Reporting Period Max (ppb) Average (ppb) Max RAA (ppb) Number of Sample
2022 1.9 1.1 1.3 11
2023 1.7 1.0 1.0 11
2024 5.9 3.4 3.0 11
2. Health Risk Category and Level
Bromate is classified as a probable human carcinogen. Acute symptoms of bromate ingestion include nausea, vomiting, diarrhea, central nervous system depression, tinnitus, deafness, and renal failure. The OEHHA primarily identifies hyperplasia2 as a non-cancer risk associated with bromate in drinking water. Cancer risk associated with lifetime consumption of water at the PHG translates into one per one million excess cancer cases. Cancer risk at the MCL is approximately one per ten thousand excess cancer cases. However, bromate is still permitted in use as a food additive in raw ingredients (such as flour), though it is largely converted to bromide in the baking process.
2 Hyperplasia is an enlargement of an organ or tissue caused by an increase in the amount of cell number. OEHHA concluded this based on male rat data in the DeAngelo et al. (1998) study. 2025 Public Health Goal Report San Francisco Water System 8 3. BAT and Treatment Cost Estimate
Bromate is a disinfection byproduct formed when the source water containing bromide is subject to ozonation treatment, which is currently practiced only at HTWTP. Although it is technically possible to remove bromate after formation using several treatment approaches, such as activated ferrous iron addition, UV irradiation, or membrane and anion exchange resins3, none of these is considered by USEPA or SWRCB as the best available treatment technology. Additionally, these treatment methods were primarily evaluated at bench-scale and pilot levels. Information on full-scale application and associated treatment and O&M costs are rare. Nevertheless, a technical memorandum (Attachment D) has been prepared as part of this report to evaluate some of these treatment methods and provide very rough preliminary cost estimates for information.
The estimate of annualized cost for bromate treatment at HTWTP ranges from $114 to $853 million per year.
This would result in an annual increase in cost at $42 - $312 for each customer served by the SFWS4. In light of the magnitude of cost increases per customer and that bromate concentrations in the treated/drinking water to the SFWS are already below the MCL, any consideration of providing bromate treatment to the PHG level would be impractical. In fact, the USEPA and the SWRCB have both identified that the optimized control of the ozone treatment process is the BAT for reducing bromate formation.
4. SFWS Programs
The SFPUC has continued its bromide monitoring in the raw water supply to HTWTP since 2020. An operational tool was also developed by HTWTP operators with support from the Water Quality Division to help with ozone dosage recommendations during challenging raw water conditions while keeping potential bromate below the regulatory limit. In conjunction with existing watershed protection programs, these efforts taken by the SFPUC are still the most efficient and effective approach to minimize the formation of bromate.
B. Hexavalent Chromium
Chromium is a naturally occurring inorganic element that is used in many industrial processes. For decades, both the USEPA and California have enforced drinking water limits of 100 ppb and 50 ppb, respectively, for total chromium that includes trivalent, hexavalent (Cr-6), and other forms of chromium. OEHHA adopted a PHG of 0.02 ppb for Cr-6 in July 2011. In 2024, the SWRCB adopted a MCL of 10 ppb and a DLR of 0.1 ppb for Cr-6 in June; the new MCL regulation became effective starting on October 1, 2024.
The SFRWS began Cr-6 monitoring at approved surface water sources under the State’s Unregulated Contaminant Monitoring Rule in 2002. In 2013, the SFWS conducted Cr-6 monitoring under USEPA’s Third Unregulated Contaminant Monitoring Rule at designated distribution locations. In early 2018, the SFWS began supplying its own groundwater to Sunset Reservoir and occasionally to Sutro Reservoir. Blending of groundwater with treated surface water Sunset Reservoir has been approved by the SWRCB to reduce the Cr-6 concentration in drinking water to the system. With the advancement of monitoring techniques and analytical instruments, lower values of Cr-6 have been reported since 2014.
3 Bromate Technical Assessment and Cost Estimate for 2025 Public Health Goal Report. Trussell Technologies (April 2025)
4 About 31% of SFRWS water entered SFWS, which served an average of 839,700 customers in the Reporting Period. 2025 Public Health Goal Report San Francisco Water System 9 1. Water Sample Results
The SFPUC continued its Cr-6 monitoring at the raw water sources and treated water supplies. Results of compliance monitoring during the Reporting Period are summarized in Table 3 below. Among the six local wells in the SFWS, only two were used to deliver groundwater intermittently to Sunset Reservoir during the Reporting Period. Compliance samples at the SSR outlets showed that Cr-6 concentrations in the blended water were far below the MCL, albeit the averages were above the PHG. In response to the new SWRCB’s MCL requirements, the SFWS conducted an initial monitoring of the treated surface water at Baden Valve Lot in late 2024. There are four points of entry at Baden. The results showed no detections of Cr-6. However, monitoring at the wholesaler SFRWS confirmed that Cr-6 were not only detected above PHG in the treated water but also in the corresponding raw water sources to the two local treatment plants (Sunol Valley Water Treatment Plant, SVWTP, and HTWTP).
2. Health Risk Category and Level
The OEHHA characterizes Cr-6 as carcinogenic. Most studies of chromium toxicity relate to inhaling airborne Cr-6 in the workplace; however, there is evidence that it is also carcinogenic by the oral route of exposure.
Non-carcinogenic risks have also been associated with inhalation and/or oral ingestion of Cr-6, including reproductive toxicity (developmental, male reproductive, and female reproductive toxicity), liver toxicity (mild chronic inflammation, fatty changes), and toxicity of blood-forming tissues.
The OEHHA calculated health-protective levels based on carcinogenic and non-carcinogenic effects. The health-protective level for carcinogenic effects is one-hundredth of the level based on non-carcinogenic effects; thus, the carcinogenic risk was used to calculate the PHG. The cancer risk associated with lifetime consumption of water at the PHG is one in one million excess cancer cases. Cancer risk at the MCL is five per ten thousand excess cancer cases.
2025 Public Health Goal Report San Francisco Water System 10 Table 3. Cr-6 Level in Compliance Samples for SFWS and Supply Sources5 in Reporting Period Location
Specifics Compliance Location Sample Type Maximum
Level (ppb)
Average
Level (ppb)
No. of
Samples
SFWS University Mound System #3 Treated SW 0.2 0.1 2
POE to SFWS Sunset Reservoir (North) Outlet Blended SW & GW 0.4 0.1 28
POE to SFWS Sunset Reservoir (South) Outlet Blended SW & GW 0.3 0.1 28
SFWS Source SF Lake Merced Well Raw GW 9.8 8.3 7
SFWS Source SF Golden Gate Park – Five
Wells Combined Raw GW 26.9 20 24
POE to SFWS Crystal Springs Pipeline #2 at
Baden Treated SW < 0.1 < 0.1 1
POE to SFWS Sunset Supply Pipeline at Baden Treated SW < 0.1 < 0.1 1 POE to SFWS SAPL #2 at Baden Treated SW < 0.1 < 0.1 1
POE to SFWS SAPL #3 at Baden Treated SW < 0.1 < 0.1 1
POE to SFRWS HTWTP Treated SW 0.3 0.2 4
SFRWS Source San Andreas Reservoir Raw SW 0.2 0.2 4
SFRWS Source Crystal Springs Reservoir Raw SW 0.3 0.2 4 SFRWS Source Pilarcitos Reservoir Raw SW 0.2 0.1 4
POE to SFRWS SVWTP Treated SW 0.3 0.2 3
SFRWS Source San Antonio Reservoir Raw SW 0.2 0.1 4
SFRWS Source Calaveras Reservoir Raw SW 0.4 0.2 4
SFRWS Source Alameda Creek Pond F3 Raw SW 0.1 0.1 3
SFRWS Source Sunol Filter Gallery Raw SW 0.5 0.3 4
POE to SFRWS Alameda East Portal Treated SW 0.2 0.1 4
SFRWS Source Hetch Hetchy Reservoir Raw SW 0.1 < 0.1 4
SFRWS Source Moccasin Reservoir Raw SW < 0.1 < 0.1 4
Note: Cr-6 levels in the above table are rounded results. Not all approved SFRWS sources are included, as some did not supply water during the Reporting Period.
5 SW: Surface Water. GW: Groundwater POE: Point of Entry SAPL: San Andreas Pipeline 2025 Public Health Goal Report San Francisco Water System 11 3. BAT and Treatment Cost Estimate
The SWRCB enlists three BATs for Cr-6 MCL compliance in the 2024 regulations. These include ion exchange, reverse osmosis, and reduction/coagulation/filtration. A technical memorandum (Attachment E) was prepared in support of this report for evaluating these Cr-6 treatment technologies and applicable cost estimates. As Cr-6 was detected above the PHG at several compliance monitoring locations for both SFRWS and SFWS, treatment costs were for the assumed facility locations shown in Table 4 and Table 5 of Attachment E. The primary cost estimates were calculated for the SFWS local groundwater and related sources, whereas the supplementary cost estimates were for the drinking water supplies from the SFRWS.
These preliminary but highly uncertain estimates of annualized capital costs for ion exchange treatment range from $47 million for local groundwater supply only to $3.23 billion for regional surface water supplies. The corresponding annualized operations and maintenance costs range from $33 million to $1.5 billion. This would result in an annual increase in cost ranging from $92 to $1,800 to each customer served by the SFWS.
As the current Cr-6 levels in the drinking water supplied by the SFWS are well below the MCL through blending, it is unnecessary to further treat SFWS water at this time for the following reasons:
• Treatment performance to attain PHG level is speculative and uncertain. • Cr-6 treatment technology is still evolving.
• Limited groundwater use.
• Treatment with current technologies may lead to the increase of other contaminants, such as formaldehyde.
4. SFWS Programs
Instead of pursuing expensive Cr-6 treatment that is questionable in performance and effectiveness, the SFPUC will continue monitoring and protecting water sources, as required by regulations. Additionally, the SFWS currently practices the State-approved blending treatment in SSR to ensure that the Cr-6 concentration from the groundwater after blending is well below the MCL. As Cr-6 has also been detected above the PHG in the raw water supplies to SVWTP and HTWTP, the SFRWS will continue its effective watershed management program and chemical quality control program to reduce the likelihood of this contaminant entering into the surface water supplies. Together with an active Cr-6 monitoring program, these efforts are significantly far more efficient for controlling Cr-6 in the drinking water than constructing expensive treatment facilities with no assurance of PHG attainment.
C. Lead
The PHG for lead is 0.2 ppb, which is below the DLR of 5 ppb. The SWRCB adopted AL of 15 ppb for lead in 1995 and requires that lead concentrations in 90% of water samples collected at customer taps not to exceed the AL. Lead enters drinking water primarily through leaching of lead-containing materials in household plumbing and service lines (Figure 2). These materials include:
• Lead-based solder used to join copper pipes
• Brass and/or chrome-plated brass from faucets
2025 Public Health Goal Report San Francisco Water System 12 • Brass/bronze from water meters, curb valves, and corporation valves • Service lines6 made of lead or galvanized steel (if the galvanized line is or ever was downstream of a lead service line or is currently downstream of a service line of unknown material) Corrosion of these materials in a plumbing system can contribute to lead in household drinking water. Note that CHSC §116875 and the Safe Drinking Water Act of 2014 require that pipes, fittings, fixtures, solder, and flux used in plumbing systems must meet the amended definition of lead-free. However, older lead-containing materials remain in many households.
Figure 2. Potential Contributors to Lead in Tap Water from Household Plumbing (from USEPA) There are other lead sources than drinking water present in the environment. For example, lead-based paint was widely used in home painting before 1977 and is still the major source of lead exposure to children in San Francisco. Via its “Prevent Lead Poisoning in Young Children” program, the San Francisco Department of Public Health (SFDPH) visits homes of children with elevated blood lead levels. These investigations help prevent lead poisoning in young children by investigating potential environmental causes and inspecting for the presence of lead in the home environment. During the Reporting Period, the SFDPH completed a total of 365 environmental investigations related to childhood lead exposure in San Francisco. Currently, the City has
6 Service line or user service line refers to the pipeline connection from home to water main. 2025 Public Health Goal Report San Francisco Water System 13 an active program “Fix Lead SF” that property owners can apply for funding to reduce lead poisoning dangers in homes.7
1. Water Sample Results
Lead was neither detected in the distribution system nor in the raw water supply to the wholesale SFRWS.
The SFPUC conducted triennial LCR monitoring at 50 SFWS customer taps in August 2024 according to the schedule approved by the SWRCB. The 90-percentile value of lead results (4.9 ppb) was even below the DLR of 5 ppb; nevertheless, it is above the PHG of 0.2 ppb. The probable lead source in some of these residences is due to the plumbing materials.
2. Health Risk Category and Level
Lead has multiple toxic effects on the human body. The carcinogenic risks are considered smaller than the risks for chronic toxicity, which includes negative neurobehavioral effects in children, hypertension in adults, and potential to cause kidney disease. The most sensitive risk is the reduction of Intelligence Quotient (IQ) points in children. The PHG was determined from a maximum daily lead intake of 2.86 micrograms per day, which corresponds to a decrease of one IQ point in children.
3. BAT and Treatment Cost Estimate
Neither the USEPA nor the SWRCB enlists BATs for lead treatment in their Lead and Copper Rule. Lead is typically present as a result of corrosion in service lines and/or customer plumbing. A combination of efforts considered equivalent to BAT and conducted by water systems for reducing exposure to lead in drinking water include optimized corrosion control, tap monitoring, lead service line replacement, and proactive consumer education/outreach efforts, along with customer point-of-use filters. In August 2006, the SWRCB approved the SFPUC’s use of pH adjustment as optimal corrosion control treatment. The SFPUC has maintained a minimum pH value of 8.2 throughout the transmission system operated by the SFRWS and the distribution system operated by the SFWS. Because the SFWS continues to meet the AL, as demonstrated through monitoring at customer taps, the SWRCB requires no additional treatment for lead.
Regarding lead service line (LSL) replacement, both regulatory agencies require that water systems implement LSL inventory and replacement efforts starting in late 2024. The current SFWS’s LSL program is established in response to:
• USEPA’s 2021 Lead and Copper Rule Revision (LCRR) on lead service line inventory and SWRCB’s similar requirements to (i) identify the areas where service lines are made of lead, non-lead, unknown materials, and galvanized requiring replacement (GRR)8, and (ii) share the inventory with the public. • USEPA’s 2024 Lead and Copper Rule Improvements (LCRI) on 10-year schedule for replacement of lead service lines under the water system’s control. Among others, the LCRI requires, by November
7 See Fix Lead SF at https://www.sf.gov/fix-lead-sf.
8 A GRR is defined by the USEPA as a galvanized steel service line on the customer side that may be downstream of a previously removed lead service line on the utility side. Such galvanized service lines may have trapped some lead, and, when they are disturbed, can release lead. A Lead-Status Unknown service line means the material of the pipeline cannot be identified or confirmed from inspection through the meter box. Reducing the number of Lead- Status Unknown service line is a priority goal for the SFWS.
2025 Public Health Goal Report San Francisco Water System 14 2027, water systems to (i) prepare a baseline inventory that updates the initial (2024) LSL inventory, (ii) determine the unknown materials and continue updating the inventory, and (iii) replace LSL and GRR including lead connectors within 10 years.
4. SFWS Programs
In conjunction with existing tap monitoring and optimized corrosion control treatment, the SFWS has also implemented the following actions with the goal of reducing lead exposure to San Francisco residents.
Replacement of Lead Components
1980s Removed all known (about 7,000) lead service lines from the utility-side of service meters. 1983 Discontinued “leaded” water main joints in the distribution system. 2003 Began replacing curb stop valves with lead-free units when found. 2008 Began replacing water meters with lead-free, automated units. With replacement more than 99% complete, some large compound meters are yet to be replaced due to challenges in meter accessibility resulting in an estimated replacement cost of about $80 million).
Service line Inventory and Replacement
Service Line on Utility Side of Water Meter
The SFWS had about 7,000 known lead service lines removed in the 1980’s. In 2018, the SFWS completed an inventory of lead user service lines (LUSL)9 in accordance with Senate Bill 427 (2017). A LUSL does not include the meter and the service line on the customer’s side of the meter. However, it may include a galvanized line with a short (2’- 3’ long) lead connector, also known as lead whip, associated with the service line on the water system side. The LUSL inventory reported to the SWRCB had the following findings:
• No lead pipelines were identified.
• 10,912 service lines were made of unknown material.
• 5,218 galvanized steel service lines that may contain lead whips on the water main.
The 2018 LUSL inventory was subsequently refined and updated in 2019 and 2020 10 based on additional
information gathered after 2018.
In June 2020, the SFPUC submitted a 10-year lead component replacement schedule to the SWRCB for the estimated total of 1,578 galvanized steel services lines that may have lead whips. The schedule included field inspections to confirm the unknown material service lines. If a galvanized service line is found or the unknown material cannot be verified, the service line will be scheduled for replacement.
As of the end of the Reporting Period, all 13,140 field inspections needed for material identification were completed. There were 363 galvanized lines out of the 8,848 unknown material service lines, whereas 1,060 of
9 §64551.60 defines LUSL as the pipe, tubing, and fittings connecting a water main to an individual water meter or service connection but does not include the service line from the meter to individual homes. 10 The July 2020 inventory update confirmed 8,848 unknown material service lines and 4,434 galvanized service lines. 2025 Public Health Goal Report San Francisco Water System 15 the 4,292 possible galvanized service lines were truly galvanized. Overall, there were 1,423 galvanized service lines identified. As of May 1, 2025, the SFWS replaced 1,156 (80.4%) of which 226 (19.6%) had lead whips. As part of the replacement program, the SFWS has also created a customer lookup map that is currently posted at sfpuc.gov/Lead. A customer can use the map to identify if an address has a galvanized service line scheduled for replacement. The LUSL will not be replaced until the customer has been given lead health information fact sheets, building flushing instructions, and a water pitcher filter with a 6-month supply of filters. The replacement program is anticipated to be completed by mid-2026, well ahead of the regulatory deadline of 2030.
Service Line on Customer Side o f Water Meter
Starting in 2022, the SFWS began the preparation of an inventory of customer-side service lines in accordance with the USEPA’s LCRR. The initial LSL inventory submitted under LCRR to the SWRCB in October 2024 reported that (i) there are no LSLs, (ii) 653 GRRs and 407 Lead-Status Unknown lines were identified, and (iii) 9,042 inspections were done. A predictive model was initially developed followed by the use of a statistical approach to help determine the probability that lead might be found without inspecting all customer- side service lines. The rigorous statistical method concluded that there is less than 1% probability that a cu
stomer-side service line is made of lead. Additionally, experienced plumbers with 30 years or more of knowledge of the distribution system confirm that they have never encountered customer-side service lines m
ade of lead. In November 2024, notification letters were sent to customers with GRRs and unknown lines offering free lead testing and free inspections to identify the unknown line material. The lookup map initially developed for the utility-side LUSL locations has been expanded to include the customer-side information.
The map and web-based information are routinely updated to show the locations of these service lines.
S
ince the October 2024 inventory submittal, the SFPUC has resurveyed the 407 Lead-Status Unknown lines that had access issues. As of May 1, 2025, there are 675 GRRs and 241 remaining unknown material lines.
The SFPUC intends to inspect all reasonably accessible unknown lines by the end of 2025. Some service lines that may require concrete removal, excavation, and site resolution with other parties may take additional time.
B
etween July 2019 and May 2022, SFPUC staff conducted a pilot study at residences in SFWS where 158 LUSLs were subsequently replaced. Thirty-one of these LUSLs had lead whips. The study was to evaluate the lead levels in tap water after these replacements. A total of 36 participants volunteered for the study, and the results indicated that lead levels in tap samples after LUSL replacement increased slightly and then dropped to levels lower than the AL. Some of these participants still have detectable lead results in their first 1-liter samples, suggesting that the household plumbing is still a contributor to the lead detected in the tap w
ater. These are consistent with industry findings.
In addition to the above lead reduction activities, the SFPUC is working on the following to comply with the USEPA’s 2024 LCRI:
• Identify new Tier 3 sites that have GRRs for future lead and copper monitoring. • Develop a schedule for tap sampling at schools and licensed childcare facilities starting by 2028. • Discussion and evaluation of a potential GRR replacement program per LCRI.
P
ublic Outreach and Education
2025 Public Health Goal Report San Francisco Water System 16 The SFPUC has long taken a proactive approach to educating customers about lead in drinking water, its health effects, and ways to reduce lead exposure in drinking water. Below are highlights of public outreach activities:
1980 Conducted free lead tests of drinking water taps at the San Francisco Unified School District. 1994 Began providing “Lead Test for a Fee” for consumers, testing tap water for a nominal fee. 1996 Began sending customer-focused communications regarding lead issues in bill inserts and annual Water Quality Reports.
Participated in SFDPH Childhood Lead Prevention Program to provide laboratory services and water sampling assistance to help investigate the lead sources for cases of high blood levels in children residing in the City and County of San Francisco. 1998 Began offering free lead tests for Women, Infants & Children Program enrollees. 2000-
2010
Provided lead-free faucets to childcare centers and public schools in San Francisco at no cost and offered significantly discounted lead-free faucets to City residents via annual sales at street fairs.
2017-
2019
Assisted 198 public and private K-12 schools including pre-school facilities on public school properties in sampling and analysis of lead in drinking water. 2022-
2023
2024-
Present
Assisted the San Francisco Unified School District in completing lead sampling at 36 childcare centers located on their school campuses.
Plan for public and private K-12 school sampling and Licensed Childcare Centers starting by 2028.
V. Recommendations for Further Actions
In accordance with the OEHHA literature,11 a PHG is not a boundary line between a “safe” and “dangerous” level of a contaminant. Drinking water is considered acceptable for public consumption, even if it contains contaminants at levels exceeding the PHG, provided the MCLs are met.
The benefits of reducing the naturally occurring contaminants are minimal if their levels are well below their corresponding MCLs. The SFWS will continue monitoring for the bromide level in the influent and optimizing the ozone dose to minimize bromate formation at the HTWTP. Additionally, Cr-6 levels will continue to be maintained well below the MCL through effective blending with other system supplies.
The major sources of lead in tap water are the plumbing fixtures at customer premises, although the presence of GRRs and unknown material service lines may also contribute to the lead level in drinking water. The most
11 OEHAA, Guide to Public Health Goal for Chemicals in Drinking Water, 2022. 2025 Public Health Goal Report San Francisco Water System 17 effective actions that the SFWS can take to reduce customer’s exposure to lead in drinking water are to maintain optimized corrosion control treatment and continue existing lead abatement and public outreach efforts. Identifying and replacing service lines (LUSLs and GRRs) will help ensure that lead is not introduced into drinking water.
In summary, the SFWS will continue existing surveillance and monitoring programs in a proactive manner to control and reduce contaminants in its drinking water supply to customers. 2025 Public Health Goal Report San Francisco Water System Attachmen
t A
Excer
pt from California Health and Safety Code, Section 116470(b)-(f) Attachment A: Excerpt from California Health and Safety Code: Section 116470(b) - (f) for PHG Report
(b) On o
r before July 1, 1998, and every three years thereafter, public water systems serving more than 10,000 service connections that detect one or more contaminants in drinking water that exceed the applicable public health goal, shall prepare a brief written report in plain language that does all of the following:
(1) I
dentifies each contaminant detected in drinking water that exceeds the applicable public health goal.
(2)
Discloses the numerical public health risk, determined by the office, associated with the maximum contaminant level for each contaminant identified in paragraph (1) and the numerical public health risk determined by the office associated with the public health goal for that contaminant. (3)
Identifies the category of risk to public health, including, but not limited to, carcinogenic, mutagenic, teratogenic, and acute toxicity, associated with exposure to the contaminant in drinking water, and includes a brief plainly worded description of these terms.
(4) D
escribes the best available technology, if any is then available on a commercial basis, to remove the contaminant or reduce the concentration of the contaminant.
The public water system may, solely at its own discretion, briefly describe actions that have been taken on its own, or by other entities, to prevent the introduction of the contaminant into drinking water supplies. (5)
Estimates the aggregate cost and the cost per customer of utilizing the technology described in paragraph (4), if any, to reduce the concentration of that contaminant in drinking water to a level at or below the public health goal. (6) B
riefly describes what action, if any, the local water purveyor intends to take to reduce the concentration of the contaminant in public drinking water supplies and the basis for that decision.
(c
) Public water systems required to prepare a report pursuant to subdivision (b) shall hold a public hearing for the purpose of accepting and responding to public comment on the report.
Public water systems may hold the public hearing as part of any regularly scheduled meeting. (d
) The department shall not require a public water system to take any action to reduce or eliminate any exceedance of a public health goal.
(e) En
forcement of this section does not require the department to amend a public water system's operating permit.
(f
) Pending adoption of a public health goal by the Office of Environmental Health Hazard Assessment pursuant to subdivision (c) of Section 116365, and in lieu thereof, public water systems shall use the national maximum contaminant level goal adopted by the United States Environmental Protection Agency for the corresponding contaminant for purposes of complying with the notice and hearing requirements of this section. 2025 Public Health Goal Report San Francisco Water System Attachmen
t B
Health Ris
k Information for Public Health Goal Exceedance Reports DRAFT – FOR REVIEW ONLY
OFFICE OF ENVIRONMENTAL HEALTH HAZARD ASSESSMENT
Public Health Goals
Health Risk Information
for Public Health Goal
Exceedance Reports
February 2025
Pesticide and Environmental Toxicology Branch
Office of Environmental Health Hazard Assessment
California Environmental Protection Agency
Of
fice of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 1
Health Risk Information for
Public Health Goal Exceedance Reports
Prepared by
Of
fice of Environmental Health Hazard Assessment
California Environmental Protection Agency
February 2025
NEW fo
r the 2025 Report: New in this document are newly established Public Health Goals (PHGs) for perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and five haloacetic acids: monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid.
Background: Under the Calderon-Sher Safe Drinking Water Act of 1996 (the Act), public water systems with more than 10,000 service connections are required to prepare a report every three years for contaminants that exceed their respective PHGs.1 This document contains health risk information on drinking water contaminants to assist public water systems in preparing these reports. A PHG is the concentration of a contaminant in drinking water that poses no significant health risk if consumed for a lifetime. PHGs are developed and published by the Office of Environmental Health Hazard Assessment (OEHHA) using current risk assessment principles, practices and methods.2
The water system’s report is required to identify the health risk category (e.g., carcinogenicity or neurotoxicity) associated with exposure to each contaminant in drinking water that has a PHG and to include a brief, plainly worded description of these risks. The report is also required to disclose the numerical public health risk, if available, associated with the California Maximum Contaminant Level (MCL) and with the PHG for each contaminant. This health risk information document is prepared by OEHHA every three years to assist the water systems in providing the required information in their reports.
1 Health and Safety Code Section 116470(b)
2 Health and Safety Code Section 116365
Of
fice of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 2
Numerical health risks: Table 1 presents health risk categories and cancer risk values for chemical contaminants in drinking water that have PHGs.
The Act requires that OEHHA publish PHGs based on health risk assessments using the most current scientific methods. As defined in statute, PHGs for non-carcinogenic chemicals in drinking water are set at a concentration “at which no known or anticipated adverse health effects will occur, with an adequate margin of safety.” For carcinogens, PHGs are set at a concentration that “does not pose any significant risk to health.” PHGs provide one basis for revising MCLs, along with cost and technological feasibility.
OEHHA has been publishing PHGs since 1997 and the entire list published to date is shown in Table 1.
Table 2 presents health risk information for contaminants that do not have PHGs but have state or federal regulatory standards. The Act requires that, for chemical contaminants with California MCLs that do not yet have PHGs, water utilities use the federal Maximum Contaminant Level Goal (MCLG) for the purpose of complying with the requirement of public notification. MCLGs, like PHGs, are strictly health based and include a margin of safety. One difference, however, is that the MCLGs for carcinogens are set at zero because the US Environmental Protection Agency (US EPA) assumes there is no absolutely safe level of exposure to such chemicals. PHGs, on the other hand, are set at a level considered to pose no significant risk of cancer; this is usually no more than a one-in-one-million excess cancer risk (1×10 -6) level for a lifetime of
exposure. In Table 2, the cancer risks shown are based on the US EPA’s evaluations.
For more information on health risks: The adverse health effects for each chemical with a PHG are summarized in a PHG technical support document. These documents are available on the OEHHA website (https://oehha.ca.gov/water/public-health-goals- phgs).
Of
fice of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 3
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Alachlor carcinogenicity
(causes cancer)
0.004 NA5,6 0.002 NA
Aluminum neurotoxicity and
immunotoxicity
(harms the nervous and
immune systems)
0.6 NA 1 NA
Antimony hepatotoxicity
(harms the liver)
0.001 NA 0.006 NA
Arsenic carcinogenicity
(causes cancer)
0.000004
(4×10-6)
1×10-6
(one per
million)
0.01 2.5×10-3
(2.5 per
thousand)
Asbestos carcinogenicity
(causes cancer)
7 MFL7
(fibers >10
microns in
length)
1×10-6 7 MFL
(fibers >10
microns in
length)
1×10-6
(one per
million)
Atrazine carcinogenicity
(causes cancer)
0.00015 1×10-6 0.001 7×10-6
(seven per
million)
Barium cardiovascular toxicity
(causes high blood
pressure)
2 NA 1 NA
1 Based on the OEHHA PHG technical support document unless otherwise specified. The categories are the hazard traits defined by OEHHA for California’s Toxics Information Clearinghouse (online at:
https://oehha.ca.gov/media/downloads/risk-assessment//gcregtext011912.pdf). 2 mg/L = milligrams per liter of water, equivalent to parts per million (ppm) 3 Cancer Risk = Upper bound estimate of excess cancer risk from lifetime exposure. Actual cancer risk may be lower or zero. 1×10-6 means one excess cancer case per million people exposed. 4 MCL = maximum contaminant level.
5 NA = not applicable. Cancer risk cannot be calculated. 6 The PHG for alachlor is based on a threshold model of carcinogenesis and is set at a level that is believed to be without any significant cancer risk to individuals exposed to the chemical over a lifetime. 7 MFL = million fibers per liter of water.
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Water Toxicology Section
February 2025 4
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Bentazon hepatotoxicity and
digestive system toxicity
(harms the liver,
intestine, and causes
body weight effects8)
0.2 NA 0.018 NA
Benzene carcinogenicity
(causes leukemia)
0.00015 1×10-6 0.001 7×10-6
(seven per
million)
Benzo[a]pyrene carcinogenicity
(causes cancer)
0.000007
(7×10-6)
1×10-6 0.0002 3×10-5
(three per
hundred
thousand)
Beryllium digestive system toxicity
(harms the stomach or
intestine)
0.001 NA 0.004 NA
Bromate carcinogenicity
(causes cancer)
0.0001 1×10-6 0.01 1×10-4
(one per
ten
thousand)
Cadmium nephrotoxicity
(harms the kidney)
0.00004 NA 0.005 NA
Carbofuran reproductive toxicity
(harms the testis)
0.0007 NA 0.018 NA
Carbon
tetrachloride
carcinogenicity
(causes cancer)
0.0001 1×10-6 0.0005 5×10-6
(five per
million)
8 Body weight effects are an indicator of general toxicity in animal studies.
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fice of Environmental Health Hazard Assessment
Water Toxicology Section
February 2025 5
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Chlordane carcinogenicity
(causes cancer)
0.00003 1×10-6 0.0001 3×10-6
(three per
million)
Chlorite hematotoxicity
(causes anemia)
neurotoxicity
(causes neurobehavioral
effects)
0.05 NA 1 NA
Chromium,
hexavalent
carcinogenicity
(causes cancer)
0.00002 1×10-6 0.010 5×10-4 (five
per ten
thousand)
Copper digestive system toxicity
(causes nausea,
vomiting, diarrhea)
0.3 NA 1.3 (AL9) NA
Cyanide neurotoxicity
(damages nerves)
endocrine toxicity
(affects the thyroid)
0.15 NA 0.15 NA
Dalapon nephrotoxicity
(harms the kidney)
0.79 NA 0.2 NA
Di(2-ethylhexyl)
adipate (DEHA)
developmental toxicity
(disrupts development)
0.2 NA 0.4 NA
Di(2-ethylhexyl)
phthalate
(DEHP)
carcinogenicity
(causes cancer)
0.012 1×10-6 0.004 3×10-7
(three per
ten million)
9 AL = action level. The action levels for copper and lead refer to a concentration measured at the tap. Much of the copper and lead in drinking water is derived from household plumbing (The Lead and Copper Rule, Title 22, California Code of Regulations [CCR] section 64672.3).
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Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
1,2-Dibromo-3-
chloropropane
(DBCP)
carcinogenicity
(causes cancer)
0.000003
(3x10-6)
1×10-6 0.0002 7×10-5
(seven per
hundred
thousand)
1,2-Dichloro-
benzene
(o-DCB)
hepatotoxicity
(harms the liver)
0.6 NA 0.6 NA
1,4-Dichloro-
benzene
(p-DCB)
carcinogenicity
(causes cancer)
0.006 1×10-6 0.005 8×10-7
(eight per
ten million)
1,1-Dichloro-
ethane
(1,1-DCA)
carcinogenicity
(causes cancer)
0.003 1×10-6 0.005 2×10-6
(two per
million)
1,2-Dichloro-
ethane
(1,2-DCA)
carcinogenicity
(causes cancer)
0.0004 1×10-6 0.0005 1×10-6
(one per
million)
1,1-Dichloro-
ethylene
(1,1-DCE)
hepatotoxicity
(harms the liver)
0.01 NA 0.006 NA
1,2-Dichloro-
ethylene, cis
nephrotoxicity
(harms the kidney)
0.013 NA 0.006 NA
1,2-Dichloro-
ethylene, trans
immunotoxicity
(harms the immune
system)
0.05 NA 0.01 NA
Dichloromethane
(methylene
chloride)
carcinogenicity
(causes cancer)
0.004 1×10-6 0.005 1×10-6
(one per
million)
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Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
2,4-Dichloro-
phenoxyacetic
acid (2,4-D)
hepatotoxicity and
nephrotoxicity
(harms the liver and
kidney)
0.02 NA 0.07 NA
1,2-Dichloro-
propane
(propylene
dichloride)
carcinogenicity
(causes cancer)
0.0005 1×10-6 0.005 1×10-5
(one per
hundred
thousand)
1,3-Dichloro-
propene
(Telone II)
carcinogenicity
(causes cancer)
0.0002 1×10-6 0.0005 2×10-6
(two per
million)
Dinoseb reproductive toxicity
(harms the uterus and
testis)
0.014 NA 0.007 NA
Diquat ocular toxicity
(harms the eye)
developmental toxicity
(causes malformation)
0.006 NA 0.02 NA
Endothall digestive system toxicity
(harms the stomach or
intestine)
0.094 NA 0.1 NA
Endrin neurotoxicity
(causes convulsions)
hepatotoxicity
(harms the liver)
0.0003 NA 0.002 NA
Ethylbenzene
(phenylethane)
hepatotoxicity
(harms the liver)
0.3 NA 0.3 NA
Ethylene
dibromide (1,2-
Dibromoethane)
carcinogenicity
(causes cancer)
0.00001 1×10-6 0.00005 5×10-6
(five per
million)
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Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Fluoride musculoskeletal toxicity
(causes tooth mottling)
1 NA 2 NA
Glyphosate nephrotoxicity
(harms the kidney)
0.9 NA 0.7 NA
Haloacetic acids:
dibromoacetic
acid
carcinogenicity
(causes cancer)
0.00003 1×10-6 0.06* 2×10-3
(two per
thousand)10
Haloacetic acids:
dichloroacetic
acid
carcinogenicity
(causes cancer)
0.0002 1×10-6 0.06* 3×10-4
(three per
ten
thousand)11
Haloacetic acids:
monobromo-
acetic acid
musculoskeletal toxicity
(causes muscular
degeneration)
0.025 NA 0.06* NA
Haloacetic acids:
monochloro-
acetic acid
general toxicity
(causes body and organ
weight changes8)
0.053 NA 0.06* NA
Haloacetic acids:
trichloroacetic
acid
carcinogenicity
(causes cancer)
0.0001 1×10-6 0.06* 6×10-4
(six per ten
thousand)12
Heptachlor carcinogenicity
(causes cancer)
0.000008
(8×10-6)
1×10-6 0.00001 1×10-6
(one per
million)
* For total haloacetic acids (the sum of dibromoacetic acid, dichloroacetic acid, monobromoacetic acid, monochloroacetic acid, and trichloroacetic acid). There are no MCLs for individual haloacetic acids. 10 Based on 0.060 mg/L dibromoacetic acid; the risk will vary with different combinations and ratios of the other haloacetic acids in a particular sample.
11 Based on 0.060 mg/L dichloroacetic acid; the risk will vary with different combinations and ratios of the other haloacetic acids in a particular sample.
12 Based on 0.060 mg/L trichloroacetic acid; the risk will vary with different combinations and ratios of the other haloacetic acids in a particular sample.
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February 2025 9
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Heptachlor
epoxide
carcinogenicity
(causes cancer)
0.000006
(6×10-6)
1×10-6 0.00001 2×10-6
(two per
million)
Hexachloro-
benzene
carcinogenicity
(causes cancer)
0.00003 1×10-6 0.001 3×10-5
(three per
hundred
thousand)
Hexachloro-
cyclopentadiene
(HCCPD)
digestive system toxicity
(causes stomach
lesions)
0.002 NA 0.05 NA
Lead developmental
neurotoxicity
(causes neurobehavioral
effects in children)
cardiovascular toxicity
(causes high blood
pressure)
carcinogenicity
(causes cancer)
0.0002 <1×10-6
(PHG is
not based
on this
effect)
0.015
(AL9)
2×10-6
(two per
million)
Lindane
(γ-BHC)
carcinogenicity
(causes cancer)
0.000032 1×10-6 0.0002 6×10-6
(six per
million)
Mercury
(inorganic)
nephrotoxicity
(harms the kidney)
0.0012 NA 0.002 NA
Methoxychlor endocrine toxicity
(causes hormone
effects)
0.00009 NA 0.03 NA
Methyl tertiary-
butyl ether
(MTBE)
carcinogenicity
(causes cancer)
0.013 1×10-6 0.013 1×10-6
(one per
million)
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February 2025 10
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Molinate carcinogenicity
(causes cancer)
0.001 1×10-6 0.02 2×10-5
(two per
hundred
thousand)
Monochloro-
benzene
(chlorobenzene)
nephrotoxicity
(harms the kidney)
0.07 NA 0.07 NA
Nickel developmental toxicity
(causes increased
neonatal deaths)
0.012 NA 0.1 NA
Nitrate hematotoxicity
(causes
methemoglobinemia)
45 as
nitrate
NA 10 as
nitrogen
(=45 as
nitrate)
NA
Nitrite hematotoxicity
(causes
methemoglobinemia)
3 as
nitrite
NA 1 as
nitrogen
(=3 as
nitrite)
NA
Nitrate and
Nitrite
hematotoxicity
(causes
methemoglobinemia)
10 as
nitrogen13
NA 10 as
nitrogen
NA
N-nitroso-
dimethyl-amine
(NDMA)
carcinogenicity
(causes cancer)
0.000003
(3×10-6)
1×10-6 none NA
Oxamyl general toxicity
(causes body weight
effects)
0.026 NA 0.05 NA
13 The joint nitrate/nitrite PHG of 10 mg/L (10 ppm, expressed as nitrogen) does not replace the individual values, and the maximum contribution from nitrite should not exceed 1 mg/L nitrite-nitrogen.
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February 2025 11
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Pentachloro-
phenol (PCP)
carcinogenicity
(causes cancer)
0.0003 1×10-6 0.001 3×10-6
(three per
million)
Perchlorate endocrine toxicity
(affects the thyroid)
developmental toxicity
(causes neurodevelop-
mental deficits)
0.001 NA 0.006 NA
Perfluorooctane
sulfonic acid
(PFOS)
carcinogenicity
(causes cancer)
1×10-6 1×10-6 NA NA
Perfluoro-
octanoic acid
(PFOA)
carcinogenicity
(causes cancer)
7×10-9 1×10-6 NA NA
Picloram hepatotoxicity
(harms the liver)
0.166 NA 0.5 NA
Polychlorinated
biphenyls
(PCBs)
carcinogenicity
(causes cancer)
0.00009 1×10-6 0.0005 6×10-6
(six per
million)
Radium-226 carcinogenicity
(causes cancer)
0.05 pCi/L 1×10-6 5 pCi/L
(combined
Ra226+228)
1×10-4
(one per
ten
thousand)
Radium-228 carcinogenicity
(causes cancer)
0.019 pCi/L 1×10-6 5 pCi/L
(combined
Ra226+228)
3×10-4
(three per
ten
thousand)
Selenium integumentary toxicity
(causes hair loss and
nail damage)
0.03 NA 0.05 NA
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February 2025 12
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Silvex (2,4,5-TP) hepatotoxicity
(harms the liver)
0.003 NA 0.05 NA
Simazine general toxicity
(causes body weight
effects)
0.004 NA 0.004 NA
Strontium-90 carcinogenicity
(causes cancer)
0.35 pCi/L 1×10-6 8 pCi/L 2×10-5
(two per
hundred
thousand)
Styrene
(vinylbenzene)
carcinogenicity
(causes cancer)
0.0005 1×10-6 0.1 2×10-4
(two per
ten
thousand)
1,1,2,2-
Tetrachloro-
ethane
carcinogenicity
(causes cancer)
0.0001 1×10-6 0.001 1×10-5
(one per
hundred
thousand)
2,3,7,8-Tetra-
chlorodibenzo-p-
dioxin (TCDD, or
dioxin)
carcinogenicity
(causes cancer)
5×10-11 1×10-6 3×10-8 6×10-4
(six per ten
thousand)
Tetrachloro-
ethylene
(perchloro-
ethylene, or
PCE)
carcinogenicity
(causes cancer)
0.00006 1×10-6 0.005 8×10-5
(eight per
hundred
thousand)
Thallium integumentary toxicity
(causes hair loss)
0.0001 NA 0.002 NA
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February 2025 13
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Thiobencarb general toxicity
(causes body weight
effects)
hematotoxicity
(affects red blood cells)
0.042 NA 0.07 NA
Toluene
(methylbenzene)
hepatotoxicity
(harms the liver)
endocrine toxicity
(harms the thymus)
0.15 NA 0.15 NA
Toxaphene carcinogenicity
(causes cancer)
0.00003 1×10-6 0.003 1×10-4
(one per
ten
thousand)
1,2,4-Trichloro-
benzene
endocr
ine toxicity
(harms adrenal glands)
0.005 NA 0.005 NA
1,1,1-Trichloro-
ethane
neurotoxicity
(harms the nervous
system),
reproductive toxicity
(causes fewer offspring)
hepatotoxicity
(harms the liver)
hematotoxicity
(causes blood effects)
1 NA 0.2 NA
1,1,2-Trichloro-
ethane
carcinogenicity
(causes cancer)
0.0003 1x10-6 0.005 2×10-5
(two per
hundred
thousand)
Trichloro-
ethylene (TCE)
carcinogenicity
(causes cancer)
0.0017 1×10-6 0.005 3×10-6
(three per
million)
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Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Trichlorofluoro-
methane
(Freon 11)
accelerated mortality
(increase in early death)
1.3 NA 0.15 NA
1,2,3-Trichloro-
propane
(1,2,3-TCP)
carcinogenicity
(causes cancer)
0.0000007
(7×10-7)
1x10-6 0.000005
(5×10-6)
7×10-6
(seven per
million)
1,1,2-Trichloro-
1,2,2-trifluoro-
ethane
(Freon 113)
hepatotoxicity
(harms the liver)
4 NA 1.2 NA
Trihalomethanes:
Bromodichloro-
methane
carcinogenicity
(causes cancer)
0.00006 1x10-6 0.080# 1.3×10-3
(1.3 per
thousand)14
Trihalomethanes:
Bromoform
carcinogenicity
(causes cancer)
0.0005 1x10-6 0.080# 2×10-4
(two per ten
thousand)15
Trihalomethanes:
Chloroform
carcinogenicity
(causes cancer)
0.0004 1x10-6 0.080# 2×10-4
(two per ten
thousand)16
# For total trihalomethanes (the sum of bromodichloromethane, bromoform, chloroform, and dibromochloromethane). There are no MCLs for individual trihalomethanes. 14 Based on 0.080 mg/L bromodichloromethane; the risk will vary with different combinations and ratios of the other trihalomethanes in a particular sample.
15 Based on 0.080 mg/L bromoform; the risk will vary with different combinations and ratios of the other trihalomethanes in a particular sample.
16 Based on 0.080 mg/L chloroform; the risk will vary with different combinations and ratios of the other trihalomethanes in a particular sample.
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February 2025 15
Table 1: Health Risk Categories and Cancer Risk Values for Chemicals with California Public Health Goals (PHGs)
Chemical Health Risk Category1
California
PHG
(mg/L)2
Cancer
Risk3
at the
PHG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Trihalomethanes:
Dibromochloro-
methane
carcinogenicity
(causes cancer)
0.0001 1x10-6 0.080# 8×10-4
(eight
per ten
thousand)17
Tritium carcinogenicity
(causes cancer)
400 pCi/L 1x10-6 20,000
pCi/L
5×10-5
(five per
hundred
thousand)
Uranium carcinogenicity
(causes cancer)
0.43 pCi/L 1×10-6 20 pCi/L 5×10-5
(five per
hundred
thousand)
Vinyl chloride carcinogenicity
(causes cancer)
0.00005 1×10-6 0.0005 1×10-5
(one per
hundred
thousand)
Xylene neurotoxicity
(affects the senses,
mood, and motor
control)
1.8 (single
isomer or
sum of
isomers)
NA 1.75 (single
isomer or
sum of
isomers)
NA
# For total trihalomethanes (the sum of bromodichloromethane, bromoform, chloroform, and dibromochloromethane). There are no MCLs for individual trihalomethanes. 17 Based on 0.080 mg/L dibromochloromethane; the risk will vary with different combinations and ratios of the other trihalomethanes in a particular sample.
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February 2025 16
Table 2: Health Risk Categories and Cancer Risk Values for Chemicals without California Public Health Goals
Chemical Health Risk Category1
US EPA
MCLG2
(mg/L)
Cancer
Risk3
at the
MCLG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Disinfection byproducts (DBPs)
Chloramines acute toxicity
(causes irritation)
digestive system toxicity
(harms the stomach)
hematotoxicity
(causes anemia)
45,6 NA7 none NA
Chlorine acute toxicity
(causes irritation)
digestive system toxicity
(harms the stomach)
45,6 NA none NA
Chlorine dioxide hematotoxicity
(causes anemia)
neurotoxicity
(harms the nervous
system)
0.85,6 NA none NA
Radionuclides
1 Health risk category based on the US EPA MCLG document or California MCL document unless otherwise specified.
2 MCLG = maximum contaminant level goal established by US EPA. 3 Cancer Risk = Upper estimate of excess cancer risk from lifetime exposure. Actual cancer risk may be lower or zero. 1×10-6 means one excess cancer case per million people exposed. 4 California MCL = maximum contaminant level established by California. 5 Maximum Residual Disinfectant Level Goal, or MRDLG.
6 The federal Maximum Residual Disinfectant Level (MRDL), or highest level of disinfectant allowed in drinking water, is the same value for this chemical. 7 NA = not available.
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February 2025 17
Table 2: Health Risk Categories and Cancer Risk Values for Chemicals without California Public Health Goals
Chemical Health Risk Category1
US EPA
MCLG2
(mg/L)
Cancer
Risk3
at the
MCLG
California
MCL4
(mg/L)
Cancer
Risk at the
California
MCL
Gross alpha
particles8
carcinogenicity
(causes cancer)
0 (210Po
included)
0 15 pCi/L9
(includes
radium but
not radon
and
uranium)
up to 1x10-3
(for 210Po,
the most
potent alpha
emitter)
Beta particles
and photon
emitters8
carcinogenicity
(causes cancer)
0 (210Pb
included)
0 50 pCi/L
(judged
equiv. to 4
mrem/yr)
up to 2x10-3
(for 210Pb,
the most
potent beta-
emitter)
8 MCLs for gross alpha and beta particles are screening standards for a group of radionuclides.
Corresponding PHGs were not developed for gross alpha and beta particles. See the OEHHA memoranda discussing the cancer risks at these MCLs at
http://www.oehha.ca.gov/water/reports/grossab.html.
9 pCi/L = picocuries per liter of water.
2025 Public Health Goal Report San Francisco Water System Attachmen
t C
SFWS
Water Quality Reports - 2022, 2023, 2024
CITY OF SAN FRANCISCO
20 22
20 22
ANNUAL
WATER
QUALITY
REPORT
Here For You 24/7
The San Francisco Public Utilities Commission (SFPUC)
provides 2.7 million customers in cities and towns across the region with high quality water that exceeds all federal and state standards. Through careful stewardship of both our natural resources and our infrastructure, our goal is to reliably deliver high quality drinking water to homes and businesses every day. However, long-term climate change requires all of us to rethink the way we use this precious resource.
Understanding This Report
The SFPUC produces a Water Quality Report every year
in order to provide specific information about where your water comes from, how we treat it, and its overall chemical composition. We do this not only to meet regulatory
requirements but also to provide you with clear and
important information about our drinking water operations and our public health protection efforts.
We are committed to providing high quality drinking water for all our customers. The SFPUC operates and maintains a
water system that deliver potable water for consumption by our customers. In addition to the system of reservoirs within San Francisco, the SFPUC also maintains a wider system of reservoirs and pipelines on the Peninsula, in the South Bay, and upcountry in the Yosemite National Park. It is our hope that this report will not only provide you with greater knowledge of your water, but also an increased confidence in the skills, talents, and efforts of our staff that ensure delivery of high-quality water to every one of our customers.
Our Drinking Water
Sources and Treatment
Almost all of our drinking water supply comes from the San Francisco Regional Water System (SFRWS), which is the
wholesale system owned and operated by the SFPUC. The
supply consists of surface water and groundwater that are well protected and carefully managed. These sources are diverse in both origin and location with the surface water stored in reservoirs located in the Sierra Nevada, Alameda County and San Mateo County, as well as groundwater
stored in a deep aquifer located in the northern part of San Mateo County and the western side of San Francisco.
Maintaining this variety of sources is an important
component of the SFPUC’s near- and long-term water supply management strategy. A diverse mix of sources protects us from potential disruptions due to emergencies or natural disasters, provides resiliency during periods of drought, and helps us ensure a long-term, sustainable water supply as we address issues such as climate uncertainty, regulatory changes, and population growth.
To meet drinking water standards for consumption, all
surface water supplies including the upcountry non-Hetch Hetchy sources undergo treatment by the SFRWS before it is delivered. While the water from Hetch Hetchy Reservoir is exempt from state and federal filtration requirements due to its exceptional quality, it receives the following treatment: disinfection using ultraviolet light and chlorine, pH adjustment for optimum corrosion control, fluoridation for dental health protection, and chloramination for maintaining disinfectant residual and minimizing the formation of
regulated disinfection byproducts. Water from local Bay Area reservoirs in Alameda County and non-Hetch Hetchy
sources is delivered to the Sunol Valley Water Treatment Plant (SVWTP); whereas water from local reservoirs in San Mateo County is delivered to Harry Tracy Water Treatment Plant (HTWTP). Water treatment at these plants consist
of filtration, disinfection, fluoridation, optimum corrosion control, and taste odor removal.
In 2022, we did not use non-Hetch Hetchy sources of water.
However, a small amount of groundwater was added to our surface water supplies through blending in the transmission pipelines and Sunset Reservoir.
Protection of Watersheds
The SFPUC conducts watershed sanitary surveys for the
Hetch Hetchy source annually and for non-Hetch Hetchy
surface water sources every five years. The latest sanitary surveys for the non-Hetch Hetchy watersheds were
completed in 2021 for the period of 2016-2020. All these surveys, together with the SFPUC’s stringent watershed
protection management activities, were completed with
support from partner agencies including National Park
Service and US Forest Service. The purposes of these
annual and quinquennial surveys are to evaluate the sanitary conditions and water quality of the watersheds and to review results of watershed management activities conducted in the preceding years. Wildfire, wildlife, livestock, and human activities continue to be the potential contamination
sources. You may contact the San Francisco District office of the State Water Resources Control Board’s Division of
Drinking Water (SWRCB) at 510-620-3474 for more
information.
Water Quality
We regularly collect and test water samples from reservoirs and designated sampling points throughout the systems to ensure the water delivered to you meets all federal and state drinking water standards. In 2022, we conducted more than 94,230 drinking water tests in the source, transmission, and distribution system. This is in addition to the extensive treatment process control monitoring performed by our
certified operators and online instruments.
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. To ensure that tap water is safe to drink, the United States Environmental Protection Agency (USEPA) and the SWRCB prescribe
regulations that limit the amount of certain contaminants in water provided by public water systems. The U.S. Food and Drug Administration regulations and California law also establish limits for contaminants in bottled water that
pr
ovide the same protection for public health.
Fluoridation and Dental Fluorosis
Mandated by State law, water fluoridation is a widely accepted practice proven safe and effective for preventing and
controlling tooth decay. Our fluoride target level in the water is
0.7 milligram per liter (mg/L, or part per million, ppm), which is consistent with the May 2015 State regulatory guidance on optimal fluoride level. Infants fed formula mixed with water containing fluoride at this level may still have a chance of developing tiny white lines or streaks in their teeth. These marks are referred to as mild to very mild fluorosis and are often only visible under a microscope. Even in cases where the marks are visible, they do not pose any health risk. The Centers of Disease Control (CDC) considers it safe to use optimally fluoridated water for preparing infant formula. To lessen this chance of dental fluorosis, you may choose to use low-fluoride bottled water to prepare infant formula. Nevertheless, children may still develop dental fluorosis due to fluoride intake from other sources such as food, toothpaste, and dental products.
Contact your healthcare provider or the SWRCB if you have concerns about dental fluorosis. For additional information about fluoridation or oral health, visit the State Water Resources Control Board website waterboards.ca.gov/
drinking_water/certlic/drinkingwater/Fluoridation.html , the CDC website cdc.gov/fluoridation, or our website
sfpuc.org/TapWater.
94,230
WATER TESTS
DRINKING
94,230
Potential Contaminants Why We Test For It Likely Source Your Water Source Microbes
Microscopic organisms
such as Coliform bacteria,
Giardia and Cryptosporidium
Can make people
sick after drinking
several glasses.
Naturally present in
the environment or from
animals or human activity
Surpasses State
and Federal
Water Quality
Requirements
Copper and lead
High Levels can cause
health issues over an
extended period of time.
Corrosion of
indoor plumbing
Surpasses State
and Federal
Water Quality
Requirements
Disinfection Byproducts
Byproducts of the process
of disinfecting drinking
water- trihalomethanes
and haloacetic acids
High levels can cause
health issues over an
extended period of time.
Water Disinfection Process
Surpasses State
and Federal
Water Quality
Requirements
Turbidity – cloudiness of
water from suspended
particles in the water
Less turbid
water indicates
high water quality
Soil runoff
Surpasses State
and Federal
Water Quality
Requirements
Fluoride
High levels can cause
marks on teeth over an
extended period of time.
Erosion of natural deposits
and mandated water
additive for dental health
At the optimal CDC
recommended level
PFAS
Synthetic organic chemicals
that are resistant to heat,
water, and oil
Widely used in consumer
and industrial products
No PFAS
detected
Your drinking water comes from rain or melted snow collected in reservoirs in the Sierra Nevada, Alameda and San Mateo Counties, and a small amount of groundwater. 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. Collectively these are called contaminants.
Water Quality Report Card
Special Health Needs
Some people may be more vulnerable to contaminants in
drinking water than the general population. Immuno-
compromised persons, such as those with cancer undergoing chemotherapy, persons who have undergone organ
transplants, people with HIV/AIDS or other immune system disorders, and some elderly people and infants, can be
particularly at risk from infections.
These people should seek advice about drinking water from their healthcare providers. USEPA/CDC guidelines on
appropriate means to lessen the risk of infection by
Cryptosporidium and other microbial contaminants are
available from the USEPA’s Safe Drinking Water Hotline
800-426-4791 or at epa.gov/safewater.
Per-and Polyfluoroalkyl
Substances (PFAS)
PFAS comprise a group of thousands of man-made,
persistent chemicals used in a variety of industries and consumer products. In 2021, we conducted a second
round of voluntary monitoring using a new analytical
method adopted by the USEPA for some other PFAS
contaminants. No PFAS were detected above the SWRCB’s
Consumer Confidence Report Detection Levels in our
surface water and groundwater sources. For additional
information about PFAS, you may visit SWRCB website
waterboards.ca.gov/pfas , SFPUC website sfpuc.org/
TapWater, and/or USEPA website epa.gov/pfas .
Contaminants and Regulations
Generally, the sources of drinking water (both tap water and bottled water) include rivers, lakes, oceans, 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. Such
substances are called contaminants, and may be present in source water as:
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 so
urces such as agriculture, urban stormwater runoff
and r
esidential uses
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 runoff,
agricultural application, and septic systems
Radioactive contaminants , which can be naturally
occurring or be the result of oil and gas production and mining activities
More information about contaminants and potential health effects can be obtained by calling the USEPA’s Safe Drinking Water Hotline 800-426-4791 , or at epa.gov/safewater.
Drinking Water and Lead
Exposure to lead, if present, can cause serious health
effects in all age groups, especially for pregnant women and young children. Infants and children who drink water
containing lead could have decreases in IQ and attention span and increases in learning and behavior problems. The children of women who are exposed to lead before or during pregnancy can have increased risk of these adverse health effects. Adults can have increased risks of heart disease, high blood pressure, kidney or nervous system problems.
Lead in drinking water is primarily from materials and
components associated with service lines and home
plumbing. There are no known lead service lines in our water distribution system. We are responsible for providing high quality drinking water and removing lead pipes, but we
cannot control the variety of materials used in plumbing components in your home. You share the responsibility for protecting yourself and your family from the lead in your home plumbing. You can take responsibility by identifying and removing lead materials within your home plumbing and by taking steps to reduce your family’s risk. When your water has been sitting for several hours, you can minimize the
potential for lead exposure by flushing your pipes for several minutes, such as running your tap, taking a shower, doing laundry or a load of dishes, before using water for drinking and cooking. You can also use a filter certified by an
American National Standards Institute accredited certifier to remove lead from drinking water. If you are concerned about lead in your water you may wish to have your water tested, call 311 or access our website at sfpuc.org/LeadTest to apply for lead testing analysis at a minimal fee. The SFPUC offers low-cost water tests for lead at $25 per tap; clients enrolled in the Women, Infants and Children program may receive free lead test vouchers from our partner agency San Francisco Department of Public Health. Information about lead in drinking water, testing methods, and steps you can take to minimize exposure is available at
epa.
gov/water/lead.
In addition to our water source protection efforts, we
continue the following programs to minimize customer
exposure to lead in water:
•
Replace the remaining brass met
ers with lead-free
automated water meters
• Remov
e/replace LUSL (see below)
• Building flushing Guidance
• Day Care/School Testing
Lead User Service Line (LUSL)
In July 2020, the SFPUC submitted a 10-year lead component replacement schedule to the State Water Resources Control Board and began replacing the estimated 1,578 galvanized steel services lines that may have lead whips. The schedule includes field inspection to confirm the unknown material service lines. If a galvanized service line is found or the unknown material cannot be verified, the service line is scheduled for replacement. The SFPUC created a Lead
Service Line Replacement Program with a customer lookup map, which is posted on SFPUC’s website, sfpuc.org/Lead.
A customer can use the map to identify if the address has an unknown or galvanized service line.
In July 2021, the 10-year lead component replacement
schedule was updated with the number of unknowns and
galvanized services that remained to be inspected. New
changes also reflected that customers in disadvantaged
neighborhood areas would be distributed equitably in the monthly field inspection and replacement schedule. As of February 2023, there are 1,352 galvanized service lines confirmed and 317 field inspections yet to be completed. We also began the preparation of material inventory for customer- side service line: 5,207 field inspection were done, and 406 service lines were determined as galvanized. Between 2019 and 2021, staff conducted a pilot study evaluating the lead levels at residences in San Francisco where Lead User Service Lines were subsequently replaced. A total of 36 participants volunteered for the study, of which the results indicated that lead levels in tap samples after LUSL replacement increased slightly and then dropped to levels lower than the Action Level.
Some of these participants still have noticeable lead results in their first 1-liter samples, suggesting that the household plumbing is still a contributor to the lead detected in the tap water. These are consistent with industry findings. See sfpuc.org/Lead for the San Francisco Water System report on “Impact of Lead Components on Household Lead Levels
at the Tap”, dated March 2022.
Lead and Copper
Tap Sampling Results
We conducted our triennial Lead and Copper Rule (LCR)
monitoring in 2021, when we sample from customer taps
rather than our distribution system, and these sampling results are accessible at sfpuc.org/Lead. The next round of LCR monitoring will be in 2024.
Lead Tests in Childcare
Facilities and Public Schools
Presently we are working with San Francisco Unified School District to help develop a long-term, recurring lead monitoring program for the K-12 schools. We also assisted the school district in completing lead sampling in childcare centers on public school campuses by late 2022.
E. Coli Detections
In late 2022, the system detected E. coli on three separate occasions associated with construction and/or maintenance work. We immediately conducted investigation and
resampling after each incident and confirmation samples showed negative results. These detections were subsequently determined to be caused by unsanitary site conditions, which were then thoroughly flushed and sanitized. The State Water Resources Control Board found no violations of E. coli
Maximum Contaminant Level drinking water standard.
Key Water Quality Terms
The following are definitions of key terms referring to standards and goals of water quality noted on the data
table.
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.
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
USEPA.
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 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.
Primary Drinking Water Standard (PDWS) : MCLs and
MRDLs for contaminants that affect health along with their monitoring and reporting requirements, and water treatment requirements.
Regulatory Action Level : 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.
Turbidity: A water clarity indicator that measures cloudiness of the water and is also used to indicate the effectiveness of the filtration system. High turbidity can hinder the effectiveness of disinfectants.
Cryptosporidium is a parasitic microbe found in most
surface water. We regularly test for this waterborne
pathogen and found it at very low levels in source water and treated water in 2022. However, current test methods approved by the USEPA do not distinguish between dead
organisms and those capable of causing disease. Ingestion of Cryptosporidium may produce symptoms of nausea,
abdominal cramps, diarrhea, and associated headaches.
Cryptosporidium must be ingested to cause disease, and it may be spread through means other than drinking water.
San Francisco Water System - Water Quality Data for 2022 This report is a snapshot of last year’s water quality. The tables below list detected contaminants in our drinking water in 2022 and the information about their typical sources. Contaminants below detection limits for reporting are not shown, in accord with regulatory guidance. The SFRWS holds a SWRCB monitoring waiver for some contaminants in the surface water supply and therefore their monitoring frequencies are less than annual. Visit sfpuc.org/WaterQuality for a list of all water quality parameters we monitored in raw water and treated water in 2022.
DETECTED CONTAMINANTS UNIT MCL/TT PHG
OR (MCLG)
RANGE OR
LEVEL FOUND
AVERAGE
OR [MAX] TYPICAL SOURCES IN DRINKING WATER
TURBIDITY
Unfiltered Hetch Hetchy Water NTU 5 N/A 0.2 - 0.4 (1) [3.4] Soil runoff Filtered Water from Sunol Valley
Water Treatment Plant (SVWTP)
NTU
-
1 (2)
Min 95% of
samples
≤0.3 NTU (2)
N/A
N/A
-
99.3% - 100%
[2.2]
-
Soil runoff
Soil runoff
Filtered Water from Harry Tracy
Water Treatment Plant (HTWTP)
NTU
-
1 (2)
Min 95% of
samples
≤0.3 NTU (2)
N/A
N/A
-
100%
[0.1]
-
Soil runoff
Soil runoff
DISINFECTION BY-PRODUCTS AND PRECURSOR
Total Trihalomethanes ppb 80 N/A 11 - 54 [36]
(3) By-product of drinking water disinfection
Five Haloacetic Acids ppb 60 N/A 6.7 - 47 [28] (3) By-product of drinking water disinfection Bromate ppb 10 0.1 ND - 1.7 [1.3] (4) By-product of drinking water disinfection Total Organic Carbon (5) ppm TT N/A 1.3 - 3.9 2.3 Various natural and man-made sources
MICROBIOLOGICAL
Fecal coliform and E. coli
(6) - 0 Positive Sample (0) - [0] Human or animal fecal waste Giardia lamblia cyst/L TT (0) 0 - 0.04 0.01 Naturally present in the environment
INORGANICS
Fluoride (source water)
(7) ppm 2.0 1 ND - 0.8 0.3 (8) Erosion of natural deposits; water additive to promote strong teeth Chloramine (as chlorine) ppm MRDL = 4.0 MRDLG = 4 <0.1 - 3.5 [2.7] (4) Drinking water disinfectant added for treatment
CONSTITUENTS WITH
SECONDARY STANDARDS UNIT SMCL PHG RANGE AVERAGE TYPICAL SOURCES IN DRINKING WATER Chloride ppm 500 N/A <3 - 15 8.7 Runoff / leaching from natural deposits Color Unit 15 N/A <5 - 5 <5 Naturally-occurring organic materials Iron ppb 300 N/A <6 - 24 11 Leaching from natural deposits Manganese ppb 50 N/A <2 - 2.4 <2 Leaching from natural deposits Specific Conductance µS/cm 1600 N/A 37 - 210 140 Substances that form ions when in water Sulfate ppm 500 N/A 1.1 - 29 15 Runoff / leaching from natural deposits Total Dissolved Solids ppm 1000 N/A <20 - 104 61 Runoff / leaching from natural deposits Turbidity NTU 5 N/A 0.1 - 0.2 0.1 Soil runoff
LEAD AND COPPER (9) UNIT AL PHG RANGE 90TH
PERCENTILE TYPICAL SOURCES IN DRINKING WATER
Copper ppb 1300 300 ND - 383 60 Internal corrosion of household water plumbing systems Lead ppb 15 0.2 ND - 190 7.1 Internal corrosion of household water plumbing systems
NON-REGULATED WATER
QUALITY PARAMETERS
UNIT ORL RANGE AVERAGE KEY
Alkalinity (as CaCO3) ppm N/A 7.1 - 166 41 < / ≤ = less than / less than or equal to AL = Action Level
Max = Maximum
Min = Minimum
N/A = Not Available
ND = Non-Detect
NL = Notification Level
NoP = Number of Coliform-Positive Sample
NTU = Nephelometric Turbidity Unit
ORL = Other Regulatory Level
ppb = part per billion
ppm = part per million
µS/cm = microSiemens/centimeter
Boron ppb 1000 (NL) 28 - 105 56
Calcium (as Ca) ppm N/A 3.2 - 15 9.3
Chlorate ppb 800 (NL) 45 - 650 147
Chromium (VI) ppb N/A 0.22 - 0.27 0.25
Hardness (as CaCO3) ppm N/A 9.1 - 49 32
Magnesium ppm N/A 0.2 - 4.2 2.9
pH - N/A 7.8 - 9.6 9.2
Potassium ppm N/A 0.3 - 1 0.7
Silica ppm N/A 5 - 5.9 5.5
Sodium ppm N/A 3.5 - 21 14
Strontium ppb N/A 16 - 159 79
San Francisco Local Groundwater - Water Quality Data for Year 2022 FOOTNOTES ON SAN FRANCISCO WATER SYSTEM - WATER QUALITY DATA:
(1) These are monthly average turbidity values measured every 4 hours daily. (2) This is a TT requirement for filtration systems. (3) This is the highest locational running annual average value. (4) This is the highest running annual average value. (5) Total organic carbon is a precursor for disinfection byproduct formation.
The TT requirement applies to the filtered water from the SVWTP only. (6) The MCL was changed to E. coli based starting on July 1, 2021 after the SWRCB adopted the Revised Total Coliform Rule. (7) The SWRCB recommended an optimal fluoride level of 0.7 ppm be maintained in the treated water. In 2022, the range and average of the fluoride levels were 0.5 ppm - 0.9 ppm and 0.7 ppm, respectively. (8) Natural fluoride in the Hetch Hetchy source was ND. Elevated fluoride levels in the raw water at the SVWTP and HTWTP were attributed to the transfer of fluoridated Hetch Hetchy water into the local reservoirs. (9) The most recent Lead and Copper Rule monitoring was in August 2021. Three of the 72 site samples collected at consumer taps had lead concentrations above the AL.
Note: The different water sources blended at different ratios throughout the year have resulted in varying water quality. Additional water quality data may be obtained by calling our Water Quality Division toll-free number at 877-737-8297.
Treated Water
(Sunset
Reservoir)
DETECTED CONTAMINANTS UNIT MCL
PHG
OR
(MCLG)
RANGE AVERAGE TYPICAL SOURCES IN DRINKING WATER
INORGANICS
Chromium (VI) ppb N/A 0.02 0.02 - 0.31 0.12 Leaching from natural deposits; waste discharges from electroplating
Fluoride ppm 2.0
(Natural-Source)
1 0.6 - 0.8 0.7 Erosion of natural deposits; water additive to promote strong teeth
CONSTITUENTS WITH
SECONDARY STANDARDS UNIT SMCL PHG
RANGE
OR LEVEL
FOUND
AVERAGE TYPICAL SOURCES IN DRINKING WATER
Chloride ppm 500 N/A 5.2 - 14 8.6 Runoff / leaching from natural deposits Iron ppb 300 N/A 13 13 Leaching from natural deposits
Specific Conductance µS/cm 1600 N/A 73 - 176 106 Substances that form ions when in water Sulfate ppm 500 N/A 5.7 5.7 Runoff / leaching from natural deposits Total Dissolved Solids ppm 1000 N/A 48 48 Runoff / leaching from natural deposits Turbidity NTU 5 N/A 0.1 - 0.3 0.2 Soil runoff
Raw Water
(San Francisco
Local
Groundwater
Wells)
DETECTED CONTAMINANTS UNIT MCL
PHG
OR
(MCLG)
RANGE AVERAGE TYPICAL SOURCES IN DRINKING WATER
INORGANICS (1)
Chromium (VI) ppb N/A 0.02 8.4 - 27 17 Leaching from natural deposits; waste discharges from electroplating
Chromium ppb 50 (100) ND - 21 11 Erosion of natural deposits; discharge from electroplating
Nitrate (as nitrogen) ppm 10 10 3.2 - 8 6.2 Landscape fertilizers and leaked wastewater
VOLATILE ORGANICS
Carbon tetrachloride (2) ppb 0.5 0.1 ND - 0.9 ND Discharge from chemical plants and other industrial activities
Tetrachloroethylene
(3) ppb 5 0.06 2.1 - 2.3 2.2 Discharge from factories, dry cleaners, and auto shops (metal degreaser)
NON-REGULATED WATER
QUALITY PARAMETERS UNIT ORL
RANGE AVERAGE
pH - N/A 6.9 - 8.1 7.8
Strontium ppb N/A 144 - 186 165
FOOTNOTES ON SAN FRANCISCO LOCAL GROUNDWATER - WATER QUALITY DATA:
(1) T
hese contaminants are detectable in the raw groundwater. Blending of groundwater with surface water has been approved by SWRCB as treatment for these contaminants. In 2022, only two of the six local wells (Lake Merced Well and West Sunset Well) delivered groundwater to the distribution system intermittently. (2) This contaminant was detected at South Sunset Well and West Sunset Well but not in the blend water at Sunset Reservoir. South Sunset Well was not in operation in 2022. (3) Tetrachloroethylene was detected at Golden Gate Central Well, which supplied to Golden Gate Park throughout 2022 for irrigation only.
P.O. Box 7369
San Francisco, CA 94120-7369
Follow Us @MySFPUC
San Francisco Public Utilities Commission
Every day we deliver high-quality drinking water to 2.7 million people in San Francisco, Alameda, Santa Clara and San Mateo counties. We generate clean, reliable hydroelectricity that powers 100% of San Francisco’s vital services, including police and fire stations, street lights, Muni, SF General Hospital and more.
Water quality policies are decided at SFPUC Commission hearings, held the 2nd and 4th Tuesdays of each month at 1:30 pm in San Francisco City Hall, Room 400.
This report contains important information about your drinking water. Translate it, or speak with someone who understands it.
Este informe contiene información muy importante sobre su agua potable. Tradúzcalo o hable con alguien que lo entienda bien.
Mahalaga ang impormasyong ito. Mangyaring ipasalin ito.
Cé rapport contient des information importantes concernant votre eau potable. Veuillez traduire, ou parlez avec quelqu’ un qui peut le comprendre.
Этот отчет содержит важную информацию о вашей питьевой воды. Переведите его или поговорите с тем, кто это понимает.
此份水質報告， 內有重要資訊。 請找他人為你翻譯和解說清楚。
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。 翻訳を御依頼なされ
るか、 内容をご理解なさっておられる方にお尋ね下さい。
This report contains important information about our drinking water.
Please contact SFPUC Communications at 628-215-0940 or email [email protected] for assistance.
Este informe contiene información muy importante sobre su agua potable. Favor de comunicarse con JP Streeter en tel 628-215-0940 o [email protected] para asistencia.
此份水質報告，內有重要資訊。請找他人為你翻譯和解說清楚。
Newsha K. Ajami, PRESIDENT
Sophie Maxwell, VICE PRESIDENT
Tim Paulson, COMMISSIONER
Anthony River, COMMISSIONER
Kate H. Stacy, COMMISSIONER
Annual Water Quality Report
2023
CITY OF SAN FRANCISCO
2023
Introduction 1
2023 Annual Water Quality Report1
The San Francisco Public Utilities Commission provides
high-quality water that meets all federal and state
standards to 2.7 million residents and thousands of
businesses in cities and towns across the region.
Through careful stewardship of both our natural
resources and our infrastructure, our goal is to reliably deliver high-quality drinking water to homes and
businesses every day. Although the 2022-2023 water
year proved to be a wet one for California, long-term
climate change will continue to make the state’s
weather more extreme and unpredictable. This will
require all of us to rethink the way we use water and
the sources of supply available to us.
Understanding This Report
The San Francisco Public Utilities Commission produces
a Water Quality Report every year to provide specific
information about where your water comes from, how we
treat it, and its overall quality. We do this not only to meet a regulatory requirement but also provide an educational opportunity for you to understand our drinking water
operations and public health protection efforts.
We are committed to providing high-quality drinking
water for all our customers. Our system is large and we work across several counties to maintain the system
that delivers drinking water for your consumption. It is our hope that this report will not only provide you with greater knowledge of your water, but also an increased
understanding of the considerable skill, talent, and effort of the San Francisco Public Utilities Commission staff
that goes into ensuring businesses and residents have
reliable access to this precious resource.
We’re proud of our water, and we hope you are too. We
hope you enjoy getting to know a little more about who we are as an agency and how you can get involved.
Summary of Water Quality Report
The San Francisco Public Utilities Commission (SFPUC) is a public agency. We run a regional water system. This system delivers drinking water to over 2.7 million residents and thousands of businesses in the Bay Area. Every year we produce Water Quality Reports for customers both in San Francisco and outside of San Francisco. In this report, you can learn where your water comes from, how we treat it, and its overall quality. Our pledge is to provide high quality drinking water to all our customers. In 2023, our water met all federal and state standards.
Annual Water
Quality Report
CITY OF SAN FRANCISCO
Table of Contents:
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 Our Drinking Water Sources and Treatment . . 2
3 Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4 Special Health Needs . . . . . . . . . . . . . . . . . . . . . . 4 5 Contaminants and Regulations. . . . . . . . . . . . . . 5 6 Drinking Water and Lead. . . . . . . . . . . . . . . . . . . 7 7 Key Water Quality Terms . . . . . . . . . . . . . . . . . . . 8 2023 Annual Water Quality Report
2 Our Drinking Water Sources
and Treatment2
Almost all of our drinking water supply comes from
the San Francisco Regional Water System, which is
the wholesale system owned and operated by the
San Francisco Public Utilities Commission. The supply
consists of surface water and groundwater that are
well protected and carefully managed. These sources
are diverse in both origin and location with the surface water stored in reservoirs located in the Sierra Nevada mountains, Alameda County, and San Mateo County, as
well as groundwater stored in a deep aquifer located in the northern part of San Mateo County and the western
side of San Francisco. Maintaining this variety of sources is an important component of the San Francisco Public
Utilities Commission’s near- and long-term water supply management strategy. A diverse mix of sources protects
us from potential disruptions due to emergencies or
natural disasters, provides resiliency during periods of drought, and helps us ensure a long-term, sustainable
water supply as we address issues such as climate
uncertainty, regulatory changes, and population growth.
To meet drinking water standards for consumption,
all surface water supplies including the upcountry
non-Hetch Hetchy sources undergo treatment by the San
Francisco Regional Water System before it is delivered.
While the water from Hetch Hetchy Reservoir is exempt
from state and federal filtration requirements due to its exceptional quality, it receives the following treatment:
disinfection using ultraviolet light and chlorine, pH
adjustment for optimum corrosion control, fluoridation
for dental health protection, and chloramination for
maintaining disinfectant residual and minimizing the
formation of regulated disinfection byproducts. Water
from local Bay Area reservoirs in Alameda County and
non-Hetch Hetchy sources is delivered to the Sunol
Valley Water Treatment Plant; whereas water from local
reservoirs in San Mateo County is delivered to the Harry Tracy Water Treatment Plant. Water treatment at these
plants consists of filtration, disinfection, fluoridation, optimum corrosion control, and taste and odor removal.
In 2023, we did not use upcountry non-Hetch Hetchy
sources of water, and only a very small amount of local groundwater was added to the supply through blending
in the transmission pipelines and Sunset Reservoir.
Summary: Water Sources
Surface water from reservoirs makes up almost all of the water you receive.
In 2023, we also used a very small amount of groundwater. Using a mix of sources protects us from supply interruptions in the future. These interruptions can be due to drought, climate change, or population growth.
We tr
eat all drinking water before delivering it to you. We use proven science to make sure it meets all federal and state standards. In 2023, we performed nearly 100,000 drinking water tests. Samples came from reservoirs and other points in the water system.
2 2023 Annual Water Quality Report
3 We regularly collect and test water samples from
reservoirs and designated sampling points throughout
the system to ensure the water delivered to you meets
all federal and state drinking water standards. In 2023, we conducted nearly 100,000 drinking water tests in
the source, transmission, and distribution system. This is in addition to the extensive treatment process control monitoring performed by our certified operators and
online instruments.
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. Collectively these are called contaminants.
Therefore, 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. To ensure that tap water is safe to drink, the United States Environmental Protection Agency and the State
Water Resources Control Board prescribe regulations
that limit the amount of certain contaminants in water
provided by public water systems. The United States Food and Drug Administration regulations and California law
also establish limits for contaminants in bottled water that provide the same protection for public health.
Protection of Watersheds
The San Francisco Public Utilities Commission conducts
watershed sanitary surveys for the Hetch Hetchy source
annually and for non-Hetch Hetchy surface water sources every five years. The latest sanitary surveys for the non- Hetch Hetchy watersheds were completed in 2021 for
the period of 2016-2020. All these surveys, together with the San Francisco Public Utilities Commission’s stringent watershed protection management activities, were
completed with support from partner agencies including
the National Park Service and the United States Forest
Service. The purposes of these annual and quinquennial
surveys are to evaluate the sanitary conditions and
water quality of the watersheds and to review the results of watershed management activities conducted in the
preceding years. Wildfire, wildlife, livestock, and human activities continue to be the potential contamination
sources. You may contact the San Francisco District office of the State Water Resources Control Board’s Division of Drinking Water at 510-620-3474 for more information.
Fluoridation and Dental Fluorosis
Mandated by State law, water fluoridation is a widely
accepted practice proven safe and effective for
preventing and controlling tooth decay. The San Francisco Public Utilities Commission’s target fluoride level in the water is 0.7 milligram per liter (mg/L, or part per million, ppm), which is consistent with the May 2015 State
regulatory guidance on optimal fluoride levels. Infants fed formula mixed with water containing fluoride at this level may still have a chance of developing tiny white
lines or streaks in their teeth. These marks are referred to as mild to very mild fluorosis and are often only visible under a microscope. Even in cases where the marks are
visible, they do not pose any health risk. The Centers
for Disease Control and Prevention considers it safe
to use optimally fluoridated water for preparing infant formula. To lessen this chance of dental fluorosis, you may choose to use low-fluoride bottled water to prepare infant formula. Nevertheless, children may still develop dental fluorosis due to fluoride intake from other sources such as food, toothpaste, and dental products. Contact
your healthcare provider or the State Water Resources
Control Board if you have concerns about dental
fluorosis. For additional information about fluoridation or oral health, visit the State Water Resources Control Board website’s waterboards.ca.gov/drinking_water/
certlic/drinkingwater/Fluoridation.html, the Centers
for Disease Control and Prevention’s website cdc.gov/
fluoridation, or our website sfpuc.org/TapWater.
Summary: Fluoridation
We add fluoride to our water. California law mandates fluoridation. It is proven safe. It is also effective at preventing and controlling tooth decay. Our fluoride levels match the state’s optimal level. To learn more, visit waterboards.ca.gov/drinking_water/certlic/drinkingwater/Fluoridation.html, cdc.gov/fluoridation, or sfpuc.org/TapWater.
Water Quality3
2023 Annual Water Quality Report
4 4
Summary: Special
Health Needs
We measure contaminants in our water
supply. Drinking water will likely have small
amounts of some contaminants. This does
not mean that the water is unsafe. Bottled
water also likely has some contaminants.
Federal and state governments closely
regulate drinking water. They limit how much
of certain contaminants can exist in public
water. This year, our water met all federal
and state standards.
Some people may need to be more careful
of contaminants. This includes:
•
Immun
ocompromised people
• Peo
ple who have had an organ transplant(s)
• Peo
ple with Human Immunodeficiency
Virus/Acquired Immunodeficiency Syndrome
or other immune system disorders
•
Som
e elderly people and infants
These people should seek advice from their
healthcare providers. To learn more, visit
epa.gov/safewater. Or call 800-426-4791.
Some people may be more vulnerable to contaminants
in drinking water than the general population.
Immunocompromised persons, such as those with
cancer undergoing chemotherapy, persons who have
undergone organ transplants, people with Human
Immunodeficiency Virus/Acquired Immunodeficiency
Syndrome or other immune system disorders, and some
elderly people and infants can be particularly at risk
from infections. These people should seek advice about
drinking water from their healthcare providers.
Cryptosporidium is a parasitic microbe found in most
surface water. We regularly test for this waterborne
pathogen and found it at very low levels in source water and treated water in 2023. However, current test methods approved by the United States Environmental Protection
Agency do not distinguish between dead organisms
and those capable of causing disease. Ingestion of
Cryptosporidium may produce symptoms of nausea,
abdominal cramps, diarrhea, and associated headaches.
Cryptosporidium must be ingested to cause disease, and
it may be spread through means other than drinking water.
The United States Environmental Protection Agency
and the Centers for Disease Control and Prevention
guidelines on appropriate means to lessen the risk
of infection by Cryptosporidium and other microbial
contaminants are available from the United States
Environmental Protection Agency’s Safe Drinking Water
Hotline at 800-426-4791 or at epa.gov/safewater.
Special Health Needs4
2023 Annual Water Quality Report
5 Generally, the sources of drinking water (both tap water and bottled water) include rivers, lakes, oceans, streams, ponds, reservoirs, springs, and wells. Water from these sources may pick up contaminants in the following forms:
• 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 by-products of
industrial processes and petroleum production, and
can also come from gas stations, urban stormwater
runoff, agricultural application, and septic systems
• Radioactive contaminants, which can be naturally
occurring or be the result of oil and gas production
and mining activities
More information about contaminants and potential
health effects can be obtained by calling the United
States Environmental Protection Agency’s Safe Drinking
Water Hotline at 800-426-4791, or at epa.gov/safewater.
Unregulated Contaminant Monitoring Rule
The Safe Drinking Water Act requires the United States
Environmental Protection Agency issue every five years a list of unregulated contaminants to be monitored by
public water systems. The fifth Unregulated Contaminant Monitoring Rule, published on December 21, 2021,
requires sample collection for 30 chemical contaminants between 2023 and 2025. The monitoring results are
expected to provide scientifically valid data on the
national occurrence of these contaminants in drinking
water to assist the agency in future policy development and rulemaking for establishing the appropriate drinking water standards. The fifth Unregulated Contaminant
Monitoring Rule includes 29 per- and poly-fluoroalkyl
substances (PFAS) and lithium. PFAS comprise a group
of thousands of man-made, persistent chemicals used
in a variety of industries and consumer products. We
conducted four consecutive quarters of monitoring at
designated locations approved by the United States
Environmental Protection Agency in 2023, and all results have been non-detect. Together with the two previous
rounds of voluntary PFAS monitoring, we are proud to
report that our water supplies are not compromised by
these contaminants. For additional information about
PFAS, you may visit State Water Resources Control
Board’s website waterboards.ca.gov/pfas, San Francisco
Public Utilities Commission’s website sfpuc.org/TapWater, and/or United States Environmental Protection Agency’s
website epa.gov/pfas.
5 Summary: No PFAS Detected
You may have heard about PFAS. These are man-made chemicals that have been used in industry and consumer products worldwide since the 1940s. We did not detect PFAS in our water. To learn more, visit waterboards.ca.gov/pfas, sfpuc.org/TapWater, and/ or epa.gov/pfas.
Contaminants and Regulations5
2023 Annual Water Quality Report
6 Water Quality Report Card
This Water Quality Report card shows the state of your water. This year, our water met all federal and state standards.
Potential Contaminants Why We Test For It Likely Source Your Water Source Microbes
Microscopic organisms
such as Coliform
bacteria, Giardia
and Cryptosporidium
Can make people
sick after drinking
several glasses.
Naturally present in
the environment or
from animals or
human activity
Surpasses State
and Federal
Water Quality
Requirements
Copper and Lead
High levels can cause
health issues over an
extended period of time.
Corrosion of
indoor plumbing
Surpasses State
and Federal
Water Quality
Requirements
Disinfection Byproducts
Byproducts of the process
of disinfecting drinking
water- trihalomethanes
and haloacetic acids
High levels can
cause health issues
over an extended
period of time.
Water disinfection
process
Surpasses State
and Federal
Water Quality
Requirements
Turbidity – cloudiness of
water from suspended
particles in the water
Less turbid
water indicates
high water quality
Soil runoff
Surpasses State
and Federal
Water Quality
Requirements
Fluoride
High levels can
cause marks on teeth
over an extended
period of time.
Erosion of natural
deposits and mandated
water additive for
dental health
At the
optimal CDC
recommended
level
PFAS
Synthetic organic
chemicals that are
resistant to heat,
water, and oil
Widely used in
consumer and
industrial products
No PFAS
detected
2023 Annual Water Quality Report
7 Exposure to lead, if present, can cause serious health effects in all age groups, especially for pregnant women and young children. Infants and children who drink water containing lead could have decreases in intelligent
quotient and attention span as well as increases in
learning and behavior problems. The children of women
who are exposed to lead before or during pregnancy can
have an increased risk of these adverse health effects.
Adults can have increased risks of heart disease, high
blood pressure, kidney, or nervous system problems.
Lead in drinking water is primarily from materials and
components associated with service lines and home
plumbing. We are responsible for providing high-quality drinking water and removing lead pipes, but we cannot
control the variety of materials used in plumbing
components in your home. You share the responsibility for protecting yourself and your family from the lead in your home plumbing. You can take responsibility by identifying and removing lead materials within your home plumbing
and by taking steps to reduce your family’s risk. When
your water has been sitting for several hours, you can
minimize the potential for lead exposure by flushing your pipes for several minutes, such as running your tap,
taking a shower, or doing laundry or a load of dishes
before using water for drinking and cooking. If you flush the tap, you may wish to collect the flushed water and
reuse it for another beneficial purpose, such as watering plants. You can also use a filter certified by an American National Standards Institute accredited certifier to
remove lead from drinking water.
If you are concerned about lead in your water, you may
wish to have your water tested. We offer low-cost water tests for lead at $25 per tap. Call 311 or access our
website sfpuc.org/LeadTest for details. Clients enrolled in the Women, Infants and Children program may receive
free lead test vouchers from our partner agency the San Francisco Department of Public Health.
In addition to our water source protection efforts and
low-cost lead tests, we continue the following programs to minimize customer exposure to lead in water:
• Replace remaining brass meters with lead-free
automated water meters
• Remove/replace lead pipelines (see below)
• Building flushing guidance
• Day Care/School Testing
Information about lead in drinking water, testing methods, and steps you can take to minimize exposure is available at epa.gov/lead.
Lead User Service Line
In July 2020, we submitted a 10-year lead component
replacement schedule to the State Water Resources
Control Board and began replacing the estimated 1,578
galvanized steel services lines that may have lead whips in the distribution system. The schedule includes field inspections to confirm the unknown material service
lines. If a galvanized service line is found or the unknown material cannot be verified, the service line is scheduled for replacement. In conjunction with the development of the replacement program, we also deployed a customer
lookup map, which is posted on the San Francisco Public Utilities Commission’s website, sfpuc.org/Lead. A
customer can use the map to identify if an address has
an unknown or galvanized service line. In July 2021, the 10-year lead component replacement schedule was
updated with the number of unknown and galvanized
services that remain to be inspected. New changes also
reflected that customers in disadvantaged neighborhood
areas are equitably included in the monthly field
inspection and replacement schedule. As of April 2024,
there are 1,457 galvanized service lines confirmed and
10 field inspections yet to be completed.
We also began the preparation of material inventory for customer-side service lines: approximately 7,100 field
inspections were done between 2020 and 2023, and
about 10% of these service lines were determined as
galvanized. Between 2019 and 2021, staff conducted
a pilot study evaluating the lead levels at residences
in San Francisco where lead user service lines were
subsequently replaced. A total of 36 participants
volunteered for the study, of which the results indicated that lead levels in tap samples one week after lead user service line replacement increased and then dropped to
levels lower than the Action Level.
Some of these participants still have noticeable lead
results in their first one-liter samples, suggesting that the household plumbing may still contribute to the lead detected in the tap water. These are consistent with water utility results from across the county. See sfpuc.org/Lead for our report on “Impact of Lead Components on
Household Lead Levels at the Tap,” dated March 2022.
Drinking Water and Lead6
2023 Annual Water Quality Report
8 The following are definitions of key terms referring
to standards and goals of water quality noted on the
data table.
• 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.
• 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 United States Environmental Protection Agency.
• 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 Residual Disinfectant Level (MRDL):
The highest level of a disinfectant allowed in
drinking water. There is convincing evidence
that the 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.
• Primary Drinking Water Standard (PDWS): MCLs
and MRDLs for contaminants that affect health along
with their monitoring and reporting requirements, and
water treatment requirements.
• Regulatory Action Level: 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.
• Turbidity: A water clarity indicator that measures the cloudiness of the water and is also used to indicate
the effectiveness of the filtration system. High turbidity can hinder the effectiveness of disinfectants.
Lead and Copper Tap Sampling Results
We conducted our triennial Lead and Copper Rule
monitoring at 72 representative customer tap sites
in 2021. These sampling results are accessible at
sfpuc.org/Lead. The next round of lead and copper
rule monitoring will be in 2024.
Lead Tests in Childcare Facilities
and Public Schools
Presently we are working with San Francisco Unified
School District to help develop a long-term, recurring lead monitoring program for the K-12 schools. In 2023, we
assisted the school district in completing lead sampling in childcare centers on public school campuses.
Summary: Lead
Exposure to lead can cause serious health
effects. This is especially true for pregnant
women and young children. Lead in drinking
water usually comes from materials in service
lines and home plumbing. There are no known
lead service lines in our system. We cannot
control the plumbing materials used in your
home. You share the responsibility of protecting
yourself from lead in your home plumbing. We
offer water testing for lead for a small fee. If you
are enrolled in the Women, Infants, and Children
program you may receive free lead testing. To
learn more, visit epa.gov/lead.
Key Water Quality Terms7
2023 Annual Water Quality Report
9 San Francisco Water System - Water Quality Data for 2023 This report is a snapshot of last year’s water quality. The tables below list detected contaminants in our drinking water (unless otherwise indicated) in 2023 and the information about their typical sources. Contaminants below detection limits for reporting are not shown, in accordance with regulatory guidance. The San Francisco Public Utilities Commission holds a State Water Resources Control Board monitoring waiver for some contaminants in the surface water and groundwater supplies, and therefore their monitoring frequencies are less than annual. Visit sfpuc.org/WaterQuality for a list of all water quality parameters monitored in raw water and treated water in 2023.
DETECTED CONTAMINANTS UNIT MCL/TT PHG
OR (MCLG)
RANGE OR
LEVEL FOUND
AVERAGE
OR [MAX] TYPICAL SOURCES IN DRINKING WATER
TURBIDITY
Unfiltered Hetch Hetchy Water NTU 5 N/A 0.3 - 0.9 (1) [2] Soil runoff Filtered Water from Sunol Valley
Water Treatment Plant (SVWTP)
NTU
-
1 (2)
Min 95% of samples
≤0.3 NTU (2)
N/A
N/A
-
100%
[0.2]
-
Soil runoff
Soil runoff
Filtered Water from Harry Tracy
Water Treatment Plant (HTWTP)
NTU
-
1 (2)
Min 95% of samples
≤0.3 NTU (2)
N/A
N/A
-
99.4% - 100%
[0.6]
-
Soil runoff
Soil runoff
DISINFECTION BY-PRODUCTS AND PRECURSOR
Total Trihalomethanes ppb 80 N/A 15 - 93 [48]
(3) By-product of drinking water disinfection
Five Haloacetic Acids ppb 60 N/A 7.9 - 77 [42] (3) By-product of drinking water disinfection Bromate ppb 10 0.1 ND - 1.7 [1] (4) By-product of drinking water disinfection Total Organic Carbon (5) ppm TT
(% Removal Ratio)
N/A 1.2 - 1.8 [1.5] (4) Various natural and man-made sources
MICROBIOLOGICAL
Giardia lamblia cyst/L TT (0) 0 - 0.13 0.03 Naturally present in the environment
INORGANICS
Fluoride (source water)
(6) ppm 2.0 1 0.4 - 2.6 0.6 Erosion of natural deposits; water additive to promote strong teeth Nitrate (as N) ppm 10 10 ND - 0.6 ND Erosion of natural deposits Chloramine (as chlorine) ppm MRDL = 4.0 MRDLG = 4 <0.1 - 3.6 [2.7] (4) Drinking water disinfectant added for treatment
CONSTITUENTS WITH
SECONDARY STANDARDS UNIT SMCL PHG RANGE AVERAGE TYPICAL SOURCES IN DRINKING WATER Aluminum (7) ppb 200 600 ND - 82 ND Erosion of natural deposits; some surface water treatment residue Chloride ppm 500 N/A <3 - 17 8.7 Runoff / leaching from natural deposits Color Unit 15 N/A <5 - 5 <5 Naturally-occurring organic materials Iron ppb 300 N/A <6 - 42 19 Leaching from natural deposits Manganese ppb 50 N/A <2 - 4.6 2.6 Leaching from natural deposits Specific Conductance µS/cm 1600 N/A 32 - 289 175 Substances that form ions when in water Sulfate ppm 500 N/A 1.2 - 36 17 Runoff / leaching from natural deposits Total Dissolved Solids ppm 1000 N/A <20 - 153 84 Runoff / leaching from natural deposits Turbidity NTU 5 N/A 0.1 - 0.6 0.3 Soil runoff
LEAD AND COPPER
(Samples Taken from Select
Customers’ Taps) (8)
UNIT AL PHG RANGE 90TH
PERCENTILE TYPICAL SOURCES IN DRINKING WATER
Copper ppb 1300 300 ND - 383 60 Internal corrosion of household water plumbing systems Lead ppb 15 0.2 ND - 190 7.1 Internal corrosion of household water plumbing systems
NON-REGULATED WATER
QUALITY PARAMETERS UNIT ORL RANGE AVERAGE KEY
Alkalinity (as CaCO3) ppm N/A 3.1 - 103 46 < / ≤ = less than / less than or equal to AL = Action Level
Max = Maximum
Min = Minimum
N/A = Not Available
ND = Non-Detect
NL = Notification Level
NoP = Number of Coliform-Positive Sample
NTU = Nephelometric Turbidity Unit
ORL = Other Regulatory Level
ppb = part per billion
ppm = part per million
µS/cm = microSiemens/centimeter
Boron ppb 1000 (NL) 22 - 65 40
Calcium (as Ca) ppm N/A 2.9 - 24 13
Chlorate(9) ppb 800 (NL) 30 - 749 141
Chromium (VI) ppb N/A 0.11 - 0.35 0.23
Hardness (as CaCO3) ppm N/A 7.5 - 86 46
Magnesium ppm N/A 0.2 - 8.4 4.7
pH - N/A 8.4 - 9.8 9.2
Potassium ppm N/A 0.3 - 1.7 1
Silica ppm N/A 4.4 - 9.4 6.2
Sodium ppm N/A 2.7 - 20 14
Strontium ppb N/A 14 - 331 139
2023 Annual Water Quality Report
10 San Francisco Local Groundwater - Water Quality Data for Year 2023 Footnotes on San Francisco Water System - Water Quality Data:
(1) These are monthly average turbidity values measured every 4 hours daily. (2) This is a treatment technique requirement for filtration systems. (3) This is the highest locational running annual average value. (4) This is the highest running annual average value. (5) Total organic carbon (TOC) is a precursor for disinfection byproduct formation. The treatment technique requirement applies to the filtered water from the Sunol Valley Water Treatment Plant (SVWTP) only. In 2023, the range of the SVWTP effluent TOC levels were 0.6 ppm - 3.3 ppm. (6) Natural fluoride in the Hetch Hetchy source was non-detect. Elevated fluoride levels in raw water to the water treatment plants were attributed to the transfer of fluoridated Hetch Hetchy water into the local reservoirs. In 2023, the average fluoride level in raw water sources was 0.3 mg/L. (7) Aluminum also has a primary MCL of 1,000 ppb. (8) The most recent Lead and Copper Rule monitoring was in August 2021. Three of the 72 site samples collected at consumer taps had lead concentrations above the action level. (9) The detected chlorate in the treated water is a degradation product of sodium hypochlorite, which we use for water disinfection.
Note: The different water sources blended at different ratios throughout the year have resulted in varying water quality. Additional water quality data may be obtained by calling our Water Quality Division toll-free number at 877-737-8297.
Treated Water
(Sunset
Reservoir)
DETECTED CONTAMINANTS UNIT MCL
PHG
OR
(MCLG)
RANGE AVERAGE TYPICAL SOURCES IN DRINKING WATER
INORGANICS
Chromium (VI) ppb N/A 0.02 0.02 - 0.31 0.12 Leaching from natural deposits; waste discharges from electroplating
Fluoride ppm 2.0
(Natural-Source)
1 0.6 - 0.8 0.7 Erosion of natural deposits; water additive to promote strong teeth
CONSTITUENTS WITH
SECONDARY STANDARDS UNIT SMCL PHG
RANGE
OR LEVEL
FOUND
AVERAGE TYPICAL SOURCES IN DRINKING WATER
Aluminum (1) ppb 200 600 60 60 Erosion of natural deposits; some surface water treatment residue
Chloride ppm 500 N/A 4.1 - 16 7.9 Runoff / leaching from natural deposits Iron ppb 300 N/A 32 - 34 33 Leaching from natural deposits Manganese ppb 50 N/A 2.3 - 2.4 2.3 Leaching from natural deposits Specific Conductance µS/cm 1600 N/A 54 - 223 112 Substances that form ions when in water Sulfate ppm 500 N/A 4.1 - 4.2 4.2 Runoff / leaching from natural deposits Total Dissolved Solids ppm 1000 N/A 38 38 Runoff / leaching from natural deposits Turbidity NTU 5 N/A 0.1 - 0.6 0.3 Soil runoff
Raw Water
(San Francisco
Local
Groundwater
Wells)
DETECTED CONTAMINANTS UNIT MCL
PHG
OR
(MCLG)
RANGE AVERAGE TYPICAL SOURCES IN DRINKING WATER
INORGANICS (2)
Chromium (VI) ppb N/A 0.02 5.4 - 24 15 Leaching from natural deposits; waste discharges from electroplating
Chromium ppb 50 (100) ND - 21 11 Erosion of natural deposits; discharge from electroplating
Nitrate (as nitrogen) ppm 10 10 6.1 - 7.8 6.8 Landscape fertilizers and leaked wastewater
VOLATILE ORGANICS
Carbon tetrachloride (3) ppb 0.5 0.1 ND - 1 ND Discharge from chemical plants and other industrial activities
Tetrachloroethylene
(4) ppb 5 0.06 1.7 - 2.5 2.1 Discharge from factories, dry cleaners, and auto shops (metal degreaser)
NON-REGULATED WATER
QUALITY PARAMETERS UNIT ORL
RANGE AVERAGE
pH - N/A 7.7 - 8.1 7.9
Strontium ppb N/A 145 - 189 167
Footnotes on San Francisco Local Groundwater - Water Quality Data for 2023:
(1) A
luminum also has a primary MCL of 1,000 ppb. (2) These contaminants are detectable in the raw groundwater. Blending of groundwater with surface water has been approved by State Water Resources Control Board (SWRCB) as treatment for these contaminants. In 2023, only two of the six local wells (Lake Merced Well and West Sunset Well) delivered groundwater to the distribution system intermittently. (3) This contaminant was detected at South Sunset Well but not in the blend water at Sunset Reservoir. South Sunset Well was out of service in 2023. (4) Tetrachloroethylene was detected at Golden Gate Central Well, which supplied to Golden Gate Park throughout 2023 for irrigation only.
P.O. Box 7369
San Francisco, CA 94120-7369
Follow Us @MySFPUC
San Francisco Public Utilities Commission
Every day we deliver high-quality drinking water to 2.7 million people in San Francisco, Alameda, Santa Clara and San Mateo counties. We generate clean, reliable hydroelectricity that powers 100% of San Francisco’s vital services, including police and fire stations, street lights, Muni, SF General Hospital and more.
Water quality policies are decided at SFPUC
Commission meetings, held the 2nd and
4th Tuesdays of each month at 1:30 pm
in San Francisco City Hall, Room 400.
This report contains important information about your drinking water. Translate it, or speak with someone who understands it.
Este informe contiene información muy importante sobre su agua potable. Tradúzcalo o hable con alguien que lo entienda bien.
Mahalaga ang impormasyong ito. Mangyaring ipasalin ito.
Cé rapport contient des information importantes concernant votre eau potable. Veuillez traduire, ou parlez avec quelqu’ un qui peut le comprendre.
Этот отчет содержит важную информацию о вашей питьевой воды. Переведите его или поговорите с тем, кто это понимает.
此份水質報告， 內有重要資訊。 請找他人為你翻譯和解說清楚。
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。 翻訳を御依頼なされ
るか、 内容をご理解なさっておられる方にお尋ね下さい。
Tim Paulson, PRESIDENT
Anthony Rivera, VICE PRESIDENT
Newsha K. Ajami, COMMISSIONER
Kate H. Stacy, COMMISSIONER
This report contains important information about our drinking water.
Please contact SFPUC Communications at 628-215-0940 or email [email protected] for assistance.
Este informe contiene información muy importante sobre su agua potable. Favor de comunicarse en tel 628-215-0940 o [email protected] para asistencia.
此份水質報告，內有重要資訊。請找他人為你翻譯和解說清楚。
City of San Francisco
2024 Annual Water
Quality Report
Summary of Water
Quality Report
The San Francisco Public Utilities
Commission (SFPUC) is a public
agency. We run a regional water
system. This system delivers drinking
water to over 2.7 million residents
and thousands of businesses in the
Bay Area. Every year we produce
Water Quality Reports for customers
both in San Francisco and outside of
San Francisco. In this report, you can
learn where your water comes from,
how we treat it, and its overall quality.
Our pledge is to provide high-quality
drinking water to all our customers.
In 2024, our water met all federal
and state standards.
City of San Francisco
2024 Annual Water Quality Report
Table of Contents:
1. Introduction ................................ 1
2. Ou
r Drinking Water Sources and Treatment .... 1
3. Wa
ter Quality .............................. 2
4. Fluor
idation and Dental Fluorosis ............ 3
5. Dr inking Water and Lead .................... 4
6. Spe
cial Health Needs ....................... 8
7. Wa
ter Quality and Treatment Spotlights ...... 8
8. Ke
y Water Quality Terms ................... 10
City of San Francisco | 2024 Annual Water Quality Report 1 Almost all of our drinking water supply comes from the San Francisco Regional Water System (SFRWS), which is
the wholesale system owned and operated by the San
Francisco Public Utilities Commission (SFPUC). The supply consists of surface water and groundwater that are well protected and carefully managed. The surface water is
stored in reservoirs in the Sierra Nevada, the East Bay, and San Mateo County, and the groundwater is kept in a
deep aquifer in the northern part of San Mateo County
and the western side of San Francisco. Maintaining this variety of sources is an important component of the
SFPUC’s near- and long-term water supply management
strategy. A diverse mix of sources protects us from
potential disruptions due to emergencies or natural
disasters, provides resiliency during periods of drought, and helps us ensure a long-term, sustainable water
supply as we address issues such as climate uncertainty, regulatory changes, and population growth.
To meet drinking water standards for human consumption, all surface water the SFPUC supplies must undergo
proper treatment. Water from Hetch Hetchy Reservoir
is exempt from state and federal filtration requirements due to its exceptional quality. It is subject to disinfection using ultraviolet light and chlorine, pH adjustment
for optimum corrosion control, fluoridation for dental
health protection, and chloramination for maintaining
disinfectant residual and minimizing the formation of
regulated disinfection byproducts. Water from local Bay Area reservoirs in the East Bay and upcountry non-Hetch Hetchy sources are delivered to the Sunol Valley Water
Treatment Plant. Water from reservoirs in San Mateo
County is delivered to the Harry Tracy Water Treatment
Plant. Water treatment at these plants consists of filtration, ozonation, chloramination, fluoridation, taste and odor removal, and optimum corrosion control. In 2024, we did not use upcountry non-Hetch Hetchy sources of water. A
very small amount of local groundwater (0.1%) contributed to the drinking water supply.
The San Francisco Public Utilities Commission (SFPUC)
provides high-quality drinking water that meets all
federal and state standards to 2.7 million residents and thousands of businesses in cities and towns across the
region. Through careful stewardship of both our natural resources and our infrastructure, our goal is to deliver high-quality drinking water to homes and businesses
every day. Your ratepayer dollars support this mission
and allow us to make crucial upgrades to the system.
Whether installing new pipes to best withstand
earthquakes or adding extra layers of water quality
treatment, we’re investing in a reliable future.
Understanding this Report
The SFPUC produces a Water Quality Report every year
to provide specific information about where your water
comes from, how we treat it, and its overall quality. We do this not only to meet a regulatory requirement but
also to provide an educational opportunity for you to
understand our drinking water operations and public
health protection efforts.
We are committed to providing high-quality drinking
water for all our customers. Our system is large, and we work across several counties to maintain the system
that delivers drinking water for your consumption. It is our hope that this report will not only provide you with greater knowledge of your water, but also an increased
understanding of the considerable skill, talent, and effort of the SFPUC staff that goes into ensuring businesses
and residents have reliable access to this precious
resource. We’re proud of our water, and we hope you are too. We hope you enjoy getting to know a little more about who we are as an agency and how you can get involved.
2. Our Drinking Water Sources and Treatment
2. Summary: Water Sources
Surface water from reservoirs makes up almost
all of the water you receive. In 2024, we also used
a very small amount of groundwater. Using a mix
of sources protects us from supply interruptions
in the future. These interruptions can be due to
drought, climate change, or population growth.
We treat all drinking water before delivering it to
you. Our highly skilled staff make sure it meets
all federal and state standards. In 2024, we
performed nearly 100,000 drinking water tests.
Samples came from reservoirs and other points
in the water system.
1 1. Introduction
City of San Francisco | 2024 Annual Water Quality Report 2 3. Water Quality
We regularly collect and test water samples from
reservoirs and designated sampling locations
throughout the system to ensure that the water
delivered to you meets all federal and state drinking
water standards. In 2024, we conducted more than
96,950 drinking water tests of samples from source,
transmission, and distribution system locations. This is in addition to the extensive treatment process control
monitoring performed by our certified operators and
online instruments.
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. Collectively these are called contaminants. Therefore, 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. To ensure that tap water is safe to drink, the United States Environmental Protection Agency (USEPA) and the State Water Resources Control Board
(SWRCB) prescribe regulations that limit the amount of
certain contaminants in water provided by public water
systems. The United States Food and Drug Administration regulations and California law also establish limits for contaminants in bottled water that provide the same
protection for public health.
Contaminants and Regulations
Throughout the United States, sources of drinking water (both tap water and bottled water) can include rivers,
lakes, oceans, streams, ponds, reservoirs, springs, and wells. Contaminants present may include:
•
Mic
robial contaminants, such as viruses and bacteria
that may come from sewage treatment plants, septic
systems, agricultural livestock operations, and wildlife • Ino
rganic 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
• Pe
sticides and herbicides that may come from a variety
of sources such as agriculture, urban stormwater runoff and residential uses
•
Or
ganic 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
runoff, agricultural application, and septic systems
•
Rad
ioactive contaminants, which can be naturally
occurring or be the result of oil and gas production
and mining activities
More information about contaminants and potential
health effects can be obtained by calling the USEPA’s
Safe Drinking Water Hotline at 800-426-4791, or at
epa.gov/safewater.
Protection of Watersheds
The San Francisco Public Utilities Commission (SFPUC)
conducts watershed sanitary surveys for the Hetch
Hetchy source annually and for non-Hetch Hetchy surface water sources every five years. The latest sanitary surveys for the non-Hetch Hetchy watersheds were completed
in 2021 for the period of 2016-2020. These surveys
document the SFPUC’s stringent watershed protection
activities that are implemented with support from partner agencies including the National Park Service and the
United States Forest Service.
These surveys not only evaluate the sanitary conditions and water quality of the watersheds but also describe
the results of watershed management activities
conducted in the preceding years. Wildfire, wildlife,
livestock, and human activities continue to be the
potential contamination sources. You may contact the
San Francisco District Office of the SWRCB’s Division of Drinking Water at 510-620-3474 for more information.
Unregulated Contaminant Monitoring Rule
Unregulated contaminant monitoring helps the USEPA
and the SWRCB determine where certain contaminants
occur and whether the contaminants need to be regulated.
We completed the fifth Unregulated Contaminant
Monitoring Rule monitoring for the system in 2023
and 2024. All results of 29 per- and poly-fluoroalkyl
substances (PFAS) and lithium were "none detected."
Together with two previous rounds of voluntary PFAS
monitoring, we are proud to report that our water
supplies are not compromised by these contaminants.
For additional information about PFAS, you may visit
the SWRCB’s website waterboards.ca.gov/pfas, our
website sfpuc.gov/TapWater, or the USEPA’s website
epa.gov/pfas.
City of San Francisco | 2024 Annual Water Quality Report 3 4. Fluoridation and Dental Fluorosis
Mandated by State law, water fluoridation is a widely
accepted practice proven safe and effective for
preventing and controlling tooth decay. Based on the
recommendation from the Centers for Disease Control
and Prevention (CDC) and the State Water Resources
Control Board’s (SWRCB) regulatory guidance, the San
Francisco Public Utilities Commission has maintained
an optimal fluoride level at 0.7 milligram per liter (mg/L, or part per million, ppm), since 2015. The optimal level provides the benefits of tooth decay prevention while
minimizing the chance that children develop dental
fluorosis. Infants fed formula mixed with water containing fluoride at this level may still have a chance of developing mild to very mild fluorosis, which can cause tiny white lines or streaks in their teeth. These marks are often
only visible under a microscope. Even in cases where the marks are visible, they do not pose any health risk. To lessen the chance of dental fluorosis, you may choose to use low-fluoride bottled water to prepare infant formula.
Nevertheless, children may still develop dental fluorosis due to fluoride intake from other sources such as food, toothpaste, and dental products. Contact your healthcare provider or the SWRCB if you have concerns about dental fluorosis. For additional information about fluoridation or oral health, visit the SWRCB’s website waterboards.
ca.gov/drinking_water/certlic/drinkingwater/
Fluoridation.html, the CDC’s website cdc.gov/
fluoridation, or our website sfpuc.gov/TapWater.
4. Summary: Fluoridation
We add fluoride to our water. California law
mandates fluoridation. It is proven safe. It is also
effective at preventing and controlling tooth decay.
Our fluoride levels match the State’s optimal level.
To learn more, visit waterboards.ca.gov/drinking_
water/certlic/drinkingwater/Fluoridation.html,
cdc.gov/fluoridation, or sfpuc.gov/TapWater.
3. Summary: No PFAS Detected
You may have heard about PFAS. These are man-made chemicals that have been used in industry and consumer products worldwide since the 1940s. We did not detect PFAS in our water. To learn more, visit waterboards.ca.gov/pfas, sfpuc.gov/TapWater, and/ or epa.gov/pfas. 3 City of San Francisco | 2024 Annual Water Quality Report 4 Exposure to lead, if present, can cause serious health effects in people of all ages, especially for pregnant
women and young children. Infants and children who
drink water containing lead could have decreases in
intelligent quotient and attention span as well as
increases in learning and behavior problems. The
children of women who are exposed to lead before or
during pregnancy can have an increased risk of these
adverse health effects. Adults can have increased risks of heart disease, high blood pressure, kidney, or
nervous system problems.
Lead in drinking water is primarily from materials and
components associated with service lines and home
plumbing. We are responsible for providing high-quality drinking water and removing lead pipes, but we cannot
control the variety of materials used in plumbing
components in your home. Because lead levels may vary
over time, lead exposure is possible even when your tap sample results do not detect lead at one point in time.
You share the responsibility for protecting yourself and your family from the lead in your home plumbing by taking one or more of the following actions:
•
Iden
tify and remove lead materials within your
home plumbing.
• If yo
u use a water filter, make sure it’s certified for
lead to National Sanitation Foundation (NSF)/ANSI
standards. Make sure to replace and maintain the filter according to the manufacturer’s instructions.
• Us
e only cold water for drinking, cooking, and making
baby formula. Hot tap water can potentially have higher concentrations of lead. (Do not boil your water to
remove lead. Boiling water will not remove lead).
•
Flu
sh your pipes for several minutes before using your
water for drinking, cooking, and preparing baby formula (this can be done by running your tap, taking a shower, doing laundry or a load of dishes, and reusing for
watering plants).
•
Flu
sh for a longer period if you have pipes made of lead
or galvanized material.
If you are concerned about lead in your water, you may
wish to have your water tested. We offer low-cost water tests for lead at $25 per tap to our customers. Call 311 or access our website sfpuc.gov/LeadTest for details.
Clients enrolled in the Women, Infants and Children
program managed by the San Francisco Department of
Public Health may receive free lead test vouchers from
that department. In addition to our water source
protection efforts and low-cost lead tests, we continue the following actions to minimize customer exposure to
lead in water:
•
Kee
p and update an inventory of service line materials
between the water main and the building (can be found
at sfpuc.gov/lead)
• Rep
lace remaining brass meters with lead-free
automated water meters
• Rep
lace lead service pipelines if identified
• Upd
ate flushing guidance for buildings
• Tes
t for lead in tap water at day care facilities
and schools
Information about lead in drinking water, testing methods, and steps you can take to minimize exposure is available at epa.gov/lead.
Lead Service Line Inventory
and Replacement
Utility-Owned Service Lines
The San Francisco Public Utilities Commission (SFPUC)
removed all known lead service lines in the 1980’s. In July 2020, we submitted a 10-year lead component
replacement schedule to the State Water Resources
Control Board (SWRCB). We have begun replacing the
estimated 1,580 utility-owned galvanized steel service
lines that may have lead whips. A lead whip is a short
piece of lead pipe, typically 3 feet or less, connecting the large pipe in the street to the smaller pipe that carries water to your building. There were 13,140 utility-owned service lines made of either galvanized steel or unknown materials. After several years of field inspections, the confirmed total galvanized service lines were updated to be 1,423. As of March 2025, we had replaced 1,099 of
these galvanized services with new copper pipelines.
Lead whips were found in only 21% of the removed
galvanized services. As part of this replacement program, we have also created a customer lookup map that is
currently posted on the SFPUC’s website, sfpuc.gov/Lead.
A customer can use the map to identify if an address has a galvanized service line scheduled for replacement. The replacement program is 77% complete and scheduled to
be completed by mid-2026, four years ahead of schedule.
Customer-Owned Service Lines
Starting in 2022, we began the preparation of an
inventory of customer-side service lines in accordance
5. Drinking Water and Lead
City of San Francisco | 2024 Annual Water Quality Report 5 5. Summary: Lead
Exposure to lead can cause serious health effects. This is especially true for pregnant women and young children.
Lead in drinking water usually comes from materials in service lines and home plumbing. There are no known lead service lines in our system. We cannot control the plumbing materials used in your home. You share the responsibility of protecting yourself from lead in your home plumbing. We offer water testing for lead for a small fee. If you are enrolled in the Women, Infants, and Children program you may receive free lead testing. To learn more about lead in water, visit epa.gov/lead.
with the United States Environmental Protection Agency’s (USEPA) Lead and Copper Rule Revisions. As of October
2024, we completed 9,042 inspections and developed
a statistical and predictive model to help determine the probability that lead might be found without inspecting all customer-side service lines. The rigorous statistical method concluded that there is less than 1% probability a customer-side service line is made of lead. Additionally, our experienced plumbers, some with 40 years of
knowledge of our distribution system, confirm that they have never encountered customer-side service lines
made of lead.
Our initial service line inventory submitted to the SWRCB in October 2024 reported no lead lines; however, there
are 653 galvanized service lines that require replacement and 407 Lead-Status Unknown lines on the customer
side. A galvanized service line requiring replacement is defined by the USEPA as a galvanized steel service line on the customer side that may be downstream of a
previously removed lead service line on the utility side.
Such galvanized service lines may have trapped some
lead, and, when they are disturbed, can release lead.
A Lead-Status Unknown service line means the material
of the pipeline cannot be identified or confirmed from
inspection through the meter box. Reducing the number
of Lead-Status Unknown service line is a priority goal
for the SFPUC. In November 2024, we sent notification
letters to these customers about the unknown material
status of their service lines and are reaching out to these customers for free inspection of their service lines.
Website information and a lookup map is routinely
updated to show the locations of these service lines.
Email [email protected] to schedule your free
inspection to remove your Lead-Status Unknown
service line.
Lead and Copper Tap Sampling Results
We conducted our triennial Lead and Copper Rule
monitoring at 50 customer tap sites in 2024. Our 90th
percentile value of lead was 5 parts per billion (ppb), and all results were below the regulatory Action Level
of 15 ppb. These sampling results are accessible at
sfpuc.gov/Lead. The next round of lead and copper
rule monitoring will be in 2027.
Lead Tests in Childcare Facilities and
Public Schools
Starting in 2028, the SFPUC will begin lead monitoring
in schools to meet the USEPA’s Lead and Copper Rule
Improvement regulations. Within 5 years of 2028, the
SFPUC will sample all K-8 grade schools in San Francisco for lead. Currently, the SFPUC offers lead sampling at
9- to 12-grade schools if requested, even though we
are not required to test these schools.
City of San Francisco | 2024 Annual Water Quality Report 5 City of San Francisco | 2024 Annual Water Quality Report 6 6
City of San Francisco | 2024 Annual Water Quality Report
City of San Francisco | 2024 Annual Water Quality Report 7 Water Quality Report Card
This Water Quality Report card shows the state of your water. This year, our water met all federal and state standards.
Potential Contaminants Why We Test For It Likely Source Your Water Source Microbes
Microscopic organisms
such as Coliform
bacteria, Giardia
and Cryptosporidium
Can make people
sick after drinking
several glasses.
Naturally present in
the environment or
from animals or
human activity
Surpasses State
and Federal
Water Quality
Requirements
Copper and Lead
Levels can cause health
issues over an extended
period of time.
Corrosion of
indoor plumbing
Surpasses State
and Federal
Water Quality
Requirements
Disinfection Byproducts
Byproducts of the process
of disinfecting drinking
water - trihalomethanes
and haloacetic acids
High levels can
cause health issues
over an extended
period of time.
Water Disinfection
Process
Surpasses State
and Federal
Water Quality
Requirements
Turbidity – cloudiness of
water from suspended
particles in the water
Less turbid
water indicates
high water quality
Soil runoff
Surpasses State
and Federal
Water Quality
Requirements
Fluoride
High levels can
cause marks on teeth
over an extended
period of time.
Erosion of natural
deposits and mandated
water additive for
dental health
At the
optimal CDC
recommended
level
PFAS
Synthetic organic
chemicals that are
resistant to heat,
water, and oil
Widely used in
consumer and
industrial products
No PFAS
detected
City of San Francisco | 2024 Annual Water Quality Report 8 6. Special Health Needs
7. Wa
ter Quality and Treatment Spotlights
Some people may be more vulnerable to contaminants
in drinking water than the general population.
Immunocompromised persons, such as those with
cancer undergoing chemotherapy, persons who have
undergone organ transplants, people with Human
Immunodeficiency Virus/Acquired Immunodeficiency
Syndrome 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 healthcare providers.
Cryptosporidium is a parasitic microbe found in surface water. We regularly test for this waterborne pathogen and found it at very low levels in source water and treated water in 2024. However, current test methods approved
by the United States Environmental Protection Agency
(USEPA) do not distinguish between dead organisms
and those capable of causing disease. Ingestion of
Cryptosporidium may cause cryptosporidiosis with
symptoms of nausea, abdominal cramps, diarrhea,
and associated headaches. Cryptosporidium must
be ingested to cause disease, and it may be spread
through means other than drinking water.
Guidelines on appropriate means to lessen the risk
of infection by Cryptosporidium and other microbial
contaminants are available from the USEPA’s Safe
Drinking Water Hotline at 800-426-4791 or at
epa.gov/safewater.
Making Upgrades: Ozonation at Sunol Valley
Water Treatment Plant
As the San Francisco Public Utilities Commission
(SFPUC) provides drinking water to 2.7 million residents daily, we are continually upgrading our water treatment infrastructure. This year, we began construction at the Sunol Valley Water Treatment Plant in the East Bay to
install ozone treatment facilities. The Sunol Valley Water Treatment Plant treats water from both San Antonio
Reservoir and Calaveras Reservoir in the East Bay, and
water from Hetch Hetchy Reservoir in the Sierra Nevada
if needed. As climate change produces more extreme
weather, we have seen more algal blooms in the two
local reservoirs during the region’s warmer months.
Nutrient availability, temperature, and sunlight can
cause these algal blooms, which may cause drinking
water to have a taste or odor that some people
describe as “earthy.” The SFPUC is installing innovative technology to ensure that potential algal blooms don’t
affect the taste and odor of our water supply.
What is Ozonation?
When construction finishes in 2028, the Sunol Valley
Water Treatment Plant will treat raw water with ozone.
Ozonation works by injecting ozone into raw water where it immediately oxidizes, or destroys, organic material
which can cause these taste and odor concerns. This
treatment has already been in use at the Harry Tracy
6. Summary: Special
Health Needs
We measure contaminants in our water supply.
Drinking water will likely have small amounts of
some contaminants. This does not mean that the
water is unsafe. Bottled water also likely has some
contaminants. Federal and state governments
closely regulate drinking water. They limit how
much of certain contaminants can exist in public
water. This year, our water met all federal and
state standards.
Some people may need to be more careful of
contaminants. This includes:
• Immunocompromised people
• People who have had an organ transplant(s)
• People with Human Immunodeficiency
Virus/Acquired Immunodeficiency Syndrome
or other immune system disorders
• Some elderly people and infants
These people should seek advice from their
healthcare providers. To learn more, visit
epa.gov/safewater. Or call 800-426-4791.
City of San Francisco | 2024 Annual Water Quality Report 9 Water Treatment Plant on the Peninsula since the
1990s. Investments in our infrastructure mean you’ll
continue to have great-tasting, high-quality water
whenever you need it.
San Francisco Public Utilities Commission’s
Water Treatment Plants Recognized
for Excellence
In 2024, the American Water Works Association (AWWA)
honored the SFPUC with two awards for our exceptional
water quality. The awards were granted through the
AWWA’s Partnership for Safe Water, which requires
participating utilities to produce water quality that is significantly higher than regulatory requirements. The
Harry Tracy Water Treatment Plant and the Sunol Valley
Water Treatment Plant were recognized for meeting
strict water quality standards for the last 20 and 25
years respectively.
Water Quality Strategic Plan
The San Francisco Public Utilities Commission (SFPUC)
has a history of proactively identifying potential water quality issues and considering them in capital planning and operational decisions. This practice has enabled the SFPUC to comply with all state and federal drinking
water regulations and continue to provide high quality
water to customers. To create a sound foundation for
capital and operational investments that may be
required in the next decade to protect drinking water
quality, our Water Quality Division (WQD) regularly
assesses potential real-world concerns that could
impact our water quality and identified recommendations to consider for implementation. In 2024, the WQD
conducted its periodic update to the Water Quality
Strategic Plan that was initially adopted in 2008.
This updated plan provides an overview of the strategic planning process, activities currently underway within
the Water Quality Division, and recommends new
activities. The plan is available at sfpuc.gov/WQ-Planning.
City of San Francisco | 2024 Annual Water Quality Report 9 10
City of San Francisco | 2024 Annual Water Quality Report • 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.
•
Max
imum 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 United States Environmental Protection Agency.
•
Max
imum 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.
•
Max
imum 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.
•
Max imum Residual Disinfectant Level (MRDL):
The highest level of a disinfectant allowed in drinking water. There is convincing evidence that the addition
of a disinfectant is necessary for control of microbial contaminants.
•
Tre
atment Technique (TT): A required process
intended to reduce the level of a contaminant in
drinking water.
•
Pri
mary Drinking Water Standard (PDWS): MCLs,
MRDLs, and TT for contaminants that affect
health, along with their monitoring and reporting
requirements.
•
Regu
latory Action Level: The concentration of a
contaminant which, if exceeded, triggers treatment or
other requirements that a water system must follow.
•
Turb
idity: A water clarity indicator that measures the
cloudiness of the water and is also used to indicate
the effectiveness of a filtration system.
8. Key Water Quality Terms
San Francisco Water System - Water Quality Data for 2024 The system meets primary and secondary drinking water standards in 2024. The tables below list detected contaminants in our drinking water (unless indicated otherwise) and the information about their typical sources in accordance with regulatory guidance. The San Francisco Public Utilities Commission holds monitoring waivers approved by the State Water Resources Control Board for some contaminants in the surface water and groundwater supplies, and they are monitored less than once a year. Visit sfpuc.gov/WaterQuality for a list of all water quality parameters we monitored in raw water and treated water in 2024.
DETECTED CONTAMINANTS UNIT MCL/TT PHG
OR (MCLG)
RANGE OR
LEVEL FOUND
AVERAGE
OR [MAX] TYPICAL SOURCES IN DRINKING WATER
TURBIDITY
Unfiltered Hetch Hetchy Water NTU 5 N/A 0.3 - 0.5 (1) [2.1] Soil runoff Filtered Water from Sunol Valley
Water Treatment Plant (SVWTP)
NTU
-
TT=Max 1
TT=Min 95% of samples
≤0.3 NTU
N/A
N/A
-
99.97%
[0.4]
-
Soil runoff
Soil runoff
Filtered Water from Harry Tracy
Water Treatment Plant (HTWTP)
NTU
-
TT=Max 1
TT=Min 95% of samples
≤0.3 NTU
N/A
N/A
-
100%
[0.1]
-
Soil runoff
Soil runoff
DISINFECTION BY-PRODUCTS AND PRECURSOR
Total Trihalomethanes ppb 80 N/A 16 - 54 [49]
(2) By-product of drinking water disinfection
Five Haloacetic Acids ppb 60 N/A 9 - 41 [42] (2) By-product of drinking water disinfection Bromate ppb 10 0.1 ND - 5.9 [3] (3) By-product of drinking water disinfection
INORGANICS
Chromium (VI) ppb 10 0.02 ND - 0.2 0.1 Erosion of natural deposits Fluoride (source water) (4) ppm 2.0 1 ND - 0.8 0.3 Erosion of natural deposits; water additive to promote strong teeth Nitrate (as N) ppm 10 10 ND - 0.4 ND Erosion of natural deposits Chloramine (as chlorine) ppm MRDL = 4.0 MRDLG = 4 <0.1 - 3.5 [2.6] (3) Drinking water disinfectant added for treatment
CONSTITUENTS WITH
SECONDARY STANDARDS UNIT SMCL PHG RANGE AVERAGE TYPICAL SOURCES IN DRINKING WATER Aluminum ppb 200 (MCL = 1000) 600 ND - 59 ND Erosion of natural deposits; some surface water treatment residue Chloride ppm 500 N/A <3 - 18 9.3 Runoff / leaching from natural deposits Iron ppb 300 N/A <6 - 41 14 Leaching from natural deposits Manganese ppb 50 N/A <2 - 2.7 <2 Leaching from natural deposits Specific Conductance µS/cm 1600 N/A 31 - 317 193 Substances that form ions when in water Sulfate ppm 500 N/A 1 - 41 18 Runoff / leaching from natural deposits Total Dissolved Solids ppm 1000 N/A 24 - 169 102 Runoff / leaching from natural deposits Turbidity NTU 5 N/A 0.1 - 0.4 0.2 Soil runoff
LEAD AND COPPER (9) UNIT RAL PHG RANGE 90TH
PERCENTILE TYPICAL SOURCES IN DRINKING WATER
Copper ppb 1300 300 ND - 152 72 Internal corrosion of household water plumbing systems Lead ppb 15 0.2 <1 - 8.8 4.9 Internal corrosion of household water plumbing systems
NON-REGULATED WATER
QUALITY PARAMETERS
UNIT ORL RANGE AVERAGE KEY
Alkalinity (as CaCO3) ppm N/A 7.4 - 120 60 < / ≤ = less than / less than or equal to Max = Maximum
Min = Minimum
N/A = Not Available
ND = Non-Detect
NL = Notification Level
NTU = Nephelometric Turbidity Unit
ORL = Other Regulatory Level
ppb = part per billion
ppm = part per million
RAL = Regulatory Action Level
μS/cm = microSiemens/centimeter
Bromide ppb N/A <10 - 29 <10
Boron ppb 1000 (NL) 23 - 65 41
Calcium (as Ca) ppm N/A 3.2 - 28 15
Chlorate (6) ppb 800 (NL) 24 - 597 144
Giardia lamblia cyst/L N/A 0 - 0.06 0.01
Hardness (as CaCO3) ppm N/A 8.4 - 106 60
Lithium ppb N/A <2 - 4 <2
Magnesium ppm N/A 0.2 - 9.5 5.7
pH - N/A 8.7 - 9.8 9.3
Silica ppm N/A 4.9 - 9.9 7.5
Sodium ppm N/A 3.1 - 24 16
Total Organic Carbon (7) ppm N/A 1.4 - 2.8 1.9
11 City of San Francisco | 2024 Annual Water Quality Report 12 San Francisco Local Groundwater - Water Quality Data for Year 2024 Footnotes on San Francisco Water System - Water Quality Data: (1) These are monthly average turbidity values measured every 4 hours daily at Tesla Treatment Facilities. (2) This is the highest locational running annual average value. (3) This is the highest running annual average value. (4) Natural fluoride in the Hetch Hetchy water was ND. Elevated fluoride levels in raw water at both SVWTP and HTWTP were attributed to transfers of fluoridated Hetch Hetchy water into local reservoirs. The fluoride levels in our treated water ranged from 0.5 ppm to 0.8 ppm with an average of 0.7 ppm. (5) The most recent Lead and Copper Rule monitoring of selected consumer taps was in August 2024. None of the 50 consumer tap samples had lead concentrations above the regulatory Action Level. (6) The detected chlorate in the treated water is a degradation product of sodium hypochlorite, which we use for water disinfection. (7) The range and average values of the total organic carbon data were from special study projects for the distribution system.
Note: Blending different water sources throughout the year resulted in varying water qualities. Additional water quality data may be obtained by calling our Water Quality Division toll-free number at 877-737-8297.
Treated Water
(Sunset
Reservoir)
DETECTED CONTAMINANTS UNIT MCL
PHG
OR
(MCLG)
RANGE AVERAGE TYPICAL SOURCES IN DRINKING WATER
INORGANICS
Chromium (VI) ppb 10 0.02 ND - 0.4 0.1 Leaching from natural deposits; waste discharges from electroplating
Fluoride ppm 2.0 1 0.6 - 0.8 0.7 Erosion of natural deposits; water additive to promote strong teeth
CONSTITUENTS WITH
SECONDARY STANDARDS UNIT SMCL PHG
RANGE
OR LEVEL
FOUND
AVERAGE TYPICAL SOURCES IN DRINKING WATER
Chloride ppm 500 N/A 3.5 - 17 8.9 Runoff / leaching from natural deposits Iron ppb 300 N/A 28 - 31 29 Leaching from natural deposits Specific Conductance µS/cm 1600 N/A 68 - 290 127 Substances that form ions when in water Sulfate ppm 500 N/A 3.3 - 17 7.9 Runoff / leaching from natural deposits Total Dissolved Solids ppm 1000 N/A 26 - 27 27 Runoff / leaching from natural deposits Turbidity NTU 5 N/A 0.1 - 0.4 0.2 Soil runoff
Raw Water
(San Francisco
Local
Groundwater
Wells)
DETECTED CONTAMINANTS UNIT MCL
PHG
OR
(MCLG)
RANGE AVERAGE TYPICAL SOURCES IN DRINKING WATER
INORGANICS
Chromium (VI) (1) ppb 10 0.02 7.5 - 24 16 Leaching from natural deposits; waste discharges from electroplating
Chromium (Total) ppb 50 (100) ND - 23 11 Erosion of natural deposits Nitrate (as nitrogen) (1) ppm 10 10 5.2 - 8.2 7.1 Landscape fertilizers and leaked wastewater Perchlorate ppb 6 1 ND - 1 ND Environmental contamination from use/disposal of fireworks, explosives, and a variety of industries
NON-REGULATED WATER
QUALITY PARAMETERS UNIT ORL
RANGE AVERAGE
Lithium ppb N/A 3.8 - 4.5 4.2
pH - N/A 7.7 - 8.4 8
Footnotes: (1) These contaminants were detected in the raw groundwater. Blending of groundwater with surface water supplies in Sunset Reservoir is approved by SWRCB as treatment for these contaminants. In 2024, only two of the six local wells (Lake Merced Well and West Sunset Well) delivered groundwater to the system intermittently.
Ci
ty of San Francisco | 2024 Annual Water Quality Report
13 City of San Francisco | 2024 Annual Water Quality Report
P.O. Box 7369
San Francisco, CA 94120-7369
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Este informe contiene información muy importante sobre su agua potable. Tradúzcalo o hable con alguien que lo entienda bien.
Mahalaga ang impormasyong ito. Mangyaring ipasalin ito.
Cé rapport contient des information importantes concernant votre eau potable. Veuillez traduire, ou parlez avec quelqu’ un qui peut le comprendre.
Этот отчет содержит важную информацию о вашей питьевой воды. Переведите его или поговорите с тем, кто это понимает.
此份水質報告， 內有重要資訊。 請找他人為你翻譯和解說清楚。
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。 翻訳を御依頼なされ
るか、 内容をご理解なさっておられる方にお尋ね下さい。
Kate H. Stacy, PRESIDENT
Joshua Arce, VICE PRESIDENT
Avni Jamdar, COMMISSIONER
Steve Leveroni, COMMISSIONER
This report contains important information about our drinking water.
Please contact SFPUC Communications at 628-215-0940 or email [email protected] for assistance.
Este informe contiene información muy importante sobre su agua potable. Favor de comunicarse en tel 628-215-0940 o [email protected] para asistencia.
此份水質報告，內有重要資訊。請找他人為你翻譯和解說清楚。
2025 Public Health Goal Report San Francisco Water System Attachmen
t D
Bromate Technical Assessment and Cost Estimate for 2025 Public Health Goal Report
City and County of San Francisco Public Utilities Commission San Francisco, CA Bromate Technical Assessment and Cost Estimate for 2025 Public Health Goal Report April 2025 Prepared for: San Francisco Public Utilities Commission
Technical Memorandum San Francisco Public Utilities Commission Final Date: April 24, 2025 Draft Date: March 11, 2025 Prepared For: San Francisco Public Utilities Commission (SFPUC), Water Quality Division Eddy So, P.E. Prepared By: Trussell Technologies, Inc. Andrew Rudchenko Reviewers: Rhodes Trussell, Ph.D., P.E., BCEE David Hokanson, Ph.D., P.E., BCEE Emily Owens-Bennett, P.E., BCEE Subject: Public Health Goal Report Bromate Technical Assessment 1 Introduction The purpose of this Technical Memorandum (TM) is to provide an overview and assessment of best available technologies (BAT) that may potentially reduce bromate in SFPUC’s drinking water to below the Public Health Goal (PHG) of 0.1 micrograms per liter (µg/L). Bromate was detected at levels in excess of its PHG based on compliance monitoring data collected during the current reporting period of 2022 through 2024. Very preliminary cost estimates for select BAT alternatives are provided in support of SFPUC’s 2025 PHG Report. Bromate is a regulated disinfection byproduct (DBP) that forms when ozone is applied to waters containing naturally occurring bromide. Within the last three quarters of 2024, bromate was detected at concentrations up to 5.9 µg/L in SFPUC treated water from Harry Tracy Water Treatment Plant (HTWTP), which provides ozonation for pre-oxidation and primary disinfection. While HTWTP was the only treatment plant within SFPUC’s system that included an ozone treatment step during the current reporting period (2022-2024), ozone facilities are currently under construction at the Sunol Valley Water Treatment Plan (SVWTP). As such, costs for potential future treatment at SVWTP are also provided in this TM. An evaluation of bromate BATs was provided in SFPUC’s 2022 PHG Report, which noted several treatment processes for bromate removal, including activated ferrous iron addition, UV irradiation, and membrane or anion exchange resins. As part of this assessment, Trussell surveyed recent literature on each of these treatment
technologies to provide an update on their effectiveness for bromate control that would be applicable to the HTWTP. Trussell also surveyed recent literature to identify additional treatment alternatives for bromate beyond those listed in the 2022 PHG Report. Additional treatment alternatives that were identified included removal via biological activated carbon (BAC) filtration and zero valent iron (ZVI). The following sections present a description of the five aforementioned bromate BATs as well as preliminary cost estimates for consideration of each BAT in targeting the bromate PHG. 2 Bromate Occurrence Routine monthly monitoring of bromate from the HTWTP finished water is used to calculate running annual average (RAA) values on a quarterly basis. The quarterly reporting of RAA is used for compliance determination with the maximum contaminant level (MCL) of 0.010 mg/L, or 10 µg/L. For the three-year PHG reporting period of 2022 through 2024, a total of 33 bromate samples were analyzed from the HTWTP finished water. The results of these individual measurements are presented in Figure 2-1, along with the quarterly RAA compliance values; the detection limit for the purposes of reporting (DLR) and the PHG value are provided for reference.
Figure 2-1. Bromate monitoring values from HTWTP Effluent (2022-2024)
0.0 1.0
2.0 3.0
4.0 5.0
6.0 1/1/22 8/29/22 4/26/23 12/22/23 8/18/24 4/15/25
Bromate (µg/L)
Sample Date
monthly sample RA A
DLR = 1.0 µg/L
PHG= 0.1 µg/L
The individual bromate values (Figure 2-1) ranged from below the DLR (six occurrences) to a maximum value of 5.9 µg/L, while the quarterly RAA compliance values ranged from below the DLR to a maximum value of 3 µg/L. All values were well below the MCL of 10 µg/L. The annual average of the individual monitoring values was 1.14 µg/L in 2022, 0.98 µg/L in 2023, and 3.36 µg/L in 2024. This increase in finished water bromate concentration observed in 2024 can be correlated with an increase in the bromide values of the raw water entering HTWTP, as shown in Figure 2-2.
Figure 2-2. HTWTP raw water bromide (orange) and effluent bromate (blue; blank markers are <DLR) for 2022-2024 Considering the influence of increasing raw water bromide concentration on effluent bromate concentration (Figure 2-2), the level of bromide in the source waters for SVWTP were compared with that of HTWTP in Figure 2-3. While lower overall, the raw water bromide levels for the SVWTP source waters were comparable to the HTWTP raw water at San Andreas Reservoir Outlet (Figure 2-3) at times when the HTWTP effluent bromate levels exceeded the PHG and DL (Figure 2-1). This suggests that bromate formation above the PHG level is likely to occur at the SVWTP once the ozone facilities come online. For these reasons, bromate treatment is included for SVWTP with the cost estimates in Section 5 for future consideration. 0 10
20 30
40 50
60 1/1/22 8/29/22 4/26/23 12/22/23 8/18/24 4/15/25
Concentration (µg/L)
HTWTP raw water bromideHTWTP effluent bromateHTWTP effluent bromate (<DLR)
Figure 2-3. Raw water bromide from HTWTP at San Andreas Reservoir Outlet (orange) and SVWTP at Calaveras (light blue) and at San Antonio (dark blue) for 2022-2024 3 Best Available Technologies for Removal of Bromate The triennial PHG reporting must provide an estimate of the cost to reduce contaminants to the PHG. The cost estimates provided in the TM rely on evaluating bromate removal using treatment technologies established for achieving MCL compliance, rather than the non-enforceable PHG concentrations, and the treatment costs were extrapolated to meet the PHG. It is important to note that the BAT to reach the PHG level has not been defined and may not be available. For the purpose of this TM, the BAT removals documented in the literature for achieving the MCL and/or DLR have been extrapolated to evaluate potential expected removal with respect to the PHG concentration. Only treatment technologies that can theoretically remove a contaminant to the PHG are considered BATs; thus, the use of dilution via blending of source waters and/or control of the formation of PHG contaminants are not considered. The following subsections provide an overview of five BATs for removal of bromate including three previously identified BATs in SFPUC’s 2019 PHG Report (activated ferrous iron addition, UV irradiation, and membrane or anion exchange resins) and two new technologies identified as part of this assessment. These two new treatment methods include anoxic BAC filters and zero valent iron. While reverse osmosis (RO) has been demonstrated to be effective for the removal of bromate, the loss of water associated with the process, the lack of a suitable location for discharge of the RO concentrate, the potential requirement of an additional pass or passes of RO to treat to 0 10
20 30
40 50
60 1/1/22 8/29/22 4/26/23 12/22/23 8/18/24 4/15/25 12/11/25 Bromide Concentration (µg/L)
HTWTP raw water at San Andreas Reservoir Outlet
SV WTP raw water Calaveras
SV WTP raw water San A ntonio
the PHG, and the likely need for pretreatment precluded the further consideration of RO. 3.1 Activated Ferrous Iron Addition Bromate has been shown to be removed through reduction to the bromide ion form using reduced ferrous iron (Fe2+), which is then oxidized to ferric iron (Fe3+) by bromate and other constituents present in ozonated water, such as dissolved oxygen (DO) (Siddiqui et al., 1994). The reduction equation for acidic solutions and basic solutions by which bromate is removed through ferric iron addition is as follows (Gordon et al., 2005): 1. Reduction reaction in acidic solution: 6Fe2+ + BrO3– + 6H+ ßà 6Fe3+ + Br– + 3H2O 2. Reduction reaction in basic solution: 6Fe2+ + BrO3– + 3H2O ßà 6Fe3+ + Br– + 6OH Siddiqui et al 1994 found higher bromate removal rates at a lower pH and higher temperature, demonstrating bromate removal up to 50% at pH of 7.5, temperature of 10ºC, Fe2+ dose of 20 mg/L, and contact time of 30 minutes (representative of a typical drinking water flocculation time) using deionized water adjusted with a synthetic humic acid solution. A later study demonstrated 99% removal of bromate (relative to the DLR) from reagent water in the absence of DO at a pH of 7.5, Fe2+ dose of 30 mg/L, and 6-minute contact time (Gordon et al., 2002). While the results of both studies indicate that ferrous iron is a good reducing agent for bromate, further testing using ozonated surface water samples is needed to evaluate the impacts of bromate removal on waters with similar DO levels and natural organic matter content as HTWTP finished water. Conclusion: No studies have reported bromate removal to levels below the DLR using activated ferrous iron addition based on testing of natural waters (e.g., surface water). This suggests that achieving the PHG is not feasible with this technology. 3.2 UV Irradiation Alone and UV Advanced Reduction Processes UV irradiation is an innovative approach to bromate reduction that has been studied primarily at the bench- and pilot-scale. UV advanced reduction processes (ARPs) including UV/sulfite have also been evaluated in the literature. 3.2.a UV Irradiation Alone While the reduction of bromate is complex, involving competing reactions which vary based on site specific conditions, the overall reaction scheme can be divided in four steps [(Farkas and Klein, 1948), (Siddiqui et al., 1993), (Tammaro et al., 2016)].
1. UV catalyzes the reduction of bromate to hypobromite through a first order reaction. BrO3- + hv à OBr- + O2 2. Hypobromite exists in solution in equilibrium with hypobromous acid OBr- + H+ ßà HOBr 3. UV catalyzes the reduction of both hypobromite and hypobromous acid, forming bromide, oxygen, and hydrogen OBr- + hv à Br- + ½ O2 HOBr + hv à Br- + H+ + ½ O2 4. UV catalyzes the disproportionation reaction of hypobromite, partially reforming bromate 3OBr- + hv à BrO3- + 2Br- A bench-scale study observed bromate removal rates in ozonated groundwater samples of up to 47% at UV doses greater than 4000 mJ/cm2 (Tammarro et al 2016). While the study reports promising removal rates, the UV doses are two orders of magnitude higher than typical UV doses in drinking water applications, which may be on the order of 20 - 40 mJ/cm2. Furthermore, various studies have indicated bromate removal by UV is adversely impacted by presence of organic matters (e.g., total organic carbon [TOC]) and nitrate. More research is needed to further characterize impacts from various water matrices [(Tammarro et al 2016), (Siddiqui et al 1994)]. 3.2.b UV Sulfite ARPs Sulfite-based ARPs, also known as UV/sulfite ARPs, have emerged in recent literature as a highly efficient way to remove bromate and other contaminants such as per and polyfluoroalkyl (PFAS) substances and 2,4,6-trichlorophenol. Unlike UV irradiation alone, UV/sulfite ARPs rely on the addition of sulfite in the presence of UV light to remove bromate through three mechanisms including UV irradiation (as discussed above), sulfite reduction, and reduction via reactive radicals produced by the photolysis of sulfite by UV light. While several factors are shown to inhibit the removal of bromate including DO and humic acid, bromate removal rates documented in literature ranged from 60-61% for UV/sulfite processes with oxygen present and ≥86% in samples in the absence of oxygen at exposure times ranging from 30 minutes to 240 minutes. Conclusion: Bromate removal rates have been demonstrated through bench-scale studies at up to 47% using UV irradiation and ≥86% using UV/sulfite ARPs. Significant practical barriers to implementation of UV irradiance and/or UV/sulfite ARPs for reduction of bromate for SFPUC include lack of full-scale operational data on bromate
removal, long UV exposure times, high UV doses, and potential need to purge oxygen from ozonated water to achieve reliably high removal rates. Achieving the UV reactor exposure times and UV doses to reduce bromate to below the PHG would necessitate impractically high UV reactor capacity (in terms of volume) and power requirements, and thus prohibitive from a capital and operational cost perspective. 3.3 Anion Exchange Membranes and Resins Anion exchange membranes and anion exchange resins refer to media with fixed cationic groups (i.e., positively charged) that allow for the removal of anions from drinking water sources. Anion exchange membranes are semi-permeable membranes that block the passage of select cations (i.e., positively charged ions) retaining them on the feed side of the membrane while selectively allowing anions to pass through. Anion exchange resins are media that have cationic functional groups and allow the exchange of anions on the surface of the resin. Both technologies have been studied at the bench- and pilot-scale for the removal of bromate ions in drinking water applications. 3.3.a Anion Exchange Membranes A 2021 study evaluated and compared the removal of bromate using anion exchange membranes in a Donnan dialysis (DD) process and electrodialysis process (ED), respectively, using batch reactors. Using the DD process, a concentrated salt (NaCl) receiver stream was used to drive the exchange of bromate with chloride in the feed stream. Using the ED process, an electric current was applied across anion and cation exchange membranes to drive the separation of bromate and other anions (such as nitrate and bicarbonate) from the diluent stream. While both processes were highly effective at removing greater than 90% influent bromate concentrations, the study highlights the drawbacks of anion exchange membranes as both processes also require batch reaction times on the order of 1-2 hours and result in a concentrated bromate stream that requires further treatment or disposal. An estimated 99.1% removal is achieved using the ED process at an energy consumption rate of 0.34 watt-hours per liter (Wisniewski and Kabsch-Korbutowicz 2021). 3.3.b Anion Exchange Resin Mestri et. al. evaluated the removal of bromate by anion exchange resins using both fixed-bed (i.e., flow-through) and batch reactors. Results of the flow-through experiments using a 50 mg/L bromate feed solution demonstrated a maximum 200-minute time to breakthrough of bromate to the initial feed concentration in a 1.2 cm (5 gram) anion exchange resin column experiment fed at 70 mL/min. In this study, breakthrough was defined when the effluent bromate concentration was equal to 10% of the feed concentration (90% removal). While the study presents a mathematical model to predict breakthrough to account for flow channeling and asymmetric breakthrough behavior, the study notes difficulties in scaling up the results for full-scale applications.
Conclusion: Through bench-scale studies, anion exchange membranes were demonstrated to provide ≥99% removal of bromate at batch reaction times of 1-2 hours. Similarly, anion exchange resins were shown to provide ≥90% removal for up to 200 minutes. While not intended to be a comprehensive assessment, the experimental data in this section is presented to represent the scale at which bromate removal has been assessed in literature using anion exchange membranes and resins. For each technology, further testing at full scale or bench/pilot scale using representative drinking water matrices would be needed to reasonably scale results for future full-scale applications. 3.4 BAC Filters BAC filters reduce the concentration of contaminants through biological degradation, whereas typical granular activation carbon (GAC) filters remove target contaminant by surface adsorption. Several studies have noted that poor removal of bromate can be expected by GAC from natural waters due to the competition for active sites by dissolved organic carbon (DOC) [Siddiqui et al., 1994), (Miller et al., 1996)]. Conversely, BAC filtration has been shown to be an effective treatment strategy for bromate removal in natural waters, however, there are several drawbacks to this approach which present challenges for full scale implementation. For effective bromate removal with BAC, specific water quality conditions must exist. Kiristis et at. (2000) studied the impacts of variable water quality parameters, notably pH, DO, and nitrate, on biological bromate reduction with BAC in bench-scale studies using tap water and raw surface water samples. At an approximate 20-minute empty bed contact time (EBCT), the study found a 40% reduction in bromate at DO of 3.8 mg/L and 11% reduction at DO of 13.6 mg/L. At a higher EBCT of 51 minutes, the study found an 86% removal of bromate in the absence of nitrate and 49% removal at an influent nitrate level of 42.3 mg/L. These results suggest both DO and nitrate inhibit the biological reduction of bromate, as these constituents compete with bromate as high potential electron acceptors. To increase the demand for bromate as an electron acceptor (and thereby accelerating its reduction to bromide), tests were conducted with an added external carbon source (lactate and pyruvate) at a dose of 3.1 mg of carbon per liter, which yielded bromate removal to the detection limit (approximately 95% removal assuming removal to the DLR). A separate pilot scale ozone BAC study noted enhanced reduction of both nitrate and bromate while using methanol as an external electron donor source (J.P. Van der Hoek et al., 2024). Conclusion: Through bench-scale studies, the biological reduction of bromate and BAC filters was demonstrated at removal rates of 11% to 95% depending on the background water quality and operational conditions of the BAC filters. While the literature indicates somewhat promising bromate removal at ambient DO levels and excellent removal at higher DO levels with the addition of a supplemental carbon source based on bench-scale studies (i.e., electron donor source), the impacts to downstream treatment
processes (e.g., filtration, chlorination) from an external carbon source along with the monitoring requirements to prevent regrowth in the distribution system are unclear. Further full-scale testing would be required to validate these results. 3.5 Zero Valent Iron While typically employed in groundwater treatment for the removal of nitrate, ZVI has been investigated at the bench- and pilot-scale for the removal of bromate. Similar to activated ferrous iron addition, ZVI (Feº) can reduce bromate to bromide while zero valent iron is oxidized to Fe2+ and Fe3+. In packed bed (i.e., column test) experiments, bromate removal of 90% was demonstrated from a groundwater matrix at an EBCT of 20 minutes for up to 20 bed volumes, suggesting it may be feasible to design full-scale packed bed ZVI systems operated similar to GAC contactors for drinking water treatment applications (Westerhoff 2001). Similar, innovative technologies like zero valent aluminum (ZVAl) have been applied to the removal of bromate. Lin et al., (2016) demonstrated the near-complete removal of bromate from deionized water in a batch reactor at a pH of 3 with the addition of ZVAl powder. While not practical for drinking water treatment due to the extremely low pH, the study suggests powdered forms of ZVI or ZVAl could be applied in drinking water treatment, similar to the application of powdered activated carbon (PAC). Conclusion: In bench scale column tests using groundwater, bromate removal was demonstrated at an efficiency of 90% using ZVI in packed bed columns. With more innovative alternatives to ZVI, such as acid washed ZVAI, higher removal rates may be achieved. However, limited research has been conducted for ZVI and related technologies for removal of bromate in drinking water applications and there are currently no full-scale ZVI applications for drinking water. Extensive research would be required to make this a feasible alternative for SFPUC to meet PHG goals. 4 Summary of Treatment Efficacy A summary of bromate removal percentages is provided below for each treatment alternative, based on the maximum value referenced in literature. The estimated bromate concentration after treatment assuming the maximum value detected in SFPUC treated water of 5.9 µg/L is calculated.
Table 1. Summary Bromate Removal Percentages
Treatment Alternative Maximum Removal Percentage
Influent Bromate Concentration from Literature (µg/L)
Estimated Bromate Concentration After Treatment (µg/L)1 Ferrous Iron Addition 99% 50 0.06 UV Irradiation 47% 250 3.1 UV/sulfite ARPs ≥86% NA ≤0.83 Anion Exchange Membrane 99.1% 100 0.05 Anion Exchange Resin 90% 50,000 0.59 BAC 86% 20 0.83 ZVI 90% 1,279,000 0.59 ZVAI at pH 3 NA 10,000 <12 NA = Not available. 1Values in this column were calculated by applying the ‘Maximum Removal Percentage’ to the maximum bromate concentration between 2022 – 2024 (5.9 µg/L). 2Estimated bromate concentration after treatment is assumed to be less than the DLR. Of the treatment alternatives evaluated for bromate, ferrous iron addition, UV irradiation, and anion exchange membrane and/or anion exchange resin have demonstrated the maximum percent removal for bromate shown in Table 1 through pilot- and bench-scale studies. For select technologies, including ferrous iron addition and anion exchange membranes, the reported removal percentages from literature may be sufficient to achieve the PHG for bromate assuming the highest value measured at HTWTP within the past three years (Table 1), further testing using representative post-ozonation HTWTP water would be required to confirm these treatment efficiencies. Scaling these technologies from lab or bench-scale to full-scale is another significant uncertainty that would need to be addressed. 5 Preliminary Cost Estimate An assessment of the potential costs for achieving the bromate PHG builds on the evaluation of BATs and the highest documented removal rates. As noted in Section 3, the documented treatment performance is based on targeting the MCL and presented relative to the existing DLR, which is greater than the PHG concentration. These results were extrapolated in this TM to evaluate potential achievement of the PHG. Assigning costs to these theoretical treatment levels further compounds the extrapolation of the treatment. For these reasons, the costs presented herein should be considered highly speculative and uncertain.
Since many of the technologies discussed in this TM are still being developed as they are applied to bromate treatment, few cost estimates are available in literature. As such, cost estimates for similar treatment technologies were adapted from the most recent edition of Suggested Guidelines for Preparation of Required Reports on PHGs prepared by the Association of California Water Agencies (ACWA) in 2022. It should be noted that the referenced cost estimates provided in the 2022 ACWA PHG Guidelines were not primarily targeted for the removal of bromate. As such, the estimated annualized costs based on these values may be well below the actual costs to implement these technologies. To account for additional studies, treatment processes, reconfiguration of the existing HTWTP treatment train, and additional infrastructure needed to adapt each technology for removal of bromate, the following adjustments using uncertainty factors (UFs) were made: • An uncertainty factor of 1.5 (UF1) was applied to the total 2025 annualized cost for each of the treatment technologies given the lack of testing to achieve the PHG target. In addition, none of these technologies have been applied in a full-scale drinking water treatment application for bromate control. Additional testing, time, and investment will be required to match these treatment technologies with full-scale drinking water treatment. • For UV irradiation/UV sulfite ARPs, anion exchange resins, BAC, and ZVI, an additional cost factor of 1.5 (UF2) was applied since the estimated concentration after treatment did not meet the PHG based on the removal percentages presented in literature for each technology. • For BAC, an additional cost factor of 1.5 (UF3) was applied for uncertainties associated with using an external carbon source as references in section 3.4 to achieve sufficiently high removal rates to meet the PHG. • No ACWA cost estimates were available for ZVI, thus the ZVI cost estimates provided are based on a GAC cost estimate from the ACWA PHG guidelines given that similar infrastructure would likely be used (e.g., vessels/gravity beds). An additional 1.5 uncertainty factor (UF4) was applied to the 2025 annualized cost. • All costs from the 2022 ACWA PHG Guidelines were updated to reflect annualized costs using the February 2025 Engineering News Record (ENR) February 2025 Construction Cost Index of 13,766.3. • It was assumed that SFPUC would need to acquire a 2-acre site to locate the bromate treatment. The cost for land acquisition was assumed to be $10 million dollars per acre (statista.com) and annualized over a 30-year period. Speculative cost estimates were developed for each of the technologies discussed in this TM to bring bromate levels in SFPUC drinking water to below the PHG goal. Table 2 presents these preliminary and high-level cost estimates based on sizing each treatment technology for the peak capacity at HTWTP of 180 million gallons per day (MGD). Because bromate was only detected at HTWTP for the 2022 through 2024 PHG reporting period, the costs in Table 2 are sufficient for the 2025 PHG Report. However,
SFPUC is currently in the process of adding ozone treatment at SVWTP for control of taste and odor compounds from seasonal algae blooms and disinfection byproduct precursor material. While outside of the scope of the PHG Report for the current reporting period, supplementary cost estimates for the technologies examined in this TM are provided for the 160 MGD flows from SVWTP in Table 3. The speculative cost estimate for SVWTP bromate treatment assumes the same level of treatment used for achieving effluent bromate concentrations below the PHG at HTWTP. The cost estimates for SVWTP are based on the same 2022 ACWA cost estimates as provided for HTWTP and additional cost factors as described above.
Table 2. Aggregate Annualized Cost Estimate for Treatment Alternatives at HTWTP Treatment Alternative ACWA 2021 Annualized Cost ($/1000 gallons) Adjusted 2025 Annualized Cost ($/1000 gallons) Land Acquisition Annualized Cost ($/1000 gallons) Total 2025 Annualized Cost ($mil/year)1,2 Reference Project Notes Activated Ferrous Iron
6.935 7.869 0.010 776 February 28, 2013, Final Report Chromium Removal Research, City of Glendale, CA. 100-2000 gpm. Reduce Hexavalent Chromium to 1 ppb.
Average ACWA 2021 Annualized $/1000 gallons selected from range (1.91-11.96). UF1 applied to account for additional testing needed to apply this technology at full-scale. Total cost factor = UF1 = 1.5 is applied. UV Irradiation/UV Sulfite ARP
0.67 0.760 0.010 114
Carollo Engineers, estimate for VOC treatment (PCE) by UV Light, Ozone, Hydrogen Peroxide, O&M costs based on operation during 329 days/year at 10% downtime, 24 hr/day AOP operation, 1900 gpm capacity, Oct. 1994 UF1 applied to account for additional testing needed to apply this technology at full-scale. UF2 applied as the estimated concentration after treatment did not meet the PHG. Total cost factor = UF1 x UF2 = 2.25 is applied Anion Exchange Membrane/Resin
5.075 5.758 0.010 853
February 28, 2013, Final Report Chromium Removal Research, City of Glendale, CA. 100-2000 gpm. Reduce Hexavalent Chromium to 1 ppb.
Average ACWA 2021 Annualized $/1000 gallons selected from range (1.96-8.19). UF1 applied to account for additional testing needed to apply this technology at full-scale. UF2 applied as the estimated concentration after treatment did not meet the PHG. Total cost factor = UF1 x UF2 = 2.25 is applied BAC
2.71 3.075 0.010 684
Southern California Water Co. - actual data for "rented" GAC to remove VOCs (1,1-DCE), 1.5 mgd capacity facility, 1998 UF1 applied to account for additional testing needed to apply this technology at full-scale. UF2 applied as the estimated concentration after treatment did not meet the PHG. UF3 applied to account for unknown external carbon source addition and monitoring. Total cost factor = UF1 x UF2 x UF3 = 3.375 is applied. ZVI
2.71 3.075 0.010 684
Southern California Water Co. - actual data for "rented" GAC to remove VOCs (1,1-DCE), 1.5 mgd capacity facility, 1998 UF1 applied to account for additional testing needed to apply this technology at full-scale. UF2 applied as the estimated concentration after treatment did not meet the PHG. UF3 applied as no 2021 ACWA cost estimate for ZVI treatment was available and the cost estimate of a similar technology (GAC) was used. Total cost factor = UF1 x UF2 x UF4 = 3.375 is applied. 1Costs were adjusted from 2021 estimates provided using a ratio of the February 2025 Engineering News Record (ENR) Construction Cost Index (CCI) of 13,766 to the 2021 CCI of 12,133 (13,766 / 12,133 = 1.135) 2Cost based on treating peak HTWTP flow.
Table 3. Aggregate Annualized Cost Estimate for Treatment Alternatives at SVWTP Treatment Alternative ACWA 2021 Annualized Cost ($/1000 gallons) Adjusted 2025 Annualized Cost ($/1000 gallons) Land Acquisition Annualized Cost ($/1000 gallons) Total 2025 Annualized Cost ($mil/year)1,2 Reference Project Notes Activated Ferrous Iron
6.935 7.869 0.011 690
February 28, 2013, Final Report Chromium Removal Research, City of Glendale, CA. 100-2000 gpm. Reduce Hexavalent Chromium to 1 ppb.
Average ACWA 2021 Annualized $/1000 gallons selected from range (1.91-11.96). UF1 applied to account for additional testing needed to apply this technology at full-scale. Total cost factor = UF1 = 1.5 is applied. UV Irradiation/UV Sulfite ARP
0.67 0.760 0.011 101
Carollo Engineers, estimate for VOC treatment (PCE) by UV Light, Ozone, Hydrogen Peroxide, O&M costs based on operation during 329 days/year at 10% downtime, 24 hr/day AOP operation, 1900 gpm capacity, Oct. 1994 UF1 applied to account for additional testing needed to apply this technology at full-scale. UF2 applied as the estimated concentration after treatment did not meet the PHG. Total cost factor = UF1 x UF2 = 2.25 is applied Anion Exchange Membrane/Resin
5.075 5.758 0.011 758
February 28, 2013, Final Report Chromium Removal Research, City of Glendale, CA. 100-2000 gpm. Reduce Hexavalent Chromium to 1 ppb.
Average ACWA 2021 Annualized $/1000 gallons selected from range (1.96-8.19). UF1 applied to account for additional testing needed to apply this technology at full-scale. UF2 applied as the estimated concentration after treatment did not meet the PHG. Total cost factor = UF1 x UF2 = 2.25 is applied BAC
2.71 3.075 0.011 608
Southern California Water Co. - actual data for "rented" GAC to remove VOCs (1,1-DCE), 1.5 mgd capacity facility, 1998 UF1 applied to account for additional testing needed to apply this technology at full-scale. UF2 applied as the estimated concentration after treatment did not meet the PHG. UF3 applied to account for unknown external carbon source addition and monitoring. Total cost factor = UF1 x UF2 x UF3 = 3.375 is applied. ZVI
2.71 3.075 0.011 608
Southern California Water Co. - actual data for "rented" GAC to remove VOCs (1,1-DCE), 1.5 mgd capacity facility, 1998 UF1 applied to account for additional testing needed to apply this technology at full-scale. UF2 applied as the estimated concentration after treatment did not meet the PHG. UF3 applied as no 2021 ACWA cost estimate for ZVI treatment was available and the cost estimate of a similar technology (GAC) was used. Total cost factor = UF1 x UF2 x UF4 = 3.375 is applied. 1Costs were adjusted from 2021 estimates provided using a ratio of the February 2025 Engineering News Record (ENR) Construction Cost Index (CCI) of 13,766 to the 2021 CCI of 12,133 (13,766 / 12,133 = 1.135) 2Cost based on treating peak SVWTP flow
6 References Farkas, L. and Klein, F.S. (1948). On the photo-chemistry of same ions in solution, J. Chem. Phys. 16 (1948) 886. Gordon, G.; Gauw, R.; Emmert, G.; Walters, B.; and Bubnis, B. (2002). Chemical reduction methods for bromate ion removal. Journal / American Water Works Association, 94 (2), 91-98. Lin, K.A. and Lin, C.H. (2016). Simultaneous reductive and adsorptive removal of bromate from water using acid-washed zero-valent aluminum. Chemical Engineering Journal, 297 (2016) 19-25 Mestri, Safal; Dogan, Sedar; and Tizaoui, Chedly (2022): Bromate Removal from Water Using Ion Exchange Resin: Batch and Fixed Bed Column Performance, Ozone: Science & Engineering, DOI: 10.1080/01919512.2022.2114420 Miller, J.; Snoeyink, V.L.; and Kruithof, J. (1996). The Reduction of Bromate by Granular Activated Carbon in Distilled and Natural Waters. American Chemical Society. Siddiqui, M.S.; Amy, G.L.; and Mc Collum, L.J. (1996). Bromate destruction by UV irradiation and electric-arc discharge, Ozone: Sci. Eng., 18(3) (1996) 271-290. Siddiqui, M.; Amy, G.; Ozekin, K.; Zhai, W.Y.; and Westerhoff, P. (1994). Alternative strategies for removing bromate. J. Am. Water Works Ass., 86(10), 81–96. Siddiqui, M. S. ; Amy, G. ; and Rice, R. (1995). Bromate ion formation: a critical review, J. Amer. Water Works Assoc. 87 (1995) 58 – 70 Tammaro, M.; Salluzzo, A.; Patti, A.; Fiandra, V.; and Lancia, A. (2016). UV treatment to remove bromate formed by ozonation on groundwater. Influence of oxidation process on the removal efficiency, Journal of Environmental Chemical Engineering 4(3) (2016) Van der Hoek, J.P.; Deng, T.; Spit, T.; Luimstra, V.; de Kreuk, M.; and van Halem, D. (2024). Bromate removal in an ozone – granular activated carbon filtration process for organic micropollutants removal from wastewater. Journal of Water Processing Engineering, 58,104877 Westerhoff, P. and Johnson, P. (2001). A Zero valent Iron Packed-Bed Treatment Process. Water Research Project #2555 Wisniewski, J.A. and Kabsch-Korbutowicz, M. (2021). Removal of nitrate and bromate ions from water in processes with ion-exchange membranes. Department of Environmental Protection Engineering, Wroclaw University and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland. 2025 Public Health Goal Report San Francisco Water System Attachment E
Hexavalent Chromium Technical Assessment and Cost Estimate for 2025 Public Health Goal Report
City and County of San Francisco Public Utilities Commission San Francisco, CA Hexavalent Chromium Technical Assessment and Cost Estimate for 2025 Public Health Goal Report April 2025 Prepared for: San Francisco Public Utilities Commission
Technical Memorandum
San Francisco Public Utilities Commission
Draft Date: March 20, 2025
Final Date: April 28, 2025
Prepared For: San Francisco Public Utilities Commission (SFPUC), Water Quality Division
Eddy So, P.E.
Prepared By: Trussell Technologies, Inc.
Andrew Rudchenko
Teresa Venezia
Reviewers: Rhodes Trussell, Ph.D., P.E., BCEE
David Hokanson, Ph.D., P.E., BCEE
Emily Owens-Bennett, P.E., BCEE
Subject: Public Health Goal Report Hexavalent Chromium Technical Assessment
1 Introduction
The purpose of this Technical Memorandum (TM) is to provide an overview and assessment of Best Available Technologies (BATs) that may potentially remove Hexavalent Chromium (Cr-6) in the San Francisco Public Utilities Commission (SFPUC) drinking water to below the Public Health Goal (PHG) of 0.02 micrograms per liter (µg/L). The Cr-6 PHG was established by OEHHA in 2011. The State Water Resources Control Board (SWRCB) adopted a MCL of 10 µg/L along with a detection limit for the purposes of reporting (DLR) of 0.1 µg/L, both of which have been in effect since October 1, 2024.
During the current reporting period of 2022 through 2024, Cr-6 was detected at levels in excess of its PHG based on compliance monitoring data collected from SFPUC’s entry points to the distribution system. Very preliminary high-level cost estimates for select Cr-6 treatment alternatives are provided in support of SFPUC’s 2025 PHG Report; however, it is important to note that these estimates are based primarily on pilot- and demonstration-scale studies with very limited data from full scale applications of these treatment technologies. Moreover, the studies consider treatment to MCL and do not consider treatment to the much lower PHG, making the very preliminary cost estimates highly speculative.
An evaluation of Cr-6 BATs was provided in SFPUC’s 2019 PHG report, which referenced several treatment processes from the City of Glendale’s Hexavalent Chromium Removal Research Project (Glendale Project), most notably reduction, coagulation, filtration (RFC), weak base anion ion exchange (WBA), and strong base anion ion exchange (SBA), which are all designated as BATs to achieve MCL compliance by SWRCB Division of Drinking Water (DDW). PHGs, set by OEHHA, are often much lower than MCLs, so it is not always possible to determine from available information what treatment, if any, could reduce contaminant levels to the PHGs. BATs to reduce contaminant levels to the PHGs, for which limited information is available, are to be differentiated from BATs to achieve MCLs. Cost estimates to reduce contaminant levels to the PHGs for these treatment technologies could therefore be highly uncertain. As part of this effort, the performance efficiencies for these technologies relative to compliance with the MCL were examined from recent literature and extrapolated to estimate achievement of the PHG for Cr-6. Similarly, speculative preliminary cost estimates provided in the 2019 PHG report were revised to reflect any improvements in each technology’s performance. Treatment costs nationally and for California to meet varying potential Cr-6 MCLs were developed by Seidel et al. (2013). For California, Cr-6 occurrence data was largely based on DDW’s Water Quality Analysis Database with what is classified as a low maximum reporting limit (MRL) of 1 µg/L. Treatment technology evaluation was largely based on work in Glendale, CA, in which pilot- and demonstration-scale work was shown to effectively remove Cr-6 to <5 µg/L. For WBA, it was stated by Seidel et al (2013) that treatment to 2 µg/L has been demonstrated. For SBA, it was stated that, based on work in Glendale and on some full-scale applications, treatment to 1 µg/L has been documented. These levels are considerably higher than the PHG of 0.02 µg/L, making the costs to reduce concentrations to the PHG highly speculative. 2 Hexavalent Chromium Occurrence Cr-6 primarily enters the San Francisco Water System (SFWS) through the local groundwater well supply, which are blended with various treated surface water sources from the San Francisco Regional Water System (SFRWS) in the local SF reservoirs. The two local SF reservoirs include the 87-million-gallon (MG) Sunset Reservoir (SSR) and 31-MG Sutro Reservoir. The treated surface water supplies include the Hetch Hetchy (HH) supply, Harry Tracy Water Treatment Plant (HTWTP) effluent, and Sunol Valley Water Treatment Plant (SVWTP) effluent. A schematic of the SFWS including connection points with the SFRWS is provided in Figure 1.
Figure 1. Schematic of the SFWS Connection Points (red stars indicate proposed SFWS Cr-6 treatment locations) A summary of Cr-6 detections at SFPUC’s various compliance monitoring locations is provided in Table 1. In terms of SFWS supplies, between 2022-2024, Cr-6 was detected in five of the six raw groundwater sources at levels above the MCL. After blending with SFRWS supplies in the SSR, Cr-6 levels were detected at both SSR outlets at concentrations well below the MCL, but above the DLR and PHG. For the SFRWS supplies including HTWTP, SVWTP, and Alameda East (representative of HH supply), Cr-6 was detected above the PHG and DLR, yet much lower than the local SF GW wells. However, Cr-6 levels in the SFRWS were below the DLR at the representative points of entry (POEs) to the SFWS including the four Baden Pipelines: Crystal Springs
Pipeline #2- Baden, San Andreas Pipeline #2-Baden (SAPL2), San Andreas Pipeline #3-Baden (SAPL3), and Sunset Supply Pipeline (SSPL). Table 1. Summary of Maximum Cr-6 Detections at Compliance Monitoring Locations Between 2022-2024 Location Sample Type Maximum Cr-6 Concentration (µg/L) Date of Maximum Cr-6 Detection SSR (North) Outlet Treated Water 0.37 1/9/24 SSR (South) Outlet Treated Water 0.31 9/13/22 HTWTP Treated Water 0.27 8/10/22 SVWTP Treated Water 0.35 6/21/23 Alameda East Treated Water 0.22 8/10/22 Crystal Springs Pipeline #2-Baden Treated Water 0.04 (<DLR) 10/30/24 SAPL2 Treated Water 0.04 (<DLR) 10/30/24 SAPL3 Treated Water 0.04 (<DLR) 10/30/24 SSPL Treated Water 0.04 (<DLR) 10/30/24 SFGW-WSW Raw GW 26.9 1/14/22 SFGW-LMW Raw GW 9.76 1/11/22 SFGW-GGP Central Raw GW 27.1 1/11/22 SFGW-GGP North Raw GW 23.2 1/11/22 SFGW-SWW Raw GW 14.7 7/11/23 SFGW-SSW Raw GW 21.4 1/11/22 Per DDW guidance on compliance reporting, results below the DLR should be considered zero for calculation purposes. As such, to reduce Cr-6 levels to below the PHG in the SFWS, treatment is needed for the Lake Merced Well (LMW) and GGP/Sunset wellfields (after co-mingling of the five wells in the common header). An alternate to providing treatment of the GGP/sunset wells is to provide treatment after blending with SFRWS supplies at the SSR outlet. As shown in Figure 1, since water from the LMW has the potential to be delivered to customers prior to blending in the SSR, treatment at LMW is needed regardless of which treatment alternative is pursued (GGP/Sunset wellfields or SSR outlet). These treatment locations in the SFWS are marked with red stars in Figure 1. While the Cr-6 levels in the treated surface water supplies at Baden Valve Lot (the four POEs of the SFWS) were below the DLR, this was based on only one round of monitoring in 2024. Supplementary cost estimates are provided for the SFRWS supplies in this TM for future consideration given the Cr-6 detections above the DLR at the surface water treatment plant effluents. Potential treatment siting locations could include treatment of the East Bay Blend at the Sunol Valley Chloramination Facility (SVCF), representative of both SVWTP and HH supply, and HTWTP.
For the purposes of cost estimating, flow rates for each supply listed assume values from the 2019 PHG report. 3 Best Available Technologies (BAT) for Removal of Hexavalent Chromium The triennial PHG reporting must provide an estimate of the cost to reduce contaminants to the PHG. The cost estimates provided in this TM rely on evaluating removal using treatment technologies for Cr-6 established for achieving MCL compliance, rather than the non-enforceable PHG concentrations. The treatment costs were extrapolated to meet the PHG. It is important to note that the treatment technologies to reach the PHG level have not been defined and may not be available. For the purpose of this TM, the Cr-6 removal rates documented in the literature for achieving the MCL and/or DLR have been extrapolated to evaluate potential expected removal with respect to the PHG concentration. This approach is highly speculative as effectiveness of various technologies to achieve the PHG is unknown. Only treatment technologies that can remove a PHG contaminant are considered best available technologies to reduce concentrations to the PHG, thus dilution via blending of source waters is not considered. The following subsections provide an overview on recent literature for the BATs for removal of Cr-6. These include RCF and anion exchange, which were previously identified BATs in SFPUC’s 2019 PHG Report but are updated for this TM based on new innovations, where applicable. In addition, RO is considered as a BAT in the 2024 Cr-6 MCL regulation. However, the loss of water associated with the process, the lack of a suitable location for discharge of the RO concentrate, the potential requirement of an additional pass or passes of RO to treat to the PHG, and the likely need for pretreatment precluded further consideration of RO. 3.1 RCF RCF for the removal of Cr-6 in water is a process in which aqueous ferrous iron (Fe2+) is applied to reduce Cr-6 to trivalent chromium (Cr-3). To further reduce the resulting total chromium concentration in the finished water, Cr-3 is co-precipitated and/or adsorbed to iron hydroxide particles and removed via filtration. Excess ferrous iron not involved in the Cr-6 reduction/co-precipitation reaction can then be oxidized to iron hydroxide particles with ambient/introduced oxygen or sodium hypochlorite. RCF has been primarily examined for Cr-6 removal at the bench and pilot levels. The Glendale Project (Phase III, 2015) examined the impacts of various ferrous iron doses (or Fe:Cr-6 mass ratios), filtration methods including granular media filtration (GMF) and membrane filtration (MF), and excess iron oxidation methods on Cr-6 removal and operational performance (WRF 2015). As summarized in SFPUC’s 2019 PHG Report, removal efficiencies for Cr-6 from RCF using GMF and MF were both >99% with an influent Cr-6 concentration between 10-15 µg/L and final Cr-6 concentrations as low as 0.05 µg/L, but with an impractical reduction time of approximately 45 minutes required. At the demonstration scale, the Glendale Project utilized a range of ferrous iron doses of 2-3 mg/L, corresponding to Fe:Cr-6 ratios ranging from approximately 111 – 230 to 1. Other operational conditions used during the 2015 Glendale Project include a backwash frequency of 1 day and reduction time of 5-15 minutes. Through pilot scale RCF studies using expanded polystyrene filtration, Mahringer et al. (2020) concluded that ferrous doses up to an Fe:Cr-6 ratio of 155:1 was insufficient to remove Cr-6 to the same extent as Fe:Cr-6 ratio of 271:1, for which nearly complete Cr-6 removal was observed. While the polystyrene filtration media used in Mahringer’s 2020 study is not widely used at full scale, backwash frequencies during the study were 3 days. In a separate pilot study, Liang et al (2015) examined the impact of filter aid and polymer dosing to improve granular media filtration performance using RCF for Cr-6 removal. The pilot test showed a decrease in filter performance (i.e., longer filter ripening and higher rate of head loss accumulation) with the addition of filter aid; but the filter performance was improved with an alum dose of 10 mg/L, though filter run times were not extrapolated past 24 hours. In later pilot scale studies by Mahringer et al. (2024), RCF was tested using a biological granular filter acclimated with Fe2+ oxidizing bacteria. The test demonstrated that the Cr-6 reduction time could be greatly reduced compared to RCF with non-biologically acclimated filters to as low as 2.7 minutes while achieving ≥96% Cr-6 removal, with a final effluent concentration of 2 µg/L. This is attributed to significantly less iron-based sludge formation when excess ferrous iron that does not react with Cr-6 is oxidized by oxygen or chlorine upstream of the filtration step. RCF with biological filtration also eliminates the need for a chlorine addition step to oxidize excess ferrous iron, reducing operational costs. Conclusion: In general, recent literature on Cr-6 removal through RCF corroborates the findings of the Glendale Project, achieving high Cr-6 removal rates ≥96%. The Fe:Cr-6 ratio’s examined by Mahringer’s 2020 study are fairly consistent with those of the 2015 Glendale Project. Mahringer’s 2020 and 2024 studies suggest some operational optimization of the 2015 Glendale Project can be achieved, specifically with respect to reduction of contact time (to as low as 2.7 minutes) and backwash frequency (once per 3 days), at a treated water Cr-6 concentration of 2 µg/L. If applied to full scale, both of these factors primarily influence the footprint required to implement RCF as longer reduction time and higher backwash water volumes require larger tank sizing. The cost analysis paper by Seidel et al (2013) stated that the minimum feasible treatment target with RCF was 5 µg/L.
3.2 Anion Exchange Ion exchange is a sorption mechanism that occurs when ions in solution travel to a solid matrix carrying equal polarity. Anion exchange utilizes positively charged functional groups on the resins to facilitate removal of anions from water via exchange of an anion in the source water for an anion adhered to the surface of the resin. Anion exchange is one of the most highly recommended treatment approaches for removing Cr-6 from water. In fact, Cr-6 is mostly present in drinking water as an anion, in the form of chromate (CrO42-) or bichromate (HCrO4-). Both anions have been shown to be removed using either strong-base anion (SBA) or weak-base anion (WBA) exchange resins. 3.2.a SBA The mechanism of removal of Cr-6 with SBA involves the exchange of the Cr-6 ion from the source water to replace chloride ions on the surface of the SBA resin. The first major studies examining pilot-scale SBA for Cr-6 removal from drinking water to levels below the MCL were included in the Glendale Project (Phase II, 2005). The full-scale implementation of SBA exchange systems were operated by Coachella Valley Water District (CVWD). CVWD tested three full-scale ion exchange treatment plants (up to 4,000 gpm) using SBA resin and effectively removed arsenic and Cr-6. Najm et al. (2014) conducted bench-scale studies with SBA systems and demonstrated Cr-6 removal to an effluent concentration as low as 0.1 µg/L. In a separate study, Pacific Gas and Electric (PG&E) provided treatment for Hinkley, Ca, using single-pass SBA point of entry systems and demonstrated treatment to below 0.06 µg/L as described by Parks et al (2017). The PG&E study showed no major difference in removal performances for different water qualities but showed impact on pretreatment costs and disposal cost depending on varying influent Cr-6 and sulfate concentrations. SBA resins have generally been implemented by utilities for the removal of nitrate, arsenic, perchlorate and other groundwater contaminants. Cr-6 treatment goals down to 1 μg/L have been documented at both pilot-scale (McGuire et al, 2007) and existing full-scale treatment systems for the removal of other contaminants. The anionic selectivity of SBA resins is as follows, CrO4 2- > SO4 2- > HAsO4 2- > NO3- > HCO3- > Cl- > F- > OH making them an ideal choice for Cr-6 removal. However, the presence of competing anions, such as sulfate, impact resin bed volumes (BVs) before breakthrough. Generally, SBA resins are easier to use for water with lower sulfate levels (< 50 mg/L) because they will not require onsite regeneration as often. In this case, resins can be more efficiently used for Cr-6 removal. For water with higher levels of sulfate (>50 mg/L), onsite regeneration with lead-lag staggered operation will be required. These resins are strongly basic and their functional group stays ionized over a large range of pH. As such, they are effective at broad ranges of pH and do not require pH suppressant or adjustment (Clifford, 1999). SBA resins, such as IRA 400 and 900, have been shown to strongly bind to Cr-6 and achieve treatment goals after 6 minutes contact time. (Rafati et al. 2010; Pratima et al. 2018). Purolite A-400, another SBA resin, also showed excellent removal of Cr-6, removing approximately 98% of the initial concentration at a pH level of 7.4. Parks et al, (2017) bench-tested Cr-6 removal with SBA resins, specifically Purolite A600E/9149 and ResinTech SBG1, at an empty bed contact time of 2 minutes with a Cr-6 spiked concentration of 100 µg/L. Breakthrough, defined as Cr-6 > 8 µg/L in treated water, was observed as soon as 2,500 BVs for waters with high sulfate levels (around 150 mg/L), and up to 6,000 BVs for waters with sulfate levels of 60 mg/L SBA systems are generally operated in a lead-lag configuration and resins are regenerated on site after exhaustion using a salt solution. Since the salt waste stream also contain Cr-6, disposal of the used salt solution, may be challenging for inland sites or States with stringent restrictions, such as California, where the waste would need to be treated and disposed as a solid waste and a nonhazardous liquid waste. All of the SBA studies referenced are for drinking water applications targeting a fraction of the MCL and demonstrating removal no lower than to the DLR. The effectiveness of the technologies treating to the PHG is unknown and the much lower treatment target will increase changeout frequency, require much higher contact times, and require much larger footprint to house a much larger number of vessels, all at much greater cost. 3.2.b WBA The mechanism of Cr-6 removal by WBA is not typical and consists of an exchange of chromate ion with chloride ion and reduction of Cr-6 to Cr-3 on the resin surface. WBA resins have been extensively evaluated in studies conducted by the City of Glendale CA, the City of Burbank CA, the City of San Fernando CA and other agencies. The Glendale Project demonstrated Cr-6 removal to below 1 µg/L (Phase III, 2014). Glendale pilot testing was followed by construction of a 425-gpm demonstration-scale WBA system. Testing for this facility demonstrated one year for breakthrough at a 5 µg/L treatment target. The breakthrough time for a treatment target of the PHG of 0.02 µg/L would be expectedly much shorter, necessitating additional ion exchange vessels and a longer contact time at much greater cost. Parks et al (2017) demonstrated Cr-6 breakthrough at 7,000 BVs of WBA (Purolite S106) media with an initial spiked Cr-6 concentration of 100 µg/L. In contrast with SBA resins, WBA resins require pH to be depressed to 6.0 or less for treatment optimization (Blute et al, 2013; McGuire et al, 2007). Post treatment adjustment to a more alkaline pH will be also required to protect pipe material in the distribution system resulting in higher O&M cost compared to SBA resins.
WBA systems are operated in a lead-lag configuration and resins are not regenerated but replaced after exhaustion and disposed as solid waste. Unlike SBA resins, WBA resins are typically not regenerated due to the different mechanism for the Cr-6 to be removed by the WBA media involving a chemical reaction from Cr-6 to Cr-3 rather than a typical exchange of anions. Since WBA resins can also remove uranium, if high levels of uranium are present in the treated water, spent resin could be classified as radioactive or hazardous waste, requiring costly disposal options. Conclusion: In general, the literature highlights that while both WBA and SBA can be effective at achieving values below the MCL for Cr-6, no studies specifically looked at reliably achieving removal to the PHG. In addition, the performance of SBA and WBA resins is highly dependent on water quality. As such, testing using SFPUC’s surface water and groundwater sources would be required for each individual site to confirm a) the actual removal and comparison with the PHG and b) the resin replacement rate, pH target, and other treatment optimizations that would influence the cost and implementation of these treatment technologies. The cost analysis paper by Seidel et al (2013) stated that the minimum feasible treatment target with WBA was 2 µg/L and with SBA was 1 µg/L. 4 Summary of Treatment Efficacy This TM examined the treatment efficacy of RCF and anion exchange for removal of Cr-6 in recent literature, expanding on the data from the Glendale Project as referenced by the 2019 PHG Report. A summary of the revised treatment efficacy for each unit process is provided in Table 2 below based on the highest achieving treatment efficacy examined in literature for each process (see columns 3 and 4 in Table 2). As mentioned above, the minimum treatment targets for each technology were identified in Seidel et al (2013) and are more reliable for the practical implementation of each technology at the full scale (see column 5 of Table 2). These concentrations will be used in the preliminary cost estimate.
Table 2. Summary Cr-6 Treatment Efficacy
Treatment Technology Technology Variation Pilot and Demonstration Studies Seidel et al (2013) Influent Concentration Range (µg/L) Effluent Concentration Range (µg/L) Minimum Treatment Target (µg/L) RCF Granular Media Filtration 10 - 15 0.05 - 0.13 ≤5 Biofiltration 5 – 50 0.3 – 2.0 Anion Exchange - SBA Purolite A600E/9149 20-30 <0.02 ≤1 Anion Exchange - WBA Purolite S106 Dow PWA7 30-40 <0.02 ≤2 5 Preliminary Cost Estimate An assessment of the potential costs for achieving the Cr-6 PHG builds on the evaluation of BATs and the minimum treatment targets shown in Table 3 based on Seidel et al. (2013). As noted in Section 3, the documented treatment performance is based on targeting the MCL and presented relative to the existing DLR, which is greater than the PHG concentration. These results were extrapolated to evaluate potential achievement of the PHG. Assigning costs to these theoretical treatment levels further compounds the extrapolation of the treatment. For these reasons, the costs presented should be considered highly speculative and uncertain. Revised speculative cost estimates to bring Cr-6 levels to below the PHG are provided in this section for anion exchange using SBA and WBA, utilizing California-specific cost estimate equations adapted from the Glendale Project (2012) and Seidel et al (2013). RCF was not included in the cost analysis as the effluent concentration range provided from literature was significantly higher than the PHG, as well as the effluent concentrations for WBA and SBA from literature (Table 2). The cost estimate equations developed by Seidel et al are based on engineering estimates and installed costs of existing treatment systems (including the Glendale Project) targeting the MCL or values above both the current DLR and PHG. The equations are adaptable to variable Cr-6 influent concentrations and are valid for a system size between 10 – 4000 gpm. While the equations do not specify an influent Cr-6 concentration, they are tailored to various Cr-6 effluent goals specific to the capital and O&M cost equations for each technology. The capital and O&M cost equations adapted from Seidel et al are provided in Table 3 below. If available, the assumed treatment goal is provided next to each equation. Table 3. Capital and O&M Cost Equations Adapted from Seidel et al (2013) Technology Capital Cost (National), $/year1 O&M Cost (California), $/year1 Anion Exchange - WBA Cost = 310,253 x Q0.4030 Goal = 2 ppb; Cost = 135,205 + 627.3 x Q Anion Exchange - SBA Goal ≤ 1 ppb; Cost = 183,992 +1,194 x Q Goal =1 ppb; Cost = 183,542 + 1,298 x Q 1Capital and O&M equations valid over a flow range of 10-4000 gpm and includes treatment/disposal of residual waste streams. Q = Design or Average Flow Rate (gpm). Goal = effluent goal Treatment goals for the equations in Table 3 range from 1 – 2 µg/L, whereas the PHG for Cr-6 is 0.02 µg/L. To account for additional studies, potential supplemental treatment processes, and additional infrastructure needed to adapt each technology for removal of Cr-6 to the PHG, the following adjustments/assumptions were made to the capital and O&M costs for WBA and SBA: • Flow Assumption: To account for the difference in flow between the valid flow range for the equations (10-4000 gpm) and capacities of the SFWS and SFRWS supply waters described in this TM, preliminary costs were calculated for a 2000 gpm system, then scaled linearly for the capacity of each source water. • Capital Cost Adjustment: An uncertainty factor of 1.5 was applied to the total 2025 annualized capital costs for each treatment technology to account for unknown challenges associated with treating to the PHG level, including additional bench/pilot testing, reconfiguration of the existing treatment systems, increased monitoring, etc. • O&M Cost Adjustment for WBA: The O&M cost increases significantly with decreasing treatment goals because of more frequent resin replacement. The O&M cost equation for 0.02 µg/L effluent treatment goal was adjusted as shown in Appendix of this memorandum. • O&M Cost Assumption for SBA: O&M costs for SBA are independent of the effluent goal and therefore no adjustment to the Seidel et al equation was made to account for lower treatment goal. • Adjustment for Inflation: To adjust capital and O&M costs from 2013 to 2025 values, the ratio of the Engineering News Record (ENR) Construction Cost Index (CCI) between 2025 and 2013 was applied (e.g., 13,766 / 9668 = 1.42). • Assumption for Land Acquisition: It was assumed that SFPUC would need to acquire a 2-acre site to locate the Cr-6 treatment. The cost for land acquisition was assumed to be $10 million dollars per acre (statista.com) and annualized over a 30-year period. This annualized cost was added to the total 2025 annualized capital cost for each treatment technology. Speculative annualized 2025 capital and O&M costs for anion exchange-WBA and anion exchange-SBA are provided in Tables 4 and 5 (respectively). Primary and supplementary costs are presented below to add treatment targeting Cr-6 at the PHG. The local sources to the SFWS are considered primary for the purpose of Cr-6 removal, whereas the treated surface water supplies are considered supplementary in this cost evaluation due to the non-detect Cr-6 at the four points of entry at Baden Valve Lot. • Primary cost estimates for SFWS supplies with monitoring values above the DLR (Table 1) a. Sunset Reservoir Outlet b. Lake Merced Well c. Consolidated treatment for the five wells from the GGP/Sunset Well Field prior to entry into Sunset Reservoir • Supplementary cost estimates for SFRWS supplies with current monitoring values above the DLR o Consolidated treatment of the East Bay Blend at the SVCF o HTWTP Although the monitoring results from the four Baden pipeline points of entry to the SFWS (Table 1) indicated that the levels of Cr-6 were less than the DLR, implementation of treatment at the supplementary locations can allow for more direct influence of individual supplies that were impacted by Cr-6 levels measured above the DLR in the SFRWS. For these reasons, if achieving the PHG is prioritized, further study of these supplementary treatment locations could be considered to maximize the impact of the treatment to the SFWS. Overall, the speculative cost estimate for adding WBA treatment is of a similar order of magnitude as what was presented in the 2019 PHG report. Unsurprisingly, the speculative cost estimate for WBA is significantly higher than that of SBA given the challenges associated with WBA for this specific application (e.g., single use resin, shorter bed life, higher impact from background water quality, pH adjustment required before and after WBA treatment). Given the significant cost to treat Cr-6 and considering that current levels are well below the current MCL (after blending), treating Cr-6 to PHG levels does not appear to be warranted. As highlighted in this TM, many of the technologies discussed in this TM are still being developed as they are applied to Cr-6 treatment, few cost estimates are available in literature, and potentially significant site-specific testing would be needed to account for the difference in treatment targets between the MCL and the PHG.
Table 4. Aggregate Annualized Cost Estimate for Anion Exchange-WBA Treatment Priority Source Water Maximum Flow
Rate (mgd)
2013 Annualized
Capital Cost
($mil/year)
2013 Annualized
O&M Cost
($mil/year)
Land Acquisition
($mil/year)
2025 Adjusted
Annualized Capital Cost
($mil/year)1,2
2025 Adjusted
Annualized O&M Cost
($mil/year)1,3
Primary Sunset Reservoir Outlet 19 44.2 30.4 0.667 95 43.2 Lake Merced Well 0.864 2.0 1.4 0.667 4.9 2.0
GGP/Sunset Wellfield 3.96 9.1 6.3 0.667 20 9.0
Supplementary East Bay Blend 475 1095 759 0.667 2339 1081 HTWTP 180 415 288 0.667 887 410
1Costs were adjusted from 2013 estimates using ENR CCI ratio between 2025 and 2013 of 13,766 / 9668. 2Capital costs were adjusted by an uncertainty factor of 1.5. 3WBA O&M costs were adjusted as described above. Detailed information on the adjustment methodology is shown in the Appendix.
Table 5. Aggregate Annualized Cost Estimate for Anion Exchange-SBA Treatment Priority Source Water Maximum Flow Rate
(mgd)
2013 Annualized
Capital Cost
($mil/year)
2013 Annualized
O&M Cost
($mil/year)
Land Acquisition
($mil/year)
2025 Adjusted Annualized
Capital Cost ($mil/year)1,2
2025 Adjusted
Annualized O&M
Cost
($mil/year)1
Primary Sunset Reservoir Outlet 19 17.1 18.3 0.667 37 26.1 Lake Merced Well 0.864 0.8 0.8 0.667 2.3 1.2
GGP/Sunset Wellfield 3.96 3.5 3.8 0.667 8.2 5.4
Supplementary East Bay Blend 475 424 458 0.667 907 653
HTWTP 180 161 174 0.667 344 247
1Costs were adjusted from 2013 estimates using ENR CCI ratio between 2025 and 2013 of 13,766 / 9668. 2Capital costs were adjusted by an uncertainty factor of 1.5. 6 References Blute, N.; Wu, X.; Cron, C.; Fong, L.; Froelich, D.; Abueg, R. (2015b). Microfiltration in the RCF Process for Hexavalent Chromium Removal from Drinking Water. Water Research Foundation: Web Report #4365. Blute, N., X. Wu, K. Porter, G. Imamura, and M. J. McGuire. 2013. Hexavalent Chromium Removal Research Project Report to The California Department of Public Health. Los Angeles, CA: Hazen and Sawyer, and Arcadis U.S. Inc/Malcolm Pirnie. Clifford, D. A. 1999. “Ion Exchange and Inorganic Adsorption.” In Water Quality and Treatment: A Handbook of Community Water Supplies, Edited by R.D. Letterman, New York: McGraw Hill. Hazen and Sawyer; Arcadis U.S./Malcolm Pirnie. (2013). Hexavalent Chromium Removal Research Project Report to the California Department of Public Health. Liang, S. and Maceiko, S.M. (2015). Hexavalent Chromium Removal Through Conventional Filtration Treatment Processes. Journal AWWA Vol. 7 Issue 5. Mahringer, D., S. Zerelli, U. Dippon, A.S. Ruhl. (2020). Pilot scale hexavalent chromium removal with reduction, coagulation, filtration and biological iron oxidation. Separation and Purification Technology 253 117478. Mahringer, D., M. Lutz, M. Klumbies, S. Pabst, A.S. Ruhl. (2024). Reduction, coagulation and biotic filtration (RCbF) for Cr(VI) groundwater remediation – A case study. Journal of Water Processing Engineering 65 105867. McGuire, M. J., N. K. Blute, G. Qin, P. Kavounas, D. Froelich, and L. Fong. 2007. Hexavalent Chromium Removal Using Anion Exchange and Reduction with Coagulation and Filtration. Project #3167. Denver Colo.: AwwaRF. Najm, I., N. P. Brown, E. Seo, B. Gallagher, K. Gramith, N. Blute, X. Wu, M. Yoo, S. Liang, S. Maceiko, S. Kader, and J. Lowry. 2014. Impact of Water Quality on Hexavalent Chromium Removal Efficiency and Cost. Project #4450. Denver, Colo.: Water Research Foundation. Parks, J.L.; Mantha, A.; Edwards, M.; Kommineni, S.; Shim, Y.; Porter, K.; Imamura, G. (2017). Bench-Scale Evaluation of Alternative Cr(VI) Removal Options for Small Systems. Water Research Foundation: Web Report #4561. Pratima M, Ghosh A, Ramamurthy Y et al (2018) Removal of hexavalent chromium from mine effluents by ion exchange resins-comparative study of Amberlite IRA 400 and IRA 900. Russ J Non-Ferrous Met 59:533–542.
Rafati L, Mahvi AH, Asgari AR, Hosseini SS (2010) Removal of chromium (VI) from aqueous solutions using Lewatit FO36 nano ion exchange resin. Int J Environ Sci Tech 7:147–156 Seidel, C.J. I.N. Najm, N.K. Blute, C.J. Corwin, X. Wu. (2013). National and California treatment costs to comply with potential hexavalent chromium MCLs. Journal AWW]A Vol. 105 Issue 6, pages E320-E336.
APPENDIX Cr-6 Treatment Cost Calculation O&M Costs
Cost Adjustment for a lower effluent goal (0.02µg/L):cost ($/year) = 2E+06*(Treatment goal µg/L)^-0.213 Cost Adjustment for higher flow rate:Cost calculated normalizing by 2000 gpm flow and scaled linearly for each water supply Cost Adjustment for inflation:1.4239ENR CCI ratio of the 2025index/2013index Assumptions:WBA O&M cost is dependent on the treated water Cr-6 goal because resin replacement increases significantly with decreasing treatment goals.SBA O&M cost is indipendent of the treated water Cr-6 goal. O&M cost equations are applicable to sytem with a capacity between 10-4000 gpm2000 gpm is assumed to calculate an initial cost used to determine the treatment goal equation Capital Costs