Water & Wastewater Study Material

CA SWRCB T5 Exam Dashboard

Last Updated — August 2026

About the T5 Exam

The T5 exam is arguably California's most unique water or wastewater exam. Unlike the other exams, which are written and follow the standard true/false, multiple choice, and math format, the T5 exam is a 30-minute oral interview.

Candidates are tasked with placing themselves into varying operational, emergency, or management scenarios and detailing to the panel their response. The exam is six questions in total: two regulatory, two utility management and emergency, and two operational (see the T5 Examination Description for the full breakdown). Candidates must prove to the panel that they can serve as Chief Operator by:

Understanding the regulations that drive treatment plant processes
Understanding how to monitor, troubleshoot, and correct treatment systems within a plant
Understanding emergency operations as they relate to safety and public health
Understanding how to manage personnel, including disciplinary processes

For a candidate, understanding the rules, requirements, and practices that define a Chief Operator is important, but more important is the candidate's ability to navigate a given question and provide a complete, satisfactory answer. To that end, this study guide leans heavily on the REACT lens:

R-Recognize the Issue
E-Ensure Public Health
A-Act to Address
C-Communicate Clearly
T-Transform for Prevention

By approaching a question from the REACT angle, a candidate can naturally navigate the entirety of the scenario and create a thorough answer.

While the REACT lens is helpful, the successful candidate will drill the material not only by studying, but by recording themselves reciting their answer. THAT is the exam. Taking the knowledge and experience you have, placing yourself in a fictitious plant with processes you may have no personal experience with, and verbally describing "how do you respond?" It is important that you incorporate this practice into your study habits.

How it's organized

Study Guides — one page per rule or topic area containing purpose, rule evolution, key numbers (MCLs/MCLGs/MRDLs), monitoring & compliance mechanics, notification tiers, and California-specific requirements where they diverge from the federal rule. Listed alphabetically.
Study Tools
- Sample Exam Questions: scenario-based, framed around the REACT and CARES lenses
- Flash Cards: quick recall, tracks right/wrong and lets you filter by category or missed cards
- Scripts: Audio-style study scripts that walk through the exam rules by topic in plain, spoken language

How to use it

Click any Study Guide in the sidebar to jump straight to that rule's page.
Use the Flash Cards deck to drill recall. Track accuracy and filter by "missed only" or by category for targeted review.
Use Sample Exam Questions to rehearse verbal answers using the REACT (operations) and CARES (management) lenses.
Use the Scripts to create strong memory tools for passive studying.
Click "CA SWRCB T5 Exam Dashboard" at the top of the sidebar anytime to return to this page.
Switch between the Dark and Light buttons under the title anytime.

Source material

T5 Examination Description
Drinking Water-Related Regulations (Aug 2026)
40 CFR - Part 141
EPA Quick Reference Guides
National Primary Drinking Water Regulations
The Microbial Toolbox
CA Cryptosporidium Action Plan (April 2019)
Filter Backwash Rule Technical Guidance Manual
Lead and Copper Rule Improvements
CA PFAS Information
Upcoming CA Regulations
WaterWisePro — This dashboard was heavily influenced by Steve's T5 prep course. I highly encourage taking it.

Safe Drinking Water Act

The Safe Drinking Water Act (SDWA) is a federal law that protects the nation's public drinking water. It lets the U.S. Environmental Protection Agency (EPA) set national, science-based health standards for drinking water, and made those standards legally enforceable. First established in 1974, the SDWA has been amended 7 times to ensure safe drinking water for all as our communities grow and evolve.

What the Act Does

Established the National Primary Drinking Water Regulations (NPDWRs). Each one sets a maximum contaminant level (MCL) or a required treatment technique for a contaminant.
- The Drinking Water Standards page explains how an MCLG, an MCL, and a treatment technique differ.
Makes meeting the NPDWRs enforceable. These are legal limits, not guidelines.
Allows states to take the lead. A state can hold primacy if its rules are at least as strict as the federal ones, and can and will enforce them.
Requires public water systems meet the NPDWRs.
Requires public communication and transparency through monitoring and reporting schedules, the annual Consumer Confidence Report, and public notification when something goes wrong.

Who enforces it in California

California holds primacy and enforces the SDWA through the State Water Resources Control Board's Division of Drinking Water. California has its own Safe Drinking Water Act, which lives in the California Health and Safety Code. The laws DDW enforces are in Title 22 of the California Code of Regulations. Because California has primacy, Title 22 is as strict as the federal rules, and on several contaminants it is stricter.

How it affects your treatment plant

DDW issues a Water Supply Permit that lets your treatment plant and distribution system operate. Operating outside it is a core violation.
Every MCL, disinfectant limit, and treatment technique traces back to the SDWA.
Your monitoring and reporting requirements are established via the Standardized Monitoring Framework.
DDW performs Sanitary Surveys on your system and expects complete, current records.
Issuance of the annual Consumer Confidence Report and public notification when there is a health risk or violation.
Citations, compliance orders, and penalties for failure to maintain public health.
The SDWA requires qualified, certified operators to run the plant. The entire reason for your profession and the T5 certification you seek is rooted in this act.

Chief Operator lens

The SDWA is why every limit and every report on my desk exists.
EPA sets the national floor. California holds primacy and runs the program through DDW. Title 22 is the rulebook I follow, and it is at least as strict as federal.
It reaches my permit, my MCLs and treatment techniques, my monitoring and reporting, my operator certification, and my duty to notify customers and regulators.

Stage 1 & Stage 2 DBP Rules

Purpose

Improve public health protection by reducing exposure to disinfection byproducts. Some disinfectants and disinfection byproducts (DBPs) have been shown to cause cancer and reproductive effects in lab animals and suggested bladder cancer and reproductive effects in humans.

How this rule evolved

The Stage 1 Disinfection Byproducts (DBP) Rule (1998) set the DBP MCLs and applied only to public water systems that add a disinfectant other than UV light:

TTHM and HAA5 MCLs, measured as a system-wide running annual average (RAA)
MCLs for bromate (ozone plants) and chlorite (chlorine dioxide plants)
MRDLs for chlorine, chloramines, and chlorine dioxide
A precursor TOC-removal treatment technique

The Stage 2 DBP Rule (2006) kept the same MCL values but changed how and where compliance is proven:

TTHM/HAA5 compliance moved to a locational running annual average (LRAA) at each monitoring site, so a single hot spot can no longer hide behind a system-wide average
Monitoring locations set by an Initial Distribution System Evaluation (IDSE) to find where DBPs actually peak
Added Operational Evaluation Levels (OELs) to catch a rising trend early
Extended DBP requirements to consecutive systems that purchase water from a system that adds a disinfectant other than UV light

Paired with LT2

Paired with LT2: Stage 2 was issued alongside the Long Term 2 Enhanced Surface Water Treatment Rule (LT2) to address two risks at once. Stage 2 lowers disinfection byproduct formation. A system could pursue that by cutting disinfection doses, which would weaken pathogen protection. LT2 is the counterweight. Disinfection profiling and benchmarking must clear any significant change to disinfection practice before it can proceed.

Regulated contaminants

Contaminant	MCL	Compliance basis	Monitoring (freq · location)	Applies to
Total Trihalomethanes (TTHM)	0.080 mg/L	LRAA at each monitoring location (Stage 2)	Quarterly; locations by system type & population*	All disinfecting systems
Haloacetic Acids (HAA5)	0.060 mg/L	LRAA at each monitoring location (Stage 2)	Quarterly; locations by system type & population*	All disinfecting systems
Bromate	0.010 mg/L	RAA	Monthly · 1 at entry point	Plants using ozone
Chlorite	1.0 mg/L	Daily / follow-up monitoring	Daily at entry point; monthly (3 sites) in distribution	Plants using chlorine dioxide

*Routine TTHM/HAA5 monitoring frequency and number of locations are dictated by system type (Subpart H / surface water vs. ground water) and population served. Subpart H systems monitor more frequently and at more locations than ground water systems of the same size; the smallest systems monitor annually, larger systems quarterly.

Regulated disinfectants

Disinfectant	MRDL	Compliance basis	Monitoring (freq · location)	Applies to
Chlorine	4.0 mg/L (as Cl₂)	RAA	Same location & frequency as coliform (RTCR) sampling	All disinfecting systems
Chloramines	4.0 mg/L (as Cl₂)	RAA	Same location & frequency as coliform (RTCR) sampling	All disinfecting systems
Chlorine dioxide	0.8 mg/L	Daily / follow-up monitoring	Daily · 1 at entry point	Plants using chlorine dioxide

Chlorine and chloramine RAA has two steps: the residual readings taken at each coliform site are first averaged by month, then those monthly averages feed the running annual average, computed quarterly. Chlorine dioxide is not averaged — it is judged on daily entry-point samples.

Pathogen Risk > MRDL Limits

The MRDL is a chronic-exposure limit. When there is an acute microbial threat, protecting public health comes first. A system may raise the chlorine or chloramine (not chlorine dioxide) residual above the MRDL to protect public health and address specific microbial contamination problems, such as a distribution line break, a storm run-off event, a source water contamination event, a natural disaster, or a cross-connection event. Systems must notify the State Water Board immediately when doing so.

Running Annual Average (RAA) & Locational Running Annual Average (LRAA)

RAA — averaged system-wide across all monitoring sites.
LRAA — averaged per location.

RAA / LRAA = (Q₋₃ + Q₋₂ + Q₋₁ + Q₀) ÷ 4

Averaged over four consecutive quarters. As each new quarter comes in, the oldest falls off.

A violation occurs when the RAA/LRAA exceeds the MCL/MRDL. A single quarter's result high enough to pull the average over the limit is itself a violation.

Operational Evaluation Level (OEL)

The purpose of the OEL is to detect a rising TTHM or HAA5 level before an MCL violation occurs.

OEL = ((Q₋₂ + Q₋₁) + (Q₀ × 2)) ÷ 4

The OEL is calculated at the same time as the LRAA but only includes the three most recent quarters of data. The current quarter is double-weighted so a rising trend trips the OEL early.

The OEL is exceeded if its value is greater than the TTHM or HAA5 MCL. This is an operational trigger, not an MCL violation. If an OEL is exceeded, the system must:

Conduct an operational evaluation by examining the treatment & distribution practices contributing to TTHM/HAA5 formation, and identifying steps to minimize future exceedances.
Submit a written report to the state no later than 90 days after being notified of the results that caused the exceedance.
Keep a copy of the report and make it publicly available on request.

Enhanced coagulation — required TOC removal (%)

Systems using conventional filtration must remove the specified percentages of TOC as outlined in the table below, unless they meet alternative criteria. Softening systems must meet the removal requirements for source alkalinity > 120 mg/L.

Alkalinity drives how much TOC removal the rule requires because it controls how easily a system can reach the pH where coagulants perform best. Common coagulants like ferric and alum work most effectively at lower pH. Alkalinity buffers pH, so low-alkalinity water reaches that effective range readily and higher TOC removal is both achievable and required. High-alkalinity water resists the pH drop and would need far more coagulant to get there, so the rule allows lower removal. High-alkalinity, hard-water systems often use enhanced softening instead, which removes TOC by co-precipitation at higher pH.

Source TOC (mg/L)	Alk 0–60	Alk >60–120	Alk >120
> 2.0 – 4.0	35.0%	25.0%	15.0%
> 4.0 – 8.0	45.0%	35.0%	25.0%
> 8.0	50.0%	40.0%	30.0%

Alkalinity in mg/L as CaCO₃.

Controlling TTHM & HAA5 — treatment techniques

DBPs form when chlorine reacts with natural organic matter (TOC). Controlling DBP formation can be achieved via the methods described in the table below.

Strategy	How it's done	Where	Targets
Remove TOC precursors	Enhanced coagulation; enhanced softening; granular activated carbon (GAC10/GAC20); nanofiltration (≤ 1000 Dalton cutoff)	Plant	Both
Manage the disinfectant	Optimize chlorine dose; move chlorination point downstream; convert residual to chloramines (forms far less TTHM/HAA5)	Plant	Both
Reduce residence time / water age	Improved distribution & storage-tank management: tank turnover, level cycling, systematic / unidirectional flushing, looping dead-ends, right-sizing mains	Distribution	Both
Aeration / air stripping	Spray or packed-tower aeration strips formed TTHMs after they develop. Little effect on HAA5 (non-volatile).	Both	TTHM only

How pH acts on TTHM/HAA5

pH steers which byproduct forms as chlorine reacts with organics. A pH above 7.0 favors the formation of TTHM while a pH less than 7.0 favors the formation of HAA5. Because corrosion control often raises finished-water pH to control lead and copper (Lead & Copper Rule), the two goals can clash. If TTHM is a problem where CCT is required, moving to an orthophosphate inhibitor can achieve LCR compliance without raising pH.

Chief Operator lens

Disinfection comes first. Controlling byproducts never justifies easing up on pathogen kill. The byproduct risks are chronic, the pathogens acute.
Monitor your source water. TOC and Alkalinity concentration can move the TOC removal targets and algae can cause serious disruptions.
Attack the precursors, not just the byproduct. Removing organic material up front by optimizing coagulation, flocculation, sedimentation, and filtration cuts formation at the source. Chasing byproducts after they form is harder.
TTHM and HAA5 build as chlorine sits in contact with organic material. They climb with warm water, long detention, and distance from the plant. Ensure tank turn over, aerate problem tanks, and flush dead ends where problems exist, especially during the summer.
Watch pH and disinfectant choice as your levers. pH steers whether TTHM or HAA5 dominates, and switching to chloramines or moving an injection point shifts your whole DBP picture.
Treat an operational evaluation level exceedance as an early warning, not a violation. Investigate and adjust before it becomes one.
If an acute microbial threat hits, the MRDL yields. The rule lets you carry chlorine or chloramines above the limit to protect public health during an event, provided you notify the State Board right away. Pathogen protection comes first.

Comprehensive Surface Water Treatment Rule

Purpose

Improve public health protection through the control of microbial contaminants, particularly viruses, Giardia lamblia, and Cryptosporidium.

How this rule evolved

The overarching theme of the Surface Water Treatment Rules is multi-barrier treatment. No single step is trusted to protect public health alone. Independent barriers — source protection, coagulation, flocculation, sedimentation, filtration, and disinfection — each remove or inactivate pathogens, so if one underperforms the others still carry the load.

The 1989 Surface Water Treatment Rule (SWTR) set the original treatment-technique requirements:

Combined Filter Effluent (CFE) ≤ 0.5 NTU (95th percentile) & 5 NTU max
3-log Giardia (99.9%)
4-log Virus (99.99%)
Residual Disinfection Requirements

The Interim Enhanced SWTR (IESWTR — large systems) and the Long Term 1 Enhanced SWTR (LT1 — small systems) tightened turbidity limits, added Individual Filter Effluent (IFE) monitoring, and Cryptosporidium (Crypto) requirements. IFE monitoring exists because CFE readings can mask a single filter's turbidity spike, and IFE is the control point for Crypto breakthrough:

CFE ≤ 0.3 NTU (95th percentile) & 1 NTU max
IFE Monitoring
2-log Crypto (99%)
Disinfection Profiling/Benchmarking
Sanitary Surveys
Covered Water Storage Facilities

The Filter Backwash Recycling Rule (FBRR) required conventional/direct filtration systems that recycle to return recycle flows through all treatment processes.

The Long Term 2 Enhanced SWTR (LT2) added Crypto source water monitoring, Crypto bin classification, and the Microbial Toolbox.

Paired with Stage 2 DBP

Paired with Stage 2 DBP: LT2 was issued alongside the Stage 2 Disinfectants / Disinfection Byproducts Rule to address two risks at once. LT2 strengthens pathogen protection. It adds bin-based Cryptosporidium treatment on top of the existing 2-log baseline. A system could undercut that by cutting disinfection doses to chase lower DBP levels. Stage 2 is the counterweight. Disinfection profiling and benchmarking must clear any significant change to disinfection practice before it can proceed.

Turbidity Requirements

Type	Limit	Monitoring
CFE 95% value Report total measurements and % ≤ limit	≤ 0.3 NTU	Continuous, record every 15 min
CFE maximum Report date/time of any exceedance	1 NTU*	Continuous, record every 15 min
IFE monitoring+ Report monitoring + follow-up actions	Exceedances trigger IFE follow-up.	Continuous, record every 15 min

*Exceeding the CFE max turbidity limit triggers DDW consultation within 24 hours. Failure to consult can escalate this to a Tier 1 Public Notification.

+Systems with ≤2 filters may monitor CFE continuously in lieu of IFE.

IFE FOLLOW-UP TRIGGERS — California systems serving ≥10,000

Return to Service — Post backwash or service interruption

Condition	Required Action
>0.3 NTU — after ≥60 min of continuous operation two consecutive readings 15 min apart	Produce a filter profile within 7 days if cause is unknown.
>0.5 NTU — once the filter has been in operation 4 h (return to service)	Take the filter out of service, inspect, and do not return it until deficiencies are corrected.
>2.0 NTU — any time during the first 4 h after return to service	Take the filter out of service, inspect, and do not return it until deficiencies are corrected.

California requires filtration rates to be increased gradually when a filter is returned to service after a backwash or interruption. A filter that reaches >1.0 NTU following at least 90% of its interruption events over any 12 consecutive months must also be taken out of service, inspected, and not returned until deficiencies are corrected.

Routine Operation — two consecutive 15-minute readings

Condition	Required Action
>1.0 NTU — any time	Produce a filter profile within 7 days if cause is unknown.
>1.0 NTU — same filter, 3 consecutive months	Conduct a filter self-assessment within 14 days.
>2.0 NTU — same filter, 2 consecutive months	Conduct a CPE.

What each action is

Filter Profile — a graph of one filter's turbidity across an entire run (backwash to backwash), including how it behaves while another filter is backwashed. (40 CFR 141.2)
Filter Self-Assessment — a structured evaluation of the problem filter where its performance is assessed. Develop a filter profile, identify and rank the factors limiting performance, judge which corrections apply, and write a report. (40 CFR 141.175(b))
Comprehensive Performance Evaluation (CPE) — a thorough review of the entire plant's performance and its operations and maintenance practices, to find what limits compliance and fix it without major capital investment where possible. Assess plant performance, evaluate the major unit processes, identify and rank performance-limiting factors, and write a report. (40 CFR 141.2)

FILTER BACKWASH RECYCLING REQUIREMENTS

Requirement	Information	Source
Treatment	Use of coagulant chemicals is advisable (and usually necessary) to meet turbidity goals	CAP (4.h); FBRR TGM (10.5.2)
Location	Return all recycle flows to the headworks of the treatment plant or an alternative location approved by the State Board	Tit. 22, § 64653.5(b)
Monitoring	Monitoring shall be representative of the recycled water.	Tit. 22, § 64654.8(b)(3)
Recycle Flow	≤ 10% of plant influent flow	CAP (4.h); FBRR TGM (10.5.2)
Turbidity	< 2.0 NTU	CAP (4.h); FBRR TGM (10.5.2)

Requirement figures above are design/operational guidelines/goals, not explicitly FBRR requirements - verify against your plant's permit.

Covered recycle flows

Filter Backwash Waste — Particles dislodged from filter media when a filter is backwashed.
Supernatant — Decant from a sedimentation basin used to hold solids.
Dewatering Liquids — Liquids from a unit concentrating solids for disposal (DAF, Belt Press, etc.)

Recycle information to keep on file

List of all recycle flows and the frequency they are returned.
Average and maximum backwash flow rates and backwash duration
Typical filter run length and a written summary of how it is determined.
Type of treatment provided for waste flows and for recycle flows.

LT2 — Cryptosporidium bin classification

LT2 targeted systems with higher concentrations of Cryptosporidium by establishing a bin classification derived through an initial study. Systems sampled Cryptosporidium, E. coli & turbidity monthly for 2 years and were then placed in a bin based on the average oocysts concentration. A follow-up study occurred 6 years after the initial bin classification and systems were recategorized where the average concentration changed.

The log removal credits required per bin were in addition to the 2-log baseline removal requirement established in the IESWTR/LT1.

Bin	Bin concentration (oocysts/L)	Conventional	Direct
Bin 1	< 0.075	No additional treatment	No additional treatment
Bin 2	0.075 – < 1.0	1-log	1.5-log
Bin 3	1.0 – < 3.0	2-log	2.5-log
Bin 4	≥ 3.0	2.5-log	3-log

Microbial Toolbox

The Microbial Toolbox is a EPA Technical Guidance Manual that outlines the set of "tools" a Water System can use to meet the additional Cryptosporidium treatment required by its LT2 bin classification. Systems may combine any of the applicable options below provided design, operational, and performance criteria are met.

Source: watershed control program; alternative source/intake management
Pre-Filtration: pre-sedimentation w/coagulation; two-stage lime softening; bank filtration
Treatment Performance: combined filter; individual filter; demonstration of performance
Additional Filtration: bag/cartridge; membrane; second-stage; slow sand
Inactivation: chlorine dioxide; ozone; UV.

Cryptosporidium Action Plan

The CAP is a DDW technical guidance document that clarifies how a surface water system in California optimizes its treatment process to meet existing regulatory requirements. Cryptosporidium can break through filters when operated improperly, and resist chlorine.

The CAP's authority is derived from the California Health and Safety Code (§116360) and includes:

Watershed Sanitary Surveys — a comprehensive survey of a watershed's contamination sources.
Source Bacteriological Monitoring — monthly raw water monitoring for E. coli.
Treatment Optimization Goals:
- Settled Effluent: 1-2 NTU
- Filter Backwash: 10% and <2.0 NTU
- CFE <0.1 NTU
Operations Plan — incorporate the goals above into the Operations Plan.
Reliable Processes — alarms, standby/redundant equipment and processes.
Alternate Treatment Technology — LT2 bin classification treatment options (see Microbial Toolbox).
Public Communication — Cryptosporidium language for the Consumer Confidence Report (CCR) and Fact Sheet.

Figures above are design/operational guidelines/goals, not explicitly SWTR requirements - verify against your plant's permit.

Disinfection & residual monitoring

Residual disinfectant must be maintained and monitored at the points below.

Location	Requirement	Frequency
Entry to Distribution System	Residual cannot be < 0.2 mg/L for more than 4 h	Continuous
Distribution System (BSSP Sample Sites)	Residual must be detectable in at least 95% (≥ 95%) of samples/month for any 2 consecutive months. An HPC ≤ 500/mL = a detectable residual.	at time of BSSP sample collection

Systems must also meet Stage 1 & 2 DBPR MRDLs and MCLs.

Disinfection profiling & benchmarking

The purpose of disinfection profiling and benchmarking is to allow systems and States to assess whether a change in disinfection practices reduces microbial protection. Systems must develop a disinfection profile that reflects Giardia and viruses inactivation, calculate a benchmark based on the profile, and consult with the State prior to making a significant change* to disinfection practices.

Disinfection Profile — a graphical representation of a system's microbial inactivation over 12 consecutive months.
Disinfection Benchmark — the lowest monthly average inactivation value.

*A Significant Change is defined as: change in point of disinfection, change in type of disinfectant, change in disinfection process, or any other modification designated by the state.

Chief Operator lens

Monitor your source water. Changes to water quality can have immediate and drastic impacts on treatment system performance.
Your LT2 bin placement sets how much extra treatment is owed.
Ensure your upstream treatment processes are optimized. Coagulation, flocculation, and sedimentation. Run jar tests, use a streaming current meter, analyze turbidity, etc.
Monitor CFE and IFE. One bad filter can hide behind a clean average and let particles through. Treat a rising trend as the earliest warning of breakthrough, and act on the trend, not just the limit.
Keep in mind that filtration and disinfection cover different pathogens. Filtration is the direct barrier for Cryptosporidium. Disinfection handles what remains of Giardia and viruses.
Build reliability into your system. Incorporate alarms, standby equipment, redundant processes, etc. to maintain compliance and increase resiliency.
Balance disinfection practices with disinfection byproducts. Check any disinfection change against the benchmark before making it. Don't trade lower byproducts for lost pathogen kill.
When a barrier breaks, treat it as a public-health event, not a paperwork item. Correct the unit or take it offline, notify DDW the same day, and check who is at risk downstream.

Ground Water Rule

Purpose

Reduce the risk of illness caused by microbial contamination in public ground water systems (GWSs).

A risk-targeted rule: identify ground water systems susceptible to fecal contamination, then correct significant deficiencies and source-water fecal contamination. Does not apply to systems that combine all ground water with surface water / GWUDI prior to treatment.

Sanitary Surveys

A DDW-conducted assessment of a ground water system to identify significant deficiencies that would make the system vulnerable to fecal contamination. Sanitary surveys are conducted every 3 years. This can be increased to every 5 years if:

the PWS provides 4-log treatment of viruses, or
has an outstanding performance record (as defined by the state) and no history of total coliform MCL or monitoring violations (TCR) since the last Sanitary Survey was conducted.

Triggered Monitoring

Systems not providing 4-log virus inactivation treatment must perform triggered source-water monitoring from any source in use when the PWS (or a purchasing system, if a wholesaler) receives a total coliform-positive routine sample result (TCR/RTCR).

Samples must be collected within 24 hours.
Samples must be taken before treatment (or at a state-approved location following treatment).
Samples must be analyzed for fecal coliforms (E. coli, enterococci, or coliphage).

A PWS that voluntarily discontinues 4-log treatment before/at the first customer makes the system subject to triggered source-water monitoring.

Notifications

Fecal-indicator-positive source sample → Tier 1 Public Notification
Failure to conduct required triggered / additional monitoring → Tier 3 Public Notification

Exceptions & invalidation

Distribution-system cause: not required to conduct triggered monitoring if the state documents the TC+ was caused by a distribution deficiency, or the system shows (within 30 days) the sample met state criteria for distribution conditions causing TC+.
Invalidation: state may invalidate a fecal-positive source sample on written lab notice of improper analysis, or substantial evidence the sample does not reflect source-water quality. If invalidated, resample for the same indicator within 24 h.

Treatment Technique

If a fecal-positive source sample is collected, or a sanitary survey identifies a significant deficiency, a ground water system must implement one or more corrective actions:

Correct all significant deficiencies
Provide an alternate source of water
Eliminate source of contamination
Provide 4-log treatment of viruses

Compliance Monitoring

A system can avoid triggered monitoring by notifying the state in writing that it provides ≥4-log virus treatment (inactivation, removal, or a state-approved combination) before or at the first customer, then monitoring to demonstrate it.

Chemical Disinfection

Population Served	Monitoring	Detail
≤ 3,300	Daily grab (or continuous)	Grab during hour of peak flow (or state-specified time); if a grab is below the state minimum, take follow-up samples every 4 h until residual meets/exceeds minimum
> 3,300	Continuous only	Record the lowest residual each day water is served; state-approved location

Membrane filtration: State-specified — monitor process & verify membrane integrity.
Alternative / UV: State-specified — UV: monitor intensity, flow, lamp status; verify sensor calibration ≥ monthly; validate reactor.

Continuous-Monitoring Equipment Failure

On failure, conduct grab sampling every 4 hours until the equipment is back in service.
Resume continuous monitoring within 14 days.

Notifications

Failure to maintain 4-log virus inactivation treatment → Tier 2 Public Notification
- Occurs when 4-log virus inactivation treatment is not restored within 4 hours — notify DDW ASAP.
Failure to conduct required compliance monitoring → Tier 3 Public Notification.

Chief Operator lens

Sanitary surveys catch deficiencies before they become contamination. Walk your wellheads, seals, and casings with the same eyes the engineer would use.
Know whether you provide 4-log virus treatment. That treatment technique defines everything you do under this rule.
A fecal-positive source sample is a public health event. Notify DDW and complete corrective actions.
Treat a coliform-positive sample in the distribution system as a possible source problem, not just a distribution one.
Monitor your 4-log virus treatment as required.

Total Coliform Rules

Purpose

Improve public health protection by reducing fecal pathogens to minimal levels through control of total coliform bacteria — including fecal coliforms and Escherichia coli (E. coli) — and by reducing potential pathways of entry for fecal contamination into distribution systems.

How this rule evolved

The 1989 Total Coliform Rule (TCR) established Bacteriological Sample Siting Plans (BSSP) with Routine and Repeat sampling locations, Sanitary Surveys, and a monthly total-coliform MCL.

The 2016 Revised TCR (RTCR) replaced the total-coliform MCL with an E. coli MCL, and established a "find-and-fix" treatment technique where TC+/EC+ results now trigger Level 1 / Level 2 assessments to locate and correct sanitary defects, rather than counting toward an MCL.

Bacteriological sample siting plan (BSSP)

Every PWS must maintain a written BSSP identifying distribution system sampling locations that represent system water quality and the collection schedule for all Routine & Repeat sampling sites.

Routine samples

Collected at regular intervals throughout the month.
In California, the minimum amount of required samples is determined based on population served or number of service connections, whichever results in the larger amount of required samples.
Each TC+ routine sample must be tested for E. coli and a Repeat Sample Set collected.
Any EC+ result must be reported to the State by the end of that day.

Repeat sample set

Within 24 hours of a TC+ result, the PWS must collect a Repeat Sample Set consisting of:

Repeat Sample: One sample from the same tap as the original sample
Upstream Sample: One sample collected within 5 service connections upstream of the original sample
Downstream Sample: One sample collected within 5 service connections downstream of the original sample

If any sample from the Repeat Sample Set is TC+, it must be analyzed for E. coli (any EC+ sample must be reported to the State by end of day) and another Repeat Sample Set collected unless an assessment is triggered by the State.

E. coli MCL violation combinations

Routine	Repeat
EC+	TC+
EC+	Any missing sample
EC+	EC+
TC+	EC+
TC+	TC+ (but no E. coli analysis)

An EC+ result must be reported to the state by the end of the day the PWS is notified.

Significant rise in bacterial count

Outside of the E. coli MCL violations above, the State can determine that a significant rise in bacterial count has occurred if:

A public water system collecting at least 40 samples per month has a total coliform-positive routine sample followed by two total coliform-positive repeat samples in the repeat sample set;
A public water system has a sample which is positive for E. coli; or
A system fails the E. coli MCL.

If any of the above occurs, the PWS must contact the State within 24 hours and perform an investigation into the operating procedures which may have caused the elevated bacteriological findings including:

Current operating procedures that are or could potentially be related to the increase in bacterial count;
Any interruptions in the treatment process;
System pressure loss to less than 5 psi;
Vandalism and/or unauthorized access to facilities;
Evidence indicating bacteriological contamination of facilities;
Analytical results of any additional samples collected, including source samples;
Community illness suspected of being waterborne; and
Records of the investigation and any action taken.

If the State determines a significant rise in bacterial count has occurred, the PWS may be required to issue a Tier 1 Public Notification.

Assessments & corrective action

Assessment	Triggered by	Conducted by
Level 1	<40 samples/mo: ≥2 TC+ in the month · ≥40 samples/mo: >5.0% TC+ · failure to take every required repeat	PWS owner/operator
Level 2	E. coli MCL violation · a second Level 1 trigger within a rolling 12-month period (annual-monitoring systems: 2 consecutive years)	State or state-approved party (PWS responsible for ensuring it happens)

Purpose: find sanitary defects that could provide a pathway for microbial contamination or indicate failure of protective barriers.

Deadline: submit the assessment form within 30 days of the trigger; corrective actions completed no later than form submission, or within a state-approved timeframe proposed on the form.

Treatment-technique violations

Failure to conduct a Level 1 or Level 2 assessment within 30 days of a trigger.
Failure to correct all sanitary defects from an assessment within 30 days (or the state-approved timeframe).
Failure of a seasonal system to complete its State-approved start-up procedure before serving water to the public.

Chief Operator lens

Total coliform is the alarm bell, and E. coli is the fire. A total coliform positive triggers an investigation; an E. coli hit is an acute public-health event with a Tier 1 notification.
Take every routine and repeat sample on time as outlined in your BSSP. A missed repeat is itself an assessment trigger.
When results trigger an assessment, find and fix the sanitary defect. Look for cross-connections, storage integrity, pressure loss, and intrusion.
A Level 1 assessment you run yourself while a Level 2 assessment brings the State in. Corrections stay your responsibility.
Chlorine residual is your early indicator. A spot where residual disappears is a spot where contamination can enter. Watch the low-residual ends of your system.

Arsenic Rule

Purpose

Improve public health by reducing exposure to arsenic in drinking water.

Background

Arsenic is a naturally occurring semi-metal found in rock and soil. It gets into water mainly by erosion of natural deposits, which is why it shows up in groundwater. Historic sources also include runoff from orchards (old arsenical pesticides) and wastes from glass and electronics manufacturing.

In California, it is one of the two most common regulated primary inorganic chemicals, along with nitrate, in groundwater.

Health Concern

Arsenic is a known human carcinogen. Long-term exposure is linked to cancer of the bladder, lung, and skin, plus non-cancer effects: skin damage and circulatory problems.

Limits

Arsenic's MCL is 10 ppb.

Monitoring Requirements

Samples must be collected from each source, or at each entry point to the distribution system that is representative of each source after treatment.

Systems that test below the MCL are given reduced monitoring requirements:

Ground Water: 1 Sample every 3 years
Surface Water: 1 Sample annually

Systems that test above the MCL are given increased monitoring requirements:

Quarterly until reliably and consistently below the MCL

Once a system has three rounds of monitoring with every result below the MCL (three compliance periods for groundwater, or three years for surface water), it may apply for a waiver of up to one 9-year compliance cycle, but must still collect ≥1 sample per source while the waiver is in effect.

Compliance Determination

Compliance is based on a running annual average (RAA) at each sampling point.
- No violation until 1 year of quarterly samples collected, unless fewer samples cause the RAA to exceed the MCL.
- When the RAA exceeds the MCL, issue a Tier 2 Public Notification.
When a sample exceeds the MCL, the response is
- Confirm the result
- Notify the State
- Begin increased (quarterly) monitoring as described above
If a single sample is >10× the MCL, collect a confirmation sample. If the average of those two samples is >10× the MCL the State may direct you to immediately take the source out of service, with written State approval required before it returns to service.
If arsenic results are greater than half the MCL (>5 ppb), but at or below the MCL (≤10 ppb), a statement must be made in the annual Consumer Confidence Report (CCR).

Treatment Technologies

These BATs remove arsenate, As(V) or As+5 much more effectively than arsenite, As(III) or As+3, which is uncharged and therefore poorly removed. In most groundwater the arsenic is arsenite, so systems pre-oxidize to convert As(III) to As(V) before treatment.

Reverse osmosis
Ion exchange
Electrodialysis
Activated alumina
Oxidation/filtration (for high removal, the iron-to-arsenic ratio must be at least 20 to 1)
Lime softening (not a BAT for systems under 500 service connections)
Coagulation/filtration (not a BAT for systems under 500 service connections)

Chief Operator lens

Know your source occurrence. Arsenic is natural and common in California groundwater; review each source's history against the MCL.
Respond deliberately. It is chronic, so confirm, notify, and step up monitoring; reserve taking the source out of service for the more-than-10× case.
If you treat, pre-oxidize to As(V) first, then choose a BAT that fits your system size and residuals handling. Reverse osmosis and electrodialysis reject a large volume of water, and arsenic-bearing waste needs proper disposal.

Nitrate

Purpose

Protect public health — particularly formula-fed infants — from nitrate in drinking water.

Background

Nitrate is a nitrogen compound and is largely a man-made contaminant. In California it is one of the two most commonly regulated primary inorganic chemicals in groundwater, along with arsenic.

Health Concern

Nitrate is an acute contaminant. In high enough concentrations it interferes with the blood's ability to carry oxygen. In formula-fed infants or younger children that drink water, this can cause methemoglobinemia, or "blue baby syndrome." In infants under six months this can come on quickly and, if left untreated, can be fatal, with symptoms including shortness of breath and a bluish skin color. High levels can also affect pregnant women.

Sources

Sources are largely man-made and include:

Fertilizer
Animal Feedlots
Manure
Septic Systems
Wastewater Discharges

Limits

Nitrate and Nitrite carry their own MCLs:

Nitrate: 10 mg/L
Nitrite: 1 mg/L
Nitrate + Nitrite (as N): 10 mg/L

Monitoring Requirements

Base monitoring frequency depends on source type:

Groundwater systems, and transient-noncommunity systems on approved surface water: annually.
Community and nontransient-noncommunity systems on approved surface water: quarterly.

Repeat monitoring steps up at half the MCL:

Groundwater: any single sample at or above 50% of the MCL puts you on quarterly monitoring for at least a year. After four straight quarterly results below the MCL, you may ask the State Board to return to annual.
Approved surface water: any single sample at or above 50% of the MCL puts you on quarterly monitoring. After four straight quarterly results below 50% of the MCL, you may return to annual; you go back to quarterly if any one sample reaches 50% of the MCL again.

Nitrite is sampled once per site as a baseline. If a single sample exceeds the MCL, handle it the same way as nitrate. Repeat monitoring is quarterly, then possibly annual, if a result is at or above half the MCL, or once every three years if it stays below half. Nitrate plus nitrite is tracked as a combined sum against the 10 mg/L limit; if the sum exceeds it, handle it as nitrate. If you treat for nitrate, you also sample the treated water monthly.

Compliance Determination

As an acute health risk, compliance is judged sample by sample, not on a running annual average. One exceedance triggers steps for confirmation and subsequent action:

The lab must notify you within 24 hours whenever a single sample exceeds the MCL. If the lab cannot reach you, it must notify the State Water Board directly.
Within 24 hours of that notice, a confirmation sample must be collected and analyzed.
- If the average of the two samples exceeds the MCL, a violation has occurred and a Tier 1 public notification must be issued.
- If you cannot resample within 24 hours, issue a Tier 1 public notice and collect the confirmation sample within two weeks.
- If the average is at or below the MCL, inform the State Board within 7 days.
Get below the MCL: take the source offline, blend it down, or move to a cleaner source. You cannot keep delivering water over 10 mg/L to the public.
If nitrate is detected above 5 mg/L (as nitrogen) but at or below the MCL, specific health-effect language must appear in the annual Consumer Confidence Report (CCR).

Treatment Technologies

Nitrates and Nitrites can be treated via three processes:

Ion exchange works by swapping nitrate/nitrite onto a resin, which then needs regeneration and brine (salt-waste) disposal. Watch for chromatographic peaking: if a run goes too long, the column can suddenly release stored nitrate/nitrite in a spike higher than the incoming level.
Reverse osmosis removes nitrate/nitrite well but wastes a large share of the feed water as reject.
Electrodialysis (Nitrate only) works well but is complex and generally suited to smaller systems.

Where a cleaner source exists, blending or switching sources is often the cheapest way to stay under the MCL. It is a source-management strategy rather than a listed BAT, but it is frequently the first move.

Chief Operator lens

Treat it as acute. Nitrate is not on a slow chronic clock. It is Tier 1, and the confirmation sample is on a 24-hour fuse, so know who your 24-hour contact is before you ever need them.
Protect infants first. The whole limit exists for babies under six months. If you are over the MCL, get affected users onto safe water, such as bottled or an alternate supply, right away while you fix the source.
Know your season. Nitrate rises with irrigation and rainfall, so your peak risk is agricultural season. Watch trending wells before they cross half the MCL.
Choose treatment for its waste stream. Ion-exchange brine and reverse-osmosis reject both need disposal, and if you run ion exchange, do not over-run the column or you will spike nitrate into the finished water.

Radionuclides Rule

Purpose

Reducing exposure to radionuclides in drinking water reduces the risk of cancer. This rule also improves public health protection by reducing exposure to all radionuclides.

Background

Radionuclides are radioactive forms of elements. Gross alpha emitters, radium-226, radium-228, and uranium occur naturally and get into water by erosion of natural deposits, so they show up mainly in groundwater.
Beta particle and photon emitters are mostly man-made. They are a concern only at systems the State designates as vulnerable, such as those downstream of a nuclear facility.

Health Concern

Long-term exposure raises the risk of cancer. Uranium also causes toxic effects on the kidneys.

Limits

Because they are carcinogens, the health goal (maximum contaminant level goal, MCLG) is zero for all of them. No level is considered risk-free.

Contaminant	MCL (Title 22)
Gross alpha particle activity (excluding radon and uranium)	15 pCi/L
Combined radium-226 / 228	5 pCi/L
Uranium	20 pCi/L
Beta/photon emitters*	4 mrem/yr

*Up to 168 individual beta/photon emitters may be used to calculate compliance.

Uranium: California's MCL of 20 pCi/L is by radioactivity and is stricter than the federal MCL of 30 µg/L (by mass) shown on the Drinking Water Standards page (that table shows federal values). It is the operative limit for a California system. Gross alpha (15 pCi/L) and combined radium (5 pCi/L) match federal.

Beta/photon equivalents: California expresses the 4 mrem/yr dose limit as specific activities: strontium-90 = 8 pCi/L, tritium = 20,000 pCi/L.

Detection levels for reporting (DLRs) set the "detection limit" used in the reduced-monitoring tiers below: radium-226 and radium-228 each 1 pCi/L, gross alpha 3 pCi/L, uranium 1 pCi/L, gross beta 4 pCi/L.

California (Title 22)

For a California system, Title 22 governs. California applies the radionuclide MCLs to both community and nontransient-noncommunity water systems; the federal rule (40 CFR §141.66) covers community water systems only. California's MCLs match federal except for uranium (see the MCL notes above).

Monitoring Requirements

Phase	Requirement
Initial	Four consecutive quarters at each entry point
Reduced (based on initial average)	< detection limit → 1 sample every 9 years
	≥ detection but ≤ ½ MCL → 1 sample every 6 years
	> ½ MCL but ≤ MCL → 1 sample every 3 years
Increased	Entry-point result > MCL → quarterly until 4 consecutive quarters below MCL

Beta particle & photon radioactivity

No monitoring required for most CWSs. Vulnerable CWSs: gross beta quarterly; tritium & strontium-90 annually.
Reduced: if RAA of gross beta minus naturally occurring K-40 ≤ 50 pCi/L → 1 sample every 3 years.
Increased: if it exceeds 50 pCi/L → speciate as required and sample at initial frequency.

All samples at each entry point to distribution.

Compliance Determination

These are chronic contaminants, not acute. An exceedance calls for a deliberate response, not immediate plant shutdown.

Treatment Technologies

California (Title 22 §64447.3) and federal rules (40 CFR §141.66) name the same best available technologies, which vary by radionuclide:

Combined radium-226/228: ion exchange, reverse osmosis, lime softening
Uranium: ion exchange, reverse osmosis, lime softening, coagulation/filtration
Gross alpha particle activity: reverse osmosis
Beta particle and photon radioactivity: ion exchange, reverse osmosis

Ion exchange and reverse osmosis are the workhorses across the board. The catch is residuals: spent resin, regenerant brine, and reverse-osmosis reject water concentrate the radioactivity and need proper disposal.

Chief Operator lens

Know your source occurrence. Radium, uranium, and gross alpha are natural in many California groundwaters; review each source against the MCLs. Beta/photon monitoring applies only if the State designates your system vulnerable.
Respond deliberately. These are chronic, so confirm, notify, and step up monitoring rather than shutting down on a single result.
Track uranium against California's limit, not the federal mass-based number.
If you treat, ion exchange and reverse osmosis are the go-to methods. Budget and permit for radioactive-residuals disposal early, since spent media and reject water can become the real cost.

Lead and Copper Rules

Purpose

Protect public health by minimizing lead (Pb) and copper (Cu) levels in drinking water, primarily by reducing water corrosivity. Pb and Cu enter drinking water mainly from corrosion of Pb- and Cu-containing plumbing materials.

How this rule evolved

The original Lead and Copper Rule (LCR) was introduced in 1991. Unlike most contaminants, which can be removed at the treatment plant, lead and copper leach into the water after it leaves the plant from lead service lines, old solder, brass fixtures, and copper pipe. The LCR set action levels (AL) of 15 ppb for lead and 1.3 mg/L for copper, measured as the 90th-percentile of tap samples. A system that exceeds either AL is tasked with reducing lead and copper at the tap, typically through corrosion control treatment or lead service line replacement.

The Lead and Copper Rule Revisions (LCRR) followed in 2021. The LCRR set a lead trigger level of 10 ppb, required systems to inventory their service lines for lead-containing materials, required notice to anyone served by a lead, galvanized, or unknown service line, and made public notification of a lead AL exceedance a Tier 1 notice. It also introduced the first requirements to sample for lead at schools and child-care facilities.

The Lead and Copper Rule Improvements (LCRI) takes effect on November 1, 2027. The LCRI eliminates the lead trigger level and lowers the lead AL to 10 ppb, requires all lead and galvanized service lines to be replaced within ~10 years, establishes improved sampling requirements and techniques, and expands the school and child-care sampling begun under the LCRR.

There is no safe level of lead exposure.

Current status (as of August 2026)

In force now: the original LCR framework in the blocks below, plus the LCRR pieces already phased in. LCRI takes over Nov 1, 2027.

Litigation: the LCRI is under challenge (AWWA v. EPA), with oral argument expected in fall 2026. No stay is in effect, so the rule and its Nov 1, 2027 compliance date stand.

Not likely to change prior to the August 2026 exam, but re-verify as necessary (https://www.awwa.org/resource/lead/).

LCR → LCRR → LCRI

The Lead and Copper Rule (LCR, 1991) and its two rebuilds: the Lead and Copper Rule Revisions (LCRR, 2021) and the Lead and Copper Rule Improvements (LCRI, 2024). This table shows what each version changed and what it left alone.

Requirement	LCR (1991)	LCRR (2021)	LCRI (Nov 2027)
Lead action level*	15 ppb	15 ppb	10 ppb
Copper action level*	1.3 mg/L	1.3 mg/L	1.3 mg/L
Service line inventory	None	New. Initial inventory due Oct 16, 2024	Baseline inventory due at compliance
Tap sampling	First-draw, 1 liter	Fifth-liter at lead service line sites (superseded before taking effect)	First and fifth liter; higher value governs
Lead service line replacement	≥ 7%/yr, only if over the AL after treatment; partial replacement and "replaced by testing" allowed	Superseded before it took effect	All lead and galvanized-requiring-replacement lines, ~10%/yr, generally within ~10 years; no partials, no testing credit
Find-and-fix / site assessment	None	Find-and-fix introduced: a single sample above the lead AL triggers site follow-up (superseded before taking effect)	Renamed Distribution System and Site Assessment (DSSA); applies at the lower LCRI lead AL
Public notification of a lead exceedance	None for the exceedance itself	Tier 1	Tier 1

*Based on 90th percentile sample results

Treatment technique responses if AL exceeded

An AL exceedance is not itself a violation. The exceedance triggers the below responses under today's rules (LCRR). The responses cascade in order of cost and disruption by targeting water chemistry treatment first, and replacing lead service lines only if that is not enough.

Under the LCRI this changes, and service line replacement becomes a standing requirement rather than a last step.

A lead action level exceedance requires a Tier 1 public notice to all consumers within 24 hours.
Public Outreach & Education (lead only):
- Deliver educational materials within 60 days after the end of the monitoring period. While the exceedance continues, repeat annually and include a message on each water bill at least quarterly.
Water Quality Parameter (WQP) Monitoring:
- No existing Corrosion Control Treatment (CCT): baseline water chemistry (pH, alkalinity, calcium, conductivity, temperature) that helps the State decide what corrosion control to require.
- Existing CCT: the same parameters plus the inhibitor residual already dosed.
Corrosion Control Treatment (CCT) - The State designates one or more of three treatments:
- pH/Alkalinity Adjustment - Raise pH (caustic soda, lime, etc.) and hold alkalinity so lead and copper stay less soluble and a stable, protective scale forms.
  - Usually the first and lowest-cost option, but increasing pH affects disinfection efficacy and byproduct formation.
- Corrosion Inhibitor - Feed orthophosphate (or a silicate) to build a protective film on the pipe and hold a residual to the tap. The workhorse for lead, but phosphate adds load to downstream wastewater and needs a constant, reliable feed.
- Calcium Hardness Adjustment. Adjust calcium and carbonate to lay a thin calcium carbonate film on the pipe. Seldom the primary fix for lead; mainly for soft, low-calcium water.
Once the State designates the required CCT, install it within 24 months, then run 2 consecutive 6-month rounds of tap and WQP monitoring. The State then sets optimal WQPs (OWQPs) that define your corrosion control treatment requirements.
Source Water Treatment (SOWT) - Within 6 months of the exceedance, sample each source entry point to measure how much lead or copper comes from the source, then recommend treatment or show it is not needed. If required, install within 24 months. The State sets maximum permissible source levels.
Lead Service Line Replacement (LSLR) - Used only if the lead AL is still exceeded after CCT and SOWT. Replace at least 7% of lead service lines per year. Under the rules in force now, a line also counts as "replaced" if its own samples are at or below the lead AL ("replaced through testing").
Stopping - Discontinue public outreach and LSLR once the 90th percentile stays at or below the lead AL for 2 consecutive 6-month periods. Resume if it is exceeded again.

LCRI change

The LCRI removes the "replaced through testing" approach and mandates full replacement of any lead or galvanized-requiring-replacement service lines regardless of whether sampling results have fallen below the AL.

Landmark lead events

Washington, D.C. (2001–2004)
- What happened: Lead levels spiked citywide, one of the worst lead-in-water events in U.S. history.
- What changed: The utility switched its disinfectant from free chlorine to chloramine to cut disinfection byproducts and comply with the DBP rule. Chloramine changed the water chemistry so that the insoluble lead scale that free chlorine had been holding in place became unstable and started releasing lead. A change made to fix one problem caused another.
Flint, Michigan (2014–2015)
- What happened: Lead leached into the water after a source switch.
- What changed: The city switched its source from treated Detroit water to the Flint River to save money, and did not add corrosion control treatment to the new, more corrosive water. With no corrosion inhibitor, the more aggressive water stripped the protective scale off lead service lines.
Newark, New Jersey (2017–2019)
- What happened: Lead exceeded the action level starting in 2017, in the half of the city served by one of its two treatment plants (the Pequannock plant).
- What changed: The corrosion control treatment Newark already had in place stopped working. A shift in water chemistry (pH drifting out of the range the inhibitor needed) made the existing corrosion control ineffective, and the scale began releasing lead.

Chief Operator lens

The LCRI is a multi-year program. What changes is in the table above. Here is how a system gets ready, with public health first throughout.

Service Line Inventory - The inventory becomes the replacement roadmap. Keep it current and resolve every unknown-material line.
Replacement Program - Replacement becomes mandatory for every lead line and every galvanized line that requires replacement, on the roughly 10-year clock in the table, regardless of tap sampling results. Budget and plan for it now (funding through state revolving fund loans, grants, and rates, contractors lined up, and a maintainable yearly pace to stay on schedule).
Corrosion Control (Lower AL) - The lead action level drops. Re-check existing corrosion control treatment against the tighter number and plan for re-optimization the LCRI requires after an action level exceedance.
Tap Sampling - Sampling moves to the new first-and-fifth-liter method at lead service line sites (see the table). Identify qualifying sites, train samplers, and update procedures ahead of the date.
Schools & Child Care Facilities - Develop or improve the expanded sampling and outreach program for schools and licensed child-care facilities.
Public Outreach - Start customer communication early, coordinate funding with your governing board, and plan staffing for the added workload. Be prepared to issue timely (Tier 1) public notification if the lead action level is exceeded. Update revised lead language within the CCR.
California timing - The State's adoption of the LCRI into Title 22 and the current California action level are tracked on the Upcoming Regulations page.

Manganese

Purpose

Protect public health — particularly formula-fed infants — from neurotoxic effects of elevated manganese, while managing its long-standing aesthetic impacts (discoloration, staining).

Background

Manganese is a hard, brittle, silvery-gray chemical element and is the 12th most abundant element in the earth's crust.

Health Concern

It is an essential nutrient, but over-exposure poses a neurotoxic risk; occupational exposure causes manganism, a cognitive/motor syndrome resembling Parkinson disease.
Formula-fed infants are the most susceptible population — they absorb and/or retain more manganese than adults. This is the driver of the 2026 revision.
Aesthetic effects at lower concentrations: discolored water, staining of plumbing fixtures and laundry, sediment buildup.

Sources

Manganese is a naturally occurring element found in the earth's crust. As such, it is commonly found in both ground water and surface water sources.

Limits

Notification Level (NL): a nonregulatory, health-based advisory level for a contaminant without an MCL.
Response Level (RL): the recommended concentration at which systems consider taking a source out of service or providing treatment.

Level	Value	Basis
Secondary MCL	50 ppb	RAA
Notification Level	50 ppb	RAA
Response Level	200 ppb	Single confirmed detection w/follow-up sample

Note: The secondary MCL and the Notification Level are the same value.

California — where this stands, June 2026

On June 2, 2026, DDW issued revised notification and response levels for manganese and requested that OEHHA establish a Public Health Goal — the first step toward a primary MCL. Manganese is a live rulemaking to watch.

Monitoring Requirements

Groundwater: every 3 years
Surface water: annually

If manganese exceeds the secondary MCL (50 ppb):

Go to quarterly monitoring
After a year of quarterly results below the MCL with no upward trend, the system can ask the State for reduced frequency

Compliance Determination

The NL exceedance is determined via the RAA. If exceeded:
- notify the governing body within 30 days.
The RL can be exceeded with a single value. If exceeded, take a repeat sample and average the two for confirmation. If the RL is still exceeded:
- notify the State within 7 days
- Issue a Tier 2 public notification within 30 days of the initial exceedance. The notice must notify customers to use an alternative water source (e.g., bottled water) when preparing infant formula
- The PWS must either treat the source or remove it from service.

Treatment Technologies

While no BAT is explicitly given for manganese, common treatment options include oxidation, usually with chlorine or potassium permanganate, followed by filtration, typically with greensand, which is a glauconite-based filtration media.

Chief Operator lens

Know your source occurrence — manganese is natural and widespread, especially in groundwater; review historical Mn data per source against the notification and response levels.
If you treat for Mn (greensand/oxidation-filtration, sequestration), verify treated effluent performance against the new levels, not just the secondary MCL.
Prepare the two notification pathways in advance (governing-body notice; infant-formula customer advisory) — DDW has published templates and an FAQ.
Budget/plan for a future primary MCL: the PHG request is the leading indicator.
Watch sequestration waivers: iron/manganese secondary-MCL waivers are conditioned on results staying under the notification level, so the tightened level narrows who qualifies.

PFAS (Per- and Polyfluoroalkyl Substances)

Background

PFAS are a group of more than 14,000 human-made substances that are characterized by a strong carbon-fluorine bond. In typical conditions, PFAS are resistant to degradation and do not break down in the environment (commonly called "forever chemicals"). PFAS are widely used as surface coatings in consumer, commercial, and industrial products such as carpet, clothing, food packaging, non-stick cookware, firefighting foam, etc.

Health Concern

PFAS exposure may result in adverse health effects including developmental effects to fetuses during pregnancy, cancer, liver effects, immune effects, thyroid effects, and other effects.

Sources

Detected in air, water, wastewater, fish, and soil worldwide, PFAS are especially present in and around facilities that produce, use or dispose of PFAS or PFAS containing materials.

Four major sources of PFAS in drinking water

Fire training and response sites
Industrial sites
Landfills
Wastewater treatment plants and biosolids

Limits

Federal — 2024 PFAS NPDWR

On April 10, 2024, the U.S. EPA announced the final National Primary Drinking Water Regulation (NPDWR) for six PFAS establishing legally enforceable MCLs, plus a Hazard Index (HI) MCL for PFAS mixtures.

Hazard Index concept (exam-testable): a sum of fractions, where each fraction compares the measured level of a PFAS to the highest level below which there is no risk of health effects; the HI MCL is set at 1.

Federal MCLs and California NL/RL

Abbreviation	Chemical name	Fed MCL	Fed MCLG	CA NL	CA RL
PFOA	Perfluorooctanoic acid	4.0	Zero	4.0	10
PFOS	Perfluorooctane sulfonic acid	4.0	Zero	4.0	40
PFHxS	Perfluorohexane sulfonic acid	10	10	3.0	10
PFNA	Perfluorononanoic acid	10	10	—	—
HFPO-DA (GenX)	Hexafluoropropylene oxide dimer acid	10	10	—	—
PFBS	Perfluorobutane sulfonic acid	—	2,000	500	5,000
PFHxA	Perfluorohexanoic acid	—	—	1.0 µg/L	10 µg/L
PFHpA	Perfluoroheptanoic acid	—	—	requested	requested
Hazard Index	Mixture of ≥2 of PFHxS, PFNA, PFBS, HFPO-DA	1 (unitless)	1 (unitless)	—	—

Values are ng/L (= parts per trillion, ppt) unless noted. PFHxA is in µg/L (1.0 µg/L = 1,000 ng/L). PFBS has an MCLG but no individual MCL; the Hazard Index is unitless.

Federal MCLs and MCLGs finalized April 2024. California NL and RL issued or revised October 29, 2025, except PFBS (March 5, 2021); PFHpA requested.

Federal status — pending 2026 proposals

The 2024 federal PFAS rule is the current, enforceable standard and the likely exam basis. In May 2026 EPA proposed revisions (keeping some limits, rolling back others), but they are proposed rules only, not final, so the 2024 rule still governs. Re-verify federal status close to your exam. (Source: EPA, May 2026; not on the Water Boards page.)

California status — PHGs and MCL development

California has not yet adopted PFAS MCLs. Until it does, the state manages PFAS through DDW monitoring orders and Notification and Response Levels, while OEHHA develops Public Health Goals (PHGs) that will drive the eventual state MCLs. That PHG-to-MCL pathway is the same one shown in "How California establishes an MCL" on the Upcoming Regulations page.

Monitoring Requirements

Federal Compliance Timeline

Milestone	Deadline
Initial monitoring complete	Within 3 years of promulgation (2024–2027)
Compliance monitoring begins; initial + compliance results in CCR; Tier 3 public notification for monitoring/testing violations	Starting 3 years after promulgation (2027–2029)
Comply with all MCLs; Tier 2 public notification for MCL violations	Starting 5 years after promulgation (2029)

Compliance Determination

Notification Level (NL): a nonregulatory, health-based advisory level for a contaminant without an MCL.
Response Level (RL): the recommended concentration at which systems consider taking a source out of service or providing treatment.

Trigger	Required response
Detect above the NL	Notify the governing body within 30 days (HSC §116455); report confirmed detections in the CCR (§116378).
Detect above the RL	Take the source out of service, treat the delivered water, or provide public notification (HSC §116455/§116378).

Applies to systems that receive a DDW monitoring order; the RL response requirement has been in force since January 2020.

See the combined Federal MCLs and California NL/RL table above for NL and RL values.

Treatment Technologies

Granular Activated Carbon (GAC)
Ion Exchange
Reverse Osmosis (RO)

Chief Operator lens

Know your source vulnerability: proximity to the four major source categories (fire training sites, industrial sites, landfills, WWTP/biosolids); groundwater sources are the accumulation risk.
Complete initial monitoring by 2027.
Track results against NLs and RLs; execute the required response(s) on NL or RL exceedance.
Report confirmed detections in the CCR.
Plan for federal MCL compliance by 2029 and watch California's own MCL rulemaking.
Pursue funding where needed — State Water Board PFAS grants/loans and EPA's Emerging Contaminants in Small or Disadvantaged Communities grant.
Maintain records of monitoring results, lab reports, order correspondence, and public notifications, consistent with the Record Keeping Rules page of this dashboard.

Upcoming Regulations

Purpose

Track pending California and federal drinking-water regulations so the agency can anticipate compliance obligations before they land. A T5 Chief Operator is expected to know what is coming, not just what is in force.

Status — snapshot

Sourced from DDW's Upcoming Regulations page and the Board's 2026 Regulatory Priorities (adopted March 2026). This is a snapshot as of August 2026. Verify against the DDW page before the exam.

First, the standing process: how California turns an emerging contaminant into an enforceable MCL. This part does not change from year to year. Everything after it is a dated snapshot of the specific rules that process currently has in motion.

How California establishes an MCL

California builds a primary MCL through a defined statutory ladder, not by direct EPA adoption:

Contaminant identified via occurrence data, the Unregulated Contaminant Monitoring Rule (UCMR), or monitoring orders.
- The UCMR is the heart of regulatory change. Roughly every five years the U.S. Environmental Protection Agency (EPA) names a set of contaminants that have no drinking-water standard yet and has water systems test for them. The results go into a national occurrence database EPA uses to decide whether a contaminant needs a federal rule.
Notification and Response Levels (NL & RL) are issued.
The Office of Environmental Health Hazard Assessment (OEHHA) sets a Public Health Goal (PHG).
DDW sets the MCL as close to the PHG as technologically and economically feasible.
The MCL is adopted into Title 22.

DDW must also review existing MCLs against current PHGs at least every five years (the quinquennial MCL review). This review generates most of the pending MCL revisions listed below.

Hexavalent chromium — adopted; first compliance date arrives October 1, 2026

Cr(VI) MCL: 0.010 mg/L; DLR 0.0001 mg/L. Rule effective October 1, 2024; the MCL applies on the phased compliance dates below.
CA total chromium MCL: 0.05 mg/L, stricter than the federal total chromium MCL of 0.1 mg/L shown on the Drinking Water Standards page.

System size (service connections served on October 1, 2024)	Cr(VI) MCL compliance date
10,000 or greater	October 1, 2026
1,000 to 9,999	October 1, 2027
Fewer than 1,000	October 1, 2028

Initial monitoring: community and NTNC systems began Cr(VI) compliance monitoring on April 1, 2025.
Compliance plan: an MCL exceedance before your compliance date requires a Hexavalent Chromium MCL Compliance Plan within 90 days (compliance method; pilot study if new or modified treatment; construction dates; Operations Plan date).
Operations plan: new or modified treatment requires a State Board-approved Hexavalent Chromium Operations Plan before serving treated water (performance monitoring, maintenance program, unit-process descriptions, dose-rate procedures, reliability features).

MCLs in development

PFAS — California MCL rulemaking underway; the federal 2024 rule is in force with 2026 federal proposals pending. See the PFAS page.
Disinfection byproducts — current framework on the Stage 1 & 2 DBP Rules page.
- TTHM and HAA5 — MCL revisions under consideration.
- NDMA (N-nitrosodimethylamine) — new MCL in development; a nitrosamine disinfection byproduct associated with chloramination.
Styrene — MCL revision in process (current MCL on the Drinking Water Standards page).
Cadmium and mercury — MCL revisions in process (quinquennial-review outcome).
1,4-Dioxane — MCL in development.
Arsenic — California MCL revision in process. See the Arsenic Rule page.

NL/RL watch list

Manganese — revised June 2, 2026. Full treatment on the Manganese page.
Cyanotoxins — notification levels under development (harmful-algae-bloom program). Ties to the algae-bloom operations scenario in the Study Tools.
PFHpA — NL/RL requested. See the PFAS page NL/RL table.

Lead and Copper Rule Improvements — California adoption

The federal LCRI (what it is, the evolution table, and the "Meeting LCRI" compliance plan) lives on the Lead and Copper Rule page. This entry adds only the California adoption layer:

California is adopting the federal LCRI into Title 22 as a new Chapter 17.6 ("Control of Lead and Copper"), effective November 1, 2027, with the existing Chapter 17.5 repealed the same day, through an emergency rulemaking. The State Water Board was scheduled to consider adoption at its August 18–19, 2026 Board meeting (as of August 2026). Until then, the codified California numbers stay on the old framework (see the Lead and Copper Rule page).
A companion policy handbook for lead testing at schools and child-care facilities (Assembly Bill 1096) is in development alongside it.

Other pending items

Detection Limits for Purposes of Reporting (DLRs) — updates in process for metals and organic chemicals.
Primacy package approvals in progress — Public Notification Rule, Ground Water Rule, Revised Total Coliform Rule, PFAS NPDWR, Lead and Copper Rule and revisions, CCR Rule. These bring California's rules formally in line with the federal versions.
CCR Rule revisions — 2027 changes, covered in the status callout on the CCR page.
Microplastics — monitored under a policy handbook (Senate Bill 1422), not a numeric standard. Awareness item only.

Recently in effect (context, not pending): Direct Potable Reuse (October 1, 2024); Cross-Connection Control Policy Handbook revisions (April 21, 2026); Onsite Treatment and Reuse of Nonpotable Water (April 22, 2026); Electronic Reporting of Drinking Water Quality Data (July 13, 2026).

Chief Operator lens

Track the DDW Upcoming Regulations page and the annual Regulatory Priorities resolution; subscribe to DDW announcements.
Translate each pending item into agency exposure: which sources/treatment/reporting would be affected, and on what date.
The recurring exam pattern: NL/RL → PHG → MCL. If a contaminant has a fresh NL revision or PHG request (manganese, PFAS), an MCL is the expected next step — budget and plan accordingly.

Standardized Monitoring Framework

Purpose

Standardize, simplify, and consolidate monitoring requirements across contaminant groups. The SMF increases public health protection by simplifying monitoring plans and synchronizing monitoring schedules, leading to increased compliance with monitoring requirements.

How this page is built

The SMF Quick Reference Guide presents the framework as year-by-year grids (2020–2037). Those grids encode a frequency logic. This page presents that logic directly (contaminant → status → frequency) plus the governing footnotes, rather than reproducing the 18-column grids. The framework itself is unchanged.

The SMF synchronizes monitoring for chemical and radiological contaminants into a repeating 9-year compliance cycle made of three 3-year compliance periods. It covers inorganic contaminants (IOCs), synthetic organic contaminants (SOCs), volatile organic contaminants (VOCs), and radionuclides (radioactive contaminants) — with named exceptions.

IOCs, SOCs, and VOCs are also written as inorganic, synthetic organic, and volatile organic chemicals.

Scope

Applies to	Contaminants
All PWSs	Nitrate, Nitrite
CWSs	IOCs, SOCs, VOCs, Radionuclides
NTNCWSs	IOCs, SOCs, VOCs

Counts and Exceptions

15 IOCs (nitrate, nitrite, asbestos are SMF exceptions)
51 SOCs & VOCs (vinyl chloride for ground water is an exception)
4 radionuclides (excludes beta/photon emitters)

Frequency logic by contaminant group

IOCs — Ground water

Status	Frequency
≤ MCL w/no waiver, or Reliably & consistently < MCL	Once per 3-year compliance period
With waiver	Once per 9-year cycle — 1 sample while the waiver is effective, renewed each cycle
> MCL / not R&C < MCL	Quarterly — 4 quarterly samples at each entry point to the distribution system within the primacy-agency timeframe

IOCs — Surface water

Status	Frequency
≤ MCL w/no waiver, or Reliably & consistently < MCL	Annual — 1 sample at each entry point to the distribution system
With waiver	Once per 9-year cycle — 1 sample while the waiver is effective, renewed each cycle
> MCL / not R&C < MCL	Quarterly — 4 quarterly samples at each entry point to the distribution system within the primacy-agency timeframe

Asbestos

Status	Frequency
No waiver, R&C < MCL, or vulnerable to asbestos	Once per 9-year cycle — 1 sample in the first 3-year compliance period
With waiver (vulnerability assessment every 3 years)	No sample unless the primacy agency requires it
> MCL / not R&C < MCL	Quarterly — 4 quarterly samples at each entry point to the distribution system within the primacy-agency timeframe

Vulnerable through asbestos-cement pipe corrosion: sample at a tap served by that pipe. Vulnerable at the source: sample at each entry point to the distribution system.

SOCs (all sizes)

Status	Frequency
Reliably & consistently < MCL	Annual — 1 sample at each entry point to the distribution system
< detect, no waiver (population > 3,300)	2 quarterly samples in one year of each 3-year compliance period
< detect, no waiver (population ≤ 3,300)	Once per 3-year compliance period
With waiver (vulnerability assessment every 3 years)	No sample unless the primacy agency requires it
≥ detect / not R&C < MCL	Quarterly — 4 quarterly samples at each entry point to the distribution system within the primacy-agency timeframe

Annual samples are taken in the quarter that previously produced the highest result. After 3 consecutive annual samples below the detection limit a system may seek a waiver; the primacy agency reconfirms non-vulnerability every 3 years.

VOCs — Ground water

Status	Frequency
< detect, no waiver	Annual — 1 sample at each entry point to the distribution system
< detect after ≥3 annual samples	Once per 3-year compliance period
Reliably & consistently < MCL	Annual — 1 sample at each entry point to the distribution system
With waiver (vulnerability assessment every 3 years)	1 sample per 6-year waiver term (two compliance periods)
≥ detect / not R&C < MCL	Quarterly — 4 quarterly samples at each entry point to the distribution system within the primacy-agency timeframe

VOCs — Surface water

Status	Frequency
< detect w/no waiver, or Reliably & consistently < MCL	Annual — 1 sample at each entry point to the distribution system
With waiver (vulnerability assessment every 3 years)	No sample unless the primacy agency requires it
≥ detect / not R&C < MCL	Quarterly — 4 quarterly samples at each entry point to the distribution system within the primacy-agency timeframe

Annual VOC samples are taken in the quarter that previously produced the highest result. A ground water waiver still requires 1 sample every 6 years; a surface water waiver requires no routine sample. After 3 consecutive annual non-detects a system may seek a waiver.

Nitrate — Ground water

Status	Frequency
< ½ MCL, or Reliably & consistently < MCL	Annual — 1 sample at each entry point to the distribution system
≥ ½ MCL / not R&C < MCL	Quarterly — 4 quarterly samples

Nitrate — Surface water

Status	Frequency
After 4 consecutive quarters < ½ MCL	Annual — 1 sample at each entry point to the distribution system
≥ ½ MCL within the last four quarters	Quarterly — 4 quarterly samples

Nitrate — TNCWSs (ground & surface water)

Status	Frequency
All systems	Annual — 1 sample at each entry point to the distribution system

No R&C < MCL determination is allowed for surface water nitrate. A 20 mg/L nitrate MCL may be approved by the primacy agency for certain non-community systems not serving children under 6 months (40 CFR §141.11(d)).

Nitrite

Status	Frequency
< ½ MCL	As specified by the primacy agency
Reliably & consistently < MCL	Annual — 1 sample at each entry point to the distribution system
≥ ½ MCL / not R&C < MCL	Quarterly — 4 quarterly samples

Radionuclides

Status	Frequency
< detect	Every 9 years
≥ detect and ≤ ½ MCL	Every 6 years
> ½ MCL and ≤ MCL	Every 3 years
> MCL	Quarterly until 4 consecutive quarters < MCL

Covers gross alpha, radium-226, radium-228, and uranium. Beta particle and photon radioactivity are monitored separately under 40 CFR §141.26(b).

"R&C < MCL" = primacy agency has determined the point is reliably and consistently below the MCL.

Key conditions (footnotes)

Trigger levels: quarterly sampling is triggered at > MCL (IOCs), > detection limit (VOCs/SOCs), or ≥ ½ MCL (nitrate/nitrite). No R&C < MCL determination for surface-water nitrate.
If the RAA of quarterly sampling is > MCL, remain quarterly until qualifying as R&C < MCL.
Annual samples taken in the quarter that previously gave the highest result.
SOC/VOC waiver: apply after 3 consecutive annual results below detection; vulnerability reconfirmed every 3 years (VOC waiver effective 2 periods / 6 years).
Asbestos: monitor in the 1st 3-year period of each 9-year cycle (tap served by A-C pipe, or each entry point to the distribution system if source-vulnerable).
Nitrate MCL of 20 mg/L may be approved for NCWSs not serving children under 6 months if criteria met (§141.11(d)).

Chief Operator lens

Treat the framework as one master monitoring calendar. Its purpose is to put every chemical and radiological contaminant on one schedule so nothing slips — build your sampling plan from it.
Your frequency is earned, not fixed. Clean history and waivers buy less frequent sampling; a result over the trigger puts that source on quarterly monitoring until it's reliably back down.
Don't let a waiver make you complacent. It still requires the occasional confirming sample and a source that stays non-vulnerable — conditions change, and so can your obligation.
A missed monitoring window is its own violation, separate from any exceedance. The calendar discipline is the compliance.

Consumer Confidence Report Rule

Purpose

Improve public health protection by providing educational material to allow consumers to make educated decisions regarding any potential health risks pertaining to the quality, treatment, and management of their drinking water supply.

Current status (as of August 2026)

The 2024 EPA CCR Rule Revisions apply federally starting 2027 (first revised reports due July 1, 2027) — see the comparison table below for what changes.

Annual deadlines

A wholesale CWS must deliver the information needed to prepare a CCR to its purchasing system(s) by April 1st, or a date mutually agreed upon and specifically included in the contract.
CWSs must distribute their CCR to its customers and DDW by July 1st.
CWSs must submit proof of CCR distribution to DDW by October 1 (or 90 days after distribution).

Eight required content items

Water system information — contact name/phone; public-participation opportunities
Source(s) of water
Definitions — MCL, MCLG, TT, AL, MRDL, MRDLG
Detected contaminants — table of concentrations vs. MCLs/MCLGs (or MRDLs/MRDLGs), known sources, health-effects language
Monitoring info for Cryptosporidium, radon, and other contaminants (if detected)
Compliance with other regulations — violations and GWR special notices
Variances and exemptions (if applicable)
Required educational information — contaminants in drinking & bottled water; vulnerable-population Cryptosporidium info; nitrate, arsenic, and lead statements

Memory Tool — MASTER

M-Monitoring info (crypto, lead, etc.)
A-Analytes (detected contaminants)
S-System Info (Contact + Sources)
T-Terms Defined (MCL, MCLG, etc.)
E-Educational/Health Info
R-Regulatory (Compliance + Variances)

Reporting & recordkeeping

Mail or directly deliver a copy to each customer; make a good-faith effort to reach non-bill-paying consumers.
Large-population non-English communities: include information in the appropriate language(s) or a contact for a translated copy.
CWS serving ≥ 100,000 must also post the current report on a publicly accessible website.
All CWSs must make copies available on request.

2027 CCR Revisions

Component	California now (Title 22)	EPA revised (2027)
Report frequency (systems ≥ 10,000)	Annual, by July 1 (§64480)	Twice per year: first by July 1, second by Dec 31. Second report adds a 6-month update if the system had violations, action-level exceedances, or UCMR results. Systems < 10,000 stay annual.
Delivery method	Mail or direct delivery (§64483(a))	Mail or electronic; paper copy on request
Certification to primacy agency	Report by distribution date; certification within 3 months (§64483(c))	Report + certification within 10 days of required distribution
Website posting	Systems ≥ 100,000 post current report; retain reports ≥ 3 years (§64483(f),(g))	Systems ≥ 50,000 post; any posted report kept available ≥ 3 years
Summary section	Not required	Required at the start — contact info, brief description of any violations, note if public notices are included
Translation access	Spanish required; other languages if group > 1,000 residents or > 10% of the community (§64481(l))	Where to get a translated copy/assistance; systems > 100,000 develop language access plans
Lead action-level exceedance	Lead/copper action language per appendix 64465-D on violation (§64481(g)(3))	Must identify the exceedance in the data section and explain it, consumer steps to reduce exposure, and corrective actions

CA column: Title 22 as compiled Aug 2025 (project file) plus DDW's 2025 CCR-cycle instructions. EPA column: 2024 CCR Rule Revisions (89 FR 45980, May 24, 2024). CA adoption timing unconfirmed — verify before exam.

Chief Operator lens

The CCR is your once-a-year public-health communication — treat it as trust-building, not a chore. Clear, honest, plain language does more for confidence than a perfect table nobody reads.
Hit the deadline and prove delivery. Distribution and the certification that follows are both enforceable — a late or unproven CCR is a violation even if the water was perfect.
Report what you detected accurately and explain it: the level, the likely source, and the health context, in language a customer understands.
Use it to get ahead of concerns. If something ran high but stayed compliant, explain it plainly here before a customer hears it elsewhere.

Public Notification Rule

Purpose

Notify the public of drinking water violations or situations that may pose a risk to public health.

Notify persons served (not just billing customers) of violations or situations that may pose a health risk. The clock starts when the PWS learns of the violation.

Tier 1 Within 24 hours

Fecal coliform / E. coli present in a distribution sample; failure to test after a TC-positive.
Nitrate, nitrite, or total nitrate+nitrite MCL violation; failure to take a confirmation sample.
Chlorine dioxide MRDL exceeded at the entrance to distribution and in one or more distribution samples the next day — or failure to take those distribution samples.
Exceedance of the maximum turbidity level, if elevated to Tier 1 by the primacy agency.
A treatment-technique violation posing an acute risk to health (e.g., failure to filter or disinfect under the SWTR/IESWTR/LT1/LT2), as determined by the primacy agency.
Lead action level exceedance under the Lead and Copper Rule (LCRR/LCRI).
Waterborne disease outbreak or other emergency.
Detection of E. coli, enterococci, or coliphage in a ground water source sample.
Other violations/situations determined by the primacy agency.

Tier 2 As soon as practical, within 30 days

All MCL, MRDL, and treatment-technique violations except where Tier 1 is required.
Monitoring violations, if elevated to Tier 2 by the primacy agency.
Failure to comply with variance/exemption conditions.
Chlorine dioxide MRDL exceeded in 2 consecutive daily samples at the entrance to distribution only (escalates to Tier 1 if a distribution sample the next day also exceeds).
GWR 4-log systems: failure to maintain treatment for more than 4 hours.
Failure to take required corrective action for a fecal-positive source or a significant deficiency (GWR).
Special notice (LT2): failure to collect 3 or more months of source-water Cryptosporidium samples, or failure to determine bin classification or mean Cryptosporidium level — a monitoring violation that is Tier 2, not Tier 3.

Repeat every 3 months until resolved.

Tier 3 Within 12 months

Monitoring / testing-procedure violations (unless elevated), including failure to profile/benchmark or to develop a monitoring plan.
Operating under a variance or exemption.
Special notices: unregulated-contaminant results; fluoride SMCL exceedance.

Repeat annually while unresolved.

Ten required content items

Description of the violation/situation, contaminant(s), and levels
When it occurred
Potential health effects (Appendix B language for MCL/MRDL/TT; standard monitoring language otherwise)
Population at risk, including vulnerable subpopulations
Whether alternate water should be used
Actions consumers should take, including when to seek medical help
What the PWS is doing to correct it
When the PWS expects to return to compliance
PWS (or designee) name, business address, and phone
Statement encouraging recipients to distribute the notice, where applicable

Memory Tool — PARCH

P-Problem (what & when)
A-Actions (consumer actions, alternate water)
R-Response by Utility (corrective measures, timeline for compliance)
C-Contact & Circulate (PWS info + share notice w/ others)
H-Health (effects and susceptible populations)

Chief Operator lens

Match the clock to the risk. Tier 1 is an acute threat — hours, by every means that reaches people. Tier 2 is a health-based violation — weeks. Tier 3 is monitoring or administrative — up to a year. Know which one you're in before you draft.
When in doubt, notify faster and consult DDW. A borderline turbidity or acute situation can escalate to Tier 1 if you don't consult in time — the safe error is speed.
Reach the people served, not just the billing addresses. Renters, schools, and businesses drink the water too; use methods that actually reach them, and translate where your community needs it.
Say what happened, what it means, and what to do. The notice exists to let people protect themselves — plain language, health effects, clear actions, not legalese.

Record Keeping Rules

Purpose

Help owners and operators of PWSs serving fewer than 10,000 persons understand what records they are required to keep, what additional records they should keep, how long to retain them, the benefits of record keeping, and how to keep records secure — maintaining a comprehensive history of the system.

General retention requirements

Record	Retain
Actions to correct primary-regulation violations; public notices issued	≥ 3 years
Microbiological & turbidity analyses; variances/exemptions	≥ 5 years
Chemical analyses (residuals, DBPs, nitrate/nitrite, radionuclides, IOC/VOC/SOC); sanitary surveys	≥ 10 years

May keep actual lab results or summaries (see 40 CFR 141.33). Requirements may not apply to systems that purchase water and add no treatment — check with the state.

Rule-specific retention

Rule	Record	Retain
Public Notification	Any public notice issued	≥ 3 yr
Consumer Confidence	CCRs	≥ 3 yr
Lead & Copper	PE records for a lead ALE	≥ 12 yr
Lead & Copper	All Pb/Cu results, WQP, source sampling, CCT studies, PE, state determinations, schedules, evaluations	≥ 12 yr
Stage 1 DBPR	Monitoring plans	≥ 10 yr
Stage 2 DBPR	Subpart V monitoring plans & analytical results	≥ 10 yr
LT1ESWTR	Individual filter monitoring results	≥ 3 yr
LT1ESWTR	Disinfection profiling/benchmarking (raw data & analysis)	Indefinitely

Phase II/V and the SWTR add no rule-specific retention beyond the general table. IESWTR applies to systems > 10,000 and is not covered by this small-system guide.

Why keep records

Support proper operation & maintenance and efficient facility performance.
Educate new staff; help recognize, diagnose, and solve problems.
Resolve customer complaints; document changes in water use, quality, and availability.
Facilitate communication with customers, regulators, and decision-makers; support financial planning and required reports.

Chief Operator lens

Know your longest clocks. Chemical results, sanitary surveys, and lead/copper records have to survive years — build retention around the longest requirement, not the shortest.
Records are how you prove compliance. In an inspection or after a violation, what you can produce is your defense — if it isn't documented, it didn't happen as far as the regulator is concerned.
Make them retrievable and secure. Retention only helps if you can find the record and it hasn't been lost, altered, or destroyed early — back them up and control access.
Keep more than the minimum where it helps you operate. Trends in your own operating data catch problems the required records never will.

National Primary Drinking Water Regulations

Purpose

National Primary Drinking Water Regulations (NPDWRs) are legally enforceable standards that apply to public water systems. They protect public health by limiting the levels of contaminants in drinking water.

Source & currency

Adapted from EPA's National Primary Drinking Water Regulations table (epa.gov, current through Dec 2025) — supersedes the older EPA 816-F-09-004 (May 2009) poster, which predated the PFAS NPDWR. This is an EPA summary, not regulatory text — cite 40 CFR Part 141 for the enforceable federal requirement. For a California system, Title 22 governs and is more stringent in several places — see "California caveats" at the end of this page.

Key definitions

MCLG (Maximum Contaminant Level Goal) — the level below which there is no known or expected health risk; non-enforceable, allows a margin of safety.
MCL (Maximum Contaminant Level) — the highest level allowed; enforceable, set as close to the MCLG as feasible using the best available treatment technology and cost.
MRDLG / MRDL — the same goal/enforceable-limit pairing, applied to disinfectant residuals rather than contaminants.
TT (Treatment Technique) — a required process to reduce a contaminant's level, used where a numeric MCL is not feasible to measure directly.

Regulated contaminants (A–Z)

Units are mg/L unless noted (mg/L ≈ ppm). Health effects are from long-term exposure unless marked short-term. See detailed rule panels (DBPR, Arsenic, Radionuclides, Lead & Copper, TCR/RTCR, SWTR, PFAS) for monitoring & compliance mechanics — this table is the contaminant-by-contaminant limit/goal reference. PFAS are shown separately below (not part of the original 2009 poster).

Contaminant	MCL or TT	Potential health effects (long-term exposure above the MCL)	Common sources in drinking water	MCLG
Acrylamide	TT⁴	Nervous system or blood problems; increased risk of cancer	Added to water during sewage/wastewater treatment	zero
Alachlor	0.002	Eye, liver, kidney, or spleen problems; anemia; increased risk of cancer	Runoff from herbicide used on row crops	zero
Alpha/photon emitters	15 pCi/L	Increased risk of cancer	Erosion of natural deposits of certain radioactive minerals that may emit alpha radiation	zero
Antimony	0.006	Increase in blood cholesterol; decrease in blood sugar	Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder	0.006
Arsenic	0.010	Skin damage or circulatory-system problems; increased risk of cancer	Erosion of natural deposits; runoff from orchards; runoff from glass & electronics production wastes	zero
Asbestos (fibers >10 micrometers)	7 MFL	Increased risk of developing benign intestinal polyps	Decay of asbestos cement in water mains; erosion of natural deposits	7 MFL
Atrazine	0.003	Cardiovascular system or reproductive problems	Runoff from herbicide used on row crops	0.003
Barium	2	Increase in blood pressure	Discharge of drilling wastes; discharge from metal refineries; erosion of natural deposits	2
Benzene	0.005	Anemia; decrease in blood platelets; increased risk of cancer	Discharge from factories; leaching from gas storage tanks and landfills	zero
Benzo(a)pyrene (PAHs)	0.0002	Reproductive difficulties; increased risk of cancer	Leaching from linings of water storage tanks and distribution lines	zero
Beryllium	0.004	Intestinal lesions	Discharge from metal refineries and coal-burning factories; electrical, aerospace & defense industries	0.004
Beta particle & photon emitters	4 mrem/yr	Increased risk of cancer	Decay of natural & man-made radioactive deposits emitting photon/beta radiation	zero
Bromate	0.010	Increased risk of cancer	Byproduct of drinking water disinfection	zero
Cadmium	0.005	Kidney damage	Corrosion of galvanized pipes; erosion of natural deposits; metal refineries; waste batteries & paints	0.005
Carbofuran	0.04	Problems with blood, nervous system, or reproductive system	Leaching of soil fumigant used on rice and alfalfa	0.04
Carbon tetrachloride	0.005	Liver problems; increased risk of cancer	Discharge from chemical plants and other industrial activities	zero
Chloramines (as Cl₂)	MRDL=4.0	Eye/nose irritation; stomach discomfort; anemia	Water additive used to control microbes	MRDLG=4
Chlordane	0.002	Liver or nervous system problems; increased risk of cancer	Residue of banned termiticide	zero
Chlorine (as Cl₂)	MRDL=4.0	Eye/nose irritation; stomach discomfort	Water additive used to control microbes	MRDLG=4
Chlorine dioxide (as ClO₂)	MRDL=0.8	Anemia; infants, young children & fetuses of pregnant women: nervous system effects	Water additive used to control microbes	MRDLG=0.8
Chlorite	1.0	Anemia; infants, young children & fetuses of pregnant women: nervous system effects	Byproduct of drinking water disinfection	0.8
Chlorobenzene	0.1	Liver or kidney problems	Discharge from chemical and agricultural chemical factories	0.1
Chromium (total)	0.1	Allergic dermatitis	Discharge from steel and pulp mills; erosion of natural deposits	0.1
Copper	TT⁵; AL=1.3	Short-term: GI distress. Long-term: liver or kidney damage. Wilson's Disease patients should consult a doctor if levels exceed the action level	Corrosion of household plumbing systems; erosion of natural deposits	1.3
Cryptosporidium	TT⁷	Short-term: gastrointestinal illness (diarrhea, vomiting, cramps)	Human and animal fecal waste	zero
Cyanide (as free cyanide)	0.2	Nerve damage or thyroid problems	Discharge from steel/metal factories; plastic and fertilizer factories	0.2
2,4-D	0.07	Kidney, liver, or adrenal gland problems	Runoff from herbicide used on row crops	0.07
Dalapon	0.2	Minor kidney changes	Runoff from herbicide used on rights of way	0.2
1,2-Dibromo-3-chloropropane (DBCP)	0.0002	Reproductive difficulties; increased risk of cancer	Runoff/leaching from soil fumigant used on soybeans, cotton, pineapples & orchards	zero
o-Dichlorobenzene	0.6	Liver, kidney, or circulatory system problems	Discharge from industrial chemical factories	0.6
p-Dichlorobenzene	0.075	Anemia; liver, kidney, or spleen damage; changes in blood	Discharge from industrial chemical factories	0.075
1,2-Dichloroethane	0.005	Increased risk of cancer	Discharge from industrial chemical factories	zero
1,1-Dichloroethylene	0.007	Liver problems	Discharge from industrial chemical factories	0.007
cis-1,2-Dichloroethylene	0.07	Liver problems	Discharge from industrial chemical factories	0.07
trans-1,2-Dichloroethylene	0.1	Liver problems	Discharge from industrial chemical factories	0.1
Dichloromethane	0.005	Liver problems; increased risk of cancer	Discharge from industrial chemical factories	zero
1,2-Dichloropropane	0.005	Increased risk of cancer	Discharge from industrial chemical factories	zero
Di(2-ethylhexyl) adipate	0.4	Weight loss, liver problems, or possible reproductive difficulties	Discharge from chemical factories	0.4
Di(2-ethylhexyl) phthalate	0.006	Reproductive difficulties; liver problems; increased risk of cancer	Discharge from rubber and chemical factories	zero
Dinoseb	0.007	Reproductive difficulties	Runoff from herbicide used on soybeans and vegetables	0.007
Dioxin (2,3,7,8-TCDD)	0.00000003	Reproductive difficulties; increased risk of cancer	Emissions from waste incineration/combustion; discharge from chemical factories	zero
Diquat	0.02	Cataracts	Runoff from herbicide use	0.02
Endothall	0.1	Stomach and intestinal problems	Runoff from herbicide use	0.1
Endrin	0.002	Liver problems	Residue of banned insecticide	0.002
Epichlorohydrin	TT⁴	Increased cancer risk; stomach problems	Discharge from industrial chemical factories; impurity of some water treatment chemicals	zero
Ethylbenzene	0.7	Liver or kidney problems	Discharge from petroleum refineries	0.7
Ethylene dibromide	0.00005	Problems with liver, stomach, reproductive system, or kidneys; increased risk of cancer	Discharge from petroleum refineries	zero
Fecal coliform & E. coli	MCL⁶	Indicates possible contamination with human/animal wastes; short-term GI symptoms; special risk for infants, young children & immunocompromised	Human and animal fecal waste	zero⁶
Fluoride	4.0	Bone disease (pain & tenderness); children may get mottled teeth	Water additive that promotes strong teeth; erosion of natural deposits; fertilizer & aluminum factories	4.0
Giardia lamblia	TT⁷	Short-term: gastrointestinal illness (diarrhea, vomiting, cramps)	Human and animal fecal waste	zero
Glyphosate	0.7	Kidney problems; reproductive difficulties	Runoff from herbicide use	0.7
Haloacetic acids (HAA5)	0.060	Increased risk of cancer	Byproduct of drinking water disinfection	n/a⁹
Heptachlor	0.0004	Liver damage; increased risk of cancer	Residue of banned termiticide	zero
Heptachlor epoxide	0.0002	Liver damage; increased risk of cancer	Breakdown of heptachlor	zero
Heterotrophic plate count (HPC)	TT⁷	No health effects — an analytic method measuring bacterial variety; lower counts indicate better system maintenance	Naturally-occurring bacteria measured across the environment	n/a
Hexachlorobenzene	0.001	Liver or kidney problems; reproductive difficulties; increased risk of cancer	Discharge from metal refineries and agricultural chemical factories	zero
Hexachlorocyclopentadiene	0.05	Kidney or stomach problems	Discharge from chemical factories	0.05
Lead	TT⁵; AL=0.015	Infants/children: developmental delays, attention & learning deficits. Adults: kidney problems, high blood pressure	Corrosion of household plumbing systems; erosion of natural deposits	zero
Legionella	TT⁷	Legionnaire's Disease, a type of pneumonia	Found naturally in water; multiplies in heating systems	zero
Lindane	0.0002	Liver or kidney problems	Runoff/leaching from insecticide used on cattle, lumber & gardens	0.0002
Mercury (inorganic)	0.002	Kidney damage	Erosion of natural deposits; refineries & factories; runoff from landfills & croplands	0.002
Methoxychlor	0.04	Reproductive difficulties	Runoff/leaching from insecticide used on fruits, vegetables, alfalfa & livestock	0.04
Nitrate (as Nitrogen)	10	Infants <6 months: serious illness, possibly fatal (blue-baby syndrome, shortness of breath) if untreated	Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits	10
Nitrite (as Nitrogen)	1	Infants <6 months: serious illness, possibly fatal (blue-baby syndrome, shortness of breath) if untreated	Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits	1
Oxamyl (Vydate)	0.2	Slight nervous system effects	Runoff/leaching from insecticide used on apples, potatoes & tomatoes	0.2
Pentachlorophenol	0.001	Liver or kidney problems; increased cancer risk	Discharge from wood-preserving factories	zero
Picloram	0.5	Liver problems	Herbicide runoff	0.5
Polychlorinated biphenyls (PCBs)	0.0005	Skin changes; thymus gland problems; immune deficiencies; reproductive/nervous system difficulties; increased risk of cancer	Runoff from landfills; discharge of waste chemicals	zero
Radium 226 & 228 (combined)	5 pCi/L	Increased risk of cancer	Erosion of natural deposits	zero
Selenium	0.05	Hair or fingernail loss; numbness in fingers or toes; circulatory problems	Discharge from petroleum & metal refineries; erosion of natural deposits; mines	0.05
Simazine	0.004	Problems with blood	Herbicide runoff	0.004
Styrene	0.1	Liver, kidney, or circulatory system problems	Discharge from rubber & plastic factories; leaching from landfills	0.1
Tetrachloroethylene	0.005	Liver problems; increased risk of cancer	Discharge from factories and dry cleaners	zero
Thallium	0.002	Hair loss; changes in blood; kidney, intestine, or liver problems	Leaching from ore-processing sites; electronics, glass & drug factories	0.0005
Toluene	1	Nervous system, kidney, or liver problems	Discharge from petroleum factories	1
Total Coliforms	5.0 percent⁸	Indicator that other, potentially harmful bacteria may be present (see Fecal coliform & E. coli)	Naturally present in the environment	zero
Total Trihalomethanes (TTHMs)	0.080	Liver, kidney, or central nervous system problems; increased risk of cancer	Byproduct of drinking water disinfection	n/a⁹
Toxaphene	0.003	Kidney, liver, or thyroid problems; increased risk of cancer	Runoff/leaching from insecticide used on cotton & cattle	zero
2,4,5-TP (Silvex)	0.05	Liver problems	Residue of banned herbicide	0.05
1,2,4-Trichlorobenzene	0.07	Changes in adrenal glands	Discharge from textile finishing factories	0.07
1,1,1-Trichloroethane	0.2	Liver, nervous system, or circulatory problems	Discharge from metal degreasing sites and other factories	0.2
1,1,2-Trichloroethane	0.005	Liver, kidney, or immune system problems	Discharge from industrial chemical factories	0.003
Trichloroethylene	0.005	Liver problems; increased risk of cancer	Discharge from metal degreasing sites and other factories	zero
Turbidity	TT⁷	Indicates cloudiness/filtration effectiveness; higher turbidity often correlates with higher levels of disease-causing organisms (viruses, parasites, some bacteria)	Soil runoff	n/a
Uranium	30 µg/L	Increased risk of cancer, kidney toxicity	Erosion of natural deposits	zero
Vinyl chloride	0.002	Increased risk of cancer	Leaching from PVC pipes; discharge from plastic factories	zero
Viruses (enteric)	TT⁷	Short-term: gastrointestinal illness (diarrhea, vomiting, cramps)	Human and animal fecal waste	zero
Xylenes (total)	10	Nervous system damage	Discharge from petroleum factories; discharge from chemical factories	10

Selected PFAS (2024 NPDWR)

New since the 2009 poster — finalized in EPA's April 2024 PFAS NPDWR. Full Hazard Index mechanics, California NL/RL levels, and the monitoring/compliance timeline are on the PFAS page; the current values are repeated here for a single contaminant-by-contaminant reference.

Contaminant	MCL (ppt)	HBWC¹⁰ (ppt, Hazard Index)	Potential health effects	Sources in drinking water	MCLG (ppt)
Hazard Index PFAS (HFPO-DA, PFBS, PFHxS, PFNA)	1 (unitless)	n/a	Mixture of ≥2 of these PFAS may produce liver, immune, thyroid, and developmental effects even when no single PFAS individually exceeds a level of concern	Manufacturing/industrial chemical facilities; consumer products; occupational exposures; firefighting activities	1 (unitless)
HFPO-DA (GenX)	10	10	Immune, liver, kidney effects; potential cancer concern; developmental effects from exposure during pregnancy/childhood	Manufacturing/industrial chemical facilities; consumer products; occupational exposures; firefighting activities	10
PFHxS	10	10	Immune, thyroid, liver effects; developmental effects from exposure during pregnancy/childhood	Manufacturing/industrial chemical facilities; consumer products; occupational exposures; firefighting activities	10
PFNA	10	10	Elevated cholesterol; immune and liver effects; developmental effects from exposure during pregnancy/childhood	Manufacturing/industrial chemical facilities; consumer products; occupational exposures; firefighting activities	10
PFBS	No individual MCL	2,000	See Hazard Index PFAS row	See Hazard Index PFAS row	No individual MCLG
PFOA	4.0	n/a	Cardiovascular, immune, liver effects; increased incidence of kidney and testicular cancers; developmental/immune effects from exposure during pregnancy/childhood	Manufacturing/industrial chemical facilities; consumer products; occupational exposures; firefighting activities	zero
PFOS	4.0	n/a	Cardiovascular, immune, liver effects; increased incidence of liver cancer; developmental/immune effects from exposure during pregnancy/childhood	Manufacturing/industrial chemical facilities; consumer products; occupational exposures; firefighting activities	zero

Units are ng/L (parts per trillion, ppt) except the Hazard Index, which is unitless — matches the PFAS page.

National Secondary Drinking Water Regulations

Non-enforceable federal guidelines for contaminants causing cosmetic (skin/tooth discoloration) or aesthetic (taste, odor, color) effects. EPA recommends but does not require compliance — some states, including California, adopt secondary MCLs as enforceable standards (Title 22 §64449).

Contaminant	Secondary MCL
Aluminum	0.05 – 0.2 mg/L
Chloride	250 mg/L
Color	15 (color units)
Copper	1.0 mg/L
Corrosivity	Noncorrosive
Fluoride	2.0 mg/L
Foaming Agents	0.5 mg/L
Iron	0.3 mg/L
Manganese	0.05 mg/L
Odor	3 threshold odor number
pH	6.5 – 8.5
Silver	0.10 mg/L
Sulfate	250 mg/L
Total Dissolved Solids	500 mg/L
Zinc	5 mg/L

Selected notes (adapted from EPA's current NPDWR table; supersedes the 2009 EPA 816-F-09-004 poster numbering):

4 — Acrylamide/epichlorohydrin: certify annually that dose × monomer level does not exceed specified products (acrylamide 0.05% dosed at 1 mg/L or equivalent; epichlorohydrin 0.01% dosed at 20 mg/L or equivalent).

5 — Lead & copper are regulated by a Treatment Technique requiring control of water corrosiveness; if >10% of tap samples exceed the action level (Cu 1.3 mg/L, Pb 0.015 mg/L), additional steps are required. See the Lead and Copper Rule panel for full mechanics.

6 — A fecal-coliform/E. coli-positive routine sample triggers repeat sampling; an acute MCL violation occurs if any repeat is TC-positive (or, for TC-positive/fecal-negative routines, if any repeat is fecal/EC-positive).

7 — Surface water treatment requires disinfection and filtration (or filtration-avoidance criteria) to control Cryptosporidium (99% removal, filtered systems), Giardia lamblia (99.9% / 3-log removal/inactivation), viruses (99.99% / 4-log removal/inactivation), turbidity (≤1 NTU max / ≤0.3 NTU in ≥95% of samples/month for conventional/direct filtration), and HPC (≤500/mL). See the Surface Water Treatment Rules panel.

8 — No more than 5.0% of samples total-coliform-positive in a month (systems collecting <40 samples/month: no more than 1 TC-positive sample).

9 — No collective MCLG for HAA5/TTHM as a group, but individual MCLGs exist: dichloroacetic acid (zero), trichloroacetic acid (0.02 mg/L), bromodichloromethane (zero), bromoform (zero), dibromochloromethane (0.06 mg/L), chloroform (0.07 mg/L), monochloroacetic acid (0.07 mg/L). Bromoacetic acid and dibromoacetic acid are also regulated in the HAA5 group but have no MCLGs.

10 — Health-Based Water Concentration (HBWC): the level below which adverse health effects are not likely to occur, used in the PFAS Hazard Index calculation.

California caveats (Title 22 governs a CA system)

This page is the federal NPDWR summary. For a California system, Title 22 governs and is more stringent in several places relevant to the exam:

Hexavalent chromium (Cr6): no separate federal MCL (federal chromium above is total chromium at 0.1 mg/L) — California has its own Cr6 MCL of 0.010 mg/L. See the Upcoming Regulations page.
Manganese: federally only a secondary standard (0.05 mg/L, above) — not a federal primary MCL. See the Manganese page for California's status.
Lead action level: both federal and California currently enforce 0.015 mg/L; the federal LCRI value of 0.010 mg/L begins November 1, 2027. See the Lead and Copper Rule page.
PFAS: California has its own Notification/Response Levels and MCL rulemaking that may differ from the federal MCLs above — do not assume the federal numbers are the CA compliance numbers. See the PFAS page.
Uranium: federal MCL is 30 µg/L (above); California's operative MCL is 20 pCi/L (by radioactivity, not mass) — see the Radionuclides Rule page.

For the enforceable legal text, cite 40 CFR Part 141 (federal) or Title 22 (California) — not this summary.

Sample Exam Questions

How to use this tab

One prompt at a time. Work the answer out loud, then reveal the things to talk about to check your coverage. There is no right/wrong scoring here — this is a rehearsal tool, not a quiz.

Loading…

Prompt 0 of 0

Shortcuts: Space/Enter = reveal · ← / → = prev/next

Flash Cards

Total cards

Reviewed

Correct

Incorrect

Accuracy

—

0 of 0 reviewed

Deck

Loading…

Card 0 of 0

Shortcuts: Space/Enter = reveal · ← / → = prev/next · 1 = right · 2 = wrong

Scripts

What these are

Audio-style study scripts that walk through the exam rules by topic in plain, spoken language. Each one is written to be read aloud and recorded, so you can listen back on repeat — on a commute, at the gym, wherever — and let the rules and numbers sink in through repetition. They are grouped the way the exam groups its questions.

How to use them

Read each script out loud and record yourself with any voice-recording tool.
Listen to your own recording on repeat. Hearing the material in your own voice is a strong memory aid.
Each script runs about 15 to 20 minutes, sized to fit a typical commute.
Recording it in your own voice works best. If you would rather not, you can download a computer-read audio version below and listen to that instead.

Home

About

Wastewater Exam Prep

Water Exam Prep

T1–T4 Exam Prep

Surface Water & Reservoirs

Wells & Groundwater

Watershed Protection

Raw Water & Clearwell Storage

Coagulation, Flocculation & Sedimentation

Filtration

Disinfection

Corrosion Control

Taste & Odor

Iron & Manganese Removal

Fluoridation

Best Available Technology (BAT)

Chemical Feeders

Pumps, Motors & Gearboxes

Blowers & Compressors

Water Meters

Pressure Gauges

Instrumentation

Electrical Generators

Sampling

General Lab Practices

Disinfectant Analysis

Alkalinity Analysis

pH Analysis

Turbidity Analysis

Specific Conductance

Hardness

Fluoride Analysis

Color Analysis

Taste & Odor Analysis

Microbiological Analysis

Safety

Regulations & Administrative Duties

How these work

The Pounds Formula

Chemical Feed Rate

Percent Removal

Area

Volume

Detention Time

Mean Cell Residence Time (MCRT)

Sludge Volume Index (SVI)

Chlorine Dose, Demand & Residual

Food to Microorganism Ratio (F:M)

Biochemical Oxygen Demand (BOD)

Wastewater Math Videos

CA SWRCB T5 Exam Dashboard

About the T5 Exam

How it's organized

How to use it

Source material

Safe Drinking Water Act

What the Act Does

Who enforces it in California

How it affects your treatment plant

Stage 1 & Stage 2 DBP Rules

Regulated contaminants

Regulated disinfectants

Running Annual Average (RAA) & Locational Running Annual Average (LRAA)

Operational Evaluation Level (OEL)

Enhanced coagulation — required TOC removal (%)

Controlling TTHM & HAA5 — treatment techniques

Comprehensive Surface Water Treatment Rule

Turbidity Requirements

IFE FOLLOW-UP TRIGGERS — California systems serving ≥10,000

Return to Service — Post backwash or service interruption

Routine Operation — two consecutive 15-minute readings

FILTER BACKWASH RECYCLING REQUIREMENTS

Covered recycle flows

Recycle information to keep on file

LT2 — Cryptosporidium bin classification

Microbial Toolbox

Cryptosporidium Action Plan

Disinfection & residual monitoring

Disinfection profiling & benchmarking